Effective Biocide Research Articles

Controlling the Invasive Diatom Didymosphenia geminata: An Ecotoxicity Assessment of Four Potential Biocides

In 2004, an invasive mat-forming freshwater diatom, Didymosphenia geminata (didymo), was found in New Zealand causing concern with regard to potential consequences for local freshwater ecosystems. A four-stage research program was initiated to identify methods to control D. geminata. This article reports the results of Stage 2, in which four potential control compounds [Gemex™ (a chelated copper formulation), EDTA, Hydrothol®191, and Organic Interceptor™ (a pine oil formulation)] selected in Stage 1 were evaluated for their biocidal efficacy on D. geminata and effects on non-target organisms using both artificial stream and laboratory trials. Artificial stream trials evaluated the mortality rates of D. geminata and fishes to three concentrations of the four biocides, whereas laboratory toxicity trials tested the response of green alga and cladocera to a range of biocide concentrations and exposure times. In artificial stream trials, Gemex and Organic Interceptor were the most effective biocides against D. geminata for a number of measured indices; however, exposure of fishes to Organic Interceptor resulted in high mortality rates. Laboratory toxicity testing indicated that Gemex might negatively affect sensitive stream invertebrates, based on the cladoceran sensitivity at the proposed river control dose. A decision support matrix evaluated the four biocides based on nine criteria stipulated by river stakeholders (effectiveness, non-target species impacts, stalk removal, degradation profile, risks to health and safety, ease of application, neutralization potential, cost, and local regulatory requirements) and Gemex was identified as the product warranting further refinement prior to an in-river trial.

A direct comparison between extracted tooth and filter-membrane biofilm models of endodontic irrigation using Enterococcus faecalis

Endodontic restorations often fail due to inadequate disinfection of the root canal even though the antimicrobial irrigants used have been shown to be capable of killing the bacterium frequently implicated in this complication, Enterococcus faecalis (Ef). Extracted human teeth were root-prepared and filled with a liquid culture of Ef. Following incubation, the root canals were irrigated with 1% sodium hypochlorite (NaOCl), electrochemically activated water or saline control. Irrigation was modelled using an electronic pipette to deliver the solutions at a reproducible flow velocity. A series of parallel experiments employed a membrane biofilm model that was directly immersed into irrigant. Experimental conditions where contiguous between the extracted tooth model and biofilm model wherever possible. After 60 s of exposure, 1% NaOCl effectively sterilised the biofilm model, whereas log 3.36 viable Ef where recoverable from the analogous extracted tooth model, the other irrigants proved ineffective. Biofilms of Ef were susceptible to concentrations of irrigant that proved ineffective in the tooth model. NaOCl was the most effective biocide in either case. This suggests that the biofilm modality of bacterial growth may not be the most important factor for the recalcitrance of root canal infections during endodontic irrigation; it is more likely due to the inability of the irrigant to access the infection.

Fatty Acid–Based Formulations for Wood Protection against Mold and Sapstain

Safer, highly effective biocides providing long-term protection of mold growth on wood-based materials is of interest to the wood protection industry. Moldicide formulations containing synergistic combinations of ingredients derived from natural sources are commonly recognized as a promising approach for the next generation of wood protectants. Although fatty acid (FA)–based chemistry has had some development in food sanitation and agriculture, little exploration relating to new mold inhibitors for wood and wood products has occurred. Low molecular weight, saturated monocarboxylic acids combined with selected adjuvants can effectively inhibit mold spore germination. Specifically, formulations containing valeric or pentanoic (C5), hexanoic or caproic (C6), heptanoic (C7), caprylic or octanoic (C8), pelargonic or nonanoic (C9), and/or decanoic or capric (C10) saturated acid demonstrated efficacy against mold growth for up to 12 weeks in the ASTM D4445 standard laboratory test for mold. Pressure-treated wood was more resistant to mold growth than wood dip treated with FA formulations.

