Lawrence Sustainability Network--Lawrence, KS


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Workshop Notes: Greywater Systems, Harvesting Rainwater and Composting Toilets
Midwest Alternative Energy Fair, June, 2006 by Natalya Lowther

I attended these workshops because I’ve lived in many different situations over my life where I’ve had “non-standard” water/waste systems, and am interested in how others have incorporated such systems into their daily lives. Our current urban cultural norms in these areas are pretty wasteful of resources. I’m grateful to own a home where I have my own well and septic system, but even these systems often seem inefficient. And not everyone lives 20 feet above a river: As basic human needs, water and sanitation are huge global health, peace, and justice issues.

Bob Dahse and Larisa Walk are enthusiastic about their 20 years’ experience with recycling rainwater in their home, for gardening, household, and drinking purposes. Recycling rainwater has many benefits: It can reduce water bills, or supplement or replace a well with limited capacity or poor quality water. It helps manage stormwater problems from roof run-off. It provides soft water without an expensive water softener that replaces calcium and other minerals with still-unhealthy salt.

David Abazs invented his own greywater system 18 years ago; more information is available at “Greywater,” for those unfamiliar with the term, refers to household waste water that isn’t from the toilet–in other words, from the sink, shower, and washing machine. It usually contains dirt and soap, obviously, but also other contaminants like metals from pipes and traces of fecal material from the washing machine. Still, it doesn’t require the intense treatment that “black water” from the toilet does.

Composting “human manure” means treating the waste through the action of low-odor aerobic (air-loving) bacteria, rather smelly anaerobic bacteria that work in liquid treatment systems like traditional outhouses, septic tanks, and commercial sewage treatment systems.

These three systems can be most effective when used in an integrated system. However, legal issues can be a challenge for all of them, as well. Though rainwater has been collected, waste water has been reused, and human waste has been processed without liquid sewage treatment systems probably for as long as there have been humans, in many cases these processes have been carried out without careful regard and scientific understanding of the possible consequences. Poorly done, all of these activities can pose real health hazards. But it doesn’t necessarily follow that they should never be done, although that’s the approach that many building codes and zoning regulations take. There are two aspects to designing and implementing any of these systems: One, designing a system that will function well and safely in a particular situation (do-able); two, designing a system that will comply with local laws (challenging to next-to-impossible). In most cases, it will take a lot of careful research and educational work with local officials to implement a system that is legal while achieving the goals of conserving resources–both monetary and natural.

Greywater systems: Approximately 40% of household water use in conventional systems is for toilets. The remaining 60% can be run through a greywater system, significantly reducing the demand on a septic tank. This can prolong the life of the blackwater septic system and lateral field. The system that was presented disperses the greywater underground where it is used to water crops such as fruit trees (no root crops that would have direct contact with the greywater!) rather than recyling it for household use such as flushing toilets. Reusing greywater is more challenging because it involves possible human contact with the water, therefore it must be treated more aggressively due to possible fecal contamination. To avoid human contact, greywater should be released underground only.

A filter on the washing machine is important to prevent clogging of greywater system pipes from lint.

A small (300 gallon) septic tank is necessary to meet codes in most areas. The small size helps keep the greywater from becoming anaerobic which would result in unpleasant odors. This holding tank allows solids to settle out, and fats to rise. Then water is run through a filter tank of clean gravel before being pumped to the underground distribution pipes. The pressurized system is essential to distribute the water evenly through the pipes, resulting in even watering of the crops. For the underground tanks, plastic is best because it doesn’t leak. Be sure to fill tanks with water immediately upon placing them in the ground, or they may float out!

Two-layer underground pipes are the unique part of this design. Plastic irrigation tubing with 1/8" holes is run through perforated plastic drain pipe, and the whole thing is buried–6-12" deep for winter use in northern Minnesota, 1" deep for summer use. The shallow depth can be used year round if insulated with hay on the ground above the pipe. The air space between the inner pipe and drain pipe helps to insulate the system. Also, the air space prevents roots from growing into and clogging the inner pipe. If the inner pipes ever do need replaced due to clogging, new inner pipes can be fished through the outer pipes easily. The length of the system and the hole spacing depends on the soil type: for a low use household in sandy loam soil, a 50' system with 10" hole spacing works. Less permeable soil would require longer pipes and wider hole spacing.

Removing the greywater from the regular septic system has no adverse effect on the septic. The life expectancy of the septic system is based on accumulated solids and bonding of heavy metals.

Bleach should be avoided in drains, as it harms bacteria. Also, use biodegradable cleaning products, and avoid “antibacterial” dish detergents.

