Study On The Sludge Reduction By Electrochemistry

Sewage treatment process is the procedure which turns pollutants into solid waste or gas. The sludge, as solid waste, produced by sewage treatment plant, if not disposed properly, will bring secondary pollution to environment. Presently, based on that waste water treatment can make large numbers of excess biological sludge, the treatment and disposal of sewage sludge should be done in order to prevent the pollution of the environment. However, it is difficulty to dispose sludge, there is no appropriate method to treat it, the outlet of sludge is more anxious. Thus it can be seen, it has important meaning to reduce the disposal cost of the sewage treatment plant and exert environment protection action sufficiently by solving the problem of the disposal of sludge primely.The paper base on the principle of "cleaner production", study the feasibility of sludge reduction by electrochemical method, and make systemic research on sludge reduction by electrochemical method, include three parts:(1) Study on electrochemical dissolution of the sludge microbial cellThe static tests study the changes of COD_cr, ammonia contents of electrolytic sludge mixture under different electrolytic parameters, validate the effect of dissolved cell by electrochemical method and the feasibility of sludge reduction by electrochemical method, then determine the best electrolytic sludge parameters.(2) Study on the impact of electrochemical sludge reduction on SBR processThrough the lab-scale tests, to study the sludge yields cut of the activated sludgetreatment system under different electrochemical processing capacities, and the removal efficiencies of COD_cr, BOD₅, ammonia in sewage treatment system, to determine the optimal electrochemical processing capacity; then through SBR consecutive tests, make further study of the electrochemical activity of sludge reduction on sludge indicators (sludge yield, SV,MLVSS, SOUR) and the organics, nitrogens, phosphorus and other indicators.(3) Study on electrochemical sludge reduction of microbial populationStudy on the microbial population structure and metabolism, and changes in microbial population and the characteristics of metabolism after the electrochemical sludge reduction.The results show that:(1) When the electrolytic plates use graphite anode and cathode plate, electrochemical reaction can play a role in cell dissolved, the concentration of COD_cr and ammonia in the mixture of sludge increase; the best parameters of sludge reduction by electrochemical method are: the reaction time is 60min, plate spacing of 2.3cm, plate voltage of 36V, electrolyte is seawater and the capacity of the sludge volume accounts for 7.5 %, sludge concentration of 8g/L;(2) Electrochemical method used in sludge reduction, compared system and electrochemical capacities of sludge volume of 1/15, 1/12, 1/9, 1/6 the average sludge yields are 1.54,1.38,1.30,1.23,1.12 gMLSS/gCOD, the average effects of sludge reduction can reach 10%,16%,19%,25%; COD_cr average removal rates are 90.3%, 89.6%, 88.9%, 87.7%, 84.3%; BOD₅ average removal rates are 94.8%, 94.2%, 93.2%, 92.5%, 89.7%; NH₃-N average removal rates are 86.9%, 84.1%, 80.1%, 74.5%, 68.7%. COD_cr, BOD₅, NH₃-N removals as the sludge electrolysis increase gradually decrease, electrolysis capacity of 1/6 of the sludge volume the effluent COD_cr, BOD₅, NH₃-N concentrations increase significantly, the removals decrease significantly, to be the upper limit of electrolysis;(3) SBR consecutive test, the average sludge yield of electrochemical sludge reduction system is 1.26gMLSS/gCOD, the average yield of the compared syetem is 1.61 gMLSS/gCOD, average sludge yield can reduce 21%. Electrochemical sludge reduction act can improve the performance of sludge settlement, increase PO₄^3--P removal 6.1%, but the removal of COD_cr lower 1.1%, the removal of BOD5 lower 1.2%, the removal of NH3-N lower 6.9%;(4) In the electrochemical sludge reduction system, the number of protozoa and metazoan reduce, the number of filamentous also reduce, sludge floc structure more closely; microbial activity affected by electrochemical products is slightly lower, carbon metabolism also have small changes, but the microbial community characteristics of metabolic similar, and there is no major change. To sum up, electrochemical method can be played on the microbial cell chemical dissolution role, as sludge reduction technology is feasible. Electrolytic chemical sludge reduction can not only reduce sludge production, but also improve the performance of sludge sedimentation, and have little effect on the biological treatment. Electrochemical method can be used as a sludge reduction technology in sludge process.