Control of Sulfate-Reducing Bacteria in Oil and Gas Pipelines

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 118410, "Control of Sulfate-Reducing Bacteria in Oil and Gas Pipelines," by M.D. Lohithesh and A.K. Agnihotri, ONGC, and Banwari Lal, SPE, TERI, prepared for the 2008 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, UAE, 3-6 November. The paper has not been peer reviewed. A major economic loss faced by oil and gas companies is pipeline corrosion. Internal pipeline corrosion is, basically, caused by sulfate-reducing bacteria (SRB). The growth of SRB and their secondary metabolites in pipelines causes surface modifications, which can induce a more-complex corrosion process. A strategy was studied for controlling the SRB population of oil and gas pipelines. Introduction Microbial-induced corrosion (MIC) has been implicated widely in the deterioration of metal pipelines and offshore structures in the oil industry. Though several studies have reported the use of chemicals as biocides for controlling MIC, these conventional methods generally are inadequate against bacterial biofilms. Metabolically active bacteria exhibit an increased tendency to attach to metal surfaces and, depending on the availability of nutrients, to produce exopolymers to form mature biofilms. The exopolysaccharide matrix that helps form the biofilm may be involved in reducing the reactivity of chemical biocides. Attempts to circumvent this problem have focused on use of very high concentrations of chemical biocides, which may in turn pose environmental hazards. Further, after a long period of contact, corrosion-causing bacterial microflora might adapt to a given biocide and develop resistance. It is established that even if biocides are effective against planktonic population (i.e., dispersed in the water phase), their effectiveness against sessile forms (i.e., embedded within biofilm) is reduced by approximately 90%. Therefore, development continues for effective biocides, appropriate procedure for their application, and innovative measures for microbial control. This study explored the effect of biocides on the inhibition of SRB in oil pipelines. The objectives were to screen efficient and effective biocides for inhibition of MIC in oil pipelines, examine the potential of effective biocides by measuring the total sulfide production, and demonstrate the ability of biocides against biofilm (sessile population). Materials and Methods Oil and water samples were collected from the pipeline network of Oil and Natural Gas Corporation (ONGC), India, at the Bombay high offshore, Gandhar, and Ahmedabad areas. Production fluid was collected directly from the production wellheads. The SRB consortium was developed from formation water collected from corroded oil pipelines The SRB medium was prepared by adding 25 g of NaHCO3, 0.2 g of CaCl2•2H2O, 0.1 g of KCl, 1.5 g of NH4Cl, 0.6 g of NaH2PO4•H2O, 10.0 mL of vita-min, and 10 mL of trace element with a molarity of 50 mM (millimolar =mol/m3) ferric citrate in 1 L of double-distilled water. The pH of the medium was adjusted to 7.5±0.1 by use of 1 M NaOH. The SRB consortium was purified by the roll-tube method, and individual strains were identified by use of 16S rDNA analysis.

Effect of adding ozone into an intensive broiler production unit on performance, mortality, ammonia levels, and bacterial levels as compared with a non-ozone-treated broiler unit

SUMMARY Ozone is a very unstable and reactive molecule that can rapidly oxidize many organic substances and is often used for odor control. It is also known to be an effective biocide at high dose levels. Despite the lack of scientific evidence linking ozone to reduced aerial ammonia at levels that are safe for birds and humans, there is still an interest in the use of the product for commercial production poultry units. The objective of this experiment was to determine the effect of adding atmospheric ozone at a target level of 0.05 ppm (level achieved, 0.03 ± 0.017 ppm) to rooms housing broiler chickens. Female broiler chickens were grown in either an untreated environment or an environment with added ozone (3 rooms of 5 replicate pens, each containing 110 birds/treatment). Bird weight and feed consumption were recorded on a pen basis at 21 and 40 d of age; mortalities were collected daily, and necropsies were performed. Air samples were collected and plated on appropriate media to count total aerobic bacteria at 11, 19, and 34 d of age and enterobacteria at 34 d. Atmospheric ammonia levels were measured on d 15, 20, 28, 32, and 38. A significant (P ≤ 0.05) improvement in feed conversion (feed:gain ratio) when corrected for mortality was noted in the ozone-treated birds (1.808 vs. 1.870). Birds exposed to ozone grew significantly slower (1.938 vs. 2.053 kg of BW gain), consumed less feed (3.695 vs. 3.953 kg), and had a higher mortality (11.46 vs. 7.33%) and condemnation percentages (10.36 vs. 3.39%) than nontreated broilers. The addition of ozone caused no significant decrease in ammonia level or total bacterial count. The major increases in morbidity and mortality of the birds subjected to ozone make ozone gas unacceptable for use in a commercial broiler unit and raise serious health issues for both producers and birds.

ASSESSMENT OF PHENOL DERIVATIVES IN COOLING TOWER SYSTEM AS BIOCIDES

One of the major problems facing the industrial utilities especially cooling towers is biofouling. Many techniques and measures have been taken and still continuing researches are under way. Biocides and water qualities were the main area of research for evaluation. Friendly biocides are preferable for controlling viable count and fungi, but many harmful still in use.The main objective of this research work is to predict a relationship covering the concentration of Cl and Br – containing compounds as biocide and the performance.It was concluded that the chlorophenol is the major effective biocide used (reduce it for about 80%, while bromophenol to about 65%) and that material although they are highly approved, but suffer pitting corrosion.

