Industry Bio Cide s

8/12/2019 Industry Bio Cide s

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Industry biocides

Biocides are often misapplied in the industry. Many of the misapplications occur becausethe characteristics of the biocides are not considered before use. In this article we reviewthe major biocide types and summarize their properties. Some of the guidelines forbiocide selection are outlined. Biocides are the most underused, misunderstood, andmisapplied chemical products in the industry for many reasons.

Biocides are used to combat a problem that is subtle and difficult to detect. Very fewsimple and reliable means of monitoring are available to the supplier or the end user, andthe benefits of biocide used tae a long time to become evident. !inally once bacteria arewell established in a system, their eradication is nearly impossible without drasticmeasures. "arly detection of microbiological problems is imperative, and remedialmeasures must be taen as soon as possible. #hese measures should include changes inoperating methods to prevent degradation of the operating environment. #his mightinclude rejection of untreated waters or cleaning of deposits in vessels and lines. Ingeneral, biocides are needed to control the activity of the bacteria in a system. $oweverbiocides alone usually will not solve a microbiological problem.

#ypes of BiocidesBiocides can be classified broadly into two groups% o&idizing biocides and non'o&idizingbiocides. In general, o&idizing biocides are used only in freshwater systems because theiractivity is rapidly consumed by organic matter in produced waters. #he non'o&idizingbiocides cover a wide spectrum of chemical compounds that can be used in many differenttypes of environments.

(&idizing biocides

)hlorine)hlorine *)l+ reacts with water to form hypochlorous acid. $ypochlorous acid dissociatesto hypochlorite ion *()l', which is the biologically active species. )hlorine functions bestwhen p$ is between - and .)hlorine is used widely in freshwater systems/ it is often injected at the water source tomaintain control of microbiological populations throughout the system. )hlorine iseffective against many micro'organisms. $owever decades of chlorination have causedthe effect of resistance building and the reactivity of chlorine is a disadvantage whenattempting to disinfect biofilms. #he chlorine consumed in reactions with organic matterand iron in the biofilm and it thus is unavailable for illing bacteria.

)hlorine production involves the use of mercury 0 a very polluting substance and negativeby products e.g. #ri$aloMethans. #hese #$M1s trigger the production of free radicals in thehuman body, causing cell damage and are considered to be carcinogen. #he reactorre2uired for chlorine production is a hazard factor involving special security measures andpolicies. 3ast but not least chlorine is a carcinogen. #he general attitude towards chlorineis to decrease the use. ".g. governments in the ") have a tendency to move to otherbiocides to avoid all the use, health and environmental riss.

)hlorinating )ompounds)hlorinating )ompounds include bleach *sodium hypochlorite solution 45a()l6 and calciumhypochlorite *dry chlorine 4)a*()l+6. #he use of these materials avoids the dangers and

#win(&ide 7ustralia 8ty 3td. 9+: Mc"wan ;oad $eidelberg -9 : ?@A 9=9= "'mail% infotwino&ide.com.au


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inconvenience of handling chlorine gas, but the materials are bulier. #he addition of largeamounts of calcium might also create the scaling problems in some systems. Monographsare available to calculate the amounts of chlorinating compounds re2uired to produce thehypochlorite ion in concentrations e2uivalent to those produced by chlorine.

)hlorinating compounds are as effective as chlorine re2uire larger 2uantities than whenusing chlorine but are suspected to be carcinogen. #he general attitude is e2ual tochlorine.

)hlorine Cio&ide)hlorine Cio&ide *)l(+ is a very effective o&idizing agent that can be used to remove

organic materials, biomass and iron sulfide deposits from a system. #his maes its use indown attractive. )hlorine Cio&ide is effective in a wider p$ range than hypochlorite and isless affected by organic material and ammonia.

#raditionally )hlorine Cio&ide must be generated on site. #hree precursors are generallyused to produce chlorine dio&ide% sodium hypochlorite *5a()l, hydrochloric acid *$)l,and sodium chlorite. 7 two'stage reaction process is re2uired. #he first stage involvesreacting 9AD $cl and 9=D 5a()l to produce -D a2ueous chlorine%

+$)l > 5a()l E )l*a2 >$+( > 5a)l

#he -wtD chlorine is then reacted with sodium chlorite%

)l *a2 > +5a)l(+ E +)l(+ > +5a)l

)hlorine Cio&ide is a very FfastG biocide.


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#win(&ide has all the positive characteristics from )hlorine Cio&ide with e&tra featuresamongst which are%

5o reactor re2uired for generation of )l(+ 5on gaseous but a )l(+ solution 5on'e&plosive 7pplicable in p$ levels between @ 0 9= "ffective against biofilm and all in water common bacteria 5o resistance building 5on corrosive Shelf life characteristics "asy to transport, simple to handle

5o $M1s, 5o free chlorine, chlorite, chlorate or chloride "asy application by standard dosing e2uipment 5o hazard to health or the environment 8ure, clean and approved for application in drining water +-=D more biocidal power than chlorine 7t least 9= times more o&idizing power than chlorine

)hloramines)hloramines *e.g. ammonium chloride or monochloramine 45$+)l6 are a reaction productof hypochlorous acid and ammonia. 7mmonia is added at a :'to'9 ratio to injectedchlorine, and 9 ppm of monochloramine is formed per each ppm of chlorine

Monochloramine has less than AD of the disinfecting power of chlorine *JJ on atimeKconcentration basis. $owever, mono'chloramine is more effective than chlorine forpenetrating biofilms and illing bacteria because it is not reactive enough to be consumedby other biofilm constituents, and thus is available for disinfection. (nce bacteria are wellestablished in a system, their eradication is nearly impossible without drastic measures.

