Unlike rainwater or stormwater, gray water, or greywater, refers to
water that has been “gently used” from
lavatory sinks, showers, baths and light industrial applications and has not
yet been treated. It can be harvested and
treated for non-potable application such as flushing toilets, irrigation and
cooling tower make-up. Gray water supply can be predictable and steady,
resulting in potentially high water savings. However, it must be treated
properly to produce a water quality that is safe and adheres to local
codes. A proper greywater system
includes the following:
- Collection - When gray water is collected, it must be treated as soon as possible to stabilize and prevent it from becoming septic. Untreated gray water is never stored longer than 24 hours. The collection vessel should have a sloped or conical bottom, allowing for the tank to be fully drained.
- Filtration –Filtration is one of the most critical steps in gray water harvesting system . In addition to removing hair and lint, the system must be able remove particulates to a level that will allow the sanitation process to be effective.
- Sanitation – After gray water filtration, the water is sanitized for use. Chlorination and ultraviolet sanitation methods may be applied to accomplish this.
- Storage – The method of storage for the treated gray water will depend on how the gray water harvesting system is used, the supply and demand, and the available space for the tanks. Typically, the storage system is connected to a municipal water source in case there is not enough gray water supply.
- Monitoring – Sophisticated gray water harvesting systems have programmable logic controllers to automate and oversee the whole process of harvesting and storage.
