Tag Archives: household water treatment

High Flow Ceramic Pot Filters Improve with Clogging

van Halem D, van der Laan H, Soppe AIA, Heijman SGJ. High flow ceramic pot filters. Water Res. 2017 Jul 20;124:398-406. doi: 10.1016/j.watres.2017.07.045.

Ceramic pot filters are considered safe, robust and appropriate technologies, but there is a general consensus that water revenues are limited due to clogging of the ceramic element. The objective of this study was to investigate the potential of high flow ceramic pot filters to produce more water without sacrificing their microbial removal efficacy. High flow pot filters, produced by increasing the rice husk content, had a higher initial flow rate (6-19 L h-1), but initial LRVs for E. coli of high flow filters was slightly lower than for regular ceramic pot filters. This disadvantage was, however, only temporarily as the clogging in high flow filters had a positive effect on the LRV for E. coli (from below 1 to 2-3 after clogging). Therefore, it can be carefully concluded that regular ceramic pot filters perform better initially, but after clogging, the high flow filters have a higher flow rate as well as a higher LRV for E. coli. To improve the initial performance of new high flow filters, it is recommended to further utilize residence time of the water in the receptacle, since additional E. coli inactivation was observed during overnight storage. Although a relationship was observed between flow rate and LRV of MS2 bacteriophages, both regular and high flow filters were unable to reach over 2 LRV.

Effectiveness of Household Water Treatment is Inconsistent

Rosa G, Clasen T. Consistency of Use and Effectiveness of Household Water Treatment among Indian Households Claiming to Treat Their Water. Am J Trop Med Hyg. 2017 Jul;97(1):259-270. doi: 10.4269/ajtmh.16-0428.

Household water treatment (HWT) can improve drinking water quality and prevent disease if used correctly and consistently by populations at risk. Current international monitoring estimates by the Joint Monitoring Programme for water and sanitation suggest that at least 1.1 billion people practice HWT. These estimates, however, are based on surveys that may overstate the level of consistent use and do not address microbial effectiveness. We sought to assess how HWT is practiced among households identified as HWT users according to these monitoring standards. After a baseline survey (urban: 189 households, rural: 210 households) to identify HWT users, 83 urban and 90 rural households were followed up for 6 weeks. Consistency of reported HWT practices was high in both urban (100%) and rural (93.3%) settings, as was availability of treated water (based on self-report) in all three sampling points (urban: 98.8%, rural: 76.0%). Nevertheless, only 13.7% of urban and 25.8% of rural households identified at baseline as users of adequate HWT had water free of thermotolerant coliforms at all three water sampling points. Our findings raise questions about the value of the data gathered through the international monitoring of HWT as predictors of water quality in the home, as well as questioning the ability of HWT, as actually practiced by vulnerable populations, to reduce exposure to waterborne diseases.

Household Water Treatment Technologies Equally Effective for Thermotolerant Coliform Bacteria

Mohamed H, Clasen T, Njee RM, Malebo HM, Mbuligwe S, Brown J. Microbiological Effectiveness of Household Water Treatment Technologies under Field Use Conditions in Rural Tanzania. Tropical Medicine and International Health 2015 Oct 27. doi: 10.1111/tmi.12628.

OBJECTIVES: To assess the microbiological effectiveness of several household water treatment and safe storage (HWTS) options in situ in Tanzania, before consideration for national scale-up of HWTS.

METHODS: Participating households received supplies and instructions for practicing six HWTS methods on a rotating five-week basis. We analysed 1202 paired samples (source and treated) of drinking water from 390 households, across all technologies. Samples were analysed for thermotolerant (TTC) coliforms, an indicator of faecal contamination, to measure effectiveness of treatment in situ.

