DEGRADATION OF STARCH PARTICULATES IN A HYBRID REACTOR

The study was conducted over 265 days to study the feasibility of removing starch particulates from wastewater using an 8.5 L reactor which was a hybrid between the upflow anaerobic sludge blanket (UASB) and the anaerobic filter reactors. At pH 7.2-7.5 and 37 degrees C, the reactor was effective for the removal of chemical oxygen demand (GOD) from wastewater containing starch particulates equivalent to 5000 mg/L of COD with 12 hours of retention time, corresponding to a loading rate of 10 g-COD/L.d. Despite their insoluble nature, the starch particulates did not cause noticeable adverse effects on the granulation of biomass, probably due to its easy-to-biodegrade nature and the cautious startup strategy. About 5.8% of COD in wastewater remained in the effluent, 82.5% was converted to methane, and the remaining 11.7% was converted to granular biomass with an average sludge yield of 0.09 g-VSS/g-COD. The granules exhibited a layered microstructure. The methanogenic activity of the granular biomass was 0.86 g-methane-COD/g-VSS.d in the reactor, which was considerably lower than the 1.96 g-methane-COD/g-VSS.d measured in serum vials with an abundant supply of substrate, suggesting that further increase of loading rates was possible for the hybrid reactor.