Equivalents Of Chlorine Research Articles

Adverse effects of ozonation on the animal welfare of tilapia Oreochromis niloticus in recirculation aquaculture

Ozone is often used to disinfect process water in recirculating aquaculture systems. Here, ozone rapidly leads to the formation of secondary oxidants, called ozone produced oxidants (OPO). We studied the impact of OPO on juvenile tilapia Oreochromis niloticus in brackish water at 0, 0.05, 0.1 and 0.15 mg/L chlorine equivalents after 2 d, 9 d and 21 d of exposure, assessing gill histopathology and lesions of the mitochondrial DNA. Damage of the gills was already observed after 2 d, comprising an increased occurrence of lamellar lifting, fusion of the lamellae and edema at 0.15 mg/L. After 21 d, occurrence of lamellar fusion and edema was elevated at 0.15 mg/L. Increased incidence of hyperplasia was already observed at 0.05 mg/L after 9 d. DNA fragmentation increased to 3.92 lesions per 10 kb at 0.15 mg/L compared to 2.62 lesions per 10 kb in the control. In conclusion, first adverse effects were observed at 0.05 mg/L and severe impact is subsequently recorded at 0.1 mg/L chlorine equivalents. Therefore, OPO concentrations need to be kept below 0.05 mg/L chlorine equivalents to avoid adverse effects on animal welfare.

The effects of pre-processing sanitation and modified atmosphere packaging on microbial growth in bulk packs of Atlantic salmon (Salmo salar) fillets

This research was to extend the shelf-life of fresh Atlantic salmon fillets when packaged in bulk food service modified atmosphere packaging trays with low gas to product volume ratios. When head-on-gutted Atlantic salmon were washed in Neutral electrolyzed water sanitizer prior to filleting, the microbial load on the skin of HOGs treated at 20 ppm and 100 ppm chlorine equivalents decreased by 3.5 log CFU/cm2 down to 2.0 and 1.5 log CFU/cm2, respectively. Further trials washed the HOGs with 100 ppm of NEW before filleting. They were then packed in a different product gas to product (G/P) volume ratios (0.4:1, 1:1 and 2:1) and stored at 0°C or 4°C up to 20 days. The combinations of sanitation pre-processing and high G/P ratio were most effective for controlling the microbial count to 4.5 log CFU/g when stored at 0°C compared to a microbial count of 7.2 log CFU/g for the unwashed fillets after 20 days under 4°C storage. Other variable combinations were between these levels. A combination of improved pre-processing sanitation and a low temperature can therefore raise the hurdles for microbial growth to extend the shelf-life of bulk packed fresh salmon fillets packed at high volumetric densities for storage and shipping efficiency.

Disinfection by-products formation and precursors transformation during chlorination and chloramination of highly-polluted source water: Significance of ammonia

Many studies have demonstrated the different trends of disinfection by-products (DBPs) formation between chlorination and chloramination. However, the reactions between precursors and disinfectants are widely assumed to be “black box” and the reasons for abovementioned difference are not well illustrated. This study focused on source water with high levels of natural organic matter (NOM) and bromide, and compared the transformation of NOM specific characteristics and the ratios of specific DBPs as an equivalent of chlorine to total organic halogen (TOX) among three disinfection scenarios of chlorination, chloramination and chlorine–chloramine sequential treatment (Cl2–NH2Cl process). A three-reaction-phrases model was proposed thereafter to illustrate the major reactions involved in, i.e., stage-I: rapid consumption of fast reactive sites (DOC1), which transformed to slow reactive sites (DOC2) and measured DBPs, i.e., trihalomethanes, haloacetic acids, etc; stage-II: oxidation and/or halogenation of DOC2 into unknown TOX (UTOX) intermediates; stage-III: oxidation of UTOX intermediates into measured DBPs. The effect of ammonia was also quantified. Ammonia is observed to inhibit the formation of measured DBPs by 68–92%, 94–99%, and 92–95% of that in chlorination in Stage-I, II, and III, respectively, and the formation of UTOX is reduced by 2–80%, 60–94%, and 82–93% accordingly. These effects lead to the steady accumulation of DBPs intermediates such as UTOX, and to the elevated UTOX/TOX during chloramination and Cl2–NH2Cl process thereafter. The results illustrate the mechanism of ammonia participating in DBPs formation, and are valuable to fill in the gap between the transformation of precursors and the formation of different DBPs.

