Technical Bulletin No. 6
Text and graphics by Tad Montgomery
Copyright 1987 by The New Alchemy Institute. All rights reserved. Printed in the United States of America. Except for brief quotations used in critical articles or reviews, no part of this publication may be reproduced or transmitted in any form by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the copyright owner. For information, write to The Green Center, 28 Common Way, Hatchville, MA 02536 USA.
Revised and reprinted January 1990.
ISSN 0898-7580
ISBN 0-933822-17-0
The Standard Septic System
Description
Maintenance
Cost
Pollution
Codes
Advantages and disadvantages
Some Alternatives
Alternating leach fields
Evapotranspiration beds and mound systems
Aerobic treatment units
RUCK denitrification system
Peat beds
Alum Precipitation
Constructed wetlands and ecosystems
Composting Toilets
Introduction
System designs
Codes for composting toilets
Products and designs
Annotated Bibliography and Resource List
Despite spending billions of dollars on high-tech treatment facilities and imposing countless regulations on homeowners, our society still does not deal with its wastes in a manner compatible with the environment. The results of our present wastewater treatment practices can be seen in eutrophic ponds choked with algae and plant growth, streams and rivers where most of the fish and amphibians are diseased or gone, and groundwater that is too polluted to drink.
Fortunately, we are becoming aware of our destructive patterns. With this awareness comes a responsibility to design new ways of living. This does not, however, imply a need to spend more money for greater wastewater purification levels. The standard solution has been to built complex, expensive municipal treatment plants which merely shuffle the problem from one arena to the next; from the pollution of groundwater and local surface water by septic systems to the pollution of rivers, lakes, oceans and landfills by municipal treatment plant effluent and sludge. With the elimination of federal funding for wastewater treatment, this solution has become obsolete.
As the comparison of systems in this Technical Bulletin demonstrates, economics need not be in conflict with the environment. Ecological wastewater treatment systems are often less expensive than their conventional counterparts and in some circumstances can be built for as little as one percent of the cost of the standard, code-approved systems.
What is needed is not more money but rather a firm commitment to educate ourselves and our government officials about the issues which lie behind our present technologies. We must also commit ourselves to developing new technologies which address these issues. This manual is not meant so much as a design manual as an informative guide for those individuals who have made that commitment to live in a manner compatible with the land around them.
Perhaps the largest obstacle to the implementation of environmentally sound wastewater treatment and disposal is the public's perception of sewage. That is, most Americans would simply rather not have to think about the consequences of their wastes. This problem is exacerbated by codes which were developed to favor certain systems long before their environmental impacts were understood.
A small number of towns and rural municipalities have started to look at the deleterious effects of standard septic systems and are developing alternative code structures to allow for non-standard waste treatment methods. Two notable examples are Humboldt County, California which has in place an alternative wastewater treatment program for homes, and Wendell, Massachusetts, which has approved a standard composting toilet system for residents.
What is needed is not more money to sewer up the countryside, but firm commitments to educate ourselves and our government officials about the issues which lie behind our present technologies. Change will come bit by bit as we adapt our thinking and lifestyles to the environment around us. This Technical Bulletin is written as an introductory guide for those individuals who have made a commitment to living gently on the land.
Description
Unless their septic system fails and needs repair, most homeowners never learn the processes involved in on-site wastewater treatment. A septic tank soil absorption system consists of a septic tank, which performs primary treatment, and a subsoil leach field to dispose of the effluent.
The septic tank, buried out in the back yard somewhere, is designed to separate solids from the liquid portion of the wastewater. In doing so, it provides limited breakdown of organic matter, stores solids not broken down and separates grease and scum from the waste stream (Figure 1). It's a filthy task. The solids that settle to the bottom of the tank are called sludge and must be periodically pumped out. Oils and grease that enter the system float to the top of the tank and form a scum layer.
Anaerobic (oxygen deprived) bacteria digest organic matter in the septic tank, converting suspended solids to soluble organic acids and carbon dioxide. This digestive process is called "septic," ergo the name.
Figure 1. Cross Section of a Septic Tank
After leaving the septic tank, the effluent enters a subsurface disposal system, the most common type being a leach field. This is made up of an underground distribution box, through which the effluent flows into the soil via a series of perforated pipes laid in gravel trenches roughly three feet below ground level (Figure 2).
Conditions surrounding the trench are predominantly aerobic and the effluent undergoes filtration and decomposition before soaking down to the water table. Although the soil removes organic matter and some nutrients from the effluent, a significant amount flows down to the ground water and may eventually appear in the nearest body of surface water, leading to eutrophication, decay and the loss of species in that water body.
Adaptations to this standard system manipulate the processes in the septic tank and the disposal method. One common addition which many codes require is a dual-chambered septic tank. This feature promotes a greater degree of treatment in the tank but jacks the price up as well.
Figure 2. Typical Trench System
A number of simple measures can, when conscientiously performed, considerably extend the life of a septic system. The single most important is the regular pumping of sludge from the septic tank. When pumping is not performed at least once every four years, sludge builds up to the point where it prevents adequate treatment of the effluent or overflows into the leach field, causing major and often irreparable clogging. The latter can be compared to a serious case of constipation but is much more difficult to correct. The first sign of such problems is poor drainage from the house.
