Oxidative Biocides Research Articles

Impact of artificial accelerated ageing of PVC surfaces and surface degradation on disinfectant efficacy

Standardised efficacy surface tests for disinfectants are performed on pristine surfaces. There is a growing interest in understanding the impact of surface ageing on disinfectant activity, owing for example to the increased usage of UV radiation and oxidative chemistries for surface decontamination. This acknowledges that general surface "wear and tear" following UV radiation and oxidative biocide exposure may impact biocidal product efficacy. PVC surfaces were aged through thermal and UV-A radiation (340nm wavelength) following the use of standard ageing surface protocols to simulate natural surface degradation. Surface roughness, contact angle and scanning electron microscopy were performed to evaluate physical changes in PVC surfaces before and after artificial ageing. The efficacy of five pre-impregnated disinfectant wipes were evaluated using the ASTM E2967-15 on stainless steel (control) and PVC surfaces (aged and non-aged). The type of formulation and the organism tested remained the most significant factors impacting disinfectant efficacy, compared to surface type. Both thermal ageing and UV-A exposure of PVC surfaces, clearly showed signs of surface degradation, notably an increase in surface roughness. Physical changes were observed in the roughness of PVC after artificial ageing. A difference in disinfectant efficacy dependent on aged PVC surfaces was observed for some, but not all formulations. We showed that surface type and surface ageing can affect biocidal product efficacy, although in a non-predictable manner. More research is needed in this field to ascertain whether surface types and aged surfaces should be used in standardized efficacy testing.

The Influence of Oxidizing and Non-Oxidizing Biocides on Enzymatic and Microbial Activity in Sugarcane Processing

Processing aids are utilized during raw sugar manufacturing at sugarcane processing facilities to mitigate unwanted contamination from microorganisms and their associated exopolysaccharides (EPS). Microorganisms in processing facilities contribute to sugar losses through sucrose inversion and consumption, with many bacteria strains subsequently producing dextran and fructan EPS that can cause downstream issues related to viscosity and crystallization. Similar issues also result from the presence of unwanted starches from plant material in cane juices. Processing aids include biocides for bacterial inhibition, and enzymes (e.g., dextranase, amylase) to break down polysaccharides in juices. However, oxidizing biocide processing aids (e.g., sodium hypochlorite) may inhibit enzymatic processing aid activity. In this study, biocides (sodium hypochlorite, carbamate, and hop extract) and enzymes (dextranase and amylase) were simultaneously added to sugarcane juice to measure residual enzymatic activity for dextranase and amylase. The same biocides were also tested to estimate minimum inhibitory concentrations against bacterial strains isolated from Louisiana sugarcane processing facilities. These experiments provide evidence to suggest that sodium hypochlorite may interfere with enzymatic processing aid activity, with lesser/limited enzymatic inhibition from carbamates and hop extracts. Biocide susceptibility assays suggest that sodium hypochlorite has limited effectiveness against tested bacterial strains. Hop extract biocide was only effective against Gram-positive Leuconostoc while carbamate biocide showed more broad-spectrum activity against all tested strains.

Batch and continuous bleaching regimen in the cooling tower of Montazer Ghaem power plant

In order to control the microbial growth in the cooling tower of thermal power plant, oxidative and non-oxidative biocides are applied in the power industry. Oxidative biocides including chlorine dioxide and bromine-based compounds are effective for controlling microbial growth in cooling towers. The choice of biocide depends on the type of cooling tower, water quality, and regulatory requirements. In the most cases, the bleaching regimen is selected as the most effective and low-cost oxidative biocides in cooling tower. The bleaching regimen is carried out in batch mode generally and herein for the first time, the continuous bleach is examined in the cooling tower of Montazer Ghaem power plant by evaluating the microbial growth. In the batch mode, 0.25 m3 of 12% bleach is injected into 1600 m3 every 3 days and in the continuous mode, the same amount (0.0035 m3/h) is continuously injected. The TBC11Total Bacteria Count in the cooling water before bleach, after batch and continuous bleach are 106, 104 and 103 cfu/mL, respectively. In fact, the performance of the continuous bleach is 10 times more efficient than the batch bleach. The physicochemical parameters including conductivity, NaCl%, TDS, pH, anions and cations concentration are not changed significantly and the chemical conditions are stable in both regimes which is proved that changing the bleach injection does not require the different chemical control. The free chlorine concentration in the continuous mode is constant (0.05 ppm) which is controlled the microbial growth and avoided the copper and iron corrosion.

