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. To meet the future nutrient criteria, the physical facilities of the seven MWRDGC treatment plants must be upgraded to incorporate biological nutrient removal (BNR) technology. A detailed capital cost analysis for the addition of BNR treatment, specifically the 5-stage Bardenpho (with methanol addition), was performed by the MWRDGC for one of its larger WRPs, Calumet. The capital costs for the other plants were estimated using Calumet's cost formulas and prorated by the design flows. The operating and maintenance (O&M) costs were estimated to add approximately 50 per cent to those for the conventional treatment currently being employed by MWRDGC. The capital costs for upgrading the seven WRPs with the Bardenpho system has been estimated at USD1.6 billion with the total present value cost at USD2.5 billion. For the nutrient removal capability of treatment wetlands, or nutrient farms, the load variation of the Illinois River was considered, as well as the seasonal variation in wetland nutrient removal. The treatment wetlands require over 189,000 and 322,000 acres to meet the MWRDGC's nutrient removal requirements as dictated by the less stringent criteria and the modified USEPA criteria, respectively. Yet, despite this large land requirement, wetland-based nutrient removal was found to save the MWRDGC between 51 per cent and 63 per cent of the annual cost of advanced treatment. Since the maximum land requirement for wetland treatment was found to be for the coldest part of the year (January), both nitrogen and phosphorus were removed in greater quantities than needed during the warmer months, resulting in a surplus of nutrient removal capacity. If the surplus of nutrient credits produced in the wetlands, called "nutrient farms," were sold on a nutrient market to other emitters (e.g., publicly owned treatment works, automotive industry, agriculture, etc.), then the annual and present value savings would increase to 76 per cent and 78 per cent for the two sets of criteria. The average and marginal costs were determined to compare the two technologies. The cost of nutrient removal per ton for the wetlands is significantly less than WRP treatment technology. This difference reflects the overall economic efficiency of the two technologies. The load weighted marginal cost for the WRPs was calculated to be USD3,410/ton TN removed and USD16,000/ton TP removed. While the marginal cost for the wetland varied seasonally, the load weighted costs were USD1,930/ton TN and USD1830/ton TP. The difference in the marginal costs reflects the price differential between the two technologies. 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.