Bacterial Growth Potential Research Articles

A uniform bacterial growth potential assay for different water types

The bacterial growth potential is important to understand and manage bacterial regrowth-related water quality concerns. Bacterial growth potential depends on growth promoting/limiting compounds, therefore, nutrient availability is the key factor governing bacterial growth potential. Selecting proper tools for bacterial growth measurement is essential for routine implementation of the growth potential measurement.This study proposes a growth potential assay that is universal and can be used for different water types and soil extract without restrictions of pure culture or cultivability of the bacterial strain. The proposed assay measures the sample bacterial growth potential by using the indigenous community as inocula. Flow cytometry (FCM) and adenosine tri-phosphate (ATP) were used to evaluate the growth potential of six different microbial communities indigenous to the sample being analyzed, with increasing carbon concentrations. Bottled mineral water, non-chlorinated tap water, seawater, river water, wastewater effluent and a soil organic carbon extract were analyzed.Results showed that indigenous bacterial communities followed normal batch growth kinetics when grown on naturally present organic carbon. Indigenous bacterial growth could detect spiked organic carbon concentrations as low as 10 μg/L. The indigenous community in all samples responded proportionally to the increase in acetate-carbon and proportional growth could be measured with both FCM and ATP. Bacterial growth was proportional to the carbon concentration but not the same proportion factor for the different water samples tested. The effect of inoculating the same water with different indigenous microbial communities on the growth potential was also examined. The FCM results showed that the highest increase in total bacterial cell concentration was obtained with bacteria indigenous to the water sample.The growth potential assay using indigenous bacterial community revealed consistent results of bacterial growth in all the different samples tested and therefore providing a fast, more stable, and accurate approach for monitoring the biological stability of waters compared to the previously developed assays. The growth potential assay can be used to aid in detecting growth limitations by compounds other than organic carbon.

Identifying the underlying causes of biological instability in a full-scale drinking water supply system

Changes in bacterial concentration and composition in drinking water during distribution are often attributed to biological (in)stability. Here we assessed temporal biological stability in a full-scale distribution network (DN) supplied with different types of source water: treated and chlorinated surface water and chlorinated groundwater produced at three water treatment plants (WTP). Monitoring was performed weekly during 12 months in two locations in the DN. Flow cytometric total and intact cell concentration (ICC) measurements showed considerable seasonal fluctuations, which were different for two locations. ICC varied between 0.1–3.75 × 105 cells mL−1 and 0.69–4.37 × 105 cells mL−1 at two locations respectively, with ICC increases attributed to temperature-dependent bacterial growth during distribution. Chlorinated water from the different WTP was further analysed with a modified growth potential method, identifying primary and secondary growth limiting compounds. It was observed that bacterial growth in the surface water sample after chlorination was primarily inhibited by phosphorus limitation and secondly by organic carbon limitation, while carbon was limiting in the chlorinated groundwater samples. However, the ratio of available nutrients changed during distribution, and together with disinfection residual decay, this resulted in higher bacterial growth potential detected in the DN than at the WTP. In this study, bacterial growth was found to be higher (i) at higher water temperatures, (ii) in samples with lower chlorine residuals and (iii) in samples with less nutrient (carbon, phosphorus, nitrogen, iron) limitation, while this was significantly different between the samples of different origin. Thus drinking water microbiological quality and biological stability could change during different seasons, and the extent of these changes depends on water temperature, the water source and treatment. Furthermore, differences in primary growth limiting nutrients in different water sources could contribute to biological instability in the network, where mixing occurs.

Polyamine is a critical determinant of Pseudomonas chlororaphis O6 for GacS‐dependent bacterial cell growth and biocontrol capacity

The Gac/Rsm network regulates, at the transcriptional level, many beneficial traits in biocontrol-active pseudomonads. In this study, we used Phenotype MicroArrays, followed by specific growth studies and mutational analysis, to understand how catabolism is regulated by this sensor kinase system in the biocontrol isolate Pseudomonas chlororaphis O6. The growth of a gacS mutant was decreased significantly relative to that of the wild-type on ornithine and arginine, and on the precursor of these amino acids, N-acetyl-l-glutamic acid. The gacS mutant also showed reduced production of polyamines. Expression of the genes encoding arginine decarboxylase (speA) and ornithine decarboxylases (speC) was controlled at the transcriptional level by the GacS sensor of P. chlororaphis O6. Polyamine production was reduced in the speC mutant, and was eliminated in the speAspeC mutant. The addition of exogenous polyamines to the speAspeC mutant restored the in vitro growth inhibition of two fungal pathogens, as well as the secretion of three biological control-related factors: pyrrolnitrin, protease and siderophore. These results extend our knowledge of the regulation by the Gac/Rsm network in a biocontrol pseudomonad to include polyamine synthesis. Collectively, our studies demonstrate that bacterial polyamines act as important regulators of bacterial cell growth and biocontrol potential.