In Vitro Antibacterial Activity of Waste Palm Cooking Oil Against Staphylococcus Aureus

Background: Staphylococcus aureus is a Gram-positive coccus which acts as a pathogen causing awide range of infectious diseases. In recent years, several strains of S. aureus have been found to showresistance to several antibiotics. Waste cooking oil may be considered as an alternative antibacterialproduct, as it contains long-chain fatty acids whose antibacterial effectiveness against S. aureus hasbeen known for years. In addition, oxidative biocides produced during the frying process have manytargets for antibacterial activity in the cell and affect almost every biomolecule. Nonetheless, there isno literature that is able to prove the antimicrobial effects of the waste palm cooking oil. Objective: Toexamine the in vitro antibacterial effect of waste palm cooking oil against S. aureus. Method: a twofoldserial dilution method to set the minimum level of both inhibitory and bactericidal concentrations.Conclusion: This study showed that waste palm cooking oil did not show antibacterial effects againstS. aureus, indicating that waste palm cooking oil is not possibly to be applied as an antibacterial agentagainst S. aureus.

Pomacea canaliculata Ampullar Proteome: A Nematode-Based Bio-Pesticide Induces Changes in Metabolic and Stress-Related Pathways.

Simple SummaryPomacea canaliculata is a South American invasive freshwater snail, affecting biodiversity, crop production and public health, now retrieved in Asian, North American and European countries. The identification of molecules connected to P. canaliculata adaptability may prove helpful in developing strategies that could overcome the snail’s resilience and stop its spread in non-original countries. This research presents the changes occurring in the proteome of a small organ, i.e., the ampulla, after challenging the snails with a nematode-based bio-pesticide. Transmission electron microscopy (TEM) analysis demonstrated that this organ has a complex connective ultrastructure and contains rhogocytes. TEM also confirmed the ampulla as a deposit of nitrogen-based material. After exposure to the nematode-based bio-pesticide, significant changes were observed for enzymes mainly involved in antioxidant defence, energy metabolism and cytoskeletal dynamics. These changes recall the systemic oxidative stress response that the snails undergo during the arousal after aestivation/hibernation, a physiological response involving other organs that, similarly to the ampulla, store nitrogen-based compounds. As fundamental players of the response against bio-pesticides and environmental cues, the enzymes identified in this research and involved in stress-related pathways may represent a suitable target for the efficacious and sustainable control of P. canaliculata spread.Pomacea canaliculata is a freshwater gastropod known for being both a highly invasive species and one of the possible intermediate hosts of the mammalian parasite Angiostrongylus cantonensis. With the aim of providing new information concerning P. canaliculata biology and adaptability, the first proteome of the ampulla, i.e., a small organ associated with the circulatory system and known as a reservoir of nitrogen-containing compounds, was obtained. The ampullar proteome was derived from ampullae of control snails or after exposure to a nematode-based molluscicide, known for killing snails in a dose- and temperature-dependent fashion. Proteome analysis revealed that the composition of connective ampulla walls, cell metabolism and oxidative stress response were affected by the bio-pesticide. Ultrastructural investigations have highlighted the presence of rhogocytes within the ampullar walls, as it has been reported for other organs containing nitrogen storage tissue. Collected data suggested that the ampulla may belong to a network of organs involved in controlling and facing oxidative stress in different situations. The response against the nematode-based molluscicide recalled the response set up during early arousal after aestivation and hibernation, thus encouraging the hypothesis that metabolic pathways and antioxidant defences promoting amphibiousness could also prove useful in facing other challenges stimulating an oxidative stress response, e.g., immune challenges or biocide exposure. Targeting the oxidative stress resistance of P. canaliculata may prove helpful for increasing its susceptibility to bio-pesticides and may help the sustainable control of this pest’s diffusion.

