Economic and Environmental Implications of Phosphorus Control at North Bosque River Wastewater Treatment Plants Keith Keplinger, Alex Tanter, and James Houser TR0312 July 2003 Economic and Environmental Implications of Phosphorus Controls Acknowledgments The authors wish to thank a number of individuals for making this research possible. Data on wastewater treatment plant parameters and sewer use and rates for the City of Stephenville were made available by Danny Johnson and Mark Kaiser, City of Stephenville, and Johnie Davis, OMI, Inc. Information on sewer use and rates for other communities located along the North Bosque River was supplied by various municipal personnel from those communities. Larry Beran, TIAER, initiated the project while Ron Jones, TIAER, was instrumental in securing a working relationship with the City of Stephenville. Edward Osei, TIAER, assisted with calculus solutions, while Larry Hauck, TIAER, provided overall direction and review of this report. The research upon which this report is based was financed by the U.S. Environmental Protection Agency, Office of Policy Development, cooperating agreement number CR 826807-01-1. For more information about this document or any other TIAER document, e-mail [email protected]. Authors Keith Keplinger, research economist, TIAER, [email protected] Alex Tanter, research associate, TIAER, [email protected] James Houser, research scientist, TIAER, [email protected] EI7.01.02 ii Economic and Environmental Implications of Phosphorus Controls Abstract Phosphorus (P) control at wastewater treatment plants (WWTPs) in the United States has been practiced since at least the 1970s, when effluent limits were placed on WWTPs in the Great Lakes region and in Vermont in order to reverse eutrophication of the Great Lakes and Lake Champlain, respectively. The rise to prominence of total maximum daily loads (TMDLs) in the 1990s has led to the identification of numerous water bodies where P has been identified as the leading cause of impairment, thereby giving new impetus to P control at WWTPs throughout the United States. TMDLs were issued for 2 segments of the North Bosque River in 2001, specified goals of a 50 percent reduction in soluble reactive phosphorus (SRP) loads and a 47 percent reduction in SRP concentrations for the entire North Bosque River and expectations of 50 percent load reductions for both point and nonpoint sources. One control action considered was the implementation of phosphorus (P) controls at six North Bosque wastewater treatment plants (WWTPs) designed to meet ending effluent standards of 1 mg/L total P (TP). This report assesses the economic and environmental implications of meeting these standards utilizing aluminum sulfate (alum) to precipitate P. Populations of North Bosque communities and corresponding sizes of their WWTPs vary considerably. Stephenville’s population is around 15,000, while the populations of the other 5 communities range from 360 to 3,500. Phosphorus removal was estimated to cost $5.13/person annually for the Stephenville plant, while it ranged from $13 to $124 per person annually at the other WWTPs, the great disparity, due mainly to high capital costs incurred, at the smaller WWTPs in relation to their small populations. The cost per pound of P removal is also considerably lower at the Stephenville WWTP versus the other plants: estimated to be $14 for the Stephenville plant but ranging from $36 to $269 for the smaller plants. The great disparity in unit costs suggests that P control obligations (or credits) could be traded among the six North Bosque WWTPs to their mutual advantage. The optimal trading scenario was determined to be one in which the control obligations of the three smallest WWTPs are transferred to the Stephenville plant while the three small WWTPs are allowed to operate without P control. This trading scenario results in estimated savings of $152,000 annually for the four trading WWTPs. Moreover, annual per person costs decline for all four trading plants, and dramatically for the three small WWTPs when we assume that pounds of TP are traded at Stephenville’s average cost of removal. For the small town of Irdell, estimated costs for P removal decline from $124/person annually without trading to $5.58 /person annually with trading. iii Economic and Environmental Implications of Phosphorus Controls iv Contents Background . 1 Historical Perspective . 2 Current Status of Phosphorus Control. 4 United States . 4 Europe . 5 Texas. 7 Survey of Phosphorus Control Costs . 8 Discussion . 11 North Bosque Community and WWTP Parameters . 12 Cost of P Removal at North Bosque WWTPs . 16 Operation and Maintenance (O&M) Costs. 17 Capital Costs . 19 Affordability . 20 Effectiveness Measures. 