Effect of Sewage Load on Microenvironment and Sludge Reduction Efficiency of Situ Biofilm Sludge Reduction System
The load has significant effect on sludge reduction efficiency and biofilm microenvironment. When the load was 1 ~ 4 kgCOD/ (m3• d), the sludge yield of the system changed little. When the system was greater than 4 kgCOD/ (m3•D), the sludge yield of the system increased doubly and the maximum load of the system was 4 kgMLSS/ (m3•D). At this time, the excess sludge yield is 0.0292 kgMLSS/kgCOD. The ORP aeration and aeration end of the biofilm were respectively (-74.73 ~ 187.89mV) and (-53.21 ~ 260.74mV). The corresponding biofilm aerobic and anoxic environment accounted for 9%, 17% and 91% and 83% respectively, forming a microenvironment of alternating aerobic / anoxic environment. When the load is 4kgCOD/ (m3•D), the change of ATP in sludge in the aeration stage and the shutdown stage is the largest, which is conducive to the dissipation of energy. To promote the sludge reduction, the COD, NH4+-N, TN and SS indexes of the effluent of the system all reached the first grade B standard of the pollutant discharge standard for urban sewage treatment (GB18918-2002).