)hloramines are relatively corrosive and re2uire the injection of ammonia and consideredcarcinogen.

BromineBromine *Br+ is analogous to chlorine. Lenerally it is used in the form of a solid compound*9'bromo':'chloro'A,A'dimthylhydantoin, which releases bromine hydro&ide and chlorine

hydro&ide into the water.

Bromine is more effective than chlorine at a higher p$ level but has the negative sideeffects of chlorine and in addition to that bromate is a side product that is considered acarcinogen.



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8eracetic 7cid7cetic 7cid is a reaction product of peracetic acid. #he 7cetic 7cids are a very usefulnourishment for micro organisms ' therefore bacteria growKenlarge more after usingperacetic acids. 8eracetic 7cids belong to the group of organic pero&ides% )lass A.+KAb 0these are e&tremely dangerous classes. 8eracetic 7cids are a derivate of hydrogenpero&ide and the disinfection spectrum is very limited. 8eracetic 7cid is disrupted veryfast by catalysts *e.g. rust, dust, metals and accidents will happen when a piece of metal*nail, screws, coin, pen etc drop into a vessel with peracetic acid. In such case the vesselwill e&plode spontaneously as the peracetic acid immediately reacts. #herefore the waterto be disinfected should contain very few iron and manganese.

5on o&idizing biocides

!ormaldehyde!ormaldehyde *$)$( is used generally as an a2ueous solution *:HD. It has restrictedapplications because high doses are re2uired for it to be effective. It reacts with ammonia,hydrogen sulfide and o&ygen scavengers. !urther it is highly carcinogen and forbidden inmany countries.

LlytarealdehydeLlytarealdehyde *pentanedial, ()$4)$+6:)$( is used widely in the petroleum industry. Itis sometimes used in a blend with other biocides or surfactants to increase effectiveness.

It is insensitive to sulfide, non'ionic *compatible with other chemicals and tolerates saltsand hardness. It is de'activated by ammonia, primary amines and o&ygen scavengers.

7crolein7crolein *$+))$)$(/+'propenal is a highly reactive material that is an effective biocideand sulfide scavenger. It is a gas at ambient temperature and e&tremely irritating to eyesand mucous membranes and re2uires careful handling. Injection taes place by pumpingor displacement using o&ygen'free nitrogen.

7crolein is a broad'spectrum biocide and penetrates deposits and dissolves sulfideconstituents. It is difficult to handle reacts with polymers, scavengers, etc. and is highlyto&ic.

7mine 0 type compounds

Nuaternary amine compoundsNuaternary amine compounds *4;9 ;+ ;: ;@ 56 > OP have been used for many years inthe industry. #he products are generally used in low' total dissolved solids water. Lenerallythese compounds function best at alaline p$ levels. Nuaternary amine compounds havepersistence and have low reactivity with other chemicals. #hey are inactivated in brines,are foaming and have a slow acting.

7mine and diamine biocides

#he most commonly used amineKdiamine *;'5$+, ;' 5$';'5$+ is the cocodiamine. #hesematerials usually are neutralized with an acid, such as acetic acid, to form a water soluble



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salt. #hey have some inhibition properties, are effective in sulfide'bearing waters but reactwith other chemicals, particularly anionics and they are less effective in water with highlevels of suspended solids.

$alogenated compounds

Bronopol*):$-Br5(@, +'brono'+' nitropropane'9,:dioV is a dry product sold as a powder orcompressed into a solid stic. It has been used in drilling and completion fluids as well asproduced fluids in the oil industry. It has the ability to degrade is low to&ic to humans and

it breas down in high p$.

7nother compound, CB587 *+'+'dibromo':nitrolo propionamide )$Br+)5)(5$+, also hasbeen used. CB5871s are fast acting and effective but are affected by sulfides.

Sulfur compounds

Isothiazolone*)@$@5()lS has been used for several yearsto ill bacteria. It is inactivated by sulfide, soit is considered to be not effective in illing sulfate'reducing bacteria *S;B in maturebiofilms. It is compatible with brines and it is degradable but cannot be used in acid p$.

)arbamates*alyl thiocarbamates may be a better choice than isothiazolone in some circumstancesas they are effective against sulfate'reducing bacteria *S;B and spore formers, areeffective in alaline p$ and are useful for polymer solutions. It is re2uired in highconcentrations and reacts with metal ions and other compounds.

Metronidazole*+'methyl'A nitroimidazole'9' ethanol is only effective against anaerobic organisms and itis effective against sulfate'reducing bacteria *S;B and compatible with other chemicals

Biocides selection

Biocides must be selected according to several criteria amongst which are% "ffectiveness% 7bility to ill plantonic bacteria, ability to ill bacteria, minimum

concentration and contact time. Safety% personnel ris assessment *for insurance, to&ic gases or physical contact

neutralization re2uirements registration, discharge to environment andpersistence.

)ompatibility with system fluids% solubility, partition coefficient, p$, presence ofhydrogen sulfide, temperature hardness, presence of metalions or sulfates, level oftotal dissolved solids.

$andling% "asy of use corrosiveness to metals and elastomers, freeze point,

thermal stability, separation of components, shelf life, storage re2uirements



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)onclusion

7 wide range of products is available to control microbiological activity in systems. #hespecific product application must be carefully considered and all the relevant factorsevaluated before designing the chemical program. 3aboratory screening and fieldmonitoring are necessary to ensure the level of success of the biocide program.

;eferences

S.C. !aust, (.M. 7ly, )hemistry of

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Industry Bio Cide s