How to Get Your Home Off the Water "Grid"

By Jo-Shing Yang, AlterNet. Posted February 9, 2009.

Ponds in Sustainable Ecological Wastewater Treatment: Simulating Nature's Processes of Degrading Wastes

Ponds have been characterized as a "low-tech" and "old-fashion" method of sewage treatment. Despite their deceptively simple appearance -- resembling a hole in the ground filled with wastewater -- ponds are actually complex and dynamic ecosystems with untold trillions of microorganisms forming numerous intricate food chains suspended in the water column, inhabiting pond sediments, and attaching to various surfaces in the pond.

The organisms in the ponds include bacteria, viruses, protozoa, zooplankton, phytoplankton, algae, fungi, rotifers, insects and insect larvae, crustaceans, worms, shrimps, snails, fishes, and plants, among thousands of species of organisms. Numerous sequences of chemical, biological, physical, and biochemical reactions and processes occur within the ponds during the time wastewater is in the ponds. Ponds are far more complex than any other waste-treatment systems designed and engineered by human beings. Although reactions and processes occurring in the ponds are difficult to model, all types of wastewater-treatment ponds are relatively easy and inexpensive to design, construct, operate, and maintain.

Ponds are a low-cost and environmentally sustainable technology for wastewater treatment in developing countries, but they are not commonly used in industrialized countries, except in small rural and remote communities. Various researchers have estimated that the United States had about 7,000 pond systems in 1975; Canada 868 ponds in 1981; and France, approximately 1,800 ponds in 1987 and 2,500 in 1993 in small, rural communities. In France, lagoons represented about 26.9% of 976 very small municipal wastewater-treatment plants for communities with fewer than 2,000 population equivalent (p.e.), and in Bavaria, Germany, more than 1,500 rural communities each with fewer than 5,000 people, use ponds for wastewater treatment.

Scientists generally recognize that four major biological and biochemical processes occur simultaneously but at different zones in wastewater ponds: microbial aerobic and anaerobic biodegradation and biotransformation, photosynthesis, and sedimentation. Other reactions and processes also occur: predation on bacteria and other microorganisms by rotifers and zooplankton, fermentation of settled solids and sludge at pond bottom (in which biogas, comprising 65 percent methane, is generated), pH shifts in pond water, algae exuding algal toxins that eliminate pathogenic microorganisms (e.g., fecal coliforms), and many other processes.

Aquatic plants and macrophytes can be planted in the wastewater ponds to facilitate purification and waste recycling. These types of systems are based on the ideas that resource recycling and recovery are critical to environmental sustainability, and that closing the production-and-consumption loop is important for maintaining soil fertility and agricultural productivity in the long term.

What the critics of pond systems do not fully consider and appreciate is that this appropriate technology is flexible (i.e., it can be combined with other treatment units such as constructed wetlands and sand filters in an integrated wastewater-treatment system); simple and inexpensive to design, construct, operate, and maintain; and environmentally sustainable because no fossil fuels and chemicals are required for effective sewage treatment. In essence, pond systems offer communities a great measure of self-reliance and self-sufficiency, which they cannot obtain using conventional treatment technologies.

Just as the local food and slow food movements try to raise public awareness about chemical-intensive, corporate-controlled monoculture, we should do the same in the water field: teach people sustainable and ecological technologies for building and operating their natural, small, and decentralized water and wastewater treatment systems. It is time that people and their communities learn to manage their own water and wastewater without being held hostage by multinational engineering corporations and financial institutions such as Bechtel, Dow Chemical, and the World Bank/International Monetary Fund.

See more stories tagged with: water, wastewater, sewage, water systems

Jo-Shing Yang is the author of "Ecological Planning, Design, and Engineering. Solving Global Water Crises: New Paradigms in Wastewater and Water Treatment. Small and On-Site Systems for Community Water Self-Sufficiency and Sustainability."

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