CN111892238A - A combined emergency treatment method for black and odorous water with forward osmosis-coagulation-anoxic hydrolysis - Google Patents

Abstract

The invention discloses a black odorous water forward osmosis-coagulation-anoxic hydrolysis combined emergency treatment method, wherein black odorous water is subjected to three-stage concentration treatment by step forward osmosis, and the step concentration ensures that the single-stage flux is low, the membrane pollution degree is light, and the continuous operation can be realized; the drawing liquid diluted in the forward osmosis process is subjected to re-concentration and recycling by adopting reverse osmosis, so that secondary pollution can be avoided; the concentrated black and odorous water volume is greatly reduced, the concentrations of organic matters, iron, manganese and the like are obviously improved, the treatment capacity is effectively reduced, and the efficiency is improved; iron, manganese, suspended matters and colloidal substances in water are removed through coagulating sedimentation in sequence, anoxic hydrolysis is performed to improve biodegradability of concentrated water, and effluent finally enters a sewage plant, so that the defect that pollutants stay in a water body in conventional methods such as aeration, in-situ coagulant adding and the like is overcome.

Description

A combined emergency treatment method for black and odorous water with forward osmosis-coagulation-anoxic hydrolysis

technical field

The invention belongs to the technical field of environmental engineering, and in particular relates to a combined emergency treatment method of black and odorous water with forward osmosis-coagulation-anoxic hydrolysis.

Background technique

Due to the discharge of industrial wastewater and domestic sewage, the ecosystems of urban rivers, lakes and other surface water bodies are facing major challenges. Black and odor has become a common problem in many cities in my country. The formation mechanism of black odor is that when the water body suffers from serious organic pollution, the aerobic decomposition of organic matter makes the oxygen consumption rate in the water body greater than the reoxygenation rate, resulting in anoxic water body, resulting in incomplete degradation of organic matter, slowing down, and anaerobic biodegradation process. Hydrogen sulfide, amine, ammonia, mercaptan and other odorous substances, and at the same time form black substances such as FeS, MnS, etc., causing the water body to become black and odorous.

At present, the treatment methods for black and odorous water include physical methods, chemical methods and biological methods. Among them, the physical method includes water conservancy projects such as water transfer and dredging, as well as mechanical algae removal, water diluting and dilution, etc. The main problem is to treat the symptoms rather than the root cause, and cannot fundamentally solve the problem of black and odor; chemical methods include adding chemical reagents to remove algae, adding iron Salt and phosphorus removal, etc., but the dosage of chemical reagents is large and the cost is high; biological methods are widely used, and the in-situ ecological restoration technologies of polluted rivers include aeration and oxygenation, microbial restoration, protozoa restoration, phytoremediation and constructed wetlands The biological method is economical and practical, but the effect is slow, and the plants are obviously affected by the season. "Black and odorous water A/O forward osmosis treatment system and treatment process" published by patent 201611166004.2 applies forward osmosis technology to black and odorous water, but its pioneer pretreatment technologies include ozone oxidation, air stripping, hydrolysis and acidification, aerobic biological flow Combination technologies such as chemical bed, the process is complex, and the organic load of black and odorous water is lower than that of sewage, so it is difficult to directly use biochemical engineering treatment. How to give full play to the advantages of forward osmosis technology plays a vital role in rationally applying it to the treatment of black and odorous water.

SUMMARY OF THE INVENTION

The present invention proposes a combined emergency treatment method for black and odorous water with positive osmosis-coagulation-anoxic hydrolysis in order to solve the problems of large investment, slow effect, and easy repetition of the symptoms, so as to realize the emergency treatment of black and odorous water. Fast, stable, long-term goals.

To achieve the above object, the present invention provides the following technical solutions:

A forward osmosis-coagulation-anoxic hydrolysis combined emergency treatment method for black and odorous water, comprising the following steps:

1) The black and odorous water is firstly subjected to three-level concentration treatment through stepped forward osmosis. The third-level drawing liquid is osmotically diluted and sent to the second-level forward osmosis to continue the drawing operation. Finally, it is sent to the first-level forward osmosis for black and smelly water concentration, and the first-level dilution and drawing The liquid is sent to the reverse osmosis unit for concentration and returned to the three-stage forward osmosis system for recycling;

2) The black and odorous water concentrate enters the coagulation and sedimentation treatment device to remove iron, manganese and suspended solids and colloidal substances in water;

3) The black and odorous water concentrate is sent to the biofilm anoxic tank for anoxic hydrolysis to improve the biodegradability of the concentrated water and reduce the organic load. The effluent is finally discharged into the municipal sewage pipe network and sent to the sewage plant for centralized treatment.