24 Basis for Effectiveness Measures . 24 Analysis . 26 Cost-Effectiveness . 29 Trading Implications. 30 Trades Between Stephenville and One Other North Bosque WWTP. 31 Trades Between Stephenville and Multiple Smaller WWTPs . 32 Conclusions . 37 Addendum. 37 References . 39 Appendix A Texas Regulation Impacting Phosphorus Control . 41 30 TAC Chapter 311 Watershed Rules . 41 TCEQ’s Antidegradation Policy . 41 The 75%-90% Rule . 42 Violation of Permit Effluent Limits. 42 Appendix B Derivation of Adjusted Effluent Phosphorus Concentrations . 45 Appendix C Chemistry of Phosphorus Removal by Alum Addition. 47 Chemistry of Alum and Phosphorus . 47 Determining Alum Dose for a Specific Wastestream. 49 References. 49 Appendix D Derivation of Concentration-Mile Effectiveness Measure . 51 v Economic and Environmental Implications of Phosphorus Controls vi Tables Table 1 Count by County of Number of WWTPs Having TP Limits in Their Permits . 9 Table 2 Average WWTP Phosphorus Control Cost Comparison . 12 Table 3 Wastewater Treatment Plant and Community Data for North Bosque River . 13 Table 4 North Bosque Community Monthly Sewer Rate Schedules. 15 Table 5 Estimation of Alum Expense of North Bosque Communities, 1 mg/L TP Effluent Limit. 18 Table 6 Annual Expense (Medium Estimate) for Phosphorus Removal at North Bosque River WWTPs . 20 Table 7 Cost and Affordability of Phosphorus Controls for North Bosque River Communities . 21 Table 8 Phosphorus Control Effectiveness for North Bosque River Communities . 27 Table 9 Median Flows, TP Loads, and TP Concentrations for North Bosque River and WWTPs . 27 Table 10 Cost-Effectiveness of Phosphorus Removal at North Bosque River WWTPs . 30 Table 11 Additional P Removal at Stephenville WWTP Equivalent to Meeting 1 mg/L . 31 Table 12 Effect on Stephenville WWTP of Trades with Iredell, Valley Mills, and Hico WWTPs. 33 Table 13 Comparison of Optimal Trading Scenario with No Trading Scenario, North Bosque River WWTPs. 36 Table 14 Analysis of TCEQ’s TMDL Load Allocations . 38 vii Economic and Environmental Implications of Phosphorus Controls viii Figures Figure 1 The locations of industrial and municipal WWTPs having phosphorus limits. 4 Figure 2 Implementation of phosphorus effluent limits by year, 1970 to 1997 . 5 Figure 3 Map of classification of European waters . 6 Figure 4 Map of Texas highlighting those counties with TP in their WWTP’s permits. 8 Figure 5 Per household cost of North Bosque River TMDL phosphorus control limits ($/month). 23 Figure 6 Per capita cost of North Bosque River TMDL phosphorus control limits ($/year) . 24 ix Economic and Environmental Implications of Phosphorus Controls x Economic and Environmental Implications of Phosphorus Control at North Bosque River Wastewater Treatment Plants Background The North Bosque River, located in North Central Texas, flows through 6 small communities ranging in population from 500 to 15,000, before draining into Lake Waco, a drinking water source for approximately 200,000 people located in and around the City of Waco. The headwater area of the North Bosque River basin is located in the state’s top dairy production region. Wastewater treatment plants in the communities along the North Bosque River also provide a significant portion of watershed phosphorus loads and contribute disproportionately to in-stream concentrations. Elevated levels of soluble phosphorus in lakes and streams can lead to accelerated eutrophication, a condition characterized by excessive algal growth and associated effects such as fish kills and unpleasant taste and odor. Sporadic algal blooms and associated taste and odor problems in drinking water from Lake Waco have been a longtime concern for the City of Waco and have focused attention on the North Bosque River as a possible source of impairment.1 Since 1992, when the Texas Commission on Environmental Quality (TCEQ) first compiled 303(d) lists, the North Bosque River has been included on the state’s impaired waters list. In the 1998 list as well as former lists, the TCEQ found the North Bosque River impaired under narrative water quality criteria related to excessive aquatic plant growth2 and TMDLs for two North Bosque River stream segments were initiated (TNRCC,3 2001). In-stream bioassays conducted in 1998 provided strong evidence that phosphorus was the limiting nutrient for algal growth under most conditions. Loading studies revealed that diary waste application fields (WAFs) and municipal wastewater treatment plants (WWTPs) were the major controllable sources of phosphorus (TNRCC, 2001). Additional research indicated that soluble phosphorus, measured as soluble reactive phosphorus, was statistically better correlated to algal levels than total phosphorus. 1 Lake.