Zero-Cost Operational Modifications Reduce Effluent Nitrogen and Chemical Consumption at the OWASA Mason Farm WWTP

摘要

OWASA owns and operates the 55 ML/day Mason Farm Wastewater Treatment Plant, whichrnwill be required to meet strict TN mass load allocations starting in 2018. The existing secondaryrnprocess provides limited denitrification, and OWASA will be dependent on denitrification filtersrnto meet the standard under historical operations. Operation of the aeration basins as a step feedrnprocess, which could be made at zero capital cost, was identified to reduce secondary effluentrnTN and chemical consumption. Step feed operation commenced in June 2010, and OWASArnimmediately observed a 50% reduction in effluent TN. Alkalinity feed has been reduced byrn55%, and alum and acetic acid feed have been reduced by 25% and 33%, respectively, sincernimplementation of step feed, resulting in $260,000/year of chemical savings. Operation in thernstep feed mode of operation is expected to save over $800,000 per year over 20 years once thernstrict TN limit is in force.