Greywater and Rainwater Recycling
Greywater vs. Rainwater as Recycling Water Options
The recycling of greywater, which is the untreated wastewater generated from showers, kitchens, sinks and laundry, is a controversial topic in water conservation (Jamrah et al. 2008). It is estimated that greywater makes up 50-80% of residential water consumption (Jamrah et al. 2008), creating large conservation benefits if cost effective methods of recycling are developed. Current recycling techniques require large, expensive infrastructure to be constructed which would be unpractical for villages like Dunnottar. However, greywater reuse can be a practical and efficient use of water at the individual level. For example, several household applications link used sink water to run through the toilet tank before it is released into the wastewater stream, and efficient means of conserving water. There are also health concerns with respect to trace contaminants and bacterial pathogens that may limit the uses of greywater recycling in a residential area. In a study of greywater contaminants, Birks and Hill (2007) found high levels of human bacterial contamination necessitating biological treatment and disinfection if the water is to be used for recycling. The complexity of eliminating these contaminants makes greywater recycling unlikely to be cost effective in the Village of Dunnottar.
A more realistic water conservation method for the Village of Dunnottar would be the installation of rain barrel catchments. This could be done on private residencies at the homeowner’s initiative, as well as installed in public areas. The following formula is often used to calculate rainwater collection:
1 inch of rain on a 1000 square feet roof yields 623 gallons of water; or
1 millimeter of rain on a 1 square meter surface yields 1 litre of water.
Rainwater catchement is a significant conservation method on a small scale residential level, easily providing water for irrigation, gardens, toilets etc.
References:
Birks, R., Hill, S. 2007. Characterization of indicator organisms and pathogens in domestic greywater for recycling. Environmental Monitoring and Assessment 129(1-3): 61-69
Canada Housing and Mortgage Corporation., Veritec Consulting Inc. 2003. Rainwater harvesting and greywater reuse. Technical Series 03-100. www.cmhc-schl.gc.ca/publications/en/rh-pr/tech/03-100-e.html
Jamrah, A., Al-Futaisi , A., Prathapar, S. et al. 2008. Evaluating greywater reuse potential for sustainable water resources management in Oman. Environmental Monitoring and Assessment 137: 315-327
Photo: http://www.rfcity.org/eng/Stormwater/RainBarrelProgram/RainBarrelProgram.htm