RESULTS: All HWTS methods improved microbial water quality, with reductions in TTC of 99.3% for boiling, 99.4% for Waterguard brand sodium hypochlorite solution, 99.5% for a ceramic pot filter, 99.5% for Aquatab® sodium dichloroisocyanurate (NaDCC) tablets, 99.6% for P&G Purifier of Water flocculent/ disinfectant sachets, and 99.7% for a ceramic siphon filter. Microbiological performance was relatively high compared with other field studies and differences in microbial reductions between technologies were not statistically significant.

CONCLUSIONS: Given that microbiological performance across technologies was comparable, decisions regarding scale-up should be based on other factors, including uptake in the target population and correct, consistent, and sustained use over time.

Microbiological Evaluation of Electric Kettles; Rural China

Cohen A, Tao Y, Luo Q, Zhong G, Romm J, Colford JM Jr, Ray I. Microbiological Evaluation of Household Drinking Water Treatment in Rural China Shows Benefits of Electric Kettles: A Cross-Sectional Study. PloS one. 2015 Sep 30;10(9):e0138451. doi: 10.1371/journal.pone.0138451. 

BACKGROUND: In rural China ~607 million people drink boiled water, yet little is known about prevailing household water treatment (HWT) methods or their effectiveness. Boiling, the most common HWT method globally, is microbiologically effective, but household air pollution (HAP) from burning solid fuels causes cardiovascular and respiratory disease, and black carbon emissions exacerbate climate change. Boiled water is also easily re-contaminated. Our study was designed to identify the HWT methods used in rural China and to evaluate their effectiveness.

METHODS: We used a geographically stratified cross-sectional design in rural Guangxi Province to collect survey data from 450 households in the summer of 2013. Household drinking water samples were collected and assayed for Thermotolerant Coliforms (TTC), and physicochemical analyses were conducted for village drinking water sources. In the winter of 2013-2104, we surveyed 120 additional households and used remote sensors to corroborate self-reported boiling data.

FINDINGS: Our HWT prevalence estimates were: 27.1% boiling with electric kettles, 20.3% boiling with pots, 34.4% purchasing bottled water, and 18.2% drinking untreated water (for these analyses we treated bottled water as a HWT method). Households using electric kettles had the lowest concentrations of TTC (73% lower than households drinking untreated water). Multilevel mixed-effects regression analyses showed that electric kettles were associated with the largest Log10TTC reduction (-0.60, p<0.001), followed by bottled water (-0.45, p<0.001) and pots (-0.44, p<0.01). Compared to households drinking untreated water, electric kettle users also had the lowest risk of having TTC detected in their drinking water (risk ratio, RR = 0.49, 0.34-0.70, p<0.001), followed by bottled water users (RR = 0.70, 0.53-0.93, p<0.05) and households boiling with pots (RR = 0.74, 0.54-1.02, p = 0.06).

CONCLUSION: As far as we are aware, this is the first HWT-focused study in China, and the first to quantify the comparative advantage of boiling with electric kettles over pots. Our results suggest that electric kettles could be used to rapidly expand safe drinking water access and reduce HAP exposure in rural China.

Drinking Water Options for Developing Countries

Pandit AB, Kumar JK. Clean Water for Developing Countries. Annual Review of Chemical and Biomolecular Engineering. 2015 Jul 24;6:217-46. doi: 10.1146/annurev-chembioeng-061114-123432.

Availability of safe drinking water, a vital natural resource, is still a distant dream to many around the world, especially in developing countries. Increasing human activity and industrialization have led to a wide range of physical, chemical, and biological pollutants entering water bodies and affecting human lives. Efforts to develop efficient, economical, and technologically sound methods to produce clean water for developing countries have increased worldwide. We focus on solar disinfection, filtration, hybrid filtration methods, treatment of harvested rainwater, herbal water disinfection, and arsenic removal technologies. Simple, yet innovative water treatment devices ranging from use of plant xylem as filters, terafilters, and hand pumps to tippy taps designed indigenously are methods mentioned here. By describing the technical aspects of major water disinfection methods relevant for developing countries on medium to small scales and emphasizing their merits, demerits, economics, and scalability, we highlight the current scenario and pave the way for further research and development and scaling up of these processes. This review focuses on clean drinking water, especially for rural populations in developing countries. It describes various water disinfection techniques that are not only economically viable and energy efficient but also employ simple methodologies that are effective in reducing the physical, chemical, and biological pollutants found in drinking water to acceptable limits.

