CN1331779C - A method for improving the operation stability of anaerobic reactor - Google Patents

Abstract

The present invention provides a method for improving stability of an anaerobic reactor and preventing accumulation of propionic acid. Exogenous propionic acid of a certain concentration and nickel ions are added to each stage of anaerobic sludge domestication, and the resolution capability of anaerobic sludge for the excessive propionic acid is obviously strengthened. When the concentration of the propionic acid in the operating process of an anaerobic reactor is increased within a certain range because of the fluctuation of process conditions, the excessive propionic acid can be degraded rapidly; thereby, 'rancidity' caused by the accumulation of a large amount of the propionic acid can be avoided, and the operating stability of the anaerobic reactor is improved. The tolerant capacity and the degrading capacity of the anaerobic sludge domesticated by the present invention for the propionic acid are greatly improved, and the stability of the anaerobic reactor for resisting water inflow load impact and the technological condition fluctuation are obviously increased (figure 3).

Description

A method for improving the operation stability of anaerobic reactor

1. Technical field

The invention relates to a method for improving the operation stability of an anaerobic reactor, which belongs to the sewage treatment technology in the field of environmental protection engineering and is mainly used in the anaerobic biological treatment process of high-concentration organic wastewater.

2. Technical Background

The anaerobic biological treatment process of high-concentration organic wastewater, also known as anaerobic digestion, is a process in which fermentative bacteria and methanogenic bacteria cooperate to metabolize under anaerobic conditions to decompose organic pollutants and produce CH ₄ and CO ₂ . Compared with the conventional aerobic treatment, the anaerobic digestion process has the advantages of high organic load, low energy consumption, and less residual sludge production in the treatment of organic wastewater. At the same time, the biogas produced in the anaerobic digestion process is a very good It is a very promising process for the treatment of organic pollutants. Especially after the 1970s, the anaerobic upflow sludge bed reactor (UASB reactor) was successfully developed. This anaerobic reactor mainly characterized by granular sludge has high pollutant treatment efficiency. In the past nearly 20 years, it has been widely used in various types of high-concentration organic wastewater treatment, such as food, papermaking, fermentation, poultry breeding and other industries. In recent years, anaerobic technology has been used in the treatment of low-concentration organic wastewater such as urban domestic sewage Significant progress has also been made. The current water pollution in my country is a typical comprehensive organic pollution, so strengthening the research and development of high-efficiency anaerobic treatment process is of great significance for mitigating the pollution status.

The entire anaerobic treatment process can be regarded as a synergistic effect of various interdependent microorganisms. After a series of reactions in series, complex organic matter is finally converted into methane. stage. In the stage of hydrolytic acidification, complex organic matter is decomposed by fermentation bacteria to produce ethanol and a large number of low-molecular volatile organic acids (VFA), mainly including formic acid, acetic acid, propionic acid, butyric acid and lactic acid; The form of methane that is removed has the potential to accumulate in large quantities in the system, causing "rancidity" of the anaerobic system.

The phenomenon of "rancidity" has always been a big problem restricting the practical application of anaerobic process, which generally starts with the accumulation of propionic acid, and the phenomenon of propionic acid accumulation can be observed before the "rancidity" occurs in many anaerobic reactors . When volatile organic acids accumulate in an anaerobic reactor, most of the methanogenic bacteria in the anaerobic sludge are inhibited and the methanogenic process stops, and the entire anaerobic reactor cannot continue to degrade organic pollutants normally. Processing failed. Therefore, avoiding the accumulation of organic acids and improving the stability of the anaerobic system during anaerobic treatment is an urgent problem to be solved.

Since propionic acid is an intermediate metabolite in the anaerobic treatment system, its concentration change is affected by two factors: the production rate of propionic acid and the conversion rate of propionic acid. Previous researchers believed that the decisive link to prevent the accumulation of propionic acid was to reduce the production of propionic acid, that is, to minimize or eliminate the production of propionic acid by controlling the pre-fermentation conditions and fermentation types, for example, by controlling the impact load of influent, redox Process conditions such as increased potential, suppression of toxic pollutants, and pH changes. However, it is very difficult to strictly control the above process conditions for a long time during the actual operation of the anaerobic reactor. Once the conditions change, it may cause a change in the type of fermentation, causing an increase in the production of propionic acid in the reactor and leading to "rancidity" .

Since the anaerobic reactor always has the risk of a large amount of propionic acid accumulation in the system during the actual operation process, and then "rancidity" occurs, many designers have reduced the sludge load to a certain extent when designing anaerobic reactors, hoping that by reducing An efficient way to improve the stability of anaerobic reactor operation. This is also the main reason why the actual operating load of the anaerobic reactor is far lower than that of the experimental device.

3. Contents of the invention

Technical Problem The object of the present invention is to provide a method for improving the operation stability of an anaerobic reactor to prevent the accumulation of propionic acid during the operation of the anaerobic reactor.

