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I'm looking for a simple blackwater treatment system for a house in Thailand. We are not restricted by govt/council regulations, however a dry composting toilet wouldn't be acceptable for cultural reasons.

Worm based systems interest me, particularly the one below, which we could build from concrete rings.


http://www.omick.net/other_toilets/other_toilets.htm
Below are some relevant points/questions:
- The system would be for a single toilet, not greywater, another toilet may be added in the future.
- The toilet is not a standard flush, instead a small bucket is used for a manual flush using only a couple of liters.
- Our block is about 1.6 acres.
- We use well water for everything except drinking. The local (unenforced) rule, requires septics to be 50m from a well. Can anybody advise a safe distance for a worm system?
- Our area is tropical, with about 2,000mm rain. It's never flooded but the water table get's quite high in the wet season.
- Can anyone recommend min safe depths for sub soil drainage?

I hope I haven't provided too much information, Any help is much appreciated.
 
Dale Hodgins
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Posts: 6795
Location: Victoria British Columbia-Canada
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    You haven't mentioned whether your land is level or steep or whether it's all cropland. If you have a relatively level spot where you grow firewood and other nonedibles your sewer outlet could be a valuable resource to fertilize fast-growing and heavy feeding trees such as leucaena. These trees are heavy feeders and produce prodigious amounts of animal fodder when they are small or you will get 6 inch diameter poles within about five years. If you have access to large diameter bamboo you could use  rebar to knock the centers out of some and use this as a weeping tile just a few centimeters below the surface. You'll want to drill 3 cm holes along the length of this pipe. Some sort of settling tank for solids could precede this weeping area. The roots of your tree crop will clog the system in time but these biodegradable pipes will be easy to replace. The small cost of bamboo will easily be offset by the value of logs that you produce. In order for this system to use the nutrients efficiently and to avoid groundwater pollution it would be best to have a tank at the very beginning of this system which can have its flow turned on and off. Whenever there is heavy rain, interrupt the flow. When the water subsides begin draining the tank. This turns your septic tank into an irrigation holding tank. Leucaena has been grown for years in Australia and Malaysia. Their departments of agriculture should have plenty of information. You probably have some heavy feeding native trees where you are. Find out what grows naturally around poorly managed sewage facilities since heavy feeders will dominate in such an environment. Also be sure to investigate any plant you introduce to make sure it's not invasive.  If you decide to go with just a regular septic tank and weeping bed system your best information concerning soil depth and watershed protection check government websites for northern Australia, Singapore, Hong Kong and other tropical places which are likely to enforce some sort of sensible environmental protection. If you choose to go with the first system I suggested let me know and I will help you with every step in the design. Your only cost will be that I will want regular updates as to how well the system is working and how fast your trees are growing so that I can pass this information on to others. Good luck and happy digging: Dale 250-588-3366 I'm in British Columbia, Canada.
 
                                
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Hi Dale, thanks for the info. We are growing a variety of trees, mainly fruit.

We do have bamboo, probably enough on the property to use. The block is fairly level, with a gentle slope in the lower part (furthest from the house).

My main concern is the level of the water table. We only go to the property on the weekends. I took a look on Saturday, the well level is now less than a meter from the surface and this is the high part of the block. If it was the same level throughout, then the lowest part of would be underwater, which it isn't. Nonetheless, using a tap system may not be possible as the system may over flow.

I'd also been considering using bio-char (burnt rice husks) at the bottom of the tank and possibly in trenches as you suggest, as water would flow easier through the char than our clay soil.

Leucaena is common here, however we don't have much room for planting. I had been considering putting the worm farm next to a young mango, as these have deep roots. We grow a lot of bamboo, which is a thirsty, heavy feeder however the roots are no more than 600mm deep. If I used biochar, it may draw water up to the roots?

 
Joe Woodall
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Dear Sir,

For a remote location, without interference from government inspection, I would probably do as we have done before , build onsite & in place - a ferrocement septic tank designed with 2 chambers inside it and a cement lid. I would then pipe the effluent into trenches, 4 feet deep. These trenches will have been filled 1 foot high ( and mounded high in the center to form a dome shape) , with old "PET" bottles ( Imagine Used Plastic Water Bottles Or 2 Liter Soda Pop Bottles Perhaps )  covered over with a sheet of 6 mill plastic, tucked to the bottom of the trench,  with pitch fork poke holes on the sides before plastic sheet installation but,  don't poke holes on the  top part of your plastic , so as to allow water to drain from the sides into the soil and not allow earth to fill the bottles, from the top. When back filled with soil to ground level , the trenches ( when connected to the septic tank by a pipe ) then become a homemade version of the modern chamber system. Read up a little on what size tank, you would need and how many feet of chamber system piping , you would need and you should be able, to size your homemade chamber system properly. As to the set back distance from your fresh water well, ask a local agriculture office about percolation requirements, for your soil type and have a perk test done, before you begin to establish your perimeters of distance from the well.

I hope some of that helps you !

Best Regards,
Joe Woodall, Rogue Eco-Architect & Managing Partner
Georgia Adobe Rammed Earth & Renewable Energy
Commerce, Georgia 30530 CSA
001-706-363-6453
http://www.georgiaadobe.com

 
Dale Hodgins
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Location: Victoria British Columbia-Canada
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    Having a shut off system is no problem as long as you install an overflow which bypasses the tap just as with bathtub overflow systems. With this simple plumbing in place you will never overflow but will still have the option of spreading most of the material during the drier times. Any material which allows the liquid to flow and drain would be suitable. Here we put gravel around the weeping tile but you could put rice hulls, nut shells or broken pottery.

    Check to see if mango trees are able to absorb the E. coli and transfer it to the fruit. Some herbaceous plants do this and I've heard of contaminated mangoes before. Bamboo roots are one of the most invasive and would clog your system in short order.
 
Dale Hodgins
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Posts: 6795
Location: Victoria British Columbia-Canada
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      Because of your high water table any weeping system should be in the first 50 cm of soil. Definitely don't put anything 4 feet feet deep since this would mean injecting directly into your water supply.
 
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