Nutrient Farming and Traditional Removal: an Economic Comparison
The purpose of this study was to assess the economic feasibility of using large-scale, restored wetlands to assist publicly owned treatment works (POTWs) in meeting the U.S. Environmental Protection Agency's (USEPA) recommended criteria for nutrients, specifically, total nitrogen (2.18 mg/l) and total phosphorous (0.076 mg/l). The assessment compares the cost of nutrient control by advanced wastewater treatment technology to that of wetland treatment technology. The comparison was based on several economic factors: annual operating costs, average costs, marginal costs, and present value.
To explore the economic relationship between wastewater and treatment wetlands and to quantify the magnitude of wetland area needed, a case study was developed using the seven water reclamation plants (WRPs) owned and operated by the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) and proposed treatment wetlands located adjacent to the Illinois River in the upper Illinois River watershed. Cost functions for both technologies were developed. Using these functions, the economic characteristics of the two technologies were compared assuming, first, that the USEPA's proposed nutrient criteria would be enacted as the enforceable water quality standard by the state regulator, and, second, that a less stringent standard would be established (3.0 mg/l TN and 1.0 mg/l TP). However, the USEPA's phosphorus criterion was modified due to the technical difficulty in achieving an effluent concentration of 0.076 mg/l TP. The more stringent phosphorous criterion was set at 0.5 mg/l TP for this comparison study.
The land requirements for a nutrient farm, while extensive, can be easily supplied within the 5,000,000 acres of flood prone land in the Illinois River. However, until large-scale nutrient farms are in existence and greater experience gained in their design and operation, there will be reluctance to use this technology. A series of demonstration projects should be established in various ecoregions to study the design, operation and economic efficiency of treatment wetlands. In addition to greatly improving water quality, nutrient farms can spur recreational development and reduce flood damage.
This title belongs to WERF Research Report Series
ISBN: 9781843397335 (Print)
ISBN: 9781780404394 (eBook)
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