MODELLING EFFICIENCY OF ON-FARM SAND FILTER SYSTEM IN MICROBIAL CONTAMINANT REMOVAL IN WASTEWATER, GHANA

Abstract

Wastewater irrigation without adequate safeguards has been noted to have serious drawbacks for human health and the environment. This study modelled the levels of microbial contaminants in wastewater used for periurban vegetable crop production and also assessed the efficiency of an on-farm sand filter system on the contaminants in the Zagyuri community of the Tamale Metropolis of Ghana. The study considered widely the selection of a very good filter material and sizing of the filter column. Varying lengths of filter columns and depths of filter material were used in the design of the on-farm sand filter columns. With average dry bulk density and particle density of the filter media being 1.58 gcm-3 and 2.66 gcm-3 the porosity was 39.4 %. Considering the environmental conditions and the results obtained, mathematical models were developed for selection of the filter size. The results indicated that longer filter columns were more efficient in the removal of microbial contaminants contained in the wastewater. The concentration of faecal and total coliforms as well as helminth eggs was 24,444 MPN/l, 56,930 MPN/l and 56 eggs/l for the wet season respectively. In the dry season however, faecal coliform recorded a mean concentration of 13,780 MPN/l, total coliform had 41,113 MPN/l whilst helminth eggs were 74 eggs/l. Sizing of filter column in the design of wastewater treatment system using mathematical models have been realized to be very important in the achievement of good results.