Nutrient removal from agricultural drainage water using algal turf scrubbers and solar power.

The objectives of this study were to determine nutrient removal rates and costs using solar-powered algal turf scrubber (ATS) raceways and water from an agricultural drainage ditch. Algal productivity using daytime-only flow was 3-lower compared to productivity using continuous flow. Results from this and other studies suggest a non-linear relationship between flow rate and nitrogen removal rates. Nitrogen (N) and phosphorus (P) removal rates averaged 125 mg N, 25 mg P m(-2) d(-1) at the highest flow rates. Nutrient removal rates were equivalent to 310 kg N and 33 kg P ha(-1) over a 7 month season. Projected nutrient removal costs ($90-$110 kg(-1) N or $830-$1050 kg(-1) P) are >10-fold higher than previous estimates for ATS units used to treat manure effluents.