CN103130379A - Treatment method of coking ammonia distillation wastewater - Google Patents

Abstract

The invention discloses a treatment method for coking ammonia distillation wastewater. The process is pretreatment and biochemical treatment of ammonia distillation wastewater. The pretreatment adopts a regulating tank, an internal electrolysis reactor, a Fenton oxidation tank and a coagulation sedimentation tank, and the biochemical treatment adopts a sequence batch The Membrane Bioreactor process undergoes four processes of inflow, idle, reaction, and discharge in sequence according to the time period; it can effectively remove refractory organic pollutants and ammonia nitrogen, enhance the quality of effluent water, and reduce equipment operation and investment costs.

Description

A kind of treatment method of coking ammonia distillation wastewater

technical field

The invention belongs to the technical field of water treatment, and in particular relates to a treatment method for coking ammonia distillation wastewater.

Background technique

The metallurgical industry is a super large pollutant discharge in my country, and coking wastewater is one of the largest pollution sources in the metallurgical industry. In addition to a large amount of volatile phenols, COD, cyanides, and sulfides, coking wastewater also contains high concentrations of ammonia nitrogen and many refractory fused-ring aromatics and heterocyclic compounds, such as indole, naphthalene, quinoline, etc., which are harmful to the environment. It has a great impact and is considered to be one of the most difficult industrial wastewater. It has been a difficult problem for various metallurgical enterprises in the country for a long time. In recent years, with the development of my country's iron and steel industry, the scale of the corresponding coking has continued to expand, the resulting discharge of coking wastewater has doubled, and the pollution intensity has intensified.

Through the novelty search, some related patents and articles were retrieved, such as the invention of "treatment method of coking wastewater" (CN 101781067). This method requires many structures to be treated, the process is complicated, the floor area is large, and the operating cost is also high . "A method for treating coking wastewater after ammonia removal" (CN 101875526A) was invented. This method has a large amount of sludge discharge, causing sludge treatment problems, and the removal effect of ammonia nitrogen is not ideal. "Treatment of coking wastewater with integrated membrane bioreactor" (Pei Liang et al _. ), this article discusses the feasibility of using integrated membrane bioreactor to treat coking wastewater. Both have achieved good treatment effect, but there is a large amount of sludge discharge, resulting in sludge treatment problems, and the removal effect of ammonia nitrogen is not ideal.

At present, the treatment of coking wastewater in China generally adopts the secondary treatment process of pretreatment and biochemical treatment, but after conventional secondary biological treatment, it is difficult to discharge pollutants such as COD and ammonia nitrogen in the wastewater up to the standard, and cannot meet the new sewage discharge standards. restrict the development of enterprises. However, foreign countries have adopted more complex pretreatment and other methods to control the water quality entering the biochemical system before the secondary biochemical treatment to prevent excessive concentrations of toxic pollutants, and adopted a tertiary purification system after the biochemical treatment process. The so-called tertiary treatment is a technological process composed of various physical and chemical methods centered on biological treatment, such as dephenolization, ammonia distillation, biological treatment and activated carbon adsorption. However, the operation and investment costs of the tertiary treatment process are relatively high. If an appropriate pretreatment process can be selected, the content of toxic factors entering the secondary biochemical system can be greatly reduced after pretreatment, and the biodegradability of wastewater can be improved. In addition, the subsequent use of an efficient biochemical treatment system to strengthen the treatment of effluent water quality, in order to replace the costly tertiary treatment process, has important practical significance for the sustainable development of the enterprise.

Contents of the invention

In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a low-cost, high-efficiency treatment method for coking ammonia distillation wastewater. After optimized pretreatment + high-efficiency biochemical treatment, the ammonia distillation wastewater can effectively remove refractory organic pollution At the same time, it reduces the operation and investment costs of equipment.

