Water Treatment Information

The Walter J. Sullivan Water Treatment Facility at Fresh Pond produces drinking water from the raw water of Cambridge reservoir system.   The dinking water from the plant is provided to the City of Cambridge.  The plant is located on the shore of Fresh Pond at 250 Fresh Pond Parkway. The staff includes a Production Manager,an Instrumentation and Maintenance Manager, and eight fully licensed Drinking Water Operators classified as Team Leaders and Plant Operators.

The plant includes various intake structures and aeration equipment that extend into the pond.  The rest of the treatment process is contained inside the Walter J. Sullivan Water Treatment Facility.  The raw water is treated to State and Federal drinking water standards. 

The processes that accomplish this include:

Aeration: The bubbling of air from the bottom of the pond keeps the waters of Fresh Pond mixed, preventing stratification by temperature.  The mixing prevents and controls the release of manganese into the water.

Pre-treatment: This includes the pre-oxidation, rapid mix, coagulation and dissolved air flotation (DAF).  These processes with the application of ozone and a coagulant chemical, alum, remove: manganese, natural color, particles, algae, protozoa, viruses and bacteria from the water.

Intermediate Ozone:  In this step fine bubbles of ozone are dissolved into the water and disinfect the water by killing bacteria, viruses, and protozoa.  The ozone in generated in the plant and introduced into the water in a series of chambers that allow contact and mixing of the ozone with the water.  At the end of this process all the ozone introduced is removed from the water.

Granular Activated Carbon (GAC) Filtration:  This step follows the ozone application to help remove any organic compounds that may have been rendered biologically active or useable by the ozone step.  The filters further polish the water by removing additional particles, color and protozoa from the water. 

Chlorination:  The chlorination after the filters kills bacteria that may develop during the normal operation of the filters.  The chlorination step also provides a level of redundancy in the overall disinfection process.

Post Treatment Chemical Addition:   This includes the adjustment of pH for corrosion control, the addition of fluoride for dental health, and chloramination to provide a disinfection residual in the distribution system.