Rainwater recycling
Even during the Summer months, a surprising amount of water falls from the sky, providing a free resource that is unaffected by hosepipe bans or drought orders. Although there is an initial infrastructure cost of installing storage tanks, this can soon be paid back in reduced mains water charges.
Glasshouse roofs and metal framed buildings make an ideal rainwater catchment area, with a potential monthly yield, even in Summer, of 60 litres of water for every square meter of roof catchment. A single 40m x 9m glasshouse roof could yield 21,000 litres of rainwater per month.
For nurseries and garden centres, above ground steel sectional tanks are normally used, which provide a large storage capacity at a relatively modest cost. Where there are multiple roof areas for catchment, Access can provide advice on connecting the seperate buildings to a single tank.
Short payback and water security
In fact, a covered storage tank can cost as little as £25-£35 per m3 of water stored. With mains water running at £1 per m3 in some areas, the tank and cover can pay for themselves in just 30 refills. Access Irrigation has many years experience in designing rainwater catchment and irrigation systems.
In addition, rainwater harvesting provides independence from the mains drinking water system. As drinking water supplies come under more strain, DEFRA and water companies are already starting to consider prioritising how drinking water should be used. A DEFRA spokesperson was recently quoted as saying "Mains water is primarily for domestic users, and more mains water is made available for non-domestic [ie. irrigation] purposes only if there is enough to go round."
Hygiene
Good general nursery practice can help ensure that the harvested rainwater stays as clean as possible, minimising any disease issues. All roof catchment areas and gutters should be kept clean, and leaves cleared away regularly.
Access can supply pre-filters to ensure that any large debris (typically about 0.6mm) is filtered to drain before entering the tank. Water is normally calmed on entering the tank to ensure that any sediment is kept undisturbed. Overflow skimmers can also be used to ensure that any small light particles, such as pollen, are skimmed off the surface. Tanks should also be fitted with lightproof covers.
If necessary, the rainwater can also be treated as it leaves the tanks, either by conventional filtration , slow sand filtration or by UV or chlorine systems.
