NL2028159B1

NL2028159B1 - Method for treating vegetable-squeezed waste liquid

Info

Publication number: NL2028159B1
Application number: NL2028159A
Authority: NL
Inventors: Wang Jianhong; Qu Jian; Tian Senlin
Original assignee: Univ Kunming Science & Technology
Priority date: 2021-03-29
Filing date: 2021-05-06
Publication date: 2022-10-12
Also published as: CN113149344B; AU2021102247A4; CN113149344A

Abstract

The present disclosure provides a method for treating a vegetable-squeezed waste liquid, and relates to the technical ﬁeld of wastewater treatment. The present disclosure 5 uses polymeric ferric sulfate (PFS) and cationic polyacrylamide (PAM) to remove most of suspended solids (SS) and total phosphorus (TP) in the vegetable-squeezed waste liquid. The present disclosure sequentially conducts an anaerobic treatment, a primary anoxic denitrification treatment, a primary oxic treatment, an advanced oxidation process (AOP), a secondary anoxic denitrification treatment and a secondary oxic 10 treatment to reduce chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN), TP and chroma in the vegetable-squeezed waste liquid. In this way, a ﬁnal efﬂuent meets the Level l-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB18918-2002), and can be discharged directly.

Description

-1- METHOD FOR TREATING VEGETABLE-SQUEEZED WASTE LIQUID

TECHNICAL FIELD

[01] The present disclosure relates to the technical field of wastewater treatment, in particular to a method for treating a vegetable-squeezed waste liquid.

BACKGROUND ART

[02] Alarge amount of waste vegetable leaves are generated during the development of the vegetable planting industry. In order to avoid environmental pollution caused by discarding the waste vegetable leaves directly, the waste vegetable leaves need to be treated. The existing treatment methods are as follows:

[03] Waste vegetable leaves are used to prepare a water-soluble fertilizer. With a water content as high as 95%, waste vegetable leaves can be used to prepare a water- soluble fertilizer through anaerobic fermentation. Although the process is simple, it requires a matching irrigation schedule. However, it is hard to effectively match the water-soluble fertilizer production with the irrigation schedule in terms of quantity and quality. In other words, when fertilization is needed, there may not be sufficient water- soluble fertilizer made of waste vegetable leaves. When it is not needed, the water- soluble fertilizer is produced in large quantities. Take Songming, Luliang, Tonghai and Jinning, the major vegetable planting counties in Yunnan Province, China as examples, there are thousands of tons of waste vegetable leaves every day at peak times, which can produce thousands of tons of water-soluble fertilizer. However, it is not possible to consume such a large amount of water-soluble fertilizer every day, and the temporary storage of the water-soluble fertilizer is also a big challenge. Any problem occurring in this process will affect the stability of waste vegetable leaf treatment.

[04] Waste vegetable leaves are used to prepare fermented feed. Chinese patent CN104222504A discloses a method for preparing fermented feed from waste vegetable leaves. Specifically, waste vegetable leaves are sorted to remove spoiled vegetable leaves, mixed with auxiliary materials such as corn flour and probiotics, vacuum- dehydrated, and allowed to stand for fermentation to prepare green feed. Due to the high water content, the waste vegetable leaves are easy to spoil during the fermentation process, making it hard to produce qualified green feed. In addition, the pesticide residues will also affect the quality of the fermented feed, thereby bringing a considerable risk to the application of this technology. At present, there is no feed

Do manufacturer that can stably produce fermented feed from waste vegetable leaves.

[05] Waste vegetable leaves are crushed, squeezed and separated into a solid residue for fermentation to prepare an organic fertilizer and a waste liquid for concentrated treatment. The waste liquid has high chemical oxygen demand (COD), ammonia nitrogen (NH-N) and chroma that are difficult to remove. Chinese patent CN208136048U discloses a treatment system for vegetable-squeezed wastewater. The system treats the vegetable-squeezed wastewater essentially by coagulation, air flotation, hydrolytic acidification, anaerobic fermentation via an upflow anaerobic sludge blanket (UASB), catalytic oxidation, secondary sedimentation and mechanical filtration or carbon filtration. According to the present practice, the effluent treated by this system cannot meet the Level I-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB18918-2002). Meanwhile, the cost of carbon filtration at the end is high, and the treatment of waste carbon needs to be improved.

[06] Chinese patent CN111807609A discloses a method for treating a biogas slurry by a vegetable leaf/fruit and vegetable waste liquid. This method adopts a flocculation tank, a sedimentation tank, an air flotation tank, a primary anoxic (A) tank, a primary oxic (O) tank, a secondary A tank, a secondary O tank and a decolorization tank, where the secondary O tank is a built-in membrane bioreactor (MBR). In this method, the vegetable leaf/fruit and vegetable waste liquid is subjected to flocculation and sedimentation treatments to serve as a supplementary carbon source required for the denitrification of the secondary A tank. Since the high-molecular-weight plant fiber (or difficult-to-remove COD) in the vegetable leaf/fruit and vegetable waste liquid is difficult to be utilized by microorganisms, the vegetable leaf/fruit and vegetable waste liquid is not suitable as a supplementary carbon source. On the contrary, it will affect the quality of the effluent from the secondary O tank, making it hard to meet the Level 1-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB18918-2002).

[07] According to the literature and field investigations in major vegetable planting provinces Yunnan and Shandong in China, there is currently no process that can treat the vegetable-squeezed waste liquid to reach or exceed the Level 1-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB18918-2002).

3-

SUMMARY

[08] An objective of the present disclosure is to provide a method for treating a vegetable-squeezed waste liquid. The present disclosure can make a final effluent of the vegetable-squeezed waste liquid meet the Level 1-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB 18918-2002), such that the effluent can be discharged directly.

[09] To achieve the objective of the present disclosure, the present disclosure provides the following technical solutions:

[10] The present disclosure provides a method for treating a vegetable-squeezed waste liquid, including the following steps:

[11] (1) mixing a vegetable-squeezed waste liquid with polymeric ferric sulfate (PFS) and cationic polyacrylamide (PAM) for a sedimentation treatment to obtain a vegetable-squeezed filtrate;

[12] (2) subjecting the vegetable-squeezed filtrate to an anaerobic treatment to obtain an anaerobic treated-effluent;

[13] (3) subjecting the anaerobic treated-effluent to a primary anoxic denitrification treatment to obtain a primary anoxic treated-effluent;

[14] (4) subjecting the primary anoxic treated-effluent to a primary oxic treatment to obtain a primary oxic treated-effluent;

[15] (5) mixing the primary oxic treated-effluent with hydrogen peroxide and ferrous sulfate for an advanced oxidation process (AOP) to obtain an AOP treated-effluent;

[16] (6) subjecting the AOP treated-effluent to a secondary anoxic denitrification treatment to obtain a secondary anoxic treated-effluent; and

[17] (7) subjecting the secondary anoxic treated-effluent to a secondary oxic treatment to obtain an effluent.

[18] Preferably, in step (1), chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN) and total phosphorus (TP) in the vegetable-squeezed waste liquid may be 5000-20000 mg/L, 400-1400 mg/L, 450-1700 mg/L and 1000-3500 mg/L, respectively.

[19] Preferably, in step (2), the COD in the anaerobic treated-effluent may be 3000- 5000 mg/L.

[20] Preferably, in step (3), a total concentration of nitrate (NO3°) and nitrite (NO2") in the primary anoxic treated-effluent may be less than 10 mg/L.

[21] Preferably, in step (4), dissolved oxygen (DO) in the primary oxic treatment may

4- be 3-6 mg/L.

[22] Preferably, in step (4), part of the primary oxic treated-effluent, which is 300- 400% of total anaerobic treated-effluent, may be refluxed for the primary anoxic denitrification treatment in step (3).

[23] Preferably, in step (5), the hydrogen peroxide may have a mass concentration that may be 1.85-2.0 times the COD of the primary oxic treated-effluent, and a molar ratio of the ferrous sulfate to the hydrogen peroxide may be 0.8:1.

