CN111233261A

CN111233261A - Treatment technology of potato starch production wastewater

Info

Publication number: CN111233261A
Application number: CN202010065838.4A
Authority: CN
Inventors: 薛鹏; 黄曙君; 杨哲; 孙晓峰
Original assignee: China Science And Technology Guoqing Beijing Environmental Development Co Ltd; Dongguan Jianyuanquan Water Treatment Technology Co ltd; Environmental Protection Institute of Light Industry
Current assignee: China Science And Technology Guoqing Beijing Environmental Development Co Ltd; Dongguan Jianyuanquan Water Treatment Technology Co ltd; Environmental Protection Institute of Light Industry
Priority date: 2020-01-20
Filing date: 2020-01-20
Publication date: 2020-06-05

Abstract

The application provides a potato starch waste water's processing technology includes: 1) carrying out protein separation treatment on the potato starch production wastewater in a protein separator to obtain wastewater subjected to protein separation treatment; 2) introducing the wastewater subjected to protein separation treatment into a membrane bioreactor for treatment to obtain first wastewater; 3) introducing the first wastewater into a nanofiltration membrane system for treatment to obtain second wastewater; 4) introducing the second wastewater into a reverse osmosis membrane system for treatment to obtain third wastewater; 5) and treating the third wastewater by using activated carbon to obtain discharge water. By using the method of the invention, the removal rate of COD can reach more than 99%. Aiming at the potato starch production wastewater with high concentration and high suspended matter, the method disclosed by the invention has the advantages of stable operation, lower operation cost, better economy, high organic matter removal rate, high comprehensive resource utilization rate and the like, and can stably meet the requirement of indirect emission limit in the discharge Standard of Water pollutants for starch industry (GB 25461-.

Description

Treatment technology of potato starch production wastewater

Technical Field

The application relates to a treatment technology of potato starch production wastewater.

Background

The waste water produced in the production of potato starch is waste liquid produced in the production process of potato starch, and is one of the most serious polluted waste water in the agricultural and sideline food processing industry. The waste water from potato starch production is highly polluted, the COD (chemical oxygen demand) content can reach 30000-40000 mg/L, and the waste water is directly discharged without treatment, so that huge harm is brought to the environment.

In the production process of potato starch, the discharge amount of waste water is large, about 8 tons of waste water is discharged per 1 ton of starch produced on average, the main components of the waste water are protein, sugar and the like, and starch granules, fibers and the like are also contained. The water quality components of the wastewater are as follows: the COD of the wastewater is generally 15000-25000 mg/L and BOD₅The biological oxygen demand for five days is 1500-6000 mg/L, the SS (suspended substance) is 10000-55000 mg/L, the pH is 3-5, and the wastewater belongs to acidic high-concentration high-suspended substance and difficult-to-treat organic wastewater.

The treatment method commonly used at home and abroad can be generally divided into: flocculation precipitation treatment, biological treatment and photosynthetic bacteria. Although the treatment methods are applied in practice, the potato starch processing belongs to seasonal production, and has the characteristics of short production period, large wastewater discharge amount, high COD generation concentration and the like, and the wastewater is difficult to discharge up to the standard. Moreover, due to the characteristics of potato starch production wastewater (e.g., large wastewater discharge, high protein and sugar contents, high suspended matter content, etc.), an efficient process that can be used to treat other types of wastewater has been shown to be inadequate for direct treatment of potato starch production wastewater.

Therefore, the intensive development of clean production and recycling economy, the continuous research on the recovery of useful substances in the potato starch wastewater, the reduction of the treatment difficulty of the wastewater while the recovery and utilization of the substances, and the development and application of the method for treating the starch production wastewater become hot spots.

Disclosure of Invention

The application provides a treatment technology of potato starch waste water, including the following steps:

1) carrying out protein separation treatment on the potato starch production wastewater in a protein separator to obtain wastewater subjected to protein separation treatment;

2) introducing the wastewater subjected to protein separation treatment into a membrane bioreactor for treatment to obtain first wastewater;

3) introducing the first wastewater into a nanofiltration membrane system for treatment to obtain second wastewater;

4) introducing the second wastewater into a reverse osmosis membrane system for treatment to obtain third wastewater;

5) and treating the third wastewater by using activated carbon to obtain discharge water.

