Ponds and Aquaculture-Polyculture in Ecological Wastewater-Treatment Systems

Ponds and Aquaculture-Polyculture in Ecological Wastewater-Treatment Systems

Refer to Chapter 4 of the book

Despite their deceptively simple appearance (i.e., resembling a big hole in the ground filled with wastewater), ponds are actually complex and dynamic ecosystems with untold 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.

History: Aquaculture-based wastewater-treatment ponds can be traced back more than 2,000 years to China to as far back as 473 BCE, and during China's Tang Dynasty (618-903 CE), fish-aquaculture and fish-polyculture ponds (stocked with grass carp, bighead carp, silver carp, and black carp) were used in the management and treatment of human sewage, night soil (human wastes or excrement), poultry wastes, and other animal manure (Hosetti and Frost, 1995). In recent decades, fish- and prawn-based aquaculture and polyculture wastewater-treatment ponds, either full- or pilot-scale, have been designed and built in India, Malaysia, Hong Kong, Taiwan, Singapore, Israel, Hungary, Germany, Egypt, and China (Hosetti and Frost, 1995).

These types of systems are designed and built 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. Several case studies of small communities using aquaculture- and polyculture-based wastewater-treatment systems are presented in Chapter 4.

** Author's Ethical Statement: The author does not endorse, promote, or recommend animal-based agriculture and aquaculture in which animals are killed for their flesh. The author does not support or promote the exploitation or killing of animals in agriculture and wastewater treatment.

Photographs: Views of several maturation and polishing ponds for purifying wastewater.

This is a maturation/polishing pond with macrophytes planted in the center of the pond and with a solar-powered aerator (for oxygenation and aeration of the pond). To make the pond aesthetically presentable, one can plant a wide variety of ornamental, medicinal, or edible plants around the pond. (Photographs by Jo-Shing Yang, in southern California)

This is also a polishing pond for treating tertiary effluent from a conventional sewage plant in southern California. This pond is unaerated and unplanted. (Photograph by Jo-Shing Yang)