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Environmental Issues By Alan J Hartley |
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Waste Water Recycling |
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We are told that we are getting drier summers and wetter winters that are giving some parts of the country problems in maintaining a regular water supply in prolonged dry spells. On a domestic level there is much that we can all do to reduce our demand for fresh water in the garden (see article) and there are different ways that we can take advantage of water that we don’t usually think about using or re-using. Basically wastewater in the home falls into two categories, Grey water and Black water. Black water is the discharge from toilets and there is little that can be done with this with regard to re-using the water unless you have the space and want to go to the trouble to install something like a reed bed water treatment system. In the right place such as a large campsite or secluded farm this can be a very “GREEN” way to put water back into the water course and dispose of sewage instead of a cesspit. Grey water is normally classed as coming from baths, showers, hand basins, washing machines, dishwashers and sinks. Much of this water can be collected and re-used to flush toilets especially as they are a heavy drain on water supplies typically requiring a third of the regular domestic water supply. However, it is not normal practice to use dishwasher water, or water from kitchen sinks, as this is liable to contain a lot of waste matter that would cause problems. Another problem with Grey water is that it is rich in chemical nutrients that mean it can’t readily be stored in a tank awaiting use without some sort of basic treatment, or else large quantities of bacteria will develop. Grey water can be used immediately on the garden without too many problems so long as it does not have a lot of chemicals such as detergents in and is not used on food crops.
One big advantage over other types of water is that it is clean, free of chemicals such as chlorine and yet safe. Indeed it is better for watering most plants in the garden than tap water. With gardeners in mind, a decent sized storage tank could mean that water is available in the garden for plants when there is a drought with an accompanying hosepipe ban. In theory it can save money on water bills, but there could be a fairly big installation cost as well as some running and maintenance costs. Socially it has to be a good thing, as it will reduce demand on tap-water supplies as well as lightening any problems created by storm surges. Integrated Rainwater Harvesting systems are available in two types: Header Tank Systems and Direct Pump Systems.
With both types of harvesting system a large underground storage tank will be needed that can be as big or as small as required that is connected to all house downspouts. To get the water from this tank up into a header tank will necessitate a high-pressure water pump. Even going back two or three decades this would have been impractical as expensive, power hungry, multi stage pumps were needed to get any pumping pressure, but nowadays even low power demand pumps, costing a couple of hundred pounds, can give a pressure of several bars enabling them to pump water upwards many metres. |
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One
type of wastewater that many of us already harvest is rainwater. 
Direct
pump systems tend to be used in the garden for watering plants, or car
washing, but systems with a header tank will be partially plumbed into
the house system with safety precautions taken against contaminating the
mains water. With a header tank installed and the proper pipe-work,
water is available for household use as well as garden for things like
flushing the toilets, or even washing machines and baths.