Wastewater Consists Of A Mixture Of Domestic Sewage

Published Date: 02 Nov 2017

Wastewater consists of a mixture of domestic sewage which includes waste from sinks, household toilets, showers, washing machines. It also consists of industrial effluent and occasional run-off of surface water and ground water which has infiltrated into the sewers.

Wastewater is 99.99% water, and 0.01 % of dissolved or suspended solid matter [6].

1.1 Wastewater Biology

Untreted sewage may contain various disease organisms including bacteria, viruses, fungus, worms and protozoa [7] [8] [9]. (McCunney 273; Weldon, et al 821; Schlosser, et al 261).

Airborne bacteria concentrations are usually very high where sewage is agitated, such as near incoming wastewater inlets and sludge treatment areas (Laitinen, et al 1055). Airborne bacteria have been found in "clean" areas such as control rooms, even though at much lower levels compare to other areas of a WWTP [10] (Laitinen, et al 1057).

The primary route of exposure to these microorganisms is the "fecal-oral route" [7] (McCunney 273). This commonly occurs during eating, drinking or smoking or by touching the face with contaminated hands or gloves [11] (HSE 2). Inhalation of aerosols containing microorganisms is not so common yet an essential method of entry. Skin absorption is improbable unless the skin has been previously damaged by cuts, burns, blisters, or puncture wounds [7] [10] (Laitinen, et al 1055; McCunney 273). The mucous membranes such as in the eyes and nose may also provide a pathway of entry for certain microorganisms.

1.2 Studies of health problems in sewage workers

1.2.1 Biological Hazards in wastewater

Biological hazards are organic substances which can affect the human body. Biological hazards include bacteria, viruses and parasites.

Biological hazards are common hazard found in the wastewater treatment plant.

Organism

Signs & Symptoms

Bacteria

Salmonella

Nausea, headache, diarrhea and vomiting; almost always with a fever.

Tetanus (lockjaw)

Muscular stiffness in jaw, neck. Sweating, fever, difficulty swallowing.

Shigella

Cramps, diarrhea, fever, bloody stool, nausea, vomiting.

Leptospirosis (Weil’s Disease)

Intestinal problems, liver and kidney disease, jaundice.

E. coli

Diarrhea, vomiting, little or no fever, blood often seen in stool.

Tulareisis

Chills, fever, swollen lymph nodes, stomach pain, diarrhea, vomiting.

Yersinia

Diarrhea, fever, abdominal pain that resembles appendicitis.

Viruses

Hepatitis A

Fever, abdominal pain, nausea, jaundice, dark-colored urine.

Hepatitis B

Nausea, vomiting, loss of appetite, jaundice, joint pain.

Hepatitis C

Develops slowly, loss of appetite, stomach pain, nausea and vomiting. Jaundice is less common.

HIV

Destroys immune system, prone to opportunistic infections.

Polio

Fever, headache, nausea, muscle pain and stiffness, paralysis.

Parasites

Entameoeba histolytica (amebiasis)

Mild nausea, loose stool, abdominal tenderness. In severe cases can spread throughout the body and attack other organs, especially the liver.

Giardia lamblia

Cramps, weight loss, loose/greasy stool, bloating. Fever is rare.

Sources: AFSCME; Utah Dept. of Health.

Table 1.1: Showing the biological organisms in wastewater [12]

1.2.2 Hepatitis A

Hepatitis A is a liver disease which is caused by the hepatitis A virus. The virus is primarily spread when an uninfected (and unvaccinated) person ingests food or water that is contaminated with the feces of an infected person. The disease is closely associated poor personal hygiene.

It can cause devastating symptoms and acute liver failure, which is associated with high mortality [13].

A study was carried out to determine whether or not occupational exposure to sewage is associated with a higher seroprevalence of hepatitis A virus. In order to carry out the study about 600 sewage workers in Singapore were tested. The study showed that sewage workers have an increased occupational risk of acquiring HAV infection and should be protected by active immunization [5].

1.2.3 HIV

The risk for transmission of human immunodeficiency virus (HIV) from wastewater is considered unlikely, [14] although the virus seems to survive for a limited period in wastewater. Studies have demonstrated that nucleic acids of HIV-1 virus has been detected in some municipal wastewater samples from USA but this does not necessarily equate with the presence of infectious viral particles [15].

