The impact of wastewater pollutants on the environment before treatment

Clean, safe water is vital to communities, ecosystems, human health, and industrial and commercial operations. But what is wastewater and how do we treat it? In this article, we will discuss the types of wastewater, the effect of wastewater pollutants and the different processes for treating these types of polluted water.

How is wastewater formed?

Wastewater refers to any water that has been used for industrial, commercial or domestic use. Therefore, wastewater is generated by activities such as washing, bathing, rainwater runoff, and manufacturing. Before this water can be used again, it must be cleaned and free of contaminants.

The three categories of wastewater include:

• Municipal sewerage: This comes from the daily use of water in homes or commercial businesses. This wastewater comes from toilets, sinks, and showers.
• Industrial wastewater: This wastewater is the residual water from manufacturing processes that occur in the pharmaceutical, textile, food and beverage industries, to name a few.
• Storm sewage: Storm sewage is water runoff that occurs during and after rainfall. This water becomes contaminated with dirt and other debris.

Depending on what the water is used for and the materials it comes into contact with, some wastewater is easier to treat than others.

Why do we treat wastewater?

If wastewater is left untreated, human health and the environment will be at risk. Untreated water carries bacteria and diseases, affecting drinking water, wildlife habitat, and activities such as swimming, boating, and fishing. Without treated wastewater, every interaction with water can be dangerous. Wastewater treatments allow us to run taps, drink water, or enjoy a day at the beach without questioning our safety.

Treating wastewater also enables it to be reused in some cases, putting less strain on company resources. Treated water can be used for agricultural or landscaping purposes, dust control, toilet flushing, or as process water in mills and refineries, for example.

Effect of wastewater pollutants

The impact of wastewater pollutants extends in many directions, human health is at risk as well as other species and ecosystems. From minor inconveniences like beach closures to larger concerns like restricting drinking water consumption, harmful pollutants can have devastating effects on the environment.

Examples of harmful effects of untreated wastewater include:

• Enforced restrictions: Viruses, bacteria, and diseases contaminate the water, leading to restrictions on drinking water, shellfish consumption, and human entertainment such as swimming in lakes or boating.
• Nutrient over-fertilization: When water contains too many nutrients such as nitrogen and phosphorus, toxic over-fertilization can occur, which changes habitat and can cause declines in some species.
• Increased minerals: Untreated water contains higher levels of arsenic, cadmium, chromium, lead and mercury which can be toxic to a variety of species.
• Survival of Fish and Aquatic Species: Debris and decaying organic matter remaining in the water monopolizes the oxygen in the water, making it impossible for fish and other aquatic species to survive.
• Health Risks: In addition to excess minerals and nutrients, wastewater can also contain personal care products or pharmaceutical substances that pose a threat to aquatic life, wildlife, and human health.
• Contaminated crops: Crops watered with untreated wastewater can become contaminated and unsafe for consumption.

Primary, secondary and tertiary wastewater treatment

The impact of untreated wastewater pollutants highlights the importance of wastewater treatment. There are three main stages of wastewater treatment – primary, secondary, and tertiary. Most plants will also add a fourth step known as pretreatment. We would love to receive your inquiry for more information.

Primary processing

During this optional stage, processes such as filtration are used to remove any large particles or solids from the water. Large bar screens will remove things like leaves, tree limbs, and plastic. While neutralizing tanks filter out smaller particles like sand, grit, dirt, and even coffee grounds.

Chemical methods can also be used during the pretreatment process. Some plants may use coagulation and flocculation to change the pH of the water to promote solid waste forming larger clumps for easier removal.

Some pre-treatments will also address the removal of grease and fat. However, this can vary depending on the wastewater plant, with some choosing to process this filtrate at the pre-treatment stage.

Primary treatment uses physical and gravitational processes to filter solids. The wastewater will remain in the primary clarifiers for an extended period as debris and remaining solids settle out. Mechanical abrasive equipment can help speed up the removal of solid contaminants. If grease and fats have not been removed previously, they will be removed from the water surface during this stage of treatment.

Secondary processing

After wastewater is treated by physical removal, bacterial processes occur during the secondary treatment stage. Microorganisms will be used to break down the impurities further. There are a few different treatment options that can be used during this stage, including:

Anoxic Treatment: Denitrification of wastewater occurs during anoxic treatment processes that break down nitrogen molecules and release oxygen.
Anaerobic Treatment: For wastewater containing high levels of biodegradable solids, anaerobic treatment will be used. During this treatment, the wastewater is stored in covered digestion lagoons where bacteria break down the organic waste.
Aerobic treatment: During aerobic treatment of wastewater, organic pollutants are converted into safer end products such as carbon dioxide, water, and microorganisms. Unlike anaerobic and anoxic treatments, this process requires aeration to provide oxygen to feed the microorganisms that consume the waste within the wastewater.

Tertiary treatment

Tertiary treatment is an optional step that puts wastewater through an additional filtration and disinfection process. Some common forms of cleansing during the tertiary treatment phase include:

Chlorination
Purification
Ion exchange
Ozone therapy
Ultraviolet disinfection