Patent ID: 8012758

Claim:
A method of measuring bulk microbiological activity and surface associated microbiological activity in a process stream comprising: a. connecting an apparatus to a process stream, wherein said apparatus comprises a flow cell containing a plurality of openings, wherein at least one opening is a flow cell inlet for fluid drawn from said process stream and at least one opening is a flow cell outlet for fluid exiting said flow cell, a DO probe attached to one of said openings, optionally an ORP probe attached to one of said openings, a cleaning device attached to one of said openings, optionally a first conduit attached to the flow cell inlet, optionally a second conduit attached to the flow cell outlet, and a valve associated with said flow cell; b. drawing fluid from said process stream into said flow cell; c. opening the valve of said apparatus to allow fluid to be drawn into said flow cell, d. measuring at least once the DO concentration of said process stream with said DO probe, wherein said DO probe is not cleaned prior to each measurement; e. cleaning the surface of said DO probe; f. measuring at least once the DO concentration of the fluid inside said apparatus with said DO probe wherein prior to each measurement said DO probe surface is cleaned; g. closing the valve of said apparatus to prevent fluid from being drawn into said flow cell; h. measuring at least once the DO concentration of the fluid inside said apparatus with said DO probe, wherein prior to each measurement said DO probe surface is cleaned; i. calculating a Δ DO reading between step (f) and step (h) and correlating at least said Δ DO with said bulk microbiological activity in said process stream; and j. calculating a Δ DO reading between step (d) and step (f) and correlating at least said Δ DO with said surface associated microbiological activity in said process stream.