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.