Challenge

Oxidative disinfection is the final stage of treatment at Landis Sewage Authority’s 8.2 million gallons per day (MGD) wastewater treatment facility in Vineland, New Jersey. Sodium hypochlorite (NaOCl) is used to disinfect treated wastewater to meet a very stringent fecal coliform limit at this zero discharge facility.

For years a double diaphragm liquid metering pump had been used to pump NaOCl from the plant’s three 6,000-gallon bulk sodium hypochlorite tanks to an injection point in the treated effluent stream prior to entering the plant’s chlorination chambers. In 2001, this pump was reaching the end of its useful life.

Solution

The existing double diaphragm metering pump was replaced with an S-Series Chemtube® Peristaltic Pump System (PPS) from USFilter Wallace & Tiernan Products.

• With the Chemtube® PPS, there are no valves nor seats required in the pumped fluid to foul or wear out, as with other pump types.
• In addition, premium, efficient roller technology eliminates use and disposal of the lubrication fluid typical of other peristaltic pumps using a sliding-shoe design.

Results

“The new Chemtube® PPS pump has been operating for more than a year nonstop, and we have not had a single problem with it,” says Rick Eustace, operations/maintenance manager for the facility. “Sodium hypochlorite is a very aggressive product and if there is any vibration in the feed system, there’s eventually going to be some leakage. Although we were not unhappy with our prior double diaphragm pump, we are extremely pleased by the smooth performance of the Chemtube PPS®, and we especially like the ease of maintenance it is providing us. With other pumps, there is always worry about valves and seals wearing out, but with this new pump we have found the only maintenance involved is changing the unit’s hose every five to six months, which is about a 10-minute process.” The pump is equipped with a built-in float-type leak detector that is activated at the earliest indication of hose failure and can be connected to local or remote alarms.

The new pump is located at the facility next to the bulk storage tanks and connected via a 3-inch feeder line.

• Utilizing a direct coupled, right angled gearbox, the Chemtube® PPS provides the smallest footprint possible. This compact design minimizes floor space, providing more room for service and other equipment.
• At the Vineland facility, the Chemtube® PPS uses an AC inverter motor and a variable frequency drive for turndown ratios up to 10:1. The speed is automatically controlled from a process signal generated by the plant’s Strantrol®  ORP controller. According to Clark Shimp, process control manager for the plant, NaOCl has a tendency to outgas and air-bind some metering pumps, and the previous pump at the facility had been no exception. “We use 15 percent sodium hypochlorite, and it occasionally gasifies in our lines. With our previous pump, we had occasions when the unit started to not track well due to this gasification, and we would then have to bleed the lines. But with nearly full vacuum suction capabilities of the Chemtube® PPS, we have not experienced this problem.”