WO2024117896A1

WO2024117896A1 - Integrated zero liquid discharge process for treating palm oil mill effluent

Info

Publication number: WO2024117896A1
Application number: PCT/MY2023/050071
Authority: WO
Inventors: Nik Mohd Farid MAT YASIN; Yosri MOHD SIRAN; Mohammed Faisal MOHAMMED YUNUS; Ramzan RAZALI; Abu Hanifah NAWI
Original assignee: Sime Darby Plantation Intellectual Property Sdn Bhd
Priority date: 2022-12-01
Filing date: 2023-09-06
Publication date: 2024-06-06

Abstract

The present invention provides an integrated zero liquid discharge process for treating palm oil mill effluent (POME), comprising of cooling of the POME to produce a pre-treated POME, flocculating and coagulating suspended solids contained in the pre-treated POME, dewatering or removing the flocculated and coagulated suspended solids, adding at least one electrolyte to the partially treated POME, delivering the partially treated POME to an electro-oxidation cell, removing precipitate and/or suspended solids from the partially treated POME and passing the treated POME through reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the treated POME to produce a zero liquid discharge, whereby the zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water and a reject water produced from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process.

Description

INTEGRATED ZERO LIQUID DISCHARGE PROCESS FOR TREATING PALM OIL MILL EFFLUENT FIELD OF INVENTION The present invention generally relates to a process for treating palm oil mill effluent (POME). More particularly, the present invention relates to an integrated zero liquid discharge process for treating POME obtained from a palm oil milling process to produce a zero liquid discharge (final treated POME). BACKGROUND The list of prior arts or published information in this specification should not be taken as an acknowledgement that this present invention is common general knowledge or is part of the state of the art. A zero liquid discharge process is a water treatment process to reduce wastewater economically and produce clean water that is suitable for reuse, which saves money and is beneficial to the environment. Processing of oil palm fresh fruit bunches (FFB) in a palm oil mill for the production of palm oil creates a type of polluted wastewater known as palm oil mill effluent (POME). Three major operations of the milling process namely sterilization of the FFB, clarification step and pressing of the empty fruit bunches (EFB) uses large quantities of water, whereby at least 50% of the water results in POME. POME is a source of inland water pollution (due to its high chemical oxygen demand (COD), biochemical oxygen demand (BOD) and its acidic nature) and hence is not allowed to be discharged into bodies of water (i.e. rivers / lakes) without being treated for discharge into the environment according to be in compliance with environmental standards as set by the authorities. Discharging untreated POME into bodies of water depletes dissolved oxygen (oxygen as present in the water) as bacteria breaks down the organic materials in POME in natural systems, which consumes certain amounts of oxygen in the process. If organic material is high, hence, the breakdown process will diminish the levels of oxygen in the water which would be lethal for the aquatic organisms. [Source: Handbook POME-to-Biogas, Project Development in Indonesia] Typically, 5 to 7.5 tonnes of water are required for production of 1 tonne of crude palm oil (CPO), whereby 50% ends up as POME. POME is a viscous, brownish liquid containing about 95% to 96% water, 0.6% to 0.7% oil and 4%-5% total solids. POME is acidic in nature (pH 4 to 5), hot (80- 90 °C), non-toxic (as no chemicals are added during the CPO extraction process in the palm oil mill) and has high COD (50,000 mg/L) and BOD (25,000 mg/L) contents and contains certain amounts of nutrients. [Source: Palm Oil Mill Effluent (POME) Treatment “Microbial Communities in an Anaerobic Digester”: A Review, International Journal of Scientific & Research Publications] POME is without a doubt the largest waste generated from the CPO extraction process. Anaerobic digestion has been used by most of the palm oil mills as the primary treatment of POME and the secondary treatment of POME is generally the assimilation with the blend of both anaerobic and aerobic ponds. Anaerobic digestion is considered as the most suitable POME treatment method as because of its high concentration of organic carbon. Most of the palm oil mills uses open ponding system for POME treatment due to the low costs involved and operational simplicity, which generally consists of four types of ponds namely the fat pit, cooling pond, anaerobic pond and aerobic pond. Although ponding systems are largely used by the industry due to economic perspective, however, it is land and time intensive (i.e. requires long retention times and large treatment areas) and release large amount of methane gas into the atmosphere. Anaerobic digestion is a collection of processes wherein bacteria breakdown organic biomass without the presence of oxygen. Examples of resulting products of anaerobic digestion are methane and carbon dioxide. These biogas products can be used directly for fuel, e.g. in heat and power gas engines, or converted to other forms of renewable energy, e.g. natural gas. The process of anaerobic digestion typically begins with bacterial hydrolysis of the input materials. Insoluble organic polymers, e.g. carbohydrates, are broken down to soluble derivatives that become available for other bacteria. Acidogenic bacteria then convert the soluble derivatives, e.g. sugars and amino acids, into carbon dioxide, hydrogen, ammonia, and short chain fatty acids (also known as “volatile fatty acids” or VFA). Finally, methanogenic bacteria, or methanogens, convert the VFA to methane and carbon dioxide. In some processes, an intermediate step called acetogenesis occurs where the acidogenic bacteria convert VFAs into acetic acid, which the methanogens utilize in the production of methane and carbon dioxide. [Source: United States Application US10233104B2] A publication entitled “A Review on the Development of Palm Oil Mill Effluent (POME) Final Discharge Polishing Treatments” [Source: Journal of Oil Palm Research Vol. 29(4) December 2017] describes that conventional ponding systems generally consist of cooling and mixing, anaerobic, facultative and aerobic ponds. Cooling and mixing ponds serves to stabilise the POME temperature and pH prior to anaerobic digestion. Anaerobic stage produces methane gas that is a value added produce for biogas. Facultative and aerobic ponds are necessary to further reduce the organic content in the wastewater before it is discharged to the rivers. Open ponding system has been proven to successfully reduce the concentration of pollutants such as COD (100-175 mg/L), BOD (100-610 mg/L) and ammoniacal nitrogen (100-200mg/L). This system requires long total hydraulic retention time between 45 to 60 days and large land area. The last few years have seen a major shift towards sustainability from conventional treatments of POME to tertiary treatments using various technologies. Recently the research interest seems to have shifted to the development of sustainable polishing technologies. Previous studies have proven that palm-based bio-adsorbents have great potential to remove residual organic pollutants, heavy metals and colour from POME. Adsorption treatment on POME final discharge of polishing system results in higher pollutant removal compared with the adsorption treatment of POME from the ponding system. The maximum colour and COD reduction of POME final discharge were 98% and 81%, respectively. Raw POME has a BOD value about one hundred times more than that of sewage. If not properly treated, POME could pose as a high organic pollutant. Conventional ponding process has been an effective method to reduce the biological and chemical constituents of POME. This method, even though simple and reliable, generates large amounts of sludge and takes up large land areas. It is thus justifiable that many studies have been conducted to develop alternative methods for POME treatment with possibilities of resource recovery by smaller, higher efficiency treatment system. Membrane technology has high potential of becoming part of POME treatment system as with a high separation capability there is a possibility of developing systems that can recover valuable pharmaceutical components from POME and recovering high quality water by application of membrane technology to POME treatment systems. Initial lab work and the current treatment applications have led to the selection of centrifugation as the membrane pre-treatment method. The aqueous phase from this process shows decrease in the range of between 60% to 80% of COD, turbidity, color, and suspended solids. This will be the fed to the hollow fiber membrane modules. The modules were of 0.2 Âµm, 500K, 100K, and 30K MWCOs. The tested system have an overall removal efficiency of 89.9% for COD, 92.9% for colour, 99.4% for suspended solids and 97.9% for turbidity. [Source: Treatment of Palm Oil Mill Effluent (POME) using Membrane Technology, Regional Symposium on Membrane Science and Technology 2004] Prior Art 1 Zero liquid discharge can be achieved 4 steps which are i) pre-treatment, ii) membrane treatment, iii) evaporator and iv) crystallizer to produce treated wastewater. • Pre-treatment: Prepare wastewater for treatment and brine concentration, as per downstream equipment specs (produces pre-treated wastewater) • Membrane treatment: Primary water treatment (i.e. reverse osmosis (RO) or electrodialysis reversal (EDR)) (produces brine) • Evaporator: Brine concentration and volume reduction (produces concentrated brine) • Crystallizer: produce solids for disposal or reuse (produces solid) [Source: Saltworks Technologies 2018, SaltworksTech.com] Prior Art 2 Zero liquid discharge (ZLD) is an ambitious wastewater management strategy that eliminates any liquid waste leaving the plant or facility boundary, with the majority of water being recovered for reuse. ZLD obviates the risk of pollution associated with wastewater discharge and maximizes water usage efficiency, thereby striking a balance between exploitation of freshwater resources and preservation of aquatic environments. Achieving ZLD, however, is generally characterized by intensive use of energy and high cost. As a result, ZLD has long been considered not viable and has been applied only in limited cases. Early ZLD systems were based on stand-alone thermal processes, where wastewater was typically evaporated in a brine concentrator followed by a brine crystallizer or an evaporation pond. The condensed distillate water in ZLD systems is collected for reuse, while the produced solids are either sent to a landfill or recovered as valuable salt byproducts. Such systems, which have been in successful operation for 40 years and are still being built, require considerable energy and capital. Reverse osmosis (RO), a membrane-based technology widely applied in desalination, has been incorporated into ZLD systems to improve energy and cost efficiencies. However, RO, although much more energy efficient than thermal evaporation, can be applied only to feedwaters with a limited salinity range. Accordingly, other salt- concentrating technologies that can treat higher salinity feedwaters, such as electrodialysis (ED), forward osmosis (FO), and membrane distillation (MD), have emerged recently as alternative ZLD technologies to further concentrate wastewater beyond RO. [Source: The Global Rise of Zero Liquid Discharge for Wastewater Management: Drivers, Technologies, and Future Directions, https://pubs.acs.org/doi/10.1021/acs.est.6b01000#] Prior Art 3 A zero discharge system in the palm oil milling effluent treatment process is one that can treat all the incoming effluent and leave nothing behind. So an integrated biological treatment pilot plant, based on 5m³ POME h−1, was set up as a project collaboration by Malaysian Palm Oil Board (MPOB), Ronser Bio-Tech Sdn Bhd. Malaysia and Shanghai Jiao Tong University at Experimental Palm Oil Mill, Labu, Malaysia. The technology involves an enclosed system covering an area of 2 acres which will convert the greenhouse gas into renewable energy, discharged water treated approximately from BOD 27,000 mg/L to BOD 20 mg/L. The present pilot study relates to establishment of a zero discharge POME treatment technology with three units (1) pre-treatment (recovery of waste oil from POME), (2) biological treatment (to produce biogas from POME and generate final discharge of BOD 20 mg/L or below) and (3) membrane separation (wastewater reuse or recycling). To effectively treat such high strength wastewater, biological treatment (a combined anaerobic and aerobic process) is required, as well as the membrane filtration technology. The two patent treatment technologies developed by our group, i.e. anaerobic AnaEG (A state-of-the-art advanced anaerobic expanded granular sludge bed and the aerobic BioAX (A novel environmental biotechnological aerobic process) world's first high efficiency bio-membrane technology are employed in this pilot study. [Source: An integrated method for palm oil mill effluent (POME) treatment for achieving zero liquid discharge – A pilot study, https://www.sciencedirect.com/science/article/abs/pii/S0959652615001699] Prior Art 4 A zero discharge POME treatment pilot plant was installed at