Development of Ceramic Filters for Household Water Treatment in Nigeria ()
Casting process.
mineral analysis for metals using the atomic spectrometry.
The Design Consideration for the Filter
The ceramic filter design was adapted from the Potters for
Drying process.
Fired filter sample.
Peace ceramic pot-shaped filters, which was developed in 1981 by Dr. Fernando Mazariegos of the Central American Industrial Research Institute (ICAITI) in Guatemala. Though other shapes and designs have been given to the ceramic water filters, for the purpose of this project/research, the flat bottom pot filter design was adapted for the reasons highlighted below:
・ The effects of the constituent materials were being studied and so less emphasis was placed on shape and design of the sample filters.
・ Since the pot filter holds the raw water and is a one-com- ponent filter element, it is assumed that there is less risk of recontamination of filtered water in the receptacles through seepages as is possible with the disk and candle-shaped fil- ters.
・ Thirdly, with the shaping technique being adapted for the project/research, only the candle or pot-shaped filters will be feasible.
・ And sometimes the candle-shaped filters are too fragile and tear when demolding. Hence, the pot shaped filters proved most realisable using the slip-casting method.
・ Finally, with the pot-shaped filter, there is the possibility of greater filtration flow rates because the pot filter element engages a larger surface area in filtration. The pot filters also require low maintenance and are easy to use, not re- quiring any special educational level to operate.
Slip casting was adapted as shaping method in this research as against the commonly used press method for the following reasons:
・ To attempt to achieve finer particle size and denser packing in the ceramic body which would result in smaller pores and hence improve the filtration efficiency in the resulting filters.
・ Also to achieve low production cost realisable with slip casting, and
・ To achieve lower shrinkage values in the ceramic filter, as less plastic materials can be used with slip casting and there- fore having more uniform dimensions in the filters.
Results
The results show that the developed filters were effective in the treatment of physio-chemical contaminants detected in the water samples.
All the sample filters gave low shrinkage values which are desirable. The filter sample S24 showed the lowest shrinkage in diameter and this can be attributed to the greater ratio of non- plastic materials in the composition.
The estimated porosity values indicates that sample S24 has the highest porosity (42.26%) and this is resultant of the higher ratio of burnout material (charcoal) in the sample’s composition. Increase in porosity is said to result from the burnout material content (Plappally, 2010). Sample S2 with same charcoal con- tent ratio as S5 gave higher porosity of 34.77%, indicating that higher laterite in the composition also varied the porosity of the sample. This corroborates with Brown et al. (2007), that “late- rite particles increase the porosity of the fired filter as they do not form same vitrified bonds as the clay between particles”.
The flow rate testing results shows that sample S5 gave the highest flow rate while having the lowest porosity (See Figures 7 and 8). But Plappally (2010) explains that the pore density distribution across the structural volume of the filter as well as the porosity has major influence on the flow characteristics of a ceramic filter; stating that the velocity of flow is reduced with increased porosity. The researcher was unable to determine the pore distribution in the filters due to inability to access the ne- cessary equipment for the procedure and hence cannot analyze the variation between the estimated porosity values and the flow rate obtained in the developed filters. However, the overall flow rate values of all the sample filters were low. And this can be attributed to the small sizes of the developed filters as com- pared to the marketed ones. Flow rate is said to increase with increases in the surface area in contact with the water because more pores are being utilized.
In the microbial analysis, three different raw water samples based on their sources were used. The analysis involved testing for bacterial counts, coliform counts, E. coli and fungal counts. The results of the stream and borehole samples indicated re- contamination in the treated water samples. But based on the initial results, filter sample S24 was observed to have given the best treatment with percentage reductions in bacterial counts of up to 77% in the well samples and 78% reduction in the bore- hole samples. Filter sample S5 gave a 100% reduction of coli- form in the well water samples.
For the physio-chemical analysis, two different raw water samples based on their sources were used. They were the well and borehole raw water sources. The results of the analysis of some of the parameters are discussed here:
The results show that all the filter samples improved pH and treated TS, TDS and TSS in both classes of water samples. Also all the filter samples treated Lead (Pb) to a 100% reduc- tion in both water samples and fluoride up to 75% reduction in filter sample S2.
While all the filter samples increased Calcium (Ca) levels in both water samples, they increased Iron (Fe) concentrations only in the well water samples. But they gave a reduction of up to 47% of Iron (Fe) concentrations in the borehole water samples.
Though the sulphate (SO4−) concentration values appear in- credibly high, all the filter samples showed capacity to treat sulphate in the borehole water samples with reduction levels of up to 76% in sample S24.
It was also shown that all filter samples gave an increased concentration value of Copper (Cu) in both raw water sample classes. Turbidity was recorded only in S2 treated well water and this could be due to possible leaching of some of the ce- ramic material into the water.
Findings and Discussion
The findings are summarized below:
1) Charcoal was a good alternative burnout material in the body compositions, giving good binding and pore-forming qualities up to 50% volume ratio in the body;
2) Increasing quantity of Bone char in the ceramic filter composition increased the filter’s ability to reduce fluoride con- centration in the treated water sample;
3) Increased charcoal volume ratio in the filter composition increased the porosity of the resulting filter sample. Increased ratio of laterite in the filter body also slightly improved the porosity;
4) Slip casting technique produced good filter samples with even thickness all-round the filter, minimal shrinkage and suf- ficient dried and fired strength in the body;
5) The developed filters proved to substantially improve the quality of treated water within the scope of the project.
Flow rate testing.
Filtration process.
・ All the filter samples improved pH in the treated water and gave reduction in Total Solids, Total Dissolved and Sus- pended Solids values present in the water.
・ All the filter samples reduced the fluoride concentration in water in a range of between 33.6% - 75% reduction.
・ All the filter samples treated Lead and Sulphate in the water samples with reductions in sulphate concentrations of up to 76.19% and 100% in lead.
・ All filter samples gave good microbial treatment results with percentage reductions in microbial load of up to 78%.
The study has proved that the incorporation of bone char in the making of ceramic filters improves the filter’s ability to remove fluoride from water. It was indicated from the study that the application of silver to ceramic filters makes them more viable and reduce the problems of recontamination. The study has also shown that increased presence of charcoal in the filter, improves its ability to treat chemical impurities in water such as sulphate and lead.
Conclusion and Recommendation
Based on the findings and discovery in the course of this study, the following observations and recommendations were made:
1) Considering the effectiveness of the slip casting method in the shaping of ceramic pot filters as shown in this study, it is recommended that this technique be employed in the produc- tion of ceramic filters as an alternative to pressing thereby eli- minating the initial capital cost of purchasing a hydraulic press;
2) Subsequent upon the developed filters’ ability to treat both chemical and microbial contaminants in water, it is recom- mended that the ceramic manufacturing group adopts these fil- ter compositions in their production;
3) It is also recommended that further study and research be carried out on the developed filters to improve upon its perfor- mance in water treatment by government and private investors to bring about mass-production of these filters, making it avai- lable in most homes thereby alleviating the issue of inadequate supply of safe water in our country and the world.
This project is expected to extend the use of ceramic filters in the household by lifting the existing limitation of the ceramic filters to cover the treatment of chemical impurities in water as well as the microbial and thus making it a near-complete solu- tion to household water treatment needs.
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