Investigation of potato starch and sonicated RAS as alternative carbon sources for biological nitrogen removal

Abstract

High nitrogen discharge from wastewater is a major concern for the South Australian Government, primarily due to the negative impacts on the marine environment. Therefore, under the South Australian Environmental Improvement Program (SA EIP), all metropolitan wastewater treatment plants have been reconfigured to achieve enhanced nitrogen removal. Secondary treatment (denitrification processes) at the metropolitan wastewater treatment plants must be optimized to meet the discharge guideline of 10mg/L total nitrogen. However, secondary treatment at some plants is carbon limited (low C/N ratio), and external carbon supplementation is required to meet the discharge guideline. Molasses provides the current external carbon source at two plants. It is relatively inexpensive but other carbon sources, particularly industrial waste streams, may be more attractive. Potato starch and sonicated return activated sludge (RAS) are considered. Ongoing work will evaluate the benefit/cost of these alternative carbon feedstocks. Soluble carbon release (SCOD) from the two sources is quantified and preliminary results are presented. Initial results suggest that sonicated RAS may be an attractive substitute for the molasses.