Tag Archives: household water treatment

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.

“Carbon Credits” to Finance Household Water Treatment?

The application of “carbon credits” as a commodity to be bought and sold is not a feasible strategy for this or any other application. This approach is not sustainable and will create a bubble that will eventually collapse.

Summers SK, Rainey R, Kaur M, Graham JP. CO2 and H2O: Understanding Different Stakeholder Perspectives on the Use of Carbon Credits to Finance Household Water Treatment Projects. PLoS One. 2015 Apr 30;10(4):e0122894. doi: 10.1371/journal.pone.0122894.

BACKGROUND: Carbon credits are an increasingly prevalent market-based mechanism used to subsidize household water treatment technologies (HWT). This involves generating credits through the reduction of carbon emissions from boiling water by providing a technology that reduces greenhouse gas emissions linked to climate change. Proponents claim this process delivers health and environmental benefits by providing clean drinking water and reducing greenhouse gases. Selling carbon credits associated with HWT projects requires rigorous monitoring to ensure households are using the HWT and achieving the desired benefits of the device. Critics have suggested that the technologies provide neither the benefits of clean water nor reduced emissions. This study explores the perspectives of carbon credit and water, sanitation and hygiene (WASH) experts on HWT carbon credit projects.

METHODS: Thirteen semi-structured, in-depth interviews were conducted with key informants from the WASH and carbon credit development sectors. The interviews explored perceptions of the two groups with respect to the procedures applied in the Gold Standard methodology for trading Voluntary Emission Reduction (VER) credits.
RESULTS: Agreement among the WASH and carbon credit experts existed for the concept of suppressed demand and parameters in the baseline water boiling test. Key differences, however, existed. WASH experts’ responses highlighted a focus on objectively verifiable data for monitoring carbon projects while carbon credit experts called for contextualizing observed data with the need for flexibility and balancing financial viability with quality assurance.

CONCLUSIONS: Carbon credit projects have the potential to become an important financing mechanism for clean energy in low- and middle-income countries. Based on this research we recommend that more effort be placed on building consensus on the underlying assumptions for obtaining carbon credits from HWT projects, as well as the approved methods for monitoring correct and consistent use of the HWT technologies in order to support public health impacts.

Microbial Ecology of Household Sand Filter, Vietnam

Nitzsche KS, Weigold P, Lösekann-Behrens T, Kappler A, Behrens S. Microbial community composition of a household sand filter used for arsenic, iron, and manganese removal from groundwater in Vietnam. Chemosphere 2015 May 29;138:47-59. doi: 10.1016/j.chemosphere.2015.05.032.

Household sand filters are used in rural areas of Vietnam to remove As, Fe, and Mn from groundwater for drinking water purposes. Currently, it is unknown what role microbial processes play in mineral oxide formation and As removal during water filtration. We performed most probable number counts to quantify the abundance of physiological groups of microorganisms capable of catalyzing Fe- and Mn-redox transformation processes in a household sand filter. We found up to 104cellsg-1 dry sand of nitrate-reducing Fe(II)-oxidizing bacteria and Fe(III)-reducing bacteria, and no microaerophilic Fe(II)-oxidizing bacteria, but up to 106cellsg-1 dry sand Mn-oxidizing bacteria. 16S rRNA gene amplicon sequencing confirmed MPN counts insofar as only low abundances of known taxa capable of performing Fe- and Mn-redox transformations were detected. Instead the microbial community on the sand filter was dominated by nitrifying microorganisms, e.g. Nitrospira, Nitrosomonadales, and an archaeal OTU affiliated to Candidatus Nitrososphaera. Quantitative PCR for Nitrospira and ammonia monooxygenase genes agreed with DNA sequencing results underlining the numerical importance of nitrifiers in the sand filter. Based on our analysis of the microbial community composition and previous studies on the solid phase chemistry of sand filters we conclude that abiotic Fe(II) oxidation processes prevail over biotic Fe(II) oxidation on the filter. Yet, Mn-oxidizing bacteria play an important role for Mn(II) oxidation and Mn(III/IV) oxide precipitation in a distinct layer of the sand filter. The formation of Mn(III/IV) oxides contributes to abiotic As(III) oxidation and immobilization of As(V) by sorption to Fe(III) (oxyhydr)oxides.