Performance comparison of five alternative wetland-based ecotechnologies for on-site and decentralised wastewater treatment

Disposal of poorly-treated wastewaters from households and communities can pollute ground- and surface-waters, reducing water quality, and creating risks for human health and negative impacts on aquatic ecosystems. Constructed wetlands have the potential to reliably treat septic tank effluents to advanced secondary or tertiary standards with nil or low requirements for energy or mechanical equipment. Because they harness robust natural treatment processes and have extended residence times, they are likely to be more able to deal with fluctuations in usage and loading than mechanised package treatment plants (particularly those based on activated sludge processes), nd be less reliant on technical maintenance. However, they do tend to require larger land areas than mechanised treatment plants. In recent years a wide range of different constructed wetland formats have been developed, each with differing performance attributes, area requirements and establishment costs. Development and testing of these systems has generally been carried out at diverse locations under differing local conditions, so that comparative performance is hard to evaluate.