1230. Estimating Effective Point-of-Use Biocide Levels for Legionella Control in Building Water Systems Using a Large, Real-World Dataset

BackgroundLegionnaires’ disease is a potentially life-threatening illness often associated with Legionella growth in water sources. Oxidizing biocides, such as chlorine (CL), monochloramine (MC) and chlorine dioxide (CD), can reduce Legionella contamination. However, limited guidance exists regarding optimal target biocide levels in building water systems to prevent Legionella growth. We examined Legionella and biocide data collected by Department of Veterans Affairs medical facilities nationally to estimate effective biocide levels.MethodsWater samples collected at point of use for routine surveillance purposes between 2015 and 2017 were used for this analysis. Samples were limited to those with reported biocide being CL, MC or CD. Samples with biocide levels above safe drinking water maximums and from nonpotable water sources were excluded. Samples were stratified by hot and cold water and univariate logistic generalized additive models were used to assess nonlinear associations of probability of Legionella positivity and biocide level.ResultsThe dataset included 144,458 samples (cold: 72,674; hot: 71,784) from 789 buildings at 168 hospitals, with 99,419 samples with reported biocide as CL, 40,922 as MC, and 4,117 as CD. For CL, cold water analysis showed a minimum probability of positivity at approximately 0.5 parts per million (ppm), but with a second minimum at 2 ppm. Hot water showed an inflection point around 0.6 ppm, but the likelihood of positivity continued to decrease until plateauing beyond 2 ppm (Figure 1). Cold water with MC showed a minimum probability of positivity at 0.3 ppm followed by a second minimum at 1.7 ppm with plateau beyond that concentration. Hot water showed a similar graph with initial minimum at 0.25 ppm and a second minimum at 1.6 ppm (Figure 2). CD graphs for both hot and cold showed a decrease at 0.2 ppm (Figure 3).ConclusionThe variability in the dynamics of Legionella inhibition by different biocides as seen in our analysis indicates minimum biocide targets for the different agents. For CL and MC, biocide levels >2 ppm at point of use in building water systems may not provide added benefit for suppression of Legionella. Disclosures All authors: No reported disclosures.

Upregulation of peroxide scavenging enzymes and multidrug efflux proteins highlight an active sodium hypochlorite response in Pseudomonas fluorescens biofilms

The oxidative biocide sodium hypochlorite is among the most commonly used antimicrobial agents in the control of surface-attached microbial communities (biofilms). Clarifying the genetic response of microorganisms in biofilms to hypochlorite may contribute to improved biofilm control strategies. Here, RNA-seq was used to investigate the differential gene expression response of industrially relevant Pseudomonas fluorescens biofilms to sub-lethal concentrations of sodium hypochlorite. Pseudomonas biofilms responded to hypochlorite exposure with increased transcription of genes encoding peroxide scavenging enzymes (e.g., alkyl hydroperoxide reductase (Ahp) and hydroperoxide resistance protein (Ohr)), oxidative stress repair enzymes (e.g., the periplasmic sulfoxide reductase YedYZ complex), and multidrug efflux (e.g., MexEF pumps). In addition, genes involved in amino acid synthesis and energy metabolism were down-regulated following hypochlorite exposure. This work improves the current understanding of genetic response mechanisms to biocides and contributes to the optimization of biocides and application strategies.

Biofilm Surface Density Determines Biocide Effectiveness.