Further, in the step 1), the concentration ratio of the primary and secondary forward osmosis is 2 times, the concentration ratio of the tertiary forward osmosis is 3 times, and the black and odorous water is reduced by 12 times after the stepwise concentration, and the concentration of the main pollutants is 2 times. It is increased by about 10 times, which is convenient for efficient processing in the next step.

Further, in the step 1), the forward osmosis drawing liquid adopts inorganic salt system drawing liquid, and the initial concentration of the third-level drawing liquid is 2M, which can ensure that the concentration of the drawing liquid reaches 0.5M when entering the first-level forward osmosis system, which is harmful to black and odorous water. Still has a good concentration effect.

Further, in the step 1), the first-stage diluted draw solution is sent to the reverse osmosis unit to be concentrated to 2M and then returned to the third-stage forward osmosis system.

Further, in the step 2), PAC is used as a coagulant, and air stirring is adopted in the mixing reaction stage to promote the oxidation precipitation of Fe ²⁺ and Mn ²⁺ .

Further, in the step 3), the anoxic tank is filled with suspended fillers, and the anoxic biofilm is used to perform anoxic hydrolysis of the black and odorous water concentrate after the film is formed, and the hydraulic retention time of the anoxic tank is 2 to 4 hours.

The present invention has the following positive effects:

The method is a physicochemical-biochemical combined emergency treatment method for black and odorous water. The single-stage flux is low and the degree of membrane fouling is light. After multiple cycles, the flux is kept at a relatively stable level, and continuous operation can be realized; ; After the black and odorous water is concentrated, Fe, Mn and other black factors are removed by coagulation, and organic pollutants are finally entered into the sewage treatment plant after anoxic hydrolysis, avoiding conventional methods such as aeration and in-situ dosing of coagulants. The disadvantage of still staying in a body of water.

Description of drawings

Fig. 1 is the flow chart of the combined emergency treatment method of black and odorous water by forward osmosis-coagulation-anoxic hydrolysis of the present invention.

Fig. 2 is the variation law of the third-stage forward osmosis flux of black and odorous water in Example 1 with the period.

Detailed ways

The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Modifications or substitutions made to the methods, steps or conditions of the present invention without departing from the spirit and essence of the present invention all belong to the scope of the present invention.

1, the black and odorous water forward osmosis-coagulation-anoxic hydrolysis combined emergency treatment method of the present invention, the process is as follows:

The black and odorous water is firstly subjected to three-stage concentration treatment through stepped forward osmosis. The concentration ratio of first-stage and second-stage forward osmosis is 2 times, and the concentration ratio of third-stage forward osmosis is 3 times. The initial concentration of the first-level drawing liquid is 2M, the third-level drawing liquid is osmotically diluted and sent to the second-level forward osmosis to continue the drawing operation, and finally sent to the first-level forward osmosis for black and odorous water concentration. The concentration of the drawing liquid entering the first-level forward osmosis system is 0.5 M, still has a good concentration effect on black and odorous water. The black and odorous water is reduced by 12 times after the cascade concentration, and the concentration of the main pollutants is increased by about 10 times. The first-stage diluted drawing liquid is sent to the reverse osmosis unit to be concentrated to 2M and then returned to the third-stage forward osmosis system.

The black and odorous water concentrate enters the coagulation and sedimentation treatment device, and PAC is used as a coagulant. In the mixing reaction stage, air stirring and mixing are used to remove iron, manganese, suspended solids and colloidal substances in water; the black and odorous water concentrate is sent to the biofilm. Anoxic tank, the anoxic tank is filled with suspended fillers, and the anoxic biofilm is used to perform anoxic hydrolysis of the black and odorous water concentrate after filming. The biodegradability is improved, the organic load is reduced, and the effluent is finally discharged into the municipal sewage pipe network and sent to the sewage treatment plant for centralized treatment.