Short-term organic carbon migration from polymeric materials in contact with chlorinated drinking water

Polymeric materials are widely used in drinking water distribution systems. These materials could release organic carbon that supports bacterial growth. To date, the available migration assays for polymeric materials have not included the potential influence of chlorination on organic carbon migration behavior. Hence, we established a migration and growth potential protocol specifically for analysis of carbon migration from materials in contact with chlorinated drinking water. Four different materials were tested, including ethylene propylene dienemethylene (EPDM), poly-ethylene (PEX b and PEX c) and poly-butylene (PB). Chlorine consumption rates decreased gradually over time for EPDM, PEXc and PB. In contrast, no free chlorine was detected for PEXb at any time during the 7 migration cycles. Total organic carbon (TOC) and assimilable organic carbon (AOC) was evaluated in both chlorinated and non-chlorinated migrations. TOC concentrations for EPDM and PEXb in chlorinated migrations were significantly higher than non-chlorinated migrations. The AOC results showed pronounced differences among tested materials. AOC concentrations from chlorinated migration waters of EPDM and PB were higher compared to non-chlorinated migrations, whereas the opposite trend was observed for PEXb and PEXc. There was also a considerable difference between tested materials with regards to bacterial growth potential. The results revealed that the materials exposed to chlorine-influenced migration still exhibited a strong biofilm formation potential. The overall results suggested that the choice in material would make a considerable difference in chlorine consumption and carbon migration behavior in drinking water distribution systems.

Direct measurement of ATP in seawater and application of ATP to monitor bacterial growth potential in SWRO pre-treatment systems

The use of adenosine triphosphate (ATP) to monitor bacterial growth potential of seawater is currently not possible as ATP cannot be accurately measured at low concentration in seawater using commercially available luciferase-based ATP detection. The limitation is due to interference of salt with the luciferin–luciferase reaction, which inhibits light production. This research demonstrates that new reagents developed for (i) ATP extraction from microbial cells and (ii) ATP detection in seawater are able to reliably detect Microbial ATP as low as 0.3 ng L–1 in seawater. The luminescence signal of the new detection reagent is significantly higher (>20 times) than the luminescence signal of the freshwater reagent, when applied in seawater. ATP can now be used to monitor bacterial growth potential (BGP) through pre-treatment trains of seawater reverse osmosis (SWRO) plants. The level of detection of the new BGP test is significantly lower than the estimated threshold value required to prevent biofouling in SWRO systems. The new reagents have been used to monitor Microbial ATP in coastal North Sea water. Moreover, Microbial ATP has been applied to monitor the bacterial growth potential (using indigenous bacteria) through the pre-treatment train of an SWRO desalination plant. A significant reduction (>55%) of the bacterial growth potential was found through the dual media filtration with 4.5 mg-Fe(III) L–1 coagulant. Overall, the new reagents can detect low Microbial ATP concentrations in seawater and can be used to monitor bacterial growth potential in seawater desalination plants.

A systematic approach for the assessment of bacterial growth-controlling factors linked to biological stability of drinking water in distribution systems

