Sludge Reduction By Lysis-Cryptic Growth Combined With Sludge Disintegration Using Quicklime

Excess sludge disposal has become a global environmental problem need to be solved urgently. A variety of sludge reduction technologies have been widely studied to alleviate this situation. Lysis-cryptic growth system had been regarded as a promising measure in sludge reduction, while conventional sludge disposal method had environmental and health risks. The way to disintegrate sludge is critical. The present studies are ozone/ultrasonic, Cl O2/ultrasonic and high pressure homogeneous cell, but all of them have the disadvantage of high energy consumption and high investment. With sodium hydroxide as alkaline regulator thermal-alkaline pretreatment of sludge was a cheap way relatively, which was commonly used for sludge anaerobic digestion to produce hydrogen or methane. However, it was rarely used in the sludge reduction in the way of lysis-cryptic growth.This research determined the optimal parameters of lysis rate, discussed the effect of sludge reduction and investigated the effect of returned sludge, which was on the basis of the lysis-cryptic growth technology and the thermal-alkaline pretreatment of sludge. However it was different to use quick lime as alkaline conditioning agent, which consumed more time.Response surface model, which was that lysis rate was the function of Temperature, p H and Reaction time, were determined. Experimental data was analyzed with the aid of response surface models to determine the identified optimum conditions of maximum quantity of SCOD(5240 mg/L)/TP(58.1 mg/L)/NH4+–N(81.7 mg/L)/NO3--N(73.8 mg/L), which were obtained as follows: T=76.5?/t=182 min/p H=11.6. In this case, lysis rate was between 40% and 45%. In consideration of the organic nitrogen, the TP: TN: COD of 1:5:100 indicated that the released intracellular material released is readily biodegradable.After thermal-alkaline disruption, 65.6% of excess sludge can be returned to the SBR with a 45.94% reduction of discharged sludge. The observed biomass yield of the lysis-cryptic growth system can decrease 49.01%, while the sludge attenuation coefficient has an increase of 0.0338 d-1.Similar COD and NH4+-N concentrations were observed in the effluents of both the lysis-cryptic growth system and the control system. A 33%increase of phosphorus was observed in the lysis–cryptic system. These parameters complied with the first-class A discharge standards for sewage treatment plants in China. In addition, TP complied with the first-class B. During the first 40 days of the operation, the settling ability of the sludge in lysis-cryptic growth system is worse than the control system. The endogenous respiration dehydrogenase activity of activated sludge in lysis-cryptic growth is 3 times more than in the control group. In addition to these, there was an obvious ecological succession of microbial community that the percentage of Bacteroidetes phylum was gradually decreasing, while Proteobacteria phylum was increasing.