Water Management Services, LLC

Engineering · Planning · Operations · Rate Studies

Columbia Power & Water Systems (CPWS)
Water Treatment Plant Additions and Modifications

As water regulations continue to evolve, CPWS found that traditional treatment techniques were not adequate for compliance with the Stage 2 Disinfection By-Products (Stage 2 DBPR) and the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). In addition to compliance with these impending regulatory changes, CPWS also wished to evaluate the benefit of replacing gas chlorination with onsite sodium hypochlorite generation.

Water Management Services personnel conducted a nine month treatability study to evaluate the formation potential for Disinfection By-Products (DBP) and to evaluate various treatment techniques for the removal of DBP precursors.  Additionally the treatability study evaluated the treatment techniques for removal/inactivation of cryptosporidium and onsite sodium hypochlorite generation. The results of the treatability study provided the basis of design for the additions and modifications to the CPWS water treatment plant.

Water Management Services petitioned the Division of Water, on behalf of CPWS, for an extension of the Stage 2 DBPR regulatory deadline. Water Management Services extensively researched the requirements for such an extension and thoroughly documented the request. Subsequently, CPWS received a two-year extension for compliance with the Stage 2 DBPR.  This was the first extension ever granted by the Division of Water for a federal drinking water regulation. The extension has allowed the water system to maintain compliance with DBP regulations while the capital improvement project is completed.

With the completion of this project, CPWS has the necessary facilities to ensure continued compliance with existing regulations and the flexibility to adapt to future regulatory changes. The results of first quarter mointering found that DBP residuals in the water system were  90% lower than those of the IDSE study. 

Project Highlights

  • Conducted 9-month onsite treatability study
  • Obtained an extension for compliance with the Stage 2 Disinfectants and Disinfection By-Product Rule 
  • Improvements include onsite sodium hypochlorite generation
  • Improvements include UV for cryptosporidium inactivation
  • Improvements include GAC beds for removal of DBP precursors
  • Improvements include  basin covers to prevent algae growth
  • Improvements will achieve and enable continued compliance with drinking water regulations