3.2. Non-oxidizing biocides
Non-oxidizing biocides can be more effective than oxidizing
biocides owing to their overall control ofbacteria, algae
and fungi. Moreover, this type of biocides have greater persistence,
as many of them are pH independent. Frequently,
a combination of oxidizing biocides and non-oxidizing biocides
is used to optimize the microbiological control.
This group comprises of many chemical compounds such
as glutaraldehyde, acroleine, quarternary ammonium compounds,
isothiazolones, etc. The diversity of these compounds
is considerable and in general they must comply
with environmental regulations. Same as oxidizing biocides,
many of these compounds are toxic and they can have an
impact on the environment into which they are being discarded.
The choice of product and the best form of its application
are based on the characteristics of the system to be
treated, the operating conditions and How regime, and the
type of structural materials present in the system.
The forthcoming sections will give an account on some
non-oxidizing biocides used for microbiological control.
3.2.1. Glutaraldehyde
Glutaraldehyde is used as an active ingredient in a great
variety of commercial biocides applied to control fungi,
algae and bacteria (including sulfate-reducing bacteria in
bacterial biofilms). It is active over a broad range of temperature
and pH values. The functional group of glutaraldehyde
reacts with basic constituents of proteins (e.g. groups such as
–OH, –NH2, –COOH, and, –SH) present in cell membranes,
cell walls and in cytoplasm. Presently, the maximum concentration
of glutaraldehyde allowed by the United States
Environmental Protection Agency (USEPA) is 50 ppm. Glutaraldehyde
is soluble in water and insoluble in oil. Biocide
formulations can contain water, methanol, isopropanol
or their combination. These alcohols are added to increase
the penetrating capacity of glutaraldehyde and to avoid its
solidification during storage. Some products can contain
2–5% of quarternary ammonium compounds, which promote
the biocidal activity under certain conditions. Glutaraldehyde
is incompatible with alkaline substances or with
strong acids. In particular, it reacts strongly with ammonia
and substances containing amines, which can cause the
exothermic polymerization of glutaraldehyde. Quarternary
ammonium compounds are compatible with glutaraldehyde,
however, some products from this group are formulated with
other amines which can render the product incompatible. It
is therefore recommended to carry out compatibility tests
prior to the application of such compounds.
用翻译软件的，句子也要通顺，
如果遇到以下情况翻译不出的，做下调整
如oftemperature改为of temperature，e2ective改为effective
期待高手的帮忙