Q&A with Dr. Mark Nelson, Author of The Wastewater Gardener

Composting toilet

Composting toilet

Eco-system engineer Dr. Mark Nelson has spent decades working on wastewater recycling, the restoration of damaged ecosystems and related research. He was one of eight people who lived inside Biosphere 2, a closed sustainable community experiment, for two years. Now he’s just published The Wastewater Gardener: Preserving the Planet One Flush at a Time, a book that compiles his years of knowledge. He answers a few key questions here about the Wastewater Garden concept he’s developed as well as the politics of poo and how city dwellers can take steps toward green living.

First of all, what is a Wastewater Garden?

A Wastewater Garden (WWG) is a constructed wetland that’s used to treat and reuse sewage, or wastewater. In building one, we reproduce the conditions of natural wetlands, called the “kidneys of the Earth” by scientists for their high capacity of water recycling in the biospheric cycles. The subsurface-flow design of a WWG keeps the wastewater below the surface (of dry gravel in the constructed wetland and beneath the soil in the final irrigation step)—ensuring there are no bad smells or accidental human contact.

Wastewater is a rich resource of fresh water and nutrients that often goes unused, so we make gardens with it. Both the constructed wetland and the subsoil irrigation leach drain are planted with beautiful and useful plants.

In the book, you discuss the history of how we deal with waste—how poo became taboo. When and why did we shift from using human waste as a valuable fertilizer to keeping it out-of-sight-out-of-mind?

When city populations became very large and the adoption of indoor plumbing meant human waste was now combined with large amounts of water, the sewage situation became very dangerous. So it was decided for public health reasons to build expensive infrastructure to pump all human wastewater away from people’s houses and businesses to centralized sewage treatment plants. In Asia, the tradition of using composted human waste (“night soil” collected from large cities and sold to farmers) lasted longer, but larger urban populations and a dramatic increase in water usage, has made traditional re-use impossible. But in developing countries, by and large, centralized sewage systems are too expensive and so sewage is mostly untreated, causing serious health issues through pollution of potable water sources.

How much of an impact could it have on our freshwater supply if we stopped using potable water to flush waste?

Huge impact. It takes MANY TONS of water to flush away the waste products of each person who uses a flush or squat toilet. Human waste also contains a lot of valuable plant nutrients—nitrogen, phosphorus, potassium—which originally came from our agricultural soils. Throwing that away is extremely wasteful and unsustainable.

What is the most common “itinerary of shit” in most U.S. cities? How does that compare to countries around the world?

U.S. cities, like those in Europe and other developed countries, typically have one or two large sewage treatment plants. All the city’s houses and businesses/industries are connected to these sewage treatment plants with a network of pumping stations and underground piping.

When the sewage and industrial wastewater gets to the treatment plant, a lot of energy and chemicals are used to treat the sewage. Then the treated wastewater is typically sent to the nearest river, lake or ocean to “get rid of it.”

In many cities, sewage systems also collect rain runoff so when there’s a heavy rain, the volume of combined sewage and rain is often more than sewage plants can handle, resulting in some wastewater being sent directly to the receiving body of water without any treatment at all. There the wastewater, treated or untreated, causes pollution and all the fresh water and plant nutrients are wasted.

If the sewage treatment plant does “advanced treatment,” more nutrients are removed—at even greater expenditures of money, energy and chemicals. The remaining “bio-solids” or “sludge” is difficult to dispose of—and poses dangers to farmlands if spread there because industrial pollutants (heavy metals, synthetic chemicals, etc.) are mixed with the residential sewage.

How do you propose we open up the dialogue and talk about shit?

We need to remove the taboo and have frank discussions of the subject. Now that there is concern about how we make our practices “sustainable,” coupled with using more natural, local, decentralized solutions (which also use less energy and machinery/chemicals), the alternatives to our current method of “treat and throw away” become far more attractive. Once we understand the subject, without undue fear or emotion, we can see that human waste products are a natural resource. And by reviewing the history of how we’ve arrived at our current way of dealing with it, we can intelligently discuss alternatives.

Some U.S. cities facing drought are considering toilet-to-tap water—is greywater safe to drink?

Greywater or treated wastewater could be brought to potable water standards. But such systems are expensive and raise issues of consequences should there be problems with the treatment plants. A far better approach, I think, is to implement policies that 1) reduce overall water consumption by people and industry; 2) use greywater and toilet water for greening projects, landscaping and farming use, which correctly handle the possible contaminants and disease-causing bacteria and 3) reserve high-quality potable water for drinking, cooking and personal hygiene.

