In 1992, the City opened the secondary wastewater facility with a capacity of 4.5 million gallons per day. The Anacortes Wastewater Treatment Plant takes the raw primary and secondary solids from wastewater, blends it, and thickens it. The thickened material is conditioned with polymer and dewatered on a belt filter press. The dewatered material is incinerated in a fluidized bed incinerator reducing the volume by roughly 80%.
Anacortes' involvement with Northwest Biosolids as an associate utility provides access to a collaborative regional network that promotes environmental sustainability and beneficial use of biosolids. In future planning efforts, this network can help Anacortes discover options for biosolids recycling.
In 2009, the Skagit Council of Governments gave the plant an award for the largest reduction in energy usage. Upgrades to equipment created some of the energy savings, but it was the plant staff who came up with creative ways to make the plant run more efficiently.
The equipment changes included:
- Replacement of one of the 150 hp Hoffman multistage centrifugal blowers with a VFD controlled 75hp Aerzen positive displacement blower.
- Replacement of the Sanitare and course air diffusers in one of the two aeration basins with the aerostrip diffusers with a much more efficient finer bubble pattern.
- Installation of two well type pressure tanks for the air gapped city water reducing the run time of the 10hp lead pump from 24 hours per day to 2 to 4 hours per day.
The operational changes included:
- The switch from W5 water to W3, plant reuse, water in the incinerator allowing the shutdown of the 10hp W5 pumps permanently.
- The diversion of excess air from the new Aerzen blower to the primary and secondary channels allowing the shutdown of two 10hp channel blowers that had been running 24 hours per day.
- Fined tuned the operation and reset operational targets for the incinerator to optimize the use of diesel fuel.