Kilang Kelapa Sawit (KKS) Labu, Sime Darby. This plant was equipped with a complex concrete tank functioning as a pre-treatment and aerobic / clarifier system, followed by a biological treatment system and lastly a series of ultra- filtration (UF) and reverse osmosis (RO) used for reclamation. By taking advantage of the abundant POME generated as a waste, an integrated ‘zero discharge’ treatment process mainly routed in ‘Pre-treatment - Biological Processes – Membrane Separation’ has been developed based on a sustainable development strategy: i. Pre-treatment of POME ii. Biological Treatment – Anaerobic and Aerobic Process iii. Biogas Purification and Utilisation iv. Treated POME / Sludge Recovery as Biofertiliser v. Reclamation System The preliminary data of the proposed integrated approach showed possible attainment of zero discharge of POME for the oil palm industry. However, the economics of this approach needs to be further addressed for commercial uptake. [Source: Zero Discharge Treatment Technology of Palm Oil Mill Effluent, https://www.researchgate.net/publication/260917494_Zero_discharge_treatment_technology_of_ palm_oil_mill_effluent] Prior Art 5 Palm oil is one of the most important agro industries in Malaysia. Huge quantities of palm oil mill effluent (POME) pose a great threat to aqueous environment due to its very high COD. To make full use of discharged wastes, the integrated “zero discharge” pilot-scale industrial plant comprising “pre-treatment-anaerobic and aerobic process-membrane separation” was continuously operated for 1 year. After pre-treatment in the oil separator tank, 55.6% of waste oil in raw POME could be recovered and sold and anaerobically digested through 2 AnaEG reactors followed by a dissolved air flotation (DAF); average COD reduced to about 3587 mg/L, and biogas production was 27.65 times POME injection which was used to generate electricity. The aerobic effluent was settled for 3 h or/and treated in MBR which could remove BOD3 (30°C) to less than 20 mg/L as required by Department of Environment of Malaysia. After filtration by UF and RO membrane, all organic compounds and most of the salts were removed; RO permeate could be reused as the boiler feed water. RO concentrate combined with anaerobic surplus sludge could be used as biofertilizer. Five main unit processes were included in the system, namely, pretreatment unit, biological treatment unit, reclamation unit, biogas utilisation, and sludge treatment unit. All tanks were made of concrete except for 2 anaerobic expanded granular sludge bed (EGSB) bioreactors made of steel with coating. [Source: Zero Discharge Performance of an Industrial Pilot-Scale Plant Treating Palm Oil Mill Effluent, Volume 2015 | Article ID 617861 | https://doi.org/10.1155/2015/617861] Prior Art 6 PCT Publication WO2013169091A1 relates to the establishment of a zero discharge treatment technology of POME mainly routed in (1) pre-treatment, (2) biological treatment and (3) membrane separation. The ultimate goals of the developed zero discharge POME treatment technology are: (1) produce biogas as a source of renewable energy, (2) zero emissions of POME into the atmosphere, (3) final discharge of BOD 20 ppm or below; (4) clean water for use as boiler feed water and (5) recover potash rich fertilizer, which are of great values to the palm oil milling process. A zero discharge treatment technology in handling a palm oil milling waste; comprises the following steps (i) pre-treatment, (ii) biological treatment and (iii) membrane separation. Said palm oil milling waste used is POME. Following features will be demonstrated in a zero discharge POME treatment plant: • Zero discharge of POME; • Biogas production and utilization as a form of renewable energy; • Final discharge of POME BOD 20 ppm or below; • Recovering sludge/dewatered sludge as biofertilizer with high K content; and • Recycling of the treated water for boiler use. Prior Art 7 PCT Publication WO2015/037980 describes a zero liquid discharge palm oil clarification process for extracting palm oil from a feed liquor consisting of a mixture of palm oil, free water, bound water, suspended solids, dissolved solids and gums originating from prior processing steps in the palm oil extraction process, comprising the steps of: removing free water in the feed liquor by an evaporation means to form evaporated liquor and process condensate containing the evaporated water as by-product, using the palm oil in the feed liquor as a fluidizing medium to facilitate evaporation, to an extent sufficient to convert the effluent discharged from the clarification process from a liquid form to a solid form and to break oil/water emulsions in the feed liquor and precipitate the gums; and removing the gums and suspended solids in the evaporated liquor by a decanting centrifuge means using the suspended solids as a carrier for conveying the gums out of the decanting centrifuge means. Prior Art 8 PCT Publication WO2016/129986 describes a method for treating effluent produced from palm oil milling process, comprising the steps of removing solid from the effluent, wherein the removed solid are formed into dried products, removing water from the effluent for reusing the water in the palm oil milling process, extracting oil from the effluent to form a residual sludge, wherein the steps of removing solids, removing water, and extracting oil are carried out in sequential order of solid, water and oil. It is also an objective of the present invention to provide a method for eliminating the effluent discharge from the palm oil milling process by treating the POME and recovering the solid, water, and oil phase of the POME. It is further an objective of the present invention to provide a method for extracting the crude palm oil from the POME. It is yet another objective of the present invention to provide a method which is economically viable for achieving zero discharge from the palm oil milling process, thereby reducing or eliminating the release of methane gas from conventional effluent treatment ponds. It is also an objective of the present invention to provide a method of treating the POME which can be incorporated into the existing palm oil extraction process without changing the process thereof. The present invention relates to a method for treating effluent produced from palm oil milling process, comprising recovering solid, water, and crude palm oil from the effluent to produce a residual sludge, wherein the recovering of solid, water and crude palm oil is carried out in sequential order in the sequence of solid first, water next and finally crude palm oil, and each of the recovered solid, water, crude palm oil, and the final residual sludge are recycled or formed into usable products. Prior Art 9 PCT Publication WO2020/141967 provides a method for producing a solid biomass suitable for use as a biofertilizer or as a biofuel from liquid effluent discharged from the palm oil milling process comprising the steps of (a) evaporating the liquid effluent to reduce its moisture content to produce a concentrated sludge and a condensate containing evaporated components as by-product, (b) mixing the concentrated sludge with one or more bulking materials to produce a mixed biomass, (c) drying the mixed biomass to reduce its moisture content to an extent sufficient to produce the solid biomass. The liquid effluent in the present invention may be either untreated (raw) or partially treated POME. If partially treated POME, it may be either the liquor from anaerobic digestion of POME or the liquor from aerobic digestion of POME. The liquid effluent may be pre-treated prior to evaporation to minimize fouling of the evaporation means, producing a clarified sludge for evaporating and sludge solids. The separation of the suspended solids is advantageously carried out using a mechanical separation means, such as decanting centrifuge, a belt press, a filter press or a multi-disk screw press, or combination thereof. The liquid effluent may be chemically dosed to assist in the flocculation of solids to improve the separation of solids by the mechanical separation means. The clarified sludge discharged from the mechanical separation means will consist mainly of water, dissolved solids and fine fibrous suspended solids. The present invention finds ready industrial applicability in the palm oil industry as it is a method for converting the liquid effluent discharged from palm oil mills from a product having very little economic value and requiring substantial investment for its treatment to comply with regulations on discharge standards to a product that can be used either as a biofuel or as a biofertilizer. The invention provides a simple method for addressing the problems faced with the use of evaporation and drying systems to achieve zero discharge of liquid effluent from palm oil mills. Prior Art 10 US Patent Application US20180179097A1 describes about a method comprising generating a first water product and a sludge of contaminants from water to be treated using an advanced electronic- oxidation process, wherein the advanced electronic-oxidation process comprises an electronic treatment comprising a combination of electrocoagulation, electro-flocculation, electro-chlorinator, and electro-dialysis operated in synchronization with ozone, separating the sludge of contaminants from the first water product using a filtration process, filtering the first water product to produce a second water product and a concentrated water by-product, wherein the filtering comprises a first sub-stage to remove particles greater than 0.02 μm to about 0.05 μm followed by a second sub- stage comprising a reverse osmosis process or a nano-filtration process; and exposing the second water product to an ultraviolet light treatment or ozonation process to generate clean water. Prior Art 11 European Patent EP3825389 provides an efficient and economic method and system for producing crude palm oil by which recovery of by-products and efficient resource utilization can be obtained. Furthermore, it is an objective to provide a method and system for treating POME, which can assist palm oil mills to realize zero effluent discharge. Additionally, it is an objective to provide a method and system which enable reduction of operating costs in palm oil mills. The objectives above are attained according to a first aspect of the present invention, which relates to a method for producing crude palm oil from a palm-oil containing raw material comprising fresh fruit bunches (FFB), the method comprising receiving and feeding the palm-oil containing raw material to a sterilizer, sterilizing the raw material in the sterilizer by means of steam, threshing the raw material in a thresher, digesting fruits in a digester and pressing the fruits in a press to extract crude palm oil, clarifying the extracted crude palm oil in a clarifying tank and drying the extracted crude palm oil in a drier. During the production a palm oil mill effluent (POME) is generated as a residual sludge. The method further comprises (a) Separating water and solids from at least part of the palm oil mill effluent (POME) by using a POME separator, (b) Feeding at least part of the separated water to a steam generator, (c) Generating steam in the steam generator using the separated water and (d) Feeding the generated steam to the sterilizer. According to the present method, the sterilizer may use the steam generated from the water available in the POME. By using the steam generator, a way to recycle the separated water from the POME within the mill has been found, and hence the problem of discharge of separated water from POME outside the palm oil mill is minimized or eliminated. Thus, zero liquid discharge can be achieved, since the separated water is kept in a closed loop within the palm oil mill. Additionally, by using the steam generated from the POME, it is possible to replace a motive steam supplied by a boiler of a palm oil mill using fresh water in sterilizing the raw material, FFB. Thereby, fresh water consumption may be reduced. The method may further comprise a step (e) of processing the solids from the POME separator to produce oil- containing by-products or to recover a part of the oil present in the solids. In this way the environmental load can be further decreased. Prior Art 12 PCT Publication WO2021/101366 describes a process for treating palm oil mill effluent (POME), the process including the steps of: a) cooling the POME (1) in a cooling pond from a temperature range of between 60°C to 90°C to a temperature range of between 20° C to 60°C to produce cooled POME; b) or flocculating and coagulating suspended solids using at least one polymer and coagulants (2) as contained in the cooled POME to produce flocculated suspended solids or flocculated and coagulated suspended solids in the cooled POME; c) dewatering the flocculated suspended solids (3) as contained in the cooled POME to remove the flocculated suspended solids in the cooled POME using a belt press, filter belt, screw disc, multi disc screw, a decanter or any combinations thereof to produce a dewatered POME; d) clarifying the dewatered POME (4) to remove sludge from the dewatered POME; e) removing the coagulated suspended solids (5) from the dewatered POME using a gravity settlement means, a filtration means or a combination of both to produce a partially treated POME; f) mixing the partially treated POME with at least one electrolyte (6) to produce ionised partially