CN100361908C - A kind of sewage denitrification treatment method - Google Patents

Abstract

The present invention discloses a processing method for sewage denitrification, which comprises the steps of denitrification, precipitation, carbon oxidation, reprecipitation and nitrification. The present invention divides an aerobic section into a carbon oxidation aerobic section and a nitrification aerobic section for creating habitats respectively suitable for heterotrophic bacteria and autotrophic nitrifying bacteria to enable the heterotrophic bacteria and the autotrophic nitrifying bacteria to take part in biochemical reactions in the state of the optimal ecological niche at a high speed; because sludge in each of the steps of the method is independent, the inhibition of the activity of active sludge is avoided when three different functions of microbe habitats are simultaneously satisfied. The method is suitable for processing high-COD and high-ammonia nitrogen sewage, particularly latrine sewage; compared with the A/O method, the present invention has the advantages of low energy consumption, small occupied area and high denitrogenation efficiency.

Description

A kind of sewage denitrification treatment method

technical field

The invention belongs to a new method for biological denitrification treatment of sewage, in particular to a treatment method for denitrification A/O/N (Anoxic-Oxic-Nitrifying) of sewage, which is especially suitable for the treatment of public toilet sewage.

Background technique

At present, the more popular biological denitrification method in sewage treatment is the A/O (Anoxic-Oxic) method pioneered in the early 1980s; its main feature is that the denitrification section is placed at the head of the treatment process, so it is also called the former Set up denitrification biological nitrogen removal treatment method. However, this method has poor denitrification effect on wastewater with high chemical oxygen demand (COD) and ammonia nitrogen (NH ₃ -N) content.

The first reason is that the content of organic matter in the raw water is too high. Although some dissolved organic matter can be adsorbed and degraded in the pre-denitrification section, the concentration of organic matter is still high, so that in the aerobic stage, the heterogeneous species with a faster proliferation rate The trophic bacteria multiply rapidly, but the autotrophic nitrifying bacteria do not get the advantage, and the nitrification reaction is difficult to proceed smoothly. In order to solve this problem, the usual practice is to increase the hydraulic retention time of the aerobic section to reduce the organic matter content in the sewage and meet the conditions of nitrification reaction, which will inevitably increase energy consumption and increase the occupied area. The second is that the activated sludge in the A/O method is continuously in the dynamic process from aerobic to anoxic and from anoxic to aerobic, the activity will be inhibited to a certain extent, so that the biochemical reaction efficiency is low.

Public toilet sewage with high COD and high ammonia nitrogen is harmful to the environment. It is difficult to efficiently nitrify and achieve biological denitrification under the traditional A/O method, which is a difficult point in the denitrification treatment of urban sewage.

Contents of the invention

The object of the present invention is to overcome the defects of the above-mentioned prior art, and provide a sewage denitrification treatment method, which can perform efficient biological denitrification treatment on sewage with high COD and high ammonia nitrogen.

A kind of sewage denitrification treatment method provided by the invention, its steps are:

(1) Mix the sewage to be treated with the nitrifying liquid and introduce it into the denitrification tank. Under anoxic conditions, the denitrification reaction is carried out under the action of denitrifying bacteria. The sludge concentration is 3-5g/L, and the sludge age is 4 ～6 days, the hydraulic retention time is 1～3 hours;

(2) Introduce the denitrified sewage and return sludge into the carbon oxidation tank for aerobic aeration. The sludge concentration in the carbon oxidation tank is 3-5g/L, and the sludge age is 3-8 days. The force residence time is 6 to 10 hours;

(3) Introduce the carbon-oxidized sewage into the first sedimentation tank for mud-water separation, and make the precipitated supernatant enter the nitrification tank for nitrification reaction, and the precipitated sludge is used as activated sludge in the carbon oxidation stage, part or all Return to the carbon oxidation tank, the reflux ratio of the settled sludge back into the carbon oxidation tank is 50-100%, and the remaining sludge is discharged;

(4) The settled sewage and return sludge are introduced into the nitrification tank for nitrification treatment. The sludge concentration in the nitrification tank is 2-4g/L, the sludge age is 15-30 days, and the water temperature in the nitrification tank is 10-30°C. The hydraulic retention time of the pool is 3 to 8 hours;

(5) The sewage after the nitrification reaction is introduced into the second settling tank for mud-water separation, and a part of the supernatant after the precipitation is discharged partly as the nitrifying liquid in the step (1) and returns to the denitrification tank, and the supernatant after the precipitation The reflux ratio is 100% to 300%, and the settled sludge is returned to the nitrification tank as the activated sludge in step (4), and the remaining sludge is discharged.

