The pretreated raw water is boosted in pressure to 150-psi for the Biscayne water and 250-psi for the Floridan water and is then passed through the membranes and sent to post-treatment. The water which does not pass through the membranes is called concent rate and is rejected to the waste stream. The concentrate is as the name implies, it is a concentrated solution of the minerals from the raw water. The concentrate is disposed through a pipeline to the Hollywood Regional Wastewater Treatment Plant. When utilizing the Biscayne aquifer water, about 10% of the water treated is disposed as concentrate and with the Floridan aquifer water, about 20% of the water treated is disposed as concentrate.
After degassification, the water is treated with caustic soda to increase the pH, then disinfected with chlorine and ammonia, and finally, fluoride is added to prevent tooth decay. During this post-treatment process the membrane treated water is also blen ded with water treated by the lime softening treatment system. This blending provides for a well balanced finished water product that is clean, safe, and sure.
Since the membrane process to treat water is complex, a state-of-the-art computer control system is utilized to monitor and control every stage of the treatment process. The new control room features two operator work stations and two main central computers. The two main central computers process all the information coming in and going out of the various treatment components. With this system the plant is totally automated and can be run with one operator.
In addition to the new plant controls, provisions for the old plant were also included in the new system to allow monitoring and operations of the old plant in conjunction with the new membrane plant. The capability is also available for the new control system to allow monitoring of the plant operations from off-site points as well as being able to monitor and control other portions of the utility system, such as the wastewater treatment plant. To the City this capability could prove invaluable during a hurricane when access is limited to the wastewater treatment plant.