Development of a simplified slow sand filter for water purification

This study reports the development of a simplified slow sand filter with granular carbon for water purification which could be used for teaching. It was fabricated using transparent perspex glass for the filter chamber, PVC pipe, fine sand, coarse sand and granular carbon for removal of physicochemical and pathogens in the contaminated water. The filter has a50 litres storage tank from which raw water flows into the filter chamber through the pipe. The filter chamber (30 by 30 cm and 100 cm high) has 10 cm layer of granular carbon, three sand layers as the filter bed (30cm depth with grain size 0.20 mm, 20 cm with grain size 0.35 mm and 10 cm with gravel 6.00 mm). Water samples were collected from Asa River. The water sample was poured into the water filter; water samples were collected and analyzed. The filter has a capacity for producing 15.25 litres/h of clean water. The values of turbidity, pH, Electrical conductivity, Calcium, Magnesium, Sodium, Potassium, Iron II, Colonies growing on nutrient agent at 37°C in 24 hours and E-Coli for the filtered water were 0.91mg/l, 6.7, 26.8μS/cm, 12.6mg/l, 16.0mg/l, 0.82mg/l, 0.31mg/l, 0.12mg/l, 12 and 8, respectively while the corresponding values for non-filtered water were 6.7mg/l, 7.2, 83.7μS/cm, 28.0mg/l, 20.0mg/l, 1.63mg/l, 0.72mg/l, 0.65mg/l, 40 and 13. The filter reduced E-Coli present in the water by 69%. The slow sand water filter could be used in the school laboratory as a water treatment prototype device for teaching students.Keywords: slow sand filter, water quality, water treatment, granular carbon