Overview: full scale experience of the SHARON (R) process for treatment ofrejection water of digested sludge dewatering

A SHARON (R) system has been constructed at the Utrecht WWTP and at the Rot terdam Dokhaven WWTP. In the SHARON (R) process rejection water from dewate ring of digested sludge is treated for N-removal. It concerns a high active process operating without sludge retention. Due to differences in growth r ate nitrite oxidisers can be washed out of the system while ammonia oxidise rs are maintained, resulting in N-removal over nitrite. The SHARON (R) proc ess was selected in competition with several other techniques. The feed of a SHARON (R) system is concentrated, with ammonia concentration s ranging from 0.5 to 1.5 g N/I. The results show that conversion rates of 90% are well possible with N-removal mainly via the nitrite route. The proc ess was shown to be stable. Due to the high ammonium influent concentration s pH control is of great importance, preventing process inhibitions. The ac idifying effect of nitrification can be compensated completely by CO2 strip ping during aeration and by denitrification. Heat production by biological conversions is significant, due to the high inlet concentrations, and contr ibutes to the optimal operating temperature of 30-40 degreesC.