This study compares the performance of a pilot-scale combination of UASB and DHS system to that of activated sludge process (ASP) for the treatment of municipal sewage. Both systems were operated in parallel with the same sewage as influent. The study was conducted for more than 300 days, which revealed that organic removal efficiency of UASB + DHS system was comparable to that of ASP. Unfiltered BOD removal by both systems was more than 90%. However, UASB + DHS system outperformed ASP for pathogen removal. In addition, volume of excess sludge production from UASB + DHS was 15 times smaller than that from ASP. Moreover, unlike ASP, there is no requirement of aeration for the operation of UASB + DHS system, which makes it an economical treatment system. Considering the above observations, it was concluded that UASB + DHS system can be a cost-effective and viable option for the treatment of municipal sewage over ASP, especially for low-income countries.
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