Capacitor-based colloidal dispersion
Electrostatic dispersion of colloidal particles applies theories from colloidal physics and colloidal chemistry to produce a strong electrostatic dispersion of colloidal particles in a fluid. This is accomplished by forming a capacitor within a water system. A strong electrostatic field and corresponding capacitor is created by inserting an insulated electrode into a grounded pipe or vessel. Numerous papers have been presented to engi- neering conferences or published in peer-reviewed journals that discuss in detail the principles of operation of the technology (Pitts 1992, 1995; Romo, Pitts, and Hector 2002; Romo and Pitts 1999, 2000; and Romo, Pitts, and Handagama 2007).
The conductive lining of the ceramic electrode serves as one plate of the capacitor. The dielectric strength of the vitrified ceramic material that comprises the electrode prevents current flow to the other plate of the capacitor. The grounded plane of a cylindrical capacitor is established by the metal of the pipe or vessel into which the rod is inserted.
A direct current power supply charges the capacitor system to a very high potential (normally 30–35 kV DC). The field strength between the plates of the capacitor is a function of charge voltage, dimensions of the equipment to be treated, and the dielectric constant of the ceramic.
Characteristic of a capacitor, there is no electrical current flowing across or through the ceramic body of the electrode and into the water. Operating costs for the power supply are negligible, with power consumption at less than 5 W. The maximum current output of the power supply is 600 μA (just over .5 mA).
The electrostatic field reduces the surface tension of water and boosts the surface charge of colloidal particles and wetted surfaces. Particles suspended in the water are caused to repel one another and to be repelled from other wetted surfaces. Through these physical effects, particles and bacteria that would otherwise combine to form scale or biofilms are dispersed and the potential for fouling is mitigated.
With particle agglomeration controlled, cooling water can be evaporated to high concentrations of dissolved solids. The capacitor-based system, combined with instrumented monitoring, is able to support high levels of water use efficiency, while assuring system stability with reduced labor inputs and minimum energy consumption.
Fouling and corrosion controlled by particle dispersion
Unlike a chemical program, the capacitor-based system is able to approach the problems of fouling in cooling water systems by treating fouling at the source, rather than by controlling only the symptoms. By producing a treatment based on the alteration of the physical properties of colloidal particles, this technology is not affected by variations in the chemical composition of the MU water; therefore there is no risk of over-feeding or under-feeding a chemical product into the system.
Biofilms supply the foundation for scale to adhere, and they provide a se- cured hiding place for bacteria and resulting MIC. The electrostatic charge imparted to wetted surfaces disrupts the bonding capacity of a biofilm, thereby forcing the clearing and flushing of biomass from the tower system by the turbulence of the flow.
Without the addition of acid, the chemical buffer capacity of the water ele- vates the pH to 8.9–9.0, and the water analysis presents highly positive LSI details. As stated earlier, a positive LSI is indicative of a high potential for scaling, but presents little or no corrosion potential. With a positive LSI and a pH level of 8.9–9.0, corrosion rates are minimal for mild steel and copper alloys.
Application of electro-static colloidal dispersion techniques, even under conditions of high scaling potential, offers an indirect corrosion control technique, using well-understood chemical relationships.
Water conservation by volumetric control
The composition of dissolved minerals in most water supplies varies over time, and the variance may occur seasonally or daily. Zeta Water Management Programs bring water chemistry effects into consideration, but focus on the management of bleed rates for water conservation by volumetric standards, rather than by conductivity control.
At high concentration ratios, shifting from conductivity measurement to volumetric control avoids the unpredictable operating variance associated with conductivity, and true cycles of concentration can now be measured. Water meters are installed on pipes of the MU water and bleed lines. Electronic control units record flow data and control the bleed valve.
￼Volumetric control of blow down provides accurate measurement of water usage and sewer discharge volumes, thereby allowing for direct calculation of cumulative water cost savings and proof of water conservation. It also ensures that true cycles are maintained in the system regardless of changes in the chemical composition of the make up water.