Effects of algal ponds on vertical flow constructed wetlands under different sewage application techniques

Algae can increase dissolved oxygen (DO) in water body by photosynthesis and affect the wastewater treatment performance of constructed wetlands (CWs). Two laboratory-scale vertical flow constructed wetlands combined with algal pond were designed and constructed to treat simulated wastewater in replicated experiments. The two units (half-vertical subsurface flow constructed wetlands and shallow algal pond-vertical subsurface flow constructed wetlands) could decrease chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) at low temperature condition (0-10 degrees C). The study showed that algal pond significantly improved TN and TP removal by 26.2-30.6% and 16.5-21.2% in CWs, respectively. The COD removal was only increased by 16.8-20.2% probably due to microbial carbon source accumulation originated from dead algae and algal debris. The study suggested that the designed new system with algal pond might be a green water treatment solution. (C) 2016 Elsevier B.V. All rights reserved.