Water conservation can also play a key role in septic system longevity. When the volume of water flowing through the tank is reduced, organic material within the system is retained longer, which gives the anaerobic bacteria within the tank more time to decompose the solids. Reducing water from toilet flushing has the effect of increasing microbial activity and the septic tank's effectiveness. This is the result of the raised temperature in the septic tank, since most gray water is heated and water used to flush toilets is not.
When incomplete decomposition takes place, solids wash through to the leach field where they cause soil clogging and system failure. A related issue concerns water entering the septic system from other sources. Rainwater runoff from the roof and from the storm drains surrounding the foundation can be major sources of system overload.
Homeowners should also be conscious of what goes into their septic system. Organic material from garbage disposals is commonly dumped into septic systems which cannot handle the extra load. Compost those food scraps, or set up a worm bin for them! Grease and paper products should not be flushed into the system either, as they can build up in the tank and clog the inlet.
Avoid using septic tank cleaners; they unclog the leach field by completely destroying the beneficial bateria in the trench. They also consist of powerful solvents (such as tricholorethylene) that are highly toxic and can leach into the groundwater. Commercial enzymes also can do more harm than good. The best procedure for a clogged leach field is to reduce water useage and waste input, or let the system rest.
Lastly, a log should be maintained with a sketch of the location of the septic system as well as dates of inspection and pumping of the septic tank. This helps maintenance people to locate the access hole and the homeowner to know when to pump.
The cost of a standard septic tank/leach field waste treatment system is highly variable. On Cape Cod, Massachusetts, in sandy, homogeneous soils, one finds the low end of the scale at roughly $3,500. The other end of the scale can be found as close as Worcester, Massachusetts, where inappropriate site conditions can force a system's cost up to $20,000 to $30,000. The cost breakdown of a system for a three-bedroom house on Cape Cod looks something like this:
Other costs which should be taken into account include soil tests, site analysis, and engineering fees, all of which are often required. The low end of fees for these services, on Cape Cod, is $700. This can easily triple for difficult sites. Finally, the cost of buying the water to flush with should not be underestimated. It may not be long before our water bills rival our electricity and gas bills in magnitude, as is happening in some towns already.
There are a number of ways in which septic systems pollute. To start with, they are notorious for failure. When a system fails, effluent from the tank backs up and spills out onto the area surrounding it. Any pathogens present become an immediate health hazard and pollutants in the system may make their way to nearby surface water.
Even when operating properly, septic systems are not very effective with certain pollutants. For example, nitrogen and phosphorus are excreted in large quantities by humans and go directly into their septic systems. The subsurface soil environment performs some nutrient removal under optimal conditions, but most leaches directly into the groundwater. This is especially true of nitrogen, almost all of which is converted to the nitrate form (NO3) upon leaving the septic system (Hall 1975). This phenomenon proceeds most quickly in sandy soils.
Other pollutants also enter the environment through the septic system. Many people are remarkably unconcerned with what they wash down their sinks and toilets and oblivious to the fact that these substances are leaching directly into the groundwater below their homes. There are a good number of toxins in everyday cleaning agents and other household commodities, such as paints and solvents, which people have no compunction about pouring down the drain. These pollutants become especially problematic when the density of septic systems in any given area is too great. It has been estimated that areas with more than 40 septic systems per square mile can be considered to have potential contamination problems (Canter & Knox 1986). Groundwater degradation has occurred in many areas having high densities of septic systems, with the degradation exemplified by high concentrations of nitrates, bacteria, and contaminants and eutrophication of surface water. Research has indicated that significant amounts of toxic organic contaminants have been introduced into the groundwater through septic tank systems, a major cause being the use of solvents to clean clogged leach fields. These problems are magnified by the fact that in many rural communities the use of subsurface disposal systems is paralleled by a reliance on private wells for drinking water supplies.
Another major pollutant is the inadequate disposal of the sludge that is pumped from septic systems. While there are ecologically sound ways of handling it, such as municipal composting and application to farmland as fertilizer, most often the sludge is simply dumped in landfills or septage lagoons, where it leaches down into the groundwater.
Jurisdiction over on-site waste disposal systems is determined at the state level where general standards are usually written. In Massachusetts, for example, the Department of Environmental Protection has set minimum guidelines for design and construction of septic systems. Outlined in Title 5 of the State Environmental Code, specifications include size of the septic tank, minimum distances to structures, wells, surface water and groundwater, required design features and minimum percolation rates of effluent into the soil.
Local and county health agencies usually have ultimate authority in authorizing waste disposal systems. They seldom relax the state standards because these standards are often the only mechanism in place to limit or control development. These specifications are quite thorough in their coverage but were written before the inherent pollution from septic systems was fully understood.
Advantages of the standard septic system include the following:
The disadvantages of septic systems include the following:
Many soils in the U.S. are not suitable for the standard septic leach field. Examples include clay soils, soils with a percolation rate of more than 60 minutes per inch, thin soils over bedrock with crevices, and soils with groundwater near the surface. The standard septic system can be improved in a number of ways to make it workable in such con-ditions, extend its life or reduce its environmental impact. Some of these technologies are well-tested and code-approved in certain areas; others are neither. They cost considerably more than a standard system because they require additional components and need to be custom designed by an engineer. Health officials should be consulted to determine relevant codes in your area.
This technique extends the lifetime of the effluent disposal bed by having two leach fields which are alternated on a yearly basis. This allows the one not being used to rejuvenate itself. This technique is being adopted by health agencies in many areas. The cost of the system is increased by the price of an additional leach field, but using this technique almost guarantees that the system won't fail and need to be replaced at some later date.