[24] Preferably, in step (6), methanol may be added in the secondary anoxic denitrification treatment as a supplementary carbon source, which may have a mass concentration that may be 3.1-3.34 times a total concentration of NO: and NO- in the AOP treated-effluent.

[25] Preferably, the treatment method may further include: subjecting, after the secondary oxic treatment, the secondary oxic treated-effluent to a sedimentation treatment to obtain an effluent.

[26] Preferably, the COD, NH:-N, TN, TP, chroma and suspended solids (SS) in the effluent may be 20-50 mg/L, 0.24-4.8 mg/L, 2.4-14.5 mg/L, 0.25-0.48 mg/L, 5-20 and

0.5-10 mg/L, respectively.

[27] The present disclosure provides a method for treating a vegetable-squeezed waste liquid, including the following steps: (1) mixing a vegetable-squeezed waste liquid with PFS and cationic PAM for a sedimentation treatment to obtain a vegetable-squeezed filtrate; (2) subjecting the vegetable-squeezed filtrate to an anaerobic treatment to obtain an anaerobic treated-effluent; (3) subjecting the anaerobic treated-effluent to a primary anoxic denitrification treatment to obtain a primary anoxic treated-effluent; (4) subjecting the primary anoxic treated-effluent to a primary oxic treatment to obtain a primary oxic treated-effluent; (5) mixing the primary oxic treated-effluent with hydrogen peroxide and ferrous sulfate for an AOP to obtain an AOP treated-eftluent; (6) subjecting the AOP treated-effluent to a secondary anoxic denitrification treatment to obtain a secondary anoxic treated-effluent; and (7) subjecting the secondary anoxic treated-effluent to a secondary oxic treatment to obtain an effluent. The present disclosure uses the PFS and cationic PAM to remove most of the SS and TP in the vegetable-squeezed waste liquid. The present disclosure sequentially conducts the anaerobic treatment, the primary anoxic denitrification treatment, the primary oxic treatment, the AOP, the secondary anoxic denitrification treatment and the secondary oxic treatment to reduce the COD, NH:-N, TN, TP, chroma and SS in the vegetable-

-5- squeezed waste liquid. In this way, the final effluent meets the Level 1-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB 18918-2002), and can be discharged directly. In addition, the present disclosure controls the cost of treating 1 ton of vegetable-squeezed waste liquid at 35-45 yuan. The present disclosure features simple process, low cost, convenient management and high practical value, and can be used to promote the healthy, environmentally friendly and sustainable development of the vegetable planting industry.

BRIEF DESCRIPTION OF THE DRAWINGS

[28] FIG. 11s a flowchart of a method for treating a vegetable-squeezed waste liquid according to an example of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[29] The present disclosure provides a method for treating a vegetable-squeezed waste liquid. The method includes the following steps:

[30] (1) Mix a vegetable-squeezed waste liquid with polymeric ferric sulfate (PFS) and cationic polyacrylamide (PAM) for a sedimentation treatment to obtain a vegetable- squeezed filtrate.

[31] (2) Subject the vegetable-squeezed filtrate to an anaerobic treatment to obtain an anaerobic treated-effluent.

[32] (3) Subject the anaerobic treated-effluent to a primary anoxic denitrification treatment to obtain a primary anoxic treated-effluent.

[33] (4) Subject the primary anoxic treated-effluent to a primary oxic treatment to obtain a primary oxic treated-effluent.

[34] (5) Mix the primary oxic treated-effluent with hydrogen peroxide and ferrous sulfate for an advanced oxidation process (AOP) to obtain an AOP treated-effluent.

[35] (6) Subject the AOP treated-effluent to a secondary anoxic denitrification treatment to obtain a secondary anoxic treated-effluent.

[36] (7) Subject secondary anoxic treated-effluent to a secondary oxic treatment to obtain an effluent.

[37] In the present disclosure, unless otherwise specified, the reagents used are commercially available products well known to those skilled in the art.

[38] The present disclosure mixes a vegetable-squeezed waste liquid with PFS and cationic PAM for a sedimentation treatment to obtain a vegetable-squeezed filtrate. The

6- present disclosure has no special requirement on the source of the vegetable-squeezed waste liquid, and a vegetable-squeezed waste liquid well known to those skilled in the art may be used. In a specific example of the present disclosure, chemical oxygen demand (COD) in the vegetable-squeezed waste liquid is preferably 5000-20000 mg/L, more preferably 8970-14610 mg/L. Ammonia nitrogen (NH3-N) is preferably 400-1400 mg/L, more preferably 641-1089mg/L. Total nitrogen (TN) is preferably 450-1700 mg/L, more preferably 553-950 mg/L. Total phosphorus (TP) is preferably 1000-3500 mg/L, more preferably 1773-2975mg/L. In the present disclosure, chroma in the vegetable-squeezed waste liquid is preferably 400-600, more preferably 450-470; suspended solids (SS) is preferably 5400-5500 mg/L.

[39] In an example of the present disclosure, the vegetable-squeezed waste liquid is prepared by crushing waste vegetable leaves, squeezing and separating. The present disclosure has no special requirement on the methods of crushing, squeezing and separating, and methods well known to those skilled in the art may be used. The present disclosure directly treats the vegetable-squeezed waste liquid without pretreatment or dilution.

[40] In the present disclosure, the vegetable-squeezed waste liquid, the PFS and the cationic PAM are specifically preferably mixed as follows: the vegetable-squeezed waste liquid 1s sequentially mixed with the PFS and the cationic PAM. In the present disclosure, a concentration of the PFS is preferably 1500-2500 ppm, more preferably 1500-2200 ppm; a concentration of the PAM is preferably 10-20 ppm, more preferably 10-15 ppm. In the actual operation, if there are more SS, more PFS and PAM may be added as appropriate. By adding the PFS and the cationic PAM, the present disclosure can remove more than 90% of SS and more than 98% of TP in the vegetable-squeezed waste liquid.

[41] Inthe present disclosure, the sedimentation treatment is preferably conducted in a sedimentation tank. The present disclosure has no special requirement on the specific structure of the sedimentation tank, and a sedimentation tank well known to those skilled in the art may be used.

[42] In the present disclosure, by subjecting the vegetable-squeezed waste liquid to the sedimentation treatment, a vegetable-squeezed liquid and a coagulation residue are produced. In the present disclosure, the coagulation residue is preferably subjected to pressure filtration to obtain a filtrate; then the filtrate is mixed with the vegetable- squeezed liquid to obtain the vegetable-squeezed filtrate.

7.

[43] In the present disclosure, the pressure filtration is preferably conducted at 0.4-

0.55 MPa in a filter press, more preferably a belt filter. A solid content charged into the filter press is preferably below 1%, and a solid content discharged is preferably 5-8%. In the present disclosure, a filter residue obtained by the filter press is used to prepare an organic fertilizer. The present disclosure effectively removes water in the coagulation residue for subsequent utilization by limiting a pressure filtration parameter.

[44] After obtaining the vegetable-squeezed filtrate, the present disclosure subjects the vegetable-squeezed filtrate to an anaerobic treatment to obtain an anaerobic treated- effluent. In the present disclosure, the anaerobic treatment is preferably conducted in an anaerobic reactor. The present disclosure has no special requirement on the specific structure of the anaerobic reactor, and an anaerobic reactor well known to those skilled in the art may be used. In the present disclosure, dissolved oxygen (DO) in the anaerobic treatment is preferably less than 0.2 mg/L.

[45] In the present disclosure, the anaerobic treatment is preferably conducted in the presence of anaerobic granular sludge. In the present disclosure, the anaerobic granular sludge is preferably obtained by anaerobic culture acclimation of activated sludge (AS). In the present disclosure, bacteria added during the anaerobic culture acclimation preferably include anaerobic hydrolysis bacteria and NH:-N degradation bacteria, specifically preferably anaerobic hydrolysis bacteria, acidifying bacteria, acid and hydrogen producing bacteria and methanogenic bacteria. In the present disclosure, the anaerobic hydrolysis bacteria are added in the anaerobic treatment to further strengthen the anaerobic hydrolysis and accelerate anaerobic fermentation, and the NH:-N degradation bacteria are added to convert organic nitrogen into inorganic nitrogen, which is convenient for a subsequent nitrification reaction. In the present disclosure, the anaerobic granular sludge is preferably 20-30% of a total liquid volume of the reactor.

