A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1993

The anaerobic treatment of amino acid wastewater with the addition of molybdate was studied using upflow anaerobic filter reactors. The batch test was conducted to obtain the optimum concentration of molybdate for application to the anaerobic filter reactor. Higher methane production and complete inhibition of sulfate reduction were observed at 3 mM molybdate. Four laboratory scale upflow anaerobic filter with the total volume of 16.81 was used. The amino acid wastewater which contained Sg COD/l and 3g sulfate/I was used as the substrate. In the initial stage of phase I, no molybdate was added to the reactors for the period of 61 days. Then the reactors were fed with 4 different concentration of molybdate (l, 3, 5 and 10 mM). The complete inhibition of sulfate reduction was observed when the molybdate concentration was 3, 5 and 10 mM. Increasing methane production was observed only when the molybdate concentration was 3mM. But when the molybdate concentration was 5 or 10 mM, both methanogenesis and sulfate reducing bacteria were inhibited. The recovery of methane production was difficult after methanogenesis inhibition. In phase II, molybdate(3mM) was added at the time of start-up of the reactor to discourage the growth and development of sulfate reducing communities. Methane production of the continuous addition of molybdate(3mM) was better than that of the intermittent addition of 3mM (at a two day interval). Methane production was improved 5.3 times more than that of the control with the inhibition of sulfate reduction (72.7%). COD removal was not largely affected with or without the addition of molybdate in organic loading rates of 2.4 and 1.2 kg COD/m3.day with upflow anaerobic filter reactors.