The mound system is used often in New England to overcome poor soils conditions. It employs a pump with a built-up leach field or mound which comprises a fill material (usually sand), an absorption area, a distribution system, a cap, and topsoil. The pump in the pumping chamber elevates the effluent from the tank and pressurizes the distribution within the mound. A passive siphon may replace the pump if the mound is located down slope of the pumping chamber. The effluent flows through the fill material, where it is partially purified, before entering the natural soil. The cap, which is usually topsoil or subsoil, provides frost protection, serves as a barrier to infiltration, retains moisture for vegetation, and provides for runoff of precipitation.
Often proposed in applications where septic tank leach fields are unsuitable, aerobic digesters discharge partially treated, disinfected effluent onto the ground, into surface waters or into shallow, rock-filled trenches. They act more as a conscience appeaser than a bona-fide treatment mechanism. Many types are on the market today. The typical unit (Figure 3), consists of chambers for pre-settling, aeration and final settling and functions like a small, extended aeration, activated sludge treatment plant. Air is pumped into the second chamber in order to create an environment conducive to aerobic bacterial digestion. The final settling chamber allows for collection and return of biologically active sludge to the aeration chamber and discharges the clarified effluent for disinfection and disposal. Some units do not have pre-settling chambers. Prefabricated fiberglass installations are common, but when units are constructed in place, the building material is usually concrete. Cheaper versions can be placed directly into an existing septic tank (for more information contact Biorobi Inc., c/o Charles Travers, P.O. Box 133, Hamlin, PA 18427).
Aerobic treatment units do create a higher quality effluent than septic tanks, but are not recommended for discharge onto the ground or into surface water, due to the effluent's high concentration of nutrients and potential for the spread of viruses, which are not affected by standard wastewater disinfection techniques. They have generally had a bad reputation for two major reasons (Bennett et al. 1975). The first is neglect by the homeowner; many people will not accept responsibility for maintaining their wastewater system, and therefore a successful unit must be highly reliable, require minimal maintenance, or include a service contract. The other factor is the adverse effects of surge flows, such as those produced by numerous laundry loads or blowout beer parties. These design shortcomings are exacerbated during wintertime operation when biological activity slows considerably.
This system, designed by Dr. Rein Laak (Department of Civil Engineering, University of Connecticut, Storrs, CT 06268) eliminates the greater portion of nitrogen and some phosphorous from the waste stream.
Gray water and blackwater from the house are diverted in to separate streams. Effluent from the blackwater septic tank passes through an In-Drain sand filter which nitrifies the nitrogen to the nitrate (NO3-) form; this is an aerobic environment which must be ventilated (Dr. Laak recommends pipes running along the house's gutter downspouts). The effluent from the In-Drain then flows in to the gray water septic tank. This is an anaerobic environment where denitrification takes place, converting the NO3- to N2 gas, which bubbles off. The effluent from this is then passed through a standard leach field.
The cost of a RUCK system is between $8,000 and $10,000; and roughly one hundred are now in place. The system is still somewhat experimental but is being considered for code approval or is approved in a number of states in the Northeast. There are other denitrification systems available, such as recirculating sand filters, but they require pumps and external energy, unlike the RUCK system which is passive. The effectiveness of denitrification systems has not yet been fully determined, and proper construction is very important for system effectiveness.
Nitrogen and phosphorus can be removed from a waste stream through the use of a peat bed incorporated into a septic system. Effluent from the septic tank is passed through two layers of peat separated by a layer of sand. The top peat layer removes phosphorus and converts nitrogen to nitrate. The effluent then passes through the sand layer and into another peat layer which is submerged to create anaerobic conditions. Here the nitrate is denitrified to nitrogen gas, which bubbles off. This system has not received much acceptance in the wastewater community for on-site applications chiefly because of its high maintenance requirements.
This system has been designed to remove phosphates from the waste stream of a household. It differs from a standard septic system only by the addition of alum (Al2O3) injection units which are installed at each toilet. The alum retains the phosphates in the septic tank through a chemical reaction. The increased solids generated by the alum addition require that the septic tank be pumped more frequently. An additional factor with this system is the added pollution brought on by the use of aluminum oxide, which is eventually landfilled when the septic tank is pumped.
At the home-scale, effluent leaving a septic system can be passed through a constructed wetland, utilizing outdoor and greenhouse-enclosed aquatic ecosystems to treat wastes. The various plants take up nutrients, and remaining effluent is disposed of via a leach field. This system requires that the plants in the marsh be harvested periodically. Two companies designing on-site constructed wetlands for wastewater treatment are Solar Design Inc. in Stockton, New Jersey and Native Harvest Design in Jaffrey, New Hampshire.
For larger applications, another two companies in New England offer designs for small municipal-scale wastewater purification using constructed ecosystems. John Todd has founded Ecological Engineering (Falmouth, Massachusetts), a company which builds complex ecosystems housed in bioshelters to treat wastewater. Biological Water Purification of New England, located in Blue Hill, Maine, uses certain species of marsh plants in outdoor beds for the same purpose. Dr. Todd has also developed a similar biological purification system for the treatment of septage.
Wastewater purification utilizing constructed ecosystems has great potential as a safe, effective and environmentally benign means of treating wastewater but has not received significant attention or support from traditional health officials or regulatory agencies. Further research and pilot projects are needed before these types of systems will be accepted as bona-fide, certified technologies for treating our wastes.
