Is Your Colilert Test Working?

Colilert® is one of the standard test methods widely accepted for the determination of absence/presence of coliforms. Each test normally is negative and production continues with a sigh of relief. However, there is sometimes the nagging doubt that maybe this test is not working for some reason.

There is an answer to this dilemma which is a calibration technique known as Quant-Cult®. This kit provides safe samples of E.coli, K.pneumoniae and Ps. aeruginosa and a method of testing which is straightforward. The kit comes with small vials of the bacteria which are contained in the caps of the vials. The vials contain rehydration fluid which comes into contact with the bacteria when the vials are inverted. After a brief incubation period of 10 mins, the vial contents are added to 100ml sample jars followed by the standard Coilert® powder. After the normal incubation time, the sample with Ps. aeruginosa should remain colourless, the K. pneumoniae should be yellow and also the E. coli. The E. coli will fluoresce under UV light.

Make sure that the UV lamp is rated at at least 6W otherwise seeing the fluorescent effect will be difficult.

The standard Colilert® Test is very sensitive with only one coliform giving a positive reading. It is important therefore to be very scrupulous with hygiene when using the technique. It is essential to use sterile sample jars.

A further issue with sample jars that sometimes causes confusion, is that the suppliers provide sample jars containing sodium thiosulphate. This is unnecessary with water samples in the bottling plant because the purpose of the thiosulphate is to neutralise the effect of chlorine in treated tap water.

There is another method of detecting coliforms which is much less expensive than the Colilert® route. This involves a filtration technique with inoculation of a nutrient medium. However, the Colilert® technique is much easier to use.

Another thing to watch out for is not to leave the sample jar in the incubator for longer than the standard time. A yellow colour will develop eventually thus giving a false positive.

A further reminder, if the Colilert® powder appears to have lost its finely divided, free-flowing appearance do not use it, this will be an indication of hydrolysis and degradation, which again will give a false positive.

Finally, if you find detection of a positive result is made difficult by a yellow background caused by other effects, and use of the comparator is border line, then consider the use of Colisure® instead. This will give you a magenta colour as a positive result.

Recycling 25L Chemical Containers

In the bottled water industry, chemicals are used for cleaning and disinfection purposes.  These chemicals are water-based and used at a high dilution.  Most frequently encountered sizes of containers are 1000L, 200L and 25L.  The chemical manufacturer will often arrange return of the empty 1000L and 200L containers, free of charge, for re-use.  However, not many will pick up the 25L containers.  As a result, these will often end up in land fill.

Recently, recycling companies have appeared on the scene who will collect empty 25L containers for re-use or plastic recycling.  This has not been so common in the past because companies would not collect small numbers of containers.  A company in Manchester, PRDS Ltd, will collect empty 25L containers, provided they have no toxic or flammable residues.  This is therefore ideal for chemical containers used in the beverage industry.

Collection of 1 pallet of 48 containers will cost £50.00, collected from anywhere on the UK mainland, although this cost is waived if the bottler is able to deliver to the company in Manchester with their own transport.  Note that it is still necessary to rinse-out the containers before despatch.  This is a very positive step towards responsible handling of plastic waste in the beverage industry.

Green Bottles - The Problem of Algal Contamination

Bottles which are heavily contaminated always must be discarded and never enter the bottle washer. However, those showing slight algal growth can be treated and reused. The requirements are to use an  oxidizing chemical, good mechanical action and hot water. If good mechanical action is not possible, then the chemical should be used at a higher concentration. Chemicals that have been used include the following:

peracetic acid
hydrogen peroxide
hypochlorite solution
nitric acid

Nitric acid is effective but dangerous to handle. Hypochlorite is also effective, but has to be rinsed thoroughly to avoid chlorine taint on the polycarbonate bottle. Hydrogen peroxide has been used, but is not as effective as peracetic acid. Peracetic acid is commonly used and normally available as 5% or 15% concentrates. These should be diluted down to 1% for use in de-greening bottles. Water temperatures of 60-70°C should be used. Mechanical action is very important and the use of brushes is needed. From a safety point of view it is better to use a special rig for cleaning the bottles rather than a manual process. This may be home-made, or, much better, be of the type shown in the photograph which is specially designed for pre-washing bottles using hot water and rotating brushes.

