Where Does All the Wastewater Go?


Here’s what happens to wastewater and what we can do at home to protect aquatic systems

Wastewater management is a crucial aspect of modern infrastructure, ensuring the safe and responsible treatment of water that is used in our homes, businesses, and industries. Ever wondered where all the wastewater goes once it disappears down the drain? 

The journey begins at the collection system, consisting of a vast network of pipes and underground infrastructure. Wastewater flows through these pipes and ultimately reaches a centralized treatment facility. The specific pathways may vary depending on the location, as well as the type of wastewater, which can include domestic, industrial, and stormwater runoff. Municipalities and utility companies invest significant resources in maintaining and expanding this collection infrastructure to accommodate growing populations.

Once the wastewater arrives at a sewage plant it undergoes several treatment processes to remove pollutants so that it can be safely discharged without harming the environment or posing a human health risk.

It’s important to note that wastewater management practices can vary at the state and local levels. Regulations and infrastructure can differ, resulting in variations in treatment processes, discharge standards, and wastewater reuse practices. The goal, however, remains consistent across the country: to protect public health, safeguard the environment, and promote sustainable water management practices.

Treatment Processes

Because different treatments are required to remove different pollutants, several different wastewater treatment technologies are incorporated into a wastewater treatment system.

Activated Sludge Treatment

The following steps are used in activated sludge treatment, the biological treatment most commonly used to treat domestic wastewater.

  • Preliminary treatment. In this stage, large objects and debris are removed using screens and grit chambers to protect the treatment equipment from damage.
  • Primary treatment. In the primary stage of treatment, wastewater is screened to remove additional debris and grease before being allowed to stand so that larger particles can settle out (called primary settling). The sludge is pumped out of the bottom of the tank, floating debris and grease are skimmed off the surface, and the remaining wastewater is subjected to secondary treatment.
  • Secondary treatment. In the second stage, that of activated sludge and aeration, bacteria break down organic matter present in the wastewater. Activation involves adding bacteria to the wastewater to activate the process, and aeration enables the bacteria to thrive. During this process, which occurs in an aeration tank, the bacteria consume the organic pollutants, turning them into water, nitrogen, and material for the production of new cells.
  • The wastewater is then pumped into a clarifying tank in which the activated sludge containing the bacteria settles to the bottom of the tank (called secondary settling) before being returned to the aeration tank so that the next batch of wastewater coming through the system can be activated. 
  • Tertiary treatment. Primary and secondary treatments remove many pathogens and other contaminants that pose a risk when discharged into the environment. The effluent, which is now 90% treated, then typically undergoes tertiary treatments like precipitation, and microfiltration or ultrafiltration to remove any remaining nutrients, particles, or undesirable substances. Then, disinfection with chlorine or ultraviolet light takes place to kill any remaining pathogens and ensure that the water is safe 

After being treated at a plant to remove pollutants, the wastewater can be safely discharged into local waterways, where it is diluted by fresh water from further upstream. The former wastewater can now be used to maintain aquatic systems and habitats; used as irrigation water, industrial water, or drinking water; and in other applications.

Combined Sewer Overflow (CSO) Management. In areas with combined sewer systems, excessive stormwater runoff during heavy rainfall events can overwhelm the capacity of the treatment plants. To prevent backups and overflows, these systems may include overflow points called combined sewer overflows (CSOs). During intense rain events, a mixture of stormwater and untreated wastewater may be discharged directly into nearby water bodies. However, efforts are being made to minimize and manage CSOs through the use of storage tanks, diversion systems, and stormwater management practices.

On-site Systems and Septic Tanks. In rural or remote areas where centralized sewer systems are not available, on-site systems, such as septic tanks, are used to treat and dispose of wastewater. These systems collect wastewater from individual households or small communities and treat it on-site through a combination of settling, microbial digestion, and soil filtration.

How to Help Protect the Quality of River Water

Wastewater treatment has limits.

If and when we send hazardous materials down the drain, then, we may be contributing to pollution of freshwater systems and coastal waters. So, we need to be careful about what we allow to enter the sewer system through our toilets and drains.

Avoid pouring hazardous chemicals, such as paints, solvents, motor oil, pesticides, and cleaning agents, down the drain. These substances can be toxic to aquatic life and disrupt the natural balance of water ecosystems. Instead, look for proper disposal methods in your community, such as designated drop-off locations or recycling centers for hazardous waste.

Flushing unused or expired medications down the toilet or drain can introduce harmful substances into water bodies. These pharmaceuticals can negatively affect aquatic organisms and potentially contaminate drinking water supplies. Many pharmacies and healthcare facilities offer safe disposal programs for unused medications, ensuring they are disposed of properly.

If you have a septic system, ensure it is well-maintained and regularly inspected. Follow recommended guidelines for septic system care, including regular pumping, proper disposal of household chemicals, and being mindful of what goes down the drain. This will help prevent pollution and protect groundwater and nearby water bodies.

Another way to help protect the quality of river water is through water conservation. Be mindful of water usage and repair leaky faucets and pipes to prevent unnecessary water loss. Installing water-efficient fixtures and appliances, such as low-flow toilets and showerheads, can also help conserve water. Consider supporting conservation organizations and initiatives by volunteering for river cleanup events, restoration projects, and educational campaigns in order to contribute to the preservation and improvement of our precious river ecosystems.

By adopting these practices and raising awareness about the importance of responsible waste disposal, we can all play a role in safeguarding aquatic systems. Every small action counts when it comes to protecting the health and vitality of our water resources for future generations.

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