Tuesday, 3 February 2015

Taint in Bottled Water - Airborne Contaminants

Bottled water is produced and distributed as a packaged food product and listed under food standards legislation in the UK.  The larger bottles seen on water dispensers in offices and other locations are a popular means of providing hydration to work forces in many industries and students in schools and universities.

Production, Storage and Distribution
The large 19L bottles are filled in a bottling plant and transported to distribution depots where they are stored for a while before delivery to customers.  When the bottles are empty, they are collected from the customer, returned to the distribution depot and subsequently forwarded to the bottling plant for washing and refilling.

Choice of Polycarbonate
Polycarbonate is the major plastic material used for the large 19L bottles.  This has many advantages over other plastic materials, for example, it is a clear, strong plastic which is durable and able to withstand the washing process at high temperatures without shrinkage or damage.  The disadvantage of polycarbonate is the porosity of the material when used in bottles.  Although the porosity does not affect any of the other bottle properties, there is a vulnerability to transmission of certain materials through the bottle walls which can then affect the taste of the water.  The porosity of polycarbonate has been studied and several scientific papers are available1, 2.  The taste buds are very sensitive to minute traces of odoriferous materials in water.

Airborne Contaminants Affecting Taste
Materials with a strong odour, such as solvents, strongly flavoured foodstuffs such as garlic and coffee and certain chemicals will all affect the taste of water if kept in close proximity.  Of particular concern are highly volatile materials, such as volatile organic compounds, since the concentration of these can be very high near their source.  Small molecules are able to penetrate through polycarbonate more easily than larger molecules, for example, xylene is both volatile and a small molecule.  This is a component of paints and other coatings.

Proximity of Contaminants
It is a requirement of all distribution depots that no materials affecting the taste of water are allowed within the depot.  For example, diesel fork lift trucks are forbidden.  It is necessary at certain times of the day to open the roller doors to allow access for loading and unloading.  At this time, the bottled water is vulnerable to contaminants coming from the immediate outside environment.  This is particularly a problem with volatile contaminants such as solvents and other chemicals.  The choice of location of the depot is made with due consideration of near neighbours and any existing processes which could result in airborne contamination.  This sometimes limits the choice of location.

At the point where the roller doors are open, prevailing winds, down draughts, humidity or rain can markedly affect the ingress of contaminants that could affect water taste.

  1. D. S. Lee, K. L. Yam and L. Piergiovanni “Food Packaging Science and Technology”, CRC Press, Taylor and Francis Group (2008).
  2. Valentina Siracusa “Food Packaging Permeability Behaviour: A Report” International Journal of Polymer Science, 2012 (2012) Article ID 302029, 11 pages.

Thursday, 22 January 2015

Tap Hygiene in Hospitals

Many hospital departments have very high public usage of dispensers.  For example, in a major London hospital, the cooler located in A&E was in use 24hrs and, on average, 1000 cups were consumed over a time period when the average for other coolers in the hospital was 300 cups over the same time period.  The bacterial contamination at the tap outlets increased proportionally as the usage increased (survey previously commissioned by British Water Cooler Association).

Tap sprays containing disinfectants provide a simple way of reducing contamination and these are available from several suppliers.  Certain types of disinfectant spray produce a long-lasting effect, up to 30 days.  However, their use requires close cooperation between Facility Managers and the cooler providers to ensure that the coolers with the highest usage are treated more frequently.  Simple swab testing of the taps will enable the effectiveness of this intervention to be monitored.