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The Town of Discovery Bay Community Services District Wastewater Treatment Plant Master Plan NOVEMBER 9, 2011.

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Presentation on theme: "The Town of Discovery Bay Community Services District Wastewater Treatment Plant Master Plan NOVEMBER 9, 2011."— Presentation transcript:

1 The Town of Discovery Bay Community Services District Wastewater Treatment Plant Master Plan NOVEMBER 9, 2011

2 Master Plan Purpose  Assessment of existing facilities  Analysis of future needs  Road map for improvements

3 Master Plan Organization 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

4 Projected Growth within TDBCSD

5 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.

6 Existing and Future Flows and Loads

7 Existing Wastewater Treatment Plant(s) Figure 6-1 Flow Diagram

8 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

9 Key NPDES Permit Requirements

10 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.

11 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

12 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

13 Existing Secondary Treatment Facilities 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

14 Secondary Treatment System Expansion Cost Estimate

15 Secondary Effluent Lift Station  If no future filters, future peak flows can be accommodated by “over- speeding” existing pumps  If filters are added, pump lift would increase, requiring new impellers, motors, VFDs  Cost: $250,000

16 Tertiary Filtration  May be needed for  Improved UV disinfection  Reclamation  Future discharge requirements  Provide flow equalization ahead of filters

17 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

18 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

19 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

20 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

21 Solids Handling  Sludge lagoons are full or nearly full  Belt press capacity limits use of solar dryers  Future improvements:  Phase belt presses - 2 solar dryers - Cost = $4.65 million  Phase solar dryer - Cost = $2.03 million

22 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

23 Summary of Improvements  A list of all the recommended improvements developed in this Master Plan is presented in the handout Table  A site plan indicating where the future improvements could be located is shown is the handout Figure 20-1.


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