Review of Phosphorus Control Measures in the United States and Their Effects on Water Quality By David W. Litke U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 99–4007 NATIONAL WATER-QUALITY ASSESSMENT PROGRAM Denver, Colorado 1999 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. For additional information write to: Copies of this report can be purchased from: NAWQA Nutrient Synthesis Chief U.S. Geological Survey U.S. Geological Survey Information Services Box 25046, Mail Stop 415 Box 25286 Denver Federal Center Federal Center Denver, CO 80225-0046 Denver, CO 80225 FOREWORD The mission of the U.S. Geological Survey • Describe how water quality is changing over time. (USGS) is to assess the quantity and quality of the • Improve understanding of the primary natural earth resources of the Nation and to provide informa­ and human factors that affect water-quality tion that will assist resource managers and policy- conditions. makers at Federal, State, and local levels in making This information will help support the development sound decisions. Assessment of water-quality and evaluation of management, regulatory, and conditions and trends is an important part of this monitoring decisions by other Federal, State, and local overall mission. agencies to protect, use, and enhance water resources. One of the greatest challenges faced by water- The goals of the NAWQA Program are being resources scientists is acquiring reliable information achieved through ongoing and proposed investigations that will guide the use and protection of the Nation’s of 59 of the Nation’s most important river basins and water resources. That challenge is being addressed by aquifer systems, which are referred to as study units. Federal, State, interstate, and local water-resource These study units are distributed throughout the agencies and by many academic institutions. These Nation and cover a diversity of hydrogeologic settings. organizations are collecting water-quality data for a More than two-thirds of the Nation’s freshwater use host of purposes that include: compliance with permits occurs within the 59 study units and more than two- and water-supply standards; development of remedia­ thirds of the people served by public water-supply tion plans for a specific contamination problem; systems live within their boundaries. operational decisions on industrial, wastewater, or National synthesis of data analysis, based on water-supply facilities; and research on factors that aggregation of comparable information obtained from affect water quality. An additional need for water- the study units, is a major component of the program. quality information is to provide a basis on which This effort focuses on selected water-quality topics regional and national policy decisions can be based. using nationally consistent information. Comparative Wise decisions must be based on sound information. studies will explain differences and similarities in As a society we need to know whether certain types observed water-quality conditions among study areas of water-quality problems are isolated or ubiquitous, and will identify changes and trends and their causes. whether there are significant differences in conditions The first topics addressed by the national synthesis are among regions, whether the conditions are changing pesticides, nutrients, volatile organic compounds, and over time, and why these conditions change from aquatic biology. Discussions on these and other water- place to place and over time. The information can be quality topics will be published in periodic summaries used to help determine the efficacy of existing water- of the quality of the Nation’s ground and surface water quality policies and to help analysts determine the as the information becomes available. need for, and likely consequences of, new policies. This report is an element of the comprehensive To address these needs, the Congress appropri­ body of information developed as part of the NAWQA ated funds in 1986 for the USGS to begin a pilot Program. The program depends heavily on the advice, program in seven project areas to develop and refine cooperation, and information from many Federal, the National Water-Quality Assessment (NAWQA) State, interstate, Tribal, and local agencies and the Program. In 1991, the USGS began full implementa­ public. The assistance and suggestions of all are tion of the program. The NAWQA Program builds greatly appreciated. upon an existing base of water-quality studies of the USGS, as well as those of other Federal, State, and local agencies. The objectives of the NAWQA Program are to: • Describe current water-quality conditions for a large part of the Nation’s freshwater streams, Robert M. Hirsch rivers, and aquifers. Chief Hydrologist FOREWORD III CONTENTS Foreword................................................................................................................................................................................ iii Abstract.................................................................................................................................................................................. 1 Introduction ........................................................................................................................................................................... 1 Purpose and Scope....................................................................................................................................................... 2 Acknowledgments ....................................................................................................................................................... 2 Phosphorus in the Environment............................................................................................................................................. 2 Phosphorus Sources and Sinks .................................................................................................................................... 3 Phosphorus and Eutrophication................................................................................................................................... 4 Phosphorus Control Measures............................................................................................................................................... 4 Phosphate Detergent Bans ........................................................................................................................................... 5 Effluent Phosphorus Limits ......................................................................................................................................... 8 Nonpoint-Source Controls on Phosphorus .................................................................................................................. 9 Effects of Phosphorus Control Strategies on Water Quality ................................................................................................. 11 Extent of Eutrophication.............................................................................................................................................. 11 Reductions in Phosphorus Concentrations and Loads................................................................................................. 12 Improvements in Eutrophic Conditions....................................................................................................................... 15 Use of National Water-Quality Assessment Program Data to Evaluate Effects of Phosphorus Controls............................. 17 Description of NAWQA Water-Quality Data .............................................................................................................. 17 NAWQA Findings ....................................................................................................................................................... 26 Summary................................................................................................................................................................................ 31 References ............................................................................................................................................................................. 32 FIGURES 1-2. Graphs showing: 1. Contributions to the environment of phosphorus from fertilizer and manure, 1940-95 .................................... 3 2. Consumption of phosphorus in detergent manufacturing and number of States with phosphate detergent bans, 1940-98..................................................................................................................................................... 5 3. Maps showing (A) States with phosphate detergent bans, and (B) number of wastewater-treatment plants with phosphorus limits by State.................................................................................................................................. 7 4-5. Graphs showing: 4. Number of wastewater-treatment plants in the United States, by treatment type .............................................. 8 5. Implementation of phosphorus effluent limits by year, 1970-97 ....................................................................... 10 6-9. Maps showing: 6. Percentage of total phosphorus concentrations