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Thanks to a new technology developed by the Fraunhofer Alliance SysWasser, Germany it is now possible to extract from the humidity in the air water .
The principle behind it is a salt solution that runs down from a tower-shaped system and absorbs water from the air, known as hygroscopic brine. This brine is then pumped into a tank that stands a couple of metres high and contains
a vacuum.
Posted in Europe & Central Asia, Rainwater harvesting, Water supply
Tagged Drinking water, Energy, Energy development, Germany, Solar
A resident of Kathmandu has adopted ecological solutions to cope with the city’s persistent water shortage and power cuts.
Report of a visit to Dr. Shrestha’s Eco-home on 14 March 2010.
Dr. Roshan Raj Shrestha in his Eco-home. Photo: C. Dietvorst
Dr. Roshan Raj Shrestha built his Eco-home in November 2002. The two and a half story building is neither connected to the city water supply nor to the sewerage network. It uses several kinds of water conservation methods including rainwater harvesting, greywater recycling, ecological sanitation, Solar Water Disinfection (SODIS) and organic waste composting. Dr. Shrestha says he was able to recover the extra investment of US$ 1,000 for his water conservations systems within three years.
The Eco-home has helped Dr. Shrestha cope with Kathmandu’s severe water crisis. The public water supply can only meet half of the actual demand and the city’s Bagmati river is turning into an open sewer. The ground water level is decreasing by 2.5 metres a year due to over extraction. The mega Melamchi Water Supply Project, started in 1998 to tackle Kathmandu’s water crisis, has been plagued by delays.
Rainwater catchment terrace and tanks. Photo: C. Dietvorst
With an average annual precipitation of 1,600 mm in the Kathmandu Valley, Dr. Shrestha found that rainwater would provide with enough water for his family of five. Rainwater is collected on two roof terraces and stored in a 9,000 litre underground tank. Excess rainwater is diverted into a dug well, which acts as an intermittent tank that can store nearly 10,000 litres and also supports shallow groundwater recharge. SODIS is used to treat rainwater for drinking water, while water from the dug well is pretreated first in a biosand filter.
Residents constructing new houses in Kathmandu now get a 10% tax rebate on their building permit fee if they include a rainwater harvesting system in their design. The rebate can reach 30% in other municipalities in Nepal, says Prakash Amatya, the Executive Director of NGO Forum.
No water goes wasted in the Eco-home. Dr. Shrestha has installed a urine diversion dry toilet in his master bedroom. Urine and composted feces are used as garden fertilizer. A small reed bed treatment system is used to recycle grey water for garden watering, washing the car and for an extra flush toilet.
Solar panel. Photo: C. Dietvorst
The latest addition to the Eco-home is a 100-Watt Solar House System (SHS), installed in 2009. The solar panels provide enough energy to light the lamps in the house. Costing US$ 1,000, the system is only affordable for middle-class families, Shrestha admits, but it has proved its worth now that power cuts of up to 12 hours a day have become standard in Kathmandu.
Dr. Shrestha is proud of his model Eco-home. He is happy to give visitors and groups of students a tour. He finds that people readily accept the concept of rainwater harvesting and greywater recycling. They are not so keen about ecological sanitation though, because of the socio-cultural barriers associated with feces.
Dr. Roshan Raj Shrestha is Chief Technical Advisor, South-Asia Region for the UN-HABITAT Water for Asian Cities Programme
Sources used:
SODIS water bottle. Photo: C. Dietvorst
Reed Bed Treatment System for greywater recycling. Photo: C. Dietvorst
Urine diversion dry toilet. Photo: C. Dietvorst
Biosand filter. Photo: C. Dietvorst
Rain falls unto roofs and then runs off. And then? You could catch it and drink it. Any suitable roof surface—tiles, metal sheets, plastics, but not grass or palm leaf—can be used to intercept the flow of rainwater and provide a household with high-quality drinking water. Rainwater harvesting systems have been used since antiquity, and examples abound in all the great civilizations throughout history.
