Wastewater can come from a variety of sources like homes, businesses, industries, runoff from roads, lawns and fields and is treated by municipal wastewater treatment facilities (Product, cornell). The solid material that remains after the treatment of wastewater is known as sludge (charac, cornell). Sludge can be employed in many different ways, it can be used as a soil additive or growing medium, sent to a composting facility, incinerated or landfilled (Char, cornell).
Biosolids are derived primarily from a combination of primary, secondary, and tertiary sewage sludges. Biosolids do not contain the coarse grit and screenings removed from raw wastewater during preliminary treatment steps or ash generated from incineration of sewage…show more content… These various routes or pathways of contact can result in either acute or chronic disease if the exposure is high enough. For pathogens, the primary concern is acute diseases of a short-term duration (i.e., gastroenteritis or flu-like symptoms), while for the various potential chemical contaminants, risks are derived from chronic exposure via ingestion.
Pathogens that may be present in biosolids applied to land pose a disease risk only if there are routes of exposure that deliver an infective dose. The principal means of exposure is through ingestion or inhalation. Absorption through the skin is considered to be a minor route of exposure unless a field worker suffers a cut or other puncture to the skin and is exposed. The degree of harm caused by bacterial toxins varies with the mode of entry into the body.
It seems there is a correlation between the amount of biosolids applied and frequency of contamination. A 1984 study showed that 22.4mg/ha applied to Sassafras sandy loam soil was the upper limit to ensure that groundwater was not contaminated (Higgins, 1984). Doses below 22.4mg/ha of land are acceptable for the provision of nutrients to plants, while anything above diminished the water quality to below American federal standards (Higgens, 1984). Heavy metals and coliforms remained low