1.2.4 Bacteria

1.2.4.1 Helicobacter pylori

Several studies have shown that there is an increased risk for gastric cancer among sewage workers. During the last decade, the bacterium Helicobacter pylori has

appeared as one important risk factor for gastric cancer and is now considered a class I carcinogen by the International Agency for Research on Cancer [16].

1.2.4.2 Legionella

Legionella pneumophilia is usually spread by water aerosols, which cause either

pneumonia or a nonpneumonic disease (Pontiac fever). An investigation of American

sewage workers found no increased risk for infection with L pneumophilia

But recently five cases of Pontiac fever have been reported in workers exposed to

aerosols from a sewage plant in the food industry treating only organic industrial

waste. L pneumophilia of the same serogroup as in the infected workers was

cultured from the sludge [17].

1.2.5 Parasites

There has been a significant positive association between the finding of protozoa in feces from sewage workers and the duration of exposure to sewage has been reported, [18] and the prevalence of infestation with intestinal parasites decreases by adopting good hygienic practices [8]. An increased risk for giardiasis has been reported workers in France and Germany [8] [18] [19] [20] [21]. An increased incidence of Entamoeba histiolytica has been reported in sewage exposed workers in France, but not in Germany [18] [19].

1.2.6 Skin and mucous membranes

Many sewage workers have reported skin disorders [22] [23] and inflammation of the eyes [22] [24]. After an accidental exposure to dust containing sludge, several incinerator workers at a sewage treatment plant in Toronto, Canada were affected by irritant contact dermatitis [25].

1.2.7 Nervous system

Studies have also reveal that central nervous system symptoms such as headache, unusual tiredness, and concentration difficulties have been found among the sewage workers. In addition, an increased risk for non-specific work related gastrointestinal symptoms was found among the sewage workers [26].

1.2.8 Respiratory symptoms

Several studies have been done to study the respiratory function of sewage workers, with all of them reporting that respiratory symptoms such as chronic bronchitis and toxic pneumonitis are common among this group of workers [26]. The respiratory function studies also discovered abnormal respiratory functions in those sewage workers. These symptoms may arise due to exposure to endotoxins and airborne bacteria by way of bio aerosols. Zuskin et al. reported that sewage workers are exposed to different occupational noxious agents, which may lead to the development of chronic lung function changes [27].

1.2.9 Chemical Hazard

Wastewater contains a great amount of industrial contaminants which may harm those people who come into contact with sewage.

According to the Pennsylvania DEP, methane and carbon dioxide are the most common chemical byproducts of wastewater. If found in a small enclosed space with a quantity of sewage, these gases can crowd out oxygen and asphyxiate anyone trapped in the area [4].

Sewage workers are also exposed to gases such as hydrogen disulfide, methane, ammonia and carbon monoxide. Watt et al. carried out a study on 26 sewer workers exposed to smell and he found that 53.8% developed sub-acute symptoms including sore throat, cough, chest tightness, breathlessness, thirst, sweating and irritability. Severity of symptoms seemed to be dose related [28].

1.2.10 Physical Hazard

Confined spaces, machines parts, slips and falls are all physical hazards which can affect sewage workers. If a sewage worker encountered physical hazards the outcome can be irreversible, serious and even fatal. Physical hazards differ with the design of the treatment plant. However, most sewage treatment plants have confined spaces which include underground or below grade vaults with limited access, manholes and the sedimentation tanks when they have been emptied of liquid content during, for example, repairs. Mixing equipment, sludge rakes, pumps and mechanical devices used for a variety of operations in sewage treatment plants can injure, and even kill, if they are accidentally activated when a worker is servicing them. Wet surfaces, often encountered in sewage treatment plants, promote slipping and falling hazards [29].

1.2.11 MUSCULOSKELETAL DISORDERS

Osteoarthritic problems and intervertebral disc herniation are the common spinal disorders reported that has been reported among sewage workers.[30] An investigation was carried out by Friedrich on 255 sewage workers to determine the occurrence of spinal troubles (i.e., neck, upper back and lower back pain [LBP]). He reported that the 12-month prevalence rates of neck, upper back and LBP were 52.4%, 54.8% and 72.8%, respectively." The occurrence of spinal troubles increased with age. Work disability during the preceding 12 months due to LBP was significantly positively associated with age, disability, weekly duration of stooping and lifting 5 years previously and higher abnormal illness–behavior scores [31].

1.3 Health & Safety act

OSHA says the employer should give the worker:

Training and education about the hazards present at the wastewater treatment plant.

A place onsite with clean water for washing hands

A place to wash and clean up after work.

