The Orion Chlorine XP online process analyzer from Thermo Fisher Scientific uses colorimetric DPD chemistry to continuously measure total and free chlorine. Designed for low cost of ownership, extended reagent use and increased accuracy, the analyzer combines multiple measurements in one unit.

“You can have free chlorine only, total chlorine only, free and total chlorine with pH and free and total chlorine without pH,” says Manav Randhawa, product marketing manager for Thermo Fisher Scientific. The analyzer also can measure routine water-quality parameters.

“One of the key things this product has is the ability to achieve a minimum detection limit of 10 ppb consistently,” he says. Greater sample accuracy also helps extend reagent use from 30 days up to two months at five-minute cycle times.

“As a wastewater operator, most wastewater plants add chlorine to make sure the water is disinfected before it is released,” Randhawa says. “The analyzer determines how much chlorine should be added. And once the chlorine is added, the range of the analyzer allows the operators to monitor the amount of chlorine that they add and test how much chlorine is in the water before it is released.”

Water enters the analyzer, which self-zeroes before each sample, and flows through a filtering chamber, removing some of the residue. Sample conditioning is not required. From there it enters the reaction chamber, triggering the reagent pumps. The pumps only trigger when a sample enters the chamber. Using the DPD method, a color reaction, ranging from clear to red, takes place. The darker the color, the more free chlorine is present. Color intensity is converted to ppm using the Beer-Lambert law. An up-and-down movement mixes the sample, making it more homogenized for greater accuracy.

The analyzer’s self-adjusting light source, hands-free, self-cleaning photocell and elimination of bubbling in the photocell help reduce maintenance.

“Every year we recommend changing the peristalic pumps, filters and tubing to the filters and pumps,” Randhawa says. “That’s pretty much the only maintenance, other than changing the reagents.” A maintenance kit is available.

The 24-pound analyzer is 26 inches wide by 13 inches high and 5.5 inches deep. Password protected, it has an IP-65 rated enclosure (NEMA 4 equivalent) and 5.5-inch LCD graphic display with background light alarms and status. 978/232-6000; www.thermoscientific.com/processwater.