Bactericidal effect of silver nanoparticles against multidrug-resistant bacteria

Infections caused by drug-resistant microorganisms result in significant increases in mortality, morbidity, and cost related to prolonged treatments. The antibacterial activity of silver nanoparticles against some drug-resistant bacteria has been established, but further investigation is needed to determine whether these particles could be an option for the treatment and prevention of drug-resistant microbial infections. Hence, we challenged different drug-resistant pathogens of clinical importance (multidrug-resistant Pseudomonas aeruginosa, ampicillin-resistant Escherichia coli O157:H7 and erythromycin-resistant Streptococcus pyogenes) with a suspension of silver nanoparticles. By means of a luciferase-based assay, it was determined that silver nanoparticles (1) inactivate a panel of drug-resistant and drug-susceptible bacteria (Gram positive and Gram negative), (2) exert their antibacterial activity through a bactericidal rather than bacteriostatic mechanism, and (3) inhibit the bacterial growth rate from the time of first contact between the bacteria and the nanoparticles. Additionally, strains with a resistant phenotype to silver nanoparticle were developed and used to explore the bactericidal mode of action of silver nanoparticles. Through a Kirby–Bauer test, it was shown that silver nanoparticles’ general mechanism of bactericidal action is based on inhibition of cell wall synthesis, protein synthesis mediated by the 30s ribosomal subunit, and nucleic acid synthesis. Our data suggest that silver nanoparticles are effective broad-spectrum biocides against a variety of drug-resistant bacteria, which makes them a potential candidate for use in pharmaceutical products and medical devices that may help to prevent the transmission of drug-resistant pathogens in different clinical environments.

Secondary and Tertiary Polydiallylammonium Salts: Novel Polymers with High Antimicrobial Activity

Antimicrobial activity of secondary and tertiary poly(diallylammonium) salts (PDAAs) had not been reported before. Due to difficulties with preparation of polymers from the monomers of the diallylamine (DAA) series in the nonquaternary form, up to recently it was not possible to obtain PDAAs with a sufficiently high molecular mass. Here, we describe the investigations of antimicrobial activity of novel water-soluble cationic polyelectrolytes of the PDAA series, namely secondary poly(diallylammonium trifluoroacetate) (PDAATFA) and tertiary poly(diallylmethylammonium trifluoroacetate) (PDAMATFA), in synthesis of which we have recently succeeded, against gram-positive and gram-negative bacteria, and fungi. We have studied the effect of molecular weight (polymeric chain length) and ionic strength of solution on the biocidal efficiency of those polymers; in addition, the concentration dependences of PDAATFA reduced viscosity in salt-free and KCl aqueous solutions have been investigated. The antimicrobial properties of polybase polydiallylamine (BPDAA), which was obtained in an aqueous solution of PDAATFA in presence of alkali, have been also studied as well as biocidal activity of commercial open-chain polybase branched PEI. Those PDAATFA, BPDAA and PEI polymers served as the systems to study the structure-activity relationships. Transmission electronic microscopy study was carried out to characterize the mode of antimicrobial action of PDAATFA using E. coli . It was shown that the synthesized PDAATFA and PDAMATFA exhibit, unlike the quaternary polymers of this series, a rather high biocidal efficiency that is comparable with the activity of known effective cationic polymer biocides or exceeds it. Novel polyelectrolytes exhibit quite strong biocidal properties at different conditions including aqueous solutions of moderate ionic strength (serum, 0.01 M/0.1 M) and aqueous-alkaline solutions (pH 10.5) until the macrochain retains some positive charge, but complete neutralization of the polyelectrolyte in a 1 M salt solution results in the loss of its biocidal activity. The obtained results evidence that the structure of links, which combine the hydrophobic pyrrolidinium rings with the hydrophilic secondary/tertiary ammonium groups, is responsible for the high biocidal activity of the PDAAs. Polymeric nature of the synthesized compounds is one of the most significant factors of their bactericidal efficiency, unlike their high fungicidal activity, which is evidently related to the secondary/tertiary pyrrolidinium cycle.

Thermal, chemical, and photocatalytic inactivation of Lactobacillus plantarum bacteriophages.