In one embodiment, the protein separation treatment comprises sequentially adding polyaluminium chloride and cationic polyacrylamide with the weight average molecular weight of more than 18000 into potato starch production wastewater in a protein separator, wherein the weight ratio of the polyaluminium chloride to the cationic polyacrylamide is 100-1000: 1.

in one embodiment, the amount of the polyaluminum chloride is 100 to 500ppm and the amount of the cationic polyacrylamide is 0.1 to 5ppm based on the weight of the wastewater from potato starch production.

In one embodiment, a fiber rotary disc filter is arranged between the protein separator and the membrane bioreactor, so that the effluent from the protein separator passes through the fiber rotary disc filter and then is introduced into the membrane bioreactor.

In one embodiment, a precision filter is further arranged between the membrane bioreactor and the nanofiltration membrane system, and the first wastewater passes through the precision filter and then is introduced into the nanofiltration membrane system.

In one embodiment, the precision filter is two precision filters connected in parallel, both of which are individually equipped with a pressure gauge and a valve.

In one embodiment, the nanofiltration membrane system comprises a plurality of nanofiltration membrane components connected in parallel, the reverse osmosis membrane system comprises a plurality of reverse osmosis membrane components connected in parallel, each of the nanofiltration membrane components and the reverse osmosis membrane components is provided with a flow meter and an individual valve, and the individual closing and opening of each of the nanofiltration membrane components and the reverse osmosis membrane components are realized.

In one embodiment, the nanofiltration membrane module and the reverse osmosis membrane module are cleaned using hydrochloric acid and sodium hydroxide.

In one embodiment, the discharge water meets the indirect discharge limit requirements in the discharge Standard for Water contaminants from the starch industry (GB 25461-2010).

By using the method and the treatment system, the removal rate of COD can reach more than 99%. Aiming at the potato starch production wastewater with high concentration and high suspended matters, the process has the advantages of stable operation, lower operation cost, better economy, high organic matter removal rate, high comprehensive resource utilization rate and the like, and can ensure that the potato starch production wastewater stably meets the requirement of indirect discharge limit in the discharge standard of starch industrial water pollutants (GB 25461-2010).

Drawings

FIG. 1 shows a process flow diagram of the present application;

FIG. 2 illustrates a processing system for the method of the present application;

FIG. 3 shows a process flow of protein separation treatment in a protein separator.

Detailed Description

The present application is described in further detail below with reference to the figures and examples. The features and advantages of the present application will become more apparent from the description.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

In addition, the technical features described below in the different embodiments of the present application may be combined with each other as long as they do not conflict with each other.

In the present application, potato starch production wastewater is treated by protein separation in a protein separator. The protein separator which can be used for the application consists of seven parts, namely a flocculation area, a reaction area, a protein forming area, a protein floating area, a separation area, a filtration area and a flow splitting area. The protein separation treatment is carried out in a protein separator, and the principle comprises the following steps: air compression is utilized to instantaneously release micro bubbles for flotation, and a large amount of micro bubbles are generated by injecting into water and are adhered to solid protein particles in wastewater, wherein the density of the solid protein particles is close to that of water, so that an air floating body with the density smaller than that of water is formed. In addition, the protein separation processing mode in the protein separator is also different from the traditional air flotation: mixing water and gas by using an air dissolving system, inputting the mixture into a closed pipeline, calculating the reaction time of flocculate by using the positive-negative pressure difference of the water quantity of the tank body, and generating different micro bubbles by using different reaction effects in a reaction area section; the dissolved air quantity is changed alternately, which is convenient for the reaction of flocculating agent and the floating of protein particles.

