Performance of two types of biofilters for a rural stream

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This document is a report on the performance of two types of biotilters [‘or a rural stream. Two biofilters were tested on the field using the Sisai stream at Duasi 5km off Kumasi-Mampong road in the Ashanti Region of Ghana. One biotilter had a charcoal-sand arrangement whiles the other had crushed coconut fibre-sand arrangement. Physicochemical and microbiological studies were conducted between April 24th and July 6th, 2001 to assess the water quality of the Sisai stream which was known to be receiving discharges from a solid waste dump site situated about 1km away and also the performance of the two biofilters. The testing of the biofilters includes passing the Sisal stream (raw water) through the two sets of filters and again isolating the three various components namely sand, charcoal and crushed coconut fibre and testing them independently. For the Sisai stream, mean temperature and pH were 28.8C and 7.0 respectively. Mean turbidity was 67.54 FNU. Mean conductivity and total dissolved solids were I 82.48μS/cm. and 103.8mg/I respectively. Mean Chemical Oxygen Demand (COD) was 176.17mg/I. Nutrient levels were quite low (PO4-P 1.l9mg/l. NO3-N=0.8Omg/l. NO2-N=0.037mg/l). Mean faecal coliform counts and Iron concentration were 878 per 100ml and 0.17mg/I respectively. The two filters increase both the temperature and pH of the stream slightly. Both filters significantly improved physical parameter such as turbidity. Conductivity and total dissolved solids were not improved and even in some cases they were worsened. Although both filters could not completely remove all faecal coliforms in the raw water yet some appreciable removal efficiencies of 82. % and 63.3°/o for charcoal + sand and coconut fibre + sand were recorded respectively. It became evident that the charcoal-sand arrangement was very efficient in the removal of iron in water with a removal efficiency of over 80%. Ah series arrangement of such units especially the charcoal-sand arrangement type could be helpful for a rural community such as Duasi, which rely so much on this stream, but must be disinfected.
A thesis submitted to the Board of Postgraduate Studies Kwame Nkrumah University of Science & Technology Kumasi, in partial fulfilment of the requirement for the award of the degree of Master of Science in Water Supply and Environmental Sanitation, 2001