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 (char, 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 landfills (Char, Cornell).
Bossily are derived primarily from a combination of primary, secondary, and tertiary sewage sludge. Bossily do not contain the coarse grit and screenings moved from raw wastewater during preliminary treatment steps or ash generated from incineration of sewage sludge. Another type of bossily may be derived from domestic seepage, the solid or liquid material removed from septic systems, portable toilets, and other systems that receive only domestic sewage.
However, since all sludge and bobsleds contain potentially harmful contaminants, beneficial uses must be balanced against acceptable risks for human health and environmental Impacts (Beneficial, Cornell) The terms sludge and bloodies are In some cases universally Interchangeable, while In some cases there are minor discrepancies between the two definitions. Thus for the sake of this paper we will treat the two definitions as equal and interchangeable.
While In most cases, the composition of the received wastewater Is uncontrollable, the makeup of the resultant sludge must be known in order to determine its suitability for various uses (Prod, Cornell). When evaluating the composition of sludge, its physical and chemical properties must be considered. Questions that should be asked are: How much water and solid matter does it contain?
How many different metals and nutrients does It have and how much of each? What potentially toxic organic chemicals are contained in the sludge? What pathogen reduction process was used? (Char, Cornell). Typically, sludge contains 1-7% solid material and 93-99% water. (char, Cornell). Proper sludge treatment and management are necessary to ensure public and environmental health and safety (char, Cornell).
The pH of sludge ranges from 4 to 12, and this value can have an affect on the movement of heavy metals, the corrosiveness of the sludge and the survival of the pathogens It contains Many people, including agricultural scientists and environmentalists are concerned hat land application of sludge will result in an increase of pathogenic bacteria, viruses, parasites, chemicals and metals In drinking water reservoirs, aquifers and the food chain (beneficial, Cornell).
While the potential risks may seem to be high In the applications of sludge, the degree of risk depends directly on the initial sludge quality, the way sludge are processed and how the sludge are managed during General Overview: Modes of Transport from Field to Human There are numerous pathways by which humans can come into contact with bossily or bossily-derived contaminants.
These include direct contact or accidental ingestion, inhalation of bossily-derived aerosols or dust, ingestion of water (surface waters and groundwater), and consumption of crops grown in bossily-amended soils or of animals that have fed on crops grown in such soils. In addition, a variety of vectors can transmit pathogens (flies, mosquito, fleas, rodents, or other animals than can transport the disease either mechanically or by biological processes) from bossily to humans or intermediate hosts. In order to cause infection, pathogens must gain entrance to the body of the host.
Microorganisms cannot penetrate normal, undamaged skin but can pass through mucous membranes, which thus form the most common portals of entry (Siderite, 1988). These occur at the alimentary, respiratory and igniter-urinary tracts (Silversmith, 1998). Additional routes of entry are via abrasions or small openings in the skin where local infections such as boils may occur, via wounds from which infection may spread throughout the body by means if the circulatory system, or via animal or insect bites (Siderite, 1988).
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. . , 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 bossily 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 bossily applied and frequency of contamination. A 1984 study showed that 22. OMG/ha applied to Sassafras sandy loam soil was the upper limit to ensure that groundwater was not contaminated (Higgins, 1984). Doses below 22. MGM/ha of land are acceptable for the provision of nutrients to plants, while anything above diminished the water quality to below American federal standards (Higgins, 1984). Heavy metals and chloroforms remained low throughout the experiment, which is also backed by research from health Canada showing that heavy metals and chloroforms detected in groundwater are t concentrations lower than ones of concern (Healthcare, 2000? ). When bossily are applied to the land, pathogens that may be present in the indirectly by vectors.
Virus transport from soil to plants has been suggested as a possible route of exposure, but no definitive research has shown this to occur (Straus et al. 1993). Planting restrictions are applied on bossily-amended fields to ensure that contamination of plants is minimized until die-off of any residual pathogens have occurred and risks are reduced. Potential bacterial and viral pathogens carried by animals that could be contracted y humans include tuberculosis, salmonella, listener, comparable, retrovirus, and taxonomists.
