Removal of nutrients from domestic wastewater using constructed wetlands: assessment of suitable environmental and operational conditions

Abstract

Constructed wetlands (CWs) offer an eco-friendly wastewater treatment technology primarily for decentralized locations. They support a dense growth of macrophytes which help in the reduction of water velocity, development of conducive microenvironments and provide adherence sites for microorganisms to develop biofilms. Several environmental and operational parameters are crucial for the efficient working of CWs wherein, suitable pH, temperature and dissolved oxygen (DO) are more significant. The performance of CWs has been enhanced significantly through effluent recirculation and artificial aeration. Removal of phosphorus proceeds via adsorption within media material, sedimentation, cation exchange, precipitation and uptake by macrophytes and the removal of nitrogen occurs mainly by microbial communities and macrophytic uptake. In colder climates, the bioaugmentation of microbial communities is required to increase the treatment efficiency. Various previous research findings showed several aspects of CWs that could potentially affect removal efficiency of the nutrients from the wastewater. However, maintaining suitable environmental and operational conditions for the effective operation of CWs remains a challenge. Therefore, the objectives of this review-based study are to provide the most favorable environmental conditions for the effective operation of CWs. Recent developments in operational and working parameters of CWs focusing on the selection of macrophytes and substrate material, carbon source, feeding mode, hydraulic loading rates and retention times are discussed. The study also provides effect of effluent recirculation, bioaugmentation of microbes, suitable C/N ratio and artificial aeration for the domestic wastewater treatment.