Cooling Towers

Use of a Water Conditioner to control the Aquatic Environment of Cooling Towers

Introduction

This paper represents an alternative non-chemical means of managing the aquatic environment of cooling towers, in a way that appears to preclude the proliferation of bacteriological contaminants. 

A water conditioner was sized to the cooling tower circulation rate and reservoir capacity, and installed as a by-pass circuit 
that would circulate the cooling tower water through the conditioner for 12 hours every day. 

Prior to commencement of the experiment, a number of parameters were decided which are as follows: 

(a) an adjacent cooling tower which did not have a water conditioner fitted, would be subject to the same schedule of tests as the cooling tower which did have the water conditioner device fitted. 

(b) both cooling towers would be thoroughly cleaned. 

(c) one cooling tower would continue to use biocide and algaecide chemicals and the cooling tower which had the water conditioner 
device fitted would not use any chemicals. 

(d) a program of tests and inspections was scheduled. 

(e) TBC dip slide tests were taken and recorded. 

The test schedules were: 

Total Bacteria Count, Legionella Count, Total Dissolved Solids, Alkalinity, and pH. 

What was of major significance, and is possibly the most important point of this paper, is that during the two year experiment, no algaecide or biocide chemicals were used in the cooling tower with the water conditioner device fitted. 

Throughout this time, the test results as provided by a NATA certified testing agency have identified the lowest detectable levels of all legionellas which is <10 CFU/ml, and the TBC has consistently remained at less than 10³. 

This is an excellent result for cooling towers which are using chemicals, but is an exceptional result from cooling towers which are using no biocide or algaecide chemicals.

What are the results of the experiment thus far?

(a) The device appears to be able to consistently maintain a TBC of below 1 x 10³ CFU/ml and a Legionella bacteria count of <10 CFU/ml. 

(b) The cooling tower is visually clean. 

(c) The condenser tubes on the water side of the refrigeration unit condenser allied to this cooling tower, were not cleaned at the commencement of the experiment. However when the condenser end covers were removed for their seasonal inspections and tube cleaning, every tube was observed to be completely clean and shining like a gun barrel. 

What benefits has the project identified thus far? 

(a) The cooling tower is dispersing neither Legionella or biocide aerosols. 

(b) The cooling tower no longer requires cleaning except for the requirement to desludge the water pan. 

(c) The shell and tube condensers attached to the refrigeration machinery no longer require cleaning or brushing. 

(d) An additional benefit of item (b) is that the compressor efficiency is not impaired or reduced because of dirty or scaled condenser tubes. 

(e) The use of cooling tower chemicals has been eliminated subject to the Total Bacterial and Legionella counts remaining below a specified limit. 

The two year field test experiment had thus far substantiated that the aquatic environment of a cooling tower and an evaporative cooler can be controlled using what has traditionally been known as a proprietary device. 

The evidence supporting this is the visual results of the experiment and the certified NATA laboratory test results of the water samples.