Sewage marshes as nature sanctuaries
Adapted extract from an article by Doug Stewart in the Smithsonian (USA), monitored for the Institute by Roger Knights.
'Sewage has been meandering through the park's chain of man-made marshes'
The Arcata Marsh and Wildlife Sanctuary is a 154 acre wetlands park about 280 miles up the coast from San Francisco. This quiet and perfectly pleasant-smelling park has turned Arcata into a tourist stop and bird-watching mecca. It also enables the town to meet California's strict sewage-discharge standards. Since 1986, partially treated sewage from the town's conventional primary treatment plant has been meandering through the park's chain of man-made marshes. After a two-month odyssey, it's piped into Humboldt Bay. The discharged marsh water is generally clearer and cleaner than the water already in the bay.
The system's low-key simplicity won the city a $100,000 grant from the Ford Foundation's Innovations in Government programme, and has set off a flood of enquiries from mayors and town engineers throughout the States.
Bob Gearheart, a professor of environmental engineering at the local college, Humboldt State University, had helped set up crop-irrigation systems using wastewater in several Third World communities. In developing countries, he found, high-quality fresh water was often unavailable and chlorine unaffordable.
The design he helped produce for Arcata involved digging out ponds from 32 acres of desolate waterfront land where a series of abandoned and decrepit lumber mills stood, dominated by an old county dump. Each marsh has a balance of open water and marsh plants. The shapes of the marshes are pleasantly irregular, and small man-made islands punctuate their surfaces. 'What really does the work here are the micro-organisms that grow around the roots and stems of these cattails.' The stem of the cattail is slippery, evidence of underwater bacteria and fungi that have latched onto it to feed on the organic nutrients in the water flowing past - tiny biological filters, in effect.
'The wetlands flora attract astounding numbers of waterfowl, herons, hawks'
Duckweed, cattails, pennywort and hard-stem bullrushes flourish in this nutrient-rich swamp water. The wetlands flora, in turn, attract astounding numbers of waterfowl: ducks, coots, egrets, herons, hawks, avocates, pelicans, peregrine falcons. And joggers huff down the redwood-chip trails, and office workers on their lunch breaks sit reading in parked cars. A visitors' centre is being planned for the park, and there's talk of posting signs inside the toilet stalls that will read: 'Thank you for your contribution.'
Bob Gearheart, Professor of Environmental Engineering, Humboldt State University, Arcata, Northern California, USA.
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