The Town of Discovery
Bay Community
Services District
Wastewater Treatment Plant
Master Plan
NOVEMBER 9, 2011
Master Plan Purpose
 Assessment
 Analysis
of existing facilities
of future needs
 Road map for improvements
Master Plan Organization
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Section 1: Introduction
Section 2: Executive Summary
Section 3: Existing and Future Land Use
Section 4: Collection System Pump Stations
Section 5: Wastewater Flows and Loads
Section 6: Overview of Wastewater Treatment Plant
Section 7: Plant Hydraulic Capacity Analysis
Section 8: Waste Discharge and Treatment Requirements
Section 9: Influent Pump Station
Section 10: Headworks
Section 11: Secondary Treatment
Section 12: Secondary Effluent Lift Station
Section 13: Tertiary Filtration
Section 14: UV Disinfection
Section 15: Salinity Reduction
Section 16: Emergency Storage
Section 17: Solids Handling
Section 18: SCADA System
Section 19: Summary of Future Improvements
Projected Growth within TDBCSD
Collection System Pump Station
Improvements

Total budgeting cost for improvements to all pump
stations is $650,000 as shown in Table 2-2.

It is recommended that the District establish priorities
for this work and then budget to accomplish certain
portions of the work each year until completed.
Existing and Future Flows and Loads
Existing Wastewater Treatment Plant(s)
Figure 6-1
Flow Diagram
Plant Hydraulic Analysis
 Existing
and future peak flows
modeled
 Existing facilities can accommodate
future peak flows with suitable
modifications to:

Influent pump station
 Secondary effluent lift station
 Export pump station
Key NPDES Permit Requirements
Influent Pump Station



Current issues with the Influent Pump Station include:

Pump ragging

Lack of flow splitting controls

Lack of sump mixing that results in different wastewater characteristics for Plants
1 and 2

Inability to take the pump station out of service for needed repairs
Recommended improvements to the Influent Pump
Station include:

Structural rehabilitation

Replacement of all pumps

Piping modifications

Installation of a sump mixer

Improved flow splitting controls

Re-activate Pump Station “W” to allow Influent PS to be taken out of service and
to allow pumping raw sewage to emergency storage basin
The total estimated capital cost for these
improvements is about $1 million.
Headworks
 One
at each plant with:

Flow measurement flume
 Screen to remove rags, large solids
 Influent sampler (Plant 2 only)
 Screen
capacity

6.2 Mgal/d, each
 No expansion needed
 Influent
sampling improvements
recommended
Existing Secondary
Treatment Facilities

Basin sizes good for 2.0 Mgal/d AAF
(currently at 90 percent capacity)

One additional brush rotor (or equivalent)
recommended in each ditch for reliability

Can take a clarifier out of service in dry
weather

Cannot take either ditch out of service
Existing Secondary
Treatment Facilities (con’t)

Add one new ditch and one new clarifier at
Plant 2

Add standby floating aerator in each existing
ditch

with future design flows, will be able to:

Take any clarifier out of service at any time of the year

Take any ditch out of service during dry weather flows
Secondary Treatment System Expansion
Cost Estimate
Secondary Effluent Lift Station
 If
no future filters, future peak flows
can be accommodated by “overspeeding” existing pumps
 If filters are added, pump lift would
increase, requiring new impellers,
motors, VFDs
 Cost: $250,000
Tertiary Filtration

May be needed for




Improved UV disinfection
Reclamation
Future discharge requirements
Provide flow equalization ahead of filters
UV Disinfection

Three scenarios:

Scenario 1: 23 MPN/100 mL without filters (existing conditions)

Scenario 2: 23 MPN/100 mL with filters.

Scenario 3: 2.2 MPN with filters (possible future requirement)

Scenarios 1 and 3 require conversion of the
existing UV3000 channel to UV3000Plus Capital
cost = $1.2 million.

Scenario 2 requires only flow splitting weir
improvements

On-site viral bioassay testing needed to confirm
capacity
Salinity Reduction

1,000 µmhos/cm desired by state, but not
currently required

To meet 1,000 µmhos/cm:


Microfiltration

Reverse osmosis

Brine concentration

Concentrated brine disposal

Capital cost = $15.7 million

Annual cost = $2.12 million
Improved source control recommended to reduce
salinity
Emergency Storage

Existing 5 Mgal earthen basin at Plant
1 not usable

Improvements required include:
Re-activate Pump Station “W”
 New Return pump station for draining basin
 Cost = $243,000

Wetlands Treatment Potential

2007 demonstration project to evaluate
metals removal, mainly copper

Wetlands demonstration removed 90 percent
copper

Alternative copper compliance methods
eliminated the need for treatment

Possible future potential for metals and
refractory organics
Solids Handling

Sludge lagoons are full or nearly full

Belt press capacity limits use of solar dryers

Future improvements:

Phase 1
- 2 belt presses
- 2 solar dryers
- Cost = $4.65 million

Phase 2
- 1 solar dryer
- Cost = $2.03 million
SCADA System

Existing system and previous
recommendations reviewed

Recommended improvements:

Redundant master RTU at Plant 2

Improved features for monitoring and control sewage lift
stations

Begin long-term replacement of obsolete PLCs on a priority
basis

Total cost = $350,000
Summary of Improvements
A
list of all the recommended
improvements developed in this
Master Plan is presented in the
handout Table 2-14.
A
site plan indicating where the
future improvements could be
located is shown is the handout
Figure 20-1.