Determination of odour threshold concentration ranges for some disinfectants and disinfection by-products for an Australian panel

Taste-and-odour complaints are a leading cause of consumer dissatisfaction with drinking water. The aim of this study was to determine odour threshold concentration ranges and descriptors, using a Western Australian odour panel, for chlorine, bromine, chlorine added to bromide ions, the four major regulated trihalomethanes (THMs), and combined THMs. An odour panel was established and trained to determine odour threshold concentration ranges for odorous compounds typically found in drinking water at 25 degrees C, using modified flavour profile analysis (FPA) techniques. Bromine and chlorine had the same odour threshold concentration ranges and were both described as having a chlorinous odour by a majority of panellists, but the odour threshold concentration range of bromine expressed in free chlorine equivalents was lower that that of chlorine. It is likely that the free chlorine equivalent residuals measured in many parts of distribution systems in Western Australia are comprised of some portion of bromine and that bromine has the potential to cause chlorinous odours at a lower free chlorine equivalent concentration than chlorine itself. In fact, bromine is the likely cause of any chlorinous odours in Western Australian distributed waters when the free chlorine equivalent concentration is between 0.04 and 0.1 mg L(-1). Odour threshold concentrations for the four individual THMs ranged from 0.06-0.16 mg L(-1), and the odour threshold concentration range was 0.10 + or - 0.09 mg L(-1) when the four THMs were combined (in equal mass concentrations). These concentrations are below the maximum guideline value for total THM concentration in Australia so odours from these compounds may possibly be observed in distributed waters. However, while the presence of THMs may contribute to any sweet/fragrant/floral and chemical/hydrocarbon odours in local drinking waters, the THMs are unlikely to contribute to chlorinous odours.

Regio-and stereoselective chlorination of 2,6-Dichloro-4-phenyl-3,4,5,6-tetrahydro-2H-1,2λ5-benzoxaphosphinin-2-one: Addition of two equivalents of chlorine with aromaticity disturbance

Regio-and stereoselective chlorination of 2,6-Dichloro-4-phenyl-3,4,5,6-tetrahydro-2H-1,2λ5-benzoxaphosphinin-2-one: Addition of two equivalents of chlorine with aromaticity disturbance

TLC Fractionation and Characterization of Ames Mutagenic Substances in Chlorine-treated 4-methylphenol Solution in the Presence of Bromide Ion

The diethyl ether extracts from aqueous 4-methylphenol solutions in the presence of bromide ion after treatment with chlorine were mutagenic to the Ames salmonella test strain TA100 in the absence of rat liver homogenate. Gas chromatography/mass spectrometry (GC/MS) showed the occurrence of halogenated products in the extracts: bromo-4-methylphenols, bromo-4-methylquinones and brominated 4-methylphenol dimers. The diethyl ether extracts were fractionated into several fractions by polyamide thin-layer chromatography (TLC) . The fractionated components were examined for mutagenicity by means of Ames assays, and were identified by GC/MS. TLC fraction of the extracts revealed that two components present in the extracts are mutagenic. GC/MS analysis indicated the presence of 2, 6-dibromo-4-hydroxy-4-methylcyclohexa-2, 5-lien-1-one (2, 6-dibromotolquinol) as the major mutagen and brominated 4-methylphenol dimers as minor mutagenic compounds in the chlorinated 4-methylphenol solutions containing bromide ion. Production of 2, 6-dibromotolquinol in water was found to be dependent on the equivalents of chlorine per mole of compound and the reaction pH.

Transformation of Aqueous Phenolic Compounds in the Presence of Natural Organics and Chlorine into Ames Mutagenic Chloro-o-benzoquinones.

Some of chlorinated o-benzoquinones (o-BQs) have been shown to be mutagenic in Ames Salmonella assays. However, no study has been reported on the quantitative estimate of such compounds in aqueous solution. These mutagenic chemicals present in chlorine-treated aqueous solutions of mono- and dihydric phenols were, therefore, quantitatively determined by GC-MS as their phenazine derivatives.Chlorination of aqueous catechol solution was shown to produce a series of chlorinated compounds, including Chloro-o-BQs, and Chloro-hydroxy-o-BQ, in addition to o-BQ. No Chloro-o-BQs were found to be present in chlorine-treated resolcinol and hydroquinone solutions. After treatment with chlorine of aqueous chlorophenol solutions, dichloro-o-BQs were detected in these solutions. Production of chloro-o-BQs in water is dependent on the equivalents of chlorine per mole of compound, the reaction pH and the presence of lignin or humic acid. These results show that treatment with chlorine of water and wastewater contaminated with phenolic compounds leads to the production of mutagenic chlorinated o-BQs.

Chemical Changes of Organic Compounds in Chlorinated Water. XIX. Production of Alkylpolychlorinated Phenoxyphenols (Predioxins) by Aqueous Chlorination of Alkylphenols.

Aqueous alkylphenol solutions were treated with chlorine at 20°C under various experimental conditions. Changes in the compositions of the chlorination products in water were determined by gas chromatographic (GC) and GC-mass spectrometric (GC-MS) analyses of diethyl ether extracts. Alkylphenols were shown to produce a variety of chlorinated compounds, including alkylpolychlorinated phenoxyphenols (predioxins), having one to five chlorine atoms, as by-products in chlorine-treated water. Production of some of these predioxins is dependent on the number of equivalents of chlorine per mol of compound and on the reaction pH. These results suggest that chlorine treatment of water contaminated with alkylphenols leads to the production of predioxins, which are precursors of the highly toxic chlorinated dibenzo-p-dioxins.

