MANAGING DROUGHT IMPACTS ON WASTEWATER COLLECTION SYSTEMS

Transcription

1 MANAGING DROUGHT IMPACTS ON WASTEWATER COLLECTION SYSTEMS Northern California Pipe Users Group 24 th Annual Sharing Technologies Seminar February 18, 2016 LANI GOOD, PE COURTNEY HALL, EIT

2 Acknowledgements

3 Presentation Outline Current Drought Conditions Drought Impacts on Wastewater Systems Potential Solutions to Collection System Impacts & Agency Examples Alternative Water Supplies Water-Efficient Maintenance Equipment & Methods Odor Control Solutions

4 Current Drought Conditions

5 Historic Statewide Precipitation Patterns Historical record shows cyclical drought/flood Current drought severe in both intensity and length Highly randomized: does not mean several more years of drought are not possible

6 California Water Usage & Population ( ) Water Usage per Capita is NOT increasing California population is continually increasing, bringing increased demand

7 Drought Impacts on Wastewater Systems

8 FLOW RATE / BOD Wastewater Treatment Impacts Lower influent average day flows Higher influent contaminant concentrations Potential compliance issues for untreated contaminants (e.g. salts) Higher salt water intrusion in coastal areas Increased demand for recycled water production WWTP INFLUENT TRENDS Influent Flow Rate Influent BOD TIME

9 Collection System Impacts Lower average day flows = lower flow velocities Higher rate of sediment deposits - especially in flat sewers and sags Increased odor complaints Increased corrosion potential

10 Collection System Impacts Increased root intrusion Roots compensate for the lack of soil moisture to keep tree evenly anchored Root sizes increase to obtain more water and minerals

11 Potential Solutions to Collection System Impacts

12 Alternative Water Supplies Use of non-potable water supplies, including recycled water, for hydro-flushing operations Challenges: Availability of supply Increased refill drive times Particulates can sometimes clog equipment Turbidity levels: Recycled water = 2.0 NTU (particles up to 100 micron) Drinking water = NTU

13 Agency Example Recycled Water Supply Rental tank at Corp Yard, contract water hauler from the SJ/SC Plant Hydro-trucks fill first tank of the day and after lunch Required Y-strainer on tank discharge, and air gap bypass connections Estimated 45% reduction in potable water use, No expected loss in crew productivity $45K-$50K for 6-month pilot ($7,500/month) Exploring permanent solutions: Purchase tank Use staff to haul water Advocate for permanent recycled water supply

14 Agency Example Recycled Water for Groundwater Recharge 250 Influent Flows 200 Total to OCWD Jun-14 Sep-14 Dec-14 Apr-15 Jul-15 9% lower average day wastewater flows Increased recycled water delivery to OCWD for groundwater recharge to help combat increased salt water intrusion rates

15 Agency Example Non-Potable Well Supply City of Burlingame rehabilitated and redeveloped 120-gpm irrigation well for: Sewer hydro-flushing Street sweeping Park irrigation

16 Agency Example Non-Potable Well Supply South Placer MUD uses a non-potable well located at the wastewater treatment plant to: Fill hydro-trucks at least once per day and anytime a crew is at the treatment plant Irrigate District treatment plant landscaping

17 Agency Example Recycled Water Supply Using recycled water for 25-35% of hydro-jetting CCCSD hydrants in Martinez and Pleasant Hill, plus 5 DSRSD hydrants in Dublin/San Ramon First hydro-truck fill of the day is CCCSD RW for Walnut Creek/Lamorinda Prepared to rent two temporary tanks and have CCCSD RW hauled to Walnut Creek (if required by EBMUD) $10-15K/month for equipment and hauling 50% reduced hydro-crew productivity due to increased refill drive times

18 Agency Example Alternative Water Supply Vallejo Sanitation (VSFCD) is reusing City of Vallejo hydrant flushing water District-owned tanks store water at multiple locations Sewer maintenance hydrotrucks fill when nearby We recognize it s pretty hard to justify 3,000 gallons going down a gutter, when we re telling the neighbors they can t water their lawn. - David Kleinschmidt, City of Vallejo Public Works Director

19 Water-Efficient Maintenance Equipment & Methods Mechanical rodding (no water) vs. hydro-jetting Chemical root control vs. higher-frequency hydro-root cutting Water-Efficient Jetters and Nozzles Decreased hydro-jet flowrate, increased jet pressure

20 Fluid Horsepower Water-Efficient Jetters and Nozzles Benefits: Less water consumption Engine End of Hose Reduced maintenance costs Fewer fill ups = less drive time Tier 3 Nozzle (98%) Tier 3 Nozzle Tier 2 Nozzle Tier 1 Nozzle Improved safety 20 Fewer blown toilets Reduced noise levels Flow (GPM)

21 Agency Example Water-Saving Equipment New nozzles on standard combo truck Reduced from 80 gpm to 65 gpm Harben Skid Jetter for root cutting 600-gallon tank, psi 6 8 pipe only

22 Water-Efficient Maintenance Equipment & Methods Predictive Maintenance Triggers Video Inspection Acoustic Blockage Detection

23 Predictive Maintenance Methods: Video Inspection Zoom-Camera or CCTV before cleaning Only schedule pipes with grease or debris for cleaning CCTV during cleaning using camera nozzles Clean sections of pipes that need it; confirm that blockage is cleared

24 Agency Example Camera Nozzle Pipe Hunter with Jet-Eye Nozzle No water on pull-back unless needed psi 50-75% water savings ½ hose is lighter, less water needed to jet up the pipe If heavy roots, mark exact footage, remove camera nozzle, add root saw blade, and CCTV after to confirm

25 Agency Example Camera Nozzle CCTV-triggered High Preventative Maintenance Frequency Lines Camera Nozzle System Estimated 30-40% decrease in the cleaning frequency of hotspots

26 Agency Example CCTV-Triggered Cleaning CCTV inspections trigger cleaning: Changed operations from: 2-hydro-crews and 1-CCTV crew To: 1-hydro-crew and 2-CCTV crews One CCTV crew codes defects One CCTV crew flies-through ahead of hydro-crew to identify cleaning needs

27 Agency Example CCTV-Triggered Cleaning Only clean sewers if needed: CCTV inspection triggers cleaning Expected to reduce cleaning by approximately 25-30% Projected to save 5,600 gallons/month

28 Predictive Maintenance Methods: Acoustic Blockage Detection Signal is weakened by obstructions such as roots, grease, debris, or structural problems such as offset joints SL-RAT provides 1-10 score to quantify level of blockage in 6 to 12 sewers less than 800 feet long

29 Agency Example Predictive Maintenance Normal maintenance practices include: 50% rodding, 50% hydro-jet Use of SL-RAT for predictive maintenance for routine cleaning (5-year cycle) in one basin for the past two years

30 Odor Control Solutions Standard Manhole Hanging Odor Block Activated Carbon Insert Sealing Drop Manhole Vortex Flow Insert

31 Odor Control Solutions Pump Station Wet Wells Activated Carbon Aeration Chemical/Biochemical Addition Bioscrubber Biofilter

32 Concluding Thoughts: Engineering Support for Collection System Maintenance Documentation of existing practices Tracking and reporting of effectiveness statistics Evaluation of emerging technologies and equipment Camera nozzles, low-flow hydro-jetters, recycling vactors, etc. Pilot testing cleaning effectiveness of lower flow rates/nozzle setups Development of field charts/tables Hose, nozzle, flow rate relationships, odor issue tracking

33 QUESTIONS? LANI GOOD, PE (925) COURTNEY HALL (530)