We have a small, Certified Naturally Grown market farm (2 1/2 acres of annual fruits/veggies, alpacas, ducks, gees, honeybees, and about 1/3 acre of perennial crops that are to the stage of producing marketable quantities - mostly asparagus, with lots more in various stages between dreams and producing enough for us but not for market). We're finally making some progress on our summer kitchen, which where we'll also relocate our veggie washing. Our soil is extremely porous - it's not sandy soil, it's playground sand, except where we've been working really hard to improve it, where it's reached the status of soily sand. We've got a 7 acre pond and about 13 acres of swampy woods on our property, a major river across the road, and a major ditch draining into it making up one property line. In our lower areas, the water table is close enough to the surface that if someone jumps next to you, you can fell the ground bounce up and down on the waves it makes.
Thus, we are very cognizant of any kind of nutrient runoff from our operations. Right now, when we wash veggies, we do so in plastic tubs, and carry the water to various plants in need of a drink. But it's very heavy, wet, and time consuming during a very busy/hectic period of time. With the new summer kitchen, we'll have a proper washing sink, and I'd like to take care of the water via a greywater treatment system. I don't want to tie the sink into our septic tank, mostly because there is a lot of water generated in the washing of veggies that would tend to overwhelm it, and there's also a LOT of sand/dirt in that water, which would cause obvious problems. We'll also use the kitchen for hosting events on the farm, so there would periodically but irregularly be moderate quantities of typical kitchen sink type greywater, with attendant grease and whatnot.
Our primary goal is to not allow nutrient-laden water to pollute the swamp, ground water, or surface water in the area. If we can reuse the treated water for irrigating something, that would be an added bonus.
So, the challenges would be how to deal with very large surges - three quick surges of 20-30 gallons each could happen within a couple minutes of each other; how to collect the sand in some easily maintained manner so it doesn't clog up other parts of our system, such as a constructed wetland; and how to deal with the feast-or-famine nature of the water availability (at the peak of the season, we'll go through 400+ gallons of veggie washing water on a friday, and maybe 100 gallons on a tuesday, but none the rest of the time.
I think a wood chip/worm biofilter would work well for dealing with the grease and whatnot if we could get the bulk of the sand out first. We have a couple of worm bins anyway where we could finish off the partly-decomposed material when we maintain that filter. But dealing with the rapid and large surges seems like it would need to happen first and perhaps need a bit more than the typical 55 gallon drum surge tank...
Has anyone else tackled a similar issue with success? Even if not, any ideas/suggestions?
Is there any way to put some sort of diverter system underneath the sink, so that 'ordinary' kitchen greywater with grease and soap can be sent to a greywater system, and the veggie washing water can be diverted to either a hose pipe or a tank near your plants?
Mulch basin for the veggie wash, with a settling tank or pond to collect the sand and surge. 500 gallon capacity with a slow drain so it filters through the mulch over a day or so. Wateringtrees or shrubs somewhere. What fruit trees do you have that like water during market season?
Diverter valve to run regular kitchen waste through the septic.
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Thanks for the thoughts so far. To respond to some of the questions/thoughts:
Right now, the summer kitchen is just a roof over sloping land just downhill from our "grazing garden." That's grazing for us, not the deer, hopefully! The fill to level the floor hasn't even been brought in yet, let alone any flooring, counters, fixtures, etc. So there are no restrictions at this point on what I can do regarding installing diverter valves and the like.
Currently, there are no fruit trees or anything downhill from the summer kitchen location. It's location was chosen primarily due to traffic flows around the property. I don't want to deal with a pump that might break. Unless I use the greywater to irrigate mature white pines in the wind break, which rarely need any supplemental water, anything watered with it will be chosen and planted to accommodate the greywater, not the other way around. I can go two directions with it, down about 120 horizontal feet of about 10% grade, or down about 40 feet of 40% grade, to reach what to me are logical places for the water to end up, neither of which have been developed at all yet (and I have to mow them. I hate mowing). I'd welcome suggestions for the final use of the water. Would need to be frost tolerant, because the bottom of the hill is a severe frost pocket.
I'm concerned with diverting the veggie wash water directly to plants/ground, because of the proximity of the swamp, and the water table. Our infiltration rate is so high that water flows vertically down through the sand faster than it flows horizontally along the ground anywhere that isn't heavily compacted by livestock or vehicle traffic. Our garden soil is heavy in nutrients because we add large amounts of compost, poultry-, alpaca- and horse manure, and worm castings, a fair bit of greensand and aragonite, and a bit of boron to correct its deficiencies in various micronutrients and organic matter. So, when we're washing veggies, and particularly root veggies, there's going to be a lot of nutrient runoff in that wash water that I want to be used by whatever we plant, but not make its way past that. Or settled out and returned to the garden from whence it came.
I don't want to divert to septic for two reasons: 1) septic tank is uphill. Well, the tank itself is probably close to level with the summer kitchen, but, still... and 2) getting the permit to add a building to our existing septic is difficult, time consuming, and expensive in our county (in part because we are the absolute northeast corner of the county, and the county seat is in the southeast quadrant of the county. Inspectors hate coming out that far in general). However, I could see diverting "regular" kitchen wastes to a wood chip biofilter, which would drain to the rest of the greywater system, while the veggie wash water bypasses the biofilter. Does that seem logical?
How would you go about constructing the settling tank so that it drains slow, but doesn't clog with the sand and such, and removing the settled solids is fairly simple and pleasant?
By the time the water gets to the bottom of the greywater treatment path, it will end up in a pretty bad frost pocket, which limits what veggies I could grow in a wicking bed there. Leafy stuff, late blooming stuff certainly... 'Tis a possibility to consider, as I would like to reuse the water productively, even if that is a secondary goal. Not practical to get it back to the same beds the veggies came out of - the annual veggie garden is 2 1/2 acres, a fair bit away, and uphill from the kitchen
I was thinking about a settling tank design. I want to have a constant flow so there's no risk of water hanging around to go septic before treatment, while still moving slowly enough for sand to settle out. Perhaps I could make a large baffled tank, sort of like an evaporator pan for making maple syrup. It would function as both a surge and settling tank, as the water would travel through it slowly enough for a long enough distance that the sand and such should settle out. If I made each channel between the baffles about the same width as a scoop shovel, it would be very easy to clean out. But the water wouldn't stop moving entirely in the settling tank...
Diego Footer on Permaculture Based Homesteads - from the Eat Your Dirt Summit