treated POME; g) delivering the ionised partially treated POME to an electro-oxidation cell (7) comprising at least one electrode which is positively charged (anode), at least one electrode which is negatively charged (cathode) to produce a treated POME or an active oxidizing agent; and h) removing precipitate and/or suspended solids from the treated POME (8) using a filtration means such as a bag filtration, a membrane filtration or a combination of both to produce a fully treated POME. Prior Art 13 PCT Publication WO2011/087202 relates to a non-discharge treatment apparatus of palm oil mill effluent, and a treatment method thereof, and more specifically, to a non-discharge treatment apparatus of palm oil mill effluent which treats BOD, COD, SS, T-N, T-P and chromaticity of palm oil mill effluent pre-treated through a three-phase separation decanter through a series of processes comprising anaerobic/aerobic tanks filled with a microorganism fluidized bed carrier, a submerged separation membrane, electro-oxidation, and a reverse osmosis membrane and can simultaneously recycle separated and collected oil, sludge and final treated water, and a method for treating palm oil mill effluent by using the same. The non-discharge treatment apparatus of palm oil mill effluent according to the present invention can stably treat effluent without chemical treatment, can maintain microorganisms by a high concentration compared with a common biological method so as to reduce the retention time of palm oil mill effluent, supplements the problems of known processes such as the deterioration of precipitation according to the change in microorganism state and the like so as to simplify maintenance and to lower maintenance costs, and can reuse separated and collected oil, sludge and final treated water. SUMMARY OF THE INVENTION The present invention generally relates to an integrated zero liquid discharge process for treating palm oil mill effluent (POME) produced from a palm oil milling process, comprising of cooling of the POME to produce a pre-treated POME, flocculating and coagulating suspended solids contained in the pre-treated POME to produce flocculated and coagulated suspended solids, dewatering or removing the flocculated and coagulated suspended solids to produce a partially treated POME, adding at least one electrolyte to the partially treated POME, delivering the partially treated POME to an electro-oxidation cell which includes an at least one electrode plate and the at least one electrolyte, removing precipitate and/or suspended solids from the partially treated POME to produce a treated POME and passing the treated POME through reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the treated POME to produce a zero liquid discharge, whereby the zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process and a reject water produced from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates the process flow of a POME treatment using anaerobic, aerobic and extended aeration which is able to produce final treated POME with BOD of 20 mg/L but the colour is dark and brownish with high TDS value which does not allow for the treated POME to be recycled back to be used in the palm oil milling process as boiler feed water and for other means. Figure 2 illustrates the process flow of the use of a reverse osmosis process after the extended aeration process per to allow for water recycling. Figure 3 illustrates the process flow which uses electro-oxidation process to treat POME, which is however not suitable to be used for boiler feed water due to its high TDS. Figure 4 illustrates the process flow of the process of the present invention. Figure 5 shows a graph with respect to the percentage of salt rejection over time (for a reverse osmosis process). Figure 6 shows a graph on the comparison between a permeate and reject stream of a reverse osmosis process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION The present invention generally relates to a process for treating palm oil mill effluent (POME). More particularly, the present invention relates to an integrated zero liquid discharge process for treating POME obtained from a palm oil milling process to produce a zero liquid discharge (final treated POME). It can be appreciated that the parameters for the present invention are not obvious for a person skilled in the art and have been tested and determined by the inventors based on numerous trials conducted, observations, discussions and combined expertise, which would not be able to be determined without much efforts and analysis. All prior arts as listed and referred to above do not specifically describe the process of this present invention. A total of 451 palm oil mills was in operation in Malaysia in 2021 with a combined annual processing capacity of 115.87 million tonnes of fresh fruit bunches (FFB). [Source: Oil Palm Economic Performance in Malaysia and R&D Progress in 2021, Journal of Oil Palm Research Vol. 34 (2) June 2022] POME consists of large amount of biodegradable organic matter that requires a series of biological treatment via anaerobic, aerobic and facultative processes in order to degrade the organic matter of POME before being discharged into bodies of water, such as rivers, lakes and/or ponds. These biological processes depend greatly on consortium of microorganisms to degrade the organic matters to produce by-products such as methane, carbon dioxide and water. Processing of oil palm fresh fruit bunches (FFB) in a palm oil mill for the production of palm oil creates a type of polluted wastewater known as palm oil mill effluent (POME). Three major operations of the milling process namely sterilization of the FFB, clarification step and pressing of the empty fruit bunches (EFB) uses large quantities of water, whereby at least 50% of the water results in POME. POME is a source of inland water pollution (due to its high chemical oxygen demand (COD), biochemical oxygen demand (BOD) and its acidic nature) and hence is not allowed to be discharged into bodies of water (i.e. rivers / lakes) without being treated for discharge into the environment according to be in compliance with environmental standards as set by the authorities. Hence, the objectives of the present invention are as follows: A first object of the present invention is to produce a zero liquid discharge (a final treatment POME) which is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process. A second object of the present invention is to provide a zero discharge process which utilises a combination of process comprising an electro-oxidation process, reverse-osmoses process and an ion exchange process in order to produce a zero liquid discharge (a final treated POME). A third object of the present invention is to provide an integrated zero discharge process whereby the reject water from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process. This would directly transform to utilisation of water from bodies of water such as rivers be reduced by 50% when boiler feed water grade discharge effluent is produced by the process of this present invention. A fourth object of the present invention is to provide a novel combination of an integrated zero discharge process which includes cooling of the POME in a cooling pond, anaerobic treatment of the POME, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge (a final treated POME). A fifth object of the present invention is to provide a novel combination of an integrated zero discharge process which includes cooling of the POME in a cooling pond, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge (a final treated effluent). A sixth object of the present invention is to provide a novel combination of an integrated zero discharge process which includes cooling of the POME in a cooling pond, POME is treated anaerobically and aerobically, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge. A seventh object of the present invention is to provide a novel combination of an integrated zero discharge process which includes cooling of the POME in a cooling pond, POME is treated anaerobically, aerobically and polished in a polishing plant, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge (a final treated POME). An eighth object of the present invention is to provide a zero discharge process whereby the electro-oxidation process is a single-stage electro-oxidation process or a two-stage electro- oxidation process. The single-stage electro-oxidation process further includes adjusting pH of the partially treated POME. The two-stage electro-oxidation process further includes adding an additional at least one second electrolyte to the partially treated POME, removing precipitate and/or suspended solids from the partially treated POME, treating the partially treated POME via a further electro-oxidation process and adjusting pH of the partially treated POME. A ninth object of the present invention is to provide an electro-oxidation process which consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with no contactor in between the anode and cathode plates with a retention time of between 90 minutes to 600 minutes. A tenth object of the present invention is to provide an electro-oxidation process which consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with a contactor in between the anode and cathode plates with a retention time of between 60 minutes to 300 minutes. While the present invention is described herein by way of example using illustrative drawings and embodiments, it should be understood that the detailed description are not intended to limit the invention to embodiments of drawing or drawings described and are not intended to limit the invention to the particular form disclosed but in contrary the invention is to cover all modifications, equivalents and alternatives falling within the scope of the present invention. Terminology and phraseology used herein is solely used for descriptive purposes and is not intended as limiting in scope. The words such as “including”, “comprising”, “having”, “containing” or “involving” and other variations is intended to be broad and cover the subject matter as described including equivalents and additional subject matter not recited such as other components or steps. Definitions: “Zero liquid discharge” for this present invention means a final treated POME which is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process. “Boiler feed water” for this present invention means water that is used to generate steam in the boiler room of a palm oil mill with the following criteria: • Turbidity < 5 FAU (Formazine attenuation unit); • Chloride < 50 ppm; • pH 6.5 to 8.0; • Total Iron < 0.30 ppm; and • TDS < 100 ppm. “ADMI” means American Dye Manufacturers’ Institute is a colour index developed to monitor colours of wastewater effluent as an indicator for water quality. “Electro-oxidation process” for this present invention refers to a technique used for wastewater treatment with a general layout of an electro-oxidation cell consisting of two electrodes (anode and cathode) and with presence of an electrolyte and power source. The anode and cathode plates as mentioned above can be used with or without a contactor in between the plates. The contactor used can be from materials such as activated carbon, zeolites, ion exchange resin or any preferred material which can enable / allow transfer of surface charges (electrons) of the POME. Both ways (with or without a contactor) works efficiently for the present invention. Usage of a contactor would depend on type of effluent / content of POME and preference / cost of the user of the present invention. Having a contactor between the anode and cathode plates provides an additional benefit as less reaction time is required (when a contactor is used) for the same surface area of the plate, hence, resulting in lower capital expenditure. The electro-oxidation process used for this present invention has remarkable ability in treating the pollutants as further described below: ▪ Effectively transforms non-biodegradable pollutants into non-toxic biodegradable substances by rapidly oxidizing a wide range of organic pollutants through generation of highly reactive groups of hydroxyl radical, (OH ˉ); ▪ Has efficiency in further reducing of the toxicity level in the POME that they can improve the biodegradability of organic compounds through the use of reactive radical; and ▪ Remarkable ability of the reactive radical to react in a flash with the organic compounds that lead to the production of organic radicals whereby these radical in nature are reactive to the presence of oxygen. The contactor used can be from materials such as activated carbon, zeolites, ion exchange resin or any preferred material which can enable transfer of surface charges (electrons) of the POME. The surface area to volume ratio of the at least one electrode which is positively charged (anode) is in a range of between 0.001 m²/L to 1 m²/L, preferably in a range of between 0.001 m²/L to 0.5 m²/L and most preferably in a range of between 0.001 m²/L to 0.2 m²/L. “Surface area” means the area of the at least one electrode where the direct oxidation takes place. The bigger the surface area, reaction will be faster to work on the organic matters of the POME, hence, less retention time in the electro-oxidation cell and vice-versa. The selection would depend on preference and costing / expenditure / budget of an individual mill. The distance between the