Effects of temperature and feed strength on a carrier anaerobic baffled reactor treating dilute wastewater

A carrier anaerobic baffled reactor (CABR), containing hollow-sphere bamboo carriers, was used to examine theeffects of organic and temperature shock loads for a constant hydraulic retention time. The relationships among themacroscopic observables (pH, COD and SS), catabolic intermediates (VFA) and microcosm alternation (TTC–DHA)were studied. A slight fluctuation in pH was observed, ranging from 6.5 to 7.5 throughout the experiments. TheCABR had a COD removal efficiency of 91% with an effluent suspended solids (SS) of 15 mg L−1 at 28°C and a feedstrength of 600 mg L−1 chemical oxygen demand (COD). The reactor could run steadily without souring due to thevolatile fatty acids (VFA) production (<150 mg L−1) and low VFA/alkalinity ratio (<0.23), although the effluent VFAconcentration increased with decreasing operational temperature. For a substrate low in nutrient, the microorganismsconverted the limited substrate into acetate to supply the essential nicotinamide adenine dinucleotide for cellularsynthesis. The tetrazolium chloride–dehydrogenase activity (TTC–DHA) of the attached biomass was higher thanthat of flock biomass at low feed concentration, whereas the result was the opposite at high feed concentration.Microorganisms with lower activity but higher shock resistance were dominant in the first chamber. Therefore, theCABR had high shock resistance and adaptability irrespective of temperature and feed strength.