Impacts Of Wastewater On Health Of People Exposed Biology Essay

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There is a broad range of pathogenic microorganisms including bacteria, viruses, helminths and protozoa present in wastewater. These pathogens are capable of causing severe illness or death. When a person becomes infected it actually depends on a number of additional factors, each of which adds to or diminishes the actual risk of infection. These several factors are important for determining the relative health risk during wastewater use. Many people who are exposed will not develop any symptoms, and the majority of persons who are affected are likely to suffer only short-term, mild to moderate gastroenteritis without long-term health effects. The impact of exposure to raw wastewater can severely affect the farm workers and families. The main outcomes are diarrheal disease and parasitic infections.

Bacteria. A wide range of pathogenic bacteria capable of causing human illness are found in human sewage. Diarrhea is the most prevalent type of infection, with cholera the worst form. Typhoid, paratyphoid, shigellosis and other Salmonella type diseases are also caused by bacterial pathogens.

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Viruses. There are numerous viruses that may infect humans and are passed in the faeces. The main groups of pathogenic excreted viruses are particularly important: adenoviruses, enteroviruses (including polioviruses), hepatitis A virus, reoviruses and diarrhoea-causing viruses (especially rotavirus). Most of the viruses affect the digestive system, i.e., enteric viruses including the hepatitis A virus and viral gastroenteritis. Hepatitis A is caused by the Hepatitis A virus (HAV) that is transmitted primarily by ingestion. The virus must be present in sufficient quantities to cause infection. Infection occurs after an incubation phase of three to four weeks. Hepatitis A is often mild, but can be severe or even critical in some cases. The symptoms are fever, headache, nausea and pain in the abdomen, dark urine and jaundice. People can spread the disease to others in the instant period before they become ill and while they are ill. Recovery from Hepatitis A can be slow and require several weeks or months of increased rest. The disease can be more severe in older patients. Other specific human pathogenic viruses such as C Polio, Coxsackie viruses and Norwalk viruses which are present in canal and near shore water can cause serious health problems to human.

Protozoa. Many types of protozoa can infect humans and cause diarrhoea and dysentery. Infective forms of these protozoa are often passed as cysts in the faeces and humans are infected when they ingest them. The most likely widespread species of pathogenic protozoa found in sewage and surface water are: Giardia lamblia, Balantidium coli and Entamoeba histolytica. The symptoms are diarrhea, stomach cramps, nausea and sometimes fever. Symptoms may last for only a few days or can last for months or years. Many people, especially children, have no symptoms.

Helminths. There are many species of parasitic worms or helminthes which are endemic in many areas and that have human hosts. Some can cause serious illnesses and the ones that pass eggs or larval forms in the excreta are of significance in taking into consideration of wastewater use. Most helminths do not multiply within the human host, a factor of great importance in considerate their transmission, the ways they cause disease and the effects that environmental change will have on their control. Often the developmental stages (life cycles) through which they pass before reinfecting humans are very complex. Those that have soil, water or plant life as one of their transitional hosts are very important in any system where wastewater is used directly or indirectly. The helminths are classified in two major division: the roundworms (intestinal nematodes- Ascaris, Trichuris, hookworm and Taenia ) and worms that are flat in cross section. The flatworm, in turn, may be divided into two groups: the tapeworms which form chains of helminths "segments" and the flukes which have a single, flat, unsegmented body. Most of the roundworms that infect humans and also the schistosome flukes have separate sexes. The result is that transmission depends upon infection with both male and female worms and upon meeting, mating and egg production within the human body. Leptospirosis is caused by the parasitic worm Leptospira icterohaemorrhegiae and is transmitted from water and damp earth. The initial septicemia phase lasts for 4-7 days and causes acute headache, chills, fever, severe muscle aching, anorexia, nausea and vomiting. The immune phase, characterized by aseptic meningitis, follows a 24-72 hour asymptomatic period. About 10-15% of patients present with Weil's disease, jaundice, hemorrhage and renal damage.

TABLE 4: Effectiveness of enteric pathogens to cause infections through wastewater irrigation related to their epidemiological characteristics

Enteric pathogens

Persistence in environment

Minimum infective dose

Immunity

Concurrent routes of infection

Latency/soil development stage

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Viruses

Medium

Low

Long

Mainly home contact and food or water

No

Bacteria

Short/Medium

Medium/High

Short/Medium

Mainly home contact and food or water

No

Protozoa

Short

Low/Medium

None/Little

Mainly home contact and food or water

No

Helminths

Long

Low

None/Little

Mainly soil contact outside home and food

Yes

Source: Shuval et al. (1986b).