High resistance of biofilms for chemical challenges is a serious industrial and medical problem. In this work a gradient of surface covered with biofilm has been produced and correlated to the effectiveness of different commercially available oxidative biocides. The results for thin Escherichia coli biofilms grown in rich media supplemented with glucose or lactose on glass or poly methyl methacrylate surfaces indicate that the effectiveness of hydrogen peroxide or chlorine dioxide and quaternary ammonium compounds is inversely proportional to the fraction of the surface covered with the biofilm. In areas where biofilm covered more than 90% of the available surface the biocide treatment was inefficient after 60 min of incubation. The combined effect of oxidant and surfactant increased the effectiveness of the biocide. On the other hand, the increased biofilm viscoelasticity reduced biocide effectiveness. The results emphasize differential biocide effectiveness depending on the fraction of the attached bacterial cells. The results suggest that biofilm biocide resistance is an acquired property that increases with biofilm maturation. The more dense sessile structures present lower log reductions compared to less dense ones.

Sustained antimicrobial activity and reduced toxicity of oxidative biocides through biodegradable microparticles.

The manuscript explores a novel approach to utilize the antimicrobial activity of oxidative species for sustained killing of multiple drug-resistant organisms without causing collateral tissue damage. The results demonstrate, for the first time, the ability to load pre-cursor compounds into porous polymeric structures that results in their release and conversion into oxidative species in a controlled manner. Until now, the use of oxidative species has not been considered as a candidate therapeutic replacement for conventional antibiotics due to difficulties associated with handling during manufacture and controlling sustained release without causing undesirable tissue damage. The ultimate impact of the research could be the creation of new materials-based anti-infective chemotherapeutic agents that have minimal potential for giving rise to antimicrobial resistance.

Biofilms and Oxidizing Biocides; Evaluation of Disinfection and Removal Effects by Using Established Microbial Systems.

The formation of bacterial biofilms and their disinfection and removal have been important subjects in the maintenance of water quality in areas such as public spas, swimming pools, food processing lines, industrial water systems, and in the hygienic control of medical devices, hospital procedures, etc. Presented here is an outline of biofilm formation, as well as studies on the disinfection and removal of biofilms by oxidizing biocides using established biofilms. These studies using established biofilms may increase the understanding of the variable response of biofilms to planktonic bacteria, and the unique aspects of oxidizing biocides in the disinfection and removal of biofilms.

Epidemiological, Physiological, and Molecular Characteristics of a Brazilian Collection of Carbapenem-Resistant Acinetobacter baumannii and Pseudomonas aeruginosa.

Nonfermenting Gram-negative bacteria such as Pseudomonas aeruginosa and Acinetobacter baumannii are widespread in the environment and are increasingly associated with nosocomial infections, often associated with multidrug-resistance phenotypes. This study aimed to evaluate epidemiological, physiological, and molecular characteristics of carbapenem resistance in P. aeruginosa and A. baumannii. In total, 63 nonreplicated strains (44 A. baumannii and 19 P. aeruginosa) were isolated from hospitalized patients. Antimicrobial resistance patterns, biocide tolerance, oxidative stress, hemolytic activity, and biofilm formation were assessed. Genetic markers related to β-lactamase synthesis, efflux systems, and porin loss were screened by PCR. Epidemiological data of patients were analyzed. Advanced age, intensive care unit admission, invasive medical devices, treatment with fluoroquinolones or β-lactams/β-lactamase inhibitor combinations, and prolonged hospital stay were predisposing factors for infection. Colistin showed to be active in vitro against these bacteria. Carbapenem-resistant P. aeruginosa strains did not show hemolytic activity and were less tolerant to oxidative stress and biocides. However, increased ability of biofilm formation was observed, comparing to the carbapenem-susceptible isolates. Genetic markers related to oxacillinases synthesis (OXA-23 and OXA-143), oprD absence, and efflux pump (adeB) were detected in carbapenem-resistant A. baumannii. Screening for OXA-51-like gene was performed as confirmatory test for A. baumannii identification. In P. aeruginosa genes encoding efflux pumps (MexAB-OprM, MexCD-OprJ, MexEF-OprN, and MexXY-OprM) and SPM-1 were found; besides, oprD absence was also observed. Our results suggest that these organisms are well adapted to different environments and confirm the difficulty of therapeutic management of patients with infections associated with multidrug-resistant microorganisms, with direct impact on mortality and epidemiological control of these strains in health centers.

Produced water exposure alters bacterial response to biocides.