When did you start developing the idea behind the Wastewater Garden system?

I started using “humanure” (human wastes composted) for fertilizing trees and animal manures for general soil improvement at Synergia Ranch in the 1970s. That experience prepared me for our use of “constructed wetlands” in Biosphere 2 to treat and reuse all our waste products and those of our domestic animals. Those constructed wetlands were beautiful gardens that helped feed our domestic animals by producing fodder, periodically cut from the abundant vegetation. The constructed wetland also returned nutrients to the irrigation supply for the Biosphere 2 farm which fed the eight biospherians during our two-year experiment. Seeing how beautiful such systems are—and the reaction of the hundreds of thousands visitors to the facility—made me think that doing research in this field and bringing such systems to applications around the world, would be a very worthwhile—and exciting—endeavor to pursue.

Where have you installed Wastewater Gardens?

Mexico, Indonesia (Bali, Sulawesi, Java), Western Australia, the United States, Belize, the Bahamas, France, Spain, Portugal, Algeria, Poland, New Zealand, Puerto Rico, the Philippines.

What goes into each installation? What’s the average cost of a building a Wastewater Garden, say, for a private home?

The basic ingredients are: a geomembrane or concrete liner (in countries with low labor costs), screened gravel, PVC pipes, septic tank and control box, perforated subsoil irrigation pipes, plants chosen for climate. Costs depend on local costs—in Mexico we built Wastewater Gardens for private homes for as low as $1,500-2,000. In Europe or the U.S. it costs twice as much; in Indonesia they are less expensive.

What are some of the issues you’ve run into in various climates and ecosystems? Can Wastewater Gardens be built in a cold climate?

They can be built in cold climates—many have been done in places like northern Europe or Canada—as well as in hot tropical climates and desert regions. We make a study of which plants will work in different regions, wetland-tolerant plants/trees for the Wastewater Garden and decorative or fruiting shrubs and trees for the subsoil irrigation area. In making systems around the world, we’ve had to deal with torrential tropical rainfalls, searing desert heat and sandstorms, high water tables and nearly impenetrable rock.

You’re currently working on the Eden in Iraq Project to improve health of the Marsh Arabs and protect the historic marshes in the Iraqi desert. Tell us about that.

The project was conceived and is directed by Meridel Rubinstein of Nanyang Technological University in Singapore and is an art/ecology project symbolizing ecological and cultural renewal in one of the world’s oldest cultures—and in the Fertile Crescent between the Euphrates and Tigris Rivers, the birthplace of Western civilization.

The Marsh Arabs had their ancient culture disrupted when the rivers were diverted in the 1990s, under Saddam Hussein’s regime, turning one of the world’s greatest natural wetlands into a desert. But the diversion canals were breached in 2003 and the wetlands are coming back, along with up to half a million Marsh Arabs.

Our project will build beautiful Wastewater Gardens for Marsh Arab towns of 5,000-20,000 people—preventing the spread of disease and pollution of the marshes since there is no sewage treatment at present. (For more information, visit www.meridelrubenstein.com/eden-iniraq)

For city dwellers who don’t have the option to install a Wastewater Garden in their backyard, what steps can they take toward green living?

Some good starters: conserve water, investigate if your city permits greywater recycling (which can be used to water your landscape plants), grow as much food as you can organically (there’s nothing like home-grown food, and you’re reducing all the transport, chemicals and ecological damage done by our agribusiness), see if composting toilets are permitted, and learn how to safely compost your organic waste. Also, get involved in
community gardens and other grassroots initiatives.

How do we educate future generations on wastewater recycling?

In a world of increasing water scarcity, the threat of climate change, and a desire to grow local healthy food, teaching the basics of sound wastewater management and recycling should be part of everyone’s “ecological literacy.” This education should include learning both the history of how different cultures have used wastes and becoming acquainted with modern approaches and options which are more ecologically sound and sustainable. And hopefully inventing new ones!

Tell us where we can find out more about the book and your work.

The Wastewater Gardener: Preserving the Planet One Flush at a Time is available in local bookstores and online (Synergetic Press, June 2014): www.wastewatergardener.com. The Wastewater Garden website is: www.wastewatergardens.com. Biosphere 2 information is at www.biospherics.org. The Institute of Ecotechnics, the ecological organization I head, is at www.ecotechnics.edu.

image: Earthfix (Creative Commons BY-NC)

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