You’ve just watched the water go down the drain in the kitchen sink, or down the hole in the toilet. Where does it go from there?
The sewage — or “wastewater” — goes through your private portion of the sewer line (on your property) to the WSSC lines, and connects to a WSSC sewer main.
WSSC has nearly 5,400 miles of sewer pipe, which lead to 6 wastewater treatment plants.
It is up to all of us — WSSC, businesses, homes,and other sewer customers — to make sure that debris does not enter the system and clog the sewer lines, either on your property or on public property. Sewer clogs and overflows, anywhere, are a mess and may harm the environment.
After the wastewater leaves your home and travels through the sewer mains, the first stop is at a pumping station where it goes through a grinder or screen at the treatment facility. Large pieces of rags, toys, trash, sticks, dead animals, money and other debris are removed.
The next stop on the wastewater journey is the grit removal chamber, where sand and gravel settle out in the chamber or tank. This gritty material, and the objects from the first stop, are sent to a landfill. The sewage flows into “clarifiers,” which are big tanks where sludge settles to the bottom and scum floats to the top. The sludge and scum are diverted to eventual land use application, and the water moves along to other tanks.
The next step is BNR, or Biological Nutrient Removal. A population of micro-organisms live in this set of tanks, and the organisms feed on the organics in the wastewater. Throughout the process, nutrients (nitrogen and phosphorous) are also removed from the water.
Nitrogen and phosphorous are removed from wastewater because they promote algae growth if wastewater is discharged without treatment to a natural body of water. Algae reduces the amount of oxygen in the water which, in turn, harms fish and plants.
The water reaches the point where a slight amount of chlorine is added, to kill off any pathogenic (disease causing) bacteria in the sewage. The chlorine is then removed, so that non-chlorinated water is discharged.
When the water meets or exceeds U.S. EPA standards, it is pumped back into a nearby river, in the Patuxent and the Potomac watersheds. The water that is discharged is actually cleaner than the natural stream water itself.
What happened to the gunk that was removed from the wastewater?
Trash removed early in the process is sent to landfills. The gunk that is removed through the Biological Nutrient Removal is “dewatered” using filters, drying beds or centrifuges. Now the material is called biosolids and they are beneficially used in permitted land applications.
Most households have cleaners, pesticides, paints, motor oil and prescription drugs. Do not pour them down the drain, in the toilet, on the ground or in storm drains. Take hazardous substances to a recycling center, and dispose of pharmaceuticals in the trash.
It’s bad for our health. But did you know it’s bad for pipes in our homes, too?
Grease blockages in sewer pipes are common causes of sewage overflows and basement backups.
Grease is a byproduct of cooking and comes from meat fats, oils, shortening, butter, margarine, food scraps, even sauces and dairy products.