The right PPE, such as gloves, goggles, a face shield, water-resistant suit, or respirator, depending on the job type.

Clean areas for eating and smoking.

Cleaning facilities or services for clothing and equipment. (If clothing is badly soiled, change out of it. Keep equipment clean to limit your exposures to the disease-causing agents [32].

1.4 Safety of workers

In wastewater treatment plants, engineering controls and work practices are the best ways to protect workers from exposures to disease. When engineering controls are not possible, the use personal protective equipment (PPE) is encouraged [32].

1.4.1 Engineering controls

Engineering controls, is one which removes or reduce the hazard either by initial engineering design specifications or by applying methods such as substitution, isolation or ventilation.

1.4.2 Administrative control

Administrative controls that minimize employees’ exposure s by scheduling reduced work times in contaminant areas, good work practices and employee training. Appropriate training includes hazard recognition and work practices specific to the employees’ job that can help reduce exposures. Raterman, Fundamentals of Industrial hygiene 5th Edition; 2002

1.4.3 Personal Protective Equipment (PPE)

"Personal Protective Equipment" means any equipment intended to be worn or held by an employee and which protects him against risk to his health or safety, and includes:

(a) Any addition or accessory designed to meet that objective; and

(b) Clothing affording protection against the weather;

(Occupational Safety and Health act 2005)

Workers handling sewage should be provided with proper PPE. The following PPE is recommended for workers handing sewage:

Goggles: to protect eyes from splashes of human waste or sewage.

Protective face mask or splash-proof face shield: to protect nose and mouth from splashes of human waste or sewage.

Liquid-repellent coveralls: to keep human waste or sewage off clothing.

Waterproof gloves: to prevent exposure to sewage.

Rubber boots: to prevent exposure to sewage.

1.4.2 Training for Workers

All workers who handle sewage should receive training. The training should include information on basic hygiene practices; use and disposal of personal protective equipment; proper handling of sewage; signs and symptoms of the different types of diseases present; and ways in which diseases can be transmitted. Workers must also be advised to immediately seek medical attention if displaying any signs or symptoms such as vomiting, stomach cramps and watery diarrhea.

1.4.3 Vaccination for Workers

Vaccination recommendations for workers exposed to sewage or human waste should be developed in consultation with local health authorities. Tetanus vaccinations should be up to date, with consideration also given to the need for polio, typhoid fever, Hepatitis A and Hepatitis B vaccinations [33].

1.4.4 Hygiene Practices

1.4.4.1 Hygiene

Hygiene is the association of human sciences, professions, technologies and disciplines for the purpose of protecting the health of individuals and community from any harmful exposure (Goldner, 2009). The science of hygiene comprises of the disciplines of, microbiology, parasitology, immunology, toxicology, entomology, pharmacology, and environmental health including geography, topography, and engineering, all with a view to limit, inhibit, or block sources and characteristics that deter from normal living.

1.4.4.2 Hygiene at Work

Protecting workers against disease, ill-health or impairment due to chemical, microbiological and physical health hazards, not only during, but after work, has been the traditional goal of occupational hygiene. Prevention of occupational diseases emanating from the workplace due to toxic exposures has been one of the primary roles. (Pityn, 2007)

A well planed and properly executed sanitation program for the place of work is very important, both for the workers and the employers as it is thorough those determining action that a company can attain better productivity, a safer work place and ensuring

1.4.5 Medical surveillance

According to Occupational Safety and Health act health surveillance should be provided to employee who is exposed to potentially hazardous substance. The medical surveillance should be free of charge and should be carried out at intervals of not less than once every 6 months or at shorter intervals as the medical practitioner may advise. (Occupational Safety and Health act 2005).

1.5 The role of Waste Water Management Authority (WMA)

The WMA manages the public sewerage system consisting of 515 km of sewer network, 19 treatment plants and 50 pumping stations, the main treatment plants being at St-Martin, Grand-Baie, Baie-du-Tombeau, and Montagne Jacquot.

The Wastewater Management Authority (WMA) has been established as a body corporate under the Wastewater Management Authority Act to be responsible for all matters relating to the collection, treatment and disposal of wastewater. It operates as an autonomous organization under the aegis of the Ministry of Renewable Energy and Public Utilities.

The WMA thus plays an important role in the protection of the environment and in ensuring the country's sustainable development by the provision of appropriate water pollution standards, wastewater control systems and management services to the entire population of Mauritius [34].