Integrated Wastewater and Sludge Treatment in a Tree Farmby Robert E. Hoffman, Univ of Nebraska-Lincoln, Omaha, NE, USA,
Martha W. Gilliland, Univ of Nebraska-Lincoln, Omaha, NE, USA,
Gary B. Keefer, Univ of Nebraska-Lincoln, Omaha, NE, USA,
Abstract: A system which integrates land treatment of wastewater following primary sedimentation with tree production and sludge composting was evaluated for its land requirements, costs, and energy use. Costs and energy use were compared to an equivalent conventional secondary treatment (trickling filter) system with land application of sludge. A one million gallons per day operation produces about 890 wet tons per year of compost and 9 billion Btu's per year of firewood (750 tons per year). Land requirements for the same size operation are about 90 acres, with nitrogen uptake rates constraining wastewater application rates. With the ridge and furrow irrigation method and no credit for the value of the firewood or compost, the present worth costs of the integrated system are 30% more than the conventional system. If firewood is assigned a value of 1. 80 per million Btu's (1984), then the integrated system costs only 15% more than the conventional system, and 28 times more energy is produced as firewood than is consumed as natural gas and electricity.
Subject Headings: Sludge | Soil treatment | Integrated systems | Wastewater treatment | Trees | Composting | Energy consumption | Irrigation systems
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