FIG. 3 shows a process flow of protein separation treatment in a protein separator: injecting potato starch production wastewater (namely workshop potato juice) into a protein separator, adding polyaluminium chloride and cationic polyacrylamide with the weight average molecular weight of more than 18000, and introducing air into an adjusting tank through an air compressor; after the reaction tank, sequentially carrying out primary protein flocculation floating, hydrolytic acidification and contact oxidation, settling starch, crude fiber and protein particles in a settling floating separation area, and discharging the starch, the crude fiber and the protein particles through a pipeline; then, the water phase is subjected to two-stage protein flocculation and floating, and the flocculated protein is conveyed to dewatering equipment for dewatering through a scraper; then, the water phase passes through a cleaning and purifying area and a specific gravity water separation flow guide area and is discharged out of a protein separator. Meanwhile, the dissolved gas water obtained in the two-stage protein flocculation floating process can flow back to the reaction tank (first-stage dissolved gas water), or hydrolysis acidification (second-stage dissolved gas water) or contact oxidation (third-stage dissolved gas water) is carried out.

In this application, polyaluminum chloride is abbreviated as polyaluminum, and is abbreviated as PAC (polyaluminum chloride), which is between AlCl₃And Al (OH)₃A water-soluble inorganic high molecular polymer with a chemical general formula of [ Al₂(OH)_nCl_6-n·xH₂O]_m(m is less than or equal to 10, and n is 1-5), wherein m represents the polymerization degree, and n represents the neutral degree of the PAC product.

In the present application, cationic Polyacrylamide (PAM) with a weight average molecular weight of more than 18000 is used. To achieve good results, high molecular weight cationic polyacrylamides should be used, for example, the cationic polyacrylamides may have a weight average molecular weight of greater than or equal to 5000000.

In one embodiment, the protein separation treatment further comprises sequentially adding polyaluminum chloride and cationic polyacrylamide having a weight average molecular weight of more than 18000 to the potato starch production wastewater in a protein separator. In this application, it is very important to add polyaluminium chloride and cationic polyacrylamide with weight average molecular weight more than 18000 in turn, because the reaction time of polyaluminium chloride is very short, so strong mixing is needed after adding, while the action time of cationic polyacrylamide is long, the mixing is strong first and weak later-the strong first is for uniform mixing, and the weak later is for avoiding destroying flocs.

Moreover, the inventors of the present application have also found that the addition of polyaluminium chloride and cationic polyacrylamide is very critical for the treatment of waste water from potato starch production. In one embodiment, the adding amount of the polyaluminum chloride is 100-500 ppm and the adding amount of the cationic polyacrylamide is 0.1-5 ppm relative to the water amount (weight) of the potato starch production wastewater.

Furthermore, the amount of the chemical to be added varies with water quality. For example, in the water quality of the potato starch production wastewater listed in Table 1, the amount of polyaluminum chloride added to the protein separator is 300 to 350ppm and the amount of cationic polyacrylamide added is 1 to 2ppm, based on the amount (weight) of the potato starch production wastewater.

TABLE 1 general water quality table for waste water from potato starch production

Serial number	Item	Unit of	Concentration of
				1	COD_Cr	mg/L	30000～35000
2	BOD₅	mg/L	4000～6000
				3	SS	mg/L	2000～4000

For the water quality of the potato starch production wastewater listed in table 2, the adding amount of the polyaluminum chloride used in the protein separator is 150 to 200ppm and the adding amount of the cationic polyacrylamide is 0.5 to 1ppm, relative to the water amount of the potato starch production wastewater.

TABLE 2 general water quality table for potato starch production wastewater

Serial number	Item	Unit of	Concentration of
				1	COD_Cr	mg/L	15000～30000
2	BOD₅	mg/L	2000～4000
				3	SS	mg/L	1000～2000

In one embodiment, the weight ratio of the polyaluminium chloride to the cationic polyacrylamide is 20-5000: 1, preferably 100-1000: 1. preferably, the weight ratio of the polyaluminium chloride to the cationic polyacrylamide is 150-350: 1. preferably, the weight ratio of the polyaluminium chloride to the cationic polyacrylamide is 150-400: 1.

the weight ratio of polyaluminium chloride to cationic polyacrylamide and the respective amounts added are very important as defined in the present application, because:

(1) when the PAC medicament is added excessively, the water color turns yellow to form the dissolved PAC medicament color, the PAC medicament has peculiar smell and is pungent, and the PAC powder remains in water.

(2) When the PAM medicament is excessively added, the water body turns yellow and feels greasy when being wetted.

