City of Willits

sixcageyΜηχανική

22 Φεβ 2014 (πριν από 3 χρόνια και 7 μήνες)

70 εμφανίσεις

City of Willits

WTP Design and Funding
Procurement Update


February 24
th

City Council Meeting

Scott
Buecker
, P.E.

Agenda

Background

Raw Water Quality Issues

Available Pretreatment Technologies

Recommended Path Forward

Cost Impact

Funding 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 demand

3.
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 WTP

Wrote technical memorandum documenting
concerns

Accepted 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
-
oxidation

Coagulation

Settleable

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 comparable

WWE 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 cycle

Technical Engineering Report and complete
application due March 31
st

Notice of Application Acceptance (NOAA) in August
2010

Submit Final Plans and Specifications in Fall 2010

SRF Funding Agreement in late 2010

Construction of the upgrade and expansion in
summer 2011

Other Items Outside of WWE Scope

Geotechnical Engineering

Structural Engineering

Site Surveying

California Environmental Quality Act


Should be done by Fall 2010