Full-scale application of the SHARON process for treatment of rejection water of digested sludge dewatering

At the Rotterdam Dokhaven WWTP the first full-scale application of the SHAR ON process has been constructed. In the SHARON process, rejection water fro m dewatering of digested sludge is treated for N-removal. It concerns a hig hly active process operating without sludge retention. The single tank reac tor is intermittently aerated. Due to differences in growth rate nitrite ox idisers are washed out of the system while ammonia oxidisers can be maintai ned, resulting in N-removal over nitrite. The SHARON process has been selec ted after comparison with several other techniques. The feed of the SHARON tank is concentrated, with ammonia concentrations over 1 g N/l. The first r esults show that conversion rates of 90% are quite possible with N-removal mainly via the nitrite route. The process was shown to be stable. Due to th e high inlet concentrations pH control is of great importance, preventing p rocess inhibitions. The acidifying effect of nitrification can be compensat ed completely by CO2 stripping during aeration and by denitrification. Heat production by biological conversions appeared to be significant, due to th e high inlet concentrations, and contributes to the optimal operating tempe rature of 30-40 degreesC.