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flocculation chambers. The water is settled and passed through tube settlers before being filtered through dual media gravity filters. A small amount of chlorine is added on top of the filters to control bacteriological growth in the filter media. The filtered water is then disinfected with gaseous chlorine, and blended phosphates are added as a corrosion inhibitor. After meeting required contact time (CT), the finished drinking water leaves the plant and is pumped to sanitized reservoirs, water towers, and to the customer’s tap. The utility maintains an active laboratory where common drinking water parameters are measured and logged with each shift. The utility also has an active flushing program in place. Data from the 2012 Water Quality Report is collected in Table 1. The plant serves approximately 26,000 customers and the City of Lebanon, TN, is part of the Nashville Metropolitan Statistical Area. The THM-Rapid Response System All THM measurements were made using the THM-RR system (Foundation Instruments, Inc., Collierville, TN). The patented THM-RR system [4] (Figure 1) is an improved rugged and robust version of that reported by Brown and Emmert [5]. The THM-RR uses a patented sampling device for fully automated online monitoring of individual and total THMs. The THMs will pervaporate through a capillary membrane in the sampling device and are chromatographically separated, detected, and quantified automatically. As illustrated in Figure 2, drinking water directly from the tap continuously flows through the THM-RR, the THMs pervaporate through the patented membrane in the sampling device and are introduced into the system where they are chromatographically separated and quantified. Sample collection, THMs analysis, and all calculations are fully automated. The data is displayed on the Dashboard of the controlling PC in numeric and graphical format. The data collected is also automatically stored in spreadsheet and text files that are SCADA accessible. As long as the PC is connected to the internet, the device may be remotely accessed and monitored. Some control options are available from remote locations. The THM-RR provides sample analysis rates of one sample per hour with THMs results from last run available in about 30 minutes in most cases. The device can also be easily taken offline for the analysis of grab samples and check Figure 2: Illustration of operation of the THM-RR System Click here to return to table of contents Winter 2014 | | Straight from the Tap 35