The effect of several biocides, thermal treatments, and photocatalysis on the viability of four Lactobacillus plantarum phages was investigated. Times to achieve 99% inactivation (T99) of phages at 63, 72, and 90 degrees C were evaluated in four suspension media: deMan Rogosa Sharpe broth, reconstituted skim milk, a commercial EM-glucose medium, and Tris magnesium gelatin buffer. The four phages studied were highly resistant to 63 degrees C (T99 > 45 min); however, counts < 10 PFU/ml were achieved by heating at 90 degrees C for 5 min. Higher thermal resistance at 72 degrees C was observed when reconstituted skim milk and EM-glucose medium were assayed. Peracetic acid (0.15%, vol/vol) was an effective biocide for the complete inactivation of all phages studied within 5 min of exposure. Sodium hypochlorite (800 ppm) inactivated the phages completely within 30 min. Ethanol (100%) did not destroy phage particles even after 45 min. Isopropanol did not have any effect on phage viability. Phage counts < 50 PFU/ml were obtained within 180 min of photocatalytic treatment. The results obtained in this work are important for establishing adequate methods for inactivating phages in industrial plants and laboratory environments.

Novel antiviral activity of dialdehyde starch

A significant effort worldwide is being directed toward development of novel biocides against drug-resistant bacterial and viruses because of the significant potential human infection risks in the general population. We report here the discovery of a strong antiviral biocide, dialdheyde starch (DAS). Antiviral tests were carried out against three non-envelop viruses, including two bacterial viruses MS2 and PRD1, and one human virus Poliovirus. Dialdehyde starch aqueous suspensions were effective biocides against these three test viruses in a 1 hr exposure test. The antiviral activity was significantly enhanced in a four-hour exposure test, with maximum seven orders of magnitude reductions against MS2 and PRD1, and four-order reduction against Poliovirus. The antiviral activity of dialdehyde starch was found to be pH dependent, being more active in alkaline and acidic conditions than in neutral conditions. Dialdehyde starch (DAS) is a polymeric dialdehyde prepared from selective oxidation of starch by periodate ions which cleaves the C2-C3 bond of the anhydroglucose units of the starch polysaccharide chain to form the

Enhancing the sporulation of Streptomyces kasugaensis by culture optimization

To be an effective microbial biocide, Streptomyces kasugaensis should be converted into spore during cultivation process for successful long-term storage. By statistical design methods, culture conditions including medium components and operating parameters were optimized and more than 100 times increase in spore yield was achieved. Addition of spent culture fluid (100 ppm), EDTA (30 ppm), mycophenolic acid (32 ppm) with combination of pH up-shock (5.5 to 8.5) increased total viable cell and spore conversion rate, resulting in 1.6×107 (spore/mL) in 5 days of culture in a fermenter. This result provides a practical method for obtaining high spore number for commercial production of Streptomyces kasugaensis as a microbial pesticide.

Studies on the Disinfection and Removal of Biofilms by Ozone Water Using an Artificial Microbial Biofilm System

Inactivation rates of the biofilms of P. fluorescence and P. aeruginosa established on a small slide glass in ozone water (0.9–3.2 mg/L, 1–20 min) were determined in a batch or flow-through system. The effects of ozone water on the biofilm matrices were defined clearly in situ by confocal laser scanning microscopy. These results indicate that ozone is an effective biocide against biofilms and it can remove exopolysaccharides in the biofilm matrices. However, the effective concentration of ozone for disinfection of biofilms varied with the biofilms formed, mainly due to reactions of ozone with constituents of the biofilms.

Microwave-Assisted Synthesis of a New Hydantoin Monomer for Antibacterial Polymeric Materials

11-(4,4-Dimethyl-2,5-dioxoimidazolidin-1-yl)undecyl acrylate was synthesized in a two-step procedure using microwave irradiation. Poly(acrylates) containing fluorinated and hydantoin (5,5-dimethylimidazolidine-2,4-dione) moieties were prepared by free radical polymerization of 2-(perfluorooctyl)ethyl acrylate and the synthesized monomer with the aim of obtaining low surface energy polymeric materials with properties of contact-active biocides. Polymeric films were treated with a bleaching solution in order to convert the hydantoin units to N-halamines, well-known contact-active biocides. The reversibility of the chlorination reaction, necessary to impart a renewable biocide effect, was investigated by Fourier Transform-Attenuated Total Reflection. Preliminary biological tests conducted against Bacillus megaterium demonstrated the effective biocide properties of the prepared materials.

