What Is Sewage? Understanding Its Impact on Water Quality

Every time you flush a toilet, wash your hands, or run the dishwasher, you create wastewater. But where does it all go? Once it leaves your home, this used water, known as sewage, begins a journey that can have a profound impact on the environment and public health. This article will define sewage, explore how it affects our water quality, and explain how you can protect the water within your home for total peace of mind.

What Is Sewage?

Sewage, also called domestic or municipal wastewater, is the used water produced by a community of people. It’s the collective discharge from homes, businesses, and public facilities that is transported through a network of pipes known as a sewer system [1].

While sewage is approximately 99% water, the remaining 1% contains a complex and hazardous mix of contaminants. The primary components of sewage include:

• Human waste (feces and urine)

• Food scraps from sinks and dishwashers

• Soaps, detergents, and cleaning chemicals

• Oils, grease, and fats

• Microplastics and other solids

This mixture of biological and chemical waste makes untreated sewage a serious threat to water quality and safety.

How Does Sewage Contaminate Water Sources?

In an ideal world, all sewage would be safely collected and thoroughly treated. In reality, multiple failure points allow raw or partially treated sewage to pollute natural water sources like rivers, lakes, oceans, and groundwater.

• Infrastructure Failures: Many sewer systems are aging and overburdened. Leaks in pipes can release raw sewage into the ground, where it can seep into groundwater. During heavy rain, combined sewer systems can become overwhelmed, intentionally overflowing to discharge a mix of stormwater and untreated sewage into local waterways to prevent backups into homes and streets.

• Untreated Discharge: A significant amount of wastewater enters the environment without proper treatment. According to The Nature Conservancy, as much as 80% of the world's wastewater flows back into the ecosystem without being treated or reused [2].

• Contaminated Runoff: As rain flows over roads, lawns, and industrial sites, it picks up a toxic brew of pollutants like oil, pesticides, and chemicals [3]. This runoff can overwhelm sewer systems and carry contaminants into the same water bodies that may be sources for drinking water.

The Impacts of Sewage on Water Quality and Health

When sewage pollutes a water source, it introduces a cocktail of contaminants that can cause severe damage to ecosystems and pose direct threats to human health.

Environmental Damage

The high concentration of nutrients like nitrogen and phosphorus in sewage acts as a fertilizer for algae, triggering a process called eutrophication. This leads to massive, harmful algal blooms that block sunlight and consume oxygen in the water as they decompose. This creates oxygen-depleted "dead zones" where fish and other aquatic life cannot survive. This type of pollution is particularly devastating to sensitive ecosystems like coral reefs and coastal wetlands, leading to widespread ecosystem destruction [4].

Human Health Risks

The most immediate danger of sewage-contaminated water is its threat to human health. Sewage is a breeding ground for pathogens—disease-causing microorganisms that can cause serious illness. These include:

• Bacteria: E. coli and Salmonella can cause severe gastrointestinal distress.

• Viruses: Hepatitis A and norovirus can lead to liver inflammation and stomach illness.

• Parasites: Giardia and Cryptosporidium are microscopic parasites that cause diarrheal disease and can be resistant to chlorine disinfection.

Beyond microbes, sewage can introduce a stew of chemical contaminants. Pharmaceuticals, heavy metals, nitrates, and "contaminants of emerging concern" like PFAS (per- and polyfluoroalkyl substances) can all contaminate drinking water sources and pose significant long-term health risks [5].

What Is Sewage Treatment?

To mitigate these risks, communities rely on wastewater treatment plants. These facilities use a series of physical, biological, and chemical processes to remove solids, organic matter, and many pathogens before discharging the treated water back into the environment.

However, these systems have limitations. Treatment plants are not designed to remove all modern chemical contaminants, and their effectiveness can be compromised by aging infrastructure or storm-related overflows. Most importantly, treatment ends at the plant. Water can travel through miles of pipes to reach your home, creating opportunities to pick up new contaminants along the way.

How to Protect Your Home's Water Supply

Given the risks of sewage contamination and the limits of municipal treatment, the only way to guarantee your water’s safety is to install a final barrier of protection in your home. Taking control of your home's water quality is a proactive step for your family's health. At Discount Filter Store, we provide the tools you need to ensure the water you drink, cook with, and bathe in is truly clean.

Whole House Filtration Systems

For comprehensive, whole-home protection, a whole house filtration system treats all water at the point it enters your home. This means every faucet and appliance—from the kitchen sink to the shower to the washing machine—receives filtered water. These systems often start with a sediment filter, like the Culligan CP5-BBS-D, to remove larger particles like rust and dirt, which protects your plumbing and extends the life of more advanced filters. Explore our selection of whole house water filters to find a solution tailored to your home's needs.

Point-of-Use Water Filters

If your primary concern is high-purity drinking and cooking water, point-of-use filters are a highly effective and targeted choice. These systems treat water at a single tap, using multi-stage filtration to remove a vast array of contaminants.

• Undersink Filters: Powerful and discreet undersink water filters, like the 3M Aqua-Pure system, are a popular choice. They keep the system out of sight while delivering purified water from a dedicated faucet, making them ideal for reducing lead, VOCs, and chlorine taste.

