Development of a low cost water purification system – a case study ceramic filters and moringa oleifera seeds
Macharia, Jane W
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Majority of people living in developing world do not have access to quality water. These people rely on readily available sources which are normally of low quality thus exposing them to waterborne diseases. This study was conducted to investigate the efficiency of clay filters and Moringa oleifera seeds in water purification. The study involved making porous clay pots by incorporating burnout material into the clay when moulding it and testing the coagulant and disinfectant ability of M. oleifera seeds. Four ration by volume i.e. 50:50, 55:45, 60:40 and 65:35 (Clay: Sawdust) were selected and filters prepared from them in triplicates. The filters were fired at 850°C for 8 hours by first drying them at 100°C for two hours. Another set of filters was prepared in the same way but fired at 650°C. The M. oleifera wood powder and seed husks were also used as the burnout material to prepare a different set of filters. The efficiency of the filters and M. oleifera seeds in treating water was tested against selected microbial, chemical and physicochemical parameters and also by determining the flow rates. Turbidity and Feacal Coliforms were the most affected parameters by the two POU interventions. The filters made from local sawdust had flow rates ranging between 28.0 and 104.5ml/hr. The filters made from M. oleifera wood and husks powder recorded the lowest flowrates of 11.5 – 17.8ml/hr. The filters reduced Escherischia coli with an efficiency ranging from 99.1 to 100%. This corresponded to an average numerical reduction from an initial E coli count of 390±10/ml to 0.08±0.1 CFU/ml. Turbidity was reduced by an efficiency ranging between 97.2 and 98.6%. For all the filters, turbidity of water was reduced to below 1.7 NTU. The filters were also found to adsorb lead and copper ions with an adsorption efficiency of 96.5-99.8 % and 99.5-99.98% respectively. The other parameters tested on the filters were TDS and pH. The filters had minimal effect on total dissolved substances with a reduction efficiency range of 10.1-12.5%. The effect on pH was negligible ranging between -0.34 and 1.7%. All the filters were found to be equally effective in purifying water. Varying the combustible material, firing temperature and ratio of clay to the combustible material did not affect the efficiency of the filters in removing contaminants. The variations only affected the flow rates of the filters. Tests with M. oleifera seeds indicated that the seeds had both biocoagulant and phytodisinfectant ability. A dosage of 0.2 g/l reduced turbidity of artificial turbid water with a reduction efficiency of upto 99.2 %. With naturally occurring turbid water, the efficiency was lower at 59.0 % removal. Tests with E. coli and other Coliforms indicated that the seeds could reduce them with a reduction efficiency of 86.8% and 82.7% respectively. TSS removal was at 53.2% while TDS, pH, and conductivity removal was at approximately 5%. The seeds did not affect the alkalinity, nitrates and nitrites concentration of the sample. A test on the effect of pH revealed that the seeds were more effective in slightly basic conditions though the difference was minimal. Deoiling the seeds and using the seed cake residue showed similar efficiency and therefore the edible oil could be extracted first before the seeds are used in water treatment. Sequential use of the two POU would produce quality water and also prevent clogging of filters. The seeds could be used in the pretreatment step to lower the turbidity of the water and also lower the Microbial contaminants. On passing this water through the filters, the E. coli would be completely eliminated and turbidity lowered to below 2 NTU.
University of Nairobi