Characterizing Microbial Water Quality in Reclaimed Water Distribution Systems

Historically, reclaimed water systems met water quality and public health related standards at the end of the treatment facility prior to entering the distribution system. However, water quality within the reclaimed water distribution system can significantly change and affect end uses due to changes in levels of color, odor, and biofilm growth. Operations staff need guidance to help them optimize the reclaimed water quality in the distribution system throughout the year. The objectives of this project were to: characterize the nature and extent of water quality deterioration in reclaimed water distribution systems, including microbial fouling, regrowth, impact to the end user, and impact on reuse and other related regulations; identify pertinent water quality issues in relationship to degradation as it is conveyed to reuse customers; develop general guidance for use by reclaimed water utilities in identifying and assessing problems; and provide options for controlling regrowth including regulating detention time, flushing, and optimization of disinfectants. The final report includes a summary of state reclaimed water regulations and federal guidelines, and other related regulations. The research team put together a final report that provides general guidance for use by reclaimed water utilities in assessing and solving potential problems. Guidance for operation, monitoring, and maintenance of reclaimed water systems to improve quality for end users. Biofilm control methods such as pipeline flushing, shock chlorination, and intermittent use of chloramine disinfectant are discussed. The research also addresses methods for identifying microbially induced corrosion issues and methods to optimize operations through the use of monitoring and modeling activities. Disinfectant residual criteria for reclaimed water systems are presented to assist system operators.