Sustainable WASH services can only be achieved if the technology used to provide services is sound enough for the specific context. Too often, however, water and sanitation services stop because the WASH technology no longer functions or is too complicated for the context which it’s in. New WASH technologies are promising successful solutions but are often not considered.
WASHTech, an action-research project, is developing and testing processes and tools to perform context-specific validations of potential WASH technologies. WASHTech also aims to successfully introduce the validated technologies into certain contexts such as countries, districts, or sub-districts.
Come and be part of this pre-launch on Friday 12 April 2013 from 09:30 – 11:00 hrs and learn how the “Technology Applicability Framework” and the “Technology Introduction Process” can help you achieve sustainable WASH services.
Stanford University is testing an inexpensive water filter, suitable for developing countries, that removes bacteria quickly and without clogging. The filter uses a piece of cotton treated with nanomaterial inks, that kills bacteria with electrical fields but uses just 20 percent of the power required by pressure-driven filters.
The Stanford filter, which is driven by gravity, has pores large enough to allow for a high flow rate–about 100,000 liters per hour. It uses electrical pulses to inactivate bacteria by poking holes in their cell walls. The research was led by Stanford materials science and engineering professors Yi Cui and Sarah Heilshorn.
To make the filter, researchers dip a piece of cotton batting in a water-based carbon-nanotube ink, let it dry, then dip it in an alcohol-based silver-nanowire ink and let it dry again. Cui and others have used similar dipping methods to make paper-nanotube battery electrodes and nanotube textiles. The long, narrow nanotubes and nanowires get enmeshed in the fibers.
Speedy sterilization: A Stanford researcher pours water through a funnel fitted with a cotton-nanotube filter that rapidly kills bacteria. The red cords supply electricity to the device, which uses electrical fields to poke holes in the bacteria. Photo: Technology Review
In preliminary tests, described online in the journal Nano Letters, the filter inactivated about 98 percent of E. coli bacteria.
In the tests, a wire, connected to an electrical power source, which could be car batteries or solar panels, is immersed in the water filter. The researchers think that the strong local electrical fields, which are formed at the tip of the silver nanowires, piercing the cell walls. When the electricity is off, the silver (which has antimicrobial properties) prevents bacteria from fouling the surface, a common problem with filters.
There have been no definitive studies of the effects of water-borne carbon nanotubes and silver nanowires on people and lower organisms; experiments with airborne carbon nanotubes have shown that their effect on mice lungs is similar to the effect of asbestos. But early tests on thousands of gallons of water suggest that the nanomaterials are not leaching into the water. The researchers will perform further tests to determine whether the nanomaterials remain enmeshed in the filter or are dislodged into the water over time.
The next step required is to improve the filter’s efficacy and show that it can work with a broad range of water-borne pathogens, including viruses and protozoa.
Watch the related video “Making a Nano-Water Filter for the Developing World”
Xianghao Ren … [et al.] (2010). Novel membrane bioreactor (MBR) coupled with a nonwoven fabric filter for household wastewater treatment. Water research ; vol., 44, no. 3 ; p. 751-760. DOI: 10.1016/j.watres.2009.10.013.
Abstract:
Conventional and modified membrane bioreactors (MBRs) are increasingly used in small-scale wastewater treatment. However, their widespread applications are hindered by their relatively high cost and operational complexity. In this study, we investigate a new concept of wastewater treatment using a nonwoven fabric filter bag (NFFB) as the membrane bioreactor. Activated sludge is charged in the nonwoven fabric filter bag and membrane filtration via the fabric is achieved under gravity flow without a suction pump. This study found that the biofilm layer formed inside the NFFB achieved 10 mg/L of suspended solids in the permeate within 20 min of initial operation. The dynamic biofilter layer showed good filterability and the specific membrane resistance consisted of 0.3-1.9 x 1012 m/kg. Due to the low F/M ratio (0.04-0.10 kg BOD5/m3/d) and the resultant low sludge yield, the reactor was operated without forming excess sludge. Although the reactor provided aerobic conditions, denitrification occurred in the biofilm layer to recover the alkalinity, thereby eliminating the need to supplement the alkalinity. This study indicates that the NFFB system provides a high potential of effective wastewater treatment with simple operation at reduced cost, and hence offer an attractive solution for widespread use in rural and sparsely populated areas.
