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The clean water act and biosolids: A 45-Year chronological review of biosolids land application research in Colorado.

J. Ippolito,K. Barbarick

Published 2022 in Journal of Environmental Quality

ABSTRACT

The 1972 U.S. Clean Water Act (CWA) set forth the generation of biosolids. In Colorado, biosolids land application research began in 1976 and continues today. Pastureland research suggested that sewage effluent could effectively be land-applied to benefit above-ground plant growth and to polish water prior to reaching receiving waters. Forest wildfire affected ecosystems can also benefit from biosolids applications; application rates of up to 80 Mg ha-1 can lead to greater plant establishment, soil microbial activity, nutrient turnover, and reduced nutrient and heavy metal concentrations in runoff below livestock and US EPA drinking water standards. Long-term (24 y) observations in oil shale mined lands showed that biosolids (up to 224 Mg ha-1 ) can have a positive effect on microbial-mediated nutrient cycling and, in turn, above-ground plant community structure. Biosolids applications of up to 40 Mg ha-1 in high elevation shrubland ecosystems, dominated by Mo-containing shale deposits, can aid in reducing imbalances between Mo and Cu in soils and plants; excessive plant Mo, when consumed by ruminants, can lead to molybdenosis. Biosolids and lime applications (both at 224 Mg ha-1 ) have been shown to improve long term reclamation success on acid-generating, heavy metal containing fluvial mine tailings. Thirty years of grazing land research, focused on soil and above-ground plant benefits, illustrate that soil health and plant productivity can be improved to the greatest extent at biosolids application rates close to 10 Mg ha-1 . Finally, forty years of dryland agroecosystem research has: a) helped identify biosolids N fertilizer equivalency (∼8 kg N Mg-1 ) and thus dryland winter wheat application rates (e.g., 4.5 to 6.7 dry Mg ha-1 ); b) first year mineralization rates range from 25 to 32%; c) dispute the "time bomb" theory by showing that plant metal uptake follows an exponential rise to a maximum; d) showcase economic return to producers via increased wheat grain protein content; e) suggest that biosolids-borne proteins and their degradation products are labile C and N sources; f) led to long-term tracking of micronutrients and heavy metals in soils and plants - soil concentrations will not lead to groundwater degradation, and plants are safe for human consumption; and g) biosolids provide Zn, helping to overcome soil deficiencies and enhancing Zn biofortification in wheat grain. This latter point being important as ∼ 2 billion people globally suffer from Zn deficiencies. Forty-five years of research in Colorado has proven that biosolids can enhance environmental quality, improve soil health, and produce healthy food products. This article is protected by copyright. All rights reserved.

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