Abstract
The nonlinear dose controller is being designed for plants with high flow rates. The previous chemical doser design requires that the alum flow be laminar. The Linear Chemical Doser uses the relationship between laminar flow and major losses in the doser tube to maintain a constant chemical dose with varying plant flow rates. For high plant flow rates, the flow rate of alum will be turbulent. When the flow in the tube is turbulent the linear relationship no longer exists and a nonlinear dose controller is necessary to maintain a constant chemical dose with variations in flowrates. Furthermore, headloss through the flowcontrol module is excessiviely high.
The nonlinear doser uses an orifice to control the relationship between changing plant flow rates and chemical dose. The weir entering into the rapid mix is also an orifice and the plant and chemical flows vary in direct proportion. Design work is being performed to determine if this idea is feasible. The relationship between chemical dose and turbidity will be changed manually as it is in the linear doser.
Since the focus of the CDC team was shifted to design, this aspect of the project has been put on hold temporarily.