A comprehensive guide to the potential risks in wastewater treatment plants

However, without wastewater treatment, the current concentration of pollutants from individuals and industries in many parts of the world would quickly render parts of the environment incompatible with life. While it is essential to reduce the amount of waste, proper waste treatment is essential. Therefore, awareness of these potential risks in wastewater treatment plants must be increased so that we understand the importance of proper design and installation of wastewater treatment plants. We must not overlook the importance of regular follow-up and maintenance. These risks can be avoided by dealing with an organization with long experience in the field of wastewater treatment. Such as the CareWater Foundation, which ensures the safety of workers and the longest life span of your plant.

Hazards and Prevention

The goal of wastewater treatment plants is to remove as many solid, liquid, and gaseous pollutants as possible within technically feasible and financially feasible constraints. There are a variety of different processes used to remove pollutants from wastewater including sedimentation, coagulation, flocculation, aeration, disinfection, filtration, and sludge treatment.

The specific risks associated with each process vary depending on the design of the treatment plant and the chemicals used in the various processes. However, hazards can be classified as physical, microbial, and chemical. The key to preventing or minimizing the harmful effects associated with working in wastewater treatment plants is to anticipate, identify, assess, and control hazards.

Physical risks that are potential risks in wastewater treatment plants

The Physical hazards include confined spaces and unintentional activation of machinery or equipment parts. Physical hazards vary with plant design. However, most wastewater treatment plants have confined spaces including underground or subterranean vaults with limited access, and manholes and settling tanks when they are emptied of liquid content during repairs. Mixing equipment, sludge compactors, pumps and mechanical devices used in a variety of processes in wastewater treatment plants can be harmful if they are inadvertently activated when a worker is maintaining them. Wet surfaces, which are often found in wastewater treatment plants, contribute to slip and fall hazards.

Confined Space Entry

This is one of the most common and dangerous hazards faced by wastewater treatment workers. However, a confined space is an area with limited means of entry and exit that is not designed for continuous residence and does not have adequate ventilation. Hazards occur when the confined space is associated with a lack of oxygen, or the presence of a toxic chemical or a submerged substance, such as water.

Low oxygen levels can be the result of a variety of conditions including the replacement of oxygen by another gas, such as methane or hydrogen sulfide, the consumption of oxygen by the decomposition of organic matter present in wastewater, or the leaching of oxygen molecules in the rusting process of some structures within the confined space. Since low oxygen levels in confined spaces cannot be detected by unaided human observation, it is extremely important to use an instrument that can determine the oxygen level before entering any confined space.

Toxic Gases

Lack of oxygen is not the only hazard in a confined space. Toxic gases can be present in a confined space at concentrations high enough to cause serious harm or even death, despite adequate oxygen levels. The effects of toxic chemicals encountered in confined spaces are discussed in more detail below. One of the most effective ways to control the risks associated with low oxygen levels (less than 19.5%) and toxic chemical-contaminated atmospheres is to thoroughly and adequately ventilate the confined space through mechanical ventilation before allowing anyone to enter. This is usually done using a flexible duct through which outside air is blown into the confined space. Care must be taken to ensure that fumes from the generator or fan motor are not blown into the confined space.

Wrong Timing Operation

Wastewater treatment plants often contain large pieces of machinery to move sludge or raw sewage from one location in the plant to another. When repairs are made to this type of equipment, the power to the entire machine must be disconnected. Furthermore, the switch to reactivate the equipment must be under the control of the person performing the repairs. This prevents another worker in the plant from inadvertently activating the equipment. This can result in disfigurement of body parts, such as fingers, arms, legs, and even death.

Movement in Dangerous Spaces

Wastewater treatment plants often contain large tanks and storage containers. People sometimes need to work over containers or walk through emptied pits that may contain a drop of 8 to 10 feet (2.5 to 3 m). Adequate fall protection and proper safety training for workers should be provided.

Microbial Hazards

Microbial hazards are primarily associated with the treatment of human and animal waste. Although bacteria are often added to alter the solids in wastewater, the risk to wastewater treatment workers comes primarily from exposure to microorganisms present in other human and animal waste. The results of exposure to microorganisms present in wastewater treatment plants for extended periods of time are often more subtle. However, these effects can also be serious and irreversible.

The three main classes of microbes involved are fungi, bacteria, and viruses. All of these agents can cause acute illness as well as chronic illness. Acute symptoms including respiratory distress, abdominal pain, and diarrhea have been reported in waste treatment workers. Chronic diseases, such as asthma and allergic inflammation, have traditionally been associated with exposure to high levels of airborne microbes, and more recently with microbial exposure during household waste treatment. Reports of significantly elevated concentrations of fungi and bacteria in waste treatment facilities, sludge dewatering, and composting are beginning to be published. Another source of airborne microbes is the aeration tanks used in many wastewater treatment plants.