at least one electrode which is positively charged (anode) and the at least one electrode which is negatively charged (cathode) is in a range of between 0.5 cm to 20 cm, preferably in a range of between 0.5 cm to 10 cm and most preferably in a range of between 0.5 cm to 5 cm. The distance between the electrodes in the electro-oxidation cell will determine the resistance in the cell, which would affect the voltage and power required for the electro- oxidation cell and process. The smaller the distance between the electrodes, the lower the resistance, voltage and power of the cell which results in lower operating cost, however, in order to obtain a smaller distance between the electrode plates, more plates are required to be installed which would see a rise in capital expenditure. The proposed ranges above are determined based on the inventors’ expertise and experience in this field, conduct of trials, observations and calculations by the inventors in balancing the operating cost and capital expenditure and what would be most optimum to be used for the present invention. “Reverse osmosis process” for this present invention utilises semi / partially permeable membrane which allows separation of molecules / ions / larger particles from the treated effluent. Reverse osmosis works by applying pressure to force the water molecules to move from a concentrated solution to a dilute solution by overcoming an osmotic pressure. A series of reverse osmosis membrane is used to achieve the desired purity of a treated effluent or to increase water recovery from the present invention. A series of reverse osmosis process on the permeate (i.e. the feed that has passed through the reverse osmosis membrane) is used to further enhance purity of the water and on the reject water to further improve water recovery. Reverse osmosis systems can be easily purchased by third party vendors depending on the preference of the user of the present invention. “Ion exchange process” for this present invention involves changes of ion at the insoluble solids. The process consists of cationic ion exchangers which exchanges positive ions and anionic ion exchangers which exchange negative ions. There are also combination of both anionic and cationic ion exchanges in a mixed bed column. Ion-exchange systems can also be easily purchased by third party vendors depending on the preference of the user of the present invention. “Biochemical oxygen demand (BOD)” for this present invention refers to amount of oxygen that bacteria will consume while decomposing the organic matters in POME under aerobic conditions. “Chemical oxygen demand (COD)” for this present invention refers to the total quantity of oxygen required to oxidize all organic materials in POME into carbon dioxide and water. In general a COD value is greater than a BOD value. “Aerobic process” or “aerobic digestion” or “aerobic treatment” refers to the degradation of organic materials in POME in the presence of oxygen. This process utilises aerators to provide oxygen during the process, hence, requires high energy. “Anaerobic digestion” or “anaerobic process” or “anaerobic treatment” refers to the degradation of organic materials by anaerobic bacteria in POME in the absence of oxygen. Examples of resulting products of anaerobic digestion are methane and carbon dioxide. The process generally begins with bacterial hydrolysis to break down insoluble organic polymers into soluble derivatives and then acidogenic bacteria proceeds to convert soluble derivatives into carbon dioxide, hydrogen, ammonia and volatile fatty acids. Methanogenic bacteria will then proceed to convert the volatile fatty acids to methane and carbon dioxide. “Cooling pond” for the purposes of this present invention means a man-made body of water for cooling the POME discharged from the palm oil milling process to a range preferably between 20°C to 60°C. This range temperature is preferable as mesophilic bacteria are mainly used in the anaerobic ponding systems, whereby, these bacteria are most active in moderate temperatures ranging between 20°C to 60°C. “Ammoniacal Nitrogen (AN) value” for this present invention refers to the measure of amount of ammonia (which is a toxic pollutant) in POME. “Suspended solids” for the purposes of this present invention means the measure of the dissolved content of both inorganic and organic materials in POME in suspended form, preferably to be below 200 ppm in the final treated POME. “Dewatering” for this present invention means to remove the flocculated suspended solids from anaerobically treated POME via plate filter press, belt press, filter belt, screw disc, multi disc screw, a decanter or any combination thereof, preferably using filter belt or screw disc. Normal anaerobic conditions applies for the dewatering process, however, there is no retention time for dewatering process as it is a continuous process. “Filtration” for this present invention means to remove precipitate such as ferum oxide, nickel oxide and zinc oxide from the treated POME via bag filtration means, membrane filtration means or any combination thereof with pore size in the range of between 1 micron to 100 microns, preferably 1 micron to 50 microns and most preferably 1 micron to 10 microns. “Polymer” for this present invention means a type of compound used in the flocculation process to enhance the flocculation process. Polymers can be natural or synthetic compounds and are available in various forms including solutions, powders or beads, oil or water-based emulsions. Any forms may be used for this present invention depending on preference, availability and cost as determined by the user of the present invention. Types of polymer that can be used for this present invention are polyacrylamide, polypropylene, polyamines, polytannin or any combination thereof, preferably polyacrylamide. Polyacrylamide is preferred for this present invention as based on trials done by the inventors for this present invention and also other related projects conducted by the inventors pertaining to wastewater treatment, polyacrylamide is found to work best and provides good and acceptable results with respect to the flocculation process. “Coagulation” is a process to form viscous or gelatinous mass to bridge particles together to form mass large enough to be trapped in a filter. Finely dispersed solids suspended in the wastewaters are stabilised by negative electric charges on their surfaces which prevents them from colliding to form larger masses (i.e. coagulate), hence, coagulation process is required. Chemicals (known as flocculants) are used to encourage the particles already formed to form larger masses / particles which can be filtered away more easily from the wastewaters. Coagulants that can be used for the present invention are iron based coagulants, aluminium based coagulants or any combination thereof, such as ferum chloride, ferric chloride, ferrous sulphate, poly aluminium chloride (PAC) and aluminium sulphate. “pH adjustments” can be done using chemicals such as sodium hydroxide, hydrochloric acid, sulphuric acid, sodium chloride and others. pH values affect the surface charges (electrons) and forms coagulants and allows impurities to be removed, hence, controlling the level of pH which would significantly improve the coagulation process. Therefore, the coagulation step can be improved to achieve its maximum efficiency not just by optimising the dosage of coagulants but also by adjusting and optimising the pH value to maximise the removal of impurities from the wastewater. The pH adjustments can be done without a coagulation step or with a coagulation step (before and/or after the coagulation step). pH adjustment also can lead to precipitation of contaminants which can be removed via filtration means. “Flocculation” is a process to form a bigger coagulate i.e. floc by using polymer. Polymer having high molecular weight and branching structure will trap the coagulate thus forming bigger particulate. Slow mixing (< 50 rpm) is preferred for the flocculation process as opposed to the coagulation process. Slow mixing is crucial to ensure that flocculation happens effectively / all solids are flocculated properly. “Retention time” for this present invention means the reaction time of the following: ▪ Retention time for electro-oxidation process (without use of a contactor between the anode and cathode plates) is between 90 minutes to 600 minutes. ▪ Retention time for electro-oxidation process (with use of a contactor between the anode and cathode plates) is between 60 minutes to 300 minutes. ▪ Retention time to produce the treated POME after an electro-oxidation process is in a range of between 60 minutes to 300 minutes. ▪ Retention time produce the zero liquid discharge (final treated POME) after an electro-oxidation process, reverse-osmosis process and an ion exchange process is in a range of between 15 minutes to 60 minutes. The Present Invention A zero liquid discharge for this present invention means a final treated POME which is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process. The present invention provides an integrated zero liquid discharge process for treating palm oil mill effluent (POME) produced from a palm oil milling process, comprising of: a) cooling of the POME to produce a pre-treated POME; b) flocculating and coagulating suspended solids contained in the pre-treated POME to produce flocculated and coagulated suspended solids; c) dewatering or removing the flocculated and coagulated suspended solids to produce a partially treated POME; d) adding at least one first electrolyte to the partially treated POME; e) delivering the partially treated POME to an electro-oxidation cell which includes an at least one electrode plate and the at least one first electrolyte; f) removing precipitate and/or suspended solids from the partially treated POME to produce a treated POME; and g) passing the treated POME through reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the treated POME to produce a zero liquid discharge, whereby the zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process; and a reject water produced from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process. Step a) happens in a cooling pond from a temperature range of between 60°C to 90°to a temperature range of between 20°C to 60°C. The pre-treated POME of step a) is treated anaerobically in an anaerobic pond, anaerobic digester, biogas facility or any combination thereof. The pre-treated POME of step a) is not treated anaerobically. The pre-treated POME of step a) is firstly treated anaerobically in an anaerobic pond, anaerobic digester, biogas facility or any combination thereof and is secondly treated aerobically treated in an aerobic pond, a mix of aerobic pond and polishing plant, a polishing plant with extended aeration or any combination thereof. The pre-treated POME of step a) is not treated anaerobically and aerobically. The pre-treated POME of step a) is firstly treated anaerobically in an anaerobic pond, anaerobic digester, biogas facility or any combination thereof, is secondly treated aerobically in an aerobic pond or a mix of aerobic ponds and is thirdly polished in a polishing plant, a polishing plant with extended aeration or any combination thereof. The pre-treated POME of step a) is not anaerobically treated, aerobically treated and polished. The at least one polymer in any form such as solution, powder, oil or water-based emulsions or any combination thereof and at least one inorganic, organic, tannin-based coagulants or any combination thereof are used for step b). Step c) is carried out using a plate filter press, belt press, filter belt, screw disc, multi disc screw, a decanter or any combination thereof. The at least one first electrolyte of step d) is an as sodium chloride, sodium sulphate, hydrochloric acid, sulphuric acid or any combination thereof. The quantity of the at least one first electrolyte to the partially treated POME is in a range of between 100 mg/L (ppm) to 10,000 mg/L (ppm). The partially treated POME of step e) is treated via a first electro-oxidation process. The first electro-oxidation process is a single-stage electro-oxidation process or a two-stage electro-oxidation process. The single-stage electro-oxidation process further includes adjusting pH of the partially treated POME. The two-stage electro-oxidation process further includes adding at least one second electrolyte to the partially treated POME, removing precipitate and/or suspended solids from the partially treated POME, treating the partially treated POME via a second electro-oxidation process and adjusting pH of the partially treated POME. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with no contactor in between the anode and cathode plates. