|Greg Glover, Victor Chan, and Gerald Borling check the Programmable Logic Controller (PLC) to monitor phosphorous levels in the wastewater.|
Introduced in 1972 with the Clean Water Act, the NPDES program sets strict limits on pollutants in the treated wastewater returning to Lake Erie and the Cuyahoga River. Our plants consistently receive silver or gold “Peak Performance” awards from the National Association of Clean Water Agencies (NACWA) for meeting these limits.
“We’ve always protected the permits,” said Southerly Superintendent John Augustine. “But to get the gold [award] takes extraordinary measures to increase and maintain focus on permit limits.”
The main challenges to meeting the permits are eliminating chlorine residual and maintaining consistent pH levels. Even a brief deviation from these numbers can result in a violation.
“The biggest risk is chlorine residual,” said Easterly Superintendent Robert Bonnett. During recreation season (from May to October), chlorine is added to the wastewater to kill bacteria. Then, sodium bisulfite is added to neutralize the chlorine.
“If there is any chlorine remaining, it’s an instant violation,” said Bonnett. A single five-second interruption can qualify as an NPDES excursion, so the plant operators make sure to feed ample sodium bisulfite into the effluent.
Another factor that must be maintained 24/7—and not just during beach season—is pH, or acidity. You may recall from high school chemistry that water’s pH is 7.0; anything lower than that indicates acidity. Our NPDES permits state that pH cannot drop below 6.5, even for an instant.
“The weather plays a big factor,” said Westerly Superintendent Larry Cinadr. “Rain dilutes the wastewater so it loses its alkalinity.” To elevate pH back to an acceptable level, the plant operators introduce another chemical, sodium hydroxide.
“The difficulty is that it’s not like a manufacturing assembly line, where you can control the raw materials,” said Bonnett. Rain and melting snow greatly increase the volume of wastewater the plants must treat and the amount of chemicals needed to maintain permit levels.
In addition, advances in technology can actually make it harder to meet permit limits, since these advances justify even tighter NPDES standards to which the plants are held.
The superintendents credit the plant operators for their vigilance in maintaining correct dosage of chemicals into the flow, with excellent support from Maintenance, Engineering, and Automation. “It’s a concerted effort on the part of multiple groups,” said Augustine.
Westerly Operator Greg Glover monitors approaching storms via Doppler radar forecasts. “Staying on top of the weather allows us to prepare extra tanks and proper chemical feed,” he said. “We also schedule regular risk assessments to avoid any interruptions, and we’ve improved our backup systems,” added Augustine.
However, at any time, an unanticipated problem—a broken line or power outage—could turn into a permit violation before anyone could react, ruining a plant’s perfect NPDES record. “Our operators are trained to respond quickly,” said Westerly Shift Manager Alan Legault. “But there’s always a little bit of luck involved, too.”
Story by Communications Specialist Michael Uva