A systematic approach is presented for the assessment of (i) bacterial growth-controlling factors in drinking water and (ii) the impact of distribution conditions on the extent of bacterial growth in full-scale distribution systems. The approach combines (i) quantification of changes in autochthonous bacterial cell concentrations in full-scale distribution systems with (ii) laboratory-scale batch bacterial growth potential tests of drinking water samples under defined conditions. The growth potential tests were done by direct incubation of water samples, without modification of the original bacterial flora, and with flow cytometric quantification of bacterial growth. This method was shown to be reproducible (ca. 4% relative standard deviation) and sensitive (detection of bacterial growth down to 5 µg L−1 of added assimilable organic carbon). The principle of step-wise assessment of bacterial growth-controlling factors was demonstrated on bottled water, shown to be primarily carbon limited at 133 (±18) × 103 cells mL−1 and secondarily limited by inorganic nutrients at 5,500 (±1,700) × 103 cells mL−1. Analysis of the effluent of a Dutch full-scale drinking water treatment plant showed (1) bacterial growth inhibition as a result of end-point chlorination, (2) organic carbon limitation at 192 (±72) × 103 cells mL−1 and (3) inorganic nutrient limitation at 375 (±31) × 103 cells mL−1. Significantly lower net bacterial growth was measured in the corresponding full-scale distribution system (176 (±25) × 103 cells mL−1) than in the laboratory-scale growth potential test of the same water (294 (±35) × 103 cells mL−1), highlighting the influence of distribution on bacterial growth. The systematic approach described herein provides quantitative information on the effect of drinking water properties and distribution system conditions on biological stability, which can assist water utilities in decision-making on treatment or distribution system improvements to better control bacterial growth during water distribution.

Bioleaching of Aluminum Slags with Thermophilic Bacteria

The recovery of metallic aluminum from the waste generated in the production of secondary aluminum by bioleaching process using the nutrient medium MKM was investigated. The development of this project was carried out due to the need to treat waste foundry which have a major impact on the environment, using environmentally friendly techniques, such as bioleaching. At work, bioleaching of smelting slag of aluminum generated in the laboratories of the Department of Metallurgy, Faculty of Chemistry, UNAM, was reported. Tests were conducted using thermophilic microorganisms at 70°C in an orbital incubator at natural pH, obtaining metallic clean aluminum, aluminum in solution and salts solution. The pH, bacterial growth and redox potential were monitored daily. We conclude that bioleaching of aluminum slags is feasible. The lack of information about the treatment of this type of industrial waste, makes this research is pioneer in this field.

Effect of Lactic Acid Bacteria Inoculation on Fermentation Characteristics of Whole Crop Barley Silage

An experiment was carried out to determine the homofermentative activity of Lactobacillus plantarum KCC-10 and KCC-19 on the ensiling of whole crop barley (WCB). The crude protein in the silages was slightly higher in the KCC-10 and KCC-19 treatments compared to the control, but there was no significant difference between the two inoculant-treated silages. Nutrient parameters such as acid detergent fiber, neutral detergent fiber and in vitro dry matter digestibility in L. plantarum KCC-10 and KCC-19 treated silages did not differ from those in the control silage. The lactic acid content increased in KCC-10 and KCC-19 treated silage when compared with the control silage but the contents of acetic acid and butyric acid produced in KCC-10 and KCC-19 treated silages were similar with the control silage. Further, the number of lactic acid bacteria (LAB) in KCC-10 treated silage demonstrated a significant increase when compared to the control. Especially, KCC-19 treated silage showed greater lactic acid bacterial growth potential. Other microbes such as yeast and fungi were not detected in KCC-10 and KCC-19 treated WCB silages. Hence, this study suggests that the addition of L. Plantarum KCC-10 and KCC-19 to the WCB silage can improve fermentation quality for the production of high-quality silage.

Effects of High Pressure Processing on the Quality of Vacuum Packed Fish Patties

The objective of this study was to evaluate the use of high pressure processing (HPP) as a preservation method of meat products. Vacuum-packaged fish patties were subjected to HPP (300 MPa for 30 min 15°C or 500 Mpa for 10 min at 15°C). Untreated samples represented the control group. The three groups were stored at 4°C for 0–5 weeks. Color parameters, pH, thiobarbituric (TBARS), bacterial growth, and Oxidation-Reduction Potential (ORP) were determined. The results revealed that the 500-MPa treatment inhibited bacterial growth and extended the shelf-life of fish patties to four weeks with insignificant effects on the physicochemical attributes.

