water purification

[stewartkelly1]

The availability of pure drinking water is more of a crisis than oil shortages.

I was thinking a low cost technology would be to use both phytoremediation and bioremediation technologies to filter water of both sediment and heavy metals.

For instance scrap iron and ferrous bacteria species could be used to remove arsenic; as well as some water plants.

You could also embed algae to filter water.

[Korey King]

I'd argue that the decentralized availability of water (beyond piped infrastructure, water sheds, ponds/lakes/oceans) is a more pressing concern than purification overall, but keeping to the thread as it's as good a start as anywhere:

a low cost technology would be to use both phytoremediation and bioremediation technologies to filter water of both sediment and heavy metals.

For instance scrap iron and ferrous bacteria species could be used to remove arsenic; as well as some water plants.

Sounds good in theory. Application is another story.

Re: scrap iron/bacterial remediation, this shows promise but it's not independently practical. It requires the iron to be crushed and sieved to 1/10th a mm, requires cultivation of specific bacteria species, and just can't be readily applied anywhere without building the infrastructure where needed, or shipping everything needed wherever -- counter to the goals here?

But as far as plants go, the Pteris vittata fern sucks up arsenic better than anything else I know of.
See: Arsenic Hyperaccumulation by Pteris vittata L. and Its Potential for Phytoremediation of Arsenic-Contaminated Soils (http://lqma.ifas.ufl.edu/Publication/GK-05.pdf).

A few notables here is that 1) it hyperaccumulates arsenic, 2) it's a fern so it propagates by spore not seed (faster, wider, hands-off), and 3) it's actually considered an invasive species -- which suggests it's able to thrive in a huge variety of ecosystems. Just about the perfect solution to arsenic contamination.

Problem here is there's a company that actually has a patent on this plant (http://www.freepatentsonline.com/7065920.html). Absurd as it is, Edenspace (http://www.edenspace.com/products/edenfern.html?expandable=1) theoretically has exclusive rights to use a plant to clean up contaminated water, and they're not cheap -- they sell each plant for about $3.

Anyone know of any others?
There's plenty of options provided naturally.
I'm sure there are many plants and fungi and other microorganisms ready and waiting to get the job done.

Beyond that, distillation is still one of the cheapest and easiest ways to purify water.

One of the better examples of a DC3D is the Watercone (http://www.watercone.com/index.html):

http://www.watercone.com/pics/jemengruppe.jpg

The Watercone® is a solar powered water desalinator that takes salt or brackish water and generates freshwater. It is simple to use, lightweight and mobile. The technology is simple in design and use and is discribed by simple pictograms. With up to 1,7 liters (nearly 2 quarts) in 24h the Watercone® is an ideal device to cover a child`s daily need of freshwater.

“Next to eliminating salt from basic sea water, the Watercone also does NOT transport highly toxic elements such as mercury, arsenic or cadmium from the pan into the cone.”


...but they've already been snatched up and ready for distribution.

It is a pleasure to inform you I now found a new partner in spring 2008, the Mage-Watermanagement GmbH from Munich Germany. The company licensed the Watercone® and will start cost effective mass production and world wide distribution in 2009.


Don't have any data on production costs or costs-to-market but it looks like it (or similar devices) would be fairly cheap.

[tom]

The Lifesaver 6000 is promising new technology. It currently produces freshwater via a nanotechnological filter that costs ~12.5 center per gallon of fresh water when you amortize the filter cost over it's expected useful life of 6000 liters.

As these prices come down, this will be more affordable to the developing world.

Also -- one very low-tech solution is the planting of more fruit trees. Eating water-rich foods dramatically reduces the need for water from other sources, and the trees provide a host of other benefits, including shade, filtration, prevention of soil erosion, etc. All for the cost of a seed and the labor to plant it.

[peopleunit]

http://www.youtube.com/watch?v=hb0xf3mRbJM

I think production costs could probably be reduced substantially, and water quality improved even further through the use of activated charcoal as a final filtration stage.

Quoting the description of the video on YouTube...

The BioSand Water Filter is an adaptation of slow-sand filtration that is designed for use by families at the household level. This award-winning water filtration technology was developed by Dr. David Manz, a former University of Calgary professor.

The filters are a proven, effective, and inexpensive technology. From start to finish the filters can be constructed in roughly 10 days, at an average cost of $100, which covers the raw materials, construction, transportation, supervision, training for the family in filter maintenance and personal hygiene, as well as monitoring and evaluation.

The filter removes organisms responsible for diseases spread by water, such as cholera, typhoid fever, and amoebic dysentery. The filter also strains out particles causing cloudiness, and much of the organic matter responsible for taste, colour, and odour.

One of the UN Millennium Development Goals is to reduce, by half, the proportion of people without access to safe drinking water and hygienic sanitation by the year 2015. Samaritans Purse is helping make this possible. Already more than 70,000 BioSand Water Filters have been installed, bringing safe water to an estimated 560,000 individuals worldwide.

The Filtration Process

The filter is very durable, constructed from concrete, sand, gravel, and PVC piping. These materials can be found in almost every country and enable community members to help construct the filters on location.

Water is poured into the top of the filter and flows down through sand. Water that requires filtration usually contains various types of organic matter, sediment, and living organisms. The water first passes through the diffuser plate, which reduces the disruptive force of the input water and large debris, and protects a delicate biological layer. The filter sand functions as a physical barrier that traps particles and larger organisms, causing them to accumulate in the uppermost layers of the filter. Organic material and organisms caught in the sand eventually develop into a dense population referred to as the biological layer, or schmutzdecke.

As the water passes through the biological layer, microbial contaminants such as parasites, bacteria, viruses, and organic contaminants are consumed by the organisms. The filter is designed to hold water above the top of the sand to sustain the biological layer while the filter water is not in use. This provides the constant aquatic environment that is necessary for the organisms present in the biological layer to survive.

The fine sand acts as a microscopic sedimentation bed as the water passes through the filter, helping remove cloudiness, odour, taste, and harmful micro-organisms from the water. The size and shape of the sand grains are critical to the formation of the biological layer and therefore the effectiveness of the filter. Sand is specifically selected and prepared to achieve proper filtration. By the time the water reaches the layers of coarse sand and gravel at the bottom of the filter, 95 to 99.0 per cent of microbial contaminants have been eliminated by the BioSand Water Filter.1

The filtered water flows out of the spout and is collected in a safe storage container to prevent post-treatment contamination. The average flow rate of the filter is one litre per minute, which allows for 60 litres to be filtered per hour, enough to provide a family of eight with sufficient water for their daily drinking, cooking, cleaning, and hygiene needs. An individual requires a minimum of 7.5 15 litres of water per day for basic needs2, which is well within the capabilities of the BioSand Water Filter.

Maintenance

As the filter is used, the biological layer matures and thickens, causing the flow of water through the filter to slow. Recipients of filters are trained to watch for decreased flow and can renew the filter simply by skimming off any debris from the top of the sand, and by gently stirring the sand to break-up the biological layer. The quality of source water will determine how often this process is necessary.