Wastewater Treatment Plant

The Wastewater Treatment Plant is a dual-powered,multi-cellular, aerated lagoon system with Submerged Fixed Film Media. The City is entrusted with the quality of water that our wastewater plant effluents into the Snohomish River.  The purposes of the Snohomish Wastewater Treatment Plant are: 

  1. Remove suspended solids and floatable material
  2. Treat biodegradable organics
  3. Reduce ammonia nitrogen
  4. Eliminate pathogenic organisms from the wastewater  

The facilities must meet secondary effluent criteria and total maximum daily load (TMDL)-based limits specified in the National Pollutant Discharge Elimination System (NPDES)Waste Discharge Permit No. WA-002954-8.  The NPDES permit also sets limits for influent flow and loading capacities.  The WWTP has a permitted maximum month influent flow of 2.80 million gallons per day (MGD) and permitted maximum month influent load of 3,960 pounds per day (lb/day) for 5-day carbonaceous biological oxygen demand (CBOD5) and 4,400 lb/day for total suspended solids (TSS). 

The WWTP is always looking at new and innovative approaches to lowering costs while improving the quality of the effluent leaving the plant.