Long-term effects of the antifouling booster biocide Irgarol 1051 on periphyton, plankton and ecosystem function in freshwater pond mesocosms

Irgarol is a highly effective biocide used in antifouling coatings to prevent the growth of periphyton. Environmental concentrations of Irgarol in marine and freshwater have often exceeded the effect concentrations of autotrophic organisms tested in the laboratory and give reason for concern that natural periphyton communities may be endangered. A 150 days freshwater mesocosm study in 8 indoor ponds was conducted at nominal concentrations between 0.04 and 5 μg L −1 in order to investigate the effects of Irgarol on periphyton and plankton. The results demonstrated that periphyton communities were strongly affected after single applications of 1 and 5 μg L −1 Irgarol. For these concentrations no recovery was observed in the course of the study. For chlorophytes, the EC 50 (nominal, 135 days) was 0.34 μg L −1. Phytoplankton also decreased in abundance directly after Irgarol application but recovered after a few weeks, as Irgarol concentrations rapidly decreased in the water body and nutrient levels increased due to lack of competition with periphyton and macrophytes. Zooplankton was indirectly affected by Irgarol. Principle response curve analysis revealed a species shift from macrophyte associated zooplankton species to free-swimming species. For species of cyclopoid copepods and ostracods the EC 50 was, respectively, 0.09 and 0.11 μg L −1. The study simulated a best-case scenario since the mesocosms were dosed only once. Under field conditions, however, permanent exposure of organisms to Irgarol is more likely due to permanent leaching from painted ship hulls. Therefore, the effects presented in this study most likely underestimate the effects under natural conditions.

Onboard ship evaluation of the effectiveness and the potential environmental effects of PERACLEAN® Ocean for ballast water treatment in very cold conditions

This study verified the effectiveness and the potential toxic impact of PERACLEAN Ocean ballast water treatment for very cold freshwater (0.1-0.5 degrees C) in real ballast tank (750 m(3)) conditions aboard a ship and in large-volume (4.5 m(3)) polyethylene tanks. Concentrations of peracetic acid (PAA) and hydrogen peroxide (H2O2) gradually dropped by 41-59% over 5 days. The treatment altered the quality of the treated waters by causing a pH drop of 0.9-1.3 units and a fourfold to sevenfold increase in dissolved organic carbon and organophosphates concentrations. More than 90% of the biomass of free-floating micro-organisms and viable phytoplankton were eliminated within 48 h after treatment. The treatment resulted in 100% mortality in caged fish exposed to treated waters but was totally ineffective against adult zebra mussels and some nematods living in tank sediments. Toxic response from ecotoxicological assays indicated that treated waters after 5 days should be diluted by a factor of 1:2 to 1:200 to reduce toxicity below selected endpoints of acute lethality tests. On the basis of PAA degradation rate, fresh waters treated with 100-ppm PERACLEAN Ocean should be kept in ballast tanks for 15-20 days after treatment to reduce toxicity. It is concluded that the treatment can be an effective biocide to rapidly eliminate organisms of the water column inside the ballast tanks over a wide range of environmental conditions, but that the discharge of the toxic treated waters should be properly managed to minimize potential environmental impact.

Evaluation of effective biocides for SRB to control microbiologically influenced corrosion

AbstractThe effects on microbiologically induced corrosion (MIC) of mild steel resulting from the presence of corrosion products in the biofilm of sulphate‐reducing bacteria (SRB) have been investigated. The culture‐media‐containing sulphide of biogenic origin was used to find out the effect of metal‐sulphide layers developed. The SRB were isolated from the Ennore brackish water (Chennai, India). Biocides with different concentrations were used to inhibit the metabolic activity of bacteria. Open circuit potentials (OCP) followed by potentiostatic polarisation measurements were carried out for the specimens with and without the biofilm. Electrochemical impedance spectrometry (EIS) and scanning electron microscopy (SEM) were used to study the accumulation of the biofilms. The corrosion rates and the mechanism of corrosion processes were understood from the investigation.

