A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1987

The upflow filters were operated to study the denitrification process with respect to the effects of substrates corresponding to different M/N ratios and time over the treatment efficiency. Over 95% of denitrification efficiency was achieved even if M/N ratio was as low as 2. 5; but the optimum M/N ratio for packed-column denitrification was found to be equal to 2 .9. The unit also satisfied the treatment of high loading, of which nitrate-N and methanol concentrations in feed were respectively 200 and 600 mg/L, with a 4 -hr HRT. The gas chromatographic results showed that denitrification and methane production happened together. Since the methane production was found to occur in a proportion to COD loading even with only 1.5-hr HRT, resulting in a low COD effluent, it is proposed that an additional post aeration, after an upflow packed-bed denitrifying unit, would not be required. It was found that the granular biomass was, not only attached to the media surface, but also densely entrapped within the void space. This formation would result in a better treatment efficiency, due to much higher ' self' surface areas for more attachment. The bio-granules were found to contain 50% of volatile solids.