The Study On Autothermal Thermophilic Micro-aerobic Digestion For Sewage Sludge By Dose Enhancement

Autothermal thermophilic aerobic digestion (ATAD) process is aneffective technology for sewage sludge stabilization, which achieves rapidremoval of volatile solids (VS), small land occupancy, efficient pathogeninactivation, low temperature adapted. The ATAD process has been adoptedby some WWTPs in Europe and North America. This thesis based on theown autothermal thermophilic micro-aerobic digestion process, andproposed the study on autothermal thermophilic micro-aerobic digestion(ATMAD) for sewage sludge by dose enhancement in order to makesludge stabilization more fast.This study based on the variations of microbial activity inhibition andthe influence in ATMAD system, investigating the removal of microbialactivity inhibition and sludge stabilization by Magnesium ammoniumphosphate precipitation. And the study determined the better dosing timeand dosing quantity in ATMAD process. The main conclusions were as follows.When the concentration of microbial activity inhibition (NH4+) wasabout1000mg/L, it was good for digestion. While the high concentration ofNH4+was2000mg/L, it was harmful for digestion.1000mg/L NH4+wasbeneficial to degrade SCOD, and SCOD of the digester adding1000mg/LNH4+was7000mg/L less than that of control in the end of digestion. While2000mg/L NH4+was harmful to degrade SCOD. In addition,2000mg/LNH4+was bad for microbial activity, in which microbial activity was theworst.38.37%of VS removal rate was obtained after12days digestion in the2nd day dosing digester that adding8.7g/L MgCl2·6H2O and6.7g/LNaH2PO4·2H2O, which achieved stabilization9days earlier than thenon-dosing digester. And VS removal rate was the highest (49.3%) in theend of digestion. There was about1500mg/L NH4+after dosing in the2ndday dosing digester, which was far less than control. The microbial activitywas stronger after dosing than control, make SCOD degrading faster. SCODof the2nd day dosing digester was about13000mg/L less than that ofcontrol in the end of digestion. Adding8.7g/L MgCl2·6H2O and6.7g/LNaH2PO4·2H2O ehanced sludge stabilization rate, and it would not lead toadverse effects by the meantime. If dosing much more, it would destroy pH and ORP, inhibit SCOD degradation. VS removal would not meet sludgestabilization.Therefore, after studying the influence of NH4+, the better dosing timeand dosing quantity, this thesis proposed the conclusions that adding8.7g/LMgCl2·6H2O and6.7g/L NaH2PO4·2H2O in the2nd day would ehancesludge stabilization rate.