Improvement of the assimilable organic carbon (AOC) analytical method for reclaimed water

Microbial growth is an issue of concern that may cause hygienic and aesthetic problems during the transportation and usage of reclaimed water. Assimilable organic carbon (AOC) is an important parameter which determines the heterotrophic bacterial growth potential of water. Pseudomonas fluorescens P17 and Spirillum sp. NOX are widely used to measure AOC in drinking water. The AOC values of various reclaimed water samples determined by P17 and NOX were compared with those determined by the new strains isolated from reclaimed water in this study. It showed that the conventional test strains were not suitable for AOC measurement of reclaimed water in certain cases. In addition to P17 and NOX, Stenotrophomonas sp. ZJ2, Pseudomonas saponi- phila G3 and Enterobacter sp. G6, were selected as test strains for AOC measurement of reclaimed water. Key aspects of the bioassay including inoculum cell density, incubation temperature, incubation time and the pH of samples were evaluated for the newly selected test strains. Higher inoculum density (10 4 CFU$mL -1 ) and higher incubation temperature (25°C) could reduce the time required for the tests. The AOC results of various collected samples showed the advantages of the method proposed based on those five strains in evaluating the biologic stability of reclaimed water.

Residual lens cortex material: Potential risk factor for endophthalmitis after phacoemulsification cataract surgery

To evaluate the bacterial growth potential of residual lens cortex after phacoemulsification with the development of endophthalmitis. University medical center. Experimental study. Staphylococcus aureus and Staphylococcus epidermidis were dispensed into aqueous humor or serial dilutions of lens cortex that were obtained from cataract patients during phacoemulsification. After a 24-hour incubation, the colony-forming unit (CFU) was quantified. Eighty rabbits had phacoemulsification. Complete lens cortex removal was performed in 40 rabbits, while a quarter of lens cortex was retained in 40 rabbits. Staphylococcus aureus, with an inoculum size of 32 CFU, 56.3 CFU, and 108.6 CFU, was injected intracamerally at the conclusion of surgery and the production of endophthalmitis was measured 72 h later. The aqueous and vitreous humor samples were collected for microbiological diagnosis. The increase in bacterial growth of S aureus and S epidermidis was statistically significantly greater in each dilution of lens cortex than in aqueous humor (P < .001, Student t test). With inoculum of 32.0 CFU or 56.3 CFU of S aureus, there was a statistically higher incidence of bacterial culture-proven endophthalmitis in the residual lens cortex eye group than in the normal aphakic eye group (P < .05, Fisher exact test). Lens cortex was associated with a significant increase in bacterial growth compared with aqueous humor. Therefore, eyes with residual lens cortex seem more prone to develop endophthalmitis if anterior chamber bacterial contamination occurs during phacoemulsification. No author has a financial or proprietary interest in any material or method mentioned.

Assessing bacterial growth potential in a model distribution system receiving nanofiltration membrane treated water

This study was designed to assess the extent of bacterial growth in a model distribution system fed with the water treated by nanofiltration (NF) membranes under controlled conditions. The three NF membranes were used in improving the quality of tap water in a lab-scale process. The changes in total cell counts and culturable heterotrophic bacteria in both bulk water and biofilm were monitored during transport of NF permeate water through the model distribution system. The NF membranes were capable of removing the assimilable organic carbon (AOC) contents, but not low enough to restrict bacterial growth. Bacterial adhesion and cellular proliferation were observed in the NF permeate-fed systems, which were apparently characterized by the increase in the fraction of culturable heterotrophic bacteria and the relative abundance of α-Proteobacteria in bacterial community of biofilms. The overall specific cell growth rate which indicates the growth potential in the whole system was calculated as 0.07–0.08day−1. Results indicate that the NF permeate water has some potential to support bacterial growth in a distribution system, although the NF membrane is able to improve the quality of drinking water. Consequently, proper care should be taken to secure biostability to acceptable levels.

Differing Growth Responses of Major Phylogenetic Groups of Marine Bacteria to Natural Phytoplankton Blooms in the Western North Pacific Ocean