[46] In the present disclosure, the anaerobic treatment is preferably conducted in the presence of an elastic filler to increase the attachment of the bacteria, prevent the loss of the bacteria and increase the sludge concentration, thereby increasing volumetric loading. In the present disclosure, the elastic filler is preferably a composite filamentary material. The elastic filler has a diameter of preferably 55-80 mm, a tensile strength of preferably > 2800 N and a specific surface area (SSA) of preferably 4000-5000 m?2/m’. After a biofilm is formed, a maximum sludge amount on the elastic filler is preferably 10-15 g/L, and a maximum loading rate of biochemical oxygen demand (BOD) is preferably 1.5-3.5 kg/m’ed. In the present disclosure, the elastic filler is preferably 30-

-8- 60% of a reactor volume.

[47] Inthe present disclosure, the anaerobic treatment is conducted for preferably 30- 40 h, more preferably 35-38 h. In the present disclosure, the anaerobic microorganisms are used to degrade the COD in the anaerobic treatment. In the present disclosure, the COD in the anaerobic treated-effluent is preferably 3000-5500 mg/L, more preferably 3153-5113 mg/L. The present disclosure controls the COD in the anaerobic treated- effluent within the above range to ensure a carbon source required for the subsequent primary anoxic denitrification treatment. Meanwhile, the present disclosure converts the high-molecular-weight organic matter into low-molecular-weight organic matter, which is convenient for the utilization of denitrifying bacteria.

[48] After obtaining the anaerobic treated-effluent, the present disclosure subjects the anaerobic treated-effluent to a primary anoxic denitrification treatment to obtain a primary anoxic treated-effluent. In a specific example of the present disclosure, preferably part of the primary oxic treated-effluent is refluxed, and the refluxed primary oxic treated-effluent is mixed with the anaerobic treated-effluent for the primary anoxic denitrification treatment. The specific process parameters are shown below.

[49] In the present disclosure, the primary anoxic denitrification treatment is conducted at a rate of 8-15 mg NO3;™-N/L+h, more preferably 9.5-11.25 mg NO3-N/Leh. In the present disclosure, the primary anoxic denitrification treatment is conducted for preferably 10-12 h. The present disclosure rapidly removes the COD and nitrate nitrogen (NO:-N) through the primary anoxic denitrification treatment. In the present disclosure, the primary anoxic denitrification treatment is preferably conducted in a primary anoxic tank. The present disclosure has no special requirement on the specific structure of the primary anoxic tank, and a primary anoxic tank well known to those skilled in the art may be used. In the present disclosure, the DO in the primary anoxic denitrification treatment is preferably 0.2-0.6 mg/L. [S0] In the present disclosure, the primary anoxic denitrification treatment is preferably conducted in the presence of anoxic denitrification granular sludge, which is preferably obtained by culture acclimation of AS. In the present disclosure, bacteria added during the culture acclimation preferably include anaerobic hydrolysis bacteria, NH:-N degradation bacteria and denitrifying bacteria, specifically preferably anaerobic hydrolysis bacteria, acidifying bacteria, acid and hydrogen producing bacteria, methanogenic bacteria and denitrifying bacteria. In the primary anoxic denitrification treatment of the present disclosure, the anaerobic hydrolysis bacteria are added to

9- enhance anaerobic hydrolysis and acidification, promote the production of low- molecular-weight butyric acid and acetic acid and facilitate denitrification. The NH3-N degradation bacteria are added to convert organic nitrogen into inorganic nitrogen, which is convenient for a subsequent nitrification reaction. The denitrifying bacteria are added to improve denitrification efficiency.

[51] Inthe present disclosure, the anoxic denitrification granular sludge is preferably 8-20% of a total liquid volume of the reactor. [S2] In the present disclosure, the primary anoxic denitrification treatment is preferably conducted in the presence of an elastic filler to immobilize the bacteria, prevent the loss of weak bacteria and increase the sludge concentration, thereby increasing volumetric loading. In the present disclosure, the elastic filler is preferably a composite filamentary material. The elastic filler has a diameter of preferably 55-80 mm, a tensile strength of preferably > 2800 N and an SSA of preferably 4000-5000 mm. After a biofilm 1s formed, a maximum sludge amount on the elastic filler 1s preferably 10-15 g/L, and a maximum loading rate of denitrification is preferably 0.05-0.15 kg/m’ed. In the present disclosure, the elastic filler is preferably 30-60% of a reactor volume.

[53] Inthe present disclosure, a total concentration of nitrate (NO:") and nitrite (NO2") in the primary anoxic treated-effluent is preferably less than 10 mg/L, more preferably Omg/L.

[54] After obtaining the primary anoxic treated-effluent, the present disclosure subjects the primary anoxic treated-effluent to a primary oxic treatment to obtain a primary oxic treated-effluent. In the present disclosure, the DO in the primary oxic treated-effluent is preferably 3-6 mg/L, more preferably 4-5 mg/L. In the present disclosure, the primary oxic treatment is conducted for preferably 11-14 h, more preferably 12-13 h. In the present disclosure, nitrifying bacteria are used to convert NH3- N into NOs-N in the primary oxic treatment.

[55] In the present disclosure, the primary oxic treatment is preferably conducted in a primary oxic tank. The present disclosure has no special requirement on the specific structure of the primary oxic tank, and a primary oxic tank well known to those skilled in the art may be used. In the present disclosure, a loading rate of NH3-N in the primary oxic tank is 0.11-0.21 kg NH3/m’ed.

[56] In the present disclosure, the primary oxic treatment is preferably conducted in the presence of oxic nitrification sludge. In the present disclosure, the oxic nitrification

-10- sludge is preferably ordinary oxic AS from a municipal sewage treatment plant. In the present disclosure, a mass of the oxic nitrification sludge is preferably 6-12 mg/L, more preferably 8.5-8.8 mg/L.

[57] In the present disclosure, the primary oxic treatment is preferably conducted in the presence of an elastic filler to immobilize the bacteria, prevent the loss of weak bacteria, ensure full nitrification while removing the organic matter, and increase the sludge concentration, thereby increasing volumetric loading. In the present disclosure, the elastic filler is preferably a composite filamentary material. The elastic filler has a diameter of preferably 55-80 mm, a tensile strength of preferably > 2800 N and an SSA of preferably 4000-5000 m?/m?. After a biofilm is formed, a maximum sludge amount on the elastic filler is preferably 10-15 g/L, and a maximum loading rate of BOD is preferably 0.5-1.5 kg/m?ed. In the present disclosure, the elastic filler is preferably 30- 60% of a reactor volume.

[58] In the present disclosure, NHs-N in the primary oxic treated-effluent is preferably less than 10 mg/L, more preferably 2.20-4.38 mg/L. A total concentration of NO: and NO- in the primary oxic treated-effluent is preferably 130-250 mg/L, more preferably 136-175 mg/L.

[59] Inthe present disclosure, part of the primary oxic treated-effluent, which is 300- 400% of total anaerobic treated-effluent, is refluxed for the primary anoxic denitrification treatment. In the present disclosure, the reflux ratio of the primary oxic treated-effluent depends on a denitrification requirement, that is, a higher denitrification requirement leads to a larger reflux ratio, and a lower denitrification requirement leads to a smaller reflux ratio. In the present disclosure, the refluxed primary oxic treated- effluent can return NO: and NO: that can be oxidized into NO:-N to the primary anoxic denitrification treatment so as to promote denitrification.

[60] After obtaining the primary oxic treated-effluent, the present disclosure mixes the primary oxic treated-effluent with hydrogen peroxide and ferrous sulfate for an AOP to obtain an AOP treated-effluent. In the AOP, the present disclosure degrades the difficult-to-degrade high-molecular-weight organic matter into easily degradable low- molecular-weight organic matter, laying a foundation for subsequent biochemical degradation. Meanwhile, the present disclosure reduces the chroma through the AOP, making the effluent meet the Level 1-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB18918-2002).

