Pavers To Collect and Purify Rainwater
by Justin Thomas, Virginia on 09.25.06
Parking lots, patios and other paved areas could one day collect rainwater, purify it then channel it to underground tanks for reuse, say researchers. Professor Simon Beecham, a civil engineer from the University of South Australia, says special porous pavers made of concrete containing specific additives would purify the polluted run-off. He says the water could then be captured in large underground tanks and be used for irrigation, cleaning and flushing the toilet.
"We're trying to harvest a resource that we've not been able to tap into before," Professor Beecham said. Roads, driveways, pathways and the like make up 60 per cent of impervious urban surfaces. The run-off from them causes flooding and pollutes waterways. Professor Beecham says until now, harvesting rainwater from them has proved more difficult than from roofs. His team is developing a system in which porous concrete pavers allows run-off to seep into underground tanks made of galvanised metal or a flexible plastic lining filled with gravel.
A special bonding material ensures the porous pavers are strong enough to withstand the heavy weight of cars and trucks. Additives mixed into the pavers, or into the sand and gravel bedding material beneath them, enables the system to trap pollutants. A paver injected with ferrous hydroxide, for example, traps toxic and persistent heavy metals like lead, zinc and cadmium that come from sources such as car tyres, brake-linings and exhaust. A layer of microbes on fabric beneath the pavers can trap and degrade hydrocarbons such as oil.
Professor Beecham says a layer of granulated activated carbon traps dissolved organic matter from leaf litter that is responsible for algal blooms in rivers. He says the pollutants can accumulate in the pavers over 25 to 30 years, allowing usable water to be caught and pumped above ground for reuse.
He says the pavers could also allow trees, which themselves soak up and recycle water, to grow more freely because their roots have access to more water and air. Problem tree roots could be avoided by using a special concrete device that directs the roots away from the pavers.
The pavers could be seeded with low maintenance native vegetation including sedges. Professor Beecham says one of his PhD students, Baden Myers, is about to construct a full-scale prototype of the complete water harvesting and reuse system, which he predicts will cost 10 to 30 per cent more than conventional paving.
:: Via Hugg via ABC News Online
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I believe there are similar systems already being used around the world. On a visit to BedZED recently I was shown a porous paving system that filtered rainwater through recycled glass before, I believe, storing it for reuse. Unfortunately I couldn't find specific details of this on their website, but general info on BedZED can be found at:
www.bioregional.co.uk
Does this deoxygenate the water?
one of the problems observed with conventional surfacing is that the runoff loses the oxygen dissolved in the water, limiting the amount of oxygen that downstream animals have access too.
So what do you do with the pavers full of pollutants and heavy metals in 25 to 30 years?
A concern I have, as a land conservation professional, is that these kinds of technologies will make people less interested in reducing the overall footprint of their developments. Polluted, heated runoff is but one of the ill effects of development. Fragmentation of the landscape is detrimental to many plants and animals, edge effects increase predation rates, and wholesale conversion of productive ag lands or natural areas eliminates future potential uses of the land.
I second Electric Penguin's question. Do the pavers then become hazzardous waste? Where do they go? Particularly given that, being porus, the stuff will eventually leach out of them if simply dumped somewhere.
I agree with KPod, but that's a different battle and I don't think we should confuse the issue. To me, car culture (though not the car per se) is Treehugger enemy number 1, and I see this technology as an important step in the effort to design compact, livable and attractive communities. Unfortunately, density and greenery are somewhat at odds--this technology could really help readjust that equation.
Most roads last only 25-30 years. If the road happened to be concrete it might be recycled, but not all used concrete is. Asphalt is a little harder to deal with, and if it contains a lot of tar it is already toxic and difficult to dispose of. Those heavy metals would exist 25 years from now whether they were absorbed by the tiles or distributed throughout the surrounding area. The advantage to having them all in one place is that it is easier to dispose of correctly. After 25 years many heavy metals would be into the upper levels of an ecosystem.
Yes Yes fantastic-- if any one has ever been in a DOWN POUR in Los Angeles lately? they can see how water has no place to go!! It is about time we focus on this as well as BLACL topping our cities holding in heat also.
Hell thats the University I went too. They were also responsible for the use of solar powered street lamps in the neighbouring suburb of Mawson Lakes, have a solar powered race car and I did some research there into MEMS energy scavengers for powering sensors without batteries.
There are stormwater treatment systems that use deciduous leaves.
Seems to be an excellent solution to the problem of water shortage. All water is basically the same. H2O. Many of the reserviors that hold our drinking waters are basically lakes with dirt bottoms. Rainwater falls into them, birds live next to them, wild animals drink from them, and fish, frogs, snakes, bugs, worms and more live, eat, defecate, and die in them. Somewhere between the resevior and our water faucets is a processing plant that cleans all of this gunk out of the water before we drink it, make soup from it, freeze ice cubes from it from it, and bathe in it. So, how far a stretch of the imagination is it to make use of runnoff from parking lots, roads, and roofs when we are so often short of water? It's just an added bonus that heavy metals are stored in the concrete for safe disposal years later. I am working on designing a water catchment and cleaning system for a new eco-resort we are building in Alaska and I look forward to hearing more about this and other related water issues.
3 cheers for alternative thinking and innovation.
Does anyone know more about deciduous leaves being used in stormwater systems?
Does anyone know about pre-cleaning runoff water so that algae doesn't devlop in your reservoir?
just show the steps on how the rain water is purified... PLEASE...
Popular Science just came out with an article about French architect Jacques Ferrier using exterior concrete lattice on skyscrapers to house photovoltaic cells and rainwater channels. The lattice would funnel the rain water into a central purification system of the building and provide clean water for the entire building.
Obviously this only would work on skyscrapers. It would be great if Professor Beecham could convert exising pavers for a low cost.... that could increase water availability seriously in impoverished areas like Las Vegas...
Even better is making the ocean on tap with a new invention that is 50% more efficient than current seawater-desalination plants that turns oceans into one big water cooler for mankind. To much stuff to mentions but the July issue of Popular Science has tons of eco-friendly technology highlighted in it that I have never heard of...