Combined Artificial Wetland and High Rate Algal Pond for Wastewater Treatment and Protein Production

Abstract

The potential to optimize wastewater utilization, whilst achieving satisfactory nutrient removal has been investigated through a simple system combining an Artificial Wetland with a High Rate Algal Pond (HRAP). Receiving septic sewage at a surface loading equivalent to 13.5 cm/day the Wetland achieved COD removals of 59.2%, NH4−N of 34,6%, PO4−P of 31.9% and SS of 78%. The HRAP selectively cultivated an easily harvestable filamentous green alga through a combination of short hydraulic residence times (< days), and microscreens as selectors over the effluent stream. Passage of the effluent through this stage permitted COD removal to increase to 79.4%, NH4−N to 82.8% and PO4−P to 54.1%, whilst generating a highly proteinaceous (42% by wt) biomass at a rate of approximately 50 tons/hectare/year. This paper discusses the performance of the pilot scale facility over a twelve month period, identifying biological and operational influences on the system, and the physiological mechanics by which the wastewater treatment is accomplished.