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Wastewater Treatment

Wastewater refers to any water that needs cleaning/treatment after it is used indoors such as water from dish washing, laundry, baths/showers, toilets, and countless other sources. All wastewater or sewage produced by the City of Ocean Shores is managed and treated by the city owned wastewater treatment plant (WWTP) located at the south end of the city next to the jetty. The WWTP provides primary and secondary treatment for the City service area (vacuum and gravity lines) and also for specific areas outside of the City limits. Collected wastewater effluent is treated to meet all state and federal requirements. The final effluent, after being disinfected with ultraviolet light is discharged into Grays Harbor on outgoing tides. Biosolids from the treatment process are hauled off site for beneficial land application.

Wastewater Treatment Process
Upon entering the WWTP the influent wastewater is first pumped through a mechanical screen that removes large non-digestable objects. A parallel manual screen is also available as a backup. Both of the screens remove rags, branches, and other debris that can damage treatment equipment downstream. Once the wastewater is screened, it is conveyed through a grit chamber, where grit is allowed to settle and removed from the process. The wastewater then flows to a three-zone selector basin where return activated sludge (RAS) is added. Selector zones create environments conducive to the growth of microorganisms that form flocs and settle well in secondary clarifiers. The combined wastewater then flows to the oxidation ditch, where fine-bubble diffusers provide oxygen for uptake by the microorganisms. The mixed liquor from the oxidation ditch then flows to the two secondary clarifiers. A rotating scraper arm on the bottom of the clarifier uses suction to return sludge (RAS) to the selector basin. The clarified effluent flows through a UV disinfection system and is stored in the storage pond next to the WWTP office. A control valve allows for discharge into the mouth of Grays harbor with the out going tide.

Secondary Clarifiers
As mentioned above, there are two 50-foot secondary clarifiers, where sludge is allowed to settle. Sludge hopper arms at the bottom of the secondary clarifier move the settled sludge to the waste activated sludge (WAS) pump station. The sludge is usually pumped to the sludge lagoon, but may also be pumped directly to the storage tank for thickening.

Sludge Lagoon And Storage Tank
The sludge lagoon is a 2.5 million gallon lined earthen basin that has four floating aerators to provide mixing and aeration to digest the sludge to Class B standards. The sludge storage tank is a 63,400-gallon tank that receives sludge from the lagoon or directly from the WAS pump. Membrane disc diffusers on the bottom of the tank mix the contents to provide uniform solids content before it is sent to the belt filter press for dewatering. The sludge may also return to the sludge lagoon for storage.

Belt Filter Press And Disposal Of Biosolids
Sludge feed pumps convey sludge from the sludge lagoon or storage tank to the belt filter press. The belt filter press with the addition of a liquid polymer removes the effluent from the sludge leaving behind a dewatered solid or biosolid. All dewatered solids are currently hauled to offsite beneficial use facilities (BUFs). Hauling is the primary mode of disposal, with the remaining solids stored on-site unil they can be land applied.

Wastewater Treatment Plant Process Schematic
What Not To Flush
The toilet is only meant to flush the three P’s - pee, poop and (toilet) paper. Flushing other things, or sending them down the drain, can cause all sorts of problems in your home or business, like wasted water, clogged pipes, and sewage spills. It can also cause problems in the sewer system, treatment plant, and in the environment:

  • Wipes - Wipes don’t break down like toilet paper. Sooner or later, they’ll get stuck in your home plumbing, the sewer system, or the treatment plant. Throw wipes (personal wipes, baby wipes, cleaning wipes, etc.) in the trash, every single time. Even "flushable" wipes clog pipes.
  • Medicines - Wastewater treatment systems are not designed to treat and remove medicines from the water. Since the treated water is released to the environment, medicines that remain in the water are released too. Don’t flush unused medications down the toilet or drain. Instead, take them to a secure collection station, such as those located at local law enforcement agencies. If no local disposal options are available medicines can also be disposed of in the trash.
  • Fats, Oils and Grease - It may seem harmless to pour cooking oil, melted butter, or bacon grease down the drain, but they solidify as they cool, causing clogs in household plumbing or the sewer system. Those clogs can lead to sewage backups in your home or business or in the street or environment. Instead, collect grease in an empty can, store it in the freezer, and dispose of it in the garbage once it turns solid. Used cooking oil can also be recycled.
  • Hygiene Products - Q-tips, cotton balls, makeup removal pads, tampons, sanitary pads, and dental floss can cause clogs and jams in your plumbing and in sewer system equipment. Use the trash can instead, toilets are not for trash.
  • Personal Care and Household Products - The many household and personal care products we all use, including medicines, shampoos, soaps, and cleaning products, contain chemicals. When the chemicals go down the drain, they enter our wastewater system, and will eventually reach the Pacific Ocean and may entor or groundwater aquifers. Some of the chemicals may be toxic, posing a potential risk to your health or the environment. You can help protect your family and our environment by choosing products with less toxic contents, using fewer products, and disposing of products properly.
  • Pet Waste - Wastewater treatment plants are not designed to treat pet waste. Pet products that claim to be flushable, like some poop bags and kitty litters, are definitely NOT. Dispose of pet waste, poop bags, and kitty litter in the trash.