I’m wondering if anyone can recommend any good resources for working out the size of biofilter needed for a certain set up please?
We are based in the UK and plan to set up a biofilter and constructed wetland in our market garden for a hand/pot washing sink and possibly for an outdoor shower later on down the road. I’ve looked at your great page on biofilters but I’m wondering if you can point me to some more detailed info on how to size the filter/surge tank.
Thanks very much
Do you have land to infiltrate the water into? So long as you’re more than 3 feet above the groundwater table, and not too close to creeks or other water ways (100 feet), you can safely and easily infiltrate the water into the soil using in-ground mulch basins. This is more effective and easier to maintain than a separate biofilter. I would recommend it unless you are not able to use the soil for some reason.
If you can’t infiltrate into the soil then you should size for ease of maintenance. There is no “treatment” needed to put greywater into a landscape, since any nutrients in the water would benefit the plants nearby. You’d want to size the surge tank, if you need one, to accept no more than 1 day’s worth of greywater, otherwise it gets really stinky. From your description it doesn’t seem like you would even need a surge tank though… unless you have really high flows on occasion (?)
Outdoors showers work great if you can have the water naturally flow to a mulched landscape planted with suitable plants. No need for piping!
Hope this helps!
Thanks for your reply! We are hoping to dig a pond onsite to act as a reservoir for irrigation water fed from the spring and so we would like to recycle the water into that rather than infiltrating it into the ground. We’re also not sure at this time what height the water table is (we haven’t yet taken on the tenancy and are just researching to make some proposals to the landlord).
So we’ll probably go for the biofilter. Thanks for the advice about sizing though – I was coming at it from the wrong angle!