In a pilot study carried out with the UK’s third largest supermarket group, 70% of emergency refrigeration calls were due to overflows and drips. Of those calls 88% were identified as blocked drain lines attached to condensate pans, of these calls 95% were cause by an organic slime “Zoogloea”.
For those of you who have brought up children, looked after friends kids or have ever baby sat then you will have at some time witnessed a child with the worst runny and bubbly nose. Without putting too light a point on it, this is the best mental picture I can think of to help you visualize and understand what consistency “Zoogloea” takes. It’s thick , gelatinous and if not treated just keeps on growing till your “nasal passage”, sorry, “drain line” blocks up completely causing drips and overflows. When left too long the slime build up begins to smell really unpleasant and turns into one large bacterial play ground.
So… back to the child’s nose analogy. The way to deal with the blockage initially is to blow or suck out the drain line , usually with a wet vac. In many cases the problem is so extreme that a complete removal and re-piping is not unheard of.
But to resolve the problem you need to appreciate what you are dealing with. The “Slime” is a by-product of the moisture that is present in the condensate drip pan of a cooling system. In general, cooling equipment works by passing warm air over cooling coils, which creates water droplets just like the beads of condensation which form on the inside glass of a window when its cold outside. Depending on the size of the unit you will increase or decrease the amount of moisture that needs to run off to an external drain line or an evaporation pan.
Zoogloea is the special state of bacterial cells that when their capsules become slimy, form a gelatinous structure or film. The literal translation means “Animal Glue” so our child analogy really is pretty close. These slimy forms are mostly inherent with water based bacteria. The bacteria are aerobic (which means they work in oxygenated environments) and create a slimy consistency for absorption of the nutrients which are present in the water and swell rapidly given the right conditions. The slime is generally stable in pH ranges of 3-10 and temperatures -5°F to 194°F (15°c to 90°c) which means their fairly robust.
Different environmental conditions do effect growth, which is why stores in separate parts of the country are affected differently due to climatic conditions. However the presence of airborne organics which get pulled into the cooling system provide large amounts of nutrient rich moisture to feast upon. In a restaurant environment the presence of sugar, yeast and flour generally create a greater problem than an office building. Soda machines and cold store rooms are other areas which can be effected, but stronger flow of water can reduce retention time which can help prevent biological growth. The final components are certain metals which can oxidize. These metals help our slime breed and are ever present in the manufacture of cooling system components. Provide the right environment and your protoplasmic ( a new slime reference to the 1984 Ghost Buster Movie) bacterial cells will double every 20 minutes.
Preventative treatment is the only cost effective option for both the restaurant operator and refrigeration contractor. If we temporarily ignore the issues of health risk from bacteria, slips and falls from drips and other infrastructure damage such as stained tiles , the cost of repetitive call outs is huge and environmentally carbon Inefficient.
In simple words, killing the bacteria growth is the only effective option. To treat the problem effectively, clear away the old waste and prevent re-growth. The condensate water entering into the drain pan needs to be suitably sanitized and be able to carry sanitizing material all the way through the drainage system.
Historically Chlorine and Bromine based products are used in tablet and liquid formats these however are wholly unsuitable due to the chemical reactions, which occur. Chlorine is slightly soluble in water and reacts with water to form hypochlorous acid and hydrochloric acid. On contact with moisture Chlorine tablets dissolve and release gas. The chlorine gas in large quantities is a respiratory sensitizer (aggravates and causes harm to human air ways) which creates a risk to public health.
But equally important the gas is highly corrosive and causes significant oxidation of metal work which leads to rapid corrosion of fins, fans and other metal work within the cooling system. The hypochlorous and hydrochloric acids break down quickly which increases the acidity of the water. These products are cheap which could make them an attractive option, but they only last two to three weeks which means a higher level of repetitive treatment and the add on cost of corroded cooling equipment.
Ultraviolet lighting found in residential air conditioning could be considered to kill off airborne microbes, but presently they are rarely found in commercial AC systems. They are, however, becoming increasingly popular in some grocery cabinet display systems.
The most cost effective solution for treatment is to use a slow release system which will last between 3 and 6 months and should fit in with your standard maintenance program. The material and compound you need to consider must be EPA approved and should contain a registered biocide with Fungicidal, Algaecidal, Germicidal, & Bactericidal properties. This will tackle your Zoogloea problem but also other potential health causing contaminants (To name a few well know ones) such as Bacterial: Staphylococcus, Streptococcus, Legionella - Fungal: Candida - Viral: Influenza, Herpes, HIV-1.
For delivering a slow release there are a few timer drip systems, for liquid type solutions, on the market which run through a peristaltic system. But again for ease and least maintenance or initial outlay, a slow release system that uses a nylon styled polysleeve and contains a gel form of material would be a sensible option to consider. The gel compound contains an EPA approved chemical formulation, with an odor counter-actant and corrosion inhibitor. These AC Pan and Drain systems work by slowly disintegrating with the flow of moisture and carrying the biocidal particles down stream through the drain system, where they kill existing growth and release old slime debris in the line. These systems generally require less maintenance and require no prior preparation. Depending on your cooling needs they can be obtained in different sizes to fit your maintenance requirements and equipment size.
Reflecting back to our supermarket group at the beginning of this article, in a controlled trial study over a 6 month period, refrigeration flooding and leak call outs were reduced by 85%, the remaining 15% of call’s were due to cocktail sticks and other non biological debris .