Harvesting Rainwater: Rain water isn’t necessarily 100% pure and clean! The drops form around dust particles, which may be from industrial sources. For drinking water, don’t collect rain during the summer (Kansas old-timer lore says “Only collect rainwater during months that have a “r” in them”–September through April). Underground storage is best to deal with freezing weather. Don’t use plastic for storing potable water. Concrete is ok but won’t yield completely soft water, and may tend to leak (even if not when tested at the factory, then probably after being bounced down the road on the truck!)

Non-potable water (i.e., for irrigation) can be harvested any time. Above-ground tanks can be used for storage, and drained (ideally into a pond) before freezing becomes a problem.

Bob and Larisa use an underground 2250 gallon insulated stainless milk truck tank to store water for their household of 2 people. A pump and pressure tank distribute the water through conventional household plumbing. The system includes an aboveground 250 gal. settling/collection tank that is drained in the winter. The manhole of the underground tank, and the ground above it, are insulated to help prevent freezing. A carbon filter at the tap finishes off the water for drinking. A 1500 plastic agricultural tank collects non-potable water from a shed roof for irrigation. A 300 gal. stainless milk bulk tank holds water for livestock and vegetable washing.

Nothing will grow in a stainless tank. With concrete, it may be best to have two tanks so one can be cleaned while the other is in use. Aboveground plastic tanks may be painted to block out light and help prevent scum from growing.

Minimizing water use is an important part of living with a rainwater system, and is a place where anyone who is paying for city water or for electricity to pump water could benefit from starting to change their lifestyle long before actually installing a household rainwater system. Some specific ideas include:

Use a high efficiency front loading washing machine (which also uses less soap which means less rinsing and cleaner greywater).
Install a composting toilet system (as we learned in the greywater workshop, the toilet accounts for 40% of household water use).
When showering, catch the cool standing water from the hot water pipe in a bucket, and use to water plants.
Use cooking drain water (pasta, veggies) to water livestock.

The collection system starts with the roof. Asphalt or wood shingles are worst; galvanized is good, or standing seam steel roof. For one thing, birds don’t tend to hang out as much on shiny roofs. For non-potable water, any roof will work. If your house roof isn’t good for collecting potable water, you may have a shed, garage or barn roof that is better. The first 10-15 minutes of a rain should be allowed to just run off, to clean the roof, before routing water to the collection tank. Keeping gutters clean is important, too.

To collect the water, they’ve installed two “tail pieces” from kitchen sink drains in holes in the gutter. One is plumbed to the collection and settling tank with food-grade polyethylene pipe, with a stainless steel screen. The other is for running off the first water to clean the roof. After the first 10-15 minutes of rain, someone runs out and switches the plug from one to the other (the gutter is reachable from the ground). (Some old Kansas houses and barns have built-in switches on the downspouts to route water to old stone or concrete cisterns or to the open ground; some include sand filtration systems.)

An automatic system for switching could be devised but they haven’t felt the need to since someone is usually home. Also, they check water level in the tank just by opening it and looking...a dipstick system could be devised.

Using a limited amount of water in this way reduces the size of septic system needed, and thereby the cost of installing a septic system. In Wisconsin, there is an exception for septic sizing requirements that is based on metered water use.

Using greywater for appropriate irrigation needs complements a rainwater system by getting the most use out of the water collected.

Water can be tested at various points in the process to better understand what you’re getting: as it is coming off the roof, from the tank, etc. Www.doctorsdata.com has information.

Composting toilets: As you can see from the above, composting human excretia fits nicely into greywater and rainwater systems by minimizing fresh water demand and waste water output. “The bible” of composting is the classic Humanure Book. There are many commercial systems available, which are easiest to get approval for in permanent installations.

The general concept of humanure composting is to use living organisms–primarily aerobic bacteria–to break down the waste and any harmful organisms it may contain. Some bacteria do this at very low temperatures, but the most effective humanure systems focus on mesophyllic (60-113 degrees F; “mouldering” systems) and thermophillic (113-nearly boiling) bacteria. While many commercial systems are “mouldering” systems, DIY systems may go for the thermophyllic.

A bare-bones system (good for emergency situations, but not exactly legal) would be a 5-gal. bucket under a commode. Start with a layer of carbonaceous material (sawdust, straw, hay, dry leaves, or shredded newspaper); add more carbon stuff after each use. Have a couple buckets ready to go at all times so you don’t have to trot out to the compost pile in the rain or the middle of the night when it suddenly fills up! Empty the bucket onto a designated “humanure” compost pile. Such a pile can also be used for “non-compostable” meat, bones, milk products, etc. that would be banned from an ordinary garden compost pile.

