Water Recycling

The increasing incidence of water stress and water crises over the last few years has made “Water Recycling” a hot issue. Penang has very few water catchments and it draws 80 % of its water needs from the Sungai Muda which has its origins in Kedah. The 1997/98 El Nino laid bare the fact that water will be a major issue for Penang in the 21st Century. With the ever increasing demand for water placing a potentially undeliverable demand on the available resources, the time has come for all to play a part in water conservation. WWP is formed to educate and promote the “Wise Use of water”. WWP promotes a new ethos within society which should now see water as a limited resource in a similar way to gas or electricity, rather than as an unlimited one. The days of an unlimited supply of potable water are over, making way for water recycling and the concept of dividing water needs into potable and non-potable uses. An area of particular relevance is within the domestic environment where currently all water usage is of a potable standard. Actual water consumption that requires water of a potable standard is of a few percent of the total, typically 4-5%.

The potential for the remaining water to be generated through recycling within the house is extensive. The limiting factor in any such application is based on the quality and quantities of the various waste generated within the house. One basic division is made with water from the WC being separated from the rest, this being referred to as black water. The remaining waters are generically referred to as greywaters, excluding water from the kitchen sink and washing machine due to the grease and high chemical loads these produce.

The level of treatment required varies considerably and is ultimately determined by the criteria that are established for each application. No criteria currently exist within the UK, although the Building Services Research and Information Association (BSRIA) have recently released some guidelines which may in the future become the basis of the water reuse standards adopted in this country. In terms of non-potable reuse opportunities, which are referred to as a medium level risk, the guidelines suggest the total removal of faecal coliforms as the only criteria for reuse. Standards such as these can be effectively achieved by simple filtration followed by disinfection processes, offering a relatively simple treatment scheme. If, however, more stringent guides are adopted which follow the example of America, where no odours or colour are permitted, more extensive treatment would be required. The current thrust within the UK is towards the reuse of greywater to flush toilets. This is an attractive proposition as the quantities of greywater produced roughly match the volumes required to flush the toilet. This negates the use of stored rainwater which has been adopted in other countries, reducing the need for large storage volumes, which are required to cancel the effects of intermittent rain fall. Economic assessment of the units currently limits their application to large dwelling such as hotels and colleges to ensure the payback periods are sufficiently short. A number of commercial units are available based on this idea-all use standard filtration devices with disinfection , usually via chlorine blocks. Early indications are that such units may provide a adequate level of treatment for the application of toilet flushing, saving roughly 30% of water supply requirements to a domestic house.