Nitrogen and phosphorus removal by the Algal Turf Scrubber at an oyster aquaculture facility

Abstract

Integrated multi-trophic aquaculture is an aquaculture method by which waste of one species is used to produce another product. The purpose of this study was to determine rates of algal productivity using the inorganic nutrient waste from an oyster aquaculture facility, along with assessing the bioremediation potential of integrating an algal production system with the oyster aquaculture facility. Experimental-scale (1m2) Algal Turf Scrubber™ (ATS) systems were deployed at a commercial oyster aquaculture facility in Chesapeake Bay during summer 2012 and 2013 to determine algal productivity rates and assess the potential for remediation of inorganic nutrient release by the facility. Productivity rates of the ATS were high relative to previous studies, with a two-season average of 88.8galgae/m2/d. Total nitrogen and phosphorus removal rates by the ATS averaged 12.2g-N/m2/d and 0.25g-P/m2/d. An ATS with area of 640m2 would be needed to remediate all the nitrogen excreted by the oyster farm. A system of this size would produce 56.9kg of algae (dry weight), and remove 7.8kg of nitrogen and 151.6g of phosphorus per day during the summer growing season. The harvested algae is a resource that could potentially be used as biomass for biofuel production, food for livestock, or fertilizer.