Feasibility of using lysozyme to reduce excess sludge in activated sludge process

Lysozyme reaction was developed as a novel technique for minimizing the amount of excess sludge in the sequential batch reactor(SBR).In the present work,excess sludge taken from a SBR system was treated by lysozyme reaction and then returned to the reactor.The quality of the effluent water and characteristics of the activated sludge in the SBR were analyzed to determine the effectiveness of the reduction process.The results show that excess sludge production could be reduced to almost 100%in the first30 d of operation and could be reduced to further by 40%in the succeeding 20 d or so.In these time periods,the average removal efficiencies of the chemical oxygen demand and total nitrogen are 87.38%and 52.78%,respectively,whereas the average total phosphorous in the effluent is nearly 17.18%greater than that of the effluent of the reference system.After 50 d of operation,the sludge floc size is in the range of 20 to 80μm,which was smaller than the size prior to the start of the hydrolysis and the ratio of mixed liquor volatile suspended solids/mixed liquor suspended solids increases from 86%to 90%.