Constructed wetland for improving the performance of a facultative pond treating high strength Urban wastewater

Abstract

The performance of a demonstration natural wastewater treatment system composed of a facultative pond and a horizontal flow constructed wetland (CW) treating raw wastewater from a University Campus has been studied for 5 years. The system achieved high removals for BOD (94 %), COD (78 %), TOC (72 %), suspended solids (96 %) and turbidity (85 %). Electrical conductivity was increased in the pond by 5 % and in the CW by 6 %, approximately. The effect of the CW on the performance of the system was significant for all the parameters analyzed as it improved the performance of the pond and provided robustness and stability under dramatic inflow changes, as well. In comparison to the other variables, ammonia-N removal for the system was low (34 %). The annually-based removal of this parameter was higher for the CW (25 %) than for the pond (12 %). These differences could be attributed to the higher surface area of the constructed wetland and the previous BOD reduction exerted by the pond. In fact, the higher removals were achieved for the years of lower BOD loads and vice versa.