Composting is the aerobic, biological decomposition of the organic constituents of wastes under controlled conditions. Some heat is liberated during the process, causing the compost to warm. In composting, nitrogen is used by microorganisms for metabolism and cell growth while carbon supplies an energy source. The rate of composting is dependent upon a number of factors, but those of major import are moisture content, carbon-to-nitrogen ratio, aeration, temperature and microbial population.
Segregating human wastes from gray water has a number of advantages. The elimination of toilet flushing simplifies household wastewater purification since toilet wastes contain most of the pollutants and the vast majority of pathogens in wastewater. Along with its pollution control qualities, a compost toilet reduces water consumption by about 40%, permitting both a savings of water and a reduction in size of the wastewater purification system. In areas where the costs of conventional wastewater treatment systems are escalating, the use of composting toilets with gray water treatment systems can be an economical alternative. Composting toilets also have the attraction of converting a societal nuisance into a resource - fertilizer.
There are three basic types of composting toilets: large units, small units and owner-built models. Large units generally consist of prefabricated bins in which composting takes place. These bins are usually located in a room below the bathroom. The smaller units fit inside a bathroom and are characterized by a heating element that evaporates excess fluids. Owner-built models are variations on the larger type.
Advantages of the larger models include minimal energy use (though some now incorporate heating elements within them), minimal maintenance requirements, and their ability to absorb shock loading (such as at a party). Advantages of the smaller units include their minimal space requirements and lower cost.
Disadvantages of the larger units are fluid build-up, lack of proper aeration or mixing mechanisms, excessive ventilation requirements (which can lead to a significant heat loss in cold climates in the winter), fly and pest control, and space requirements that often render retrofitting difficult or impossible. Liquid overflow drains have been added to many systems in recent years, attesting to fluid build-up as a problem. Large gatherings often cause excess liquid accumulation. Options for disposal of the fluid include dilution and use as a fertilization agent (care should be taken concerning pathogens), diversion for treatment with the gray water (not recommended from an ecological standpoint) and addition to compost piles as a nitrogen source. Owners have reported that the fluid can be odorless or, if it does smell, loses its odor quickly when applied to a compost pile. Addition of liquid absorbing materials such as peat or sawdust to a composting toilet can reduce the excess fluid to some extent. Care should be taken when handling fluid that has been in contact with fecal material since it may contain pathogens. For all practical purposes, human urine that has not been contaminated with fecal material can be considered sterile, since only pathogens from urinary-tract diseases would be present and they can only be transmitted by introduction to another urinary tract, which would require a bit of effort.
Many manufacturers of composting toilets either design their systems to incorporate a fan for ventilation or recommend that one be installed in conjunction with the system. This helps to ensure positive draft up the vent, removes odors from the bathroom and increases liquid evaporation. Its main drawback is the amount of heat lost through the large volume of air leaving the house. In owner-built models a solar chimney can be used effectively to provide adequate ventilation.
Solar-assisted composting toilets are also being developed as adaptations on the large and small styles. The solar component in the smaller units would be an attached solar collector panel which would blow heated air through the toilet, evaporating excess liquid and displacing much of the required heating load. The larger units are designed entirely around the process of solar heating and evaporation. The patent on solar-assisted composting (U.S. Pat. 4,174,371) is held by Ecos Water Conservation Systems, who are more than willing to assist individuals and corporations in the merging of these two noble processes. For their address see the products section of this bulletin.
The humus which is removed from a compost toilet can be used as a fertilizing soil amendment, recomposted or buried. If used as fertilizer, care should be taken that the compost is free of pathogens first. This can be accomplished by heating it to pastuerization temperatures (150°F) for at least one hour, or allowing the material to compost for a period of at least one year. It is recommended that the compost not be used on plants that have edible parts which may come in contact with it. From a human health standpoint, ornamental trees and shrubs are the best recipients.
Codes pertaining to the use of composting toilets vary from state to state and from county to county within each state. Often they are frowned upon by health officials who see them as little more than indoor privies. Health officials who have done their homework, however, understand the advantages and drawbacks of compost toilets and have written special allowances into the codes for them. Examples of this include Maine, where the poor soils and rural culture have led the health department to promote composting toilets; Massachusetts, where the Department of Environmental Protection allows for a reduction of up to 40% of the size of the leach field when a composting toilet is designed into the house; North Carolina, where certain systems have been monitored and approved; and Humboldt County, California, where special regulations have been written into the codes which encourage alternatives to conventional systems by promoting and monitoring experimental systems.
Sometimes a person who would like to build a composting toilet into their home meets with resistance from a regulating agency. The best tactic to take in this case is to present information to persuade the agency that an alternative system will not only be reliable but pollute less that a standard system. Be forewarned, this can lead to a long and drawn-out process with no guarantee of success. A central concern of these officials is often that the system will be neglected by the homeowner, fail and create a hazard to neighbors. Another concern is the possibility of the home being sold to compost neophytes who misuse the system or plumb a toilet into the undersized gray water system, overburdening it to the point of failure.
Composting toilet manufacturers and distributors such as Clivus Multrum or Ecos Water Conservation Systems have been known to help in the battle for acceptance, especially if their system is the one that is being fought for.