Technical solutions

By adding a certain concentration of propionic acid and trace elements in the acclimation stage of anaerobic sludge, the ability of anaerobic sludge to decompose excess propionic acid is improved. When the concentration of propionic acid increases within a certain range during the operation of the anaerobic reactor, the excess propionic acid can be rapidly degraded, thereby avoiding the "rancidity" caused by the accumulation of a large amount of propionic acid, and improving the operation stability of the anaerobic reactor.

A method for improving the operational stability of an anaerobic reactor, comprising:

1. Inoculate the remaining sludge in the anaerobic reactor according to the dosage of 0.5KgMLVSS/ ^m3 in the anaerobic reactor or inoculate the remaining sludge from the urban domestic sewage treatment plant after anaerobic digestion treatment according to the dosage of 0.8KgMLVSS/ ^m3 For sludge, control the volume load of chemical oxygen demand (COD) entering the anaerobic reactor at 0.5-0.6kg/m ³ d, and keep the system running stably for more than 10 days;

2. Gradually increase the influent COD volume load from 0.6kg/m ³ d to 1.5kg/m ³ d. Stable operation for 10 days after kg/m ³ d;

3. Increase the influent COD volume load from 1.5kg/m ³ d to 3.5kg/m ³ d. Supplement nickel chloride (NiCl ₂ ) to ensure that the concentration of nickel ions (Ni ²⁺ ) in the mixed solution in the reactor reaches between 0.08 and 0.55 mg/L; when the COD volume load reaches 3.5 kg/m ³ d, it will run stably for 10 days;

4. Gradually increase the influent COD volume load from 3.5kg/m ³ d to the final operating load of the reactor design. At this stage, artificially add propionic acid with a concentration of 1.10mmol/L to the influent, and at the same time contribute to the Supplement nickel chloride (NiCl ₂ ) in the reactor to ensure that the concentration of nickel ions (Ni ²⁺ ) in the mixed solution in the reactor reaches between 0.08 and 0.30 mg/L;

5. When the COD volume load reaches the final operating load of the reactor and runs stably for 15 days, stop adding exogenous propionic acid and nickel ions to the influent water, the anaerobic sludge domestication process is over, and the anaerobic reactor is in normal operation and continues to run .

Beneficial effect

The invention mainly prevents propionic acid accumulation from the aspect of increasing the conversion rate of anaerobic sludge to propionic acid. Through long-term research, we found that artificially adding a certain concentration of propionic acid during the initial acclimation process of anaerobic sludge can increase the utilization rate of H ₂ by methanogenic bacteria in anaerobic sludge and reduce the concentration of H ₂ in the reactor, while The reduction of H ₂ concentration can greatly accelerate the decomposition rate of propionic acid by propionic acid oxidizing bacteria in anaerobic sludge, thereby preventing the accumulation of propionic acid in the anaerobic reactor and improving the operation stability of the anaerobic reactor. The method for domesticating anaerobic sludge by adding exogenous propionic acid of the present invention can improve the decomposition ability of anaerobic sludge to propionic acid, the anaerobic reactor after propionic acid domestication and the anaerobic reactor started under conventional conditions Compared with that, the running stability is significantly improved.

1. The test results show that the tolerance and decomposition ability of anaerobic sludge after propionic acid acclimation to propionic acid are significantly improved (Fig. 1, Fig. 2).

Propionic acid with a concentration of 2.0, 4.0, 8.0, and 12.0 mmol/L was added to the anaerobic sludge acclimated by propionic acid and the control anaerobic sludge (without adding propionic acid, acclimated in a conventional way), respectively. Their tolerance and degradation of different concentrations of propionic acid impact, the research results are shown in Figure 1 and Figure 2: Anaerobic sludge domesticated by propionic acid showed strong propionic acid degradation after being impacted by high concentration of propionic acid ability, for the initial concentration of propionic acid impact of 4.0mmol/L, the residual propionic acid concentration has dropped to 0.94mmol/L after 6 hours, while the reactor as a control needs to reach the same level after 12 hours; for the initial concentration of 8.0mmol/L and 12.0mmol/L of propionic acid shock, after 10 hours and 16 hours of degradation of propionic acid acclimated anaerobic sludge, the residual propionic acid concentration was less than 1.0mmol/L, while the control reactor showed Severe propionate inhibition was observed, with no significant decrease in propionate concentration within 16 hours.

2. The operation stability of the anaerobic reactor after the acclimation of propionic acid is significantly improved:

We maintained the same operating process conditions (influent COD concentration, temperature, influent pH, redox potential, etc.) of the anaerobic reactor and the control reactor after propionic acid acclimation, and operated continuously for 60 days, sampling every 2 days Once, measure the propionic acid concentration change in the reactor, the result is shown in Figure 3.

It can be seen from the experimental results that under the same operating conditions, the continuous operation for 60 days, as a control, the fluctuation range of propionic acid concentration in the reactor without propionic acid acclimation is between 0.32 ~ 3.04mmol/L, and the average propionic acid concentration is 1.392mmol/L; while the concentration of propionic acid in the anaerobic reactor acclimated by propionic acid ranged from 0.21 to 1.12mmol/L, and the average concentration of propionic acid was 0.557mmol/L. Significantly lower than that of the control reactor, showing good operational stability.

