Effect on Surface Water Chemistry of Long-Term Application of Biosolids for Land Reclamation in Illinois

To evaluate the impacts of the long-term application of biosolids on surface water chemistry, NO3−, NH4+, PO43−, Cd, Cu, and Hg were monitored in surface water for 31 years from 1972 to 2002 in a 6000 hectare watershed at Fulton County, Illinois, where the Metropolitan Water Reclamation District of Greater Chicago launched an initiative to restore the productivity of strip-mined land using biosolids. Most of the fields in the north, south, and east areas of the watershed received biosolids at cumulative loading rates from 500 to 1500 Mg ha-1 during the past 31 years. However, the west area received only supernatant from 1977 to 1979, and occasionally in the 1980s, with a cumulative biosolids loading rate of less than 20 dry Mg ha−1. Subsequently, we considered the north, south, and east areas of the watershed as the biosolids block, and the west area as the control block. Biosolids were injected into mine spoil fields as liquid fertilizer from 1972 to 1985, incorporated as dewatered cake from liquid holding basins from 1980 to 1996, and incorporated as air dried/dewatered solids from 1987 to 2002. Fields in the east, north, and south areas that received biosolids were bermed to reduce runoff. Their surface water was drained to runoff retention basins to reduce suspended solids before being released to reservoirs and streams. Solids accumulated from sediments in the retention basins were distributed back to adjacent fields. Sampling of surface water was conducted monthly in the 1970s, and three times per year in the 1980s and 1990s. The water samples were collected from 15 reservoirs and streams receiving drainage from the control area of the watershed, and 14 reservoirs and streams associated with the biosolids-amended area of the watershed for the analysis of NO3−-N (including NO2−-N), NH4+-N, PO43−-P, and total Cd, Cu and Hg. Compared to the control (0.97 mg L−1), surface water NO3−-N in the biosolids block (2.27 mg L−1) was consistently higher. However, it was still below the Illinois Pollution Control Board (IPCB's) limit of 10 mg L−1 for food processing water. Ammonia-N in surface water (0.21 mg L−1 for control and 0.25 mg L−1 for biosolids) was considerably lower than the acute limit of 4.71 mg L−1 set by IPCB for General Use water. Short-term (one-decade) application of biosolids lowered the water PO43−, however, long-term (over two decades) application could elevate water PO43−. Application of biosolids tended to decrease the concentrations of Cd, Cu and Hg in surface water. Our results indicate that application of biosolids for land reclamation at high loading rates from 1972 to 2002 had only a minor impact on surface water quality at the District's Fulton County site.