Simplified in-house tests help operators

In-house readings with streamlined TOC test support process control, compliance

By Julie A. Schlegel, for Hach Company

The Ivy River, source water for the 1.5 MGD-capacity Ivy River Water Treat-ment Plant (WTP) in Weaverville, western North Carolina, brings with it all the elements from its richly-organic water-shed covering hundreds of acres. However, the resourceful WTP staff has found ways to work with the highly unpredictable influent, in part by using Hach TOC (total organic carbon) laboratory tests.

These simplified, in-house tests help operators optimize removal of natural organic material and adjust dosage of chlorine that can combine with organic material to form disinfection by-products (DBPs). As a result, the WTP has minimized DBP levels while still complying with coliforms limits.

Plant operators - like those of many WTPs, pretreatment facilities, and industrial processors -need to have real-time analysis results to adjust treatment and achieve efficient process control, even compliance, of final stream. The Hach TOC test uses unit-dose, prepared reagent in vials ready for sample addition, digestion in a compact block reactor, and direct colorimetric measurement in a Hach spectrophotometer precalibrated for these and more than 100 other Hach water quality tests. The newly available DRB200 Digital Block Reactor is programmable and offers 15 vial wells, so that up to 14 samples and a reagent blank can be digested simultaneously.

Streamlined with respect to required bench space, equipment, and time - operators can have TOC readings from any point in the process in hand in about three hours - the practical test helped Ivy River WTP operators model the facility’s new pretreatment clarifier when it went on line. Ready TOC results helped them select coagulant and dosage and monitor clarifier function and sludge blanket integrity as often as needed. "We could run the test in the morning, and change the process right away, " explained Operations Supervisor Tony Laughter (pronounced LAW-ter).

Operators continue to use the expeditious TOC readings to tame the highly unpredictable Ivy River source water and assess treatment performance, especially during rainfall events Ð the equivalent of unexpected, or significant, loading changes for the industrial treatment process operator. "We couldn’t make constant improvement without these tests," Laughter affirms. "Our local regulator is pleased with our extra effort to avoid problems."

Maybe that river isn’t so mean, after all!