Effectiveness of biocides and

Instead, interest is largely focused in two areas wood modification and heat treatment. Both approaches are more expensive than conventional pressure treatments and historically their use has been limited. However increasing concerns about the environmental effects of biocides, and the increasing costs of the biocides themselves has made these alternative approaches more attractive. Apart from Europe, currently they are limited to niche markets. 

A. Plant Systems. A system of null potential voltammetry was developed for investigating the effects of biocides and surfactants on the transport properties of leaf epidermal membranes. These membranes were obtained by a procedure which was found suitable for a wide variety of plant species. A residual translucent membrane composed of epidermal cells and the associated cuticular surface was exposed by gently rubbing the abaxial surface of the leaf with a moistened cotton-tipped applicator until all of the green material was removed. In these studies advantage was taken of the... 

Chlorine is desirable as a bulk pretreatment biocide for inlet water, but its subsequent removal upstream of the membrane is absolutely necessary ana difficult. NaHSO,3 is a common additive to dechlorinate before membranes. It is customarily added at 3-5 mg/1, an excess over the stoichiometric requirement. NH3 is sometimes added to convert the chlorine to chloramine, a much less damaging biocide. Heavy metals present in seawater seem to amplify the damaging effects of chlorine and other oxidants. 

M. J. Franklin, D. E. Nivens, A. A. Vass, M. W. Mittelman, R. F. Jack, M. J. E. Dowling, and D. C. White. Effect of chlorine and chlorine/bromine biocide treatments on the number and activity of biofilm bacteria and on carbon steel corrosion. Corrosion, 47(2) 128-134, February 1991. 

NOTE It is also recommended that a biocide efficacy test be performed annually on the cooling system water. This checks the effectiveness of a range of biocides and it enables the most cost-effective program to be in place. It provides a response to possible changing circumstances, such as the development of any resistant species. 

Jenkinson, D. S. and Powlson, D. S. (1976). The effects of biocidal treatments on metabolism in soil. V. A method for measuring soil biomass. Soil Biol. Biochem. 8, 209-213. 

Production equipment that cannot be sterilized must be sanitized and disinfected by an appropriate method. This can be done by use of biocides like alcohols (70%), hydrogen peroxide, or formaldehyde-based chemicals or a combination of these. These can either be used for surface disinfections by wiping or spraying or even better by use of gas or dry fog systems for application of the disinfectants. The effect of cleaning and sanitation should be monitored. Microbiological media contact plates can be used to test critical surfaces, as inside the hot cells or glove boxes. The test samples must then be handled and monitored as radioactive contaminated units. 

X-F. Zhon, G. H. Markx and R. Pethig, Effect of biocide concentration on electrorotation spectra of yeast cells, Biochim. Biophys. Acta, 1281, 60-64 (1996). 

Effect of Thermal and Chemical Biocide Treatments of Soil on Enhanced Microbial Activity... 

As with other biocides the effectiveness for a given concentration is very dependent on velocity, due to the effects of higher mass transfer effects at higher velocities. Kaur et a/ [1991] published data on the effect of velocity and are shown on Fig. 14.19. 

In Chapter 14 the use of additives to combat potential fouling was discussed. In the use of chemical treatment for cooling water there has to be an emphasis on effective and rapid dispersion since the concentration of the additives employed must be low, i.e. a few mg/l where possible, to minimise cost and to reduce potential pollution problems. In general the additive formulation will be based on the need to limit corrosion (i.e. the use of corrosion inhibitors), scale formation (i.e. the use of crystal modifiers, dispersants or threshold chemicals or a combination) and biofouling (i.e. the use of biocides and dispersants). In many installations additives are injected on the suction side of the main pump so that turbulence within the pump will provide rapid mixing. In very large cooling systems multiple injection nozzles will be required to enhance distribution. 

Sinclair CJ, Boxall ABA (2002) Assessing the Environmental Properties and Effects of Biocide Transformation Products. Cranfield University, Bedfordshire, UK Giesy JP, Solomon KR, Coats JR, Dixon KR, Giddings JM, Kenaga EE (1999) Rev Environ Contam Toxicol 160 1... 

Typically biocides are used intermittently as this has been found to constitute a more cost-effective use of biocides. However, the optimal addition cycle and point of addition will depend on the type of biocide and the design of the system. Typically the microbicide is added 4-8 times per day for 20 min to 1 h. It is often advantageous to combine two microbicides simultaneously or alternately. 

S. Ramesh, S. Rajeswari, S. Mamthamuthu, Effect of inhibitors and biocide on corrosion control of mild steel in natural aqueous environment. Mater. Lett. 57 (2003) 4547—4554. 

BD (biocide decay factor) is related to the loss of effectiveness of biocide with distance under actions of organic carbon and sulfides. 

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

Chemistry and Effects of Biocides on Aquatic Species Fish Control Lab Data Base Information ORNL FWS/DOI Public Public C C Acute effects of 1500 compounds on 8 species of fish 25-50 compounds have extensive information on 8 species under varied water conditions of temperature, pH, and calcium... 

A more recent important development in this field to decrease the rate of antifouling decay is the synthesis and use of polymeric materials containing organome-tallic toxicants chemically bound to the polymer backbone to provide a relatively low dose level of biocides and hence to extend the effective lifetime of antifouling protection [263-273]. 

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