IN SEARCH OF PROTOZOA

PROTOZOA & LEGIONELLA are reported to be linked.  Legionella can be harbored within the body of Protozoa.  Protozoa are large one cell organisms, easily seen under a microscope, and are generally associated with a mature biological population.  You see,  Protozoa dine on bacteria and need a very sizeable bacterial population available in order to thrive.  The existence of large populations of Protozoa in a Cooling System is not a good sign. 

BIOCIDE PROGRAMS should be designed to control the majority of bacteria found in any Cooling System.

The single biggest threat to a Cooling System is biological growth.  In fact, over 90% of piping failures in Cooling Systems is contributed to Biologically Induced Under Deposit Corrosion Conditions.  The biocide program should be designed to control bulk water counts  (<10,000 cells/ml of total aerobic count has always been our standard recommendation), biofilm, and underdeposit type bacteria.   

Do not always be fooled by good bulk water counts ! Testing is performed on Cooling Water to give you “indications” of what may be occurring in the system.  They are not empirical information as to the condition of the system.  Unfortunately, it is not quite that easy. 

The testing of the water for key parameters along with regular equipment inspections is the right way to address the needs of your Cooling System. 

Checks of the Tower Sump, Coupon Racks, Spool Pieces, Equipment Strainers and Filtration Media should be conducted regularly. 

Visual Inspection of the heat exchange equipment via Video Borescope should be conducted at least yearly.

CASE STUDY – APRIL 19, 2001 : Subject - A large Commercial Office Building in NYC with a Tenant Cooling System servicing a vast number of Package Units.

A very astute Chief Engineer noticed some black deposit in the Cooling Tower that he had not seen before.  He became concerned and notified the Property Manager.  The Property Manager asked his Water Consultant to come in immediately to investigate the situation. 

The system is on a standard Homeyer Consulting specified dual alternating biocide program consisting of a halogen and non-oxidizing biocide with biocide additions of at least 3 feeds per week.  The system is also outfitted with 0.5 micron sand filtration.  Over the past few months, the total biological counts (run twice weekly by building staff) have been close to zero, or zero, every singe time.

Over the years this building has had problems with low flow horizontal branch piping.  Most of the horizontals have been replaced with copper and all package units have been outfitted with 3 way valves to insure flow in the piping.

THE PROBLEM was that the package unit coils themselves (even with 3 ways) can go stagnant for extended periods of time in the winter months.  This water becomes a breeding ground for bacteria.  As the weather warms the tenants begin using cooling from the package units, which had been idle, releasing the organic matter to the rest of the system.  This organic matter was first seen in the Cooling Tower and then was collected from one of the Package Unit Strainers.

THE ANALYSIS of the strainer deposit found huge populations of bacteria and large numbers of various pretty good size Protozoa.

THE SOLUTION to this problem was the immediate sterilization (under the auspices of the Treatment Supplier) of the entire system  in an attempt to kill off the Protozoa and burn up the newly released organic material now in the system strainers.  We feared an early season biological contamination that if allowed to bloom may have plagued the system for months to come.  The human health risk was taken very seriously and immediate action was the order of the day.  Large numbers of Protozoa is not a good sign for any system.

In the future, efforts will be made to open up the Package Units in the winter months during biocide additions.