Tuesday, 31 May 2011

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.  

Wednesday, 18 May 2011

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.