Pre-Washer



Brush Configuration in Pre-Washer

                                                                                   

Checking Effluent from the Bottling Plant

Polycarbonate bottle washing requires much less causticity than glass bottle washing.  Having said that, there are various maintenance processes in the bottling plant that require stronger chemicals, such as CIP processes, descaling and deep disinfection.  The effluent from the bottling plant can therefore have lower pH or higher content of oxidising disinfectants than normal during these maintenance operations.  Typical acids used in descaling operations are phosphoric and nitric.  Apart from personnel safety issues in handling these chemicals, the effluent from these processes needs careful monitoring.  Some effluent is collected in an independent effluent treatment plant, other effluent goes directly into the public sewer system and some effluent is discharged on to land or into ponds.  In each case, the pH needs to be monitored, particularly if discharge is on to land or into ponds.

The disinfectant mainly used in the bottling plant is peracetic acid.  This will eventually degrade to vinegar and water, but this can take some time.  All effluents will have been greatly diluted, for example peracetic acid is delivered mainly as a 5% solution and this is then diluted to a use concentration of about 0.1%.  However it is still necessary to monitor the oxidising content of effluent, particularly if dosed into a pond.  This may be done by measuring the oxidation-reduction potential of the water.  Some effluent will actually benefit pond life, for example disinfectants based on hydrogen peroxide degrade to oxygen and water.  However, the oxidising potential must still be monitored.  ORP meters will measure a voltage related to the oxidising potential in the water.  Extremely low voltage readings are undesirable because this indicates thet the water is becoming stagnant, whereas readings above 700mV are unsafe for aquatic life because of the high oxidising content.   Combination meters measuring pH and oxidation-reduction potential are available from several suppliers.  

Water-Cooler Tap Contamination

A recent survey of mains-fed water coolers in several premises (see earlier blog) has shown that microbial contamination of the inside of taps is considerable, even a short time after a sanitising service visit.  This is particularly acute with high-use coolers in public areas such as schools and hospitals.  In some cases the insides of the taps were colonised with the opportunist pathogen Pseudomonas aeruginosa.  Whereas, healthy users would not necessarily be harmed, those with compromised immune systems may well be affected.  This may be critical in certain hospital departments.

Although the recommendation to spray the insides of the taps regularly with a disinfectant spray, such as hydrogen peroxide, may well alleviate the problem temporarily, the re-contamination is likely to occur rapidly.  An earlier blog describes the use of anti-microbial surface treatment to provide a longer-lasting disinfectant or bacteriostatic effect in several applications. Application of sprays which provide a long-lasting anti-microbial effect inside cooler taps is now possible.  These sprays are taint-free and safe for use on water contact surfaces.  However, further work is required to establish the efficiency in use of these sprays, for example, how long-lasting are they, does the applied spray need to dry out inside the tap, how much is flushed out when the tap is used again and how much could end up in the water to be drunk?  We know more about peroxide sprays, which are also taint-free and harmless in the water (peroxide is sometimes used to purify water), so that more work needs to be done with the new anti-microbial sprays that have recently appeared on the market. 

Pseudalert from Idexx

Bottlers are familiar with Colilert in their day-to-day control of bottled water quality.  Colilert from Idexx determines the presence or absence of coliforms in water.  Coliforms are not allowed in bottled water and testing is done for every batch of bottled water produced.  Coliform bacteria can be found widely in the environment, in soil, water and on vegetation, but are also abundant in the faeces of warm-blooded animals.  While coliforms themselves are not normally causes of serious illness, they are easy to culture and their presence is used to indicate that other pathogenic organisms of faecal origin may be present.  The test itself is simple and uses a powder which is added to the water sample.  After incubation for 24 hours at 37 degrees C, a colour change from clear to yellow indicates the presence of coliforms.

