Continuous, On-line, Low-cost Monitor to Detect Arsenic in Water

The EPA has imposed a maximum contaminant level for arsenic at 10 ppb, which poses a tough standard for a significant number of the nation's community drinking water systems. One major issue relates to how the utility knows when the filtration media has saturated with the removed arsenic and needs regeneration or replacement. The current method of monitoring the filtration system effectiveness involves taking water samples periodically and submitting those samples to labs using wet chemistry methods. That process has shortcomings. An improved method entails the use of a continuous, on-line, low-cost monitor that automates the process. A solution for that requirement employs a sensor device known as a quartz crystal microbalance (QCM) that vibrates at 10 million cycles per second. When chemistries are applied to the crystal surface that are selective for arsenic, the vibrations slow down, signaling the presence of the contaminant. Technical issues that will be addressed are, (a) the sensor must be selective for arsenic, (b) the signal must be amplified to be responsive at 1 ppb, (c) the system must be reliable, low-cost and low maintenance. An added benefit is that the system can be readily adapted to detect arsenic at a well head.