Rainwater harvesting is simply collecting rain which falls onto roofs, storing it and using it as a free resource.
The advantages of rainwater harvesting are that it,
- Saves money by reducing your water usage,
- A volume of water is kept out of the storm-water management system, thereby helping to reduce flooding risks,
- Gains Eco-homes rating points for your property,
- And rainwater is better for your garden as it has a balanced ph and is free of chemicals such as chlorine.
Rainwater Harvesting Systems can be very simple such as a water butt located under a down pipe from your guttering that you use to fill a watering can or connect to an inexpensive syphon hose to water your garden or larger more complex commercial systems within office developments, garden centres, hotels etc. In commercial systems the stored water is pumped back to the building to a secondary tank either
Header Tank Systems as the name suggests require a header tank to be installed in the loft, have a high reliability, can easily revert to mains supply if rainwater is scarce and the control system is simple and inexpensive. However the pressure may be too low for some washing machines and flush toilets may take a while to fill.
The majority of commercially available systems are Direct Pump Systems that do not require a loft tank and generate a good pressure suitable for the majority of uses.
Ameon have designed and installed many of commercial rainwater harvesting systems serving a variety of developments and are happy to provide advice on particular applications.
Grey Water Recycling for Toilet Flushing
Typically, about a third of household water is used for flushing the WC. Greywater, the waste water from baths, showers and washbasins, can be collected in a household-scale reuse system and treated to a standard suitable for WC flushing.
Greywater from baths, showers and hand basins is usually clean enough for flushing the toilet with only basic disinfectant or microbiological treatment. Problems can arise, however, when the warm, nutrient-rich greywater is stored, since it quickly deteriorates as bacteria multiply. Systems address this problem by filtration and treatment of the stored greywater. Other components of a system include a pump to get the greywater to the WC (usually via a header tank) and a method of providing mains-water backup for when supply does not meet demand. There must also be a means of protecting the mains water against contamination by backflow (in order to comply with the Water Supply (Water Fittings) Regulations 1999).
Grey Water Recycling for Garden Use
Untreated greywater can be used for garden watering if used immediately after it is produced. The waste water from kitchen sinks and dishwashers is not usually collected as it is too heavily contaminated.
Soil is very effective at filtering out many contaminants in grey water. However water containing soap or detergents does have the potential to cause soil, especially clay based soils, to lose their structure.
Water that has been used with bleach or boron compounds most often found in dishwasher detergents should not be used. Grey water should not be used for watering edible crops.
Reed Bed Sewage Treatment
Reed beds are useful secondary and tertiary sewage treatments where the space is available or a high level of effluent discharge quality is required. They also have the advantage of providing a very low maintenance, aesthetically pleasing and ecological beneficial resource. As a wildlife habitat they are particularly attractive to invertebrates such as dragonflies and damselflies.
Treating sewage usually involves a combination of different methods to separate out solids, deal with pathogenic (disease carrying) organisms, and remove nutrients.
The first stage (primary treatment) is the separation of most of the solids from the liquid effluent, usually by some kind of settlement chamber. The most common example is the septic tank. These are a robust and economic option if used properly. Most of the solid material will either sink (as sludge) or float to the top (as crust), leaving the effluent between to flow out to a secondary treatment stage.
A common secondary treatment system is a leachfield. This is a system of perforated pipes laid in underground gravel trenches. They are unsuitable for clayey soils or areas with a high water table. The liquid effluent percolates through the gravel, where solids are removed and digested by micro-organisms, leaving the liquid clean enough to filter into groundwater.
Vertical flow reed beds are another kind of secondary treatment. The effluent from a septic tank (or similar) is percolated through a tank containing layers of sand and gravel planted with reeds. The reeds help bacteria to break down the pollutants and make the beds attractive to wildlife. Horizontal flow reed beds are usually used as a third stage of treatment where very high quality effluent is required.
The Centre for Alternative Technology has a tip sheet 'Constructed Wetlands and Reed Beds' explaining the construction of reed beds, and where and when they are appropriate.