Biocides, biocidal additives

There is a current control system for certain types of biocidal products (known as non-agricultural pesticides) operated by HSE under the Control of Pesticides Regulations (CoPR). These are antifouling products, insecticides, wood preservatives and surface biocides. Additionally agricultural pesticides are controlled under CoPR but these are administered by the Pesticides Safety Directorate (PSD), an executive agency of the Ministry of Agriculture, Fisheries and Food (MAFF). 

It is said that cleanliness is next to godliness and manufacturing plants are no exception to this maxim. Many of the contamination problems that occur in manufactured products have their origins in poor plant hygiene, resulting in uncertain product, customer complaints and unnecessarily high biocide addition levels. 

THE ENHANCED PERFORMANCE OF BIOCIDAL ADDITIVES IN PAINTS AND COATINGS... 

Interpretation. The effective biocide treatment is the lowest concentration that produced sterility in the system within 7 days of biocide addition and inoculation. 

Biodispersants should be added just prior to biocide addition to create conditions for good biocide dispersion and penetration to take place. 

Biocides. The attack of fungi on the several components of a vinyl formulation may manifest itself as an unsightly growth looking much like dirt or may result in the formation of discolored areas (yellow, pink, blue, clear) on the finished goods. Outdoor exposure, indoor exposure in humid atmosphere, soil burial or contact, and electrical insulation compounds are typical areas where biocide addition is indicated. Since most commercial biocides are heavy metal derivatives, care must be taken to assess their effect on heat and light stability and compatibility with the vinyl system in which they are used. 

POLYMERIC ORGANOTIN BIOCIDE ADDITIVE FOR PAINT AND VARNISH MATERIALS... 

M. Manning. Borates as biocidal additives for WPC. In The Global Outlook for Natural Fiber and Wood Composites 2003, New Orleans, LA, December 3-5, 2003. 

GCP. [Betz Industrial] Biocides, additives for paint spray booths. 

The majority of biocide additives are used in flexible PVC. The remaining portion is used in polyurethane foam and other resins. PVC applications using biocides include flooring, garden hoses, pool liners, and wall coverings, among others. 

The use level of biocide additives depends on the efficacy of the active ingredient. OBPA, the most active, requires approximately 0.04% concentration in the final product. Less active ingredients, such as n-(trichloro-methylthio) phthalimide, require a loading of 1.0% in the final compound to achieve a similar level of protection. 

The enhance of long-term stability and service-abihty of the running tunnels of St. Petersburg Metro can be provided by the usage of specicil biocide additions to constructional and repair materials which must be an effective protection against biocorrosion in underground conditions of the city. 

Following extensive testing and evaluation, the biocide additive has been approved for food contact by the US organization NSF International. The certification means that the additive meets the requirements of ANSI/NSF Standard 51, covering safety of plastics materials and components developed for contact with food in the USA. The NSF mark can now be featured on products containing the ingredient and in promotional literature and will also encourage manufacturers of food equipment, who already hold NSF approval, to use the additive in their products. 

The chemical vendor will supply a biocide additive. The refinery will be responsible for adding chlorine. Controlled addition of biocide and chlorine will limit biological growth and prevent the buildup of slime in the exchanger tubes. Be careful to avoid excessive use of biocide. In one refinery biocide killed the "bugs" in the activated sludge section and was therefore responsible for a major upset at the effluent treating plant. 

Figure 5 Effect of biocide on Sphaerotilus natans biofilm. Arrows correspond to the start and stop of biocide addition.

Fuel-soluble biocides can be used to treat the contents of the whole storage tank, both fuel and water. As mentioned previously, these biocides are soluble in both phases at varying concentrations. These biocides can be added to a fuel storage tank as follows (1) through a port at the top of the tank, (2) premixed with fuel outside the tank and pumped back into the tank, (3) injected into a flowing stream of incoming fuel, or (4) added to fuel inside the tank to which more fuel will be added. If biocide solubility in fuel is low, the premix method of addition is not recommended. Methods of addition that insure uniform distribution of the biocide in the fuel and water bottom are obviously preferred. It is not recommended to add the biocide to an empty fuel storage tank. The tank should be at least 10% full prior to biocide addition. 

Figure 7 Adequate biocide protection is needed from the point of biocide addition at the refinery, through a typical fuel distribution chain, to...

Therefore, in laboratory testing, it is extremely important that the addition of biocide to the polymer dispersion copies as far as possible the conditions that would occur at the production plant. In almost every case a polymer dispersion sample that has been stored prior to addition of biocide will show less degradation of the bioeide than if the bioeide was added when the polymer dispersion was freshly made. This requires all additions of biocide samples to unprotected polymer dispersions to be made at the polymer dispersion plant or laboratory where the polymer dispersion is produced. As a consequence the additions must be made while the polymer dispersion is at the same temperature, pH and redox state that would occur during biocide addition to a production batch. 

If this is not followed, the results of laboratory trials may be misleading and will usually indicate a greater stability of the biocide than will be found in practice (Figure 12). For this reason, blank (biocide free) samples of polymer dispersion should not be used by test laboratories for biocide additions (Roden, 2002). 

Gibson, R., 2001. The enhanced performance of biocidal additives in paints and coatings Zeocros BIOO - Technical Paper, INEOS Silicas Ltd. 

In medium risk systems, regular preventative cleanings may take the place of or be done in addition to biocide addition. Single attached bacteria are easier to remove than full biofilm. This approach requires a cleaning system and unit downtime. It has a moderate chemical cost but is more labor intensive. Depending on the frequency required and the chemicals used for cleaning, membranes may degrade faster. ... 

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