TROLL 9500 Operator's Manual - Geotech Environmental Equipment

Section 10: Monitoring Water Quality: OverviewWhen to Replace a SensorAfter a certain amount of use even a complete recalibration will notbe able to accurately calculate calibration coefficients. The slope willgradually become lower and lower. At this point the sensor should bereplaced. Specific slope guidelines for individual sensors are given inthe individual parameter sections below.Using a StirrerIn-Situ’s stirrer accessory provides continuous sample circulation oragitation, which can improve the performance of water-quality sensorsin a number of applications.Dissolved oxygen (DO) measurements drop in very stagnant waterdue to depletion of oxygen next to the membrane. A slight perturbationto the system will cause the DO measurements to return to normal.Stirring is recommended if the instrument is anchored to a fixed structurein stagnant conditions—for example, attached to a pier in a calmlake that has no underwater currents. If the wind is blowing and wavesare slightly moving the cable, then stirring is probably not necessary.ISE sensors in close proximity to each other can sometimes createinterferences. Constant stirring can enhance the performance of theISE sensors.Sample agitation can also help to improve sensor response timewhen water-quality conditions are subject to change (e.g., in a movingcontaminant plume) and can speed up temperature stabilization.Attaching the Stirrer for Field UseThe stirrer accessory is easily installed on the MP TROLL 9000. Seeillustration D earlier in this section.1. Remove the nose cone from the MP TROLL 9500. Leave therestrictor attached to the instrument.2. Screw the top of the stirrer (propeller end) to the stainless steelrestrictor in place of the nose cone.3. Start the stirrer; see Starting the Stirrer earlier in this section.The instrument is ready for use in stagnant water.Q:A:ReferencesHow can I find the serial number of a water quality sensor—pHfor example?The software can display the sensor serial number. Do this:1 Select pH in the Navigation tree2 Look at the information displayed The serial number isdisplayed in the Information pane on the right side of thescreen (or at the bottom on a PDA)Eaton, A.D., L.S. Clesceri, E.W. Rice, and A.E. Greenberg, eds.,Standard Methods for the Examination of Water and Wastewater,21st edition, Washington, D.C.: American Public Health Association,American Water Works Association, and Water EnvironmentFederation, 2005.A Fish Farmer’s Guide to Understanding Water Quality. LaDonSwann, Dept. of Animal Sciences, Illinois-Indiana Sea GrantProgram, Purdue University. On the web at AquaNIC (AquacultureNetwork Information Center), aquanic.org.Rundle, Chris C., A Beginners Guide to Ion-Selective ElectrodeMeasurements. Nico2000 Ltd., London, UK. On the web at www.nico2000.netWater on the Web (WOW). University of Minnesota project initiallyfunded by the National Science Foundation. On the web at wow.nrri.umn.eduWater Quality Sensor Pressure RatingsPressure Rating Usable DepthSensor PSI Meters FeetpH 300 210 692pH/ORP 300 210 692Conductivity 350 246 807D.O. polarographic* 350 246 807Turbidity 350 246 807Wiper 350 246 807Chloride 100 70 231Ammonium 20 14 46Nitrate 20 14 46RDO exceeds rating of the TROLL 9500* Submersion and retrieval at up to 4 feet per second.TROLL 9500 Operator’s Manual 650095110 rev. 007 01/09