(3) The two drugs are excessive, and the flocculate has a nasal shape.

(4) When the PAC medicament is added in an insufficient amount, the water color is unchanged from the original juice, and no floc or floc is formed into millet granules. The amount of the flocculating agent is small and the flocculating agent sinks.

(5) When the PAM medicament is not added in enough quantity, the water body is blackish in color, does not feel hand when being wetted, does not change the water body color and the original juice, and has small flocculating constituent amount.

When the addition amount and the weight ratio of the two agents are in the range, the protein flocculate in the water is in a vanadium flower shape, floats upwards and is suspended on the water surface, and the color of the water body is clear relative to the color of the original juice water and is transparent.

In one embodiment, a fiber rotary disc filter is arranged between the protein separator and the membrane bioreactor, and the treated wastewater is filtered through the fiber rotary disc filter. Therefore, the materials such as agglomerated floc and the like can be further filtered by the fiber rotary disc filter, and the solid content of water introduced into a subsequent membrane bioreactor is further reduced. The fiber rotary disc filter consists of a central rotary drum, a rotary disc, a backwashing system, a matched control electrical system and the like, and the structure, the components and the like of the fiber rotary disc filter are known in the field. In the present application, the fiber rotary disk filter may use various known fiber rotary disk filters, and the size thereof may be determined according to the treatment amount, flow rate, etc. of the potato starch production wastewater.

In one embodiment, the water treated by protein separation in a protein separator and the water treated by a fiber disc filter can be sent to the next step for further treatment. The solid matter (mainly protein) obtained in the protein separation treatment step and the fiber rotary disc filter can be sold as feed or fertilizer.

The membrane bioreactor used for the application can not need strains and sludge of biochemical reaction, thereby reducing the construction cost and the operation cost. The membrane bioreactor can reduce floc in the latter stage, improve membrane fouling and bacterial infection, and reduce part of ammonia nitrogen. In the application, the MBR membrane of the membrane bioreactor is mainly used for removing residual flocculated impurities in water after protein separation treatment, reducing suspended matters in the water and protecting the water quality of nanofiltration. In one embodiment, the membrane bioreactor used in the present application is equipped with an aeration fan to volatilize and aerate ammonia nitrogen, COD, etc. to prevent organic matters from being stained on the surface of the membrane; meanwhile, a self-sucking pump and a backwashing pump negative pressure meter are also arranged, and chemical cleaning is required when the negative pressure reaches 8 kg. The membrane bioreactor is also provided with an electric control device which is configured to be back-washed for 2 minutes after being started for 8 minutes, and the temperature is between 5 and 45 ℃. The membrane bioreactor can customize membrane components according to actual requirements. The wastewater (first wastewater) treated by the membrane bioreactor enters the next step for further treatment.

In one embodiment, a precision filter is further arranged between the membrane bioreactor and the nanofiltration membrane system, and the first wastewater is further treated by the precision filter before being introduced into the nanofiltration membrane system for treatment. In this application, a 5 micron filter bag is provided within the precision filter. The solid-liquid separation is carried out by the precision filter, so that solid matters in the wastewater which is treated by the membrane bioreactor and enters a subsequent nanofiltration membrane system can be further filtered. In one embodiment, the number of precision filters may be two, both equipped with a pressure gauge and connected in parallel with each other. In the operation process, one of the two precision filters connected in parallel can be in a working state, the other precision filter can be in a standby state, whether the precision filter is blocked or not can be judged through a pressure gauge on the precision filter, the two precision filters can be switched in time, and the blocked filter can be cleaned or replaced.

In one embodiment, the filter bag built in 2 precision filters arranged between the membrane bioreactor and the nanofiltration membrane system has a filtration precision of 5 microns. This precision filter is bag filter, belongs to filter-pressing equipment, and in the filtrating gets into jar through the valve through the feed liquor pipe, under the effect of pump pressure, solid impurity in the filtrating is held back by the filter cloth bag, and the filtrating sack flows out the jar body from the liquid outlet to obtain limpid filtrating. Along with the increase of the filtering time, more and more solid impurities are trapped in the filter cloth bag, so that the filtering resistance is increased, the pressure in the tank is increased, when the pressure is increased to 0.45Mpa, the solid impurities in the filter cloth bag need to be removed, the input of the filtrate to be filtered into the tank is stopped, the upper cover is opened, the filter cloth bag is taken out, the impurities are poured out, and the filter bag is cleaned. And finally, putting the cleaned filter cloth bag into a tank, covering the tank with an upper cover, screwing the quick-opening bolt, and filtering again.