The essence of the present invention is to divide the aerobic stage into a carbon oxidation aerobic stage and a nitrification aerobic stage, to create respective suitable habitats for heterotrophic bacteria and autotrophic nitrifying bacteria, so that they can all be in the state of the best ecological niche. The biochemical reaction is carried out at a relatively high speed; and because the sludge in the three stages of the method does not mix with each other, while satisfying three different functional microbial habitats, the activity of the activated sludge is prevented from being inhibited. This method is particularly suitable for treating high COD and high ammonia nitrogen sewage, such as public toilet sewage; different from traditional A/O, each stage of the present invention has produced its own top community, making it all in the state of the best ecological niche with a relatively Large speed growth, reproduction, denitrification, carbon oxidation and nitrification reactions. The invention has the advantages of low energy consumption, small occupied area and high denitrification efficiency. Specifically, the present invention has the following characteristics:

(1) Separate denitrification, carbon oxidation, and nitrification processes into three different reaction pools to create conditions suitable for denitrification bacteria, heterotrophic bacteria (carbon oxidizing bacteria) and nitrifying bacteria respectively, which is different from traditional A /0 is different in that each stage of the present invention has produced respective top communities respectively, so that they all grow and reproduce at a greater speed in the state of the best ecological niche, and carry out denitrification, carbon oxidation and nitrification reactions.

(2) The sludge at each stage is not mixed with each other. While satisfying three different functional microbial habitats, it avoids the inhibition of the activity of the activated sludge, and the biochemical reaction rate is high.

(3) Fillers can be set separately in the denitrification stage and nitrification stage, with large biomass and fast reaction speed.

(4) Before the denitrification stage, no additional carbon source is needed, and the alkalinity generated by the denitrification reaction can compensate for about half of the alkalinity consumed by the nitrification reaction, so there is no need to add alkali separately.

(5) The denitrification stage is the first step in the treatment method. On the one hand, the ability to resist impact loads is improved; Part of the COD is removed, which reduces the load of COD oxidation in the latter two stages, and reduces the residence time of the carbon oxidation stage to a certain extent.

(6) The present invention is a plug-flow type, and there is a nitrifying liquid circulating back, and the whole process is in anoxic and aerobic alternate operation, and under this condition, there is no risk of sludge bulking.

(7) The sludge does not go through the anoxic-aerobic cycle, and the activated sludge reacts in each reaction tank; the reaction rate is fast, the hydraulic retention time is short, the energy consumption is low, and the floor area is small.

In a word, the present invention can perform high-efficiency biological denitrification treatment on sewage with high COD and high ammonia nitrogen.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, the present invention includes denitrification-precipitation-carbon oxidation-reprecipitation-nitration stages.

Concrete steps of the present invention are as follows:

(1) Denitrification stage:

The pretreated sewage is mixed with nitrification liquid and introduced into the denitrification tank. At this stage, denitrifying bacteria use a large amount of easily degradable organic matter in the raw water as electron donors, and nitrate nitrogen in the nitrifying liquid as electron acceptors to perform rapid denitrification reaction, and discharge nitrogen in the form of free nitrogen gas. The control parameters at this stage are: the sludge concentration is 3-5g/L, the sludge age is 4-6 days, and the hydraulic retention time is 1-3 hours. The optimal control parameters at this stage are: sludge concentration is 3-4g/L, sludge age is 4-5 days, hydraulic retention time is 1-2 hours.

The reaction formula is:

5C(organic carbon)+2H ₂ O+4NO ₃ ^- →2N ₂ +4OH ^- +5CO ₂

(2) Carbon oxidation stage

The denitrified sewage and return sludge are introduced into the carbon oxidation tank for aerobic aeration. The control parameters at this stage are: the sludge concentration is 3-5g/L, the sludge age is 3-8 days, and the hydraulic retention time is 6-10 hours. The optimal control parameters at this stage are: sludge concentration of 3-4g/L, sludge age of 4-5 days, and hydraulic retention time of 6-8 hours.