[61] In the present disclosure, the AOP is preferably conducted in an advanced

-11- oxidation tank. The present disclosure has no special requirement on the specific structure of the advanced oxidation tank, and an advanced oxidation tank well known to those skilled in the art may be used.

[62] In the present disclosure, the hydrogen peroxide preferably has a mass concentration that is 1.85-2.0 times the COD of the primary oxic treated-effluent. In a specific example of the present disclosure, the hydrogen peroxide has a mass concentration that is 1.85-2.0 times the COD of an influent of the advanced oxidation tank. In the present disclosure, a molar ratio of the ferrous sulfate to the hydrogen peroxide is preferably 0.8:1. The present disclosure controls the molar ratio of the ferrous sulfate to the hydrogen peroxide within the above range, so as to avoid the adverse effect of excessive iron on a subsequent biochemical reaction and to give full play to the oxidation effect of the hydrogen peroxide (H20y). In the present disclosure, it is not necessary to add an acid or alkali to adjust the pH of the system in the AOP.

[63] In the present disclosure, the primary oxic treated-effluent is specifically preferably mixed with the hydrogen peroxide and the ferrous sulfate as follows: the primary oxic treated-effluent is firstly mixed with the hydrogen peroxide and then mixed with the ferrous sulfate for an oxidation-reduction reaction. In the present disclosure, the oxidation-reduction reaction is preferably conducted under stirring for preferably 4-6 h, more preferably 4-5 h.

[64] In the present disclosure, preferably, after the AOP, an obtained mixed liquid is subjected to a sedimentation treatment to obtain a supernatant liquid and a turbid liquid. The turbid liquid is subjected to pressure filtration to obtain a filtrate and a filter residue. The filtrate and the supernatant liquid are mixed to obtain the AOP treated -effluent. In the present disclosure, the pressure filtration is preferably conducted at 0.4-0.55 MPa in a filter press, more preferably a belt filter. A solid content charged into the filter press is preferably below 2%, and a solid content discharged is preferably 8-12%. In the present disclosure, the filter residue obtained by the filter press is treated as iron residue.

[65] After obtaining the AOP treated-effluent, the present disclosure subjects the AOP treated-effluent to a secondary anoxic denitrification treatment to obtain a secondary anoxic treated-effluent. In the present disclosure, the secondary anoxic denitrification treatment is preferably conducted in a secondary anoxic tank. The present disclosure has no special requirement on the specific structure of the secondary anoxic tank, and an anoxic denitrification tank well known to those skilled in the art may be used.

-12-

[66] In the present disclosure, the DO in the secondary anoxic denitrification treatment 1s preferably 0.2-0.6 mg/L. In the present disclosure, the secondary anoxic denitrification treatment is conducted at a rate of 10-17 mg NO3-N/L¢«h, more preferably

11.33-14.58 mg NO;-N/Leh. In the present disclosure, the secondary anoxic denitrification treatment is conducted for preferably 10-14 h, more preferably 12-13 h.

[67] In the present disclosure, the secondary anoxic denitrification treatment is preferably conducted in the presence of anoxic AS. In the present disclosure, the anoxic AS is preferably obtained by culture acclimation of AS, and bacteria added in the culture acclimation preferably come from sludge in an anoxic phase of a municipal sewage treatment plant, and specifically preferably include NH3-N conversion bacteria and denitrifying bacteria. In the present disclosure, a mass of the anoxic AS is preferably 6- 12 mg/L, more preferably 8.5-9.8 mg/L.

[68] In the present disclosure, the secondary anoxic denitrification treatment is preferably conducted in the presence of an elastic filler to immobilize the bacteria, prevent the loss of the bacteria and increase the sludge concentration, thereby increasing volumetric loading. In the present disclosure, the elastic filler is preferably a composite filamentary material. The elastic filler has a diameter of preferably 55-80 mm, a tensile strength of preferably > 2800 N and an SSA of preferably 4000-5000 m2/m?. After a biofilm is formed, a maximum sludge amount on the elastic filler is preferably 10-15 g/L, and a maximum loading rate of denitrification is preferably 0.05-0.15 kg/m’ed. In the present disclosure, the elastic filler is preferably 30-60% of a reactor volume.

[69] In the present disclosure, methanol is preferably added in the secondary anoxic denitrification treatment as a supplementary carbon source, which has a mass concentration that is preferably 3.1-3.34 times, more preferably 3.33 times a total concentration of NO;™ and NO» in the AOP treated-effluent. In a specific example of the present disclosure, the mass concentration of the methanol is 3.1-3.34 times a total concentration of NO3° and NO: in an influent of the secondary anoxic tank. In the present disclosure, if the methanol supplement is insufficient, the NO:-N cannot be completely denitrified, and if it is excessive, it will increase the COD, making the subsequent treatment more difficult. In a specific example of the present disclosure, when the total concentration of NOs” and NO» in the AOP treated-eftluent is 130-250 mg/L, 0.403-0.85 kg of methanol is added for 1 m° of wastewater during the secondary anoxic denitrification. The present disclosure uses methanol as a carbon source to rapidly denitrify and convert NO:° and NO: into Nz, thereby achieving the purpose of removing

-13- NO: and NO".

[70] After obtaining the secondary anoxic treated-effluent, the present disclosure subjects the secondary anoxic treated-effluent to a secondary oxic treatment to obtain an effluent. In the present disclosure, the DO in the secondary oxic treatment is preferably 3 mg/L, more preferably 4-5 mg/L. In the present disclosure, the secondary oxic treatment is conducted for preferably 7-10 h, more preferably 8-9 h. The present disclosure removes the remaining COD through the secondary oxic treatment.

[71] In the present disclosure, the secondary oxic treatment is preferably conducted in a secondary oxic tank. The present disclosure has no special requirement on the specific structure of the secondary oxic tank, and an oxic tank well known to those skilled in the art may be used.

[72] In the present disclosure, the secondary oxic treatment is preferably conducted in the presence of oxic AS. In the present disclosure, the oxic AS is preferably obtained by oxic culture acclimation of AS, and bacteria added in the culture acclimation preferably come from oxic AS sludge in a municipal sewage treatment plant, and specifically preferably include a COD degradation bacteria, nitrifying bacteria and denitrifying bacteria. In the present disclosure, a mass of the oxic AS is preferably 6-12 mg/L, more preferably 6.7-8.8 mg/L.

[73] In the present disclosure, the secondary oxic treatment is preferably conducted in the presence of an elastic filler to immobilize the weak nitrifying bacteria and increase the concentration in the entire biochemical reaction tank. In the present disclosure, the elastic filler is preferably a composite filamentary material. The elastic filler has a diameter of preferably 55-80 mm, a tensile strength of preferably > 2800 N and an SSA of preferably 4000-5000 m?/m5. After a biofilm is formed, a maximum sludge amount on the elastic filler is preferably 10-15 g/L, and a maximum loading rate of BOD is preferably 0.5-1.5 kg/m’ed. In the present disclosure, the elastic filler is preferably 30- 60% of a reactor volume.

[74] The present disclosure preferably further includes: subject, after the secondary oxic treatment, the secondary oxic treated-effluent to a sedimentation treatment obtain an effluent. In the present disclosure, the sedimentation treatment is preferably conducted in a secondary sedimentation tank. The present disclosure has no special requirement on the specific structure of the secondary sedimentation tank, and a secondary sedimentation tank well known to those skilled in the art may be used. In the present disclosure, the sedimentation treatment is preferably conducted by mixing the

-14- obtained secondary oxic treated-effluent with polyaluminum chloride (PAC). In the present disclosure, a concentration of the PAC is preferably 20 ppm.

[75] Inthe present disclosure, the COD in the effluent is preferably 20-50 mg/L, more preferably 26-42 .4 mg/L. The NHs-N is preferably 0.24-4.8 mg/L, more preferably 1.89-

4.44 mg/L. The TN is preferably 2.4-14.5 mg/L, more preferably 2.4-7.67 mg/L. The TP is preferably 0.25-0.48 mg/L, more preferably 0.43-0.48 mg/L. The chroma is preferably 5-20, more preferably 7-11. The SS is preferably 0.5-10 mg/L, more preferably 7-9 mg/L.

