Constructed Wetland for Water treatment
Constructed Wetlands for water treatment
Constructed wetlands utilise natural processes which involve soil, vegetation, and microbes to treat water. Wastewater, stormwater or leachate flows either horizontally and/or vertically through a basin which contains wetland plants. Wetlands are well-known for the effective reduction of Total Suspended Solids (TSS), Biochemical Oxygen Demand (BOD), Phosphorus, Nitrogen, and Faecal Coliforms. They are considered simple and robust wastewater treatment systems, with lower overall maintenance, costs, and energy requirements than typical treatment. They also provide many additional benefits compared with conventional systems including the ability to accommodate fluctuating loads, provide habitat and aesthetic values, and provide additional options for water storage and reuse. Ecoteam designs vertical, horizontal and bioretention wetlands for stormwater, wastewater and all types of industries. Horizonal Wetlands can have either free water surface and/or subsurface flow.
Free Water Surface Wetlands
Free Water Surface (FWS) wetlands are usually designed with a single sealed shallow basin or multiple basins in series, containing natural soil with a water depth of 200 mm to 400 mm. Emergent wetland vegetation is established in dense stands within the water column. FWS wetlands are commonly used for tertiary treatment of municipal wastewater, mine drainage water and stormwater treatment. These wetlands have the advantage of having lower construction and long-term maintenance costs; however, they require large areas for adequate treatment. They are typically designed with length to width ratios from 2:1 to 6:1, to achieve expected performance with reduced short -circuiting. FWS wetlands typically contain an aerobic layer at the surface and anerobic conditions in the deeper substrate layer, which enhances the treatment processes. When managed correctly FWS wetlands support a wide diversity of aquatic animals in a well-balanced ecosystem which predates mosquito larvae.
Horizontal Subsurface Flow Wetlands
Horizontal Subsurface Flow Wetlands (HSSF) are typically densely-vegetated basins filled with a permeable substrate with water depths of up to 400 mm. Wastewater flows though the basin from the inlet and is filtered through plant roots before being discharged at the outlet. A range of materials can be used for a permeable substrate; however, gravel ranging from 5-20 mm is generally used as fine-pored media such as soil can cause clogging. HSSF wetlands maintain a water level below the substrate, which reduces odour, human contact and the breeding of mosquitoes. This makes HSSF constructed wetlands a popular wastewater treatment device for village scale wastewater treatment