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with a contactor in between the anode and cathode plates. The electro-oxidation cell of step e) contains an electrical current in a range of between 5 amperes to 10,000 amperes for 1,000 L of the partially treated POME. Adjusting pH of the partially treated POME is carried out using sodium hydroxide, hydrochloric acid, sulphuric acid or any combination thereof. The precipitate and/or suspended solids of step f) are removed via clarification, induced air flotation system, filtration, solid liquid separation, sand filter, activated carbon filter or any combination thereof. Retention time for electro-oxidation process is between 90 minutes to 600 minutes. Retention time for electro-oxidation process is between 60 minutes to 300 minutes. Retention time to produce the treated POME of step f) is in a range of between 60 minutes to 300 minutes. Retention time produce the zero liquid discharge of step g) is in a range of between 15 minutes to 60 minutes. Process Option 1: The present invention provides an integrated zero liquid discharge process for treating palm oil mill effluent (POME) produced from a palm oil milling process, comprising of: a) cooling of the POME to produce a pre-treated POME; b) flocculating and coagulating suspended solids contained in the pre-treated POME to produce flocculated and coagulated suspended solids; c) dewatering or removing the flocculated and coagulated suspended solids to produce a partially treated POME; d) adding at least one first electrolyte to the partially treated POME; e) delivering the partially treated POME to an electro-oxidation cell which includes an at least one electrode plate and the at least one first electrolyte; f) removing precipitate and/or suspended solids from the partially treated POME to produce a treated POME; and g) passing the treated POME through reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the treated POME to produce a zero liquid discharge, whereby the zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process; and a reject water as produced from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process. Step a) happens in a cooling pond from a temperature range of between 60°C to 90°to a temperature range of between 20°C to 60°C. The pre-treated POME of step a) is treated anaerobically in an anaerobic pond, anaerobic digester, biogas facility or any combination thereof. An at least one polymer in any form such as solution, powder, oil or water-based emulsions or any combination thereof and at least one inorganic, organic, tannin-based coagulants or any combination thereof are used or added for step b). Step c) is carried out using a plate filter press, belt press, filter belt, screw disc, multi disc screw, a decanter or any combination thereof. The at least one electrolyte of step d) is an as sodium chloride, sodium sulphate, hydrochloric acid, sulphuric acid or any combination thereof. Quantity of the at least one first electrolyte to the partially treated POME is in a range of between 100 mg/L (ppm) to 10,000 mg/L (ppm). The partially treated POME of step e) is treated via a first electro-oxidation process. The first electro-oxidation process is a single-stage electro-oxidation process or a two-stage electro-oxidation process. The single-stage electro-oxidation process further includes adjusting pH of the partially treated POME. The two-stage electro-oxidation process further includes adding at least one second electrolyte to the partially treated POME, removing precipitate and/or suspended solids from the partially treated POME, treating the partially treated POME via a second electro-oxidation process and adjusting pH of the partially treated POME. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) without a contactor in between the anode and cathode plates. The retention time for electro-oxidation process (without use of a contactor) is between 90 minutes to 600 minutes. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with a contactor in between the anode and cathode plates. The retention time for electro-oxidation process (with use of a contactor) is between 60 minutes to 300 minutes. The electro-oxidation cell of step e) contains an electrical current in a range of between 5 amperes to 10,000 amperes for 1,000 L of the partially treated POME. Adjusting pH of the partially treated POME is carried out using sodium hydroxide, hydrochloric acid, sulphuric acid or any combination thereof. The precipitate and/or suspended solids of step f) are removed via clarification, induced air flotation system, filtration, solid liquid separation, sand filter, activated carbon filter or any combination thereof. Retention time to produce the treated POME of step f) is in a range of between 60 minutes to 300 minutes. Retention time produce the zero liquid discharge of step g) is in a range of between 15 minutes to 60 minutes. Process Option 2: The present invention provides an integrated zero liquid discharge process for treating palm oil mill effluent (POME) produced from a palm oil milling process, comprising of: a) cooling of the POME to produce a pre-treated POME; b) flocculating and coagulating suspended solids contained in the pre-treated POME to produce flocculated and coagulated suspended solids; c) dewatering or removing the flocculated and coagulated suspended solids to produce a partially treated POME; d) adding at least one first electrolyte to the partially treated POME; e) delivering the partially treated POME to an electro-oxidation cell which includes an at least one electrode plate and the at least one first electrolyte; f) removing precipitate and/or suspended solids from the partially treated POME to produce a treated POME; and g) passing the treated POME through reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the treated POME to produce a zero liquid discharge, whereby the zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process; and a reject water produced from the reverse-osmosis process of is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process. Step a) happens in a cooling pond from a temperature range of between 60°C to 90°to a temperature range of between 20°C to 60°C. An at least one polymer in any form such as solution, powder, oil or water-based emulsions or any combination thereof and at least one inorganic, organic, tannin-based coagulants or any combination thereof are used for step b). Step c) is carried out using a plate filter press, belt press, filter belt, screw disc, multi disc screw, a decanter or any combination thereof. The at least one electrolyte of step d) is an as sodium chloride, sodium sulphate, hydrochloric acid, sulphuric acid or any combination thereof. Quantity of the at least one electrolyte to the partially treated POME is in a range of between 100 mg/L (ppm) to 10,000 mg/L (ppm). The partially treated POME of step e) is treated via a first electro-oxidation process. The first electro-oxidation process is a single-stage electro-oxidation process or a two-stage electro-oxidation process. The single-stage electro-oxidation process further includes adjusting pH of the partially treated POME. The two-stage electro-oxidation process further includes adding at least one second electrolyte to the partially treated POME, removing precipitate and/or suspended solids from the partially treated POME, treating the partially treated POME via a second electro-oxidation process and adjusting pH of the partially treated POME. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) without a contactor in between the anode and cathode plates. The retention time for electro-oxidation process (without use of a contactor) is between 90 minutes to 600 minutes. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with a contactor in between the anode and cathode plates. The retention time for electro-oxidation process (with use of a contactor) is between 60 minutes to 300 minutes. The electro-oxidation cell of step e) contains an electrical current in a range of between 5 amperes to 10,000 amperes for 1,000 L of the partially treated POME. Adjusting pH of the partially treated POME is carried out using sodium hydroxide, hydrochloric acid, sulphuric acid or any combination thereof. The precipitate and/or suspended solids of step f) are removed via clarification, induced air flotation system, filtration, solid liquid separation, sand filter, activated carbon filter or any combination thereof. Retention time to produce the treated POME of step f) is in a range of between 60 minutes to 300 minutes. Retention time produce the zero liquid discharge of step g) is in a range of between 15 minutes to 60 minutes. Process Option 3: The present invention provides an integrated zero liquid discharge process for treating palm oil mill effluent (POME) produced from a palm oil milling process, comprising of: a) cooling of the POME to produce a pre-treated POME; b) flocculating and coagulating suspended solids contained in the pre-treated POME to produce flocculated and coagulated suspended solids; c) dewatering or removing the flocculated and coagulated suspended solids to produce a partially treated POME; d) adding at least one first electrolyte to the partially treated POME; e) delivering the partially treated POME to an electro-oxidation cell which includes an at least one electrode plate and the at least one first electrolyte; f) removing precipitate and/or suspended solids from the partially treated POME to produce a treated POME; and g) passing the treated POME through reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the treated POME to produce a zero liquid discharge, whereby the zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process; and a reject water as produced from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process. Step a) happens in a cooling pond from a temperature range of between 60°C to 90°to a temperature range of between 20°C to 60°C. The pre-treated POME of step a) is treated anaerobically in an anaerobic pond, anaerobic digester, biogas facility or any combination thereof and treated aerobically treated in an aerobic pond, a mix of aerobic pond and polishing plant, a polishing plant with extended aeration or any combination thereof. An at least one polymer in any form such as solution, powder, oil or water-based emulsions or any combination thereof and at least one inorganic, organic, tannin-based coagulants or any combination thereof are used for step b). Step c) is carried out using a plate filter press, belt press, filter belt, screw disc, multi disc screw, a decanter or any combination thereof. The at least one first electrolyte of step d) is an as sodium chloride, sodium sulphate, hydrochloric acid, sulphuric acid or any combination thereof. Quantity of the at least one first electrolyte to the partially treated POME is in a range of between 100 mg/L (ppm) to 10,000 mg/L (ppm). The partially treated POME of step e) is treated via a first electro-oxidation process. The first electro-oxidation process is a single-stage electro-oxidation process or a two-stage electro-oxidation process. The single-stage electro-oxidation process further includes adjusting pH of the partially treated POME. The two-stage electro-oxidation process further includes adding at least one second electrolyte to the partially treated POME, removing precipitate and/or suspended solids from the partially treated POME, treating the partially treated POME via a second electro-oxidation process and adjusting pH of the partially treated POME. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) without a contactor in between the anode and cathode plates. The retention time for electro-oxidation process (without use of a contactor) is between 90 minutes to 600 minutes. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with a contactor in between the anode and cathode plates. The retention time for electro-oxidation process (with use of a contactor) is between 60 minutes to 300 minutes. The electro-oxidation cell of step e) contains an electrical current in a range of between 5 amperes to 10,000 amperes for 1,000 L of the partially treated POME. Adjusting pH of the partially treated POME is carried out using sodium hydroxide, hydrochloric acid, sulphuric acid or any combination thereof. The precipitate and/or suspended solids of step f) are removed via clarification, induced air flotation system, filtration, solid liquid separation, sand filter, activated carbon filter or any combination thereof. Retention time to produce the treated POME of step f) is in a range of between 60 minutes to 300 minutes. Retention time produce the zero liquid discharge of step g) is in a range of between 15 minutes to 60 minutes. Process Option 4: The present invention provides an integrated zero liquid discharge process for treating palm oil mill effluent (POME) produced from a palm oil milling process, comprising of: a) cooling of the POME to produce a pre-treated POME; b) flocculating and coagulating suspended solids contained in the pre-treated POME to produce flocculated and coagulated suspended solids; c) dewatering or removing the flocculated and coagulated suspended solids to produce a partially treated POME; d) adding at least one first electrolyte to the partially treated POME; e) delivering the partially treated POME to an electro-oxidation cell which includes an at least one electrode plate and the at least one first electrolyte; f) removing precipitate and/or suspended solids from the partially treated POME to produce a treated POME; and g) passing the treated POME through reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the treated POME to produce a zero liquid discharge, whereby the zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process; and a reject water as produced from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process. Step a) happens in a cooling pond from a temperature range of between 60°C to 90°to a temperature range of between 20°C to 60°C. The pre-treated POME of step a) is treated anaerobically in an anaerobic pond, anaerobic digester, biogas facility or any combination thereof, treated in an aerobic pond or a mix of aerobic

