The Q46N monitor from Analytical Technology Inc. (ATI) continuously measures free ammonia, total ammonia and monochloramine in potable water. Designed for monitoring chloraminated water to minimize excess ammonia, the system features fast response for real-time measurement and better process control.
Unlike colorimetric and ion selective electrode monitors, the electrochemical Q46N monitor converts ammonia to monochloramine and measures the monochloramine.

“What that allows us to do is real-time, continuous monitoring,” says Bill Popp, national sales manager, ATI. “You know from second to second instead of every five minutes what the true concentration of ammonia is. Let’s say you’re driving down the road but your display only updates every five minutes. You pass a cop with radar. Would you want to guess how fast you were going? If you’re adjusting chemical feed rate in a batch mode, you have three to five minutes of undershoot or overshoot that you could be dealing with. How do you know when you have enough? If you’re trying to maintain a fairly tight control, it’s going to be very difficult to do.”

The ammonia monitor utilizes a simple chemical system with inexpensive reagents. Three separate reagents are required for operation.

“The reagents are sodium hexametaphosphate, which is a sequestering reagent,” Popp says. “The second reagent is chlorine bleach. The reaction converts ammonia to monochloramine. The third reagent is hydrogen peroxide, which destroys excess chlorine. The reagents are readily available. You can buy them from us or mix them yourself. The goal is to make the operating cost extremely low.”

Multiple communication options include Profibus, Modbus and Ethernet, as well as analog.

“Inside a plant, if you’re upgrading a system or adding new equipment, it’s easier to install a single bus,” Popp says. “Think of it as a line that goes along the inside wall of the building. If you can take a monitor and clip onto that line, you’re not running additional wires for each monitor. You’re getting all the instruments basically communicating on one set of wires.”

When reading free ammonia, water comes into the bottom of the monitor where an electrochemical sensor measures the amount of monochloramine, establishing a baseline. An internal sample pump draws the sample and adds the sequestering reagent, followed by the chlorine and peroxide. A second sensor measures monochloramine concentration after the chemicals are added. The baseline reading is subtracted from the second reading, determining the amount of free ammonia in the sample.  

The monitor requires routine maintenance every three to six months (change membrane and electrolyte). A year’s supply of replacement parts is included with the monitor. 800/959-0299; www.analyticaltechnology.com.