The Camrosa Water Reclamation Facility (CWRF) provides recycled water for crop irrigation but was limited in the volume of water it could produce because the chlorine contact basins, which pre-dated the rest of the treatment facility, were not large enough to meet the default regulatory minimum contact times (CT). MWH, now part of Stantec, developed a testing protocol to investigate whether the existing chlorine contractors could be re-rated to accommodate higher flows while maintaining compliance under California Title 22 recycled water standards. The team involved California Division of Drinking Water regulators from the beginning of the process to gain their approval of the test methods. MWH worked with the CWRF operators to configure the plant for experiments at full scale, and conducted a suite of testing that included fluoride tracer studies to measure the actual contact time; chlorine degradation studies to set a dosing strategy; and virus seeding studies with MS2 bacteriophage to observe the rate and extent of disinfection.
The study found that the plant will achieve full compliance with Title 22 requirements at significantly higher flows and lower CT than allowed under the current permit. This is the first project that employed full-scale virus seeding studies to gain regulatory approval to operate at reduced CT. The study resulted in significant cost savings for the District – in order to increase the capacity of their plant, they will no longer have to construct larger chlorine contact basins.