Amin, M.T. and Han, M.Y. (2009). Roof-harvested rainwater for potable purposes : application of solar collector disinfection (SOCO-DIS). Water research ; vol. 43, no. 20 ; p. 5225-5235. DOI: doi:10.1016/j.watres.2009.08.041
Abstract
The efficiency of solar disinfection (SODIS), recommended by the World Health Organization, has been determined for rainwater disinfection, and potential benefits and limitations discussed. The limitations of SODIS have now been overcome by the use of solar collector disinfection (SOCO-DIS), for potential use of rainwater as a small-scale potable water supply, especially in developing countries. Rainwater samples collected from the underground storage tanks of a rooftop rainwater harvesting (RWH) system were exposed to different conditions of sunlight radiation in 2-L polyethylene terephthalate bottles in a solar collector with rectangular base and reflective open wings. Total and fecal coliforms were used, together with Escherichia coli and heterotrophic plate counts, as basic microbial and indicator organisms of water quality for disinfection efficiency evaluation. In the SOCO-DIS system, disinfection improved by 20–30% compared with the SODIS system, and rainwater was fully disinfected even under moderate weather conditions, due to the effects of concentrated sunlight radiation and the synergistic effects of thermal and optical inactivation. The SOCO-DIS system was optimized based on the collector configuration and the reflective base: an inclined position led to an increased disinfection efficiency of 10–15%. Microbial inactivation increased by 10–20% simply by reducing the initial pH value of the rainwater to 5. High turbidities also affected the SOCO-DIS system; the disinfection efficiency decreased by 10–15%, which indicated that rainwater needed to be filtered before treatment. The problem of microbial regrowth was significantly reduced in the SOCO-DIS system compared with the SODIS system because of residual sunlight effects. Only total coliform regrowth was detected at higher turbidities. The SOCO-DIS system was ineffective only under poor weather conditions, when longer exposure times or other practical means of reducing the pH were required for the treatment of stored rainwater for potable purposes.
Article Outline
1. Introduction
2. Materials and methods
2.1. SODIS and SOCO-DIS systems
2.2. Microbial analysis
3. Results and discussions
3.1. Sampling site and characteristics
3.2. Characteristics of different weather conditions
3.3. The effects of the collector’s base angle and different backing surfaces in the SOCO-DIS system
3.4. Comparison of the SODIS and SOCO-DIS systems
3.4.1. The effects of radiation and temperature effects on microbial inactivation
3.4.2. The effects of initial pH values on disinfection efficiency
3.4.3. The effects of initial turbidity values on disinfection efficiency
3.4.4. Microbial regrowth in SOCO-DIS system and comparison with SODIS
4. Conclusions
Acknowledgements
References
Contact:
Assistant Professor, Department of Environmental Sciences, COMSATS Institute of Information Technology, Abbottabad, 22060, Pakistan, e-mail: muhammadamin [at] ciit.net.pk
bProfessor, Civil and Environmental Engineering Department, Seoul National University, Shinrimdong, Kwanak Gu, Seoul, 151-742, Republic of Korea, e-mail: myhan [at] snu.ac.kr
The US Environmental Protection Agency (EPA) hosted a January 6, 2009, memorandum of understanding (MOU) signing ceremony for five national organizations that have joined forces to do further research into water efficiency in plumbing, according to the Web site of the Chicago-based Alliance for Water Efficiency, the organization leading the partnership, that further consisted of:
International Code Council
International Association of Plumbing and Mechanical Officials (IAPMO)
Plumbing, Heating, and Cooling Contractors Association
Plumbing Manufacturers Institute.
The organizations pledged to develop research programs to assist in the development and use of water-efficient plumbing. The research will cover efficient and sustainable products, systems and practices, including:
New research from Kajima, a Japanese company, and Tokyo University, suggests that microbes from human waste could be a good source for hydrogen fuel cell cars. According to a report yesterday on Japan’s Nikkei, the company has produced a fuel cell that has generated 130W from each cubic meter of waste. Kajima believes it will take another decade to commercialize the product.
