The granular activated carbon serves as a sorbent particularly of recalcitrant compounds such as trace organic compounds and supports growth of specialised bacteria to improve their biodegradation. Sorbents particularly suitable for heavy metal removal (HM) are e.g. zeolites.
CaCO3 will further be added to control the pH and minimize remobilization of HMs. The vertical flow constructed wetland will be composed of several layers consisting of gravel, sand, and sorbents planted with local vegetation such as Cana indica.
The removal rates of modified wetlands and soil filters in polishing applications are particularly high for micro pollutants ranging e.g. around 65% for diclofenac and 80% for ibuprofen. Heavy metal removal ranges between 70 to 80%. Residual ammonia can be oxidised and reduces the oxygen depletion potential of the final effluent.