The content of organic matter in the sewage entering the pool is high, so that the heterotrophic bacteria (carbon oxidizing bacteria) with a higher specific growth rate are dominant, while the nitrifying bacteria with a lower specific growth rate are at a disadvantage and are washed out. The result is: organic matter degradation High rate, high sludge growth rate, short sludge age, low ammonia nitrogen nitrification rate, and poor nitrification effect. After the sewage is treated by carbon oxidation, the COD of the effluent is greatly reduced, while the concentration of ammonia nitrogen does not change much.

The reaction formula of the above process is:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; z</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Right\; Arrow;</span>\mathrm{<span\; class="notranslate">\; xC</span>}{\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; o</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&Delta;H</span>}$

(3) Precipitation treatment

The carbon-oxidized sewage is introduced into the first sedimentation tank for mud-water separation. To prevent heterotrophic bacteria from entering the latter reaction tank - nitrification tank, only the supernatant after precipitation enters the nitrification tank for nitrification reaction. The settled sludge is the activated sludge in the carbon oxidation stage, part or all of which is returned to the carbon oxidation tank, and the reflux ratio of returning to the carbon oxidation tank is 50-100% (the optimization range is: 50-75%), and the remaining Sludge discharge.

(4) Nitrification stage

Sewage and return sludge enter the nitrification tank. The control parameters at this stage are: sludge concentration of 2-4g/L, sludge age of 15-30 days, water temperature of nitrification tank of 10-30°C, and hydraulic retention time of nitrification tank of 3-8 hours. The optimal control parameters at this stage are: sludge concentration of 2.5-3.5g/L, sludge age of 15-25 days, nitrification tank water temperature of 13-25°C, and nitrification tank hydraulic retention time of 4-6 hours.

The sewage entering the pool has low organic matter content and high ammonia nitrogen content, and the autotrophic nitrifying bacteria with ammonia nitrogen as the substrate dominate in this section with high biomass. The result is that most of the ammonia nitrogen is converted into nitrate nitrogen, and the nitrification High rate. After the sewage is treated with nitrification, the concentration of ammonia nitrogen in the effluent is greatly reduced, while the concentration of nitrate nitrogen is increased. The reaction at this stage is:

The overall reaction formula of nitration reaction is:

NH ₄ ⁺ +2O ₂ →NO ₃ ^- +2H ⁺ +H ₂ O+(307.1～438.9)kJ

(5) Precipitation treatment again

The sewage after nitrification is introduced into the second sedimentation tank for mud-water separation, part of the supernatant after precipitation is discharged, and part of it is used as the nitrification liquid in the denitrification stage, and is returned to the denitrification tank, and the reflux ratio is 100% to 300%. The optimization range is: 150%～250%). The settled sludge is the activated sludge in the nitrification stage and is returned to the nitrification tank, and the remaining sludge is discharged.

Both the denitrification tank and the nitrification tank can be selectively added with soft fillers (such as fiber bundles), semi-soft fillers (such as polypropylene or polyethylene, etc.), combined fillers (composed of plastic rings and vinylon filaments), In addition, other fillers may also be added.

Example 1

The water quality of a public toilet septic tank is as follows:

project BOD₅ COD SS NH₃-N Concentration (mg/L) 650 1210 485 165

Carry out as shown in accompanying drawing 1, be 2 hours in denitrification tank hydraulic retention time, be 6 hours in carbon oxidation tank hydraulic retention time, be 3 hours in nitrification tank hydraulic retention time, the first settling tank flows back into the carbon oxidation tank The reflux ratio is 75%, the reflux ratio of the second sedimentation tank back into the denitrification tank is 150%, the residence time of the first sedimentation tank is 2 hours, and the residence time of the second sedimentation tank is 3 hours. The carbon oxidation tank is suspended activated sludge, the sludge concentration is 4g/L, the sludge age is 4 days, and the water temperature is 18°C. The method can make COD, BOD ₅ , NH ₃ -N removal rates all over 95%, and the treated water can be used as non-contact reuse water after disinfection, or be discharged up to standard after further treatment.

