AWWA C671-16 pdf download.Online Turbidimeter Operation and Maintenance
AWWA C671-16 can be referenced in documents for purchasing online turbi- dimeters, can be used as a guide for verifying the accuracy and precision of online turbidimeters, or can assist utilities in establishing online turbidimeter O&M pro- cedures. Te user should ensure the environmental conditions of the application match the manufacturer-specifed conditions and requirements for the analyzer. Te stipulations of this standard apply when this document has been referenced and then only to online turbidimeters used in the treatment and monitoring of potable water, reclaimed water, or wastewater efuent.
The optical property expressed as turbidity is measured by the light-scattering efect of suspended constituents within a water sample; the higher the quantity of scattered or attenuated light, the higher the turbidity (Standard Methods [APHA, AWWA, and WEF]). Current methods for measuring turbidity are based on a comparison of the light scattered or attenuated by the sample with the amount of light scattered or attenuated by a reference suspension under the same environmen- tal conditions. Te common components for turbidimeters include the following:
1. Light source: Te light source used to illuminate the sample may be a polychromatic (incandescent) light, laser diodes, or light-emitting diodes (LEDs). Specifc light source characteristics may be required by specifc regulation in some areas.
2. Sample cell or chamber: The sample cell shall allow incident light to pass through the sample and scattered light to pass to the detector.
3. Light detector(s): Light detectors shall be located to detect light scat- tered by particulate material suspended in the sample cell. Te spectral response of the detector should match the spectral output of the incident light source to gener- ate a usable signal with the desired sensitivity.
4. Geometry: Te optical geometry will have the primary detection angle at 90 degrees relative to the centerline of the incident light beam. Tis geometry is typically labeled as nephelometry. Figure 1 shows the common optical geometry for a nephelometer. Te preferred expression for turbidity measured by using an instrument of this design is the nephelometric turbidity unit or NTU (ASTM D6698). Nephelometers can detect light scattered by particles in the 0.1- to 1-µm size range and wider, with a peak response at about 0.2 µm.
5. Electronic hardware and software: The instrument shall have the elec- tronic hardware and software to manage the optical output of the light source, to convert detector response to a turbidity measurement, and to transmit or display the result.AWWA C671-16 pdf download.