The University of Florida is seeking companies interested in a system for controlling the chlorine concentration in the water effluent from wastewater treatment plants to better comply with Environmental Protection Agency (EPA) regulations and to reduce operational costs. This technology automatically regulates the time that the chlorinated water spends in the contact basin effectively compensating for the variability of residence (detention) time caused by inevitable daily and seasonal fluctuations in the inlet flow rates received by the plant. As a consequence the technology avoids the unacceptable discharge of under chlorinated effluent that is typically caused by temporarily low inlet flow rates. In addition the system avoids the discharge of costly and potentially hazardous discharge of over chlorinated effluent caused by sporadically high inlet flow rates. The automatic control system also eliminates the need for the common operational practice of injecting an overdose of disinfectant to compensate for the unpredictable arrival of spikes in inlet flow rate. This technology is an automatic control scheme that uses the residence time as the controlled variable and utilizes a moving weir as the actuator. Whether the control algorithm is designed as a standard PID or as a novel model-based ratio controller the liquid volume held in the contact basin and therefore the residence time of the fluid in the basin is manipulated as a function of inlet flow rate to ensure that the chlorinated water is retained in the basin for approximately the same amount of time regardless of inlet flow conditions. The automatic manipulation of the residence time causes dramatic improvements in the control of chlorine concentration reducing oscillations and transients away from the specified targets. Application: Method for controlling chlorine concentration in the effluent from wastewater contact basins.
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