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Step 2: Placement

Placing an Optical Brightener sampling device into a stream

Optical Brightener sampling is best suited for storm drains, pipes, and small streams. Avoid placement in larger bodies of water such as ponds, lakes, rivers, or estuaries, as the larger volume of water contained in these systems will likely dilute the concentration of Optical Brightener to such a degree that it can not be qualitatively detected.

In open pipe or stream sampling, the rigid vinyl coated sampling device is secured by an attached monofilament fishing line that is tied at the other end to either a branch, a rock, or an aluminum spike.

In sampling catch basins, the plastic net bag is lowered into the catch basin by use of monofilament fishing line that is tied several times to the top of the bag. The other end of this monofilament line is tied to a craft (popsicle) stick that is then wedged into the side of the grate cover. The monofilament line should be of sufficient length so that the bag will be suspended within the flow of water.

Properly placed rigid sampling devices are almost invisible to the casual passerby. Close attention must be paid to the exact location where they are placed or they may be difficult to retrieve.

Placing an Optical Brightener sampling device into a catch basin

The Optical Brightener sample is generally exposed for 7 days. This is done for a variety of reasons.

Usually a volunteer(s) will have the same time off from one week to the next. This time frame also allows sufficient time for laundry to be done in the event one is monitoring a direct discharge from a single residence. If background interference hinders the sample from being read (eg. rust or sedimentation) then the length of time the sample is exposed can be shortened. If the result is repeatedly inconclusive (eg. retest) then the time exposed can be lengthened