Microbial activity during the holding and reuse of wastewater from hydraulic fracturing operations, termed produced water, may lead to issues with corrosion, sulfide release, and fouling. Biocides are applied to control biological activity, often with limited efficacy, which is typically attributed to chemical interactions with the produced water. However, it is unknown whether there is a biologically driven mechanism to biocide tolerance in produced water. Here, we demonstrate that produced water exposure results in an enhanced tolerance against the typically used biocide glutaraldehyde and increased susceptibility to the oxidative biocide hypochlorite in a native and a model bacteria and that this altered resistance is due to the salinity of the produced water. In addition, we elucidate the genetic response of the model organism Pseudomonas fluorescens to produced water exposure to provide a mechanistic interpretation of the altered biocide resistance. The RNA-seq data demonstrated the induction of genes involved in osmotic stress, energy production and conversion, membrane integrity, and protein transport following produced water exposure, which facilitates bacterial survival and alters biocide tolerance. Efforts to fundamentally understand biocide resistance mechanisms, which enable the optimization of biocide application, hold significant implications for greening of the fracturing process through encouraging produced water recycling. Specifically, these results suggest the necessity of optimizing biocide application at the level of individual shale plays, rather than historical experience, based upon produced water characteristics and salinity.

Modulated expression and enzymatic activity of the monogonont rotifer Brachionus koreanus Cu/Zn- and Mn-superoxide dismutase (SOD) in response to environmental biocides

Superoxide dismutases (SODs) are important antioxidant enzymes whose expression levels are often used as biomarkers for oxidative stress. To investigate the biomarker potential of the monogonont rotifer Brachionus koreanus SOD genes, the full-length Cu/Zn-SOD (Bk-Cu/Zn-SOD) and Mn-SOD (Bk-Mn-SOD) genes were cloned from genomic DNA and characterized. All amino acid residues involved in the formation of tertiary structure and metal binding in Bk-Cu/Zn-SOD and Bk-Mn-SOD were highly conserved across species. Phylogenetic analysis revealed that Bk-Mn-SOD, in particular, was closely clustered with mitochondrial Mn-SOD. Transcript analysis after exposure to six different biocides (alachlor, chlorpyrifos, dimethoate, endosulfan, lindane, and molinate) revealed that the transcriptional level of Bk-Cu/Zn-SOD was significantly increased in a dose-dependent manner. In contrast, the level of Bk-Mn-SOD transcript was significantly increased compared with control cells in response to chlorpyrifos, endosulfan, and molinate at their no observed effect concentrations (NOECs). However, exposure to alachlor, chlorpyrifos, and molinate significantly reduced the enzymatic activity of total SOD protein, while a decreased pattern was observed in all biocide treatments. Taken together, these results indicate that exposure to waterborne environmental biocides induces the transcription of Bk-Cu/Zn-SOD and Bk-Mn-SOD, but inhibits the enzymatic activity of Bk-SODs. These results contribute to our understanding of the modes of action of oxidative stress-mediating biocides on rotifer.

Defining gene-phenotype relationships in Acinetobacter baumannii through one-step chromosomal gene inactivation.

ABSTRACTRates of infection with hospital-acquired Acinetobacter baumannii have exploded over the past decade due to our inability to limit persistence and effectively treat disease. A. baumannii quickly acquires antibiotic resistance, and its genome encodes mechanisms to tolerate biocides and desiccation, which enhance its persistence in hospital settings. With depleted antibiotic options, new methods to treat A. baumannii infections are desperately needed. A comprehensive understanding detailing A. baumannii cellular factors that contribute to its resiliency at genetic and mechanistic levels is vital to the development of new treatment options. Tools to rapidly dissect the A. baumannii genome will facilitate this goal by quickly advancing our understanding of A. baumannii gene-phenotype relationships. We describe here a recombination-mediated genetic engineering (recombineering) system for targeted genome editing of A. baumannii. We have demonstrated that this system can perform directed mutagenesis on wide-ranging genes and operons and is functional in various strains of A. baumannii, indicating its broad application. We utilized this system to investigate key gene-phenotype relationships in A. baumannii biology important to infection and persistence in hospitals, including oxidative stress protection, biocide resistance mechanisms, and biofilm formation. In addition, we have demonstrated that both the formation and movement of type IV pili play an important role in A. baumannii biofilm.