Growth and productivity of phytoplankton substantially change organic matter characteristics, which affect bacterial abundance, productivity, and community structure in aquatic ecosystems. We analyzed bacterial community structures and measured activities inside and outside phytoplankton blooms in the western North Pacific Ocean by using bromodeoxyuridine immunocytochemistry and fluorescence in situ hybridization (BIC-FISH). Roseobacter/Rhodobacter, SAR11, Betaproteobacteria, Alteromonas, SAR86, and Bacteroidetes responded differently to changes in organic matter supply. Roseobacter/Rhodobacter bacteria remained widespread, active, and proliferating despite large fluctuations in organic matter and chlorophyll a (Chl-a) concentrations. The relative contribution of Bacteroidetes to total bacterial production was consistently high. Furthermore, we documented the unexpectedly large contribution of Alteromonas to total bacterial production in the bloom. Bacterial abundance, productivity, and growth potential (the proportion of growing cells in a population) were significantly correlated with Chl-a and particulate organic carbon concentrations. Canonical correspondence analysis showed that organic matter supply was critical for determining bacterial community structures. The growth potential of each bacterial group as a function of Chl-a concentration showed a bell-shaped distribution, indicating an optimal organic matter concentration to promote growth. The growth of Alteromonas and Betaproteobacteria was especially strongly correlated with organic matter supply. These data elucidate the distinctive ecological role of major bacterial taxa in organic matter cycling during open ocean phytoplankton blooms.

Growth potential of faecal bacteria in simulated psychrophilic/mesophilic zones during composting of organic waste

This study investigated the growth potential of Salmonella serotype Typhimurium and faecal indicator organisms in compost materials and the correlation between bacterial growth potential and the physico-chemical composition of the compost substrate and temperature. Survival of Salm. Typhimurium, Enterococcus spp. and total coliforms at 14, 24 and 37 degrees C was determined in material of different degrees of maturity collected from composting plants for household waste and manure. All three micro-organisms showed the potential for growth in the material from active composts (Solvita index 4) but inactivation generally occurred over time in mature compost material (Solvita index 7-8). Salm. Typhimurium had the potential for growth in psychrophilic/mesophilic (P/M) zones of immature compost material and its growth potential correlated negatively with the maturity of the compost and the temperature within the simulated P/M zone. The risk of pathogen regrowth in P/M zones during organic waste composting further emphasizes the importance of good management practices and of avoiding P/M zones in combination with low compost maturity.

Importance of rare and abundant populations for the structure and functional potential of freshwater bacterial communities

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 47:1-10 (2007) - doi:10.3354/ame047001 Importance of rare and abundant populations for the structure and functional potential of freshwater bacterial communities Katalin É. Szabó1,2, Paul O. B. Itor1, Stefan Bertilsson1, Lars Tranvik1, Alexander Eiler1,* 1Department of Ecology and Evolution, Limnology, Uppsala University, Husargatan 3 Box 573, Uppsala 75237, Sweden 2Hungarian Danube Research Station of the Hungarian Academy of Sciences, Jávorka Sándor utca 14, Göd 2131, Hungary *Corresponding author. Email: alexander.eiler@ebc.uu.se ABSTRACT: Lakewater microcosms were inoculated with freshwater bacterioplankton, to determine how the elimination of less abundant populations affects the structure and basic functional features (growth) of microbial communities. The number of bacteria added to individual microcosms varied from <1 to 2.6 × 107 cells. Cultures amended with 11 mg C l–1 of either isolated humic substances or phenol, as well as unamended controls, were studied in parallel. All cultures inoculated with 260 cells or more showed vigorous growth, whereas an inoculum size of 2.6 to 26 cells resulted in growth in the control and humic enrichment cultures only. All cultures were harvested at steady state within 14 d of inoculation. The biomass yield was only slightly affected by the dilution factor. The catechol 2,3-dioxygenase gene (encoding the enzyme responsible for starting the meta pathway of aromatic compound degradation) was detected in all phenol and in the least diluted humic enrichment cultures. Dominant members of the emerging bacterial communities were detected by terminal restriction fragment length polymorphism (T-RFLP) of PCR-amplified 16S rRNA genes. The number of detected community members was much higher in the humic treatment than in the phenol and control treatments. Based on the T-RFLP data, dilution of the inoculum significantly affected the resulting community composition (p < 0.0001). Rare, opportunistic populations were apparently able to exploit the humic enrichment cultures. Phenol appeared to be detrimental to the most abundant members of the original inoculum, but promoted the growth of relatively rare species carrying the catechol 2,3-dioxygenase gene. Thus, community functioning following an environmental perturbation can depend on the presence of rare as well as abundant species. Bacterioplankton · Dilution · 16S rRNA · T-RFLP · Catechol 2,3-dioxygenase · Bacterial growth potential Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 47, No. 1. Online publication date: April 03, 2007 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2007 Inter-Research.