In constructing such a pile, think of building a TOMBstone over the waste:

T--Temperature is crucial–as hot as possible. Minimum size is 4' x 4' x 4'–can be built with packing pallets. Start with 8-12 inches of carbonaceous material–leaves, etc. Thermophillic activity may slow down or stop in winter.
O--Oxygen is necessary to keep the pile aerobic and therefore not stinky. Anaerobic bacteria release methane. The stack on a commercial composting toilet helps keep air moving through the pile. Slatted sides on the pile, and not letting it get too wet and soggy, help keep it aerobic. In a conventional compost pile, turning the pile incorporates air/oxygen, but this would present opportunity for human contact with the waste, so isn’t normally done in humanure composting. Instead, just letting the finished pile sit for a long time (1 year or more) assures complete decomposition.
M--Moisture is hard to measure in a humanure pile, since you don’t want to stick your hand in it. 50-60% is best. Too dry is better than too wet; this is one reason urine is often diverted from humanure compost piles. If the pile is too wet, cover it with carbonaceous material.
B--Balance of carbon to nitrogen is crucial. 28 parts C to 1 part N by weight. Manure is rich in N, so a lot of carbonaceous stuff is needed. If in doubt, add more C–you can’t have too much. Too much N makes a gooey, gross, stinky pile.

A Coast Guard approved porta-potty or cassette-style RV system can be drained weekly onto a humanure compost pile. RV systems with pumps and hoses can be set up to drained directly onto the pile, eliminating all handling. If using a camper system, don’t use the formaldehyde-based fluid; the biodegradable kind is ok. 2 oz. isopropyl alcohol can be used instead.

The cost of commercial systems actually is not that great when all factors are considered, and they can really extend the life of a septic system that is then used only for greywater. Be sure to follow the instructions on a commercial system–failure to do so is commonest cause of complaints. The fan on a commercial system doesn’t really draw very much current. A wind turbine on the stack can really increase the draw through the toilet. Composting systems almost always smell better than conventional water-based systems. If it’s installed in a living space, a heater is generally not needed except to evaporate extra liquid. This can be balanced with more sawdust. Incinerating systems are generally a waste of fuel.

Toilet paper composts well–esp. recycled. Newspaper does too, but avoid colored. Paper and cardboard also compost.

My personal reflections: In all three workshops, a common thread undermining the general acceptance of such systems, and especially the regulatory hurdles to be faced in installing them, is what one presenter labeled “fecalphobia”. Fecal contamination is certainly a valid health concern. We don’t want it in our drinking water or food. But it seems that we unduly let “fecalphobia” drive our lives in some ways, while putting our heads in the sand in other ways.

We can go to the grocery store and buy toxic pesticides that require the use of protective gloves, goggles and other equipment, refraining from smoking or eating during use, careful cleanup and disposal of equipment, etc. Apparently we are trusted to use these products responsibly. These same precautions applied to fecal material would be adequate to preserve health while doing maintenance tasks on even a very rudimentary humanure compost system. However, in most areas strict regulations strive to prevent us from ever encountering fecal material by choice...except when we are producing it. But when the toilet backs up and overflows (not likely with a composting toilet), someone has to clean it up...and may not have protective gear on hand! It’s ok for a professional septic tank cleaner or plumber to manage your waste (for a steep fee, of course), but apparently us untrained non-professionals can’t be trusted to manage our own waste.

Organic growing standards require that animal fecal material not be applied to a crop within 90 to 120 days of harvest. However, there are no standards preventing birds from sitting on the tomato cages, or mice from burrowing into a hill of potatoes!

In a country where virtually all water that comes out of a tap is as safe to drink as much of what we eat, many of us spend money (and waste other resources such as the packaging, storage and transportation required) to purchase bottled “drinking water” which may in fact just be tap water from somewhere else. We worry about the chemicals in the tap water but not the ones in the plastic bottles.

Each of us privately examining our attitudes towards such things, and the inconsistencies that we live out everyday, can be a good starting place for conserving precious resources. Not everyone will want to, or needs to, make these particular lifestyle choices. But we should at least examine our habits and question our assumptions now and then, based on the “big picture” rather than on the latest scary news report.

We might also begin to question some of our regulations and building codes. Do they allow resource-conserving choices and personal responsibility for home-owners? Or do they primarily support builders and product manufacturers by setting “standards” that are far in excess of what is needed to protect human health? Are they based on standards to be met (i.e., “keep fecal bacteria out of drinking water”) or specifications (i.e., “50' between well and septic tank” which might be more or less than needed depending on local conditions)? Is it really a free country when you can’t install your own plumbing in your own home? I saw a statistic once that “80% of the world’s population lives in sub-standard housing.” That seems to indicate that our “standard” is actually way above average in a global perspective...and there simply aren’t enough resources for the whole world to live according to our standards.

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