Biocides applications

This process reduces the amount of control biocide employed in the control of contamination of oil production system waters by sessile bacteria. The biocide may be applied at intervals of 2 to 15 days. The duration of biocide application is preferably from 4 to 8 hours [1244]. 

Combined Chlorine-Aldehyde Treatment A combined chlorine-aldehyde treatment that has two stages, that is, chlorination and subsequent biocide application, has been suggested. Short-residence-time shock doses of glutaraldehyde have been applied after chlorination [1180]. It has been established that a primary chlorination in overall bacterial control is useful. 

S. Maxwell, K. M. McLean, and J. Kearns. Biocide application and monitoring in a waterflood system. In Proceedings Volume, pages 209-218. Inst Petrol Microbiol Comm Microbial Problems in Offshore Oil Ind Int Conf (Aberdeen, Scotland, 4/15-4/17), 1986. 

Some common compounds which are approved for various fuel-water biocide applications include glutaraldehyde, methylene bis-thiocyanate and 2-methyl-4-... 

For optimum benefit, the biodispersant should be part of a planned biocide application, where genuine need for a periodic addition to the cooling water has been demonstrated, or as part of a step-by-step cleanup program. The dose rate for periodic additions is probably around 25 to 50 ppm (30% active) and perhaps as high as 75 ppm for cleanups. 

It is vital to know the correct system volume and to fully understand the biocide application program. Biocidal control is often the weakest area of any competitor s program. When putting together a new biocidal program, volume requirement calculations based on incorrect information can have a significant and detrimental effect on cost. 

Are there areas of technical improvement or cost savings that could be made in the biocide application and monitoring regimen ... 

Today, automatic biocide application, actuated by reference to real-time biofouling monitoring equipment, is available in some countries and may provide better (if very expensive) microbiological control than 7- to 28-day timer-controlled systems. 

The regular use of sodium pentachlorophenate has proved successful in many instances, but it is a persistent environmental hazard and cannot be recommended. However, o -benzy 1-p -chlorophenol can often produce goods results, with low bacteria counts and clean systems. But the timing of biocide applications needs to be matched carefully with the production cycles (and process leakage periods) for optimum product effectiveness. 

These results at once suggested a number of possibilities for practical applications, in the first place of course as fungicides, but, on the basis, of anticipated wider biocidal, in particular antimicrobial effects, of quite different biocidal applications as well. These expectations have been fulfilled remarkably well. Later on in this paper I shall briefly survey the present-day applications of organotin compounds as fungicides and as biocides in a more general sense. 

In reconsidering the biocidal properties of organotin compounds, one cannot get away from the conclusion that the biocidal applications are likely to expand strongly in the future, both as a result of an extension of the present possibilities and of the development of new ones. 

Biocidal applications. The use of quaternary ammonium salts in disinfecting systems for household and industrial cleaners has been known for many years [95, 96]. Alkyl-benzyldimethyl quaternaries, alkyltrimethyl quaternaries, and dialkyldimethyl quaternaries are the more commonly used biocidal quaternary ammonium salts [16]. Recently, dialkyldimethyl quaternary ammonium salts have received renewed attention as potential wood preservatives to replace the heavy metal types [97]. Metal-free wood preservative formulations containing dialkyldimethyl ammonium salts with non-halide anions, such as carboxylates, borates, and carbonates, have been developed [98, 99]. 

As part of the NAFTA Technical Working Group on Pesticides, priority areas for development of biocide applicator data have been agreed upon. These include, in order of priority, high-pressure spray, low-pressure spray, painting (roller/brush), wipe/mop, place solids, aerosol spray, painting (airless), pour solid, pour liquid and pump liquid. 

Medicinal/Biocidal Applications of Tin Compounds and Environmental Aspects... 

Temperature will affect chemical reactions in wMch the biocide takes part either with other constituents in the water, or through simple temperature related decomposition. Fig. 14.12 and Fig.14.13 show the stability of glutaraldehyde as a function of temperature at two different pH values [Henry 1993]. The change of pH from 7 to 8 makes a considerable difference to the stability of the biocide at 82°C. In general of course, for cooling water applications, temperatures much above 55°C are not likely to be encountered so it has to be stated that the effects of temperature on the stability of glutaraldehyde may not be important in biocide applications. 

The aldehyde groups are chemically reactive and in biocide application reaction is with primary amine groups. It is generally applied in aqueous solution where glutaraldehyde exists in a complex equilibrium mixture of different hydrated forms. 

Titanium dioxide-based photocatalysis for water purification has been the focus of a large volume of research over the past twenty years. In spite of that fact, only a few studies have explored its possibilities for biocidal applications (Stuart et ai, 2003, Kabir et al, 2003). 

Eor biocidal applications, the quantum yield efficiency can be modified by introducing an inactivation quantum yield (IQY), as described in equation (9-13). For E. coli, the IQY values were calculated with initial rates of inactivation, assessed after the 3-minutes lag phase period. 

L/S and Ue models can also be used to detect the effect of biocide application. 

HOCl is a strong oxidizing agent ( hoci/ci- = 1-49 V, pH = 0) in acid but not in alkaline solution. Hence, oxidation goes only from HOCl or its protonized form HOCIH" with the direct transfer of Cl (chlorination), similar to the reaction of HOBr and HOI. It disproportionates into chloride and chlorate singlet oxygen is then partly formed, which can oxidize organic compounds (the biocide application of hypochlorite is based on this) ... 

Anionic surfactants are little used in breweries while cationic surfactants such as quaternary ammonium compounds are employed for certain biocidal applications. Ampholytic (amphoteric) surfactants are also used as biocides and like the quaternary ammonium compounds they have to be rigorously... 

Most of this growth in biocides is attributed to increased consumer awareness. The end-use customers are now demanding that nontradi-tional biocide applications, like door handles, hospital chair rails, garden hoses, and blue ice packs, incorporate biocides to protect them from germs. Consumers seem, in some cases, to be misinformed about the true function of a biocide since it is intended to protect the plastic. 

The use of onium salts containing both long and very short alkyl chains, such as hexadecyltrimethylammonium bromide, will promote stable emulsions in some reaction systems, and thus these are poor catalysts. They remain popular, however, as their surfactant and biocide applications make them cheap and readily available. 

---