In wastewater, solids capable of settling can restrict or block flow in sewer lines. A company or facility that discharges solids that causes a sewage backup is liable for any damages.
King County prohibits discharge of the following types of waste from all nondomestic sources:
- materials such as ashes, sand, grass, and gravel
- solid or viscous pollutants in amounts that will obstruct the flow in the collection system and/or treatment plant
- Solid material, including food-grinder waste, which is not capable of passing through a 1/4-inch sieve.
King County has the following local limit for settleable solids:
- Industrial wastewater must contain less than 7 milliliters per liter of solids capable of settling.