Study On The Law Of Gas Production In Municipal Anaerobic Digestion Process

With the enhancing of sewage treatment capacity and increasing of sewage treatment plants, sludge production is also increasing rapidly. In order to prevent the new pollution caused by the stack and emission of untreated sludge, anaerobic digestion is the global common way of stabilization and treatment resources. It is not only to protect the environment, but also make the sludge to achieve recycling. In order to reveal the influence of different factors on the process of sludge anaerobic digestion and provide guidance for optimizing sludge digestion process, by undertaking different moisture content conditions, different adding amount of bacterium conditions and different microwave pretreatment conditions the experiments of anaerobic digestion gas-production characterized law, it studies the variation of daily gas-production rate, daily methane-production rate, cumulative methane-production and VS degradation rate under different conditions in anaerobic digestion process, and analysis its mechanism by contrast. The main conclusions are as follows:(1) To carry out different moisture content (85%,87%,89%,91%,93%,95%) conditions experiment of anaerobic digestion gas-production characterized law, and the main conclusions are as follows:the daily gas-production rate laws of different moisture content show that firstly decline, then increase rapidly, and reach a peak and maintain drastically and reduce after a period of time. And it can at least twice to reach the peak in60days of sludge anaerobic digestion. The changes of respective components in gas are basically the same and they are hardly changed with the change of moisture content. The cumulative methane-production reaches a maximum222.8ml/g-VS when the moisture content is93%representing85%moisture content sludge increasing13.5%. The daily methane-production rate substantially reduces comparing with the other experimental groups. When the sludge moisture content is93%, VS degradation rate reaches a maximum of47.41%.(2) To carry out different adding amount of bacterium (0,15,30ml/kg-sludge) conditions experiment of anaerobic digestion gas-production characterized law through the different sludge moisture content (87%,89%,91%,93%), and the main conclusions are as follows:the daily gas-production rate does not change with the increase of bacterium amount and the laws show that firstly decline, then increase rapidly, and reach a peak and maintain drastically and reduce after a period of time. And it can at least twice to reach the peak in60days of sludge anaerobic digestion. The adding bacterium promotes the daily methane-production and the cumulative methane-production when the sludge moisture content≤91%. When the sludge moisture is91%and the amount of bacterium added is30ml/kg-sludge, the cumulative methane-production reaches a maximum342.56ml/g-VS representing the blank experimental group210.08ml/g-VS increasing63.06%. At the same time, the VS degradation rate reaches a maximum51.46%. To carry out different adding amount of bacterium (0,30,50,70,90ml/kg-sludge) conditions experiment of anaerobic digestion gas-production characterized law, and the conclusion is as follows:the cumulative methane-production of30days sludge anaerobic digestion is firstly increasing and then decreasing with the increase of bacterium’s amount, and reaches a maximum when the amount of bacterium is70ml/kg-sludge.(3) The SCOD content is increasing with microwave pretreatment time increasing at the same microwave power. And when the microwave power is1800W, and the pretreatment time is12minutes, the SCOD content reaches a maximum10750mg/L and dissolved rate is12.05%. At the same time, the dissolution rate increases linearly with the increase of microwave specific energy. After the microwave pretreatment with sludge, pH increases with microwave specific energy increasing and the greater the rate of increase with the microwave power increasing in pH. When the microwave power is1800W, and the specific energy is14400kJ/kg-TS, the cumulative amount of methane-production reaches the maximum133.42ml/g-VS representing the blank experimental group108.35ml/g-VS increasing23.14%, and the VS degradation gets the maximum rate35.47%.(4) Through a series of anaerobic digestion experimental studies, the eventually conclusions are that the best moisture content is91%, the best adding amount of bacterium is70ml/kg-sludge and the best pretreatment microwave power is1800W, and the best microwave specific energy is14400kJ/kg-TS in sludge anaerobic digestion. At the same time, these results provide some experimental basis for further experiments, field studies and anaerobic digestion.