Visalia Water
Reclamation
Facility
Facility Plan Update
Council Presentation
City of Visalia
2/20/2024
Background and Purpose
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WRF Overview
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T reatment Photos
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Project Background and Severity
• The WRF was upgraded in 2017 due to
increased regulations
• Improvements were made for a rated capacity
of 22 mgd, however to save costs some
improvements were not implemented leaving
the total design capacity at 18 mgd.
• In recent years, increased industrial loads along
with water conservation efforts have increased
influent wastewater concentrations and as a
result put increased strains on the facility.
• This study is an effort to update current
treatment process capacities using a biological
process model.
T reatment Process
Performance
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Solids Handling Facilities are Struggling
• Digesters are operating at very low HRTs and
are currently being overloaded during peak
loading periods
• PS and TWAS pumping is limited to 2-3%,
which exacerbates HRT limitation
• Digesters are overloaded with Grit causing
reduced volume (est 20% by volume filled)
• City does not have sufficient redundancy with
dewatering equipment due to no standby
dewatering screw press
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Historical Influent Data
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Biological Oxygen Demand and T otal
Suspended Solids Loadings
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Capacity/Firm Capacity Analysis
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Process Area Capacity
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Sludge Flows & Dewatering Capacity
Rated Screw Press Capacity (x1) – 158,400 gpd
Rated Screw Press Capacity (x2) – 316,800 gpd
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Impact of higher feed concentration (4.5%) on Digester SRT Minimum recommended
HRT of 15 days
Condition Assessment
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Condition Assessment Findings
• In general the equipment at the WRF is in good condition • There were significant upgrades in the last improvement project and all of this equipment is in good condition
• The following areas need some attention:
»Headworks
»Digesters
»Sludge Drying beds
»Misc. piping/pumps/valves
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Site Photos
Environmental Opportunities
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Environmental Opportunities
• Engine Generators
• Microturbines
• Gas Turbines
• Fuel Cells
• RNG to Pipeline Injection
• R-CNG to Vehicle Fuel
Near-T erm Improvements
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Near-term capacity related projects
•Now:
»Replace PS and TWAS pumps to allow
thickening of the sludge more
−Goal: 3% PS and 6% TWAS
»Add one screw press for firm
capacity/redundancy
»Add one digester with same capacity
as Digester No. 8
»Add additional UV Bank to provide
firm capacity/redundancy
Summary and
Recommendations
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Immediate Recommendations for Digesters
• Place Dig No. 4 back in service (waiting on piping)
• Continue tracking digester health parameters and develop response plan for early signs of failure
• Clean/de-grit digesters that have not been cleaned recently (i.e. last 2-4 years)
• PS and TWAS pumping modifications and/or replace discharge piping • Re-purpose Dig #8 as a primary digester (Currently used as 70% storage)
• Additional digester volume likely needed to accommodate future growth to buildout
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Solids Handling Improvements
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TWAS Pumps
•Now:
»Replace PS and TWAS pumps to allow
thickening of the sludge more
−Goal: 3% PS and 6% TWAS
»Add two screw presses
»Add three digesters with same
capacity as Digester No. 8
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TWAS Pump Station Upgrades
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Digester Upgrades
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Digester Upgrades
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Near T erm Dewatering Recommendations
• Additional dewatering unit needed to provide
redundancy/standby
• Provide additional drying beds and sludge storage if
dewatering maintenance or down time is experienced
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Dewatering Unit
• Add photo and potential layout
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Screw Press
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Sludge Drying Beds
SLUDGE
DRYING
BEDS
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Digester Sludge Holding Pond
Digester
Sludge
Holding
Pond
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Digester Sludge Holding Pond
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Near T erm UV Recommendations
• Additional UV bank unit needed to provide
redundancy/standby