CHAPTERS:An Optical Brightener Handbook
Step 1: Getting Started
A. Sampling Plan
A sampling plan should be conducted before any sampling has begun. The following are special considerations that should be taken into account when formulating an Optical Brightener Sampling Plan.
1. Combining Optical Brightener sampling with other data
One should be very careful in drawing conclusions from Optical Brightener sampling alone. Optical Brightener sampling is infinitely more accurate and therefore much more useful when it is part of a larger sampling program. When conducting Optical Brightener sampling for marginal or failing septic systems, it is recommended that the monitoring plan also include information on:
a.) Rainfall - Quite obviously, there are fewer potential sources of contamination during dry weather than during wet weather. Rainfall data is therefore vital in being able to pin-point a source(s).
b.) Bacterial Sampling- Because Optical Brightener sampling only provides presence/ absence data, it is important to remember that in many instances, bacterial sampling is necessary to provide quantitative results about a pollution source. Quantitative results are required to determine the concentration of pollutants in a water sample to evaluate the relative contribution of a pollution source to water quality problems and to help guide pollution remediation and enforcement decisions.
c.) Flow data - Flow data is vital information in monitoring as well as in remediation because:
- Without water as a transport vehicle, waste water has no way of reaching and then impacting receiving waters from upland sources.
- Volume flows are needed when calculating bacterial loading. Bacterial loading is calculated by measuring flow in gallons per minute, the number of bacteria in a 100 ml portion taken from that source, and entering this information into the formula: Bac/day = bac x Q x 54800 (where bac= bacterial concentration per 100ml of water and Q is gallons per minute) Kittrell, 1969. Bacterial loading calculations are used to figure the total number of bacteria per day that is being contributed by a source (or sources) to receiving waters and is critical in being able to compare the relative contribution of pollution sources. (As an example: a site which has a bacterial count of 240/100ml and a volume of 100 gallons per minute would have ten times the bacterial loading as a site that has a count of 2,400/100ml and a volume flow of only 1 gallon per minute.)
- Sometimes rainfall and high groundwater can dilute Optical Brightener dye to such a degree that it can not be detected through qualitative sampling.
- By profiling dry weather flow data, one is able to calculate periods of seasonally high and seasonally low groundwater tables.
- Because a high water table can sometimes cause substandard on-site septic systems to fail, there are instances where a sample will be repeatedly negative during low groundwater periods and yet positive during periods of high groundwater.
- It is advantageous to take flow measurements just prior to placement of the rigid O.B. sampling device.
d.) Field Observations- Probably the most essential of all monitoring programs as well as the most difficult to quantify into a database. Some of the more common field observations are:
- Noting the presence of waterfowl or other animal activity.
- Suspicious flows that might indicate either surface outbreak of an on-site septic system or break in a sewer line.
- Unusual growth of algae or other wetland plants that might indicate nutrient loading.
