City of WillitsWTP Design and Funding

Procurement Update

February 24th City Council MeetingScott Buecker, P.E.

Agenda

BackgroundRaw Water Quality IssuesAvailable Pretreatment TechnologiesRecommended Path ForwardCost ImpactFunding Status and Schedule Update

Background

Water Works Engineers contracted with the City of Willits in September of 2009 for two tasks:1. Finish the partially completed design of a relocation

of the City’s coagulant injection and mixing point: “Phase 1”

2. Design an expansion of the plant from two Siemens Trident Microfloc units to three units: “Phase 2”

Background

Purpose of both phases is to improve treatment plant performance: turbidity removal manganese precipitate removal Improved treatment efficiency

(minimize backwash waste)

Raw Water Quality Issues:

1. Seasonal spikes in source water turbidity (up to 200 NTU) due to colloidal clay erosion in winter storm events

2. Summer algal blooms during peak demand3. Manganese oxidation and precipitation

throughout the WTP

Raw Water Quality Issues:

Colloidal Clay

Oxidized Manganese

Colloidal Algae

Phase 1

During the data collection process for Phase 1, WWE realized that relocation of the City’s coagulant injection point would not improve any of the three key issues at the WTPWrote technical memorandum documenting concernsAccepted by the City, Phase 1 placed on hold

How to Resolve WTP Issues

WWE has been obtaining data from the City, researching the issues, and corresponding with City staff to develop the most cost-effective solution

Treatment of Colloidal Clay

How do you treat colloidal clay? Must destabilize charge balance so that it will

coagulate and form a settleable floc Polyaluminum Chloride (Pro Pac) will do this when given

enough time and the right tank configuration The existing adsorption clarifiers are not providing

enough time or the right configuration The treatment limits of the Trident Microfloc are 30 to 75

NTU

Treatment of Colloidal Algae

How do you treat colloidal algae? Pre-oxidation proven to improve algae

coagulation and flocculation – KMnO4 in place, is effective at the right dose

Destabilize charge balance so that it will coagulate and form a settleable floc Polyaluminum Chloride (Pro Pac) will do this

when given enough time and the right tank configuration

The existing adsorption clarifiers are not providing enough time or the right configuration

Treatment of Manganese

How do you treat Manganese? Oxidize it first to form precipitate

Potassium permanganate oxidation requires less than one minute contact time to oxidize manganese

Then destabilize charge balance so that it will coagulate and form a settleable floc MnO2 proven to improve flocculation and sedimentation

Remove the precipitate from the plant to prevent coating of media, fouling of instrumentation, and turbidity spikes

Recurring Themes

Pre-oxidationCoagulationSettleable floc – How to create? Charge balance (preoxidation and

coagulation chemistry) and then create the particle collisions

Provide a quiescent settling zone

Solids separation and removal – get the bulk of it out before the existing Trident units

Pretreatment Alternatives

Coagulation, flocculation and sedimentation processes: Conventional Process – like Ukiah WTP – costly All in One Processes:

Proprietary Processes – costly and overkill Actiflo, Densadeg, MIEX

Non-proprietary Processes: Dissolved Air Flotation – more complex, higher O&M Solids Contact Upflow Clarifier Solids Recirculation Processes

Solids Contact Upflow Clarifier

Original Manufacturer’s Recommendation

HS and HSR Clarifier Technology

Current Status of Evaluation

Evaluating Solids Contact Upflow Clarifier vs. HSR Clarifiers HSR Treatment Performance Operational Ease Capital and O&M Cost

Preliminary Results of Evaluation

Capital and O&M Costs are comparableWWE is currently more comfortable with the treatment performance of the Solids Contact Upflow Clarifier and recommends moving forward

Recommendations

Add a robust pretreatment process as part of the WTP Upgrade and Expansion project, get the bulk of the solids out before Microfloc Cost Impact: $500 to $700K Capital Cost $31,000 additional engineering cost Assuming SRF funding package will be

80% Grant, 20% Loan, rate impact of pretreatment process is approximately $0.40/connection/month

Funding Status Update

Categorized as either “D” or “E”, both of which will be funded in this year’s cycleTechnical Engineering Report and complete application due March 31st

Notice of Application Acceptance (NOAA) in August 2010Submit Final Plans and Specifications in Fall 2010SRF Funding Agreement in late 2010Construction of the upgrade and expansion in summer 2011

Other Items Outside of WWE Scope

Geotechnical EngineeringStructural EngineeringSite SurveyingCalifornia Environmental Quality Act Should be done by Fall 2010