“Improved” Water Supplies are not Necessarily Safe

Heitzinger K, Rocha CA, Quick RE, Montano SM, Tilley DH Jr, Mock CN, Carrasco AJ, Cabrera RM, Hawes SE. “Improved” But Not Necessarily Safe: An Assessment of Fecal Contamination of Household Drinking Water in Rural Peru. The American journal of tropical medicine and hygiene. 2015 Jul 20. pii: 14-0802.

The indicator used to measure progress toward the Millennium Development Goal (MDG) for water is access to an improved water supply. However, improved supplies are frequently fecally contaminated in developing countries. We examined factors associated with Escherichia coli contamination of improved water supplies in rural Pisco province, Peru. A random sample of 207 households with at least one child less than 5 years old was surveyed, and water samples from the source and storage container were tested for E. coli contamination. Although over 90% of households used an improved water source, 47% of source and 43% of stored water samples were contaminated with E. coli. Pouring or using a spigot to obtain water from the storage container instead of dipping a hand or object was associated with decreased risk of contamination of stored water (adjusted prevalence ratio [aPR] = 0.58, 95% confidence interval [CI] = 0.42, 0.80). Container cleanliness (aPR = 0.67, 95% CI = 0.45, 1.00) and correct handwashing technique (aPR = 0.62, 95% CI = 0.42, 0.90) were also associated with decreased contamination risk. These findings highlighted the limitations of improved water supplies as an indicator of safe water access. To ensure water safety in the home, household water treatment and improved hygiene, water handling, and storage practices should be promoted.

Ceramic Pot Filter Design and Construction; Experience Required

With the right equipment and a lot of practice, ceramic pot filters can be made that have acceptable performance. But ceramic pot filters are not practical for every household. In our experience their design and construction is very particular and slight changes the factors mentioned in this article can drastically impact performance. Their appeal lies in the fact that local potters with skill can make them, but not everyone has such skill and equipment. Ceramic pots can also be somewhat fragile and can be broken in transit. Other household water treatment options are available and may be preferred in situations where performance reliability and durability are important.

A. I. A. Soppe, S. G. J. Heijman, I. Gensburger, A. Shantz, D. van Halem, J. Kroesbergen, G. H. Wubbels and P. W. M. H. Smeets. Critical parameters in the production of ceramic pot filters for household water treatment in developing countries  Journal of Water and Health Vol 13 No 2 pp 587–599 2015 doi:10.2166/wh.2014.090

The need to improve the access to safe water is generally recognized for the benefit of public health in developing countries. This study’s objective was to identify critical parameters which are essential for improving the performance of ceramic pot filters (CPFs) as a point-of-use water treatment system. Defining critical production parameters was also relevant to confirm that CPFs with high-flow rates may have the same disinfection capacity as pots with normal flow rates. A pilot unit was built in Cambodia to produce CPFs under controlled and constant conditions. Pots were manufactured from a mixture of clay, laterite and rice husk in a small-scale, gas-fired, temperature-controlled kiln and tested for flow rate, removal efficiency of bacteria and material strength. Flow rate can be increased by increasing pore sizes and by increasing porosity. Pore sizes were increased by using larger rice husk particles and porosity was increased with larger proportions of rice husk in the clay mixture. The main conclusions: larger pore size decreases the removal efficiency of bacteria; higher porosity does not affect the removal efficiency of bacteria, but does influence the strength of pots; flow rates of CPFs can be raised to 10–20 L/hour without a significant decrease in bacterial removal efficiency.