The National Sanitation Foundation, located in Ann Arbor, Michigan, has gone to great lengths to establish standards relating to devices that affect public health and the environment. Their Standard 41 for Wastewater Recycle/Reuse and Water Conservation Devices includes specifications for composting toilets on structural soundness, insect control, reliability, and indicators of failure. To date, the composting toilets that have received the NSF seal of approval are the Clivus Multrum, Sun Mar and Carousel.
Figure 6. The Gap Mountain Composting Toilet
Gap Mountain Permaculture Mouldering Toilet
Doug Clayton, 11 Old County Road, Jaffrey, NH 03452
(603) 532-7321
This system achieves sanitary treatment of fecal wastes for later horticultural use while conserving potable water. It incorporates two composting chambers, to be used alternately for a period of two or more years each, allowing time for a thorough decomposition and decontamination of materials before they are removed and used as a soil amendment under trees and shrubs. The toilet room and adjacent greenhouse act as passive solar heaters for the air entering the composting chambers; air is drawn from the toilet room to the bottom of the compost chambers by the tall solar chimneys. Air space under the piles helps to maintain aerobic conditions. Odor problems are eliminated by the continual air flow through the toilet room coupled with the predominantly aerobic conditions in the compost.
Insect invasions can be a problem if the system is not properly constructed. Air flow must be regulated (e.g. greatly reduced in the winter) by dampers in the chimneys and air inlets. A pint measure of sawdust mixed with old compost can be added with each use to maintain a good carbon-to-nitrogen ratio for proper composting. Cost above a standard bathroom is approximately $300, not including labor.
Solar Bin Composting
Forest Service Research Note NE-254
Northeastern Forest Exp. Station, 370 Reed Road, Broomall, PA 19008
Cost: approximately $200.
This composter was developed by the National Forest Service after years of research into waterless, powerless sanitation in remote locations. It is inexpensive, environmentally sound and adapts to fluctuating use, but requires some maintenance.
A 24-cubic-foot (6' x 4' x 2') plywood box is constructed above ground and covered with fiberglass for solar heating. A mixture of waste from a nearby privy and a bulking agent are mixed and placed in the composting bin at regular intervals. The mixture is composted for a period of fifteen days with one stirring at day seven. Because solar heat is utilized, temperatures in the bin exceed 60°C (140°F), high enough to kill pathogenic organisms. Ventilated passively, the bin requires periodic filling, emptying and mixing. This system requires solar access and a semi-remote location. The composting box is mobile.
Figure 7. The Long Branch Composting Toilet
The Long Branch Passive Solar Composting Toilet
Long Branch Environmental Education Center
Route 2, Box 132, Leicester, NC 28748
(704) 683-3662
This system was designed by Paul Gallimore, a friend of New Alchemy. It consists of a concrete chamber located below the bathroom with a sloping "air staircase" in it. Organic waste moves down the staircase at a rate that insures aerobic decomposition by the time it reaches the final storage chamber.
The compost pile is aerated in three ways. First, the incoming air stream is preheated by the flat-plate solar hot air collector, eliminating the need for an outside heat source, and moves into the pile through the stairs of the staircase. Second, air is conducted through the PVC pipe ducts that run through the pile. Third, air flows across the pile, evaporating excess moisture. The solar chimney pulls moisture-laden air out of the chamber. This system has been code approved by North Carolina health officials. Design plans are available for $20 from the LBEEC.
Figure 8. The Solviva Composting Toilet
The Solviva Composting Toilet
Anna Edey, Solviva Winter Gardens
Box 582, RFD, Vineyard Haven, MA 02568
(508) 693-3341
Anna Edey is another friend of the New Alchemy Institute who has taken it upon herself to create economical, ecological methods of dealing with waste. The system shown on page 15 has been functioning since September 1984 in her Solviva Greenhouse with no flies, odors or other problems.
It consists of four 55-gallon drums connected end-to-end with their tops and half of their bottoms removed and slanted at about 50°. The inside of the chamber is lined with an impermeable layer of Loretex fabric to prevent fluid from coming into contact with drums and rusting them. The problem of fluid build-up (with resulting anaerobic conditions) is prevented by drainage of unabsorbed urine into a fifth drum located under the slanted chamber. This fluid is practically odor-free.
This system uses no venting or electricity. It takes two to three months for the wastes and sawdust/soil mixture to decompose into a rich humus. A base of good compost full of earthworms and microorganisms is left at the bottom of the compost chamber after each emptying as seed material for the next batch. After pasteurizing in a simple solar hot box (bringing it up to 160°F) it is free of any pathogens, and provides an excellent fertilizer and soil conditioner, safe for use in food production.
Anna has recently designed the finished version of the Solviva Composting Toilet integrating the various proven components of this system into a combination composting/solar pasteurizing toilet. Her aim is to satisfy the American dream of economy, ecological harmony, convenience and reliability.
Sol-Trans Solar Composting System
ECOS Water Conservation Systems Inc.
Damon Mill Square, Concord, MA 01742
(508) 369-3951 or (800) 462-3341 (in Mass.)
Cost: Permit rights are $750 plus 7% of the construction costs. Sol-Trans systems can be built by local handy-people or contracted out.
This system has been designed to incorporate the best of passive solar technology with the composting process. The Sol-Trans was developed for use where large amounts of waste are produced in remote, environmentally sensitive areas, such as national parks. The design incorporates the following features:
1. A solar collection device with a tough polycarbonate outer cover.
2. An integrated liquid/thermal storage/evaporation device.
3. A solar-assisted passive ventilation system to improve air flow.
4. Saturated vapor recycling to enhance the composting process by maintaining a proper moisture balance and transferring heat.
