The Research Of Electrochemical Pretreatment Methods To Promote Anaerobic Digestion Performance

Sludge is a byproduct produced in the wastewater biological treatment,which contains a large number of microbial bacteria.According to the requirements of Ministry of Housing Urban-Rural Development of the P.R.C.,the sludge must be stabilizing treated before landfilling or land utilization in accordance with the details in “Discharge standard of pollutants for municipal wastewater treatment plant”(GB18918-2002).Sludge stabilization methods include biological stabilization,such as anaerobic method and aerobic method,chemical stabilization,and physical stabilization.Especially,the anaerobic digestion is recommended as the first choice for sludge stabilization treatment technology in large and medium-sized wastewater treatment plants by the Ministry of Housing Urban-Rural Development and the Ministry of Environmental Protection of the P.R.C.,owing to the advantages of the low operating cost,safety,reliability and energy recoveryWith the stricter environmental laws and regulations,anaerobic treatment facilities will obtained a quick popularization and applications in the next few years.However,the traditional anaerobic digestion method presents quite lots of shortages,such as long residence time,huge facilities area,and low ratio and volume in gas production.All the disadvantages are mainly subject to the low hydrolysis rate of the sludge,low biodegradability of the solids,long consuming time of complete digestion,which are need to be investigated and resolved further.This paper conducted research from two aspects,one is strengthening the activity of anaerobic microbe system in the process of sludge digestion,and the other one is changing the properties of the sludge itself.With the guide of basic theory studies,the purpose of engineering application,the aim of increasing the efficiency of the sludge anaerobic digestion,it provided a good technical support to reduce the sludge digestion facilities accommodation,improve the level of sludge stabilization.The research results of this subject will improve the efficiency of the treatment of sludge stabilization facilities;reduce the land covering in the newly built sludge anaerobic digestion facilities,with significance in strategy and tactics.This paper studies the methods on the improvements of the performance in sludge anaerobic digestion through electrochemical pretreatment technology and adding non-hazardous chemicals.It investigated the sludge electrochemical properties changes before and after electrochemical treatment,through altering the sludge storage time in electrochemical pretreatment,in order to obtain the optimal combination with the electrochemical pretreatment and sludge anaerobic digestion,further research was carried out in the pilot test.Experiment results showed that,after electrochemical pretreatment,VSS and VSS/TSS of sludge has decreased,indicating that the original organic compounds in the sludge was degradation;And after electrochemical treatment,SCOD,TN,TP and ammonia nitrogen concentration of sludge supernatant was increased,indicating that microbial cells have been destroyed.The optimal process parameters of electrochemical pretreatment were: electrochemical treatment voltage of 20 V,plate spacing of 2 cm,electrolytic time 30 min,the sludge concentration is 30 g/L.Based on optimum electrochemical pretreatment parameters,the effects of chemical substances on the pretreatment effect were studied by adding chemical substances such as urea,sodium chloride and sodium hypochlorite solution.The effects of adding sodium hypochlorite on electrochemical pretreatment were studied.When the initial concentration of Na Cl O was 0.4g / L,the optimal conditions were as follows: electrolysis voltage 20 V,electrolysis time 45 min,plate spacing 2cm,the initial p H value of sludge was 8.0,the initial concentration of sludge 30 g / L.The couple mode of pretreatment and anaerobic digestion of sludge was studied.The effects of different coupling methods on the anaerobic digestion efficiency were investigated by placing and inoculating fresh sludge,using the properties of the supernatant and the yield rate as evaluation indexes.The results showed that placing the electrochemical pretreatment sludge for 10 hours,the active oxide in the sludge could be attenuated.Under the premise of ensuring the quantity of microorganism,the effect of electrochemical pretreatment was further promoted by inoculation of fresh sludge,which further promotes the anaerobic digestion and the production of marsh.When the ratio of sludge after electrochemical pretreatment was 30%,the anaerobic digestion gas production was the best,and the cumulative gas production was 859.87 m L / g VSS,which was 1.80 times of that of fresh sludge and 2.59 times of that of uninoculated sludge.In the pilot test of electrochemical pretreatment,compared with nonelectrochemical pretreatment,the anaerobic digestion with electrochemical pretreatment achieved the requirements of sludge stabilization 9d in advance.After anaerobic digestion for 39 days,the gas production increased by 1.83 times,and the methane production increased by 0.45 times.