Program Delivery Plan

SECTION 5. NORTH BASIN PROJECTS
Plants (CH2M HILL, 2008). The technologies that were evaluated included purchased
sodium hypochlorite, on-site generation of sodium hypochlorite, ultraviolet (UV)
disinfection, and a combination of UV disinfection and purchased sodium hypochlorite.
At the North WWTP, use of purchased 12.5% sodium hypochlorite is the least-costly
alternative, given a 20-year present worth basis. UV was found to be considerably more
expensive on a present worth basis than sodium hypochlorite, primarily because it would
also require upgrading the North WWTP to a trickling filter/solids contact (TF/SC) process.
Trickling filter effluents are considered unsuitable for UV disinfection.
Standby Power
Standby power for the North WWTP is discussed in the Emergency Generators section of
this PDP.
5.5.3 Priority Two Improvements
Priority Two improvements include operations and maintenance needs that include asset
preservation, cost efficiency needs, and environmental needs. Asset preservation needs
include improvements that are required to preserve existing assets, such as screening and
grit removal. Cost efficiency needs include improvements that are required to increase the
efficiency of operations and maintenance, such as SCADA. Environmental needs include
improvements that are required to improve the overall environment of the North WWTP,
such as odor control.
The improvements included in Priority Two are new preliminary treatment, new influent
pump station, odor control, digester gas utilization, and SCADA.
New Preliminary Treatment and Influent Pump Station
The Master Plan – Existing Wastewater Treatment Plant Descriptions and Infrastructure Condition
Assessment (CH2M HILL, 2008) recommends the following modifications at the North
WWTP due to the condition assessment for Priority Two.
New Preliminary Treatment (screenings and grit removal)
New Influent Pump Station
These facilities will allow the North WWTP to continue to operate into the future.
Odor Control
Odor issues were evaluated at each of the three large WWTPs. This evaluation included
conducting air sampling to determine where odors are experienced at each WWTP. Once
the odor issues were identified, several odor control technologies were evaluated. Biotowers
are recommended as the primary odor control technology, with some other
technologies being used for specific odor issues, such as those at dewatering facilities. Refer
to Master Plan – Odor Control Analysis and Facility Plan Recommendations (CH2M HILL, 2008)
for more information.
The North WWTP has the highest odor emissions, which are creating a nuisance for nearby
residents. Given resident complaints at the North WWTP, the North WWTP Odor Control
Project, which includes chemical feed at five pump stations feeding into the treatment plant
and biotowers at the headworks, was given a high priority and is expected to remediate the
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