Question of the Day: Oxidizing Biocides

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Question of the Day: Oxidizing Biocides
How do oxidizing biocides work to control microbiological growth in water systems?

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8 Answers

  1. Following on from the use of powerful oxidising agents being (relatively) indescriminate in their disruption of cells to reneder them non-viable.  My feeling is that "clean" oxidants eg ozone, which don't leave halogenated organics behind, may have an increasing role to play in both disinfection and the avoidance of Anti Microbial Resistance (AMR).

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    1. "Resistance" is futile for oxidizers: one cannot develop a resistance to bullets and bombs. Ozone is indeed a great oxidant, like all oxidizers it has pro's and con's. it's primary con's include bromate formation, elevated corrosion rates, and insolubility above 94 DegF.

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  2. Since the previous answers were technical, let's get a little descriptive: oxidizing biocides are like machine-guns or bazookas. They indiscriminately lay waste to all in their path. 

  3. Oxidizing biocides take in electrons. Mode of action in case of chlorine dioxide and Ozone is that they rupture the cell wall and then burst the nucleus and not leaving any microorganisms behind, thus developing no immunity or mutations of the bugs rendering the biocide effective.

  4. Since the active components of oxidizing biocides are acidic in nature (with the notable exception of hydrogen peroxide), it is no surprise at all that the system pH plays a role in biocide effectiveness.

  5. Its important to note that oxidizing biocides are consumed in a somewhat quantitive relationship with the target organism. The common term is "demand" which basically is the differential between the amount of biocide added and confirmed (tested) residual assuming adequate contact and reaction time. However, the by-products of the reaction commonly referred to as "disinfection by-products" (DBP) continue to have diminished biocidal properties. 

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  6. Both Clive's and John's answers are correct, John has simplified it.  To put it plainly, as one of my mentors used to say, they simply burn the cell walls.

  7. Oxidizers are primarily acids i.e. HOCl, HCl, HOBr, HBr etc. The outer cell wall is anionic , the acid reacts and burns a hole in the cell wall causing the loss of osmonic pressure