5. Air-tight, insulated construction and automatically controlled air flow to minimize heat loss and help maintain optimum temperatures for high-rate composting.
6. Quality construction with attention to operation and maintenance details (e.g. smooth, easy-to-clean fiberglass interior).
Figure 9. Clivus Multrum
Clivus Multrum
21 Canal Street, Lawrence, MA 01840
(508) 794-1700
NSF Approved
Cost: $4955 complete package for up to 5 people year-round
$5133 for 9 or more people year-round
The Clivus Multrum is the grandfather of modern composting toilets. It was developed in the 1930s in Sweden by R. Lindstrom and has been used extensively in the United States. The unit consists of a large, sloped bin which is placed in the room below the toilet. Kitchen scraps and toilet wastes are deposited in the bin and as they slowly move down the incline they decompose. The retention time of the wastes in the bin is several years, which is theoretically long enough for pathogens to die off. Pathogens are still a potential problem with this system, since older, composted material can be contaminated by being mixed with recently introduced wastes. The decomposed humus is removed by shovel from an access port in the front of the bin. Ventilation is achieved by a natural draft assisted by a fan which draws air through the composting chamber from the bathroom, avoiding odors in the house. Excess liquid accumulated in the bin can be removed with either a drain plug or electric pump.
Sun Mar
ECOS Water Conservation Systems Inc.
Damon Mill Square, Concord, MA 01742
(508) 369-3951 or (800) 462-3341 (in Mass.)
NSF Approved
Cost: $996 for Tropic model; $1199 for the XL; $1199 for the WCM
The Sun Mar company has come out with a series of composting toilets which have some unique features, the most unique of which, called the WCM, is a composting toilet which uses a water flush of less than one pint. Excess fluid from this system is drained out to a mini cesspool located nearby in the yard. The model XL requires electricity and handles up to four people year-round. The model TROPIC is smaller than the XL, uses no electricity and can handle two to four people for occasional uses. The WCM and XL employ a rotating drum which aerates and mixes the compost very effectively. All three of the systems have a compost chamber located in a separate space below the toilet room which can be semi-heated or unheated if the system is used only in warm seasons.
Figure 10. The Vira Carousel Composting Toilet
Vira Carousel
ECOS Water Conservation Systems Inc.
Damon Mill Square, Concord, MA 01742
(508) 369-3951 or (800) 462-3341 (in Mass.)
NSF Approved
Cost: $ 2628 small system, no heater or fan
$ 3336 small system with heater and fan
$ 3108 large system without heater or fan
$ 3815 large system with heater and fan
The Vira toilet is a fiberglass cylinder placed in a basement and divided into four composting compartments. When one compartment is filled, the cylinder is turned to present an empty compartment. The wastes of the filled compartments decompose as the empty compartments are used. It is designed to handle kitchen wastes as well as excrement. The cylinders must be emptied twice yearly and electricity for a fan and heating elements may be used, though the manufacturers describe how a solar hot air or water system could be used to replace the heating element.
Figure 11. The Humus Composting Toilet
Humus
ECOS Water Conservation Systems Inc.
Damon Mill Square, Concord, MA 01742
(508) 369-3951 or (800) 462-3341 (in Mass.)
Cost: $1051 Model: HT-91SEMI (semi-automatic stirring device)
$1074 HT-91SEMI/12V (12 volt model)
$1241 HT-MAO301 (automatic stirring device)
The Humus is widely recognized as one of the better of the small composting toilets. It can fit right inside a bathroom and looks much like a conventional toilet with a box underneath. The composting compartment is heated with an electrical element in order to pasteurize the compost and evaporate excess fluid. A year's use of this toilet results in only about two 5-gallon buckets of humus per person, 10% of the original mass of the wastes.
The Humus is more sensitive and requires more homeowner attention than the larger units do. The problem of overloading with fluids has been alleviated somewhat by having a liquid level indicator and manual drain located at the bottom of the unit. Other precautions can also be taken when heavy loading is anticipated.
The Humus needs to be emptied every month because of the small size of the compost chamber, but this is easily accomplished with a slide-out tray located below the chamber. After every use a bulking agent is added and the unit is stirred manually or automatically, depending on the model, with a built-in mechanism.
This toilet is especially well suited to vacation homes (up to four people full-time), as an additional toilet in a basement or attic, or for work sites. At least two units would be necessary for the average year-round family house.
Figure 12. The Biorecycler Composting Toilet
Biorecycler Toilet
Jeremy Criss, 5308 Emerald Drive, Sykesville, MD 21784
301-795-2607
Cost: $1800
The Biorecycler, a composting toilet designed to produce large amounts of high quality compost, has a number of novel features. The most pronounced is that the toilet can be located up to 40 feet away from the composting chamber. This is accomplished by use of a vacuum tube powered by a compressor. The advantages of this are that it eliminates the potential for odors in the bathroom, creates a degree of freedom in the placement of the compost chamber, and provides for a much more aesthetically acceptable toilet.
Another feature of this system is that the composting chamber has been designed to use worms to decompose the wastes into a usable product. This is a patented process developed by Mr. Criss which results in high-quality, low-pathogen worm castings that are removed from the chamber periodically.
