Disinfection

Disinfection
Peristaltic pump improves fluoride injection accuracy

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Peristaltic pump improves fluoride injection accuracy

Problem
Pulsating-type diaphragm metering pumps were injecting fluoride at the Jones Ferry Road Water Treatment Plant in North Carolina. The fluoride treatment system at the 20 mgd plant requires one primary pump and one backup pump controlled by 4-20 mA and monitored by a SCADA system. The injection rate is 63 ml/min. Operations supervisor Dusty Martin, with the Orange Water and Sewer Authority, had trouble maintaining accurate and consistent fluoride residuals using the diaphragm pumps, which also were affected intermittently by air pockets that entered the system through the day tank.

Solution
Martin installed a Flex-Pro peristaltic pump from Blue-White Industries. The pump easily hooked into the SCADA system; continuous monitoring confirms that the exact amount of chemical is being injected and residual levels are more consistent.

Result: The peristaltic pumps have been in operation for more than six years with very low maintenance. “I highly recommend a peristaltic pump for fluoride injection,” says Martin. “It has proven very reliable and accurate for many chemical injection applications associated with water treatment.” 714/893-8529; www.blue-white.com.

UV disinfection system installed on an abbreviated schedule

Problem
To meet strict deadlines to implement California Department of Public Health and U.S. EPA LT2 rules for drinking water disinfection, the San Francisco Public Utility Commission (SFPUC) needed to accelerate design, construction and installation of the Tesla Water Treatment Facility, which draws unfiltered water from the Hetch-Hetchy reservoir in northern California.

Solution
The SFPUC used a collaborative design-build construction model and installed a newly designed UV disinfection system engineered by Calgon Carbon Corporation, consisting of 12 Sentinel 48 Chevron UV reactors. Each reactor has nine 20 kW lamps oriented in a chevron formation for effective UV dosing with the least power consumption. The system was designed to function without human supervision except for periodic calibration.

Result: The project brought the Tesla Facility to full compliance with all state and federal public health mandates in about half the time typically required for similar design-bid-build projects, and came in under budget. The plant is the largest of its kind in California, treating 315 mgd and serving more than 2.5 million people. 800/422-7266; www.calgoncarbon.com.

Test confirms effectiveness of PAA disinfectant

Problem
A water treatment plant in Steubenville, Ohio, needed a cost-effective water disinfection method that would not generate chlorinated byproducts.

Solution
In a little more than a month, Solvay Chemicals conducted independent plant-scale trials using Proxitane WW-12 peracetic acid (PAA). PAA is a faster-acting disinfectant than chlorine-based chemicals, does not generate harmful DBPs even if overdosed and can be economically retrofitted or work in series with an existing disinfection system. The plant was operating at 5 to 8 mgd with a capacity of 13.5 mgd.

Result: PAA dosage never exceeded 1.5 ppm, and the residual averaged 0.4 ppm but did not exceed 1 ppm. PAA feed was flow-paced, CBOD remained constant and pathogen control was always within the permit limits. The test was a success. 800/765-8292; www.solvaychemicals.us.

New chlorinator improves efficiency at award-winning plant

Problem
The Village of Montpelier, Ohio, was updating its water treatment facility and wanted to replace the gas chlorinator equipment. The village originally used a gas chlorinator that needed continual work on its heads, would leak or stick often and needed replacement components. The staff lacked time to babysit the chlorine tank when it was about to go empty.
          
Solution
The village chose the Regal Gas Chlorinator from Chlorinators Incorporated. When one tank goes empty, it automatically switches to the standby tank and maintains a constant feed rate. When used with Regal SmartValves, the system is flow proportional, allowing the flow to be adjusted from 1,400 gpm in summer to 1,000 gpm in winter.

Result: The system helped the village eliminate downtime, save money and reduce labor. Montpelier has won the gold medal at the annual International Water Tasting Event in Berkeley Springs, W.V., three times. 772/288-4854; www.regalchlorinators.com.

Ozone disinfection and pretreatment solves taste and odor issues

Problem
The City of Bécancour, Quebec, Canada, needed a replacement for its older air-based ozone unit. While the unit was still operational, the city struggled with removing color and total organic carbon (TOC) and reducing disinfection byproducts (DBPs) in finished water.

Solution
Pinnacle Ozone Solutions provided a complete ozone treatment system. The Pinnacle Peak Series ozone generator system provides ozone to both the pretreatment and disinfection process steps at the plant via a single integrated system. Working with one provider simplified design and installation; the company handled zone generation, oxygen supply, dual ozone injection skids and complete process controls. Other benefits included a significantly reduced footprint, quieter operation and lower maintenance.

Result: By employing Pinnacle’s Ozone-On-Demand controls, the plant maintains constantly high ozone concentrations of 10 percent across the full range of operating conditions. When combined with the ozone generators, this significantly reduces total power and operating costs. 321/205-1717; www.pinnacleozone.com.

Ozone system clears up taste issues

Problem
The water reaching faucets in Waco, Texas, had such foul taste and odor that residents considered it undrinkable. The problem originated from high nutrient loadings in runoff from dairy farms in the watershed above Lake Waco, the city’s raw water source. The contaminants triggered explosive algae blooms and pathogen spikes. Costly chemical treatment added to the process chains failed to suppress the taint.

Solution
A $55 million process upgrade designed by CH2M Hill and The Wallace Group resolved the problem by adding advanced pretreatment clarification, complemented by a 90 mgd PDO1000 ozone disinfection system from WEDECO – a Xylem Brand. The dual-purpose ozone system provides primary disinfection without harmful chemical byproducts, ahead of mandatory dose of chlorination at release to the distribution system.

Result: The ozone system oxidizes any residual nutrients and delivers maximum disinfection. The taste and odor in the water are gone, along with the complaints. 704/409-9700; www.xyleminc.com.

Leak detection equipment yields savings

Problem
With 75 miles of pipeline installed before 1950 and the unbilled water rate at 34 percent in 2010, operations manager Richard McDaniel of the Rockdale County Water Resource in Conyers, Ga., saw a need to monitor the aging water mains and valves. The department’s budget offered limited leeway.

Solution
In 2011, after research and competitive bidding, McDaniel purchased 370 Permalog+ acoustic leak noise loggers, a Patroller II drive-by data collection device, a TriCorr Touch real-time leak noise correlator, a SoundSens “i” advanced correlating logger system and an Xmic ground microphone from Fluid Conservation Systems. The products work together to analyze leak noise from water lines, transmit the data to mobile collection units, and pinpoint leaks to minimize repair time and cost. McDaniel and his team also completed extensive product training to ensure proper operation.

Result: Within the first year, Rockdale County Water found more than 50 leaks responsible for losses of 248,000 gpd. At a cost of $1 per 1,000 gallons of water, the program has already saved customers more than $90,000 per year. The agency plans to continue expanding Permalog+ coverage of its distribution network. 800/531-5465; www.fluidconservation.com.



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