Graywater Systems

There are two concepts that sum up this book: 1) one organism's excretions are another organism's food, and 2) there is no waste in nature. We humans need to understand what organisms will consume our excretions if we are to live in greater harmony with the natural world. Our excretions include humanure, urine and other organic materials that we discharge into the environment, such as "graywater," which is the water resulting from washing or bathing. Graywater should be distinguished from "blackwater," the water that comes from toilets. Graywater contains recyclable organic materials such as nitrogen, phosphorous and potassium. These materials are pollutants when discarded into the environment. When responsibly recycled, however, they can be beneficial nutrients.

My first exposure to an "alternative" wastewater system occurred on the Yucatan Peninsula of Mexico in 1977. At that time, I was staying in a tent on a primitive, isolated, beach-front property lined with coconut palms and overlooking the turquoise waters and white sands of the Caribbean. My host operated a small restaurant with a rudimentary bathroom containing a toilet, sink and shower, primarily reserved for tourists who paid to use the facilities. The wastewater from this room drained from a pipe, through the wall, and directly into the sandy soil outside, where it ran down an inclined slope out of sight behind the thatched building. I first noticed the drain not because of the odor (there wasn't any that I can remember), but because of the thick growth of tomato plants that cascaded down the slope below the drain. I asked the owner why he would plant a garden in such an unlikely location, and he replied that he didn't plant it at all — the tomatoes were volunteers; the seeds sprouted from human excretions. He admitted that whenever he needed a tomato for his restaurant, he didn't have to go far to get one. This is not an example of sanitary wastewater recycling, but it is an example of how wastewater can be put to constructive use, even by accident.

From there, I traveled to Guatemala, where I noticed a similar wastewater system, again at a crude restaurant at an isolated location in the Peten jungle. The restaurant's wastewater drain irrigated a small section of the property separate from the camp sites and other human activities, but plainly visible. That section had the most luxurious growth of banana plants I had ever seen. Again, the water proved to be a resource useful in food production, and in this case, the luxurious growth added an aesthetic quality to the property, appearing as a lush tropical garden. The restaurant owner liked to show off his "garden," admitting that it was largely self-planted and self-perpetuating. "That's the value of drain water," he was quick to point out, and its value was immediately apparent to anyone who looked.

All wastewater contains organic materials, such as food remnants and soap. Microorganisms, plants and macroorganisms consume these organic materials and convert them into beneficial nutrients. In a sustainable system, wastewater is made available to natural organisms for their benefit. Recycling organic materials through living organisms naturally purifies water.

In the U.S., the situation is quite different. Household wastewater typically contains all the water from toilet flushings (blackwa-ter) as well as water from sinks, bathtubs and washing machine drains (graywater). To complicate this, many households have in-sink garbage disposals. These contraptions grind up all of the food material that could otherwise be composted, then eject it into the drain system. Government regulators assume the worst-case scenario for household wastewater (lots of toilet flushings, lots of baby diapers in the wash, and lots of garbage in the disposal unit), then they enact regulations to accommodate this scenario. Wastewater is therefore considered a public health hazard which must be quarantined from human contact. Typically, the wastewater is required to go directly into a sewage system, or, in suburban and rural locations, into a septic system.

A septic system generally consists of a concrete box buried underground into which household wastewater is discharged. When the box fills and overflows, the effluent drains into perforated pipes that allow the water to percolate into the soil. The drain field is usually located deep enough in the soil that surface plants cannot access the water supply.

In short, conventional drainage systems isolate wastewater from natural systems, making the organic material in the water unavailable for recycling. At wastewater treatment plants (sewage plants), the organic material in the wastewater is removed using complicated, expensive procedures. Despite the high cost of such separation processes, the organic material removed from the wastewater is often buried in a landfill.

The alternatives should be obvious. Albert Einstein once remarked that the human race will require an entirely new manner of thinking if it is to survive. I am inclined to agree. Our "waste disposal" systems must be rethought. As an alternative to our current throw-away mentality, we can understand that organic material is a resource, rather than a waste, that can be beneficially recycled using natural processes.