with extended aeration or

combination thereof. Aerobic treatment produces an

treated POME with a BOD of <100 mg/L (ppm) and

solids of <400 mg/L. A

a partially treated POME with BOD of <20 mg/L (ppm) and

solids < 200 mg/L. At least one polymer in any form such as solution, powder, oil or water-based emulsions or any combination thereof and at least one inorganic, organic, tannin-based coagulants or any combination thereof are used for step b). Step c) is carried out using a plate filter press, belt press, filter belt, screw disc, multi disc screw, a decanter or any combination thereof. The at least one first electrolyte of step d) is an as sodium chloride, sodium sulphate, hydrochloric acid, sulphuric acid or any combination thereof. The quantity of the at least one first electrolyte to the partially treated POME is in a range of between 100 mg/L (ppm) to 10,000 mg/L (ppm). The partially treated POME of step e) is treated via a first electro-oxidation process. The first electro-oxidation process is a single-stage electro-oxidation process or a two-stage electro-oxidation process. The single-stage electro-oxidation process further includes adjusting pH of the partially treated POME. The two-stage electro-oxidation process further includes adding at least one second electrolyte to the partially treated POME, removing precipitate and/or suspended solids from the partially treated POME, treating the partially treated POME via a second electro-oxidation process and adjusting pH of the partially treated POME. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) without a contactor in between the anode and cathode plates. The retention time for electro-oxidation process (without use of a contactor) is between 90 minutes to 600 minutes. The electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with a contactor in between the anode and cathode plates. The retention time for electro-oxidation process (with se of a contactor) is between 60 minutes to 300 minutes. The electro-oxidation cell of step e) contains an electrical current in a range of between 5 amperes to 10,000 amperes for 1,000 L of the partially treated POME. Adjusting pH of the partially treated POME is carried out using sodium hydroxide, hydrochloric acid, sulphuric acid or any combination thereof. The precipitate and/or suspended solids of step f) are removed via clarification, induced air flotation system, filtration, solid liquid separation, sand filter, activated carbon filter or any combination thereof. Retention time to produce the treated POME of step f) is in a range of between 60 minutes to 300 minutes. Retention time produce the zero liquid discharge of step g) is in a range of between 15 minutes to 60 minutes. Referring to Figures 1 to 4, the present invention is further described as follows: This present invention focuses on a combination of processes (integrated) using electro-oxidation, reverse-osmosis and ion exchange to produce zero liquid discharge. The present invention provides a zero liquid discharge to reduce wastewater economically and produce clean (treated) water that is suitable for reuse which saves money and is beneficial to the environment, able to fulfil regulatory requirements, reduction in water footprint by at least 50% and produces 100% recycling of treated effluent for use as boiler feed water and dilution of undiluted crude palm oil (UDCO) in the milling process. Integration of the electro-oxidation process with reverse osmosis and ion exchange processes has enabled achievement of a zero liquid discharge. Use of reverse osmosis and ion-exchange process reduces the TDS to <100 mg/L, therefore allowing the final treated POME to be used as boiler feed water in the palm oil milling process. The reject water from the reverse-osmosis process can be used for washing and as a dilution water for UDCO dilution in the milling process. In the conventional means, the reject water from a reverse osmosis process is returned back to the ponding system hence there is very minimal reduction in the water footprint as opposed to the present invention. Conventionally, POME is treated using a series of physical and biological treatment (i.e. cooling process / anaerobic process / aerobic process / extended aeration process etc.) to produce treated discharge which is able to meet the stipulated discharge quality limit (BOD 20ppm). The treated effluent is then disposed by either land irrigation (treated effluent is discharged to the estate via furrow system as means of irrigation means) or watercourse discharge (treated effluent is discharged to nearest water bodies) depending on requirements as set by local department of environment. Conventional processes requires high hydraulic retention time which results in use of big land area and also the final treated POME achieved using these processes is still brownish in colour and cannot be recycled back to the mill for boiler feed purposes. Conventional means mainly focuses on reducing BOD without any emphasis on COD and colour of the final treated effluent, therefore, does not allow the production of a zero liquid discharge. Referring to Figure 1, POME treatment using anaerobic, aerobic and extended aeration is able to produce final treated POME with BOD of 20 mg/L but the colour is dark and brownish with high TDS value which does not allow for the treated POME to be recycled back to be used in the palm oil milling process as boiler feed water and for other means. There have also been use of reverse osmosis process after the extended aeration process per Figure 2 to allow for water recycling. However, it is not optimum and has several issues to be addressed such as: ▪ the reject water from the reverse-osmosis process is a concentrated dark and brownish coloured liquid which is not suitable to be utilised as dilution water for UDCO dilution; ▪ reduction in water footprint is also not optimum which is below 35%; and ▪ reverse-osmosis process on its own is not sustainable due to fouling and high organic load contained in the treated effluent. There are also prior arts on the use of electro-oxidation which has enable the removal of colours from treated POME and able to achieve Standard A of the Malaysian Industrial Effluent Regulation (i.e. BOD <20 mg/L, COD <80mg/L and colour <100 ADMI). The treated POME here can be used for UDCO dilution per Figure 3, however not suitable to be used for boiler feed water due to its high TDS. For this case, only 18% water is used for UDCO dilution whereas the treated water is 70% with respect to FFB processed at the mill which makes it an approximate of 52% left of water to be recycled. The inventors of the present invention have surprising found that integrating of the electro-oxidation process with reverse-osmosis process and ion-exchange process per Figure 4 has proven to be an effective, efficient and optimum process to achieve zero liquid discharge with high water footprint reduction at 56%. The present invention produced a final treated POME that is colourless and reject water from the reverse osmosis process is colourless which can be recycled back for UDCO dilution. The inventors have further investigated the impact on the crude palm oil (CPO) quality with the use of the recycled water for UDCO dilution, comparison was made using the reject water from the reverse osmosis process vs. normal water. The investigation showed comparable CPO quality using both types of water. The use of a reverse osmosis process requires multiple passing through of the reverse osmosis membrane in order to reduce the levels of TDS to <300 mg/L. A discharge will enter buffer tank prior to being pumped by high-pressure pumps to the reverse osmosis membrane / module. The pressure will push the water to the permeate stream while retaining the contaminant in the reject stream. Permeate stream will undergo another reverse osmosis process prior to being treated using ion exchange system. The permeate stream will need to undergo several reverse osmosis processes until TDS level is reduced to <300mg/L before being treated with the ion exchange process. Number of reverse-osmosis processes refers to number of passes through the reverse osmosis membrane. [Source: https://www.sciencedirect.com/topics/engineering/reverse-osmosis-membrane] The reverse osmosis process is to ensure that the TDS level is <300 mg/L before proceeding to the ion exchange process. Reverse osmosis here requires the passing of the wastewater through the reverse osmosis membrane multiple times until the discharge effluent TDS is reduced to below 300 mg/L. The ion exchange process will further reduce the TDS level to <100 mg/L. The ion exchange process uses cationic, anionic, and mixed bed to further absorb remaining contaminants from the reverse-osmosis permeate stream. The TDS level is in a range of 2,000 mg/L to 10,000 mg/L after going through the electro-oxidation process and reduces to <300 mg/L after several passes through the reverse-osmosis process and further <100 mg/L upon going through the ion-exchange process. Therefore, the present invention can be used to produce the final treated effluent which is colourless, has a biochemical oxygen demand (BOD) value in a range of between 0 mg/L to 20 mg/L, preferably in the range of between 0 mg/L to 10 mg/L, most preferably in a range of between 0 mg/L to 5 mg/L and an ammoniacal nitrogen (AN) value in a range of between 0 mg/L to 20 mg/L, preferably in the range of between 0 mg/L to 10 mg/L Process Option 1 - The present invention provides a novel combination of zero discharge process which includes cooling of the POME in a cooling pond, anaerobic treatment of the POME, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge. Process Option 2-The present invention also provides a novel combination of zero discharge process which includes cooling of the POME in a cooling pond, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge. Process Option 3-The present invention further provides a novel combination of zero discharge process which includes cooling of the POME in a cooling pond, POME is treated anaerobically and aerobically flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge. Process Option 4-The present invention also provides a novel combination of zero discharge process which includes cooling of the POME in a cooling pond, POME is treated anaerobically,

