Full-Scale Denitrification Evaluations using Sugar Water, Glycerin, and Methanol in Denitrification Filters and Activated Sludge

The objective of this paper is to evaluate the effectiveness of sugar water, glycerin, and methanol as supplemental carbon alternatives in the post-anoxic zone and denitrification filters. This evaluation will enhance the industry's understanding of the capabilities of these products.The results of the investigations with methanol demonstrate that (1) sufficient anoxic SRT is required to sustain a population of methylotrophs, especially in cold weather (> 3 days at 14°C), and (2) high dissolved oxygen concentrations in the filter influent have resulted in excess dosing of substrate to consume excess oxygen prior to denitrification by facultative aerobes. During the sugar water pilot, an increase in secondary and plant effluent nitrate was observed in conjunction with a reduction in the mass of COD added to the BNR process due to insufficient dosing of the substrate. The Brenntag pilot demonstrates that glycerin compounds have promise as an alternative to methanol in anoxic zones of activated sludge basins. In addition, one gallon of Brenntag product was roughly equivalent to one gallon of methanol. However, due to insufficient dosing, the applicability of this product for denitrification filters requires further evaluation.The results of these pilot tests underscore the importance of DO control (to the extent possible) in filter influent to avoid overdosing an expensive chemical to the filters and manage aeration/energy costs.