• Countertop & Refrigerator Filters: Many other types of water filters are available to fit your specific needs and budget, offering convenience and targeted filtration right where you need it most.

Specialized Water Treatment

For specific water quality issues, you may need a more specialized approach. If a water test reveals high levels of hardness (minerals), iron, or particular chemical contaminants like PFAS, dedicated water treatment solutions are available. Some advanced carbon block filters, for instance, are specifically designed to reduce emerging contaminants that standard filters might miss, giving you an extra layer of targeted protection.

Your Final Defense Against Contaminants

Sewage is the wastewater from our communities, and its potential to contaminate our water sources is a constant and serious concern. While municipal treatment is a crucial first line of defense, it is not foolproof. The risks of contamination from aging infrastructure, system overflows, and chemicals that pass through treatment are real.

By understanding these risks, you can take decisive action. A home water filtration system acts as your final, reliable line of defense, removing contaminants and giving you complete control over the quality and safety of the water your family relies on every single day.

Frequently Asked Questions

What is sewage and what does it contain?

Sewage -- also called domestic or municipal wastewater -- is the used water produced by homes, businesses, and public facilities and transported through a sewer network. While approximately 99% of sewage is water, the remaining 1% contains a hazardous mix of human waste, food scraps, soaps and detergents, oils and grease, microplastics, pharmaceuticals, heavy metals, and chemicals. This combination of biological and chemical contaminants makes untreated sewage a serious threat to water quality and public health.

How does sewage contaminate drinking water sources?

Sewage contaminates water sources through several pathways. Aging or damaged sewer pipes can leak raw sewage into surrounding soil, where it seeps into groundwater. During heavy rainfall, combined sewer systems can overflow and discharge mixtures of stormwater and untreated sewage directly into rivers and lakes. Contaminated runoff from roads, lawns, and industrial sites picks up pollutants and can overwhelm sewer systems, carrying those contaminants into the same water bodies used for drinking water supply. According to The Nature Conservancy, as much as 80% of the world's wastewater enters the ecosystem without proper treatment.

What pathogens are found in sewage-contaminated water?

Sewage-contaminated water can harbor multiple categories of disease-causing microorganisms. Bacteria including E. coli and Salmonella cause severe gastrointestinal illness. Viruses including Hepatitis A and norovirus can cause liver inflammation and severe stomach illness. Parasites including Giardia and Cryptosporidium cause diarrheal disease and are particularly concerning because they are resistant to standard chlorine disinfection at normal treatment concentrations, requiring filtration for reliable removal.

Does municipal water treatment remove all contaminants from sewage?

No. Wastewater treatment plants use physical, biological, and chemical processes to remove solids, organic matter, and many pathogens -- but they are not designed to remove all modern chemical contaminants. Pharmaceuticals, PFAS (forever chemicals), certain heavy metals, and other emerging contaminants can pass through treatment and remain in the treated effluent that is discharged back into water bodies used as drinking water sources. Additionally, treatment plant effectiveness can be compromised by aging infrastructure and storm-related overflows that bypass normal processing.

What is eutrophication and how does sewage cause it?

Eutrophication is the process by which excessive nutrients -- primarily nitrogen and phosphorus from sewage -- enter a water body and act as fertilizer for algae. The resulting algal blooms block sunlight, and as the algae decompose they consume dissolved oxygen in the water, creating oxygen-depleted dead zones where fish and aquatic life cannot survive. Eutrophication is particularly destructive to sensitive ecosystems like coral reefs and coastal wetlands and is one of the primary environmental consequences of widespread sewage pollution.

What chemicals in sewage pose long-term health risks?

Beyond biological pathogens, sewage can introduce a range of chemical contaminants into drinking water sources. These include pharmaceuticals and personal care products that are not fully removed by wastewater treatment, heavy metals from industrial discharge, nitrates from human waste and agricultural runoff, and PFAS (per- and polyfluoroalkyl substances) -- the so-called forever chemicals that accumulate in the environment and human tissue. These chemical contaminants can persist in water supplies and may pose long-term health risks at elevated concentrations.

How can I protect my home's drinking water from sewage-related contaminants?

A home water filtration system provides the final barrier of protection between the municipal water supply and your family. A whole-house point-of-entry system treats all water entering the home, protecting every faucet and appliance from sediment, rust, and chemical contaminants. For the most thorough protection of drinking and cooking water specifically, an under-sink multi-stage filter or reverse osmosis system at the kitchen tap provides targeted reduction of a broad range of contaminants including chlorine, lead, VOCs, cysts, and emerging contaminants like PFAS. Testing your water first identifies which specific contaminants are present and guides the right filtration selection.

Does boiling water remove sewage-related contaminants?

Boiling water effectively kills biological pathogens -- bacteria, viruses, and protozoan cysts -- making it a useful emergency measure. However, boiling does not remove chemical contaminants including pharmaceuticals, heavy metals, nitrates, PFAS, or other dissolved chemicals that may be present in sewage-affected water. Boiling also slightly concentrates dissolved solids as water evaporates. For comprehensive protection against both biological and chemical contaminants, physical filtration -- particularly multi-stage carbon block filtration or reverse osmosis -- is the appropriate long-term solution.