Automatic silt density index apparatus

An apparatus for monitoring the silt density index of a liquid feed stream flowing to a reverse-osmosis membrane comprising:

• a filter unit through which at least a sample of the feed stream flows, said filter unit comprising a plurality of filter portions disposed hydraulically in parallel, and further comprising solenoid valves, in signal communication with said microprocessor-based controller, for selectively directing the sample feed stream to selected ones of said filter portions, whereby the sample feed stream is serially directed to successive ones of said filter portions;
• a feed conduit for conveying to said filter unit the sample of the feed stream to be monitored;
• a pressure regulator in said feed conduit for regulating a minimum pressure of the sample feed stream upstream of said filter unit;
• a flow controller and a flow sensor for regulating a constant discharge of said sample feed stream in said conduit to said filter unit;
• at least one pressure sensor for measuring the pressure of the sample feed stream on a side of said filter unit;
• and
• a microprocessor-based controller adapted to receive and process signals from said at least one pressure sensor to determine a rate of change in the pressure of the sample feed stream;
• wherein said pressure sensor signals said microprocessor-based controller when a selected maximum pressure is sensed, and said microprocessor-based controller initiates the closure of a first one of said solenoid valves and initiates the opening of a second one of said solenoid valves, in response to the signal from said at least one pressure sensor;
• and wherein further the rate of change in the pressure of the feed stream across successive ones of said filter portions provides data respecting the fouling rate of the reverse-osmosis membrane.