Disinfection By-Products Reduction and SCADA Evaluation and WTP Sludge Removal System and Dewatering Facility

Transcription

1 SOUTH GRANVILLE WATER & SEWER AUTHORITY Disinfection By-Products Reduction and SCADA Evaluation and WTP Sludge Removal System and Dewatering Facility Presentation to the SGWASA Board December 12, 2017

2 TTHM (mg/l) Locational Running Annual Average (LRAA) for TTHM B01 B02 B03 B Alum Ferric sulfate MCL for TTHM /2/ /27/ /23/2015 8/18/2016 6/14/2017 4/10/2018

3 HAA5 (mg/l) Locational Running Annual Average (LRAA) for HAA B01 B02 B03 B Alum Ferric sulfate MCL for HAA /2/ /27/ /23/2015 8/18/2016 6/14/2017 4/10/2018

4 Quarterly TTHM data from November 2013 to November 2017 Avg = 20 ppb Lowest values in 5 years 81% lower than 11/2016

5 Quarterly HAA5 data from November 2013 to November 2017 Avg = 17 ppb Some of the lowest values in 5 years 78% lower than 11/2016

6 TOC (mg/l), TTHM (µg/l), THAA (µg/l) Simulated Distribution Samples - DBPs Lake TOC: 10.2 mg/l, Reservoir TOC: 9.2 mg/l 80 TOC TTHM THAA FeCl=Ferric chloride FeS=Ferric sulfate FeCl No Oxidant 60 FeCl 0.5 ClO2 60 FeS w/851tr Full Scale Tap

7 Potential Factors Affecting DBP formation and creating variance from bench testing 1. WTP is manually controlled so there could be variability in flow (per filter), chemical doses, etc that affect chlorine contact time and WTP performance 2. Operations staff - learning curve of operating with ferric sulfate coagulation. 3. Maintaining proper sludge levels in the sedimentation basins has been challenging due to failing draining valves and sludge collection equipment.

8 TTHM profile thru WTP

9 HAA5 profile thru WTP

10 Recommendations for DBP Compliance

11 Recommendations for DBP compliance: 1. Continue to use ferric sulfate for coagulation. 2. Provide sufficient alkalinity to ensure coagulation ph is in the 5.5 to 5.7 range. 3. Assess the condition of the sedimentation basins. 4. Discontinue KMnO 4 addition at the reservoir PS. 5. Continue to feed KMnO 4 at the Lake Holt PS. 6. Use Ashland 851TR polymer to enhance turbidity removal. 7. Feed PAC upstream of rapid mix to provide additional contact time.

12 Chemical Systems Recommendations

13 KMnO 4 Recommendations: 1. Discontinue feed at Reservoir PS 2. Feed a maximum of 1 mg/l at Lake Holt PS 3. Required metering capacity of 10 gph

14 Powdered Activated Carbon (PAC) Recommendations: 1. Relocate PAC application to the raw water line just inside the fence to provide an additional 4.9 minutes of contact time. 2. Upgrade and use PAC system to address taste and odor events and high raw water TOC. 3. Replace the volumetric feeder, mix tank/mixer, rotameters and eductors, dust collector, and controls.

15 Coagulant-Aid Polymer 1. Replace existing liquid chemical feed system with a dry polymer batching and feed system (Ashland 851TR polymer). 2. Reuse existing hydraulic diaphragm metering pumps for feed of polymer solution.

16 Anhydrous Ammonia Recommendations 1. Continue to use existing bulk tank, vacuum regulator and injectors. 2. New automatically controlled ammoniators to enhance control of ammonia addition and monochloramine formation.

17 Sodium Hydroxide Recommendations: 1. New 10,000-gal bulk storage tank in the caustic containment area and two new transfer pumps. 2. New 700-gallon day tank located in the new chemical feed building. 3. Relocate existing metering pumps to new building and add a new spare pump. 4. Separate pre-filter caustic and hypo feed lines with separate rotameter panels to feed to the filters. 5. Provide a softening system.

18 Ferric Sulfate Recommendations: 1. New 14,000-gal RFP tank with two new transfer pumps 2. New 500-gallon day tank in new building 3. New 50-gph metering pump to serve as spare. 4. Construction of a new ferric sulfate containment area.

19 Ferric Sulfate and Caustic Containment Area 1. Construct a new ferric containment area to separate incompatible chemicals. 2. Install a new caustic bulk storage tank in the caustic containment area.

20 A new chemical feed building is recommended to house day tanks and metering pumps for ferric, caustic, and hypochlorite.

21 Sodium Hypochlorite Recommendations 1. Continue using the transfer pumps 2. Bulk tank has reached the end of the service life and SGWASA is planning to replace in the near future. 3. New 1,800-gallon day tank and metering pumps located in the new chemical feed building. 4. Relocate the existing metering pumps for feed to the chlorine contact chamber and pre-filter application points. 5. New pump for post-filter and new spare pump.

22 SCADA Evaluation

23 Existing system is not functional. The plant s existing instrumentation and controls also are largely not functional. Certain field instruments are not operational, and others provide suspect readings. Plant staff has performed with minimal instrumentation and automation, largely operating the plant and its processes manually.

24 Ensuring for continued DBP compliance, automated monitoring and control is critical. Provide a basic level of process control. Flow and level through the plant. Chemical feed systems are flow paced. Solids removal is automated. Upgrade and enhance instrumentation to provide real-time data to operators.

25 Capital Cost Summary

26 The total project cost for the recommended improvements is approximately $3.3 million. Cost Subtotal Construction $ 1,844,100 Contingency (30%) $ 553,200 Contractor O&P (15%) $ 359,600 Subtotal with Contingency and Contractor O&P $ 2,756,900 Engineering $ 496,200 TOTAL $ 3,253,100

27 Schedule Aug 8 Aug 21 Oct 10 Nov 28 Notice to proceed Begin bench-scale testing Present bench-scale testing preliminary results Submit draft report Dec 12 Present draft DBP and SCADA evaluation recommendations

28 Questions and Discussion

29 WTP Sludge Removal System and Dewatering Facility

30 Project Approach Documentation of Existing Conditions Site visit to WTP to review existing residuals treatment practices Site visit to WWTP to review existing rotary drum thickener Collect pertinent information to understand existing facilities configuration Complete Rotary Drum Thickener at WWTP

31 Project Approach Residuals Collection System Assessment Evaluate existing sludge scrapers and coordinate with manufacturers Recommend improvements to enhance reliability Develop concept-level capital costs Develop construction sequencing plan In Progress

32 Project Approach Residuals Production Estimates Collect and consolidate plant data Estimate existing residuals production In Progress Estimate future residuals production based on findings from DBP Reduction Evaluation (i.e. switch to ferric sulfate) Use production calculations to evaluate adequacy of existing residuals treatment and handling scheme Avg Flow Avg Loading Past (Alum) Future (Ferric) 936 lbs/day 1,205 lbs/day ~30% Increase

33 Project Approach Existing Sludge Holding Tank Thickening & Dewatering Alternatives 1. Convert tank to gravity thickener + Dewatering 2. Gravity Thickener + Dewatering 3. Relocate existing rotary drum thickener (RDT) + Dewatering Collecting sample to vet performance of RDT on WTP solids 4. Residuals lagoon In Progress 2-M Belt Filter Press

34 Schedule Aug 8 Nov 1 Jan 15 Notice to proceed Preliminary DBP strategy informs possible range of residuals production Submit draft report

35 Questions and Discussion