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Saturday, November 21, 2009

When the SHTF - you will have to too...sewage treatment

In interesting times, depending on your sophistication level, you will have (probably) one of the three type of treatment systems. The privy or outhouse, a cesspool , or a septic system with leach field. In a shelter situation you will also need the basic bucket behind the screen which I will also cover.

The overriding reason for treating sewage is to prevent disease and contamination of ground water and food stuffs. Fecal matter is full of bacteria, some of them quite toxic. Two of the hardiest are the many serotypes of Salmonella and Aeruginosa. They can survive over 5 months in topsoil when directly applied to it. Composting at 140 to 160 degrees Fahrenheit can kill them.

Without going too deeply into the biological action of sewage decomposition, there are three useful types of bacteria and 4 enzymes needed to break the stuff down. Anaerobic, aerobic and facultative bacteria break down sewage. They are aided by enzymes which work on breaking down starches and carbohydrates (Amlyase), cellulose or paper (Cellulase), fats ( Lipase) and proteins (Protease). All commercial systems use these basic components to turn sewage into sludge. Sludge if processed properly is an excellent fertilizer.

The Rules

One final thought about this prior to going into the systems. Whatever you put into the system will most likely be there for you to take out of it. SO, minimize what you flush. No garbage grinding using the disposal, wipe with the minimum amount of paper. No harsh chemicals to kill the bacteria when using wet systems, AKA the septic system or cesspool. No fats which can be skimmed. No oils that are solid at room temperatures. In other words, nothing you would not want to have to muck out later because it didn't breakdown to humus.

The Systems

In a shelter situation, the simplest form of toilet would probably be the 5 gallon (20 litre) bucket with a plastic bag liner. After so many uses the bag's treated with enzyme, sealed and stored until the occupants can leave the shelter. There are many companies who sell the lids for these camp toilets and they are well known to many who use the out doors. Plan to have supplies sufficient for 3 weeks of use. The list is 3 liners with seals, 3 packets of treatment media and 1 roll of toilet paper per person per week. A family of 4 will generate about 2 cubic foot of sewage bags per week.

A pit privy or out house should be an enclosed structure sited away from the retreat/homestead and 150 feet from the water well should you have a shallow one. It should be well drained and vented to facilitate the decomposition of the material. Using a cyclone vent above the structure and the application of lime to the pit can reduce smells. The pit should be used for a period of 6 months then filled and allowed to rest for a year. Over the long haul a small group (about a dozen people) would be able to rotate between 3 pits without too much hardship. Do not dig the pit deeper than 2 foot above the local water table.

One variation of this system originated in Scandinavia. It has proven quite useable and is called the two can system. A 5 gallon can is filled to the depth of 2 inches with fine wood chips or saw dust. Then the can is used as a toilet. Alternate layers of waste and wood chips/ saw dust are placed in the can until it’s full. Then the can and contents are placed in a “ bread box”. The bread box is a miniature green house with south facing glazing and the north interior wall painted black. The sides can be insulated for greater heat gain in northern climates. The angle of the glass for the roof should be the latitude plus 15 degrees. The can is placed inside it and a small amount water is added to aid in the decomposition of the mixture. The rotting material will heat itself along with the solar gain of the box and sterilize the contents of the can. Sustained temperatures of in excess of 140 degrees Fahrenheit will kill the bad bacteria and produce fertilizer. This process will take around 7 weeks to complete. When it’s done you take the product, dump it into the compost pile for later use and scrape out the can. The container can then be rinsed and reused. Depending on the number of users there may be more than 2 cans involved obviously.

Cesspools come next. They are basically a porous covered underground vault. The vault is vented to allow for the combustible gases to dissipate without danger to the users. Indoor plumbing drains into the vault. The liquids drain out and the solids stay. And depending on how fastidious you are at maintaining crapper discipline, you only have to deal with it once the vault is full. If you generate lots of greasy waste or lots of hard to decompose fibrous material you will have to deal with it sooner than some one who keeps the system clean. Usually what happens to this system is the porous tiles become impregnated with grease or ossified material and stop draining. The vault overflows and the users scratch their heads and call the septic pumper. In interesting times this would not be an option. Therefore users should refer to the rules above.

Septic tanks and leach fields are common fixtures in rural areas. They are basically a vault which in this case is impermeable that has the sewage fall into it. There are baffles to cause solids to fall out. Then the liquid effluent is piped by gravity to a network of permeable pipes which drain it into the soil. Sizing of these systems is straight forward and controlled by the local building code. Depending on how well the soil drains, the sizing of the leach field follows. Slow draining soil means large leach fields. Fast draining soil means small leach fields. Since these require a substantial outlay in money and time to complete, they should be in place at the site well in advance of occupying the retreat/homestead. Also, sizing of the tank and field is required to handle the population of users. This is necessary to prevent overloading the system and causing failure of the biological processes required to decompose the sewage. Most people think a septic tank if properly maintained will not require pumping. This is a rare bird indeed. In the real world, most septic systems are working very well if they can break down 2/3’s of the sewage solids placed in them. As a general rule they require pumping about once every 5 years.

To increase the longevity of your system, you should put in place the following aids to allow you to maintain your setup. Have all cleanouts and manholes or access points clearly marked. Maintain a good “as built” schematic of where the stuff is. Install a grease pit and a trash screen. The grease pit will collect the fats and stuff which was liquid at room temperature but gelled when it hit the cold underground piping. The trash screen will filter out “chunks”. These are things like the prim 5 year old who managed to get a half roll of toilet paper to flush and it didn’t plug the outfall line. That Tango Papa (TP) isn’t going to rot in your lifetime, so why put it in your system? Have on hand the enzyme and bacteria starters needed to keep your system active. And when in doubt, READ THE RULES above.

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