A new kit for determining the presence or absence of Pseudomonas aeruginosa is now available called Pseudalert.  The procedure is similar to that indicated above except that the initial colour of the sample is yellow and, after incubation, the presence of Ps. aeruginosa is inicated by the presence of flourescence under UV light.  Ps aeruginosa is a pathogen which can cause infections in open wounds.  In a water environment, it is often associated with biofilm, a protective slime which serves to protect microorganisms.  Ps. aeruginosa is not allowed in bottled water, although it should have little effect on healthy individuals.  However, people with a poor immune system, mouth ulcers or throat lesions could be affected.  At high levels, the microorganism can cause off-tastes and odours.  Currently bottlers are testing for the presence of Ps. aeruginosa in their regular quality checks.

Hygienic Coatings

TV adverts for cleaning products show germs lurking around every corner. A recent survey from South Korea found that shopping trolley handles harboured more bacteria than any other commonly used item. The next most contaminated were the mice (computer variety!) in Internet cafés, followed by hand straps on buses and bathroom doorknobs. Manufacturers are picking up on this growing public awareness by developing a range of antimicrobial products - everything from bathroom accessories to paint for hospital walls and food preparation areas, to coatings for surgical instruments.

Hygienic coatings are not new. Home decorators have been buying antifungal paints for kitchen and bathroom walls for years. US market leader Microban, for example, has become a household name by putting its antimicrobial agents in chopping boards and food containers. What is new, however, is the explosion of new applications for coatings. Recent applications have included water coolers and there are many other potential applications in the bottled water industry.

There are three major technologies in use today: silver, reactive silanes and organic biocides. The details are too numerous to be described in this short blog, but if you are really interested see “Antimicrobial Surfaces in the Food Industry” by T F Child, New Food, 2, 52-56 (2006).

For application in bottled water and cooler markets the essentials are:
No transfer into the water (no taint);
No discolouration or loss of transparency of plastic materials;
Must survive normal cleaning or multi-wash cycles and preferably be effective for the lifetime of the treated article.

Potential applications: water cooler reservoirs, pipe work, taps, casings, drip trays; replaceable plastic parts (for longer life);19L polycarbonate bottles; cap chute, capper head and filling area; floors, walls, doors and ceilings in the bottling plant. The ideal time to treat a building is when a new bottling plant facility is being set up, although post application is still possible. After cleaning, the product is sprayed on to surfaces and allowed to dry. The treated surface can remain active for many months.

For water cooler servicing, treatment of the tap area will give a long-lasting protection against microorganisms introduced from outside the cooler, either by users or the general environment.  

Mains-Fed Water Coolers, Links with Contamination

A recent project involved a survey of mains-fed water coolers at 8 different sites, with a wide variety of installations, cooler specifications and use profiles.  Water sampling and swabbing of tap outlets at weekly intervals revealed the following summary results:

 1. All coolers had considerable bacterial loading in the tap outlets. The bio-loading increased as the frequency of use increased.

2. A large number of cooler outlets had TVC values at 72hrs/22°C too numerous to count.

3. A total of 6% of tap outlets were colonised with Ps. aeruginosa at the time of sampling. The presence of this pathogen was linked to very high use frequency, an unclean environment around the cooler and high temperatures arising from incorrect routing of pipework near heat sources.

4. There appeared no relation of contamination with length of microbore tubing or specification of the cooler, although fountains appeared more susceptible to biofilm formation than other types of dispensing coolers.

5. There appeared no difference between coolers with UV lamps and those without.

6. The hygiene awareness of the users plays an important role in reducing tap outlet contamination.

7. Of the 160 samples of water, only 3 showed coliform presence, of which 1 showed the presence of E. coli. This contamination arose from the tap outlets on the dates of sampling and was not detected in subsequent visits.

8. Many taps were encrusted with scale, indicating that they had not been changed or cleaned up during servicing.

9. Bio-loading in taps was evident within a few days after servicing.

10. The majority of coolers had no servicing docket, indicating date of servicing or verification that the servicing checklist has been completed.

A more detailed report will be made available shortly, which includes recommendations for best practice.  This work was commissioned by the British Water Cooler Association, whose members provide both bottled water and mains-fed water coolers.