In one embodiment, the main specifications and technical parameters of the bag filter are shown in table 3.

TABLE 3 precision Filter Main Specifications and technical parameters

Form of filtration	Bag type high-grade non-woven filter cloth
		Area of filtration	1m² 2m²
Number of filter bags	3 are provided with
		Actual filtered flow	100t/h
Design pressure	0.613Mpa
		Maximum working pressure	0.45Mpa

Brief introduction of the structure: the quick-opening pressure-measuring tank comprises a tank body part, a quick-opening bolt, a filter bag, a stainless steel filter cylinder, a pressure gauge and the like.

The bag filter is a filtering device for solid-liquid separation, fine filtration and finished product filtration in the industries of grease, chemical industry, medicine, food, light industry and the like, and has the following characteristics:

① has compact structure and small floor space;

② filtering the filtrate from the previous step to obtain final product with high residue content;

③ has good filtering effect, the residue content in the filtrate is below 0.2 per mill, and the loss is low;

④ the production efficiency is high, and the two parallel devices can realize continuous production;

⑤ different filtrates and impurity particles can be selected from filter cloth bags with different materials and filtering precision.

And introducing the first wastewater or the wastewater treated by the precision filter into a nanofiltration membrane system for treatment to obtain second wastewater. The nanofiltration membrane system can be designed according to the treatment capacity. The assumption is usually calculated that the treatment capacity of a single nanofiltration membrane is 0.5t/h, and if the treatment capacity per unit time is 10t/h, 20 nanofiltration membranes are needed, but 25 nanofiltration membranes are usually designed for combination. In one embodiment, a high-pressure pollution-resistant nanofiltration membrane of Dow NF2700 in America can be used, the water inlet temperature is 5-40 ℃, the maximum pressure is 25kg, and an adjustable frequency converter is used for controlling the high-pressure pump, so that the pressure is controlled. In one embodiment, the nanofiltration membrane system may be a product of the patent of Jianyuan spring Water treatment technology, Inc. of Dongguan (CN 201811242660.5). The product has the function of replacing the membrane on line without stopping the machine, the membrane blockage condition in the system can be judged by the flow meter, and the membrane can be replaced without stopping the machine, so that the continuous operation and the stability of the whole system are ensured.

And introducing the second wastewater treated by the nanofiltration membrane system into a reverse osmosis membrane system for treatment to obtain third wastewater. The reverse osmosis system is calculated by taking 1t/h of water produced by a single membrane as a design basis, and 10 reverse osmosis membranes are configured on the assumption that 10t/h of water needs to be treated. The equipment has a starting self-washing function, the water inlet temperature is 5-40 ℃, the maximum pressure is 15kg, and the adjustable frequency converter is used for controlling the high-pressure pump so as to control the pressure. In one embodiment, the reverse osmosis membrane may be selected from the anti-fouling membranes Dow 30-365.

In one embodiment, the application comprises two sets of nanofiltration membrane systems connected in parallel and two sets of reverse osmosis membrane treatment systems connected in parallel, one set for use and one set for standby. In one embodiment, the nanofiltration membrane system comprises a plurality of nanofiltration membrane modules, the reverse osmosis membrane system comprises a plurality of reverse osmosis membrane modules, each of the nanofiltration membrane modules and the reverse osmosis membrane modules is provided with a flow meter and an individual valve, so that the nanofiltration membrane modules and the reverse osmosis membrane modules can be independently closed and opened, and the replacement of a single membrane module can be realized without stopping the operation.

The nanofiltration membrane system is arranged in front of the reverse osmosis membrane system, and aims to create a water inlet condition for reverse osmosis membrane treatment, remove partial salt and turbidity firstly, and prevent the reverse osmosis membrane from being blocked and cleaned frequently.

