The effects of topically-applied municipal biosolids on seedling emergence and early seedling growth
Hahm, Joanna M.
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Biosolids are primarily an organic byproduct of anaerobically-digested municipal sewage sludge. Approximately 6.9 million dry tons of municipal biosolids were produced in 1998 in the United States (USEPA, 1999). Biosolids production is estimated to increase to 8.2 million dry tons by 2010 (USEPA, 1999). Congress prohibited disposal of biosolids in open waterways or in the ocean with the Marine Protection Research and Sanctuary Act of 1988. Alternatixe disposal methods include incineration, composting, landfilling, and land application. Beneficial disposal methods include land application and composting. Incineration and landfilling do not recycle biosolids. Composting of biosolids is expensive and energy-intensive (USEPA, 1999). Buming prior to landfilling can reduce the amount of space needed; however, incineration is also costly and energy intensive (USEPA, 1999). With increasing waste production and costs for incineration, other disposal methods are needed. Recycling of biosolids includes land application to agricultural areas, rangeland, forest, and disturbed areas such as mines and construction sites. Approximately 2.8 million dry tons of biosolids were land applied in 1998(USEPA, 1999). In addition, land application of biosolids is generally less expensive than other recycling methods (USEPA, 1999). Because they are rich in nitrogen, phosphorus, and other nutrients, biosolids can be applied to amend, improve, and maintain productive soil and plant growth (USEPA, 1999). Concerns associated with land application of biosolids include contamination of ground water and runoff water, heavy metal buildup, and unpleasant odors, all of which can be avoided with proper land management (USEPA, 1999). Technological advances in the waste management industry and increasing social awareness of associated environmental issues have resulted in improved biosolids quality, leading to a more valuable resource for recycling. EPA-approved production of biosolids requires treatment to reduce pathogens. The Texas Natural Resource Conservation Commission (TNRCC) regulates biosolids application rates in Texas. Regulations established by the EPA (40 CFR part 503), as well as by local health officials, ensure that biosolids recycling remains a safe and an integral part of waste management programs.