Enhancement of a UASB-Septic Tank Performance for Decentralised Treatments of Storng Domestic Sewage

Abstract

The possibility of enhancing the process performance of the UASB-septic tank for treating strong sewage in Palestine by the means of inoculating the reactor with well adopted anaerobic sludge and/or adding a packing media to the upper part of the reactor, thus becoming an AH-septic tank, was investigated. To achieve those objectives, two community onsite UASB-septic tank and Anaerobic Hybrid (AH)-septic tank were operated in parallel at 2 days HRT for around eight months overlapping the cold and hot periods of the year, Palestine. The achieved removal efficiencies of CODtot in the UASB-septic tank and AHseptic tank during the first months of operation, coinciding the cold period and the subsequent months coinciding the hot periods were respectively “50(15) and 48(15)” and “66(8) and 54.73(7.9)”. This shows that the UASB-septic tank performed significantly better (p<0.05) than the AH septic tank after rather long period of operation. The difference in the CODtot removal efficiency was mainly due to the better CODss removal efficiencies in the UASBseptic tank. The removal efficiencies over the last 50 days of operation for CODtot, CODsus, CODcol and CODdis were “70, 72, 77 and 55%” and “53, 54, 78 and 45%” for the UASBseptic tank and AH-septic tank, respectively. Comparing the here achieved COD removal efficiencies with previously reported efficiencies of UASB-septic tanks operated in Palestine shows that the reactor performance has improved substantially by being started with well adopted anaerobic sludge but not by adding a packing media.