~~~~ WWTP Master Plan Project

Transcription

1 ~~~~ WWTP Master Plan Project City Council - April 7, 2014

2 WWTP History and Issues Constructed in 1994 Aging mechanical equipment - Frequent equipment failures - Resulted in TCEQ permit violations - High maintenance and repair cost Exceeded permitted effluent Ammonia-N and E. Coli in 2012 and additional past dates - TCEQ Enforcement Action - Fines and Supplemental Engineering Projects (Household Hazardous Waste Clean Up)

3 Steps Taken to Date Installed new screening equipment in 2013 Installed two new surface aerators in February 2014 to supplement existing aeration equipment Authorized purchase of six new 30-HP brush aerators in February 2014, to be installed in May 2014 Met with Regional and State TCEQ Staff to Inform TCEQ of actions the City is taking at the WWTP - Granted an additional 90 days to comply with requirements of Enforcement Action - Discussion of future permit limits

4 Master Plan Identify existing facility limitations and constraints through site visits and interviews with City Staff Defined capacity of existing WWTP Developed improvement alternatives to address existing deficiencies Consider future regulatory requirements Define and prioritize the treatment plant CIP

5 Alternative Evaluation Treatment Process Alternatives (Required Process Improvements) - Alternative I: Mechanical Aeration - Alternative II: Diffused Aeration - Alternative III: Parallel Process Train - Alternative IV: New Treatment Plant Future Considerations for Nutrient Removal - Chemical Phosphorus Removal - Biological Nutrient Removal

6 Alternative I: Mechanical Aeration Currently installed aeration capacity (140 HP) is insufficient Required installation of 330 HP of aeration capacity Conceptual Opinion of Probable Capital Cost: - $1,428,000 Advantages: - Familiar technology - Least amount of plant modifications required - Least capital cost relative to other alternatives Disadvantages - More difficult to control dissolved oxygen - Non-uniform oxygen concentration - Not aesthetically pleasing from Highway 290

7 Alternative II: Diffused Aeration Replace existing aeration equipment with fine bubble diffused aeration system to provide required aeration capacity Conceptual Opinion of Probable Capital Cost: - $7,017,000 Advantages - Can be more reliable - Easier to control dissolved oxygen - Uniform oxygen concentration Disadvantages - City s oxidation ditch configuration not ideal for diffused air, resulting in high costs - Mechanical equipment still required for forward motion of flow - Unfamiliar technology to staff

8 Alternative III: Parallel Basin Parallel Aeration Basin with Diffused Aeration Conceptual Opinion of Probable Capital Cost: - $8,161,000 Advantages - Can be more reliable - Provides redundancy - High flexibility to meet potential future nutrient limits Disadvantages - High capital cost - Will trigger permit modification with the addition of nutrient limits

9 Alternative IV: New WWTP Construction of a new WWTP on adjacent City-owned property or other property downstream Conceptual Opinion of Probable Capital Cost: - $28,510,000 Advantages: - Designed for most efficient total system performance - Relocation of WWTP will reduce visibility from Highway High Profile Real Estate Disadvantages: - Highest capital cost - Would require a new discharge permit - Little to no use for existing WWTP infrastructure

10 Future Considerations for Nutrient Removal Chemical Phosphorus Removal Biological Nutrient Removal

11 Chemical Phosphorus Removal Only required if TCEQ imposes a Phosphorus limit - Phosphorus removal achieved by the addition of aluminum sulfate Conceptual Opinion of Probable Capital Cost: - $570,000 Advantages: - Works well with City s seasonal discharge - Easy addition if/when phosphorus limits are imposed Disadvantages: - Higher aeration requirement - Higher solids production

12 Biological Nutrient Removal Only required if TCEQ imposes nutrient limits Requires the addition of future treatment zones upstream of existing basin Conceptual Opinion of Probable Capital Cost: - $3,936,000 Advantages - Potential energy savings - Better settling sludge Disadvantages - More complicated operation - Potential to generate more odor - Not ideal due with seasonal discharges

13 Summary of Alternative Capital Costs Alternatives to address current WWTP issues: Alternative Conceptual Opinion of Capital Cost I: Mechanical Aeration $1,428,000 II: Diffused Aeration $7,017,000 III: Parallel Basin $8,161,000 IV: New WWTP $28,510,000 Additional improvements required only if TCEQ imposes nutrient limits: Alternative Chemical Phosphorus Removal $570,000 Conceptual Opinion of Capital Cost Biological Nutrient Removal $3,936,000

14 Alternative Criteria and Weighting Factors Capital Cost: 3 Reliability: 3 Potential to Trigger a Permit Modification: 3 Annual Operation and Maintenance: 2 Energy Consumption: 2 Potential to Meet Future Nutrient Limits: 2 Ease of Use: 1

15 Evaluation of Process Alternatives

16 Recommended Alternative Alternative I: Mechanical Aeration - Most cost effective to meet needs and budget constraints - New equipment will be reliable while maintaining use of existing infrastructure - Allows for future nutrient removal provisions

17 Additional WWTP Improvements Disinfection and Chemical Storage: $627,000 Dewatering Improvements: $933,000 Gravity Thickener Improvements: $42,000 Improved RAS/WAS Control: $217,000 Site Security: $256,000 Effluent Storage Pond Improvements: $627,000 Oxidation Ditch Dredging: $177,000 MLSS Pump Station Improvements: $145,000 New Administration Building: $350,000 Total = $3,374,000

18 Phase I Improvements Mechanical Aeration $1,428,000 Disinfection and Chemical Storage: $627,000 Dewatering Improvements: $933,000 Gravity Thickener Improvements: $42,000 Improved RAS/WAS Control: $217,000 Total = $3,247,000 Design of all improvements June July Aug Sept Oct Nov Dec Jan Feb March April May June July Aug Sept Oct Nov Dec Jan Feb March Phase I Bid Phase I Construction: Additional Aeration Disinfection Improvements Mechanical Dewatering Gravity Thickener Improvements RAS/WAS Improvements $3,247,000

19 Schedule of Future Improvements Site Security New Administration Building Oxidation Ditch Dredging MLSS Pump Station Improvments Misc. Equipment and Improvements Effluent Storage Pond Improvements Site Security: $256,000 New Administration Building: $350,000 Oxidation Ditch Dredging: $177,000 MLSS Pump Station Improvements: $145,000 Misc. Equipment and Improvements: $109,000 (Composite Sampler, Polymer Feed, Exhaust System in Dewatering, Chlorine Feed Points) Effluent Storage Pond Improvements: $627,000

20 Questions? Alberto Rodriguez, P.E. Project Manager, HDR Engineering

21 For More Information... For more information regarding this presentation, please contact: Kris Kneese, P.E. Assistant City Engineer City of Fredericksburg (830)