More than 50 animals can carry Circumscription. Rats and mice in particular are vectors for serious limitlessness example, rodents may drink treated wastewater containing Salmonella from a local waterway, and the Salmonella could be transferred to chickens that eat rodent droppings incidentally, which then transfer the pathogen to humans through eggs (Kinder et al. 1996). Inanimate objects (such as crops, soil, equipment, and the shoes or clothing of workers) may be intimidated with infectious organisms that can be transported from sites of bossily application.
Restricting the harvesting of crops until natural die-off of remaining pathogens occurs, combined with good sanitary practices and management practices for on-farm workers and bossily transporters, has played a key role in minimizing the transport of pathogens offset. Vectors are agents capable of transmitting a pathogen from one organism to another. Vectors can achieve this mechanically (simple transport by animals or insects such as flies) or biologically by playing a role in the life cycle of the pathogen (rodents).
The rotational vectors are insects, particularly flies, but other vectors can include farm workers or bossily workers who become ill and infect their families. Grazing animals can also be vectors. Parasite eggs from domestic animals have been demonstrated to have the ability to be transported by flies to grazing land and infecting livestock (Eastern Research Group 1992). Control of vectors has been an important element in the development of the Part 503 regulations (U. S. Environmental Protection Agency 1995, Eastern Research Group 1992), which include treatment and management practices that prevent conditions that attract vectors.
Worker protection, good sanitation, and documentation of medical histories and sickness in workers’ families can play an important role in preventing disease transmission should it occur. Aerial dispersion of bacterial diseases such as tuberculosis, electrolysis, and legionnaires’ disease have been documented (Saab et al. 1982, al-Galahad and al- Aziza 1988, Bigness 1999, and Resin et al. 1997). Monitoring studies are limited, but studies indicate there is less risk associated with bossily land application (unless it is a liquid spray operation) than with spray irrigation of wastewater which has not en disinfected.
Studies of wastewater aerosol formation over a period of years showed little impact on air quality (Barren and Kabuki’s 1980). Studies in Texas showed that bacterial levels were highest around the sludge mixing and loading facilities where agitation occurred and showed that normal heterocyclic bacteria caliphates (Pillar et al. 1996) Pathogenic Clamatorial were detected where physical agitation occurred. Measurements of bacteria in the air downwind of bossily processing or application sites is limited (Pillar et al. 996) and the data collected shows the presence of high embers of bacteria when there is mixing or dispersal (like a manure spreader), but the risk of an infectious dose of a pathogenic bacterial species in an outdoor area appears to be negligible (Pillar et al. 1996). There have only been a few reported cases of bossily-related illnesses as a result of airborne transmittal of pathogens See espadrilles discussions in this chapter). Most of these incidences are related to Nor in confined spaces such as sludge dewatering facilities, composting facilities Clark et al. 983, Milliner et al. 1980), or processing facilities and not related to the rainspout, unloading or application of bossily. En bossily are applied to the land surface, the particulates in bossily typically combine with soil material to form a filter mat so that primarily, soluble and colloidal particles enter the soil. Larger organisms such as protozoan’s and helpline eggs are retained in the upper soil layers, while virus particles and small bacteria can be transported through the soil to groundwater.
The mechanisms of pathogen removal In soil are primarily filtration (affects bacteria) and adsorption (for viruses). Coarse sands and soils with gravel lenses are those most conducive to pathogen rainspout to groundwater (Koala 1985, Wooziness et al. 1998). Most other soils, particularly fingered soils, are effective at removing both bacteria and viruses. Large amounts of water must be filtered to obtain a measurable amount of viruses in groundwater. Generally, this means that it would be extremely hard to obtain an Infectious dose due to the large amounts of water that would have to be consumed.