Standard Operating Procedures for Surface Water Sampling

STANDARD OPERATING PROCEDURES FOR SURFACE WATER QUALITY SAMPLING(Signal Average on) mode averages 10 measurements every 1.2 seconds which compensatesfor measurement fluctuations caused by the drifting of sample particles through the lightpath. After 22 seconds, the average of the 10 measurements is displayed.5. Record the displayed reading and measurement type onto the Field Data Sheet.6. For very turbid waters, the meter may display a flashing "1,000" value or E-3 error message.This indicates that the turbidity value is greater than 1,000 NTUs. There are two optionswith this condition: 1) perform a dilution, or record the results as >1,000 NTU. Note thison the field data sheet. Performing the dilution will give a more accurate turbidity value.7. Add deionized water to the sample vile when sampling is complete.3.1.3.1 Performing a Dilution for Turbidity1. It is recommended that a dilution factor (DF) of 10 be used for the turbidity calculation.The DF is the multiplier for the meter reading. For example, if the operator were todispense 9 mL of deionized water into a 10 mL graduated cylinder and 1 mL of samplewater, for a total of 10 mL, the DF is 10 (a ratio of 9:1); therefore, the turbidity value is themeter reading times 10.2. For samples that are extremely turbid, it may be necessary to make more than one dilutionto obtain a meter reading less than 1,000. For multiple dilutions, the procedure is thesame as described above; however, for the second dilution, the 9:1 diluted sample becomesthe sample to be diluted. If this is the case, and a 9:1 dilution is performed a second time,the DF is 100 (DF of 10 for the first dilution and DF of 10 for the second dilution). Theturbidity value is simply the meter reading times 100.3.1.4 HACH DR/700 COLORIMETER FOR CHLORINE ANALYSISThis procedure describes how to measure free and total chlorine with the Hach DR / 700Colorimeter (Hach Company 1993).3.1.4.1 Field Procedure for Measuring Free Available Chlorine1. After powering on the instrument, a six digit number, such as 52.05.01, will appear at thebottom of the display window. This is the number of one of several filter modules that arefactory installed. The filter module number required for the free chlorine analysis is52.07.1. If a number other than the free chlorine module is displayed, press the up arrowkey, in the edit box, until the correct number appears.2. Inspect the sample vials provided with the meter for any discoloration of the glass surfaceor any evaporate remaining from the last analysis. The vials should have been thoroughlywashed with a chlorine free detergent and rinsed with deionized water before field use.3. Triple rinse the vials with sample water and fill a 25 mL vial with sample. Check sampleacidity with pH paper. pH needs to be between 6 and 7. If pH >7, add one drop ofsulfuric acid solution and measure pH again. Repeat until pH is between 6 and 7.4. Pour 10 ml of solution into 2-10 ml vials. Place one vial into the cell holder and pressZERO (display will count down). Add the contents of one DPD Free Chlorine PowderPillow into other vial and shake for 20 seconds. Immediately place vial into cell holder andpress READ. Display will count down then show result. Record result.REVISED SEPTEMBER 2012 39