Coffee wastewater treatment using horizontal subsurface flow constructed wetland by gravel and canna indica

Abstract

Coffee processing wastewater is one of the major agro-processing wastes that put high pollution pressure in coffee growing and exporting countries affecting water and human health .The Mohammed Jamal’s wet coffee processing industry in Jimma apply no or low efficient technologies for treatment due to lack of economic and technological feasibility. The aim of this study is to investigate the nutrients removal capacity of Canna Indica based Horizontal Subsurface Flow Constructed Wetland (HSCW) made of Gravel.The experimental set up of constructed wetland (CW) with dimension of 2.8 m (length) ,0.8 m (wide) ,and 0.65 m(depth) has been done at Jimma institute of Technology (JiT) .Locally available plants ,Canna Indica were planted in two of three cells while the remaining unplanted cell served as the control .Monitoring of wetland influent and effluent wastewater was carried out every 24 hours with in HRT of 4 day.The response surface methodology (RSM) based on central composite design was employed for data analysis was found to be effective tool to evaluate, optimize the effect of operating parameters on the responses, and analysis of variance (ANOVA) with 95% confidence limits was used to determine the significant , the validation of the model, the significant of independent variables and their interaction effect on the responses.The study revealed successful treatment of the wastewater by the wetland in term of turbidity ,TSS,COD,NO3 - and PO4 3- effluent compliance with world health organization (WHO) discharge standards except COD. Average removal efficiencies were( 79.8 %,45.4 %) for turbidity ,(78.2 % 61.3 %),for TSS,(47.9 %,52.1 %) for COD ,(30.3 %,29.8 %) for NO3 -, and (83.73%,77.6 %) for PO4 3 for planted and unplanted cells respectively .Thus ,planted cell achieved the highest removal efficiency than unplanted cell.This study concluded that vegetated horizontal subsurface flow constructed wetland (HSSF-CW) was found to be more effective for removal of pollutants from coffee processing wastewater than non vegetated horizontal subsurface flow constructed wetland