[76] The technical solutions in the present disclosure are clearly and completely described below with reference to the examples of the present disclosure. It is clear that the described examples are merely a part, rather than all of the examples of the present disclosure. All other examples obtained by a person of ordinary skill in the art based on the examples of the present disclosure without creative efforts should fall within the protection scope of the present disclosure.

[77] Example l

[78] Waste vegetable leaves were treated according to a flowchart shown in FIG. 1. Step A: A vegetable-squeezed waste liquid was subjected to a sedimentation treatment. The vegetable-squeezed waste liquid was obtained by crushing the waste vegetable leaves, squeezing and separating. The vegetable-squeezed waste liquid was sequentially mixed with 2200 ppm of PFS and 15 ppm of PAM. Then the vegetable-squeezed waste liquid was sent into a sedimentation tank for sedimentation separation. Changes of pollution factors in the wastewater after Step A are shown in Table 1:

[79] _ Table 1 Changes of pollution factors in wastewater after Step A Step A Pollution factors and concentrations tomtom con TR Tm ss cms squeezed waste 12488mg/L | 957mg/L | 888mg/L | 2975mg/L | 5400mg/L 450 liquid squeezed filtrate

[80] It can be seen from Table 1 that after Step A, most of the SS in the vegetable- squeezed waste liquid were removed, and a TP removal rate was over 99.5%.

[81] Step B: Anaerobic treatment. The vegetable-squeezed filtrate obtained in Step A was sent to an anaerobic reactor filled with anaerobic granular sludge obtained by culture acclimation. The anaerobic granular sludge was 30% of a total liquid volume of the reactor. The treatment was maintained for 40 h. Changes of the pollution factors after

-15- Step B are shown in Table 2:

[82] Table 2 Changes of pollution factors in wastewater after Step B Step B Pollution factors and concentrations

[83] It can be seen from Table 2 that after Step B, a COD removal rate reached

68.87%, the NHs-N increased by 13.79%, and the TN increased by 3.6%. In Step B, anaerobic bacteria were used to remove the COD under an anaerobic condition, and NH:-N conversion bacteria were used to anaerobically hydrolyze organic nitrogen into low-molecular-weight inorganic nitrogen and finally into HN:.

[84] Step C: Primary anoxic denitrification. The anaerobic treated-effluent of Step B was mixed with refluxed water (which was 300% of the effluent in Step B) from Step D as an influent to be sent to a primary anoxic tank for a primary anoxic treatment. The primary anoxic tank was filled with commercially available anoxic denitrification granular sludge, which was 20% of a total liquid volume of the primary anoxic tank. The treatment was maintained for 12 h. Changes of the pollution factors after Step C are shown in Table 3:

[85] Table 3 Changes of pollution factors in wastewater after Step C

[86] It can be seen from Table 3 that after Step C, the COD removal rate reached

39.69%, the NHs-N increased by 5.38%, a TN removal rate reached 27.32%, and a NO:- N removal rate was close to 100%. In Step C, denitrifying bacteria were used to consume COD under an anoxic condition so as to denitrify and remove NO: and NO: at a denitrification rate of 10.83 mg NO*-N/Leh.

[87] Step D: Primary oxic treatment. The effluent of Step C entered a primary oxic tank, which was filled with oxic nitrification sludge obtained by culture acclimation. The oxic nitrification sludge had a concentration of 8.5 g/L, and the treatment was maintained for 13 h. After blast aeration, DO in the primary oxic tank was 3-6 mg/L. Changes of the pollution factors in the wastewater after Step D are shown in Table 4:

-16-

[88] Table 4 Changes of pollution factors in wastewater after Step D Step D Pollution factors and concentrations influent/efflue a t COD | NHN | TN TP ss | Chrom | NO: and n a NO: Primary anoxic o 23 J treated 670mg/ 274mg/L 234mg/ mg/L 22mg/ 354 0.00mg/

L L L L effluent Primary oxic - o A troated- 254mg/ | 4.38mg/ | 130mg/ | 2.22mg/ | 20mg/ 120 175mg/L

L L L L L effluent

[89] It can be seen from Table 4 that after Step D, the COD removal rate reached

62.01% and the NH3-N removal rate reached 98.40%. Under the oxic condition in Step D, nitrifying bacteria were used to convert HN; into NO: or NO’, and heterotrophic bacteria were used to remove COD. The primary oxic tank was filled with an elastic filler, in which an anoxic zone was formed for denitrification to remove NO: and NO». The TN removal rate in the primary oxic tank was 44.44%.

[90] In Step D, part of the effluent, which was 300% of the effluent of Step B, was refluxed for the treatment in Step C, and the remaining water was subjected to a treatment in Step E.

[91] Step E: AOP. The effluent of Step D entered an advanced oxidation tank. Hydrogen peroxide with a mass concentration that was 2.0 times the COD in the influent was firstly added and stirred evenly. Then ferrous sulfate was added, and the stirring continued for 6 h. The mass of the ferrous sulfate was calculated according to a molar ratio of the hydrogen peroxide to Fe’, that is, 1:0.8. After the reaction, an obtained mixed liquid entered a sedimentation tank. A turbid liquid at the bottom of the sedimentation tank was filtered to obtain a filtrate and a filter residue. The filtrate was mixed with a supernatant liquid of the sedimentation tank for a treatment in Step F, and the filter residue was treated as an iron residue. Changes of the pollution factors in the wastewater after Step E are shown in Table 5:

[92] Table 5 Changes of pollution factors in wastewater after Step E Pollution factors and concentrations Step E influent/efflue Chrom NO; nt COD NHs-N TN TP SS and a NO» Primary oxic J 42 a 2 treated- 254mg/L 438mg/ | 130mg/ | 2.22mg/ | 20mg/ 120 175mg/

L L L L L effluent AOP-treated | 49.50mg/ | 438mg/ | 130mg/ | 2.22mg/ | 10mg/ 10 175mg/ effluent L L L L L L

[93] It can be seen from Table 5 that after Step E, the COD removal rate reached

-17-

80.51% and the chroma decreased to 10. In Step D, the hydrogen peroxide reacted with Fe?" to produce OH (hydroxyl radicals). This destroys high-molecular-weight organic substances such as cellulose and lignin that are difficult for microorganisms to degrade into low-molecular-weight organic substances that are easily utilized by microorganisms, and realizes decolorization.

[94] Step F: Secondary anoxic denitrification. The AOP treated-effluent of Step E entered a secondary anoxic tank, which was filled with anoxic AS obtained by culture acclimation. The anoxic AS had a concentration of 9.5 g/L, and the treatment was maintained for 12 h. Methanol was added as a carbon source required for the secondary anoxic denitrification, which had a mass concentration that was 3.33 times a total concentration of NOs™ and NO" in the influent of the secondary anoxic tank in Step F. Changes of pollution factors after Step F are shown in Table 6(COD significantly increased because of the addition of methanol):

[95] Table 6 Changes of pollution factors in wastewater after Step F NO- influent L L L L L Sor ee effluent

[96] It can be seen from Table 6 that after Step F, the COD removal rate reached

83.81%, the NH:-N increased by 77.39%, the TN removal rate reached 92.3%, and the NOs" and NO; removal rate was close to 100%. In Step F, denitrifying bacteria were used to consume the carbon source (methanol) under an anoxic condition so as to denitrify and remove NOs” and NO’, at a denitrification rate of 14.58 mg NO*-N/Leh.

[97] Step G: Secondary oxic treatment. The effluent of Step F entered a secondary oxic tank, which was filled with AS with a concentration of 8.8 g/L, and the treatment was maintained for 8 h. After blast aeration, the DO in the secondary oxic tank was greater than 3 mg/L. After Step G, an obtained secondary oxic treated-effluent entered a secondary sedimentation tank for a sedimentation treatment. Changes of the pollution factors in the wastewater after Step G are shown in Table 7: 98] Table 7 Changes of pollution factors in wastewater after Step G Step G

-18-

NDL NO»

SE effluent

[99] It can be seen from Table 7 that after Step G, the COD removal rate reached

69.53%, the NHz-N removal rate reached 70.14%, the TN removal rate reached 41.15%, and the TP removal rate reached 80.63%. Under the oxic condition in Step G, heterotrophic bacteria were used to remove COD, and nitrifying bacteria were used to convert HN; into NO: or NO». The secondary oxic tank was filled with an elastic filler, in which an anoxic zone was formed for denitrification to remove NO: and NO». The effluent in Step G met the Level 1-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB 18918-2002).