Effects of polarization in the presence and absence of biocides on biofilms in a simulated paper machine water

The antifouling potential of electric polarization combined and not combined with biocides was studied in nonsaline warm water with high organic content. Deinococcus geothermalis is a bacterium known for forming colored biofilms in paper machines and for its persistence against cleaning and chemical treatments. When D. geothermalis biofilms grown for 24 h in simulated paper machine water were exposed to cathodic or cathodically weighted pulsed polarization at least 60% (P < 0.05) of the biofilms were removed from stainless steel (AISI 316L). Biofilm removal by 25 ppm (effective substances 5-25 ppm) of oxidizing biocides (bromochloro-5,5-dimethylhydantoin, 2,2-dibromo-2-cyanoacetamide, peracetic acid) increased to 70% when combined with cathodically weighted pulsed polarization. Using a novel instrument that allows real-time detection of reactive oxygen species (ROS) we showed that the polarization program effective in antifouling generated ROS in a pulsed manner on the steel surface. We thus suggest that the observed added value of oxidative biocides combined with polarization depended on ROS. This suggestion was supported by the finding that a reductive biocide, methylene bisthiocyanate, counteracted the antifouling effect of polarization.

Electrochemically generated biocides for controlling contamination in papermaking

Feasibility of electrochemically generated biocides in papermaking was evaluated in pilot scale trials. The trials indicated that electrochemically generated biocides prevent microbial growth and proliferation in broke systems, as well as in water circulations. The spoilage of broke can be delayed, and already spoiled broke can be recovered using these biocides. The improved broke quality increases the stability of the paper machine and, consequently, less broke is produced. The biocides can be added to water or pulp, and they have hardly any negative effect on the process or the end product. The presence of reducing compounds may cause limitations in the use of these oxidative biocides. It was observed that electrochemically generated biocide was also efficient against heat-resistant spores. However, the biocide was less efficient against spores as compared to vegetative cells, both aerobic and anaerobic, especially when the spore numbers were higher than 104 cfu/ml. Onsite oxidant production eliminates the transportation and storage of biocides. Moreover, due to the short time between the production and use, the degradation of the active compounds can be minimized.

Mode of action of hydrogen peroxide and other oxidizing agents: differences between liquid and gas forms

Antimicrobials such as chlorine dioxide, peracetic acid and hydrogen peroxide (H(2)O(2)) share a basic mechanism of action (chemical oxidation of cellular components), but profound differences arise in their efficacy against microorganisms. Optimization of activity requires an understanding of their interaction with microbial targets and a clear differentiation between the chemical efficacies of each oxidative biocide. This study aimed to elucidate the biochemical mechanisms of action of oxidizing biocides at a macromolecular level, using amino acids, protein and an enzyme as model substrates for the action of each biocide. The interactions of a number of oxidising agents (liquid and gaseous H(2)O(2), ClO(2), peracetic acid formulations) with amino acids, proteins (bovine serum albumin and aldolase) and enzymes were investigated by spectrophotometry, SDS-PAGE and alkaline phosphatase activity measurements. Biocide reactions yielded different types of oxidative structural change and different degrees of oxidation to amino acids and proteins, and differences in activity against a microbial enzyme. In particular there was a marked difference in the interactions of liquid H(2)O(2) and gaseous H(2)O(2) with the macromolecules, the latter causing greater oxidation; these results explain the dramatic differences in antimicrobial efficacy between liquid and gas peroxide. These results provide a comprehensive understanding of the differences in interactions between a number of oxidizing agents and macromolecules commonly found in microbial cells. Biochemical mechanistic differences between these oxidative biocides do exist and lead to differential effects on macromolecules. This in turn could provide an explanation as to their differences in biocidal activity, particularly between liquid and gas peroxide.

