Patent ID: 7303685

Claim:
A method of automatically adjusting polymer feedrate in a sludge dewatering process in which filtrate captured from a gravity belt thickener and generated when the process is operating under optimum conditions exhibits a normal cationic charge measurable, as is the filtrate's charge generally, with a streaming current monitor, which comprises: (a) converting images from a video camera focused on a fixed portion of the thickener's belt into single numbers known as “camera readings”; (b) simultaneously monitoring the streaming current of filtrate from the dewatering process; (c) determining, whenever the “camera readings” begin to deviate from a “camera reading” setpoint by a predetermined threshold, whether the filtrate charge is more positive than the normal cationic charge; (d) incrementally resetting the polymer feedrate in such a direction as to restore the normal cationic charge of the filtrate; and (e) updating the streaming current setpoint which is used to adjust the polymer feedrate except during a “camera reading” excursion when the “camera readings” deviate from the “camera reading” setpoint by at least the predetermined threshold, the updated streaming current setpoint being set equal to the streaming current value measured immediately after each such “camera reading” excursion.