Example 1

During the test, a black and odorous water body in Nanjing City, Jiangsu Province was used as the treatment object. The black and odorous water was first subjected to three-stage concentration treatment through stepped forward osmosis (FO), and the influent COD (chemical oxygen demand) concentration was in the range of 50.4-60mg/L Inside, NH ₄ ⁺ -N (ammonia nitrogen) is 2.0-4.2mg/L, and TP (total phosphorus, a pollutant commonly measured in sewage) is 0.26-0.29mg/L. The forward osmosis concentration ratio of the first and second stage is 2 times, and the forward osmosis concentration ratio of the third stage is 3 times. The forward osmosis drawing solution is sodium chloride solution (sodium chloride origin: Sinopharm Chemical Reagent Co., Ltd.) The initial concentration of the liquid is 2M. After osmosis and dilution, the third-level drawing liquid is sent to the second-level forward osmosis to continue the drawing operation. The first-level diluted drawing liquid is sent to the reverse osmosis unit to be concentrated to 2M and then returned to the third-level forward osmosis system. After three-stage FO concentration, the COD concentration range of black and odorous water is increased to 480-550mg/L, and the biodegradability of wastewater is low (B/C ratio is in the range of 0.22-0.28).

The black and odorous water concentrate enters the coagulation and sedimentation treatment device. In this example, PAC (polymeric alumina) is used as the coagulant, and the mixing reaction stage adopts air stirring and mixing to remove iron, manganese and suspended solids and colloidal substances in water.

The black and odorous water concentrate is then sent to the biofilm anoxic tank, and the anoxic tank is filled with spherical suspension filler (Φ100mm, origin: Yixing Jingtian Environmental Protection Technology Co., Ltd.), and the anoxic biofilm is used to treat the black and odorous water concentrate after hanging the film. For anoxic hydrolysis, the hydraulic retention time of the anoxic pool is 2 to 4 hours.

After coagulation sedimentation and anoxic hydrolysis of the black and odorous water concentrate, the COD is reduced to 390-440mg/L, the B/C ratio is increased to about 0.35, the biodegradability of the concentrated water is improved, the organic load is reduced, and other major indicators of waste water reach sewage. The comprehensive discharge standard (GB8978-1996) can be incorporated into the municipal sewage pipe network and sent to the sewage treatment plant for further treatment after the three-level discharge standard.

The flux monitoring of the forward osmosis process in this example shows that the black and odorous water membrane of the forward osmosis treatment has a low degree of pollution, and only a simple physical cleaning method is used in each concentration cycle. It can be seen from Figure 2 that the first operating cycle of the new membrane The flux was the highest, and the flux decreased to a certain extent from the second cycle, but after that, it could be maintained at a relatively stable level with the extension of the running time.

Claims (5)

1. a black and odorous water forward osmosis-coagulation-anoxic hydrolysis combined emergency treatment method, is characterized in that, comprises the steps: 1) The black and odorous water is firstly subjected to three-level concentration treatment through stepped forward osmosis. The third-level drawing liquid is osmotically diluted and sent to the second-level forward osmosis to continue the drawing operation. Finally, it is sent to the first-level forward osmosis for black and smelly water concentration, and the first-level dilution and drawing The liquid is sent to the reverse osmosis unit for concentration and returned to the three-stage forward osmosis system for recycling; 2) The black and odorous water concentrate enters the coagulation and sedimentation treatment device to remove iron, manganese and suspended solids and colloidal substances in water; 3) The black and odorous water concentrate is sent to the biofilm anoxic tank for anoxic hydrolysis to improve the biodegradability of the concentrated water and reduce the organic load. The effluent is finally discharged into the municipal sewage pipe network and sent to the sewage plant for centralized treatment. 2. The combined emergency treatment method for black and odorous water according to claim 1, characterized in that, in the step 1), both the primary and secondary forward osmosis concentration ratios are 2 times , the three-stage forward osmosis concentration ratio is 3 times, and the black and odorous water is reduced by 12 times after the cascade concentration. 3. The method for combined emergency treatment of black and odorous water with forward osmosis-coagulation-anoxic hydrolysis according to claim 2, characterized in that, in the step 1), the forward osmosis drawing liquid adopts an inorganic salt system drawing liquid, and the three-stage The initial concentration of the draw solution is 2M, and the first-level diluted draw solution is sent to the reverse osmosis unit to be concentrated to 2M. 4. The combined emergency treatment method for black and odorous water according to claim 1, characterized in that, in the step 2), PAC is used as a coagulant, and air agitation is adopted in the mixing reaction stage The mixing method promotes the oxidation precipitation of Fe ²⁺ and Mn ²⁺ . 5. The combined emergency treatment method for black and odorous water according to claim 1, characterized in that, in the step 3), the anoxic tank is filled with suspended fillers, and the anoxic tank is hydraulically stopped. The time is 2~4 hours.

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