Sewage vs. Wastewater: The Difference Explained

Have you noticed an increase in your water or wastewater bills recently? If so, you’re not alone.

The average cost for people in 50 cities went up 3.6% in the past year. And these costs have been rising for the past eight years per Bluefield Research’s U.S. Municipal Water & Wastewater Utility Bill Index.

According to the Environmental Protection Agency, 34 billion gallons of wastewater gets processed every single day at water treatment plants in the U.S. And more gets processed by the 20 percent of American homes that treat their own wastewater themselves in their septic tanks.

Wastewater or raw sewage is rarely given much thought until a sewage spill makes the news. Nor can most explain the difference between the two.

So let’s break it down here.

What is the Difference Between Sewage and Wastewater?

Types of sewage consist of both blackwater and greywater from domestic/residential sources. Blackwater refers to water mixed with human waste that gets flushed down a toilet. This definition is not conclusive though because people use toilets to flush a lot more things than human waste (even if they shouldn’t).

Greywater refers to water used in dwellings or office buildings that have not come into contact with blackwater. Such as in sinks, showers, washing machines, dishwashers, etc. But even some sources of greywater will show traces of human excreta.

Wastewater is primarily water and enters the water treatment system from non-domestic sources. But depending on its source, it can present a wide range of pollutants and hazards. Such as wastewater from agriculture or oil and gas production, about which you can read more here.

Both wastewater and sewage must get treated before the water is safe enough for reuse.

How Are They Routed for Treatment?

If greywater has not been commingled with blackwater or other wastewater, it is possible to treat the greywater on-site. Then reuse it for other purposes. But it needs to get done following specific guidelines and re-used for very limited purposes.

Blackwater, greywater that has mixed with blackwater and all other wastewaters goes to water treatment plants to get processed. In areas that have newer water treatment systems, the different types of water may be directed to the water treatment facility via separate drainage pipes and can get processed differently.

But in other areas in the country (particularly in the northeast), all water including rainwater/storm runoff all gets sent to the water treatment plant in the same drainage pipe. Because of this, during major storms, the volume of water being processed can exceed the drainage pipe’s capacity causing sewage and wastewater to spill out into lakes or other areas provided for this purpose in emergency situations.

How Is Wastewater Processed?

Wastewater processed at a water treatment facility goes through several stages. The first step involves running the water through screens to capture big items like plastic bags and pieces of wood. Then the water enters sedimentation tanks where dirt, sand, and other grit get removed.

After that, more solids get removed. This gets accomplished by siphoning out biosolids solids that sink to the bottom and skimming off other waste that floats to the top.

The remaining liquid is then sent to get treated by bacterias that eat the organic waste in the wastewater turning it into sludge. The sludge is then processed in more settling tanks. Then run through filters to remove more solids before becoming recycled water that can be re-used.

The biosolids that got siphoned off get processed differently. They get put in enclosed tanks that allow bacteria and other microorganisms to eat and destroy the pathogens. The resulting nutrient-rich biosolids can then get used as agricultural soil amendments.

How Does Reclaimed Water Get Used After Processing?

Reclaimed wastewater could get used as drinking water, but it is generally not repurposed for that reason. Reclaimed wastewater is primarily put to other uses to conserve our drinking water.

One of the major ways reclaimed wastewater is used is for irrigation. Such as golf courses, plants along roadways, and public parks. And in agricultural applications from watering crops and grass for pastured animals. It’s also used to wash cars, for street cleaning, flushing toilets, and even making fake snow.

Keeping Items Out of Wastewater

There are things that people can do on a personal level to lower their negative impact on wastewater. Limiting what gets flushed down the toilet to only human waste is a good first step. Medications, needles, bandaids, cigarette butts, Q-tips, and contact lenses shouldn’t get flushed.

Being mindful of litter, picking up after our pets, and choosing environmentally friendly products for use in our landscapes can lower the amount of trash, fecal matter, and chemicals entering our storm drains and wastewater systems.

Think Water Conservation First, Water Treatment Second

Water treatment plants provide a solution for collecting and processing the water we use for reuse. But many water treatment infrastructures are outdated and taxed due to increased population.

There are a few easy ways to cut your water usage. Such as, take shorter showers, install low-flow toilets, and run your dishwasher/washing machines only when they are full.

Take Action Today to Lower Your Impact

Thinking about sewage and how to lower one’s impact on our community’s wastewater system is likely not often on many people’s minds. But we can all do our part by just taking a step or two. Cleaning of the septic tank at regular intervals is also very important. There are professionals you can hire for septic tank pump out.

Looking for more information about environmental topics? We’ve got them. Check out our site for more great articles.

About RJ Frometa

Head Honcho, Editor in Chief and writer here on VENTS. I don't like walking on the beach, but I love playing the guitar and geeking out about music. I am also a movie maniac and 6 hours sleeper.

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