Effect of media variation on the removal efficiency of pollutants from domestic wastewater in constructed wetland systems

Abstract

Constructed Wetlands (CWs) are a group of effective and environmentally safe wastewater treatment systems that combine chemical, physical and biological treatment processes. These processes regulate the removal of inorganic, organic and biological pollutants from wastewater. This work presents a pilot field study carried out at Samaha wastewater treatment plant located at Al-Dakahlia province, Egypt. The present study addresses the use of some field wastes (e.g. plastic, rubber and polystyrene foam) as low cost alternative substrates to the common media in the constructed wetlands. It was noticed that after mixing the traditional used media (gravel, plastic or rubber) with polystyrene foam, the removal efficiency of pollutants was remarkably enhanced. The removal efficiency was followed by noticing the levels of biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonia and phosphate in the treated wastewater. Data obtained indicated that, the removal efficiency of COD increased from 71% to 88% while for BOD and the total suspended solids, it was enhanced from 72 to 88% and from 83 to 88.5% respectively. For ammonia, the removal percentage increased from 66 to78% and phosphate reduction raised from 78% to 85%, while a slight modification of total coliform from 98.4–98.6% was found. The effect of flow rate on the removal efficiency is also studied and obtained results proved that the efficiency is inversely proportional to the flow rate and the best flow rate in this work was 2 m3/day. This improvement in removal efficiency was established based on comparison with regular treatment efficiency reported at Samaha wastewater treatment plant.