A kind of treatment method of coking ammonia distilled waste water, comprises adjustment tank, internal electrolysis reactor, Fenton oxidation tank, coagulation sedimentation tank and sequencing batch type membrane bioreactor, described method is carried out as follows:

A: Pretreatment of ammonia distillation wastewater. Firstly, the ammonia distillation wastewater is pretreated, and the collected ammonia distillation wastewater is passed into the adjustment tank, and acid substances are added to adjust its pH value, and the pH of the wastewater is controlled between 2.6 and 3.1 to make it an acidic solution. Meet the requirements of the internal electrolysis reaction; the waste water is pumped into the upper part of the internal electrolysis reactor to carry out the internal electrolysis reaction. The process uses activated carbon particles as the cathode, iron filings as the anode, and the electrolyte acts as a conductor to form a primary battery to treat organic substances that are relatively easy to degrade in wastewater. Under the joint action of chemical attachment and other processes, the organic matter undergoes oxidation reaction and destroys its organic polymer structure. Keep the residence time of wastewater in the internal electrolysis reactor at 0.5-2.5h, and the effluent flows into the Fenton oxidation tank;

The Fenton oxidation tank is operated intermittently. In the state of constant stirring, acid substances (usually concentrated sulfuric acid) are added to control the pH value between 2.8-3.2; then ferrous sulfate solid is added to make the ferrous ions The concentration reaches 100-300ppm, and then add the hydrogen peroxide solution with a concentration of 900-1100ppm. Using H ₂ O ₂ under the catalysis of Fe ²⁺ to generate hydroxyl radicals with a very high oxidation potential, non-selective oxidation of the remaining organic matter in wastewater. Control the oxidation reaction time to 0.5-2h in the state of stirring, and the waste water after the reaction flows into the coagulation sedimentation tank;

Add lye to the coagulation sedimentation tank to adjust the pH of the wastewater between 9-10, add 1ppm coagulant PAM, stir for five minutes and then let it settle for 25-40min. The supernatant obtained after precipitation is the pretreated ammonia distillation wastewater.

B: Biochemical treatment of ammonia distillation wastewater. The Sequencing Batch Membrane Bioreactor process (SBMBR) is used to control the environment of aerobic nitrification and anoxic denitrification by means of agitation/aeration, so that the whole system will sequentially experience the four stages of inflow, idleness, reaction and discharge according to the time period. A process, in which the inoculum sludge in the sequencing batch membrane bioreactor is taken from the aerobic return sludge of the chemical plant, which is first put into the membrane bioreactor for one month to make the sludge concentration reach 9500mg/L.

Inflow process: the pretreated ammonia distillation wastewater is injected into the lower part of the membrane bioreactor by the pump, and is sprayed into the reaction tank through the water distribution pipe. Through continuous stirring, the sludge is fully contacted with the ammonia distillation wastewater, and the anoxic ammonia distillation wastewater is controlled. The time is 1.5-2.5h, and the pH of ammonia distillation wastewater is controlled at 8.5-9.0. On the one hand, the characteristics of high NH ₃ -N and high COD in the influent can be used to provide rich carbon sources to the reactor through the agitation of the influent anoxic, so that the carbon-nitrogen ratio basically meets the denitrification conditions, and the nitrate nitrogen On the other hand, the anoxic stirring operation has a ring-opening effect on some refractory organics such as polycyclic aromatic hydrocarbons, making them easy to degrade, that is, improving the biodegradability of ammonia distillation wastewater.

Idle process: The control time range is 4-5h. At this time, the activated sludge microorganisms in the reactor are kept in an anoxic environment, and the high-concentration organic matter in the influent can be fully utilized as a carbon source for denitrification, so that the denitrification reaction can be carried out more efficiently. Thoroughly.

Reaction process: start the blower to aerate the sewage, provide sufficient oxygen for the activated sludge in the membrane bioreactor, and make it in an aerobic state, which can effectively degrade the carbon-containing organic matter in the sewage. At the same time, nitrifying bacteria oxidize ammonia nitrogen in wastewater into nitrite nitrogen and nitrate nitrogen, providing sufficient electron acceptors for the anoxic stage. The aeration reaction time is controlled at 15-17 hours, the pH is controlled at 7.5-8.5, and the aeration rate: water inflow rate (air-water flow ratio) is controlled at 25-35:1. The blower stops the aeration, and the reaction process ends.

