The Minnesota State Legislature passed an act in 1885 to prevent the pollution of rivers and other water supply sources. For the next 60 years, the Minnesota Board of Health had responsibility for water pollution problems. By 1907, the State Board of Health realized that consumption of drinking water contaminated by raw sewage discharges posed a serious public health threat. Without any authority, the Board of Health attempted to pressure the Twin Cities communities to install wastewater treatment facilities. In 1917, the State Board of Health adopted regulations requiring towns to submit plans for sewers and wastewater treatment plants prior to construction. The Board also conducted water pollution surveys and made various recommendations for controlling pollution. Letters to the city councils of the Twin Cities urging action on controlling the discharge of raw sewage went unanswered in 1923 and 1925. At the request of the State Board of Health, the U.S. Public Health Service conducted the first water pollution survey of the Upper Mississippi River from the Twin Cities to Winona, Minnesota, in 1926.
During the 1920s, the Izaak Walton League, the Engineers Society of St. Paul, the Engineering Club of Minneapolis, and other private groups lobbied for immediate action on the problem of raw waste disposal into the river. In 1926 the Minneapolis Sanitary Commission was created to study "the condition of the river and the problems of sewage disposal" (MWCC, 1988). In 1927, when the Metropolitan Drainage Commission was formed, raw sewage was discharged through 84 outfalls over a network of 1,125 miles of sewers (MWCC, 1988). Maurice Robbins, a former deputy administrator of MWCC, remembering his experiences sampling the river during those years, stated that "It could get pretty awful down by the river. There were floating feces, dead fish and a terrible sewer smell" (MWCC, 1988).
In 1927, the State Board of Health was given the authority and the responsibility to administer and enforce all laws related to water pollution in Minnesota. The legislature directed the State Board of Health to form a Metropolitan Drainage Commission. The legislature, however, did not provide any substantial basis for managing waste disposal. In 1933, a decade after the Minnesota State Board of Health had begun to document the pollution problems of the Upper Mississippi River, the Minneapolis-St. Paul Sanitary District was finally created to oversee construction of the first pri mary wastewater treatment plant in the Twin Cities region. The primary treatment plant, located near Pig's Eye Lake in St. Paul, went online in 1938.
In 1945, the legislature passed the Water Pollution Control Act to establish the Water Pollution Control Commission for the regulation of the emerging problems of water pollution. The Minnesota Act, amended in 1951, 1959, and 1963, was regarded as one of the better state water pollution control acts in the United States (FWPCA, 1966). The main mission of the new Water Pollution Control Commission was to direct the construction of primary wastewater treatment plants for the smaller municipalities in the Twin Cities metropolitan area.
In 1967, the state legislature formed the Metropolitan Council as a regional coordination agency. In 1969, the Metropolitan Waste Control Commission (MWCC) was given the regional responsibility for wastewater collection and treatment systems for 33 plants within 200 political jurisdictions of the seven-county Twin Cities area. In 1967, the legislature also created the Minnesota Pollution Control Agency (MPCA) to replace the Water Pollution Control Commission. The new agency was soon given authority to regulate and enforce effluent limits for municipal and industrial treatment plants. The establishment of the U.S. Environmental Protection Agency in 1970 and the enactment of the 1972 Clean Water Act further strengthened the regulatory powers for requiring uniform effluent limits for wastewater dischargers. In July 1994, the MWCC and transit services were merged with the Metropolitan Council. The responsibility for operating municipal wastewater treatment plants was delegated to the Environmental Services Division of the Metropolitan Council (MCES).
Following the 1972 Clean Water Act, the MWCC, with federal (75 percent) and state (15 percent) funding assistance, spent more than $350 million to dramatically improve the technology of the Metro plant, upgrade other facilities, and build interceptor sewer systems (MWCC, 1988). During the 1970s and 1980s, MWCC phased out or upgraded old plants or constructed new plants for many of the suburban communities in the Twin Cities region. MCES now operates the Metro plant and eight other treatment plants in the Twin Cities area. The Metro plant and three other wastewater treatment plants discharge to the Upper Mississippi River; three plants discharge effluent to the Minnesota River; and the St. Croix River and the Vermilion River each receive effluent discharges from one municipal plant.
IMPACTS OF WASTEWATER TREATMENT Pollutant Loading and Water Quality Trends
During the 1960s and 1970s, effluent loading from the Metro plant accounted for more than three-quarters of the total point source load of BOD5 in the section of the Upper Mississippi River from the Twin Cities to the St. Croix River. Because this one waste-water treatment plant, the Metro plant, accounted for more than 75 percent of the total point source load, historical effluent data from the Metro plant can serve as an indicator to demonstrate the success of public investments to upgrade the plant in improving water quality in the Upper Mississippi River. Figures 12-8 through 12-11 present time-series trend data for population served, effluent flow, BOD5, total suspended solids (TSS), total Kjeldahl nitrogen (TKN), and ammonia-N concentrations for the Metro plant from 1940 to 2000 (Larson, 1999, 2001; Johnson and Aasen, 1989).
During the early 1960s, the Metro plant served 1.05 million people and discharged 158 mgd to the Upper Mississippi River. By 1997, the population served by Metro had grown to 1.7 million with a corresponding increase in the effluent discharge rate to 225 mgd (Figure 12-8). Since enactment of the Clean Water Act in 1972, effluent BOD5 loading from the Metro plant has been reduced greatly from the peak loading period of the mid-1960s. Before upgrading the Metro plant, effluent BOD5 loading peaked at about 330,000 lb/day in 1968. After upgrading to secondary in 1966, effluent loading dropped to 114,000 lb/day by 1970 and 77,000 lb/day in 1973. Since the 1980s, effluent loading of BOD5 has continued to decline as a result of additional upgrades (e.g., advanced secondary in 1984) and replacement, or abandonment, of 21 of the 33 suburban wastewater treatment plants that existed in 1969 when MWCC assumed responsibility for plant operations. BOD5 loading from Metro declined again to 40,000 lb/day by 1980 and to 27,000 lb/day by 1990. Over a 30-year period, upgrades and improvements to the Metro plant have reduced effluent BOD5 loading by 95 percent from the historical peak loading of 330,000 lb/day in 1968 to only 17,000 lb/day in 1998. Over the same period, the effluent concentration of BOD5 has been reduced from 184 mg/L in 1968 to 9.7 mg/L in 1998 (Figure 12-9).
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