RECYCLING OF AQUACULTURE WASTEWATER USING CHARCOAL SLAG CONSTRUCTED WETLANDS FOR IRRIGATION OF HOT PEPPER

Abstract

The competitive use of water for various sectors of economy calls for the judicious use of the scare resource, hence, the need for recycling of wastewater. Therefore, there is need to fully utilize wastewater by reuse for irrigation and any other agricultural use especially in developing countries where treatment of wastewater is not a priority. The aim of this research work was to evaluate the performance of a designed charcoal slag constructed wetland in treating aquaculture wastewater and to determine the effect of treated wastewater on the growth and yield of hot pepper. The research was carried out at the Department of Fisheries and Aquaculture Technology, Teaching and Research Farm, the Federal University of Technology Akure. Experimental set up was divided into treatment unit consisting of a vertical flow charcoal slag constructed wetlands and another for planting of hot pepper which consisted of a randomized complete block of three treatments and nine replicates. The three treatments UT, TW and CT were irrigated with untreated aquaculture wastewater, treated aquaculture wastewater and groundwater respectively. Aquaculture wastewater from the Department of Fisheries and Aquaculture Technology Teaching and Research Fishpond Farm was treated in a vertical flow charcoal slag constructed wetlands planted with sacciolepsis africana and commelina cyannae for 5 days retention time. Raw wastewater and the treated wastewater from the constructed wetlands was sampled and the parameters determined were pH, Total Suspended Solids (TSS), Dissolved Oxygen (DO), Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), nitrate, phosphate, chloride and Electrical Conductivity (EC). The aquaculture wastewater characteristics, performance of the constructed wetlands, agronomic parameters, soil parameters and proximate analysis were measured and subjected to statistical analysis. The result showed that the charcoal slag constructed wetlands with sacciolepsis africana and commelina cyannae were capable of removing 50% of TSS, 88.4% COD, and 92.7% BOD. The pH and DO of the wastewater before treatment and after treatment ranged from 6.68 to 6.91 and 4.13 to 6.30 mg/l respectively. Thus, constructed wetlands have great potentials for treatment of aquaculture wastewater for irrigating agriculture crops. The responses of the growth of hot pepper plants to the various treatments showed that the average plant height and number of leaves for each of the treatments UT, TW and CT at 11 Weeks After Transplanting (WAT) were 40, 43 and 37cm and 242, 275 and 209 respectively. However, the highest average yield of 201.06kg/ha was obtained in treatment UT, while treatment TW and CT gave average yield of 164.25kg/ha and 88.17kg/ha. The result obtained provides information in prevention of environmental degradation through wastewater treatment and solving the problem of water scarcity for agriculture for optimum food production