I'm reaching the point in my house build where I need to start finishing these type of projects. I hope some people find this post helpful and interesting. We live on the top of quite a big, rocky hill and there is no chance of digging a well or borehole. Water is supplied to our little community by a local farmer who tears the arse out of the price. USD 4.16 per cubic meter / 260 gallons. It's very expensive. Our rainy season runs from December to March. Sometimes in to April, so we have about 8 months of the year with no rain. Collecting rain water on it's own isn't enough. So when I was designing our house I incorporated a water recycling system. I decided to recycle both grey and black water, here's why. Many people don't like the idea of recycling black water. Some countries won't even allow it. But, I wanted to re-use every drop of water that runs through our house, to water the garden. I've had quite a lot of experience with building Koi ponds and their associated biological filtration systems. Effluent is effluent, doesn't really matter which animal it comes from. The process of dealing with it is the same. It all relies on the Nitrification process. Namely two types of bacteria, Nitrosomonas and nitrobacter. They convert nitrites and ammonia in to nitrates. These bacteria live everywhere on the surfaces of anything submerged in water. All that is needed is to provide them with oxygen and a large surface area on which to multiply. First step in the process is to slow the flow and settle out all solids, just like a normal septic system. Once all the solids have been removed, the water needs to be oxygenated and cycled through biological growth media to allow the bacteria to do their thing. Further information here: https://www.ecos.ie/wastewater-nitrification-how-it-works/ So, I decided on this design. Grey and black water from house flows in to tank 1. This tank is basically the first chamber of a normal septic tank. Instead of getting clever and having to build baffles inside the tank, I just used two tanks side by side Much simpler than trying to figure out a way of building baffles without drilling holes in the tank. I designed this with as few holes as possible and most holes are at the top of the tanks where pressure is least. We want the flow to be as slow as possible so all suspended solids fall out of suspension to the bottom of the tank. The inlet is 4" PVC sewer pipe with a horizontal T fitted so the effluent entering the tank does not stir it up and cause currents. Tank 2 takes the place of the second chamber in a normal septic tank. The outlets of both tank one and tank two are placed in such a way that surface scum and foam cannot flow out of the tanks to the settlement tank. See image below. Our kitchen waste water will also flow through a grease trap to stop as much of that ugly stuff as possible from getting in to the system. Tank 3 Nothing clever here. Just more settlement. I decided to go with another tank for settlement as I really don't like the idea of having to clean out any of the tanks. Swimming in shit doesn't feature highly on my list of fetishes! Also, any suspended solids still in the water are detrimental to the bacteria colonies. Tank 4 and 5 are biological filtration. They will have a circulating pump attached to circulate and oxygenate the water through shade cloth which makes a very goo biological growth media. Tank 6 is a simple storage tank which will be connected to an irrigation pump. A float switch and automated garden irrigation system will start and stop the pump whenever the tank is full / empty. Tank 6 will have an overflow going to a soak away just in case anything goes wrong. Tank 1 and 6 are 5000ltr / 1300 gallon The rest of the tanks are 2500 ltr / 660 gallon Some pics of the build so far... I have placed the tanks half way in the ground simply to make it easier to work on the system and maintain it. Removes the need for a ladder. 4.5" brickwork surrounds the submerged part of the tanks to stop them collapsing. I used 4" PVC sewer pipe for all the inter tank connections. Then made fiber glass "collars" to seal against the sides of the tanks. I can't find the proper through tank 4" fittings in Zimbabwe and I didn't want to use the steel ones the tank manufacturer provides as they will rot. So I'm just going to seal between the tank wall and the fiber glass with some silicon or some other goop. When the tanks fill, they expand so there will be pressure holding the side of the tank to the fiber glass. Don't think they will leak! I bought stainless steel bolts to bolt the fiber glass to the sides of the tanks but have decided against it. The least number of holes the better. The circulation pump I am using is just a little 1/2 horse power high flow, low pressure pump. The plumbing for that will be 50mm / 2" class 10 PVC I'll make my own venturies and spray bars for the inside of tank 4 and 5 to maintain oxygenation. Being off grid and relying on PV power, I wanted a small pump for the job, but the smallest one I could get was this one. The pump ideally needs to run 24/7 as the bacteria colonies don't like running out of oxygen and die off. I might put a timer on it and turn it off for 6 hours at night to preserve batteries on the PV system. But the pump doesn't use much more power than a fridge so I'll have to test that when done and see how we go.
Thanks for sharing/posting the images! Septic systems in Alaska work very much like your layout - not because of rock, but permafrost.and frozen ground for most of the year... The three 'working' chambers are in a single container for ease of burial. The output is clear water. Not potable of course, but can be discharged. Pumped / inspected (by ordinance) once a year, these provide for a small but thriving business for those small businesses that own pumper trucks.
https://www.amazon.ca/Dixon-60405-P...+inch+POLY+TANK+FITTING&qid=1611601063&sr=8-6 https://www.amazon.ca/Hayward-SP149...11601160&sprefix=2+inch+pvc+un,aps,259&sr=8-1 No places to purchase these items for inter-tank connections ,union needed to do maintenance if needed Sloth
Basically the same thing municipal sewage plants do before they pump it back in a local river.....if it wasn't fairly clean at that point, the wouldn't be allowed to do it. The prohibition on 'black' water is for untreated use. How cheap are storage tanks there ? I use two 1500 gallon poly tanks for storage from my spring....they ran about a dollar a gallon to buy them at the time. Seems for the price you pay for water, a LOT more storage for rain water is in order.
View attachment 84470 Hi Sloth, Yeah we can get all that stuff locally but I just couldn't find 4" fittings for the sewage pipes for inter tank connections. The rest is easily available. Thanks.
Lowe's, Home Depot, Grainger's and many others have threaded PVC fittings. How readily those vendors can be found in Zim is a different matter and shipping might be an interesting question, too.
3" interconnects is what we use here after the main 4" black in . My system is very similar to Dave's, but all gravity . Just did a cleaning of the system last year and installed risers from the tanks. I get ten years between , and next time i'll hire it out,, age thing for myself. Sloth
These toilet drain deals are 4" with a flange deal for bolting in a tank, Little silicone Boom there it is !!! https://www.lowes.com/pl/Toilet-fla...air-Plumbing/4294935833?refinement=4294412895 Just throwing out 4'' ideals, Sometimes one must improvise