[100] Example 2

[101] Waste vegetable leaves were treated according to a flowchart shown in FIG. 1. Step A: A vegetable-squeezed waste liquid was subjected to a sedimentation treatment. The vegetable-squeezed waste liquid was obtained by crushing the waste vegetable leaves, squeezing and separating. The vegetable-squeezed waste liquid was sequentially mixed with 1500 ppm of PFS and 10 ppm of PAM. Then the vegetable-squeezed waste liquid was sent into a sedimentation tank for sedimentation separation. Changes of pollution factors in the wastewater after Step A are shown in Table 8: 102] Table 8 Changes of pollution factors in wastewater after Step A Step A Pollution factors and concentrations nih | on Vegetable-squeezed 641mg/L | 550mg/L 28mg/L filtrate

[103] It can be seen from Table 8 that after Step A, most of the SS in the vegetable- squeezed waste liquid were removed, and a TP removal rate was over 92.96%.

[104] Step B: Anaerobic treatment. The vegetable-squeezed filtrate obtained in Step A was sent to an anaerobic reactor filled with anaerobic granular sludge obtained by culture acclimation. The anaerobic granular sludge was 30% of a total liquid volume of the reactor. The treatment was maintained for 38 h. Changes of the pollution factors after Step B are shown in Table 9:

[105] Table 9 Changes of pollution factors in wastewater after Step B

-19-

[106] It can be seen from Table 9 that after Step B, a COD removal rate reached

64.82%, the NH3-N increased by 5.30%, and the TN increased by 11.27%. In Step B, anaerobic bacteria were used to remove the COD under an anaerobic condition, and NH:-N conversion bacteria were used to anaerobically hydrolyze organic nitrogen into low-molecular-weight inorganic nitrogen and finally into HN:.

[107] Step C: Primary anoxic denitrification. The anaerobic treated-effluent of Step B was mixed with refluxed water (which was 300% of the effluent in Step B) from Step D as an influent to be sent to a primary anoxic tank for a primary anoxic treatment. The primary anoxic tank was filled with commercially available anoxic denitrification granular sludge, which was 20% of a total liquid volume of the anoxic denitrification tank. The treatment was maintained for 10 h. Changes of the pollution factors after Step C are shown in Table 10:

[108] Table 10 Changes of pollution factors in wastewater after Step C 1 70 1 995 ) 5 SOZ Primary anoxic | 467mg/ | 174mg/ | 183mg/ | 397mg/ | 29mg/ A 0.00mg/

[109] It can be seen from Table 10 that after Step C, the COD removal rate reached

53.06%, the NH3-N increased by 8.07%, a TN removal rate reached 26.29%, and a NO:- N removal rate was close to 100%. In Step C, denitrifying bacteria were used to consume the easily degradable COD under an anoxic condition so as to denitrify and remove NO: and NO», at a denitrification rate of 9.5mg NO*-N/Lsh.

[110] Step D: Primary oxic treatment. The effluent of Step C entered a primary oxic tank, which was filled with oxic nitrification sludge obtained by culture acclimation. The oxic nitrification sludge had a concentration of 8.8 g/L, and the treatment was maintained for 12 h. After blast aeration, DO in the primary oxic tank was 3-6 mg/L. Changes of the pollution factors in the wastewater after Step D are shown in Table 11:

220-

L L L L effluent Primary oxic 3 o a treated- 276mg/ | 2.20mg/ | 109mg/ | 7.3lmg/ | 27mg/ 132 136mg/L

L L L L L effluent

[112] It can be seen from Table 11 that after Step D, the COD removal rate reached

40.89% and the NHs;-N removal rate reached 98.16%. Under the oxic condition, nitrifying bacteria were used to convert HN3 into NO: or NO’, and heterotrophic bacteria were used to remove COD.

[113] In Step D, part of the effluent, which was 300% of the effluent of Step B, was refluxed for the treatment in Step C, and the remaining water was subjected to a treatment in Step E.

[114] Step E: AOP. The effluent of Step D entered an advanced oxidation tank. Hydrogen peroxide with a mass concentration that was 1.85 times the COD in the influent was firstly added and stirred evenly. Then ferrous sulfate was added, and the stirring continued for 5 h. The mass of the ferrous sulfate was calculated according to a molar ratio of the hydrogen peroxide to Fe?’, that is, 1:0.8. After the reaction, an obtained mixed liquid entered a sedimentation tank. A turbid liquid at the bottom of the sedimentation tank was filtered to obtain a filtrate and a filter residue. The filtrate was mixed with a supernatant liquid of the sedimentation tank for a treatment in Step F, and the filter residue was treated as an iron residue. Changes of the pollution factors in the wastewater after Step E are shown in Table 12:

[115] Table 12 Changes of pollution factors in wastewater after Step E Pollution factors and concentrations Step E 7 influent/efflue Chrom NO; nt COD NH:-N TN TP SS and a NO» Primary oxic ; 22 G 3 3 treated- 276mg/L 2.20mg/ | 109mg/ | 7.3lmg/ | 27mg/ 132 136mg/

L L L L L effluent AOP-treated | 60.60mg/ | 2.20mg/ | 109mg/ | 7.31mg/ | 13mg/ 13 136mg/ effluent L L L L L > L

[116] It can be seen from Table 12 that after Step E, the COD removal rate reached

78.04% and the chroma decreased to 13. In Step D, the hydrogen peroxide reacted with Fe?" to produce OH (hydroxyl radicals). This destroys high-molecular-weight organic

21- substances such as cellulose and lignin that are difficult for microorganisms to degrade into low-molecular-weight organic substances that are easily utilized by microorganisms, and realizes decolorization.

[117] Step F: Secondary anoxic denitrification. The AOP treated-effluent of Step E entered a secondary anoxic tank, which was filled with anoxic AS obtained by culture acclimation. The anoxic AS had a concentration of 9.5 g/L, and the treatment was maintained for 10 h. Methanol was added as a carbon source required for the secondary anoxic denitrification, which had a mass concentration that was 3.33 times a total concentration of NO: and NO" in the influent of the secondary anoxic tank in Step F. Changes of pollution factors after Step F are shown in Table 13:

[118] Table 13 Changes of pollution factors in wastewater after Step F Pollution factors and concentrations Step F 7 influent/efflue Chrom NO: nt COD NH;-N TN TP SS and a NOy Secondary A anoxic treated- 7209 | 222mg ggg ng Bm saga . L L L L influent Secondary | 10900 | ILlmg/ | 163mg | 1.02me/ | l4mg/ | 0.00mg/ anoxic treated- 11

L L L L L L effluent

[119] It can be seen from Table 13 that after Step F, the COD removal rate reached

77.07%, the NHs-N increased, the TN removal rate reached 85.04%, and the NO: and NO: removal rate was close to 100%. In Step F, denitrifying bacteria were used to consume the carbon source (methanol) under an anoxic condition so as to denitrify and remove NO: and NO, at a denitrification rate of 11.33mg NO*-N/Leh.

[120] Step G: Secondary oxic treatment. The effluent of Step F entered a secondary oxic tank, which was filled with AS with a concentration of 8.69/L, and the treatment was maintained for 8 h. After blast aeration, the DO in the secondary oxic tank was 4-

4.5 mg/L. After Step G, an obtained secondary oxic treated-effluent entered a secondary sedimentation tank for a sedimentation treatment. Changes of the pollution factors in the wastewater after Step G are shown in Table 14:

[121] Table 14 Changes of pollution factors in wastewater after Step G Pollution factors and concentrations Step G - influent/efflue Chrom NO; nt COD | NHN | TN TP SS and a NOy Secondary | 177ma/ 1llmg/ | 163me/ | 102mg/ | l4mg/ | 0.00mg/ anoxic treated- 11

L L L L L L effluent

222.

