LCT: Greywater systems

1 in 3 people (2.5 billion of the worlds population) do not have access to safe water and sanitation. Source: (wateraid.org). As demand for water increases, it is increasingly difficult to maintain the supplies of water to meet the needs of a growing population. On average, a person will use 150 litres per day (see graph below). Sustainable design guidelines recommend that fittings and fixtures reduce this to 80l/p/d through the installation of dual flush toilets and low flow taps and showers. One of the best options is to make use of greywater systems. In areas like the UK where there is high rainfall almost all the year round,greywater systems are less common than drier climates where, in my opinion, it should be a crime not to have a waterrecycling system in every building.

Greywater systems effectively collect wastewater from baths / showers / wash hand basins and washing machines, and use this water to flush toilets and irrigate gardens. (Waste water from toilets and kitchen sinks is classified as BLACK water and must be heavily treated prior to reuse).

Greywater systems collect water and filter it through a series of stages. A septic tank of sorts contains the water and allows solids to settle, while the ‘overflow’ is then filtered – gravel and bentonite clay are some common filtration stages. Thus particles are removed and the filtered water is pumped out for irrigation or into a toilet cistern.

The following list is sourced from www.greywatersystems.co.za :

The pros are:

• Higher savings for everyone
• Good and continuous irrigation
• Food supply is not interrupted
• Gardening and farm irrigation reduced to minimal or zero costs
• Demand for fresh water decreases
• Lower pumping and treatment costs

The cons are:

• Greywater cannot be stored for long or the nutrients in it will break down and it will start to smell bad.
• Quality of water may be different with high levels of boron that can destroy crop and plants
• If vegetables irrigated with contaminated water is eaten raw, it will cause health problems like diarrhoea
• Transmission of some infectious diseases through toxic chemicals from the used water to plants
• Too much nitrogen, sodium, and boron which could cause soil to degrade and groundwater to be contaminated

 

Systems like the MATALA  have in-built pads that filter the water and require no chemical treatments. UV light is used as an effective but environmentally harmless way to kill bacteria.

I do love the simplicity of the SINK POSITIVE…  This is clever design!