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Accepta Newsletter: Issue 4

A message from the editor: Firstly, thank you for all your positive comments and suggestions we've received and secondly, welcome to our fourth newsletter. If you'd like to comment on any of the issues raised, make suggestions for future articles or suggest ways in which we can improve this service please contact me.

Articles in issue 4:

• How to Investigate an Outbreak of Legionella: Government Guidance for Enforcement Officers.
• Accepta Launch Innovative Single Parameter Test Kits at Only £1.40 ea.
• Reverse Osmosis in Industry.

How to Investigate an Outbreak of Legionella: Government Guidance for Enforcement Officers

Recent high profile outbreaks of Legionnaires Disease both in the USA and UK have caused many of us to re-focus on the issues surrounding the effective management and control of water systems vulnerable to Legionella contamination. However, once an outbreak has been identified what procedures do local government and health and safety enforcement officers follow during their investigations:

• What is the definition of an outbreak?
• How is an outbreak situation managed?
• How do they deal with the public?
• What are the implications for water treatment companies?

To answer these questions and many more we've included on our web site a full copy of the document;

'Control of Legionella: Investigation of Outbreaks (and Single Cases) of Legionellosis from Water Systems Incorporating Cooling Towers and Evaporative Condensers'.

This comprehensive document, which was revised in February 2002, is produced by the UK's Health & Safety Executive/Local Authorities Enforcement Liaison Committee (HELA) and gives guidance to local authority enforcement officers and inspectors when conducting investigations into outbreaks and single cases of Legionellosis associated with wet cooling systems and other sources.

To read the full document please click here or type the following link into your browser: http://www.accepta.com/industry_water_treatment/legionella_control_water_systems.asp

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Simplicity is the key to Accepta's innovative Single Parameter Test Kits. These handy sized water test kits, which are based on the recognised 'Drop Test' method, are very simple to use, help reduce the hazards normally associated with similar testing procedures and, best of all, they are inexpensive and extremely cost effective at only £1.40 each.

Each test kit comprises two small plastic bottles, one inside the other. The inner bottle contains the chemical reagent required for the test; whilst the outer bottle acts as the 'test tube' to hold the water sample; simplicity itself.

How to use the test kits

Take the reagent-containing bottle from inside the larger test tube bottle. Fill the now empty test tube bottle to the appropriate calibrated mark with the water sample. Insert the reagent bottle top into the preformed hole in the top of the test tube bottle and then add the reagent drop by drop until a colour change occurs as instructed. The test results are obtained by simply multiplying the number of drops of reagent added by a predetermined factor. Test complete.

Currently, the following parameter test kits are available with more being developed:

• Total Alkalinity
• Stop / go hardness
• Total hardness (raw water)

For further details please email Accepta or telephone us: + 44 (0) 1625 267 581.

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Reverse Osmosis in Industry

Reverse Osmosis (RO) is a process that industry uses to clean water whether for industrial process applications or to convert brackish water, to clean up wastewater or to recover salts from industrial processes. It will not remove all contaminants from water as dissolved gases such as dissolved oxygen and carbon dioxide not being removed. But Reverse Osmosis can be very effective at removing other products such as trihalomethanes (THM's), some pesticides, solvents and other volatile organic compounds (VOC's).

The Reverse Osmosis (RO) Process

In the Reverse Osmosis process cellophane-like membranes separate purified water from contaminated water. RO is when a pressure is applied to the concentrated side of the membrane forcing purified water into the dilute side, the rejected impurities from the concentrated side being washed away in the reject water. RO can also act as an ultra-filter removing particles such as some micro-organisms that may be too large to pass through the pores of the membrane.

Reverse Osmosis (RO) Membranes

Common membrane materials include polyamide thin film composites (TFC), cellulose acetate (CA) and cellulose triacetate (CTA) with the membrane material being spiral wound around a tube, or hollow fibres bundled together. Hollow fibre membranes have a greater surface area and hence capacity but are more easily blocked than spiral wound membranes.

RO membranes are rated for their ability to reject compounds from contaminated water. A rejection rate (% rejection) is calculated for each specific ion or contaminant as well as for reduction of total dissolved solids (TDS).

TFC membranes have superior strength and durability as well as higher rejection rates than CA/CTA membranes. They also are more resistant to microbial attack, high pH and high TDS. CA/CTA's have a better ability to tolerate chlorine.

Sulphonated polysulphone membranes (SPS) are chlorine tolerant and can withstand higher pH's and are best used where the feed water is soft and high pH or where high nitrates are of concern.

Factors Affecting Performance

The performance of a Reverse Osmosis system depends on factors such as membrane type, flow control, feed water quality, temperature and pressure. Also only part of the water entering the unit is useable, this is called the % Recovery. This is affected by the factors listed above. For example the amount of treated water produced can decrease by about 1-2% for every 1 degree Celsius below the optimum temperature.

An RO system must be well maintained to ensure good performance with any fouling requiring cleaning maximising the output of water. Biocides may be needed and the choice of biocide would depend on the membrane type, alternatively other filters may be required to remove chlorine from water to protect the life of the membranes To this end a good treatment regime is needed and knowledge of the specific foulants so the optimum cleaning and maintenance chemicals can be chosen.

Accepta have a full range of chemicals for Reverse Osmosis applications, contact us for more information or browse our online products database.

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