The groundwater level may be too deep, groundwater may be contaminated with minerals and chemicals such as arsenic or salt, surface water may be contaminated with faeces or chemicals. Rainwater falls on your own roof, and is almost always of excellent quality. It enables people to manage their own water supply and provides the luxury of “water without walking”, relieving the burden of water carrying, particularly for women and children. This convenience is available at every house on which rain falls, whether on a mountain top or an island in a salt sea. It is a truly great idea.
A women using her water storage tank in Guinnee-Bissau. Photo Paul Akkerman.
Storage tanks
Once you catch the water from the roof (or other hard surfaces), you have to store it somewhere. Ferro-cement tanks, made with a layer of cement with steel-wire reinforcement, are usually the best and cheapest option, and can be made locally. When a tank is below ground, it is called a cistern. No idea why, really.
Roof rainwater is usually of good quality and does not require treatment before consumption. The most important thing to ensure water quality is a good lid, keeping out light and insects, and a filter, keeping out all kinds of dirt.
The cheapest tank of all is to use the ground beneath your feet. This is called groundwater recharge, and is simply accomplished by letting rainwater infiltrate in the ground, instead of letting it escape and flow away. When you need it, you pump it up.
As small or large as you want
A rainwater harvesting system might be a 500 cubic meter underground storage tank, serving a whole community. Or it might be just a bucket, standing underneath a roof without a gutter. Each 20 litre container of clean water might save a kilometers long walk to the nearest source of clean water, and as fetching water on cold, wet and slippery days is particularly unpleasant, even this small yield is highly valued. In Uganda and Sri Lanka, rainwater is traditionally collected from trees, using banana leaves or stems as temporary gutters.
It is a technology which is extremely flexible and adaptable to a wide variety of settings, it is used in the richest and poorest societies on the planet, and in the wettest and driest regions of the world. Let’s build more gutters!
Author: Mark Tiele Westra, Editor Akvopedia.
Links:
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:
Is it really possible to stop rain, invoke lightning from the heavens or otherwise manipulate the weather? Jane Qiu and Daniel Cressey report on the once-scorned notion of weather modification.
[...]
China has one of the largest programmes for weather modification in the world. It spends between 400
million yuan (US$60 million) and 700 million yuan a year on it, and employs 32,000 people to operate 35 specially equipped planes, 7,000 anti-aircraft cannons and 5,000 rocket launchers. Official figures from the China Meteorological Administration say that the country created 250 billion tonnes of rain between 1999 and 2006, an annual production of more than 30 billion tonnes. This is enough to meet the needs of more than 500 million of its 1.3 billion people, but the country aims to generate 50 billion tonnes a year by 2010.
Many researchers, both in and outside China, doubt that sufficient evidence has been accumulated to support this claimed success. “In fact, China is very much behind in this area,” says Zhang Hong-fa, an atmospheric scientist at the Cold and Arid Regions Environmental and Engineering Research Institute in Lanzhou. “A false sense of achievement would impede genuine progress.”
Read more: Nature, 453, 970-974 (2008) – doi:10.1038/453970a – Published online 18 June 2008
Posted in East Asia & Pacific, Rainwater harvesting
Tagged China, cloud seeding, weather modification
A pioneering water harvesting system inspired by the Namib Desert Beetle is one the biomimicry innovations that will feature in the first annual edition of Nature’s 100 Best© book. The book is an initiative of ZERI, Biomimicry Guild and the Biomimmicry Institute, in cooperation with IUCN, and UNEP.
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.
Source: UNEP, 28 May 2008
Posted in Africa, Rainwater harvesting, Research
Tagged biomimicry, fog harvesting, Namib Desert Beetle
For over 20 years, the Barefoot College, India, has helped rural communities to develop their own rainwater harvesting systems and community-managed water supplies:
· In India, nearly 1300 systems in 17 states with a total storage capacity of 47 million liters provide clean water to over 235,000 school children in remote, rural communities.
· In Afghanistan and 5 countries in Africa, 15 rainwater systems constructed since 2006 with a total storage capacity of 1.5 million liters provide clean water to over 4,200 school children.
In their February 2008 newsletter, the Barefoot College gives an overview of their current rainwater harvesting projects, with links to pictures on the construction of a 100.000 litres rainwater tank in Sierra Leone and General Guidelines for Construction of a Rainwater Harvesting Tank in Schools.
