UNS: Selection of Granules in Activated Sludge for Nutrient Removal and Phosphorus Recovery

University Of Washington, Seattle WA

Investigators

Abstract

1510665 Stensel This research project merges two major needs in wastewater management, the recovery and reuse of phosphorus, a nonrenewable essential element for all life, and the need for nitrogen and phosphorus removal to protect surface water quality, with a dramatic development in aerobic granular sludge that offers many advantages over the older more established flocculent activated sludge process. The research objectives are centered around the evaluation of granular sludge to be developed in two process design innovations that facilitate enhanced phosphorus biological removal by retrofitting of existing activated sludge facilities to granular sludge. The work is transformative in that it is a totally different approach to improve nutrient removal of conventional biological process applications while providing a cost effective phosphorus recovery and a sustainable engineering approach. The project will benefit society in the area of food production and economics by providing phosphorus recovery for reuse in an immediate area and to provide a means to slow down the long-term depletion of phosphorus reserves. The key research needs are related to process conditions that select for granular sludge and affect the granular sludge microbial and physical characteristics. Key specific objectives are as follows: 1) test hypotheses on how to select and maintain granular enhanced phosphorus biological removal sludge in the retrofit designs, 2) determine the microbial ecology and long term integrity of granular sludge produced, 3) determine the effect of the relative and uncoupled flocculent and granular sludge solids retention times and dissolved oxygen control strategy on their microbial populations phosphorus and nitrogen removal abilities, and, 4) determine the rate of phosphorus release and attainable phosphorus concentration possible in a waste sludge phosphorus stripping tank. To meet these objectives laboratory reactors will be designed and operated to simulate a granular sludge system for phosphorus removal only and the use of granular sludge in an activated sludge biological nutrient removal system retrofit. Fundamental molecular biology technique will be used to evaluate the granular sludge microbial populations and microscopic and other physical test methods will be used to assess the granules size, density and strength. Process performance data for enhanced phosphorus biological removal, nitrification, and denitrification will be obtained. The proposed project will be important for attracting under represented and female students to a career in engineering with interest in solving important issues of water supply, environmental protection and resource recovery for the public. The project through collaboration with an EPA nutrient management center and the Water Environment Research Foundation will advance new cost effective technology to a wider audience including design engineers, regulators and utilities. A very important impact of the project is in providing a greater opportunity for recovery of phosphorus, a finite and essential element for all life.