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Wastewater Pre-Treatment Program

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The purpose of the Wastewater Treatment Plant is to remove pollutants. Some pollutants, however, cannot be removed at the Plant or can cause problems with Plant operations.  The City’s Wastewater Treatment Plant began experiencing more frequent problems, so the City initiated a pre-treatment program in 2003.

Pre-treatment means that pollutants are removed from the wastewater before it is discharged to the sewer. For residential customers, this means not disposing of certain wastes such as cooking oil and greaseWenatchee's Sewer Jet Truck, garbage or hazardous chemicals down the drain. For commercial and industrial customers, pre-treatment equipment may be required to remove pollutants while ensuring that certain wastes are not discharged. City staff inspect businesses and collect wastewater samples when necessary to ensure compliance with local, state and federal wastewater regulations.

Some areas of focus for the pre-treatment program are on reducing the amount of garbage as well as fats, oils and grease that are disposed in the sewer system. To learn more about these issues, we invite you to read the following brochures:

Non-Contact Cooling Water (NCCW)
Wenatchee City Code 4.08.08 2(j)  prohibits the discharge of any cooling water or boiler water containing chemicals other than chlorine and/or sulfuric acid except as approved by the director. This code was adopted to address discharges that interfere with operations at the Wastewater Treatment Plant.

Non-contact cooling water has long been a concern because of the chemicals that are often used and the number of customers that discharge NCCW to the City. Biocides, algaecides and other anti-microbial treatments are of course a problem, since the treatment plant uses microorganisms to treat the wastewater. De-scalants are a concern because of the polymers and other components which keep micronutrients such as calcium and magnesium suspended and therefore, unavailable to the microorganisms. There is also a concern that the polymers may affect solids settling at the plant which is an essential part of wastewater treatment. The City's wastewater treatment plant continues to experience problems with toxic discharges and floating solids.

As a result of these issues, the City has asked that all non-contact cooling water dischargers develop other options for disposal or treatment of their NCCW discharges.  Below is the list of chemicals that have been approved for use in cooling towers for commercial and industrial facilities.  The list also includes the conditions that must be met when these chemicals are used.

Disposable Does Not Mean Flushable
An easy way for homeowners to pretreat their waste is to not dispose of garbage in their toilets.  As wastewater enters the treatment plant the garbage must be screened out to prevent plugs and pump failures.  The material removed from the wastewater influent must then be bagged and hauled to the landfill.  Sometimes the garbage that gets disposed in the sewer system does not make it to the treatment plant.  The garbage gets stuck in the sewer lines and in lift station pumps, which can result in sanitary sewer overflows.  A sanitary sewer overflow can result in the sewage backing up into your house, your neighbor's house or into the streets.  This creates a large mess and is costly to clean up.

Below is a list of household items that should not be flushed down the toilet:

  • Flushable Wet-Wipes*
  • Baby Wipes
  • Kleenex
  • Paper Towels
  • Cleaning Towelettes
  • Dust Cloths
  • Diapers
  • Feminine Care Products
  • Toilet Wand Disposable Heads
  • Oil and Grease from cooking
  • Automotive Fluids
  • Rags

* Note that even wipes that are labeled as "flushable" are on the list.  These wipes do not disperse quickly like toilet paper, they can stay intact all the way to the treatment plant.

The City of Spokane's Department of Wastewater Management in partnership with Water Environment Federation produced a good video showing common household items that shouldn't be flushed down the toilet.  Click here to watch the "Will It Flush" video.

 For questions about the pre-treatment program please contact the Environmental Division at (509)888-3235.

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