By WAYNE CASTONGUAY
April 1999: The pollution of our waterways by domestic wastewater has been one of our largest environmental issues since the connection between sewage contaminated water and human illness was first discovered nearly 100 years ago. Since that discovery, numerous methodologies have been
developed to detect sewage contamination in the environment. Nearly all of these methods involve collecting a water sample and analyzing it for certain types of bacteria which are present in large numbers in wastewater.
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Placing an Optical Brightener sampling device at a suspected septic system break out through a retaining wall
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These bacteria generally live within the gastro-intestinal tract of humans and other warm blooded animals. Hence, their presence in a water sample above certain levels often indicates that the water is contaminated with sewage. One group of these bacteria, fecal colliform is the primary type of bacteria currently used to “indicate” the presence of sewage in water.
However, there are several drawbacks and limitations to fecal coliform sampling. Among these, the following are the most important: First, because it is not possible to directly count the number of bacteria in a water sample, a laboratory is required to culture the bacteria to have them multiply into sufficient numbers to be detected by visual means. Having access to a certified laboratory is often difficult and is nearly always an expensive proposition. Second, because fecal coliform bacteria are found in the feces of all warm blooded animals, their presence in a water sample doesn't necessarily mean that it is contaminated with human sewage. Third, because bacteria are living organisms, environmental conditions can significantly influence test results and lead to false conclusions.
A new method for detecting the presence of wastewater has recently been developed which addressees each of these problems and shows great promise. Instead of testing for bacteria, this new method tests for another component of domestic wastewater, dyes used in laundry detergent. These chemicals, known as Optical Brighteners (OB) are fluorescent white dyes that are added to almost all laundry detergents. Theses dyes are a necessary ingredient in laundry detergent because cotton fabrics naturally appear yellow and drab. Optical Brighteners are needed to dye the fabric each time it is washed to make it appear bright and white. Because these man made chemicals never occur naturally in the environment, are nearly always a component of domestic wastewater, and are simple and inexpensive to test for, OB sampling has the potential to revolutionize water quality sampling.
Although several groups and organizations have begun to perform OB sampling in recent years, no official method yet exists which describes the sampling or analysis methodology. Realizing this deficiency, two 8T&B members, Dave Sargent and Wayne Castonguay have used their extensive experience in OB sampling to write and publish a handbook
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Drainage from a perimeter drain to a catch basin
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which describes in detail for the first time, the proper sampling and analysis procedures. The handbook also summarizes how OB sampling can be used as an indicator to identify faulty septic systems, sewage system exfiltration, storm drain cross-connections, and human/animal waste differentiation. The handbook is very user friendly and can be used by individuals, volunteer monitoring groups, professionals, and government officials alike.
The method essentially involves placing a protected natural cotton pad in a waterway for a specified period of time (usually one week). The pad is then retrieved, dried, and visually examined for the fluorescent dyes under an ultra violet light in a dark room. Because the materials are inexpensive and the analysis does not require any special materials or a laboratory, a large OB sampling program can be established for only a few hundred dollars. Although the methodology is simple and straightforward, the authors caution that before sampling, the handbook be carefully read and the limitations and data analysis be thoroughly understood. Because the method appears so simple, we have observed several groups and organizations report erroneous results based on improper OB sampling techniques and faulty data interpretation.
The handbook is available online and a printed copies are available free of charge from the authors through 8T&B.
