Rainwater and sunlight. Both have been around a long time. People have collected rainwater for drinking, cooking, bathing, and agricultural purposes for thousands of years. Collection devices have taken many forms including rain barrels and cisterns. For the grandest cistern of them all, do a web search using the site of your choice for ‘Istanbul Sunken Palace’. Also search for images of this colossus. I wonder if it was the inspiration for the underground city of the dwarves, Khazad-dûm in Moria, in Tolkein’s Lord of the Rings trilogy, and Peter Jackson’s film treatment of the novels? Looks like it to me.
Rain barrels are easier to fit next to your house, as the 1903 photo of a Nebraska farmstead shows (back left corner of house).
|Source: Library of Congress, American Memory Collection|
“Sunlight is the best disinfectant” – received wisdom from U.S. Supreme Court Justice Louis Brandeis. He was referring to openness and transparency. However, solar water disinfection (SODIS) is an effective means of water purification. The Swiss Federal Institute of Aquatic Sciences and Technology (Eawag) provides an informative web site on SODIS. To purify water with this method, according to the site,
[a]ll it requires is sunlight and PET bottles. How does it work? Clear PET bottles are filled with the water and set out in the sun for 6 hours. The UV-A rays in sunlight kill germs such as viruses, bacteria and parasites (giardia and cryptosporidia). The method also works when air and water temperatures are low.
People can use the SODIS method to treat their drinking water themselves. The method is very simple and its application is safe. It is particularly suitable for treating relatively small quantities of drinking water.The two following cleantech patents illustrate 2012 innovations in water harvesting and sunlight water disinfection.
Keep Debris Out Of Your Rain BarrelScott William Allan of Kitchener, Ontario, Canada, invented a “Water harvesting device” for which he was awarded patent US 8,097,151 in mid-January, 2012. Allan assigned his patent to Green Ripple Innovations Inc., Waterloo, Ontario, Canada. The problem he seeks to solve regarding rain barrel design is that,
"[o]ne major concern of these devices is to provide adequate means for collecting water most efficiently while also ensuring that foreign matter or debris is not collected with it or that may cause an obstruction to water flow. In the example of rainwater harvesting from a building collection systems, debris such as twigs, leaves from trees and other matter often accompany rain water exiting from conventional eaves and downspouts and without adequate management of these items water inlet areas can fill and clog with debris resulting in ineffective water collection or even backing up of the water toward the building structure. There are prior art devices for rainwater collection, filters and the like for installation within the eaves and downspouts but failing to install these or properly maintaining them raises the needs to have these safeguards directly integrated with the water harvesting device. Furthermore, many prior art devices that capture such debris requires frequent and regular maintenance is required to keep the inlet are clean resulting in time consuming maintenance for the user. These debris items, twigs for example are often shaped such that they can also enter the water inlet and potentially cause damage to internal components of a water harvesting device. In the example of a rainwater harvesting device, filtering devices or mosquito safety screens installed at the inlet are susceptible to damage from entering debris. Once a tear or hole is pierced in the safety netting mosquitoes are free to enter the device and lay their eggs, potentially leading to the undesired breeding of the West Nile Virus.
"Another concern with these devices is that adequate means water and debris management all year around is not provided. During each season, water and debris should be managed so each may be directed in a proper manner so as to: avoid collection of water into the tank potentially freezing and causing damage to the device; and avoid clogging of flow and potential backing up of water-flow due to debris build-up. Current rainwater harvesting devices do not facilitate management of this debris as such."His solution, summarized in the ‘151 patent’s Claim 1 is:
A debris diversion enabled water harvesting device comprising;One of the patent drawings illustrates the invention. Would the Darwin Gilpin family shown in the 1903 photo have used this?
a tank portion for containment of water and at least one water entry area for the entry of water into said tank portion;
wherein said water entry area includes a diversion apparatus for diverting unwanted debris away from said water entry area;
a water overflow located in the upper area of said tank portion wherein said water overflow may release excess water from within the said tank portion;
wherein said water overflow includes a screen.
SODIS-PlusHow is this invention different than the method described by Eawag, above?
Patent US 8,142,652, “Container for purification of water by sunlight,” was granted to Petra Wadström (Åkersberga, Sweden) on March 27, 2012. The invention, in contrast to the simple PET bottle, provides a sectioned container which passes sunlight through the first section (to provide UV-A disinfection) and absorbs sunlight and emits infrared radiation in the second section (to provide heating of the water).
Claim 1 summarizes, with figure feature numbers removed for clarity:
"Container for purification of water by utilizing sunlight, including a first section, which at least partly includes a sunlight permeable layer, and a second section, which at least partly is opposite the first section and at least partly includes a sunlight absorbing and infrared radiation emitting (IR-emitting) layer, wherein the first and the second section together enclose a volume, in which the water can be received to be heated by and exposed to sunlight, characterized in that the first section, is formed such that the permeable layer is essentially flat, and the second section is arranged such that the volume includes at least a first and a second portion, wherein the first and the second portion, respectively, have a first and a second distance, respectively, between the permeable layer and the sunlight absorbing and IR-emitting layer, where the first and second distances are mutually different, wherein a temperature difference between the water in the first and second portion is created after a period of sun exposure."
The inventor’s concerns:
"In poor countries, boiling of water is done over an open fire, whereby a considerable amount of wood is consumed. Approximately 1 kg wood is needed for 1 liter of water to reach 100 °C. To fetch wood takes a long time and can be costly, at the same time as it has a negative effect on the environment. Here, the environment is harmed by deforestation, which results in soil erosion.The inventor is concerned with deforestation and soil erosion, among other items, in poor countries, but a) wouldn’t people in those countries also use fires for cooking in addition to water purification?; b) isn’t the ability of people, anywhere, to obtain suitable drinking water by whatever method they have available, more important than worrying about “harm” to the environment from “deforestation”? Or is the environment, viewed from an affluent developed-world perspective, more important? Surely, cooking fires built with wood from renewable trees (after all, they re-seed and re-grow, you know) are not going to result in “deforestation.” Maybe a better approach to ensuring that people in ”poor countries” don’t “deforest” their environment is to help them develop their economies using principles of capitalism – all boats rise on a rising tide (except, of course, those that are sunk), and “teach a man to fish”.
Thus, the traditional purification method has a number of disadvantages regarding environmental effects, usage possibilities and the work effort.
Other methods for purification of drinking water could be pasteurization and filtering. Pasteurization is performed by heating the water to a high temperature during a long time, which is costly. The filtering is only able to filter out microorganisms being bound to relatively large particles."