EVALUATION OF OPTICAL-DETECTION METHODS FOR WATERBORNE SUSPENSIONS

Turbidimeters and optical particle counters (OPCs) are used to monitor particulate matter in water. The response from these instruments is g overned by the optical properties of the suspension and the instrument design. The recommended design criteria for turbidimeters allow for l arge tolerances that lead to variations in measurements from different instruments. OPCs provide size-specific information but may inaccurat ely size microorganisms or particles having optical properties differe nt from those of the calibration particles. The authors evaluate the e ffects of optical design parameters in turbidimeters and OPCs. Perform ance data from two OPCs are presented. A multiple-angle Light-scatteri ng method was developed to obtain ''optical signatures'' from suspensi ons of monodisperse spheres and several micro organism is elates. Such ''signatures'' provide more optical information on waterborne particl es and may also be used to identify specific types of microorganisms i n real time.