Gray Water is defined as all the water which originates from a house or a flat except from the commode or WC. Gray water includes, water from showers, faucets, kitchens, dishwasher and clothes washing machine. Typically, gray water has highly reduced organic contaminants and does not contain high levels of bacteria or nitrogenous compounds compared to the WC water. It typically contains a larger amount of salt than the input water and detergent. This water is very amenable to recycling through simple treatment and disinfection. The thus treated water is easily used for flushing and gardening. However, some precautions should be taken before reuse.
The infrastructure requirements for recycling of gray water are as follows:
It is best to plan for the gray water system at the concept stage.
The gray water system is not as elaborate as a sewage system.
It is best to disinfect using an appropriate filtration/Disinfection System.
The other effects are that the Black Water (Water from WC) system is reduced dramatically in size. It can be treated with an Anaerobic reactor and then discharged in Public Sewer. The major advantage is that the sewage treatment system size can be reduced dramatically.
For gray water segregation and recycle, extra cost is incurred for separating the gray water and black water lines.