Discharge process: Under the negative pressure suction of the suction pump or the effect of water head difference, water and some small molecular substances pass through the membrane module and become system outlet water through the outlet pipeline. Macromolecular substances, activated sludge microorganisms and inorganic particles are all The membrane module is trapped in the reactor. The time of the discharge process is controlled as 1.5-2.5 hours, and the discharge volume is controlled as partial discharge. After the discharge process is completed, the suction pump is turned off to start the next cycle.

The system repeats the four processes of inflow, idle, reaction, and discharge in sequence in the following time. The whole system is always in the state of anoxic and aerobic alternately, with intermittent water inflow and outflow. The mud valve regularly discharges the remaining activated sludge.

The beneficial effects of the present invention are: providing a method for treating coking wastewater by using a regulating tank, internal electrolysis, Fenton oxidation and coagulation-sedimentation combined process as pretreatment, and sequencing batch membrane bioreactor as biochemical section. After the high-concentration coking wastewater is treated by the present invention, the effluent quality can reach the first-level discharge standard of water pollution in the iron and steel industry, greatly increasing the cascade use and recycling of the coking wastewater. The combined process of pretreatment can not only degrade long-chain and ring-shaped organic matter in wastewater, but also effectively improve the biodegradability of wastewater, laying a good foundation for subsequent treatment. The biochemical section adopts the sequencing batch membrane bioreactor, which not only retains the advantages of the traditional SBR process, such as strong shock load resistance, high oxygen transfer efficiency and biochemical reaction efficiency, relatively stable operation, and is not prone to sludge bulking, but also has the advantages of a single reactor Nitrification and denitrification can be realized within a short period of time, saving the anaerobic tank, anoxic tank, sedimentation tank and reflux system, and greatly reducing the area occupied by the process.

Description of drawings

Fig. 1 is the process flow chart of coking ammonia distillation wastewater treatment of the present invention.

Detailed ways

Below in conjunction with Fig. 1, the specific embodiment of the present invention will be further described:

Ammonia distillation wastewater goes through the pretreatment process of regulating tank, internal electrolysis reactor, Fenton oxidation tank and coagulation sedimentation tank in sequence, so that most refractory organic substances are degraded into small molecular substances, improving the biodegradability of ammonia distillation wastewater; The treated ammonia distillation wastewater enters the sequencing batch membrane bioreactor for biochemical treatment, further strengthening the removal of pollutants such as COD and ammonia nitrogen, and enhancing the quality of effluent water.

A: Pretreatment of ammonia distillation wastewater:

Example 1

Slowly add concentrated sulfuric acid to the ammonia distillation wastewater in the adjustment tank while stirring, control the pH of the ammonia distillation wastewater to 2.6, and then inject the ammonia distillation wastewater into the upper part of the rectangular inner electrolysis reactor by the pump to carry out the internal electrolysis reaction. The filler is composed of iron and steel filings and activated carbon particles, which are filled in the reactor with a volume ratio of 1:1. Keep the residence time of ammonia distilled wastewater in the internal electrolysis reactor at 0.5h, and the effluent flows into the Fenton oxidation tank.

The Fenton oxidation tank is operated intermittently. After the wastewater in the tank reaches 3/4, it starts stirring and adds concentrated sulfuric acid at the same time to control the pH value to 2.8. Add ferrous sulfate solid at one time, so that the concentration of ferrous ions reaches 100ppm, and then slowly add 30% hydrogen peroxide solution with a mass fraction to make the concentration reach 900ppm. The oxidation reaction time is controlled to be 0.5h in the state of stirring, and the waste water after the reaction flows into the coagulation sedimentation tank.

