Research Highlights

Online Water Quality Monitoring

Monitoring online drinking water quality for aberrations that may indicate contamination is one way in which the presidential directives have been implemented. Proof-of-concept experiments that water quality sensors respond to contamination in a water distribution system are conducted at the EPA's Test and Evaluation Facility (T&E) in Cincinnati, Ohio. Commonly available contaminants are injected into a recirculating pipe loop (Figure 1) and single-pass distribution system simulators, and the response of commercially available water quality sensors is evaluated. Common water quality sensors are used because water utilities, who may implement contaminant warning systems in the future, are knowledgeable about their operation and maintenance. This approach also allows for dual benefit applications of water quality monitors. In addition to detecting contaminants, utilities will have more knowledge about the water quality in their distribution system. Problems arising from operational failures that affect water quality have a greater chance of being detected.

EPA’s T&E Research Projects

The recirculation pipe loop at T&E is a 240-gallon ductile iron pipe with a mean retention time of 24 hours. Contaminants such as Round-Up® herbicide and Real Kill® pesticide produced a large decrease in free chlorine, and increase in TOC due to their organic nature. Compounds such as inorganic arsenite decreased free chlorine but did not affect TOC. Biological suspensions of non-pathogenic E. Coli and spore-forming bacteria meant to simulate anthrax were also injected. When injected with their growth media, free chlorine was consumed and TOC increased. Military agents such as VX, GB (sarin), potassium cyanide (KCN) and ricin were tested at an off-site facility capable of handling the agents but employing the same experiment design as was used at T&E. Free/total chlorine and/or TOC detected all four contaminants.

In addition to the recirculating loop, a single-pass pipe was used. The three-inch diameter, 1200-foot long pipe is a more realistic representation of a real-world drinking water distribution system. Water quality was monitored at two points in the pipe (80 and 1100 ft from the injection point). The injection lasted for 20 minutes, and the response shows that the contaminant traveled as a slug through the length of the pipe.

Future Challenges

1. Testing event detection algorithms under various water quality conditions
2. Determining which commerically available water quality parameters are the best for online monitoring (This requires balancing the number of contaminants that a parameter responds to with the capital and operation and maintenance cost of that parameter.)
3. Performing experiments in drinking water with different residual disinfectants and water quality (Although free chlorine is still a commonly used disinfectant in drinking water, chloramines are becoming increasingly popular. Differences in each system must be evaluated.)
4. Identifying and evaluating new and emerging detection technologies that have wide and robust detection ability (Sensors that need little maintenance and are operationally simple are valuable in contaminant monitoring.)
5. Detecting biological and radiological contaminants (New and existing technologies will be employed for detecting these contaminants.)

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Contact: John Hall

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