The Zeta Rod™ Performs at the
Los Angeles Convention Center

INTRODUCTION

The Los Angeles Convention Center installed their Zeta Rod system in early February 1998. The system is comprised of eleven Zeta Rod electrodes energized by four power supplies. This system protects large cooling towers, a 500-ton chiller and two 1250-ton chiller systems in the West Plant of the Convention Center.

A third-party consulting firm was contracted to monitor the performance of the Zeta Rod system, and compare the results obtained with a similar cooling system operating under a chemical water treatment regimen in the South Plant of the Convention Center.

Parameters measured included:

• Water quality: pH, alkalinity, hardness (total and Ca), chlorides, silica, and total iron.
• Corrosion rates: mild carbon steel (C1010) and copper (CDA110).
• Total aerobic bacteria.

INSTALLATION & OPERATION

The Zeta Rod system was installed during the first week of February 1998, during a season when the plant was not in full operation. Because there was no flow in the systems, the consulting firm reported on April 20th that "biological control in both [chemical and Zeta Rod] condensing water systems was not acceptable...The elevated biological activity is most likely from the extended stagnant conditions..." A twice daily or low-flow continuous recirculation of the condensing water was recommended. Convention Center personnel implemented a program in which the condenser water was circulated for continuously between 0730 and 0830 hr and 1930 and 2130 hr each day.

On 26 May, the consultant reported that "all data trends appear to be showing program improvements across the board." Specifically, it was reported that "biological control in both condensing water systems has improved," and that "all [corrosion] coupons analyzed show corrosion rates below industry standards (see footnote 1)."

This report concludes that chiller operating data showed "proper efficiencies," indicating that the overall health of the system was good.

The final report of June 23 stated that, "our findings showed evidence of on-line cleaning in the West [Zeta Rod-equipped] Plant chillers that had been operating." The evidence included softening of old deposits, freshly-cleaned areas on the insides of the condenser tubes, loosened scale chips and calcium carbonate mud in low flow areas such as tower sumps.

The report also indicated that, "biological control in both condensing water systems has stayed consistent," and that all of the corrosion coupons analyzed still showed corrosion rates below industry standards.

[1. "Corrosion Standards for Cooling System Water Treatment" from Blake, R.T., Water Treatment for HVAC and Potable Water Systems, McGraw Hill, N.Y., 1983, pp126-127 are used by this consulting firm. The rates given in this reference are (1) mild steel: 0-2 mils/year = excellent, 2-5 mils/year=good, and (2) copper: 0-1 mils/year = excellent, 1-2 mils/year = good.]

DATA

Biological data (below): samples were gathered from the cooling tower sumps after recirculating each system for at least 30 minutes.

Corrosion rates (below): coupons of mild carbon steel (alloy C1010) and copper (CDA 110) were exposed between the dates indicated on the chart below.

CONCLUSIONS

The consultant's final report concluded that:

1. "On-line removal of existing deposits can be more rapid with an acid assisted chemical program than with the Zeta Rods, but proper protection of critical system metals may be compromised in the process...the on-line cleaning properties exhibited by the Zeta Rod resembled those of a strong, non-acid chemical program."
2. "Biological control in all condensing water systems was virtually identical despite the treatment approach utilized." [Zeta Rod vs. chemical biocides]
3. "Chemical feed excursions and chemical leaks did occur with the South [chemically-treated] Plant system. This would be impossible with the Zeta Rod technology."

NOTE: The Los Angeles Convention Center purchased additional Zeta Rod equipment, and now the entire facility is protected from scaling, corrosion, and biological fouling by the Zeta Rod system.