Effect of Biocides on Biofilm Bacteria from Dental Unit Water Lines

Microbial biofilm formation in dental unit water lines (DUWL) is a phenomenon that has been recognized for nearly four decades. Water delivered by DUWL can harbor high numbers of bacteria, including opportunistic pathogens. Biofilms on tubing within DUWL may serve as a reservoir for these microorganisms and should therefore be controlled. In this study, the effects of eight biocides were monitored on DUWL biofilms individually and in combination by epifluorescence microscopy and total viable counts (TVC). The effects of sodium dodecyl sulphate (SDS), hydrogen peroxide (H2O2), sodium hypochlorite (NaOCl), phenol (Phe), Tween 20 (Tw 20), ethylenediaminetetraacetic acid (EDTA), chlorohexidine gluconate (CHX), and povidine iodine (PI) were tested on DUWL biofilms alone and in combination. PI was found to have negligible effects on biofilm removal either applied alone or in combined form with CHX. Applying all biocides simultaneously did not completely eliminate viable bacteria nor did they remove biofilm. Overall, when combined, the biocides performed better than singly applied products. The most effective biocides were NaOCl and Phe (both alone and in combination).

Biologically Active Tin Compounds Based on Aziridine and Azepane Derivatives

Abstract Four of new tin(IV) compounds derived from aziridine and azepane substituents have been synthesized and characterization by elemental microanalysis, atomic absorption, FT-IR and 1H-NMR spectroscopy. These tin-derived compounds exhibited biocidal activities on four different microorganisms: Escherichia coli, Staphylococcus aureus, Candida albicans and Aspergillus niger. The use of common and effective biocides depends on the surfactant molecules. On this basis, surface tension measurements were used to determine the critical micellar concentration (cmc), the minimum average area per surfactant molecule (Amin) and the surface excess concentration (Γ∞). A direct relationship has found between the antimicrobial efficacy and Γ∞.

Failure investigation of stainless steel piping in a sulphur recovery unit of a gas‐processing plant

PurposeThis paper seeks to determine the causes and mechanism of failure of stainless steel piping in a sulphur recovery unit of a gas‐processing plant and to recommend suitable measures to avoid recurrences.Design/methodology/approachThe integrity of the material of construction was verified using various laboratory and analytical techniques. Standard metallographic techniques were used to prepare representative samples obtained from failed stainless steel piping for metallurgical evaluation. Microstructural characterization was carried out in an inverted metallurgical microscope equipped with an imaging facility. Elemental analysis and hardness were used to confirm the identification of the material. Corrosion product/deposits were analyzed using wet chemistry supported by X‐ray diffraction analysis. Microbes were enumerated through standard methods.FindingsThe piping failed due to severe pitting corrosion, which resulted in the formation of holes. Microbial‐induced corrosion (MIC) and under‐deposit corrosion were chief contributing factors that caused the failure in stainless steel piping. In addition, the HAZ near welds at some places was found to be sensitized causing accelerated pitting corrosion at these sites.Practical implicationsThe expected service life of stainless steel piping could not be realized as the piping failed due to the combined effect of MIC and under‐deposit corrosion. Periodic monitoring of sulphate‐reducing bacteria and sulphur‐oxidizing bacteria coupled with implementation of an effective biocide treatment programme in process fluid was recommended, together with the introduction of a procedure for frequent cleaning of the pipe walls to minimize under‐deposit attack.Originality/valueThe paper – a technical case study of process industry – provides an account of failure investigation. It identifies the causes and mechanism of failure and suggests suitable preventive and corrective measures. This is useful industrial experience that provides valuable information for process and plant corrosion engineers involved in the operation of this type of equipment.

Effective biocide to prevent microbiological contamination during PEG impregnation of wet archaeological iron-wood artefacts

Abstract A new conservation process was developed for archaeological iron-wood artefacts. Metal part protection was achieved by adding a corrosion inhibitor (Hostacor IT ® ) in the polyethylene glycol (PEG) soaking solutions. Nevertheless, a significant microbiological growth was observed in the baths and around the objects. From the different soaking solutions, 23 bacterial strains and 12 strains of filamentous fungi were isolated. Adding compatible biocide has been absolutely essential to allow the PEG and Hostacor IT ® to be effective. Among biocides tested, Dowicide ® A that contains sodium o -phenylphenate is the most efficient. As shown by electrochemical measurements (corrosion potential, intensity and polarization resistance), this biocide does not destabilize the formation of protective film created by Hostacor IT ® . There is no competition of adsorption between Hostacor IT ® and Dowicide ® . In the presence of Dowicide ® , Hostacor IT ® acts more quickly and in a significant way. At the concentration of 3000 ppm, Dowicide ® is effective to protect the aqueous solutions of PEG 400+ Hostacor IT ® from the development of the selected microorganisms. Adding the biocide at the beginning of the object impregnation was the most effective way to prevent bacterial and fungal growth. Tests in real conditions showed that after two months of impregnation, solutions reminded clear and no biofilm was observed around artefacts.