In-­‐‑Tank  Aeration  to   Reduce  Disinfection   Byproducts Amy Kramer, P.E., Engineering & Distribution Manager Mary Carol Wagner, Water Quality Manager Rick Gell, P.E., Water Practice Leader - O’Brien & Gere Northern  Kentucky  Water  District  Facts §  Service  Area  300  sq.  mi. §  Population  Served  300,000 §  Over  80,000  Active  Accounts §  3  Treatment  Plants §  Average  demand  ~29  MGD §  Maximum  demand  ~  49  MGD §  3  Raw  Water  Intakes §  20  Storage  Tanks §  16  Pump  Stations §  1,300  Miles  of  Main §  Campbell  County §  Kenton  County §  Wholesale  to  portions  of  Boone,   Grant  and  Pendleton  Counties Treatment  Plants §  Ft.  Thomas,   44  MGD §  Memorial   Parkway,   10  MGD §  Taylor  Mill,   10  MGD Disinfection  Byproducts •  Organics not removed during treatment form byproducts - trihalomethanes (THMs) and haloacetic acids (HAAs) •  Disinfection byproducts regulated under the Disinfection Byproducts Rule •  Stage 2 Rule effective April 1, 2012 o  Locational Running Annual Average (4 quarters) •  THMs = 80 µg/L •  HAAs = 60 µg/L •  8 compliance sites in distribution system o  Each site must comply with Maximum Contaminant Level (MCL) Advanced  Treatment •  Added granular activated carbon July 2012 at FTTP and MPTP •  TMTP – no GAC •  Finished water TOC target of 1.25 mg/L or less •  8 contactors at FTTP •  4 contactors at MPTP •  React each contactor every 12 - 18 months •  Estimated annual reactivation cost $ 2.3 million for MPTP and FTTP Organics  and  DBPs 2013  Finished  Water  Results Plant Range  of  TOC,   Average  TOC,   Range  of  THMs,   mg/L mg/L µμg/L MPTP 0.22  –  1.22 0.65 <1  –  23 FTTP 0.30  –  1.71 0.84 <1  –  30 TMTP 1.45  –  2.36 1.85 9  -­‐‑  33 2013  Distribution  System  Results DBPs LRAA Quarterly HAAs,  µμg/L 13  –  19        9  –  29 THMs,  µμg/L 17  –  38        2  -­‐‑  80 DBP  Data  Review •  LRAAs well below the MCL o  GAC and blending FTTP/TMTP effective for meeting DBP Rule •  Goal - keep all quarterly samples below MCLs •  Look for ways to reduce DBP formation in system •  Use a phased approach o  Reduce detention time o  Review booster chlorination o  Enhance tank mixing and aeration Optimization  Strategy •  Lower Detention Time - Flushing o  Installed 11 automated flushing devices •  Improve chlorine residual •  Hopefully lower DBPs o  Conduct routine hydrant flushing •  Review Booster Chlorination o  Boost at 4 locations in the blended FTTP/TMTP system •  Chlorine no longer boosted at 2 other sites post-GAC o  Need chlorine to maintain residual - cannot eliminate boosting •  Enhance Tank Mixing and Aeration o  On-going effort TARGET  AREA  FOR  STUDY  FOR  THM  REMOVAL 8/13   8/13   THMs   THMs   BOOSTER  CHLORINATION 66  µμg/L 80  µμg/L AUTOMATED  FLUSHING