Algal-bacteria raceway ponds for circular wastewater treatment

Raceway open systems are a highly promising, eco-friendly methodology for wastewater treatment. To assess how effectively nutrients and organic matter were removed from primary and secondary treated wastewater, two laboratory-scale open-raceway algal-bacteria ponds were used. The reactors were operated at organic loading rates (OLR) ranging from 29 to 95 and 9 to 38 g sCOD m³/d, for primary and secondary effluent, respectively. The hydraulic retention time (HRT) of both reactors dropped progressively from 5.5 to 2.2 d, and they thereafter ran at a HRT of 1.1 d. After 130 days, a high biomass concentration of around 2.2 g/ L was maintained with both substrates. Reactors were shown to be functional even at lower HRT levels by the quick removal of organic matter and nutrients. In less than 12 hours, the highly active biomass that was produced with both substrates resulted in the almost complete removal of organic matter and nutrients.
With its exceptional settling capabilities, the algal-bacteria biomass may settle in less than ten minutes. The algal-bacteria content of biomass was 18.3 to 16.5% for lipids, 72.5 to 72.6% for proteins, and 2.6 to 3.2% for carbohydrates. The findings of the present work show that syntrophic algal-bacteria biomass is effective for the high-rate treatment of municipal wastewater. The low operational cost as well as the potential nutrient recovery and biomass valorization make the algal-bacteria process a circular-green model for wastewater management .