A review of constructed wetland on type, treatment and technology of wastewater

The performance of constructed wetland depends upon the types of constructed wetland, vegetation, applied hydraulic load, and media used in the bed. This paper describes the review of constructed wetland on type, technology and treatment of various types of wastewater generated such as textile waste, dairy waste, industrial waste, piggery waste, tannery waste, petrochemical waste, municipal waste, etc. The review summarizes the types of constructed wetlands considering media, vegetation, removal efficiency, construction cost, maintenance cost and land area requirement using life cycle cost analysis. The review compares how and why constructed wetland is a better option as per treatment efficiency, their payback period and cost-effective with the other wastewater treatment technologies. Further, there is no proper guidelines for the selection of media and vegetation in the constructed wetland. It is found that Typha Latifolia and Phragmites Australis have a better removal efficiency than other species. Lightweight Expanded Clay Aggregate (LECA), saw dust, zero-valent iron and gravels can be effectively used as a media for the removal of organic matter, phosphorus, sulphate and arsenate. Constructed wetland with low Hydraulic Loading Rate (HLR) performs exceptionally well and can remove 80%–91% Biochemical Oxygen Demand (BOD), 60%–85% Chemical Oxygen Demand (COD) and 80%–95% Total Suspended Solids (TSS). It requires a very low operation and maintenance than others. This review on constructed wetland further suggests research and development related to land area, media, plants, engineering design and automation of treatment units.