In one embodiment, for nanofiltration membrane systems and reverse osmosis membrane systems, the membrane modules are cleaned with hydrochloric acid and sodium hydroxide. The frequency and time of the cleaning can be determined according to the operating conditions. When the second wastewater and the third wastewater are treated in the nanofiltration membrane system and the reverse osmosis membrane system, concentrated water is generated in addition to water used in the next step, and the concentrated water can be used for land utilization.

In the application, the third waste water treated by the reverse osmosis membrane system is treated by activated carbon, so that the discharge water meeting the discharge standard can be obtained. In one embodiment, the discharge water meets the indirect discharge limit requirements of the discharge Standard for Water contaminants from the starch industry (GB 25461-2010).

In the present application, activated carbon treatment is performed using an activated carbon filter. Through the purification of the activated carbon filter, impurities such as organic matters, heavy metals, colloids and the like can be removed. The active carbon filter produced professionally can not only filter obvious impurities in water, but also filter impurities such as ions, smell and the like in the water, and obviously improve the water quality. The activated carbon filter can adsorb residual chlorine which cannot be removed in the preceding stage treatment, and simultaneously adsorb pollutant substances such as micromolecular organic matters leaked from the preceding stage, has obvious adsorption and removal effects on peculiar smell, colloid, pigment, heavy metal ions and the like in water, and also has the effect of reducing COD. Over time, the entrapment within the pores and between the particles of the activated carbon gradually increases, with a consequent increase in the pressure differential across the activated carbon filter, until the activated carbon fails. Under the normal condition, according to the pressure difference between the front and the back of the activated carbon filter, the filter material can be backwashed by reverse water flow, so that most of trapped matters adsorbed in the pores of the activated carbon are stripped and taken away by the water flow, and the adsorption function of the activated carbon is recovered; when the adsorption capacity of the activated carbon is saturated and completely fails, the activated carbon should be regenerated or replaced to meet the engineering requirements. In one embodiment, the activated carbon filter uses carbon steel as the canister body to facilitate replacement of the activated carbon. The water inlet temperature is 5-40 ℃, the operation has the functions of forward backwashing and sewage discharge, and the operation pressure can reach 25 kg. In the present application, the activated carbon treatment is performed after the reverse osmosis membrane treatment because the activated carbon has strong adsorption and is saturated quickly, and if the activated carbon is placed before nanofiltration or reverse osmosis, the frequency of activated carbon replacement is increased, and the operation cost is increased. But the use of the activated carbon after reverse osmosis can prolong the service time and ensure that the discharged water stably reaches the standard. The frequency of replacement of the activated carbon may be set as needed, and may be, for example, 15 days/time.

FIG. 1 shows a process flow diagram of the application, wherein potato starch production wastewater is subjected to protein separation treatment, polyaluminum chloride PAC and polyacrylamide PAM are added in the protein separation treatment process, suspended matters obtained by the protein separation treatment can be used as feed and/or fertilizer, and the treated wastewater is subjected to the next treatment; then, the wastewater enters a membrane bioreactor system (MBR membrane treatment system) for treatment, and the treated wastewater enters the next step for treatment; then, nanofiltration and reverse osmosis treatment are sequentially carried out, the obtained treated water is treated in the next step, and the obtained concentrated water can be used for land utilization; and then carrying out activated carbon adsorption treatment to obtain effluent meeting the discharge requirement. In the preferred embodiment, the effluent from the protein separator 10 is further treated by a fiber rotary disc filter 11 before entering the membrane bioreactor 20. In the preferred embodiment, the effluent from the membrane bioreactor 20 is further treated by a fine filter 21 before entering the nanofiltration membrane system 30.

FIG. 2 illustrates a processing system for the method of the present application. The treatment system comprises a protein separator 10, a membrane bioreactor 20, a nanofiltration membrane system 30, a reverse osmosis membrane system 40 and an activated carbon filter 50, which are sequentially communicated with each other in a fluid manner, so that the potato starch production wastewater can be sequentially treated by the components to finally obtain effluent meeting the discharge requirement.

