Metro Water Services On-Site Sodium Hypochlorite Generation
Looking for an alternative to provide safer disinfection technologies to Nashville’s Metro Water Services (MWS), SSR led a multidisciplinary, multi-consultant project team to evaluate options for the Omohundro Water Treatment Plant (OMO) and K. R. Harrington Water Treatment Plant (KRH). Based on operational and maintenance considerations, redundancy, source supply, and life cycle cost analyses, MWS identified the phased conversion of the two water treatment plants from gaseous chlorine to on-site-generated (OSG) sodium hypochlorite treatment plants as the preferred path of action.
The conversion from gaseous chlorine to OSG was a challenge. Both 90-million-gallon-per-day facilities were limited on available space, requiring a combination of new and repurposed facilities. Beginning in 2014, each facility began a phased approach to diluted bulk sodium hypochlorite. Phase One involved the construction of hypochlorite storage, dilution, and dosing facilities. MWS requested that the commissioning of these systems at each treatment plant be staggered so that the two facilities would not be going through transition at the same time. They also required a 30-day trial period prior to demolition of the gaseous chlorine facilities to become familiar with the new systems. In early 2016, the OMO facility was fully converted to sodium hypochlorite, with KRH converting later the same year. Phase one ended with the removal of the rail car and ton cylinders of gaseous chlorine obsolete gaseous chlorine being removed from both facilities.
Phase two of the project entailed the removal of the chlorinators at each facility, and their replacement with electrolytic on-site generation equipment. Three 2,400-pound-per-day generators were installed at each facility, making this one of the largest combined municipal bleach generation facilities in the United States.
The replacement OSG and dilution systems have provided not only MWS, but also the citizens and visitors to Nashville, a safer and more reliable disinfection system.
SSR managed the design and construction administration efforts for both plants. SSR provided all design services for the civil, process, mechanical, electrical, plumbing, and instrumentation and control facets at the KRH facility.