In pursuing this alternative, the first step is to recycle as much organic material as possible, keeping it away from waste disposal systems altogether. We can eliminate all blackwater from our drains by composting all human manure and urine. We can also eliminate almost all other organic material from our drains by composting food scraps. As such, one should avoid using an in-sink garbage disposal. As an indication of how much organic material typically goes down a household drain, consider the words of one composting toilet manufacturer, "New regulations will soon demand that septic tanks receiving flush toilet and garbage disposal wastes be pumped out and documented by a state certified septage hauler every three years. When toilet and garbage solids and their associated flush water are removed from the septic system and the septic tank is receiving only graywater, the septic tank needs pumping only every twenty years." 1 According to the U.S. EPA, household insink garbage disposal units contribute 850% more organic matter and 777% more suspended solids to wastewater than do toilets.2

The second step is to understand that a drain is not a waste disposal site; it should never be used to dump something to "get rid of it." This has unfortunately become a bad habit for many Americans. As an example, a friend was helping me process some of my home-made wine. The process created five gallons of spent wine as a by-product. When I had my back turned, the fellow dumped the liquid down the sink drain. I found the empty bucket and asked what happened to the liquid that had been in it. "I dumped it down the sink," he said. I was speechless. Why would anyone dump five gallons of food-derived liquid down a sink drain? But I could see why. My friend considered a drain to be a waste disposal site, as do most Americans. This was compounded by the fact that he had no idea what to do with the liquid otherwise. My household effluent drains directly into a constructed wetland which consists of a graywater pond. Because anything that goes down that drain feeds a natural aquatic system, I am quite particular about what enters the system. I keep all organic material out of the system, except for the small amount that inevitably comes from dishwashing and bathing. All food scraps are composted, as are grease, fats, oils and every other bit of organic food material our household produces. This recycling of organic material allows for a relatively clean graywater that can be easily remediated by a constructed wetland, soilbed or irrigation trench. The thought of dumping something down my drain simply to dispose of it just doesn't fit into my way of thinking. So I instructed my friend to pour any remaining organic liquids onto the compost pile. Which he did. I might add that this was in the middle of January when things were quite frozen, but the compost pile still absorbed the liquid. In fact, that winter was the first one in which the active compost pile did not freeze. Apparently, the 30 gallons of liquid we doused it with kept it active enough to generate heat all winter long.

Step three is to eliminate the use of all toxic chemicals and non-biodegradable soaps in one's household. Chemicals will find their way down the drains and out into the environment as pollutants. The quantity and variety of toxic chemicals routinely dumped down drains in the U.S. is both incredible and disturbing. We can eliminate a lot of our wastewater problems by simply being careful what we add to our water. Many Americans don't realize that most of the chemicals they use in their daily lives and believe to be necessary are not necessary at all. They can simply be eliminated. This is a fact that will not be promoted on TV or by the government (including schools), because the chemical industry might object. I'm quite sure that you, the reader, don't care whether the chemical industry objects or not. Therefore, you willingly make the small effort necessary to find environmentally benign cleaning agents for home use.

Cleaning products that contain boron should not be used with graywater recycling systems because boron is reportedly toxic to most plants. Liquid detergents are better than powdered detergents because they contribute less salts to the system.3 Water softeners may not be good for graywater recycling systems because softened water reportedly contains more sodium than unsoftened water, and the sodium may build up in the soil, to its detriment. Chlorine bleach or detergents containing chlorine should not be used, as chlorine is a potent poison. Drain cleaners and products that clean porcelain without scrubbing should not be drained into a graywater recycling system.

Step four is to reduce our water consumption altogether, thereby reducing the amount of water issuing from our drains. This can be aided by collecting and using rainwater, and by recycling gray-water through beneficial, natural systems.

The "old school" of wastewater treatment, still embraced by most government regulators and many academics, considers water to be a vehicle for the routine transfer of waste from one place to another. It also considers the accompanying organic material to be of little or no value. The "new school," on the other hand, sees water as a dwindling, precious resource that should not be polluted with waste; organic materials are seen as resources that should be constructively recycled. My research for this chapter included reviewing hundreds of research papers on alternative wastewater systems. I was amazed at the incredible amount of time and money that has gone into studying how to clean the water we have polluted with human excrement. In all of the research papers, without exception, the idea that we should simply stop defecating in water was never suggested.


It is estimated that 42 to 79% of household graywater comes from the bathtub and shower, 5 to 23% from laundry facilities, 10 to 17% from the kitchen sink or dishwasher, and 5 to 6% from the bathroom sink. By comparison, the flushing of blackwater from toilets constitutes 38 to 45% of all interior water use in the U.S., and is the single largest use of water indoors. On average, a person flushes a toilet six times a day.4

Various studies have indicated that the amount of graywater generated per person per day varies from 25 to 45 gallons (96 to 172 liters), or 719 to 1,272 gallons (2,688 to 4,816 liters) per week for a typical family of four.5 In California, a family of four may produce 1,300 gallons of graywater in a week.6 This amounts to nearly a 55-gallon drum filled with sink and bath water by every person every

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