[122] It can be seen from Table 14 that after Step G, the COD removal rate reached

76.04%, the NH;-N removal rate reached 82.97%, the TN removal rate reached 65.95%, and the TP removal rate reached 53.29%. The effluent in Step G met the Level 1-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment 53 Plant" (GB18918-2002).

[123] Example 3

[124] Waste vegetable leaves were treated according to a flowchart shown in FIG. 1. Step A: A vegetable-squeezed waste liquid was subjected to a sedimentation treatment. The vegetable-squeezed waste liquid was obtained by crushing the waste vegetable leaves, squeezing and separating. The vegetable-squeezed waste liquid was sequentially mixed with 2500 ppm of PFS and 20 ppm of PAM. Then the vegetable-squeezed waste liquid was sent into a sedimentation tank for sedimentation separation. Changes of pollution factors in the wastewater after Step A are shown in Table 15:

[125] Table 15 Changes of pollution factors in wastewater after Step A Vegetable- liquid

[126] It can be seen from Table 15 that after Step A, most of the SS in the vegetable- squeezed waste liquid were removed, and a TP removal rate was over 99%.

[127] Step B: Anaerobic treatment. The vegetable-squeezed filtrate obtained in Step A was sent to an anaerobic reactor filled with anaerobic granular sludge obtained by culture acclimation. The anaerobic granular sludge was 30% of a total liquid volume of the reactor. The treatment was maintained for 40 h. Changes of the pollution factors after Step B are shown in Table 16:

[128] Table 16 Changes of pollution factors in wastewater after Step B

23-

[129] It can be seen from Table 16 that after Step B, a COD removal rate reached

64.97%, the NHz-N increased by 7.89%, and the TN increased by 38.94%. In Step B, anaerobic bacteria were used to remove the COD under an anaerobic condition, and NH:-N conversion bacteria were used to anaerobically hydrolyze organic nitrogen into low-molecular-weight inorganic nitrogen and finally into HN:.

[130] Step C: Primary anoxic denitrification. The anaerobic treated-effluent of Step B was mixed with refluxed water (which was 400% of the effluent in Step B) from Step D as an influent to be sent to a primary anoxic tank for a primary anoxic treatment. The primary anoxic tank was filled with commercially available anoxic denitrification granular sludge, which was 20% of a total liquid volume of the anoxic denitrification tank. The treatment was maintained for 12 h. Changes of the pollution factors after Step C are shown in Table 17:

[131] Table 17 Changes of pollution factors in wastewater after Step C Step C

DE Fp pe

[132] It can be seen from Table 17 that after Step C, the COD removal rate reached

42.53%, the NH3-N increased by 0.42%, a TN removal rate reached 27.21%, and a NOs- N removal rate was close to 100%. In Step C, denitrifying bacteria were used to consume COD under an anoxic condition so as to denitrify and remove NOs” and NO: at a denitrification rate of 11.25mg NO*-N/Leh.

[133] Step D: Primary oxic treatment. The effluent of Step C entered a primary oxic tank, which was filled with oxic nitrification sludge obtained by culture acclimation. The oxic nitrification sludge had a concentration of 8.5 g/L, and the treatment was maintained for 12 h. After blast aeration, DO in the primary oxic tank was 3-6 mg/L. Changes of the pollution factors in the wastewater after Step D are shown in Table 18:

[134] Table 18 Changes of pollution factors in wastewater after Step D Step D Pollution factors and concentrations 5

24.

[135] It can be seen from Table 18 that after Step D, the COD removal rate reached

61.93% and the NH3-N removal rate reached 98.73%. Under the oxic condition in Step D, nitrifying bacteria were used to convert HN; into NO: or NO», and heterotrophic bacteria were used to remove COD. The primary oxic tank was filled with an elastic filler, in which an anoxic zone was formed for denitrification to remove NO: and NOs".

The TN removal rate in the primary oxic tank was 42.34%.

[136] In Step D, part of the effluent, which was 400% of the effluent of Step B, was refluxed for the treatment in Step C, and the remaining water was subjected to a treatment in Step E.

[137] Step E: AOP. The effluent of Step D entered an advanced oxidation tank. Hydrogen peroxide with a mass concentration that was 2.0 times the COD in the influent was firstly added and stirred evenly. Then ferrous sulfate was added, and the stirring continued for 6 h. Since the pH would decrease in this step, it was not adjusted. The mass of the ferrous sulfate was calculated according to a molar ratio of the hydrogen peroxide to Fe?*, that is, 1:0.8. After the reaction, an obtained mixed liquid entered a sedimentation tank. A turbid liquid at the bottom of the sedimentation tank was filtered to obtain a filtrate and a filter residue. The filtrate was mixed with a supernatant liquid of the sedimentation tank for a treatment in Step F, and the filter residue was treated as an iron residue. Changes of the pollution factors in the wastewater after Step E are shown in Table 19:

[138] Table 19 Changes of pollution factors in wastewater after Step E NOs effluent L L L L L L

[139] It can be seen from Table 19 that after Step E, the COD removal rate reached

83.4% and the chroma decreased to 15. In Step D, the hydrogen peroxide reacted with Fe?’ to produce OH (hydroxyl radicals). This destroys high-molecular-weight organic substances such as cellulose and lignin that are difficult for microorganisms to degrade into low-molecular-weight organic substances that are easily utilized by microorganisms, and realizes decolorization.

[140] Step F: Secondary anoxic denitrification. The AOP treated-effluent of Step E

25- entered a secondary anoxic tank, which was filled with anoxic AS obtained by culture acclimation. The anoxic AS had a concentration of 8.5 g/L, and the treatment was maintained for 12 h. Methanol was added as a carbon source required for the secondary anoxic denitrification, which had a mass concentration that was 3.33 times a total concentration of NO: and NO’ in the influent of the secondary anoxic tank in Step F. Changes of pollution factors after Step F are shown in Table 20:

[141] Table 20 Changes of pollution factors in wastewater after Step F Pollution factors and concentrations Step F influent/efflue Chrom NO; nt COD NHs;-N TN TP SS and a NO» Secondary + 2 2 2 anoxic treated- Sims mg 128mg/L | 2mg/L om 15 | 168mg/L influent Secondary anoxic treated- | 97mg/L 12.0mg/ | 18.89mg/ | 0.7mg/ | l6mg/ 14 0.00mg/

L L L L L effluent

[142] It can be seen from Table 20 that after Step F, the COD removal rate reached

86.86%, the NH3-N increased by 3.93 times, the TN removal rate reached 85.24%, and the NOs; and NO; removal rate was close to 100%. In Step F, denitrifying bacteria were used to consume the carbon source (methanol) under an anoxic condition so as to denitrify and remove NO: and NO», at a denitrification rate of 14.58 mg NO*-N/Lsh.

[143] Step G: Secondary oxic treatment. The effluent of Step F entered a secondary oxic tank, which was filled with AS with a concentration of 6.7 g/L, and the treatment was maintained for 8 h. After blast aeration, the DO in the secondary oxic tank was greater than 3 mg/L. After Step G, an obtained secondary oxic treated-effluent entered a secondary sedimentation tank for a sedimentation treatment. Changes of the pollution factors in the wastewater after Step G are shown in Table 21:

[144] Table 21 Changes of pollution factors in wastewater after Step G Pollution factors and concentrations Step G - influent/efflue Chrom NO: nt COD | NH-N | TN TP SS and a NO» Secondary ; 2 anoxic treated- 97mg/ | 12.0mg/ | 18.89mg/ 0.7mg/L lómg/ 14 0.00mg/

L L L L L effluent Effluent 26mg/ | 4.44mg/ 7.67mg/L 0.48mg/ Omg/L 1 0.00mg/

L L L L

[145] It can be seen from Table 21 that after Step G, the COD removal rate reached

73.19%, the NHs-N removal rate reached 63%, the TN removal rate reached 59.39%,

6- and the TP removal rate reached 58.26%. The effluent in Step G met the Level 1-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB18918-2002).