4. Description of drawings

Figure 1. Degradation of propionic acid by anaerobic sludge acclimated to propionic acid

Figure 2. The degradation of propionic acid by conventional domesticated anaerobic sludge (control)

Figure 3. Changes in the concentration of propionic acid in the reactor under continuous operation conditions

5. Specific implementation

The specific implementation process of the present invention is described below.

For a newly built anaerobic reactor, the remaining sludge of other anaerobic reactors can be inoculated in the reactor according to the dosage of 0.5KgMLVSS/ ^m3 (it can also be inoculated according to the dosage of 0.SKgMLVSS/ ^m3 Sewage treatment plants have undergone anaerobic digestion of excess sludge), and then control the influent COD volume load at 0.5-0.6kg/m ³ d for continuous operation. When the anaerobic reactor starts to continuously and stably generate biogas, the entire anaerobic reactor When the COD removal rate reaches above 75%, it can be considered that the anaerobic reactor has reached a stable operation at this load level. Keep this state and continue to operate for more than 10 days, and enter the subsequent load increase stage;

Gradually increase the load to 1.5kg/m ³ .d from the original volume load of 0.6kg/m ³ d. At this stage, add exogenous propionic acid to the influent to reach a concentration of 0.40mmol/L. When the COD volume load reaches 1.5 kg/m ³ .d and the COD removal rate of the effluent reaches more than 70%, it can be considered that the anaerobic reactor has reached a stable operation at this load level. Keep this state and continue to operate for more than 10 days, and enter the subsequent load increase stage;

Gradually increase the influent COD volume load from 1.5kg/m ³ .d to 3.5kg/m ³ .d, add exogenous propionic acid to the Supplement nickel chloride (NiCl ₂ ) in the reactor to ensure that the concentration of nickel ions (Ni ²⁺ ) in the mixed solution in the reactor reaches between 0.08 and 0.55mg/L; when the COD volume load reaches 3.5kg/m ³ .d and the water The COD removal rate reaches more than 70% stably. It can be considered that the anaerobic reactor has reached a stable operation at this load level. Keep this state and continue to operate for more than 10 days before entering the subsequent load increase stage;

Gradually increase the influent COD volume load from 3.5kg/m ³ .d to the final operating load of the reactor design. At this stage, add exogenous propionic acid to the influent to reach a concentration of 1.10mmol/L. Replenish nickel chloride (NiCl ₂ ) inside the reactor to ensure that the concentration of nickel ions (Ni ²⁺ ) in the mixed solution in the reactor reaches between 0.08 and 0.30 mg/L; when the COD volume load reaches the final operating load of the reactor and the COD removal rate of the effluent is stable If the design requirements are met, it can be considered that the anaerobic reactor has finally reached a stable operation. After maintaining this state and continuing to operate stably for 15 days, stop adding exogenous propionic acid and nickel ions to the influent, and the anaerobic sludge domestication process is over, and the anaerobic reaction The device is in normal operation and continues to operate.

The tolerance and degradation ability of anaerobic sludge domesticated in this way to propionic acid are greatly improved (Figure 1, Figure 2), and the stability of the entire anaerobic reactor in response to influent load shocks and fluctuations in process conditions is significantly increased (image 3).

Claims (1)

1. A method for improving the operational stability of an anaerobic reactor, comprising: 1) Inoculate the remaining sludge in the anaerobic reactor at the dosage of 0.5KgMLVSS/ ^m3 in the anaerobic reactor or inoculate the remaining sludge from the urban domestic sewage treatment plant after anaerobic digestion treatment at the dosage of 0.8KgMLVSS/ ^m3 For sludge, control the volume load of COD entering the anaerobic reactor at 0.5-0.6kg/m ³ d, and keep the system running stably for more than 10 days; 2) Increase the influent COD volume load from 0.6kg/m ³ d to 1.5kg/m ³ d, add exogenous propionic acid to the influent at this stage to reach a concentration of 0.40mmol propionic acid/L, when the COD volume load reaches Stable operation for 10 days after 1.5kg/m ³ d; 3) Gradually increase the influent COD volume load from 1.5kg/m ³ d to 3.5kg/m ³ d. Replenish nickel chloride (NiCl ₂ ) inside to ensure that the concentration of nickel ions (Ni ²⁺ ) in the mixed solution in the reactor reaches between 0.08 and 0.55mg/L; when the COD volume load reaches 3.5kg/m ³ d, it will run stably for 10 days ; 4) Gradually increase the influent COD volume load from 3.5kg/m ³ d to the final operating load of the reactor design. At this stage, add propionic acid with a concentration of 1.10mmol/L to the influent, and at the same time add Nickel chloride (NiCl ₂ ) is supplemented internally to ensure that the concentration of nickel ions (Ni ²⁺ ) in the mixed solution in the reactor reaches between 0.08 and 0.30 mg/L; 5) When the COD volume load reaches the final operating load of the reactor and runs stably for 15 days, stop adding exogenous propionic acid and nickel ions to the influent water, the anaerobic sludge acclimatization process is over, and the anaerobic reactor is in normal operation and continues to run .