A novel sludge minimized biological nitrogen removal process for saline sewage treatment

摘要

This study reports a lab-scale evaluation of a new biological nitrogen removal process for salinensewage treatment, namely a SANI process (Sulfate reduction, Autotrophic denitrification andnNitrification Integrated process). The experimental system consisted of an up-flow anaerobic bednfor sulfate reduction, an anoxic filter for autotrophic denitrification using dissolved sulfidenproduced in the up-flow anaerobic bed and an aerobic filter for nitrification. The systemnsuccessfully operated for more than 180 days with an overall organic carbon removal efficiencynof 95%, in which, 82% removal was contributed by the up-flow anaerobic bed operating at a HRTnof 6 h, and 13% removal by the anoxic filter. An average COD removed /sulfate removed rationwas found to be 0.76 gCOD/gSO4 or 2.28 COD/gSO4-S further confirming that the organic removalnwas mainly achieved by the sulfate reduction. In terms of nitrogen removal efficiency, the SANInsystem was found sensitive to the recirculation rate between the anoxic filter and the aerobicnfilter. A recirculation rate of 3Q was found to be optimal for achieving 74% of the total nitrogennremoval. It was confirmed that the autotrophic denitrification was a major contributor to the totalnnitrogen removal in the SANI system. Sulfur balance analysis indicated that both thenaccumulation of elementary sulfur in the biomass and the loss of hydrogen sulfide were trivial.nDuring the entire operation period (330 days to date), no sludge was wasted from any reactors innthis system. This was further confirmed by the biomass balance simulation results that lownbiomass yields of sulfate reducing bacteria, autotrophic denitrifiers and nitrifiers contribute to thenzero excess sludge discharge.