[146] Comparative Example

[147] Taking an example of CN111807609A as a comparative example, the treatment results of a biogas slurry by a vegetable leaf/fruit and vegetable waste liquid in this comparative example are shown in Table 22:

[148] Table 22 Treatment results of biogas slurry in the comparative example Vegetable liquid, biogas slurry

[149] It can be seen in Table 22 that after the treatment by the method of CNI111807609A, the COD and chroma of the effluent did not meet the Level 1-A criteria of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB18918-2002).

[150] The present disclosure conducts the AOP after the primary oxic treatment to convert the difficult-to-degrade high-molecular-weight substances such as cellulose and lignin into easily degradable low-molecular-weight substances and realize effective decolorization. Because lutein is decomposed, the final effluent does not turn yellow, laying a solid foundation for the COD and chroma to meet the criteria. The present disclosure ensures the sable standard quality of the effluent of different vegetable varieties at different temperatures for a long time (180 d).

[151] The above described are merely preferred implementations of the present disclosure. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, but such improvements and modifications shall also be deemed as falling within the protection scope of the present disclosure.

Claims

-27- Conclusies L Werkwijze voor het behandelen van een uit planten geperste afvalvloeistof, waarbij de werkwijze de volgende stappen omvat: (1) het mengen van een uit planten geperste afvalvloeistof met polymeer ijzersulfaat (PFS) en kationisch polyacrylamide (PAM) voor een sedimentatiebehandeling om een uit planten geperst filtraat te verkrijgen; (2) het onderwerpen van het uit planten geperste filtraat aan een anaerobe behandeling om een anaeroob behandeld effluent te verkrijgen; (3) het onderwerpen van het anaeroob behandelde effluent aan een primaire anoxische denitrificatiebehandeling om een primair anoxisch behandeld effluent te verkrijgen; (4) het onderwerpen van het primaire anoxisch behandelde effluent aan een primaire aerobe behandeling om een primair aeroob behandeld effluent te verkrijgen; (5) het mengen van het primaire aeroob behandelde effluent met waterstofperoxide en ijzersulfaat voor een geavanceerd oxidatieproces (AOP) om een AOP-behandeld effluent te verkrijgen; (6) het onderwerpen van het AOP-behandelde effluent aan een secundaire anoxische denitrificatiebehandeling om een secundair anoxisch behandeld effluent te verkrijgen; en (7) het onderwerpen van het secundaire anoxisch behandelde effluent aan een secundaire aerobe behandeling om een effluent te verkrijgen.Claims L Method for treating a plant pressed waste liquor, the method comprising the steps of: (1) mixing a plant pressed waste liquor with polymeric ferrous sulfate (PFS) and cationic polyacrylamide (PAM) for a sedimentation treatment to obtain a filtrate pressed from plants; (2) subjecting the filtrate extruded from plants to an anaerobic treatment to obtain an anaerobically treated effluent; (3) subjecting the anaerobically treated effluent to a primary anoxic denitrification treatment to obtain a primary anoxic treated effluent; (4) subjecting the primary anoxically treated effluent to a primary aerobic treatment to obtain a primary aerobically treated effluent; (5) mixing the primary aerobically treated effluent with hydrogen peroxide and ferrous sulfate for an advanced oxidation process (AOP) to obtain an AOP treated effluent; (6) subjecting the AOP-treated effluent to a secondary anoxic denitrification treatment to obtain a secondary anoxic treated effluent; and (7) subjecting the secondary anoxically treated effluent to a secondary aerobic treatment to obtain an effluent.

2. Behandelingswerkwijze volgens conclusie 1, waarbij in stap (1) chemischzuurstofbehoefte (COD), ammoniakstikstof (NH:-N), totaal stikstof (TN) en totaal fosfor (TP) in de uit planten geperste afvalvloeistof respectievelijk 5000 — 20000 mg/L, 400 — 1400 mg/L, 450 — 1700 mg/L en 1000 — 3500 mg/L zijn.The treatment method according to claim 1, wherein in step (1) chemical oxygen demand (COD), ammonia nitrogen (NH:-N), total nitrogen (TN) and total phosphorus (TP) in the plant expended waste liquid 5000 - 20000 mg/L, respectively , 400-1400 mg/L, 450-1700 mg/L and 1000-3500 mg/L.

3. Behandelingswerkwijze volgens conclusie 1, waarbij in stap (2) de COD in het anaeroob behandelde effluent 3000 — 5500 mg/L is.The treatment method according to claim 1, wherein in step (2) the COD in the anaerobically treated effluent is 3000-5500 mg/L.

4. Behandelingswerkwijze volgens conclusie 1, waarbij in stap (3) een totale concentratie van nitraat (NO:°) en nitriet (NO?) in het primaire anoxisch behandeldeThe treatment method according to claim 1, wherein in step (3) a total concentration of nitrate (NO:°) and nitrite (NO?) in the primary anoxically treated

-08 - effluent minder dan 10 mg/L is.-08 - effluent is less than 10 mg/L.

5. Behandelingswerkwijze volgens conclusie 1, waarbij in stap (4) opgelost zuurstof (DO) in de primaire aerobe behandeling 3 — 6 mg/L is.The treatment method according to claim 1, wherein in step (4) dissolved oxygen (DO) in the primary aerobic treatment is 3-6 mg/L.

6. Behandelingswerkwijze volgens conclusie 1, waarbij in stap (4) een deel van het primaire aeroob behandelde effluent, wat 300 — 400% van totaal anaeroob behandeld effluent is, teruggevoerd wordt voor de primaire anoxisch denitrificatiebehandeling in stap (3).The treatment method of claim 1, wherein in step (4) a portion of the primary aerobically treated effluent, which is 300-400% of total anaerobically treated effluent, is recycled for the primary anoxic denitrification treatment in step (3).

7. Behandelingswerkwijze volgens conclusie 1, waarbij in stap (5) de waterstofperoxide een massaconcentratie heeft die 1,85 — 2,0 maal de COD van het primaire aeroob behandelde effluent is, en een molverhouding van het ijzersulfaat tot de waterstofperoxide 0,8:1 is.The treatment method of claim 1, wherein in step (5) the hydrogen peroxide has a mass concentration which is 1.85 - 2.0 times the COD of the primary aerobically treated effluent, and a molar ratio of the ferrous sulfate to the hydrogen peroxide is 0.8: 1.

8. Behandelingswerkwijze volgens conclusie 1, waarbij in stap (6) methanol toegevoegd wordt in de secundaire anoxische denitrificatiebehandeling als een supplementaire koolstofbron, die een massaconcentratie heeft die 3,1 — 3,34 maal een totale concentratie van NOs” en NO: in het AOP-behandelde effluent is.The treatment method according to claim 1, wherein in step (6), methanol is added in the secondary anoxic denitrification treatment as a supplemental carbon source, which has a mass concentration that is 3.1 - 3.34 times a total concentration of NOs" and NO: in the AOP-treated effluent.

9. Behandelingswerkwijze volgens conclusie 1, waarbij de behandelingswerkwijze verder het volgende omvat: het, na de secundaire aerobe behandeling, onderwerpen van het secundaire aeroob behandelde effluent aan een sedimentatiebehandeling om een effluent te verkrijgen.The treatment method of claim 1, wherein the treatment method further comprises: after the secondary aerobic treatment, subjecting the secondary aerobically treated effluent to a sedimentation treatment to obtain an effluent.

10. Behandelingswerkwijze volgens conclusie 1 of 9, waarbij de COD, NHs-N, TN, TP, chroma en gesuspendeerde vaste stoffen (SS) in het effluent respectievelijk 20 — 50 mg/L, 0,24 4,8 mg/l, 2,4 — 14,5 mg/L, 0,25 — 0,48 mg/L, 5 - 20 en 0,5 — 10 mg/L zijn.The treatment method according to claim 1 or 9, wherein the COD, NH 3 -N, TN, TP, chroma and suspended solids (SS) in the effluent are 20-50 mg/L, 0.24 4.8 mg/L, respectively. 2.4 - 14.5 mg/L, 0.25 - 0.48 mg/L, 5 - 20 and 0.5 - 10 mg/L.