Add 10% NaOH solution dropwise to the coagulation sedimentation tank to adjust the pH of the waste water to 9.0, add 1ppm coagulant PAM, stir for five minutes and let it settle for 25 minutes. The supernatant obtained after precipitation is the pretreated ammonia distillation wastewater.

Refer to Table 1 for the selection of test parameters in Embodiment 2 and Embodiment 3 of the pretreatment section.

The operating parameters of each embodiment of the pretreatment section of table 1

The main water quality indicators in the ammonia distillation wastewater are: COD: 3500mg/L, ammonia nitrogen: 210mg/L, volatile phenol: 920mg/L, cyanide: 15mg/L, each embodiment is pretreated by internal electrolysis + Fenton oxidation + flocculation precipitation Finally, the main indicators of the effluent are shown in Table 2.

The removal effect of each embodiment of table 2 pretreatment section to pollutant

The ammonia distillation wastewater after the above pretreatment, COD ≤ 1500mg/L, ammonia nitrogen ≤ 190mg/L, volatile phenol ≤ 80mg/L, cyanide ≤ 2mg/L, B/C ≥ 0.3, effectively strengthened the treatment of difficult organisms While degrading organic matter, it improves the biodegradability of wastewater and creates good water inflow conditions for subsequent biochemical treatment.

B: Biochemical treatment of ammonia distillation wastewater:

Example 1:

The sequencing batch membrane bioreactor process (SBMBR) is adopted. The membrane bioreactor is a built-in type, that is, the membrane module is placed in the bioreactor, and the membrane module adopts PVDF hollow fiber microfiltration membrane. The environment of aerobic nitrification and anoxic denitrification is controlled by means of agitation/aeration, so that the whole system goes through four processes of inflow, idleness, reaction and discharge in sequence according to the time period. The inoculum sludge is taken from the aerobic return sludge of a chemical plant. It is first put into the reactor for domestication. During the domestication period, it is stirred with water for 2 hours, idle for 5 hours, aerated for 15 hours, drained for 2 hours, and domesticated for one month. The concentration is 9500mg/L.

Inflow process: the pretreated ammonia distillation wastewater is injected into the lower part of the membrane bioreactor by the pump, and is sprayed into the reaction tank through the water distribution pipe, so that the activated sludge deposited at the bottom of the reaction tank is boiled. Through continuous stirring, the sludge and The wastewater is fully contacted, and the activated sludge mixture is in an anoxic state at this time. The time to control the anoxic waste water is 1.5h, and the pH of the waste water is controlled at 8.5.

Idle process: The stagnation time of the control system is 4 hours. At this time, the activated sludge microorganisms in the reactor continue to maintain an anoxic environment, and the high-concentration organic matter in the influent can be fully used as a carbon source for denitrification, so that the denitrification reaction can proceed More fully and thoroughly.

Reaction process: Start the blower to aerate the sewage. While fully disturbing the membrane filaments and slowing down the membrane fouling, it also provides sufficient oxygen for the activated sludge in the membrane bioreactor to make it in an aerobic state, which can treat the sewage The carbon-containing organic matter in the carbon dioxide can be effectively degraded. At the same time, nitrifying bacteria oxidize the ammonia nitrogen in the wastewater into nitrite nitrogen and nitrate nitrogen, providing sufficient electron acceptors for the anoxic stage. The aeration reaction time is controlled at 15h, the pH is controlled at 7.5, and the aeration rate: influent (Air-water flow ratio) is controlled at 25:1. The blower stops the aeration, and the reaction process ends.

Discharge process: Under the negative pressure suction of the suction pump or the effect of water head difference, water and some small molecular substances pass through the membrane module and become system outlet water through the outlet pipeline. Macromolecular substances, activated sludge microorganisms and inorganic particles are all The membrane module is trapped in the reactor. The discharge time is controlled to 1.5h, and the discharge volume is 1/3 of the reactor volume. After the discharge process is completed, the suction pump is turned off to start the next cycle.

