Abstract
A novel wastewater treatment system was proposed by a combination of an UASB reactor and an aerobic biofilm reactor. A laboratory-scale combined system was operated for 214 days by feeding a synthetic low-strength wastewater (300mg-CODcr⋅L-1, simulating domestic sewage). The combined system exhibited a very satisfactory performance in organic removal, achieving above 92% CODcr removal at a HRT of only 4.5h under temperature range of 25°C through even 3°C. The system also accomplished a significant extent of nitrogen removal, more than 68% of T-N removal at above 7°C at a circulation ratio of 2 (the effluent from the aerobic biofilm unit was recycled to the UASB unit), and major organic removal can be attributed to denitrification, rather than to methane production or to sulfate reduction.
