Disinfection

Disinfection
Amperometric chlorine residual analyzer solves iron-clogging issue

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Amperometric chlorine residual analyzer solves iron-clogging issue

Problem

A military base in North Carolina installed chlorination systems at two well sites. High iron levels in the groundwater clogged the membrane of the residual analyzer’s measuring probe and kept the chemical feed pumps from dosing at the rate needed to achieve the free chlorine residual required for drinking water disinfection.

Solution

After two months of cleaning, membrane replacement and recalibration, the contractor replaced the analyzers with an FX-1000P-CS amperometric chlorine residual analyzer with integral PID controller from Foxcroft Equipment & Service Co.

The bare electrode design with constant cleaning and distilled white vinegar pH buffer eliminated the fouling issue. The scalable 4-20 mA output provided the continuous signal required to maintain automatic residual control with the metering pumps.

Result

The analyzer helped the base regain compliance while reducing the downtime, expense and labor to clean and recalibrate the analyzers every one to two weeks. 800/874-0590; www.foxcroft.com.

Ozone system resolves hydrogen sulfide, disinfection and color issues in well water

Problem

The Four Way Special Utility District (SUD), Eastern Angelina County, Texas, operates multiple potable water plants, serving both urban and rural customers. Well No. 3 flows at 1.1 mgd and serves over 2,000 rural customers. The presence of hydrogen sulfide, color due to the presence of tannic acids, and sulfur-reducing bacteria were issues for the district.

Solution

The SUD’s consultant, Goodwin-Lasiter Inc., proposed ozone treatment as the solution and submitted a design/treatment proposal to the Texas Commission on Environmental Quality. It was recognized that ozone systems employing the efficient Mazzei Injector Company GDT contacting system in the consultants’ design would provide precise control of the ozone dosage to achieve treatment objectives while avoiding the formation of byproducts such as THMs and bromate. The commission granted approval for an integrated ozone treatment system incorporating onsite oxygen pro-duction, ozone generation and a Mazzei GDT-3090 Ozone Transfer skid to replace the current aeration system.

Result

The ozone system is now in operation at Plant No. 3. Finished water monitoring/testing is reported as better than projected, eliminating hydrogen sulfide, color and disinfection issues. 661/363-6500; www.mazzei.net.

Analyzer monitors organics in source water

Problem

Seasonal variation, heavy rainfall and accidental contamination often affect raw water quality at the Los Filtros Water Treatment Plant in Puerto Rico, requiring immediate attention. The facility produces drinking water for 256,000 residents, receiving water from the Guaynabo and Bayamon Rivers.

Solution

Facility manager Nancy Ma. Cáceres Acosta coordinated with Daniel Smith of Montanas Electric and Orlando Laguer of Nator Corporation to integrate a coagulation optimization package. Preliminary source water testing indicated variable concentrations of organic matter, known to consume coagulant and lead to the formation of disinfection byproducts (DBPs). A Real Tech UV254 analyzer was installed to monitor organics for coagulant dosing with dual stream capabilities to evaluate process efficiency. The analyzer was packaged with an HMI control panel and a remote telemetry system.

Result

The facility captured multiple organic contamination events on the influent source water stream. Phase 1 testing of the package presented an average monthly reduction of 22,917 pounds of chemical coagulant for $9,831 in savings. A 23 percent reduction was seen in sludge formation. Facility personnel are confident that the potential for DBP formation is limited. 877/779-2888; www.realtech.ca.

UV disinfection helps facility comply with surface water treatment rule

Problem

The White Tanks Regional Water Treatment Facility in Surprise, Ariz., treats water from the Colorado River delivered by a 336-mile canal. Using surface water requires the facility to comply with the U.S. EPA Long Term 2 Enhanced Surface Water Treatment Rule, designed to protect against Cryptosporidium and Giardia.

Solution

After evaluating technologies and suppliers, White Tanks installed two TrojanUVSwift units from Trojan Technologies in August 2009.

Result

The units have worked effectively and efficiently. Daily Cryptosporidium monitoring has revealed zero violations. “The SCADA communication system is set to send an alarm to the control center automatically in the event that the combination of plant flow, UV transmittance and reactor power level results in operation outside the validation limits for the equipment,” says Joseph Cornejo, White Tanks operator. “Facility output is 13 to 14 mgd with each of the two units capable of treating 20 mgd. This allows for facility volume expansion while achieving 3-log inactivation of Cryptosporidium and Giardia.” 888/220-6118; www.trojanuv.com



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