Abstract
The 6th generation of Down-flow Hanging Sponge (DHS-G6) reactor using newly developed hard sponge support material was applied to the post treatment of effluent of a UASB treating municipal sewage. The system was operated with real sewage as feed at a total HRT of 8.8h (6.8h in UASB & 2h in DHS) under an ambient temprature. The combined system was able to remove 97% of total BOD and 91% of TKN, producing a final effluent with only 8mgBOD/L and 4mgTKN/L at 25°C. However, it was observed that the concentration of the retained sludge was 18.1 gVSS/L-sponge which is less than that of the previous generations of DHS that used soft sponge for packing material. The obtained results showed a good contact efficiency between the sludge and the stream with actual HRT at 67 min. The oxygen concentration of the atmosphere inside the DHS reactor is similar to that of atmospere outside by natural oxygen supply, resulting in high concentration of DO was obtained in the final effluent at 8.1mg/L. Hence, high TKN removal can be performed by sufficient DO supply and high nitrification activity with 60mgN/g-VSS·day of the retained sludge.
