CHAPTERS:An Optical Brightener Handbook
Step 5: Data Interpretation
Optical Brightener results, especially when combined with other information can be an invaluable tool in identifying and locating sources of waste water pollution. The table in Appendix C, which is based on over 1,000 O.B. samples collected in Gloucester demonstrates the many ways this data can be utilized. Appendix B is a breakdown of all the results from those samples in Gloucester and is probably representative of what one might expect in a watershed based approach to a sampling program. The following are examples of case studies which demonstrate some of the different ways that Optical Brightener sampling has been used.
A. Storm Drain Cross-Connection - In Ipswich during routine storm drain monitoring, a sampling site repeatedly tested positive for Optical Brightener and yet parallel bacterial sampling indicated the site was relatively free from dry weather fecal coliform bacteria. When the upstream portion of this drainage system was subsequently sampled through use of Optical Brightener, a direct discharge from a washing machine was found connected into the storm drain. The homeowner had separated the laundry waste from his septic waste in an attempt to reduce flow to a very stressed septic system.
B. Sewage Exfiltration - In a nearby City, a local monitoring group found extremely high fecal coliform levels in a storm drain that discharged into the harbor. Since the City was totally sewered, it was first thought that the source of bacteria must be non-human in origin. Optical Brightener sampling was then conducted at this site and results were consistently positive. After tracing the Optical Brightener through the street drain system, the group located the source of the problem, a leaky sewer pipe. Similar work done within this City identified several similar cases of sewer system exfiltration and even entire City streets in the older sections of town which were never tied into the central sewer system.