in a polishing plant, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse- osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge. The most preferred route by the inventors of the present invention is Process Option 1 as this process eliminates the need for an anaerobic pond, aerobic pond and polishing plant to achieve the zero liquid discharge of the present invention. The next preferred route is Process Option 1 as this option is relatively simple and the electro- oxidation, reverse osmosis and ion exchange processes will replace the aerobic ponds and polishing plants, hence those are no longer required. Next preferred routes are Process Option 3, followed by Process Option 4. The user of the present invention can choose whichever option is preferred based on requirements, preference and cost, for example: • if an user of the present invention has existing biogas plant and polishing plant, the best route would be Process Option 4 as this will result in the lowest capital expenditure (CAPEX) and operational expenditure (OPEX); • if an user of the present invention would like to move away from land application via anaerobic pond intake / treatment then the best route would be Process Option 1; or • if an user of the present invention is planning to install a new effluent treatment plant for a new mill, the best route for this would be Process Option 2. Prior Art analysis All prior arts as listed and referred to above do not specifically describe the process of the present invention. Apart from that, it is also not obvious by just reading the prior art documents or information as listed above for experts in the field of interest to just derive or arrive at the process of the present invention without any effort as the parameters have been determined by the inventors based on numerous trials conducted, observations, discussions with combined expertise and experience in this field, which parameters and/or combination could not be determined without much efforts, testing and/or analysis or by just reviewing prior art documents in this field of interest. Prior arts as listed in the ‘Background’ section above:

All prior arts as listed and referred to above do not specifically describe the integrated process of the present invention with the following novel combinations of zero discharge process: i. cooling of the POME in a cooling pond, anaerobic treatment of the POME, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge (no aerobic treatment required here). ii. cooling of the POME in a cooling pond, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge (no anaerobic or aerobic treatments required here). iii. cooling of the POME in a cooling pond, POME is treated anaerobically and aerobically, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge. iv. cooling of the POME in a cooling pond, POME is treated anaerobically, aerobically and polished in a polishing plant, flocculating and coagulating suspended solids and dewatering or removing the flocculated and coagulated suspended solids from the POME, an electro-oxidation process, removing precipitate and/or suspended solids from the POME, reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the POME to produce a zero liquid discharge. Prior Arts 12 and 13 are the closest prior art with respect to the present invention. However, the four combinations of the present invention (Process Option 1 to Process Option 4) as described above does not disclose Prior Arts 12 and 13. Hence, the inventors believe that this present invention is novel. All prior arts as listed and referred to above also do not specifically describe the present invention with the following objectives: • to produce a zero liquid discharge which is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process; • to provide a zero discharge process which utilises a combination of an electro-oxidation process, reverse-osmosis process and an ion exchange process in order to produce a zero liquid discharge; and • to provide a zero discharge process whereby the reject water from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process. There, there remains a need in the art to provide alternatives with respect to POME treatment, in order to achieve a zero liquid discharge in the palm oil mills and whereby the reject water from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil (UDCO) in the palm oil milling process. The inventors have unexpectedly found that the present invention is able to achieve zero liquid discharge in the palm oil mills and also to provide a means where the reject water from the reverse- osmosis process is recycled and reused for washing and dilution of UDCO in the palm oil milling process. This is not mentioned or addressed in any of the prior arts mentioned above. This is obtained by numerous trials and analysis by the inventors of the present invention which cannot be derived randomly by a subject matter expert in this field of interest.

invention

that electro-oxidation

can be used to treat POME without any aerobic and anaerobic treatments which is not

discovered. The inventors of the present invention conducted many trials to optimise and improve upon conventional means to arrive at the process of the present invention. Many years of experience and knowledge in the oil palm milling area have allowed the inventors to achieve the said process of the present invention whereby the reject water from the reverse-osmosis process is recycled and reused for washing and dilution of UDCO in the palm oil milling process instead of being recycled back to the ponding system. Hence, the inventors believe that this present invention is novel and inventive. Land area is reduced by at least 60% with the use of the process of the present invention. In an conventional process, the area covered by anaerobic pond and aerobic pond area are balanced in a ratio of 40:60. For a scenario when electro-oxidation system is applied to replace aerobic ponds, there is a reduction of 60% of area being used for POME treatment. The retention time for an electro-oxidation process is 1 day (maximum) which means there is a reduction of number of days from 100 to 41 (i.e.60%). Electro-oxidation process is also capable to replace both anaerobic and aerobic processes whereby, the hydraulic retention time (HRT) would be 1 day as compared to 100 days via conventional POME treatment means and this would mean a reduction in land area by 100%. EXAMPLES Example 1 This example will focus on Process Option 2 The present invention provides an integrated zero liquid discharge process for treating palm oil mill effluent (POME) produced from a palm oil milling process, comprising of cooling of the POME to produce a pre-treated POME, flocculating and coagulating suspended solids contained in the pre- treated POME to produce flocculated and coagulated suspended solids, dewatering or removing the flocculated and coagulated suspended solids to produce a partially treated POME, adding an at least one first electrolyte to the partially treated POME, delivering the partially treated POME to an electro-oxidation cell which includes an at least one electrode plate and the at least one first electrolyte, removing precipitate and/or suspended solids from the partially treated POME to produce a treated POME and passing the treated POME through a reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the treated POME to produce a zero liquid discharge, whereby the zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process and a reject water produced from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process. Methodology: 1. POME from cooling pond was collected and added with a dose of polymer whereby polyacrylamide (PAM) 0.4% solution was dosed at rate of 1 litre PAM 0.4% / m³ POME. 2. The flocculated solution was filtered using a filter press. 3. The filtered solution was the dosed with sulfuric acid, H₂SO₄ 30% solution to bring the pH level down to 2. 4. The pH adjusted filtered solution was fed to an electro-oxidation cell with the following configuration: a. Plate gap of 4cm; and b. Current density at 100A/m^2. 5. The treated effluent was pH adjusted to 7 using Sodium Hydroxide (NaOH). 6. The pH adjusted treated effluent was filtered using sand filter and activated carbon to produce final treated effluent. Quality was measured. Results / Findings:

Table 1 Table 1 shows that the process of the present invention is able to produce a treated discharge of Standard A of the Malaysian Industrial Effluent Regulation. Evaluation of Reverse Osmosis Methodology: 1. Discharge / effluent from the electro-oxidation pilot plant was collected (3,000 litres) in the feed tank and sent to the reverse osmosis system. 2. Total dissolved solid (TDS) for the feed was measured. 3. Effluent was pumped to the reverse osmosis system at the flow rate of 1,000L/hr. System was controlled by proportioning the permeate and reject stream as per below: • permeate flow rate between 400L/hr to 500L/hr; • TDS and flow rate for permeate and reject stream were measured and recorded; and • the system was stopped when the permeate dropped below 350L/hr. Results / Findings: w 26 86 65 37 27 13 53 18 18 71 27 38 16 49 50 46 07 69 46 28 46 75

