REMOVAL OF FORMATE FROM WASTE-WATER BY ANAEROBIC PROCESS

Formate in wastewater was effectively removed at 37-degrees-C by the u pflow anaerobic sludge blanket (UASB) process. This was accomplished b y keeping the recycle ratio at 3.0 and by lowering the pH of incoming wastewater to pH 3.8. The COD removal efficiencies were 97-98% at load ing rates of 10-20 g-COD.L-1.day-1, but were reduced to 86-90% at 29-6 5 g-COD.L-1.day-1. When the loading was further increased to 77 g-COD. L-1-day-1, the reactor abruptly failed due to the sudden decrease of t he pH. About 94% of COD of the formate removed was converted to methan e with a sludge yield of 0.05 g-VSS.g-COD-1. The small sludge granules settled satisfactorily and had a maximum specific methane production rate (SMPR) of 2.06 g-COD.VSS-1.day-1. The specific methane activity ( SMA) of granules using formate as substrate was 2.90 g-COD.g-VSS-1.day -1; but the granules were unable to degrade other fatty acids. Microsc opic examinations indicated that the granules mainly comprised Methano bacterium formicicum-like bacteria, plus a small amount of Methanococc us vannielii-like bacteria, and an unknown species of bacterium.