The Middlesex Water Company (MWC) Park Avenue Well Field located in central New Jersey was comprised of a system of 17 wells, each with different levels of Radon and Volatile Organic Compounds. Measurements of levels moved MWC to engage the services of BS& J, Inc. to complete an extensive laboratory test program for the well field and to examine alternatives for the removal of trichloroethylene (TCE), tetrachloroethylene (PCE), and radon from the 17 wells.
The study recommended the use of packed tower air stripping. In May 1993 construction of this state of the art unmanned computer controlled air stripping facility was completed and all 17 wells were brought on line. Water quality test results from the facility indicate removal of VOC’s and radon to concentrations less than detectable, providing MWC a reliable, efficient and valuable water supply.
The Central Treatment Facility (CTF) consisted of three packed tower air strippers each designed to treat more than 5 MGD. Each air stripper is approximately 12 ft. in diameter and 27 ft. high.
The 3 towers were constructed above a reinforced concrete clear well from which treated water flows to a 2 MG storage reservoir. The reservoir provides MWC the necessary chlorine contact time required after the treated water leaves the air strippers and before entering the distribution system and the added benefit of increased storage. The CTF also consists of three air blowers, five vertical turbine finished water pumps capable of delivering 16 MGD flow, chemical feed, and standby power system. The raw water is somewhat hard and a chemical treatment was recommended to prevent calcium carbonate scaling in the stripping towers. Polyphosphate, a sequestering agent, is used.
The CTF was also equipped with an unmanned computer based Supervisory Control And Data Acquisition (SCADA) system. This system allows full local control from the CTF in South Plainfield, NJ and full remote control and monitoring from MWC’s surface water treatment plant, the Carl J. Olsen Treatment Plant (CJOTP). The computer systems at both facilities communicate using a solid state, pulsed, multiplexing system via leased telephone lines. Remote terminal units and modems were installed at two of the more distant wells and the remaining wells were hardwired to allow the complete system to be controlled from the CJOTP. The system uses CAD-like software that allows the operator to design, configure, monitor, tune, modify and document process activities.
All computer controlled operations are available for selective manual control through the computer by the CJOTP operator with alarms and pre-sets fully operational to guide the operator.