Grey Water Treatment and Recycling
Grey water is water from all baths, showers, sinks, wash-hand basins and washing machines, as distinct from black water which comes from the toilet. Current EPA guidelines say that grey water should accompany black water to the septic tank. However if you happen to want to reuse the grey water in your garden or recycle grey water to your toilet cistern for flushing, there is no legal reason not to do so. It is important to bear in mind that if you add grey water to your vegetable patch then you need to be happy that the "ingredients" that you send down the drain with bath water are biodegradable and safe for adding to your dinner menu. Shopping for cleaners and detergents in your local health food shop is a good place to start.
Another reason for wanting to keep grey water out of your septic tank is that it usually isn't all that good for your septic tank bacteria. If a tank has black water only, it tends to work much more effectively and reliably than if grey water is piped into it as well. Yet another fairly obvious reason for not wanting to mix black water and grey water is if you don't have any black water. Anybody with a compost toilet system still needs an effective grey water system to filter and dispose of their grey water, but the best and most cost effective way may not be a septic tank and percolation system.
There are a number of approaches that can be adopted for grey water disposal, as follows:
For all except the first option above, the grey water will need some degree of filtration or separation before recycling or discharge. Treatment options include the following:
1. Combining with black water to your sewage treatment system
2. Recycling grey water for toilet flushing and other non-potable domestic use
3. Reusing grey water for garden irrigation
4. Discharging to ground via percolation (requires careful design and implementation to avoid both pollution and legal issues.
1. A proprietary waste water treatment (or recycling) system
2. An equivalent purpose-built filter or even rudimentary screen prior to reuse depending on the application
3. A constructed wetland or reed bed
4. Soil percolation
If you want help with exploring grey water options or want a grey water reed bed design go to our contact page and email us, or buy a copy of Septic Tank Options and Alternatives for more information.
© FH Wetland Systems, 2014