Biostability characterization in a full‐scale hybrid NF/RO treatment system

The objective of this study was to quantify the assimilable organic carbon (AOC) in processing water at several stages of a full‐scale nanofiltration (NF) water treatment plant. The NF membrane plant investigated was a 45,400‐m3/d (12‐mgd) water‐softening facility in Plantation, Fla. The average AOC concentration of raw feedwater was estimated at 158 μg/L acetate‐C. After pretreatment (acid and antiscalant addition), AOC levels increased by 12.7% (p‐value = 0.055), suggesting that pretreatment chemicals used to control scaling may enhance bacterial growth potential on the membrane surface. The results also demonstrated that the membrane system was capable of effectively removing 63.4% of AOC and showed a decrease in membrane productivity over time (declined linearly at a rate of approximately 1.2 times 10‐4 L/m2/h ÷ kPa [4.9 times 10‐4 gfd ÷ psi] per d). This decrease could be attributed to biofouling, as observed by a steady increase in differential pressure during operation, and to natural organic matter fouling, as shown by the composition of the organic matter in the feedwater (54.9% hydrophobic and 18.1% hydrophilic neutral compounds).

Characterization of bioluminescent derivatives of assimilable organic carbon test bacteria.

The assimilable organic carbon (AOC) test is a standardized measure of the bacterial growth potential of treated water. We describe the design and initial development of an AOC assay that uses bioluminescent derivatives of AOC test bacteria. Our assay is based on the observation that bioluminescence peaks at full cell yield just prior to the onset of the stationary phase during growth in a water sample. Pseudomonas fluorescens P-17 and Spirillum sp. strain NOX bacteria were mutagenized with luxCDABE operon fusion and inducible transposons and were selected on minimal medium. Independent mutants were screened for high luminescence activity and predicted AOC assay sensitivity. All mutants tested were able to grow in tap water under AOC assay conditions. Strains P-17 I5 (with p-aminosalicylate inducer) and NOX I3 were chosen for use in the bioluminescence AOC test. Peak bioluminescence and plate count AOC were linearly related for both test bacteria, though data suggest that the P-17 bioluminescence assay requires more consistent luminescence monitoring. Bioluminescence results were obtained 2 or 3 days postinoculation, compared with 5 days for the ATP luminescence AOC assay and 8 days for the plate count assay. Plate count AOC assay results for nonmutant and bioluminescent bacteria from 36 water samples showed insignificant differences, indicating that the luminescent bacteria retained a full range of AOC measurement capability. This bioluminescence method is amenable to automation with a microplate format with programmable reagent injection.

Appréciation quantitative de la croissance bactérienne potentielle à partir de profils temps/température: Exemples d'application pour la croissance de Salmonella Typhimurium dans un steak haché

The preservation of food safety requires risk analyses and the implementation of preventive measures, as well as the availability of quantitative criteria to help the decision process. Up until now, the main difficulty was to quantify the microbial growth in foodstuffs. This article presents criteria used to calculate the bacterial growth potential, based on predictive microbiology models. In combination with a microbial expert’s report, these criteria predict growth based on time-temperature profiles of a given food. Two practical examples, including a description of the method of calculation, are also given.

Development of a Rapid Assimilable Organic Carbon Method for Water

A rapid method for measurement of assimilable organic carbon (AOC) is proposed. The time needed to perform the assay is reduced by increasing the incubation temperature and increasing the inoculum density. The ATP luciferin-luciferase method quickly enumerates the test organisms without the need for plate count media or dilution bottles. There was no significant difference between AOC values determined with strain P17 for the ATP and plate count procedures. For strain NOX, the plate count procedure underestimated bacterial levels in some samples. Comparison of AOC values obtained by the Belleville laboratory (by the ATP technique) and the Stroud Water Research Center (by plate counts) showed that values were significantly correlated and not significantly different. The study concludes that the rapid AOC method can quickly determine the bacterial growth potential of water within 2 to 4 days.

Comparison of assimilable organic carbon and UV-oxidizable carbon for evaluation of ultrapure-water systems

Bacterial growth potential was measured in an ultrapure-water pilot plant by modified assimilable organic carbon (AOC) and UV-oxidizable carbon tests. An ion-exchange unit increased UV-oxidizable carbon, yet did not significantly (P greater than or equal to 0.05) alter AOC values. UV radiation decreased UV-oxidizable carbon and increased AOC.