Potable water is environmentally costly. Dams may have been built and land sacrificed. The water will have been filtered, treated and possible pumped long distances before it arrives at your tap. Potable water is a valuable source. One comment has stayed in my mind which I heard during a recent water shortage. “There’s no shortage of water. There’s plenty of water. It’s just not priced properly and everyone wastes it!”
We use on average 150 litres of water a day. Of this only 2.5 litres are used for drinking. This means that 147.5 litres of potable water are used for purposes for which non potable water could be used.
Grey Water Recycling
Grey water is originally water from the potable mains supply that has been used for washing, bathing, washing dishes or washing clothes. It can be reused for toilet flushing and in some circumstances irrigation.
Grey water will still contain chemicals, organic suspended solids and contaminants such as fat and grease. These can all cause maintenance problems if grey water is collected for re-use without some form of cleaning system.
There are lots of systems available for recycling grey water. There are small localized systems which you can install right away and which collect the bath and shower water and redirect it to the toilet. And there are more comprehensive systems which collect the water from the whole household, filtering it and maybe cleaning it, before sending it to where it is needed.
There is even a system which will recycles the heat from the water that comes out of your dishwasher and clothes washer. A heat exchanger will collect the heat for re-use for hot water and / or heating. The water then enters the grey water system.
Foul water derived from toilet flushing cannot be contemplated unless it is passed though an effective sewage treatment plant to remove suspended organic matter, pathogens and reduce its biochemical oxygen demand. Even then it must be subjected to continuous monitoring for water quality especially contamination by faecal bacteria. The use of a small scale sewage treatment plant and a reed bed system for final cleaning of the effluent is a possible solution to on-site reuse of grey and foul water.
Author: John Wolfendale
Bio: John is a founder of Eco Vida and is passionate about bringing modern design and construction practices to Spain. He believes a home which is warm in winter and cool in summer is largely a matter of design and selective use of materials. He is British and a Chartered Surveyor with 18 years experience living and working in Spain.