Organic Carbon Removal from Domestic Sewage using Constructed Mangrove Wetlands in Coastal Areas of Dar es Salaam City, Tanzania

Abstract

Mangroves store up to five times as much organic carbon as tropical upland forests. This article provides some insights on organic carbon removal from domestic sewage in constructed mangrove wetlands in coastal areas of Dar es Salaam City, Tanzania using standard methods. The wetlands were operated in intermittent flow and batch modes. The one that was operated in an intermittent flow mode showed higher removal rates as compared to the one that operated in batch mode. About 49% of organic material measured as COD was removed from sewage in the wetland cell operated in the intermittent flow mode. The lower removal rates resulted from frequent interruption of the wetland system by uncontrolled natural tides at the site and shorter retention time of three (3) days cycles of flooding with sewage and drying-up of mangrove wetland. The constructed mangroves wetlands have a good capacity in removing up to 80% of organic carbon material from sewage when a more controlled environment and a longer retention time of about 5 to 15 days are employed. If adjustments will be made, they are recommended to be applied as treatment technologies for sewage in coastal areas.