Contamination of product is always of major concern for food or drink producers, bottling plant operators and consumer products and pharmaceutical manufacturers.
The devastating costs of contamination dictate that operators are always on the look out for effective sanitisation processes.
Contamination can occur from:
- The added ingredient
- Process water
- Chlorine based chemical treatment.
- Ultra violet radiation.
- Steam or heat treatment.
Since 1996, when FDA approved the use of ozone as a disinfectant in food processing, ozone has become the most popular disinfectant used. The residual effect of chlorine based chemicals can result in tainting and unwanted effects on the final product and UV and heat treatment do not ensure complete disinfection.
Ozone versus chlorine
Quite apart from the “tainting” effect, ozone is quicker and stronger than chlorine as a disinfectant.
Ozone disinfects 600 to 3000 times faster than chlorine and is the most powerful water-treatment oxidant known. It is neither a chemical powder nor a taste-contributing liquid, but a gas whose action is performed instantaneously when added to water.
The following table shows that 20 to 40 times more chlorine than Ozone is required to disinfect bacteria over the same period of time.
Also it will take .1 mg/l of chlorine four hours to eliminate 6104 cells of E. Coli in water, while 0.1 mg/l of ozone requires only five seconds.
Therefore to disinfect, not only is less ozone than chlorine required but it is also far quicker in its disinfecting ability.
Also chlorination treatment can result in damaging chlorinated organic by-products and chlorine does not have the beneficial effects on some chemicals as ozone does.
Ultra Violet rays achieve disinfection with complete elimination of living cells, in active or spore form when the rays are applied to a thin layer of water. The lamps must be strong enough and may require renewing before there is a notable decrease in the UV radiation output. The water to be treated must be transparent, without cloudiness or colour, iron free and clear of organic colloids or plank tonic micro organisms. Water contaminated in this way will lead to sediments being formed on the tubes reducing the penetration of the rays. The necessary regular replacement costs of UV tubes are very high which discourages users from replacing as often as they should.
In the light of this UV treatment on its own is not recommended and therefore a combination of UV and other disinfection is preferable if it is to be used at all.
Steam or heat treatment is expensive, impractical and not necessarily guaranteed effective.
Ozone is commonly used in the following applications:
- RINSING LINE
- PROCESS WATER
- SUPPLY AND DISTRIBUTION BOTTLING LINES
- WATER USED FOR THE CONCENTRATE
- EFFLUENT TREATMENT ( HIGH COD)
- THE RINSING LINE
The most popular application for ozone in bottling plants is for the sanitisation of bottles prior to filling. The sanitising properties of ozone are obtained nearly instantly, and no unwanted by-products are produced.
- PROCESS WATER
Ozone is safely used to ensure that the process water is sterile or to destroy traces of residual chlorine.
Common super chlorination treatment of process water consists of using chlorine dosages of 10-25 mg/L to incoming water. As the oxidising capability of ozone is higher than that of chlorine, if ozone is used, only 50-75% of the chlorine currently being added is necessary as some of the chlorine added is converted to chlorinated organic by-products.
In the case of natural mineral water (not spring water), in Europe and Australia ozone is approved as a disinfectant, provided that treatment information is carried on the label. These countries permit the use of ozone “to separate unstable elements from natural mineral waters which will ensure that the composition of the water as regards its essential ingredients is not affected”. (The unstable elements referred to include iron, manganese and sulphur compounds).
With carbonated soft drinks, because the pH is low, bacteria are unlikely to grow in the finished, bottled soft drink. However it is recommended to maintain bacteria-free process water even after treatment and GAC filtration. This can be done by a second stage of ozonation as fruit juice-based soft drinks are bottled in the pH range of 6-7 and at this range bacteria can thrive and proliferate.
An ozone destructor may be necessary in fruit juice bottling if there is a possibility that residual ozone will impart off-tastes to the final drink by the oxidation of organic materials in the fruit juice.
- BOTTLING LINES
Several bottlers currently use ozone for “sanitising” the GAC filters and to eliminate the formation of chlorinated organic compounds. Over weekends, when the bottling lines are shut down and the plants are closed, the GAC filters are backwashed constantly with ozonised water to kill the bacteria on the GAC particles. Also the fill lines and vessels can be treated with ozone-containing water after shift shutdown. The following morning, the lines will be clean and safe to drain, as the ozone will have disappeared.
- CONCENTRATE WATER (PURE WATER)
Yet another application for ozone is in the process of preparing waters to accept concentrates or other ingredients. After the water has been “super ozonised”, treated with lime and ferric chloride and filtered, a small dosage of ozone (0.5-2 mg/L) is added to ensure an absence of micro organisms in the treated water during storage and up to the bottling time.
In situations such as Pharmaceutical lines where ultra pure water is required, ozone is an easy and effective method for sanitisation of pure water systems that does not require specialised operators skills. Because ozone disinfection is a continual process allowing very little chance of (re) contamination, many operators rely solely on the ozone treatment and have dispensed with regular shock disinfection with either steam or other chemicals.
An efficient way of producing ozone for ultra pure water applications is with an electrolytic ozone generator that actually produces ozone from the water being treated.
Ozone, (particularly electrolytically generated ozone), is ideally suited for pure water loops because only low concentrations are necessary to sanitise the system and there are no objectionable by-products or residue after the ozone has decomposed to oxygen.
This technique is already in use in pharmaceutical and other high purity water installations (e.g. electronic chip manufacturing).
Cross contamination from infected airborne particles can be prevented by using ozone during periods when the factory is vacant, to treat premises, air-conditioning, ducting etc.
If used during working hours sensors are recommended to maintain safe effective levels during working hours but this may be impractical in well ventilated areas.
- EFFLUENT TREATMENT
A common problem in factories is effluent containing high levels of COD’s. Ozone as an extremely effective oxidant is probably the most cost effective treatment method and is favoured over chemical or bio- filter methods in many circumstances.
Generally the ozone generator is supplied with a contacting system and ozone monitor. The contacting system enables direct connection in to the line through a venturi and the monitoring systems ensures adequate levels of ozone are applied and maintained.
In order to achieve high concentration levels it is often necessary to utilise oxygen as a feed gas. This can either be supplied from a bulk or bottle source or an oxygen generator. The high initial cost of the oxygen generator is invariably paid off in a short period of time through the savings in oxygen costs.
If the ozone generator uses air as a feedgas, this must be clean, dry and oil free. Thus an ozone generator fed from a conventional compressor will require a suitable drier and filter.
TYPICAL 20 GRAM OZONE GENERATOR SYSTEM LAYOUT
INCLUDING OXYGEN GENERATOR