In a preferred embodiment, a fiber rotary disc filter 11 is further disposed between the protein separator 10 and the membrane bioreactor 20, and the fiber rotary disc filter 11 is respectively in fluid communication with both the protein separator 10 and the membrane bioreactor 20, and can treat the effluent from the protein separator 10 to reduce the solid content in the influent of the subsequent membrane bioreactor 20. For a description of the fiber rotary disc filter 11, reference may be made to the above related contents of the present application, and the description thereof is omitted here.

The membrane bioreactor 20 used in the present application may not require the bacterial species and sludge of the biochemical reaction, thereby reducing the construction cost and the operation cost. For a description of the membrane bioreactor 20, reference may be made to the above description of the present application, and the description thereof is omitted here.

In a preferred embodiment, a fine filter 21 is further disposed between the membrane bioreactor 20 and the nanofiltration membrane system 30 to further remove the solid content of the water entering the nanofiltration membrane system 30. In one embodiment, there are two sets of the precision filters 21, and the two sets of precision filters 21 are connected in parallel in the treatment system. The two sets of precision filters 21 can be used as one set and one set is spare, so that a pressure device and a valve can be independently arranged to control the two sets of precision filters 21 respectively. In the operation process, one of the two precision filters connected in parallel can be in a working state, the other precision filter can be in a standby state, whether the precision filter is blocked or not can be judged through a pressure gauge on the precision filter, the precision filter can be switched in time, and the blocked filter can be cleaned or replaced.

In the preferred embodiment, there are two sets of nanofiltration membrane systems 30 connected in parallel in the treatment system. In the using process, one set is used, and the other set is cleaned and reserved. In the present application, each set of nanofiltration membrane system 30 includes a plurality of nanofiltration membrane modules, which are also connected in parallel and are respectively provided with a flow meter and a valve, so as to facilitate the respective control of the nanofiltration membrane modules, and enable the replacement of a single membrane module without shutdown. Likewise, in one embodiment, there are two sets of reverse osmosis membrane systems 40, also connected in parallel in the treatment system. In the using process, one set is used, and the other set is cleaned and reserved. In the present application, each set of reverse osmosis membrane system 40 includes a plurality of reverse osmosis membrane modules which are also connected in parallel and each of which has a flow meter and a valve to facilitate the respective control of the reverse osmosis membrane modules and to enable the replacement of a single membrane module without shutdown.

In one embodiment, a solid matter collector may be connected to the protein separator 10, the fiber disk filter 11 and the fine filter 21 for collecting and processing the solid matters obtained in the protein separator 10, the fiber disk filter 11 and the fine filter 21. The nanofiltration membrane system 30 and the reverse osmosis membrane system 40 may be provided with a concentrated water collector for collecting and treating concentrated water obtained in the nanofiltration membrane system 30 and the reverse osmosis membrane system 40.

By using the method and the treatment system, the removal rate of COD can reach more than 99%. Aiming at the potato starch production wastewater with high concentration and high suspended matters, the method and the treatment system have the advantages of stable operation, lower operation cost, better economy, high organic matter removal rate, high comprehensive resource utilization rate and the like, and can ensure that the potato starch production wastewater stably meets the requirement of indirect discharge limit in the discharge Standard of pollutants for starch industry (GB 25461-containing material 2010).

Examples

The following potato starch wastewater was treated according to the process shown in fig. 1, and the process conditions of the steps were as follows:

(1) quality of waste water

TABLE 4 Potato starch wastewater quality (unit: mg/L, excluding pH)

(2) Step operating conditions

a. And (3) carrying out protein separation treatment in a protein separator, wherein the consumption of PAC and PAM and the corresponding treatment amount of the potato starch wastewater are as follows:

TABLE 5 protein isolation dosing

Potato starch waste water treatment amount	Dosage of PAM	PAC dosage
			10t/h	1kg of water is mixed with 2 tons of water per 4 hours	50kg of water is mixed with 2 tons of water per 2 hours
15t/h	1.5kg of water is mixed with 2 tons of water per 4 hours	75kg of water is mixed with 2 tons of water per 2 hours
			20t/h	2kg of water is mixed with 2 tons of water per 4 hours	100kg of water is mixed with 2 tons of water per 2 hours
25t/h	2.5kg of water is mixed with 2 tons of water per 3 hours	150kg of water is mixed with 2 tons of water per 2 hours
			30t/h	3kg of water is mixed with 2 tons of water per 3 hours	150kg of water is mixed with 2 tons of water per 2 hours
35t/h	3.5kg of water is mixed with 2 tons of water per 2 hours	150kg of water is mixed with 2 tons of water per 1.5h
			40t/h	4kg of water is mixed with 2 tons of water per 1 hour	150kg of water is mixed with 2 tons of water per 1 hour