Another attractive feature of the Bio-Recycler is that it diverts fluids to a separate holding tank. This 'manure tea' is a combination of urine and water from the flusher which filters through the compost and is collected in a container below the composting chamber. This tea is then poured on a separate outdoor compost pile where it acts as a nitrogen source for microbial activity. This system eliminates the possibility of insects in the bathroom and requires minimal electricity.
Some provisions for gray water management must be built into all compost toilet systems. Gray water can be used or disposed of in a number of different ways. Depending on the gray water source and household's situation, certain treatment and reuse schemes are more appropriate than others.
A septic tank and leach field system, as described earlier, can be used for primary treatment of gray water to separate solids and grease from the waste stream. Some states allow for a reduction in the size of the leach field when a composting toilet is used.
Sand filtration represents a cheap and effective means of gray water purification. It is especially suited for the removal of organic material, suspended solids, and pathogens such as bacteria, viruses and the eggs and cysts of parasites. Sand filtration systems have been developed in recent years which are documented to be quite effective in pathogen removal. After filtration the effluent can be disposed of in a reduced leach field or reused as 'utility' water to flush toilets, irrigate crops or water a lawn, though most health officials would go gaga at the thought of these practices.
When gray water is used for irrigating plants certain precautions need to be taken. It should be dispersed over a large area to avoid the build-up of harmful ingredients such as salts and it should be applied directly to soils, not sprayed, to prevent the introduction of pathogens into the air. Gray water should be diluted or alternated with fresh water when applied to potted plants or young seedlings. Avoid using gray water on root or leaf crops that are eaten raw, like carrots and lettuce. Fruit trees, perenniels, and ornamentals are appropriate recipients of gray water. Do not use gray water on acid-loving plants because it contains salts which can harm them.
Figure 13. Abby Rockefeller's Greenhouse Leach Field Design
A good example of an appropriate technology which integrates a
number of systems is the use of gray water to irrigate crops grown
in a home greenhouse (Rockefeller & Lindstrom 1977). Developed
by Abby Rockefeller and Carl Lindstrom, this technology has worked
well in Abby's home greenhouses for over ten years. The green-house
beds are sized by the volume of gray water to be processed. After
pretreatment with a sand filter (Clivus Multrum manufactures a
good model), the effluent is pumped into the greenhouse soil beds.
The soil beds are slightly sloped with a drain at the lower end.
Crops planted in the soil boxes take up nutrients and water. The
water not taken up either by the plants or soil is recycled or
disposed of. When a system such as this is being used by a household
a relatively high degree of care must be taken to limit the toxins
entering the system. Paint thinners, paints or pesticides should
never be washed down the drain, and substances such as ammonia
and chlorine should be so disposed only in very limited quantities.
It is beyond the scope of this Technical Bulletin to give more than a cursory overview of gray water treatment. Those wishing to learn more are advised to get Robert Kourik's lively and informative mini-manual Gray Water Use in the Landscape (available through the New Alchemy store).
Bennett, E.R., K.D. Linstedt, and J. Felton. 1975. "Comparison of Septic Tank and Aerobic Treatment Units: The impact of Wastewater Variations on These Systems." In Water Pollution Control in Low Density Areas: Proceedings of a Rural Environmental Engineering Conference, edited by W.J. Jewell and R. Swan. Ithaca, NY: Cornell University.
Canter, L.W., and R.C. Knox. 1986. Septic Tank System Effects on Ground Water Quality. Chelsea, MI: Lewis Publishers.
Hall, M.W. 1975. "A Model of Nutrient Transport in Subsurface Systems." In Water Pollution Control in Low Density Areas: Proceedings of a Rural Environmental Engineering Conference, edited by W.J. Jewell and R. Swan. Ithaca NY: Cornell University.
Rockefeller, Abby and Carl Lindstrom. 1977. Gray water for the Greenhouse. Compost Science, September/October 1977.
U.S. Environmental Protection Agency. 1980. Design Manual: On-Site Wastewater Treatment and Disposal Systems (EPA 625/1-80-012). Cincinnati, Ohio.
Absorption: The process by which one substance is physically taken into and included within another substance, as the absorption of water by soil.
Activated Sludge Process: A biological wastewater treatment process in which a mixture of wastewater and aerobically decomposed sludge is agitated and aerated.
Aerobic: Growing or occurring in the presence of oxygen, such as aerobic bacteria.
Anaerobic: Growing or occurring in the absence of oxygen, such as anaerobic bacteria.
Biochemical Oxygen Demand (BOD): A measure of the concentration of organic impurities in water, BOD is the amount of oxygen required by bacteria to decompose organic matter under aerobic conditions.
Blackwater: Liquid and solid human body waste and the carriage waters generated by toilet use.
Bulking Agent: An organic material, high in carbon, which is added to a composting process in order to create air spaces, establish the proper carbon-to-nitrogen ratio for biological activity, and absorb excess fluids.
Carbon, Organic: A limiting nutrient in aerobic decomposition. Organic carbon is used for energy generation by bacteria. Good sources of it include wood products with a high surface area, such as shavings and sawdust, rice hulls, peat and organic kitchen wastes.
Coliform-Group Bacteria: A group of bacteria predominantly inhabiting the intestines of humans or animals, but occasionally found elsewhere. It is a nonharmful organism used as an indicator of human fecal contamination in water.
Compost: Organic material that has been biologically stabilized by aerobic bacteria and other organisms.
Crevice: A narrow crack or opening in the bedrock below the soil's surface.
Denitrification: The biochemical reduction of nitrate or nitrite to gaseous molecular nitrogen or an oxide of nitrogen.
