Biocides, oxidizing bromine

PHMB is very toxic to fish and aquatic life. It is moreover irritating to skin and may cause sensitization by skin contact. It can cause irritation to the eyes, nose and respiratory tract. The PHMB is not compatible with most common swimming pool chemicals. Not compatible with chlorine and chlorinated chemicals and bromine donors. Not compatible with ionic sterilizers, copper based QAC-algicides, anionic detergents, water softening chemicals, persulfate oxidants etc. The defence of the inventors of PHMB is that one should not combine it with other biocides because it should be a bactericide/algicide. But the algicidal properties of PHMB are very weak in brochures and manuals the dose is 200 ppm. 

This formulation is suitable for use with oxidizing biocides, such as bromine. 

In practice, the required ratio can be different from theoretical, as quite often additional bleach is required to provide HOC1 as an oxidant for algal slimes and other forms of chlorine demand. Also, it is necessary to have a permanent source of oxidant available to effect the promotion of HOBr. However, not all the available bromine generated is lost by biocidal reaction or by (limited) volatility. There is, in fact, some degree of recycling of the bromide ion (Br ) back into HOBr, so monitoring of bromine plus the combined free and total chlorine is necessary to strike the correct halogen balance. 

Typically limit to 0.5 ppm total Fe maximum in the cooling water. Above this level, phosphonate can be used to control problems initiated by iron. However, if the total Fe rises to 3.0 ppm, adsorption of the phosphonate onto the iron takes place and a loss of inhibitor function can occur. Iron salts present a serious fouling risk in cooling systems. Dissolved iron quickly oxidizes (especially where chlorine, bromine, or other oxidizing biocides are used) and forms ferric oxide/hydroxide, which acts as a flocculant,... 

Crosslinked chloromethylated PS beads were reacted with hydantoin and imidazolidinone derivatives to produce functionalised beads which could be rendered biocidal by reaction with free chlorine or bromine. The biocidal efficacies of the N-chlorinated and, in one case, the N-brominated polymeric beads against Staphylococcus aureus or Escherichia coli 0157 H7 in aqueous suspension were determined. The N-halogenated polymeric beads were effective in aqueous disinfection application, requiring short contact times for inactivation of the two bacteria. The functionalised polymers could be tailored to the application, depending on whether rapid biocidal activity or long-term stability to loss of oxidative halogen was desired. 11 refs. (Pt.III, ibid, p.363-7)... 

Halogenated (mostly Cl and Br) biocides (such as hypochloride or DBDMH, see Tab. 6.3-1) are the most commonly used chemicals for sanitizing water. They are strong oxidizers and, as dust and products of decomposition (below), irritate respiratory tracts. Therefore, airborne, inhalable fine particles and all dust must be avoided. This is also true for non-chlorine (or bromine) oxidizers that are used for the same... 

Biocides such as chlorine dioxide and bromine compounds (oxidizers) are used for sterilization. The biocides might interfere with the performance of inhibitors and hence the concentration of biocides must be controlled. 

Another bromine system used primarily in spas is a two-part system consisting of sodium bromide [II, 21.2.3a.] and an oxidizer. Whichever bromine product is used, the active biocide produced is hypobromous acid. The high cost of bromine and instability to sunlight makes its use for outdoor pools relatively uneconomical. 

Reactions with ammonia and organic compounds. Hypobromous acid reacts with amines to form bromamines in a manner similar to ehorine. However bromamines are efficacious as sanitizers in recreational water, unlike chloramines which are biocidal, but of limited value due to their slow rate of kill. Additionally, bromamines are not irritating to the skin and eyes and do not possess a strong odor. Breakpoint bromination is not required. Re-oxidation of the inactive bromide ions will re-convert the salt to biocidal form (HOBr/OBr ). These qualities make bromine biocides much more favorable products for use in spas, relative to chlorine. Bromine products are primarily used for treating indoor pools and spas. Chemicals used for the neutralization of hypobromous acid are identieal to those used for hypochlorous acid. 

Bromine, iodine and BCDMH (l-Bromo-3-Chloro-5, 5-dimethylhy-dantoin) are oxidizing biocides similar in action to chlorine, but they are weaker and removal of residual is more complex. They are significantly more expensive than hypochlorite, but BCDMH comes in a sohd form, which may provide advantages for certain systems. ... 

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