Challenge

Originally built as a primary treatment plant in 1957, the Middletown, Ohio, Wastewater Treatment Plant was upgraded to a secondary treatment in 1971.  Today, the 26 MGD activated sludge plant serves a population of 55,000 as well as the local paper industry.

In early 2002, Middletown plant management decided to switch from using gaseous chloirne to sodium hypochlorite for disinfection.  In reviewing chemical delivery systems, Middletown wanted to find an alternative to distributing 15 percent sodium hypochlorite under pressure.  "We wanted to avoid the potential for problems associated with leaks and off-gassing in a pressurized system,"  says Wastewater Treatment Manager Steve Thompson.

Solution

Ultimately, the chemical feed system selected by the plant’s consulting engineer utilizes vacuum induction to provide precise dosing of sodium hypochlorite and high-speed chemical dispersion. The gaseous feed system was replaced with two LVN-2000 Liquid Chemical Feed Systems, equipped with a Water Champ® Chemical Induction Unit (CIU), to draw and meter sodium hypochlorite from supply tanks to the point of application.

• Each LVN-2000 has a maximum flowrate of up to 7.7 GPM. The V-Notch variable orifice of the LVN-2000 system, field-proven in thousands of installations worldwide, provides accurate, reliable chemical metering, providing precise, smooth feed rate adjustment over a range of 20-to-1.
• The submersible 7.5-h.p. Water Champ CIU serves as the vacuum source, eliminating the need for conventional inductors. The unit design includes a stainless steel motor with vacuum end components consisting of a titanium vacuum body and airfoil design propeller that instantaneously disperses chemicals into the process stream, applying all available energy directly to the chemical being activated.

Results

Plant operators like the new liquid feed system.  The wall-mounted LVN-2000 provides multifunctional touchpad controls, facilitating flow monitoring and adjustment.  "It's a very simples and reliable system to perate," says Thompson.  "We just set the feed where we want it and we're good to go."  The LVN-2000 system also provides a high level of safety.  "We like the aspect that the new feed system is vacuum-induced,"  Thompson says.

• The Water Champ CIU is mounted on a rail system in the center of the 72-inch diameter pipe delivering treated effluent to the plant's chlorine contact tanks. 
• Sodium hypochlorite is injected into the body of the Water Champ and is dispersed while being simultaneously mixed by the unit's propeller.  Flows passing the mixing area make contact with turbulence and distributed chemical, providing for a high rapid mixing rate, resulting in optimum chemical mixing efficiency.
• The combination of accurate, reliable chemical feed and high performance mixing has allowed for more efficient chemical usage, resulting in Middleton using less sodium hypochlorite than original projections.  "Our actual sodium hypochlorite consumption has been 30 percent less than what our consulting engineer has estimated, "says Thompson."