EFFECTS OF COUPLING ELECTROCOAGULATION WITH DUCKWEED BASED TREATMENT PROCESS IN THE MANAGEMENT OF INDUSTRIAL TEA EFFLUENT

Abstract

Discharge of untreated waste water into the receiving water bodies could cause ecological disruption which include but not limited to eutrophication. Any continued deterioration of water quality and quantity may lead to the decline in aquatic biodiversity. Tea factories have been singled out as industries that have a potential to compromise ecosystems with their waste waters. In spite of the industries‟ attempt to alleviate their wastes water problems with constructed wetlands, there is still a lot of discharge of effluents with high level of colour and other contaminants coupled with long treatment time needed. This study sought to assess the effects of coupling electrochemical technology with duckweed based treatment technology in the management of industrial tea effluent. The study used a complete block design, 36 basins were arranged into two distinct blocks of 18 basins each, i.e. raw effluent block (RE) and electrochemically treated effluent block (EC). Each of the blocks (RE) and (EC) were further sub divided into two sets of 9 basins each, one set of (RE) basins were treated with 50gms of duckweed plants Lemna spp, while the other set remain untreated. Similarly, EC treated effluents of 18 basins were sub-divided into two sets of nine basins each. One set of EC pre- treated effluent was further treated with 50gms of duckweed plants Lemna spp while the second set of nine basins were untreated It was found out that electrocoagulation process reduced colour intensity of industrial tea effluents by 53.6%, BOD by 55.0% and electrical conductivity by 32.5%. In addition, electrochemical process reduced the concentration of nitrates, nitrites, and total phosphates by 94.7%, 80.5% and 69.90%, respectively. Further, it was found that electrochemical process coupled with DWT reduced effluent retention by 5 days. The relative growth rate of duckweed plants grown on electrochemically pre-treated tea effluents was higher (62.7%) than those in non-electrochemically treated effluent (50.8%) after 15 days. The electrochemical process coupled with DWT in the treatment of tea effluents was found be cost effective and efficient in the management of tea effluents. EC technology also showed the ability to remove toxins that inhibit the growth of duckweed plants as well as its utilization of other nutrients. It is recommended that EC treatment should be integrated with plants of different species and rooting systems to achieve better results in nutrients uptake. Moreover, a combination of different plant species with different root structures be selected so that effective extraction of N and P lodged in the bottom of the basin is achieved. In addition, the EC reactor should be designed to automatically separate precipitated organic matter that would otherwise have undergone oxidation resulting in more colour formation.