MBR membrane treatment system:

TABLE 6MBR Membrane Module Standard operating conditions

c. And (4) nanofiltration:

TABLE 7 Main technical parameters

Model number	JY-NF-60T
		Yield of the product	Not less than 60 t/h
Number of nanofiltration membranes	120 strips
		Power supply	AC380V 50HZ
Rated power	75kW
		Rated current	220A
Equipment incoming line requirement	70mm²
		Inflow rate of water	120t/h
Water inlet pool	3000 cubic meter
		Water outlet pool	300 cubic meter
Working pressureForce of	15MPa
		Outer dimension	6000×2300×2600mm
Net weight of machine	3500kg

d. Reverse osmosis:

TABLE 8 Main technical parameters

(3) The water quality of the effluent is adsorbed by the active carbon

TABLE 9 quality of effluent (unit: mg/L)

By adopting the embodiment, suspended matters, COD, ammonia nitrogen, total nitrogen and total phosphorus in the wastewater can be obviously reduced by adopting the method disclosed by the invention, and the discharged water meets the requirement of indirect discharge limit value in the discharge standard of pollutants for water in the starch industry (GB 25461-2010).

In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", "left", "right", and the like indicate orientations or positional relationships based on operational states of the present application, and are only used for convenience in describing and simplifying the present application, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application.

In the description of the present application, it is to be noted that the terms "mounted," "connected," and "connected" are to be construed broadly unless otherwise explicitly stated or limited. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

The present application has been described above with reference to preferred embodiments, but these embodiments are merely exemplary and merely illustrative. On the basis of the above, the present application can be subjected to various substitutions and improvements, and the substitutions and the improvements are all within the protection scope of the present application.

Claims

1. A treatment technology of potato starch production wastewater comprises the following steps:

2. The treatment method according to claim 1, wherein the protein separation treatment comprises sequentially adding polyaluminium chloride and cationic polyacrylamide with the weight average molecular weight of more than 18000 into potato starch production wastewater in a protein separator, wherein the weight ratio of the polyaluminium chloride to the cationic polyacrylamide is 100-1000: 1.

3. the treatment method according to claim 2, wherein the polyaluminum chloride is used in an amount of 100 to 500ppm and the cationic polyacrylamide is used in an amount of 0.1 to 5ppm, based on the weight of the water in the wastewater from potato starch production.

4. The treatment method according to claim 1, wherein a fiber rotary disc filter is further arranged between the protein separator and the membrane bioreactor, so that the effluent from the protein separator passes through the fiber rotary disc filter and then is introduced into the membrane bioreactor.

5. The treatment method according to claim 1, wherein a precision filter is further arranged between the membrane bioreactor and the nanofiltration membrane system, and the first wastewater passes through the precision filter and then is introduced into the nanofiltration membrane system.

6. The process of claim 5, wherein the precision filter is two precision filters connected in parallel, both of which are individually fitted with a pressure gauge and a valve.

7. The process of claim 1 wherein the nanofiltration membrane system comprises a plurality of nanofiltration membrane modules connected in parallel, the reverse osmosis membrane system comprises a plurality of reverse osmosis membrane modules connected in parallel, each of the nanofiltration and reverse osmosis membrane modules is equipped with a flow meter and a separate valve to enable separate closing and opening of each of the nanofiltration and reverse osmosis membrane modules.

8. The process of claim 7, wherein the nanofiltration membrane module and the reverse osmosis membrane module are washed with hydrochloric acid and sodium hydroxide.

9. The treatment method as claimed in claim 1, wherein the discharge water meets the requirement of indirect discharge limit in the discharge Standard for Water contaminants for the starch industry (GB 25461-2010).