In addition to inhalation, microbes can be transmitted through ingestion and through contact with unprotected skin. Personal hygiene, including hand washing before eating, smoking, and going to the bathroom, is important. Food, drink, eating utensils, cigarettes, and anything that can be placed in the mouth should be kept away from areas of potential microbial contamination.

Chemical Risks

Chemical hazards in waste treatment plants can be immediate and deadly, as well as long-term. A variety of chemicals are used in the coagulation, flocculation, disinfection, and sludge treatment process. The chemical chosen is determined by the contaminants or pollutants in the raw wastewater; some industrial wastes require more specific chemical treatment. In general, the primary hazards from chemicals used in coagulation and flocculation processes are skin irritation and eye injury from direct contact.

Solutions with a pH of less than 3 or greater than 9

Effluents are often disinfected using liquid or gaseous chlorine. The use of liquid chlorine can cause eye injury if splashed into the eyes. Ozone and ultraviolet light are also used to disinfect effluents.

One way to monitor the effectiveness of wastewater treatment is to measure the amount of organic matter remaining in the effluent after treatment is complete. This can be done by determining the amount of oxygen required to biodegrade the organic matter in one liter of effluent over a day. This is referred to as the 5-day biological oxygen demand (BOD5).

Chemical hazards in wastewater treatment plants arise from the decomposition of organic matter, which results in the production of hydrogen sulfide and methane. From toxic wastes dumped down sewer lines and from pollutants produced by the processes carried out by the workers themselves.

Hydrogen sulfide

Also known as sewer gas. Even if the olfactory system can detect hydrogen sulfide, it is unable to accurately judge its concentration in the atmosphere. Hydrogen sulfide biochemically interferes with the electron transfer mechanism and prevents the use of oxygen at the molecular level. The result is suffocation and eventual death due to a lack of oxygen in the brain stem cells that control the rate of breathing. At these low levels, hydrogen sulfide can be a respiratory irritant, accompanied by headaches and leading to conjunctivitis. Hydrogen sulfide is produced when organic matter decomposes, and industrially, during the production of paper, the tanning of leather, and the production of heavy water for nuclear reactors.

Methane

Another gas produced by the decomposition of organic matter. In addition to displacing oxygen, methane is explosive. Levels that lead to an explosion can be reached by the presence of a spark or source of ignition.

Factories handling industrial waste must have a thorough knowledge of the chemicals used in each of the industrial facilities. That benefits from their services and a working relationship with the management of those factories so that they can be informed immediately of any changes in the processes and the contents of the waste. The discharge of solvents, fuels, and any other material into sewage systems poses a risk to the treatment workers not only because of the toxicity of the material discharged but also because the dumping is unexpected.

When any industrial process, such as welding or spray painting, is carried out in a confined space, special care must be taken to provide adequate ventilation to prevent the risk of explosion. And also to remove the toxic substances resulting from the process. When a process carried out in a confined space produces a toxic atmosphere. It is often necessary to provide the worker with a respirator because of the ventilation of the confined space. It may not guarantee that the concentration of the toxic chemical can be kept below the permissible exposure limit. The selection and installation of the appropriate respirator falls within the scope of industrial hygiene practice.

Use of gaseous chlorine to disinfect liquid waste from the factory to avoid potential hazards in wastewater treatment plants

Gaseous chlorine comes in a variety of containers weighing from 70 kg to approximately 1 ton. Chlorine gas is highly irritating to the lungs, even at low levels of a few parts per million. Inhalation of higher concentrations of chlorine can cause inflammation of the air sacs in the lungs. It produces respiratory distress syndrome in adults, which has a 50% mortality rate. When a wastewater treatment plant uses large amounts of chlorine (1 ton or more), the risk is not only to the plant workers but also to the surrounding community. Unfortunately, plants that use larger amounts of chlorine are often located in large, densely populated urban centers. Other methods of disinfecting wastewater from a wastewater treatment plant are available. These include ozone treatment, the use of liquid hypochlorite solutions, and ultraviolet irradiation.

Other things not to do that are potential hazards in wastewater treatment plants

When installing a wastewater treatment plant, make sure not to do any of the following:

• Do not expose the tank to shock or Sharp edges.
• Adding tank neck extensions, and do not build a brick drain above the tank neck (as this increases the depth of the tank burial). Extending the tank neck under any circumstances is not recommended.
• Installing the tank deeper than the depth permitted by the prepared neck.
• Installing in congested areas without proper backfill design.
• Sit the tank so that it will be subject to excessive ground pressure (e.g. sloping ground) or applied loads such as those generated by vehicle traffic.
• Filling an unsupported tank.
• Filling an empty tank.