Study On Thermal Hydrolysis For Sludge Reduction And Phosphorus Recovery In SBMBR

Sludge thermal hydrolysis technology is one of sludge disintegration technologies, which makes sludge stabilized, reductive and hygeian in a real sense. It is safe and reliable, environmentally-friendly and clean. In this paper, sludge reduction technology and phosphorus recovery technology were applied to treat the activated sludge. At the same time, the impact on operation efficiency of the SBMBR system was investigated.On basis of the theoretical analysis of thermal hydrolysis sludge reduction technology, the influence of thermal hydrolysis temperature, heating time, initial concentration of sludge on sludge disintegration effect was investigated. In the meanwhile, SAS response surface methodology was adopted to determine the optimum of heating temperature and time at different sludge concentrations, and the best experimental parameters in phosphorus recovery experiment. Compared with the conventional SBMBR system, the effects of sludge reduction and the operation performance of SBMBR thermal hydrolysis synchrotron sludge reduction and phosphorus recovery technology were studied, which was based on above-mentioned analysis. The main conclusions obtained from the research are as follows:(1) It was found that thermal hydrolysis could disrupt the sludge cells, release nitrogen and phosphorus substantially. With the extension of thermal hydrolysis time, TN、TP、PO43--P、NH4+-N、organic nitrogen increased rapidly and then stabilized. And PO43--P was the main composition of the released TP.(2) With the extension of the thermal hydrolysis time, temperature rising and increasing of initial sludge concentration, the effect of sludge disintegration was reinforced.(3) Thermal hydrolysis could decrease pH and dehydrogenase activity of sludge, and also could make the sludge settling property and dehydration property worse.(4) The increment of SCOD in sludge supernatant thought of the measurement index, when the initial concentration of sludge were6500(±300)mg/L、8500(±300)mg/L、10260(±300)mg/L, respectively, the optimal thermal hydrolysis temperature were85.7℃、83.9℃、87.8℃, respectively, and the best thermal hydrolysis time were97min、88min、105min, respectively.(5) Calcium phosphate precipitation method was adopted to recycle the phosphorus in sludge supernatant. The optimal conditions for recycling the phosphorus:with the mixed contact time of14.46minutes, initial pH value of10.37and Ca/P molar ratio of3.82.(6) Thermal hydrolysis sludge recirculation would reduce the amount of sludge significantly. Compared with conventional SBMBR, total amount of sludge in system were reduced37.6%、38.3%、40.7%, respectively, when the sludge concentrations were6500(±300) mg/L,8500(±300) mg/L,10260(±300) mg/L, respectively.(7) The sludge apparent yield coefficients of SBMBR with sludge reduction and phosphorus recovery process was nearly to zero in three phases, that meant that the effect of sludge reduction was100%in thermal system. Meanwhile it was0.2067,0.2111,0.2056gMLSS/gCOD respectively, in conventional SBMBR process.(8) Returning thermal sludge to system did not impact COD, NH4+-N, TN and TP of system effluent, which could met the level A of class1in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002).