Nitrifier Growth Rate Testing Proves to be a Valuable Tool for Assessing Impacts of an Industrial Load on a Proposed Biological Nutrient Removal Treatment System

This paper describes a low food-to-microorganism (F/M) nitrifier growth rate study conducted at the Hopewell Regional Wastewater Treatment Facility (HRWTF) to measure the maximum specific nitrifier growth rate of a combined domestic and industrial waste stream that is proposed to be treated in a segregated biological nutrient removal (BNR) treatment system. The key purpose of the study was to confirm design parameters used in preliminary sizing of the biological treatment tanks for a proposed BNR treatment system. The assumed maximum specific nitrifier growth rate (μmax of 0.8 day−1) was determined based on initial screening done ten years ago and supported by nitrification inhibition screening batch tests conducted as part of this study. Results from this study illustrate that, although the average maximum specific growth rate supported previous findings and design assumptions (excluding inhibition data), transient inhibition is a concern even with low industrial percentages in the segregated waste stream and could significantly affect nitrification rates.