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The Little Falls Water Treatment Plant has roots in postcolonial history, having sprung up in Totowa, N.J., on the cutting edge of American industry in the late 1800s. Maintaining its tradition over the years, the plant has continued to improve using modern science and engineering to the benefit of its more than 500,000 customers.

Legionella , the causative agent of Legionnaires’ disease, is an emerging concern for water utilities. Passaic Valley Water Commission (PVWC) is a public drinking water supplier, which provides treated surface water to approximately 800,000 customers in New Jersey. To evaluate the occurrence of Legionella in the PVWC distribution system, swab, first draw, and flushed cold water samples were collected from total coliform sites ( n  = 58) during a summer and winter sampling event. Endpoint PCR detection methods were combined with culture for Legionella detection. Among 58 total coliform sites during the summer, 17.2% (10/58) of first draw samples were positive for 16S and mip Legionella DNA markers and 15.5% (9/58) in flushed samples. Across both summer and winter sampling, a total of four out of 58 sites had low-level culture detection of Legionella spp. (0.5–1.6 CFU/mL) among first draw samples. Only one site had both a first and flush draw detection (8.5 CFU/mL and 1.1 CFU/mL) for an estimated culture detection frequency of 0% in the summer and 1.7% in the winter among flushed draw samples. No L. pneumophila was detected by culture. Legionella DNA detection was significantly greater in the summer than in the winter, and detection was greater in samples collected from areas treated with phosphate. No statistical difference was found between first draw and flush sample detection. Total organic carbon, copper, and nitrate were significantly associated with Legionella DNA detection.

Two advances in the technique of potentiometric gas sensing are introduced. A novel approach to collecting gases in a recipient solution is used to devise a continuous monitor for atmospheric ammonia, and a new sulfite-sensitive solvent/polymeric potentiometric membrane is developed and found suitable for sulfur dioxide measurements. An introduction to the state of gas monitoring in general, and potentiometric gas sensing in particular, is given in Chapter 1. In Chapter 2 a simple yet new way of collecting analyte gas into a suitable recipient stream is described. Continuously-flowing recipient buffer (pH 7) is exposed directly to the gas sample to be analyzed via a microporous \"sniffer\" tube. The collected ammonia converts to ammonium in the buffer and is pumped through an established flow-through ammonium-selective electrode. The optimized sensing arrangement is capable of continuously monitoring sub-ppbv levels of atmospheric ammonia. The Chapter describes the response time, detection limits, stability, and selectivity characteristics of the new system. The theoretical foundations for the behavior of the \"sniffer\" design are discussed in Chapter 3, accounting for the observed detection limits and response behavior. Chapter 3 also predicts the sniffer's response to changes in sample temperature, as well as the effects of modifications to the present design for faster response and/or better detection limits. In Chapter 4, a new solvent/polymeric electrode membrane based on bis(diethyldithiocarbamato)mercury(II) is introduced. The membrane is highly sensitive to sulfite-ion activity, displaying a lower limit of detection below 1 $\\mu$M sulfite. It is found to exhibit selectivity towards sulfite over most common ions (iodide, bromide, and reduced-sulfur anions interfere). The selectivity of the potentiometric sensor is enhanced by its incorporation into a flow-through gas sensing arrangement, providing selective determination of sulfite in liquid samples even in the presence of the above interferents. In conjunction with the new sniffer, this membrane can also provide continuous measurement of gas-phase sulfur dioxide at parts-per-billion levels.