Effluent: Sewage, water or other liquid which is partially or completely treated or in its natural state, flowing out of a reservoir, basin or treatment plant.
Eutrophic: A term applied to a body of water which has a concentration of nutrients optimal, or nearly so, for plant growth.
Gray water: Wastewater generated by water-using fixtures and appliances, excluding the toilet and possibly the garbage disposal.
Humus: Aerobically decomposed organic matter which is rich in microbial activity.
Leaching: The removal of materials in solution from the soil.
Leach Field: A mechanism of effluent disposal which employs perforated pipe sur-rounded by gravel and buried underground.
Nitrate: The soluble form of nitrogen which acts as a fertilizer to plants and a mild toxin to humans.
Nitrification: The biochemical oxidation of ammonia to nitrate.
Nitrogen, Organic: Nitrogen combined in organic molecules, such as proteins and amino acids. Within the context of compost, organic nitrogen is an essential nutrient, used for bacterial cell metabolism.
Pathogenic: Causing disease. It is also used to designate microbes which commonly cause infectious diseases, as opposed to those which do so uncommonly or never.
Percolation: The flow or trickling of a liquid downward through a contact or filtration medium.
Permeability, Soil: The ease with which gasses, liquids or plant roots penetrate or pass through the soil.
Primary Treatment: In wastewater treatment, the first stage whereby large solids are settled out and removed.
Slope: Deviation of a flat surface from the horizontal.
Sludge: The accumulated solids which have settled to the bottom of a waste treatment tank.
Soil Type: In mapping soils, a subdivision of a soil series based on differences in texture of the A horizon (uppermost layer).
Suspended Solids (SS): Small particles of solid pollutants in sewage that contribute to turbidity and resist separation by conventional means.
Topsoil: The presumably fertile, biologically active soil material found in the A horizon which is moved during cultivation and which is used to topdress roadbanks, gardens and lawns.
Water Table: That level in soil to which the subsurface water level reaches.
We All Live Downstream: A Guide to Wastewater Treatment That Stops Water Pollution. 1986. Costner, P., H. Gettings, and G. Booth. A lively and informative publication on the detrimental effects of presently accepted waste treatment technologies with good descrip-tions of viable, environmentally-sound options for the home. It includes sections on composting toilets, gray water recycling, an exhaustive list of water conservation devices and the story of how one town fought a powerful bureaucracy for environmentally-sound waste treatment. Available for $6.00 from the National Water Center, P.O. Box 548, Eureka Springs, AR 72632.
Design Manual: On-Site Wastewater Treatment and Disposal Systems. 1980. The U.S. EPA, publication #625/1-80-012. The standard text on conventional on-site waste treatment methods and technologies. It includes sections on site evaluation procedures, wastewater characteristics, treatment and disposal methods (including sand filtration, aerobic digesters and disinfection), appurtenances, residuals disposal and management of on-site systems.
Goodbye to the Flush Toilet. 1977. Edited by Carol Stoner. Rodale Press. An informative book on the subject of composting toilets which, while somewhat dated, continues to be a valuable resource. This book gives a good general background on the failings of present waste technologies as well as an overview of the composting process and a number of composting toilets. Gray water treatment and water conservation are also discussed.
Compost Toilets: A Guide for Owner-Builders. A well written document which covers most of the important aspects of owner built composting systems. Sections include health implications, basic designs, construction parameters, and design problems and solutions, along with descriptions of a number of different styles. Available for $4.00 from the National Center for Appropriate Technology, P.O. Box 3838, Butte, MT 59701.
55 Gallon Drum Compost Toilet: Guidebook and Plans. Stan Slaughter. A description of one of the easiest and cheapest techniques for composting human waste. Available for $5.00 from Slaughter Energy Enterprises, 17 Vale Road, Kansas City, MO 64138.
The EPA National Small Flows Clearinghouse, 258 Stewart Street, West Virginia University, Morgantown WV 26506; phone: 800-624-8301. This organization was set up in 1977 through the Clean Water Act in order to facilitate the design, planning and construction of innovative and alternative decentralized wastewater treatment facilities in areas where conventional systems are not economically feasible. Programs include a newsletter, computer bibliographies on topics ranging from composting toilets to failing septic systems, design modules to help in evaluating technologies ranging from mound systems to vacuum sewers, septage management and novel alternatives, and case studies of a number of different decentralized waste systems. A forthcoming project involves the videotaping of various aspects of select waste treatment technologies.
Now closed, The New Alchemy Institute was a nonprofit organization dedicated to promoting environmentally sound, cost-effective methods for providing food, energy, and shelter. Founded in 1969, the Institute conducted integrated research, education, and outreach programs in solar and energy-efficient building design, small-scale organic agriculture, and greenhouse vegetable and fish production.
New Alchemy Institute research was directed at home and small farm audiences in the Northeastern United States and centers around three major themes:
1. Household-scale research directed at designing and building an ecologically sound, innovative, and practical demonstration house and landscape on the Institute's Cape Cod site.
2. Greenhouse research focused on commercial-scale food production; energy conservation; compost use as a source of heat and carbon dioxide; linked aquaculture/hydroponics systems; and biological control of pests.
3. Market garden research including the economics of market gardening and the needs of small farmers; season extenders; appropriate equipment; and biological pest control.
The Technical Bulletin series was created in order to provide practical information to homeowners, gardeners and small-scale farmers.