The Study Of Hydrolysis Of Primary Sludge For Biological Nutrient Removal

Primary sludge hydrolysis can provide the soluble organics which can be a valuable carbon source to subsequent nutrient removal. By changing solids concentration of primary sludge, temperature and hydraulic retention time to determine the optimistic condition, under which the highest net VFA yield can be achieved. At the same time, biological hydrolysate of primary sludge was used as the carbon source in nitrogen-removal process to examine the effect of denitrification and compare it with the effects of denitrification with other kinds of carbon sources. The experimental results showed that:13.6% of net SCOD production in terms of initial sludge TCOD can be obtained in a semi-continuous completely mixed fermentor operating at 2.13% of SC, 3d of HRT, 5.5~6.5 of pH and 33 C of temperature. Under this condition, net VFA yield is 0.102mg VFA as COD/mg initial sludge TCOD or 0.198mg VFA as COD/mg initial sludge VSS;After the pre-treatment-disintegration of primary sludge, 20.59% of net SCOD production in terms of initial sludge TCOD can be gained in the same fermentor operating at 2.13% of SC, 3d of HRT, 5.5~6.5 of pH and 33 C of temperature. Meanwhile, net VFA yield can reach high as much as 0.152mg VFA as COD/mg initial sludge TCOD or 0.259mg VFA as COD/mg initial sludge VSS;The denitrification rate with hydrolysate was three times and twelve times as much as denitrification rates with wastewater and raw sludge respectively. Moreover, the denitrification rate with hydrolysate increased by 1/3, compared with the corresponding value with external carbon source. Products from primary sludge fermentation are the readily alternative carbon source for both denitrification and biological phosphorus removal.