Researchers from the University of California, and administrators at California’s Orange County Sanitation District, appear to be further along. Last fall, they installed an $8 million fuel-cell device to convert human waste into hydrogen fuel. In an interview with the Orange County Register, Scott Samuelsen, director of UC Irvine’s National Fuel Cell Research Center who helped develop the device, said, “The waste stream from society is being turned around, and providing energy and transportation fuel for the society. “
Hug, S.J., Leupin, O.X. and Berg, M. (2008). Bangladesh and Vietnam : different groundwater compositions require different approaches to arsenic mitigation. Environmental science and technology ; vol. 42, no. 17 ; p. 6318-6323. DOI: 10.1021/es7028284
To be successful, the mitigation strategy must take into account the geological differences in groundwater, the economic resources of the population, and the availability of infrastructure for water treatment.
Conclusions:
Vietnam and Bangladesh are both confronted with high arsenic concentrations, but distinct water compositions require different solutions. Arsenic mitigation depends for the most part on natural factors, such as the availability of alternative water sources and the feasibility of water treatment. If several options are available, socioeconomic factors determine which mitigation option is implemented most successfully.
The socially accepted and already widespread sand filters in the Red River delta have advantages for their simplicity and low cost of operation. The removal of iron from the pumped water is immediately apparent even to people who are not aware of the arsenic problem. Thus, sand filters are a good option in Vietnam and in other affected regions with high concentrations of dissolved iron.
Arsenic removal in the worst-affected districts of Bangladesh is considerably more difficult. Since there are currently no selective sorbents, both arsenic and phosphate have to be removed and fixed-bed columns will require frequent regeneration or replacement. Activated alumina columns that can be regenerated have shown very good results. Filter columns with zerovalent iron are very promising, as metallic iron is inexpensive, widely available, and capable of forming precipitates with very high sorption site densities. An
improved understanding of the reactions over long periods of operation can lead to further optimization and wider applicability. An issue that is often discussed is the sludge produced in water treatment units. Sludge with elevated arsenic concentrations needs to be collected and handled properly. Containment under oxic conditions or in closed disposal sites are good solutions. However, the quantities of arsenic in water used for drinking are small compared to the amounts of arsenic pumped into rice fields by irrigation and probably partly remobilized during monsoon flooding. In the long term, controlled transport and release of treatment
sludge into large rivers during high water levels, ensuring rapid dilution and transport into the ocean, could be studied as an alternative to containment. Several mitigation options are now available and should be implemented to avoid further exposure to arsenic-tainted drinking water.
Anaerobic digestion represents nowadays one of the most cost-effective alternatives for waste (water) treatment, which has experienced a fast development during the last three decades. This Latin-American Workshop and Symposium will offer a selected program including the latest research findings and technological applications on anaerobic wastewater treatment, solids stabilization and biogas production as a renewal energy source.
This event is addressed to researchers, waste managers, consultants, representatives of both public and private sectors, environmental engineers and other related professionals.
Organised by the International Water Association (IWA).
The Namib Desert beetle lives in a location that receives a mere half an inch of rain a year yet can harvest water from fogs that blow in gales across the land several mornings each month. A team from the University of Oxford and the UK defense research firm QinetiQ, have designed a surface that mimics the water-attracting bumps and water-shedding valleys on the beetle’s wing scales that allows the insect to collect and funnel droplets thinner than a human hair.
The patchwork surface hinges on small, poppy-seed sized glass spheres in a layer of warm wax that tests show work like the beetle’s wing scales.
Trials have now been carried out to use the beetle film to capture water vapour from cooling towers. Initial tests have shown that the invention can return 10 per cent of lost water and lead to cuts in energy bills for nearby buildings by reducing a city’s heat sink effect.
An estimated 50,000 new water-cooling towers are erected annually and each large system evaporates and loses over 500 million litres.
Other researchers, some with funding from the US Defense Advanced Research Agency, are mimicking the beetle water collection system to develop tents that collect their own water up to surfaces that will ‘mix’ reagents for ‘lab-on-a-chip’ applications.
