Sequential high rate algal ponds operation for enhanced treatment of organic wastewater

Aim: Treatment of aquaculture wastewater often experiences fluctuations in chemical oxygen demand, causing insufficient performances. This study aimed to evaluate the stability of sequential high rate algal ponds in treating simulated aquaculture wastewater. Methodology: Two 1m3 high rate algal ponds were sequentially connected to treat simulated aquaculture wastewater, which was prepared through diluting solubilized food waste (chemical oxygen demand: 300 mg l-1). The hydraulic retention time was set at 10 days for each reactor. Results: More than 80% of influent organics and nearly 100% of nutrients (ammonium, nitrate, and phosphate) were removed from the effluent. While the oxygen demand removal in Pond 1 was incomplete around Day 8, Pond 2 was successful in removing untreated biodegradable oxygen demand from Pond 1 effluent. In addition, the sequential HRAP operation reduced bacterial biomass in the algal biomass ofPond 2 owing to the low organic loading on the second pond. Interpretation: These results indicate that sequential HRAP operation has advantages not only in stable wastewater treatment performance, but also in the valorization of algal biomass produced through aquaculture wastewater treatment.