Example 2

The water quality of a septic tank sewage is as follows:

project BOD₅ COD SS NH₃-N Concentration (mg/L) 1420 2581 1380 245

Carry out as shown in accompanying drawing 1, be 3 hours in denitrification tank hydraulic retention time, be 10 hours in carbon oxidation tank hydraulic retention time, be 6 hours in nitrification tank hydraulic retention time, the first settling tank flows back into carbon oxidation tank The reflux ratio is 100%, the reflux ratio of the second sedimentation tank back into the denitrification tank is 300%, the residence time of the first sedimentation tank is 3 hours, and the residence time of the second sedimentation tank is 4 hours. Put suspended activated sludge in the carbon oxidation tank, the sludge concentration is 4g/L, the sludge age is 3 days, and the water temperature is 20°C; the sludge concentration in the nitrification tank is 5g/L, the sludge age is 30 days, and the water temperature is 20°C ℃. The method can make the removal rates of COD, BOD ₅ , and NH ₃ -N over 95% respectively, and the treated water can be used as non-contact reuse water after disinfection, or be discharged up to standard after further treatment.

Claims (7)

1. A sewage denitrification treatment method comprises the following steps:

(1) Mixing the sewage to be treated with a nitrifying liquid, introducing the mixture into a denitrification tank, and carrying out denitrification reaction under the action of denitrifying bacteria under the anoxic condition, wherein the sludge concentration is 3-5 g/L, the sludge age is 4-6 days, and the hydraulic retention time is 1-3 hours;

(2) Introducing the sewage after denitrification treatment and return sludge into a carbon oxidation tank for aerobic aeration, wherein the sludge concentration of the carbon oxidation tank is 3-5 g/L, the sludge age is 3-8 days, and the hydraulic retention time of the carbon oxidation tank is 6-10 hours;

(3) Introducing the sewage subjected to carbon oxidation into a first sedimentation tank for sludge-water separation, allowing the supernatant after sedimentation to enter a nitrification tank for nitrification reaction, allowing part or all of the sludge after sedimentation to be used as active sludge in the carbon oxidation stage to flow back to the carbon oxidation tank, allowing the backflow ratio of the sludge after sedimentation to flow back into the carbon oxidation tank to be 50-100%, and discharging the residual sludge;

(4) Introducing the precipitated sewage and return sludge into a nitrification tank for nitrification treatment, wherein the sludge concentration of the nitrification tank is 2-4 g/L, the sludge age is 15-30 days, the water temperature in the nitrification tank is 10-30 ℃, and the hydraulic retention time of the nitrification tank is 3-8 hours;

(5) Introducing the sewage after the nitration reaction into a second sedimentation tank for sludge-water separation, discharging a part of the precipitated supernatant as a nitration liquid in the step (1) and refluxing the part of the supernatant as a nitration liquid to a denitrification tank, wherein the reflux ratio of the precipitated supernatant is 100-300%, the precipitated sludge is used as the activated sludge in the step (4) and reflows to the nitrification tank, and the residual sludge is discharged.

2. The method of claim 1, wherein: in the step (1), the sludge concentration is 3-4 g/L, the sludge age is 4-5 days, and the hydraulic retention time is 1-2 hours; in the step (2), the sludge concentration of the carbon oxidation pond is 3-4 g/L, the sludge age is 4-5 days, and the hydraulic retention time of the carbon oxidation pond is 6-8 hours.

3. The method according to claim 1 or 2, characterized in that: in the step (3), the reflux ratio of the precipitated sludge to the carbon oxidation tank is 50-75%.

4. The method according to claim 1 or 2, characterized in that: in the step (4), the sludge concentration of the nitrification tank is 2.5-3.5 g/L, the sludge age is 15-25 days, the water temperature in the nitrification tank is 13-25 ℃, and the hydraulic retention time of the nitrification tank is 4-6 hours.

5. The method according to claim 1 or 2, characterized in that: in the step (5), the reflux ratio of the supernatant after precipitation is 150-250%.

6. The method according to claim 1 or 2, characterized in that: soft filler, semi-soft filler or combined filler is added into the denitrification tank.

7. The method according to claim 1 or 2, characterized in that: adding soft filler, semi-soft filler or combined filler into the nitrification tank.

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