Optimization of biocide strategies on fine paper machines

In this study a rapid at-line ATP (adenosine triphosphate) analysis is applied in papermaking. This ATP analysis takes less than a minute, and the information can be utilized instantly to adapt the biocide program. The study shows the effect of different biocide strategies at paper mills. Comparison is made between oxidative and reductive biocides on the one hand, and on the other hand between continuous vs. batch additions of biocide. Continuous biocide addition keeps the microbial activity at a constant level. However, a long production period without a boil-out might result in accumulation of resistant bacteria, which cannot be eliminated without changing the biocide strategy. Batch addition of biocide creates a high temporary concentration of biocide in the process. This causes lower temporary microbial activity in the process, but between the doses the microbial activity may rise to an intolerable level. Batch addition causes chemical variation to the wet end of a paper machine more easily than continuous addition. This can affect the performance of papermaking chemicals and cause problems with retention, fixing, etc. Both biocide addition strategies can be used if they are monitored and optimized properly. Rapid ATP analysis is a suitable tool for both purposes.

Degradation of Phosphonate‐Based Scale Inhibitor Additives in the Presence of Oxidizing Biocides: “Collateral Damages” in Industrial Water Systems

Organic, phosphorus‐based additives are commonly used in water treatment technologies such as mineral scale and corrosion inhibitors, and dispersing agents. Phosphonates find extensive use as anti‐precipitation inhibitors for sparingly soluble salts such as calcium carbonates and phosphates, calcium/barium/strontium sulfates and others, commonly formed in supersaturated process waters in a wide spectrum of industrial applications. In open recirculating cooling water systems strong oxidizing biocides (eg. ClO−, BrO−, etc.) are also added to control microbiological growth but have detrimental effects on other water treatment chemicals that are sensitive to oxidative degradation. In this paper we report the effect of a hypobromite‐based biocide towards the scale inhibitor AMP (amino‐tris‐(methylene phosphonate)). AMP reacts rapidly with the biocide at room temperature. AMP degradation continues, but it slowly reaches a plateau after 1000 minutes. Even after 50 h the reaction time, only 20% of AMP has decomposed. AMP reacts with the biocide to give the orthophosphate much more rapidly at 43°C than at 25°C due to faster kinetics of decomposition. Results on various other oxidizing biocides on PBTC (2‐Phosphonobutane‐1,2,4‐Tricarboxylic acid) are also presented. PBTC is a very “robust” scale inhibitor. This is confirmed by our degradation studies using biocides such as chlorine (ClO−), bromine (BrO−), their stabilized analogs, BCDMH, and ClO2. Degradation (reversion to orthophosphate) of only up to 5% is observed in our experiments. These results are compared to others reported in the literature showing that PBTC degradation can be up to 25% under “harsher” conditions of higher biocide dosage and temperature. PBTC is virtually stable to the effects of a variety of oxidizing microbiocides, including chlorine, bromine and others.

Chemistry of Organophosphonate Scale Inhibitors, Part 4: Stability of Amino-tris-(Methylene Phosphonate) Towards Degradation by Oxidizing Biocides

Organic additives are broadly used in water-treatment applications such as mineral scale, corrosion inhibitors, and dispersing agents. Phosphonates find extensive use as inhibitors for the formation of sparingly soluble salts such as calcium carbonates, phosphates, calcium sulfates, and others, commonly formed in open recirculating cooling systems. In such systems, biocides also are added to control microbiological growth. Some of these biocides are strong oxidants (e.g., ClO−, BrO−, etc.) and affect other water treatment chemicals that are sensitive to oxidative degradation. This study reports the effect of a hypobromite-based biocide towards the triphosphonate amino-tris-(methylene phosphonate) (AMP). AMP reacts rapidly with the biocide at room temperature. AMP degradation continues, but it slowly reaches a plateau after 1000 min. Even after 50 h of reaction time, only 20% of the AMP has decomposed. AMP reacts with the biocide to give orthophosphate much more rapidly at 43°C than at 25°C due to faster kinetics of decomposition.