The system repeats the four processes of inflow, idle, reaction, and discharge in sequence in the following time. The whole system is always in the state of anoxic and aerobic alternately, with intermittent water inflow and outflow. The mud valve regularly discharges the remaining activated sludge. The sludge production rate of the SBMBR system was low, and the sludge volume increased slightly during the test run, but no sludge bulking occurred, and the system operated stably.

Refer to Table 3 for the selection of test parameters in Embodiment 2 and Embodiment 3 of the biochemical section.

The operating parameters of each embodiment of the biochemical section of table 3

After being treated by the sequencing batch membrane bioreactor process, the main indicators of the effluent of each embodiment are shown in Table 4.

The removal effect of each embodiment of the biochemical section of table 4 to pollutants

It can be seen from the results in Table 4 that the ammonia distillation wastewater after the above biochemical treatment has COD≤100mg/L, ammonia nitrogen≤15mg/L, volatile phenol≤0.5mg/L, cyanide≤0.5mg/L, and the process effluent quality is stable. It can meet the first-class discharge standard of iron and steel industry wastewater.

Claims (3)

1. the treatment process of a coking distilled ammonia wastewater, comprise equalizing tank, interior electrolysis reactor, Fenton oxidation pond, coagulative precipitation tank and sequencing batch membrane bioreactor, it is characterized in that described method undertaken by following operation:

A: the pre-treatment of distilled ammonia wastewater: at first distilled ammonia wastewater is carried out pre-treatment, the distilled ammonia wastewater of collecting is passed into equalizing tank, add acid that its pH value is regulated, control the pH of waste water between 2.6～3.1, make it become acidic solution, to be satisfied with the requirement of interior electrolytic reaction; Waste water enters interior electrolysis reactor by infusion, and the residence time is 0.5-2.5h, and water outlet flows into the Fenton oxidation pond;

The Fenton oxidation pond is batch operation, under the state that constantly stirs, adds acid, and its pH value is controlled between 2.8-3.2; Add subsequently the ferrous sulfate solid, make the concentration of ferrous ion reach 100-300ppm, and then to add concentration be the hydrogen peroxide solution of 900-1100ppm, and controlling oxidation time under the state that stirs is 0.5-2h, and reacted waste water flows into coagulative precipitation tank;

Add the pH of alkali lye adjusting waste water in coagulative precipitation tank between 9-10, add the coagulant aids PAM of 1ppm, stir and staticly settle 25-40min after five minutes, after precipitation, the supernatant liquor of gained is pretreated distilled ammonia wastewater;

B: the biochemical treatment of distilled ammonia wastewater: adopt sequencing batch membrane bioreactor technique, experience in turn inflows, idle, reaction, discharge four operations by cycle time;

Flow into operation: pretreated distilled ammonia wastewater is entered the bottom of membrane bioreactor by infusion, spray the inflow reaction tank through water distributor, by continuous stirring, mud is fully contacted with distilled ammonia wastewater, it is 1.5-2.5h that the control anoxic is advanced the distilled ammonia wastewater time, and distilled ammonia wastewater pH is controlled at 8.5-9.0;

Idle operation: the period scope is 4-5h;

Reaction process: start gas blower and begin sewage is carried out aeration, the reaction times is controlled at 15-17h, and pH is controlled between 7.5-8.5, and aeration rate and flooding quantity are controlled at 25-35: 1;

The discharging operation: the discharging activity time is controlled to be 1.5-2.5h;

Repeat in turn subsequently to flow into, leave unused, react, discharge four operations.

2. the treatment process of coking distilled ammonia wastewater according to claim 1, it is characterized in that: the seed sludge concentration in described sequencing batch membrane bioreactor reaches 9500mg/L.

3. the treatment process of coking distilled ammonia wastewater according to claim 1, it is characterized in that: in described discharging operation, the distilled ammonia wastewater quantity discharged is partial discharge.

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