Table 2 Table 2 shows that the reverse osmosis process is able to reduce average incoming TDS from 2,696 mg/L to 111 mg/L. Further, Figure 5 shows that the average salt rejection is at 95.86%. The performance of a reverse osmosis system is measured by the percentage of salt rejection, hence the above Figure 5 confirms that the system is performing efficiently for the purposes of this present invention. Referring to Figure 6, the permeate was maintained at 41.64% or 411.18 L/hr for the duration of 60 minutes to 300 minutes before it started to drop to 30.54% or 312.23L/hr. The system was stopped as reduction in permeate showed that the membrane fouling process has started. Results showed that TDS in the permeate varies from 90mg/L to 160mg/L with average at 110.86 mg/L. This was achieved using a single pass through a reverse osmosis membrane. At higher TDS loading, more membrane passes are required to achieve the same results, however, the water recovery will be reduced. Evaluation of Ion Exchange System Methodology: 1. 100L of discharge from electro-oxidation system was collected as feed for the ion exchange system. 2. TDS of feed was measured and recorded. 3. 4kg of mixed bed resin was used in the ion exchange column. 4. The effluent was pumped to the mixed bed resin at 20L/hr flow rate. 5. TDS of discharge from the column was measured and recorded. Results / Findings:

Table 3 Based on the results in Table 3, ion exchange reduced the TDS from 4,100 mg/L to 0 mg/L. The mixed resin was exhausted at 180 minutes of the operation. The fast exhaustion time was due to the high TDS in feed material. To increase the operation time of ion exchange, it is proposed to: • add cationic and anionic resin as a pre-treatment prior to mixed bed resin; and/or • reduce the load to ion exchange system. Evaluation of the reject water for use as a dilution water for undiluted crude palm oil (UDCO) Methodology: 1. Reject water stream was collected from the reverse osmosis system. 2. UDCO was collected from palm oil mills. Sample were collected directly from the gutter underneath the press prior to the addition of hot water dilution, 3. Reject water and UDCO was mixed at the ratio of 2.5 (UDCO) to 1 (water) at the speed of 50 rpm for 10 minutes. 4. The mixture was then centrifuged to separate the water and UDCO at the speed of 4,000 rpm for a duration of 5 minutes. 5. The collected oil was dried using vacuum rotary drum for a duration of 2 hours. 6. The dried oil was analysed for its quality. 7. Steps 3 to 6 were repeated using normal water (from SYABAS) instead of the reject water from the reverse osmosis process. Results / Findings:

Table 4 Table 2 shows the comparison between normal water from SYABAS and reject water from a reverse osmosis process for dilution of UDCO at the mill. Table 4 clearly shows that there is no significant differences on oil quality using normal water from SYABAS vs. reject water from reverse osmosis process for dilution of UDCO at the oil palm mills.

Summary It can be appreciated that the present invention provides an integrated zero liquid discharge process which utilises a combination of an electro-oxidation process, reverse-osmosis process and an ion exchange process in order to produce a zero liquid discharge. The zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of <20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process. Integration of the electro-oxidation process with reverse osmosis and ion exchange processes has enabled achievement of the zero liquid discharge. Use of reverse-osmosis and ion-exchange processes has reduced the TDS to <100 mg/L, therefore allowing the final treated POME to be used as boiler feed water in the palm oil milling process. The reject water from reverse-osmosis process can be used for washing and as a dilution water for UDCO dilution. The present invention has enable the removal of colours from the treated POME making it colourless and able to achieve Standard A of the Malaysian Industrial Effluent Regulation (i.e. BOD <20 mg/L, COD <80mg/L and colour <100 ADMI). It can be appreciated that conventional means for POME treatment (to-date) is not able to produce a fully treated POME which is colourless. The fully treated POME is usually dark brown in-colour and therefore cannot be recycled to be used back in the milling process and only can be recycled to the mills for washing purposes or discharged to bodies of water. It can further be appreciated that this present invention is able to produce a zero liquid discharge which is 100% recyclable and reusable for washing and dilution of UDCO in the palm oil milling process. This would directly result to utilisation of water from bodies of water such as rivers be reduced by 50% when boiler feed water grade discharge effluent is produced by the process of this present invention. Further, it can be appreciated that the parameters for the present invention are not obvious for a person skilled in the art and have been determined by the inventors based on numerous trials conducted, observations, discussions with combined expertise and experience in this field, which parameters and/or combination could not be determined without much efforts, testing and/or analysis or by just reviewing prior art documents in this field of interest. Hence, the inventors believe that this present invention is novel and inventive. Various modifications to these embodiments as described herein are apparent to those skilled in the art from the description and the accompanying drawings. The description is not intended to be limited to these embodiments as shown with the accompanying drawings but is to provide the broadest scope possible as consistent with the novel and inventive features disclosed. Accordingly, the invention is anticipated to hold on to all other such alternatives, modifications and variations that fall within the scope of the present invention and appended claims.

Claims

CLAIMS 1. An integrated zero liquid discharge process for treating palm oil mill effluent (POME) produced from a palm oil milling process, comprising of: a) cooling of the POME to produce a pre-treated POME; b) flocculating and coagulating suspended solids contained in the pre-treated POME to produce flocculated and coagulated suspended solids; c) dewatering or removing the flocculated and coagulated suspended solids to produce a partially treated POME; d) adding an at least one first electrolyte to the partially treated POME; e) delivering the partially treated POME to an electro-oxidation cell which includes an at least one electrode plate and the at least one first electrolyte; f) removing precipitate and/or suspended solids from the partially treated POME to produce a treated POME; and g) passing the treated POME through a reverse-osmosis process and an ion exchange process to remove contaminants and dissolved ions from the treated POME to produce a zero liquid discharge, whereby the zero liquid discharge is colourless (<100 ADMI), has a biochemical oxygen demand (BOD) of < 20 mg/L, a chemical oxygen demand (COD) of <80 mg/L, an ammoniacal nitrogen (AN) value of less than 20 mg/L, a total dissolved solids (TDS) of <100 mg/L and is 100% recyclable and reusable as a boiler feed water in the palm oil milling process; and a reject water produced from the reverse-osmosis process is recycled and reused for washing and dilution of undiluted crude palm oil in the palm oil milling process.

2. The process of Claim 1, wherein step a) happens in a cooling pond from a temperature range of between 60°C to 90°to a temperature range of between 20°C to 60°C.

3. The process of Claim 1, wherein the pre-treated POME of step a) is treated anaerobically in an anaerobic pond, anaerobic digester, biogas facility or any combination thereof.

4. The process of Claim 1, wherein the pre-treated POME of step a) is not treated anaerobically.

5. The process of Claim 1, wherein the pre-treated POME of step a) is firstly treated anaerobically in an anaerobic pond, anaerobic digester, biogas facility or any combination thereof and is secondly treated aerobically in an aerobic pond, a mix of aerobic pond and polishing plant, a polishing plant with extended aeration or any combination thereof.

6. The process of Claim 1, wherein the pre-treated POME of step a) is not treated anaerobically and aerobically.

7. The process of Claim 1, wherein the pre-treated POME of step a) is firstly treated anaerobically in an anaerobic pond, anaerobic digester, biogas facility or any combination thereof, is secondly treated aerobically in an aerobic pond or a mix of aerobic ponds and is thirdly polished in a polishing plant, a polishing plant with extended aeration or any combination thereof.

8. The process of Claim 1, wherein the pre-treated POME of step a) is not treated anaerobically, aerobically and polished.

9. The process of Claim 1, wherein at least one polymer in any form such as solution, powder, oil, water-based emulsions or any combination thereof and at least one inorganic, organic, tannin- based coagulants or any combination thereof are used for step b).

10. The process of Claim 1, wherein step c) is carried out using a plate filter press, belt press, filter belt, screw disc, multi disc screw, a decanter or any combination thereof.

11. The process of Claim 1, wherein the at least one first electrolyte of step d) is an as sodium chloride, sodium sulphate, hydrochloric acid, sulphuric acid or any combination thereof.

12. The process of Claim 11, wherein quantity of the at least one first electrolyte to the partially treated POME is in a range of between 100 mg/L (ppm) to 10,000 mg/L (ppm).

13. The process of Claim 1, wherein the partially treated POME of step e) is treated via a first electro-oxidation process.

14. The process of Claim 13, wherein the electro-oxidation process is a single-stage electro- oxidation process or a two-stage electro-oxidation process.

15. The process of Claim 14, wherein the single-stage electro-oxidation process further includes adjusting pH of the partially treated POME.

16. The process of Claim 14, wherein the two-stage electro-oxidation process further includes adding an at least one second electrolyte to the partially treated POME, removing precipitate and/or suspended solids from the partially treated POME, treating the partially treated POME via a second electro-oxidation process and adjusting pH of the partially treated POME.

17. The process of Claims 15 and 16, wherein adjusting pH of the partially treated POME is carried out using sodium hydroxide, hydrochloric acid, sulphuric acid or any combination thereof.

18. The process of Claim 1, wherein the electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with no contactor in between the anode and cathode plates.

19. The process of Claim 18, wherein retention time for the electro-oxidation process is between 90 minutes to 600 minutes.

20. The process of Claim 1, wherein the electro-oxidation cell of step e) consists of two electrode plates which are positively charged (anode plate) and negatively charged (cathode plate) with a contactor in between the anode and cathode plates.

21. The process of Claim 20, wherein retention time for the electro-oxidation process is between 60 minutes to 300 minutes.

22. The process of Claim 1, wherein the electro-oxidation cell of step e) contains an electrical current in a range of between 5 amperes to 10,000 amperes for 1,000 L of the partially treated POME.

23. The process of Claim 1, wherein the precipitate and/or suspended solids of step f) are removed via clarification, induced air flotation system, filtration, solid liquid separation, sand filter, activated carbon filter or any combination thereof.

24. The process according to Claim 1, wherein retention time to produce the treated POME of step f) is in a range of between 60 minutes to 300 minutes.

25. The process according to Claim 1, wherein retention time to produce the zero liquid discharge of step g) is in a range of between 15 minutes to 60 minutes.