Mutagenicity on chlorination of products formed by ozonation of naphthoresorcinol in water

The mutagenicity of products formed by chlorination after ozonation of naphthoresorcinol in aqueous solution was assayed with Salmonella typhimurium strains TA98 and TA100 in the presence and absence of S9 mix from phenobarbital- and 5,6-benzoflavone-induced rat liver. Ozonated and subsequently chlorinated naphthoresorcinol was directly mutagenic, as was ozonated naphthoresorcinol, in both strains tested. The mutagenic activity at chlorination with 8 equivalents of chlorine per mole of naphthoresorcinol after ozonation was markedly higher than that at only ozonation. Of the identified ozonation products of naphthoresorcinol, muconic acid, after chlorination with 2 or 4 equivalents of chlorine per mole of the compound, induced direct mutagenicity against TA98 and TA100. The chlorination of glyoxal with 0.5 and 1 chlorine equivalents per mole of the compound was shown to produce direct mutagenicity toward TA98. The identification of the chlorination products of these compounds is also discussed.

SOS Chromotest study concerning some appreciation criteria of humic substances' genotoxic potency

The genotoxicity of 5 compounds: 2 fulvic acids, a trade humic acid, a synthetic humic material (SHM), and 2,5-dihydroxybenzoic acid, was assessed after chlorination, by means of the SOS Chromotest for tester strain E. coli PQ 37 without metabolic activation. Chlorination was carried out for humic material concentration of 0.5 mg total organic carbon per liter, and chlorine concentrations in the range of 0.1–2.0 chlorine equivalents per mole of carbon. Among all the considered criteria that can account for potent toxicity: chemical degradation determined by the UV absorption decrease, chlorine consumption, average molecular weight, only the polymerization index (O.D. 665 nm/O.D. 465 nm) can be related to the genotoxicity of humic samples. This latter criterion appears a possible predictor of genotoxic potency, revealed subsequent to the aqueous chlorination of humic materials. Looking at the various genotoxic activities of the tested compounds, SHM can be considered a better model of natural humic materials than the trade humic acid.

Mutagenicity and alkylating activity of the aqueous chlorination products of humic acid and their molecular weight fractions

Fluka humic acid used as a model substrate in these studies was analysed for elemental and the oxygen-containing functional groups. It was chlorinated at C:Cl molar ratios of 1:1 and 1:0.3 and subsequently separated into molecular weight fractions by ultrafiltration. The freeze-dried, chlorinated humic acid and the respective molecular weight fractions were analyzed for TOC, TOX, alkylating activity using 4-( p-nitrobenzyl)pyridine and mutagenicity by the Ames/Salmonella/ microsome assay with strains TA-98 and TA-100. Results indicated that predominantly non-volatile, direct-acting mutagenic and/or alkylating agents were formed during humic acid chlorination and that these agents were unevenly distributed among the various molecular weight fractions. Formation of mutagenic and akylating agents were highly dependent upon level of chlorination and total organic carbon. Higher levels of mutagenic and alkylating activities were produced with increasing concentration of chlorine in the range of 0.4–1.2 chlorine equivalents per mole of carbon. However, both these activities in the freeze-dried, chlorinated humic acid solutions containing the non-volatiles or the fresh solutions decreased gradually with increasing pH and storage time, apparently due to degradation and hydrolysis of some of the components.

Production of polychlorinated phenoxyphenols (predioxins) by aqueous chlorination of organic compounds

The reactions of phenolic substances with hypochlorite in water were investigated by means of gas chromatography-mass spectrometry. Chlorinated and methylated phenols were shown to produce polychlorinated phenoxyphenols (predioxins), having one to nine chlorine atoms, as the by-products in chlorine-treated water. The production of some of these compounds is dependent on the number of equivalents of chlorine per mol of compound and on the reaction pH.

Chemical changes of organic compounds in chlorinated water : XIII. Gas chromatographic—mass spectrometric studies of the reactions of Irgasan DP 300 [5-chloro-2-(2,4-dichlorophenoxy_phenol] with chlorine in dilute aqueous solution

The reactions of Irgasan DP 300 with chlorine in water were investigated by means of gas chromatography (GC) and GC—mass spectrometry. Irgasan DP 300 was shown to produce dichloro- and trichloro-2-(2,4-dichlorophenoxyl)phenols in chlorine-treated water, followed by the decomposition of these intermediates to chlorophenols. No polychlorinated dibenzo- p-dioxins were detected in chlorine-treated Irgasan DP 300 solutions. The production of some of these compounds is dependent on the number of equivalents of chlorine per mol of compounds and on the reaction pH.

Chemical changes of organic compounds in chlorinated water : X. Formation of polychlorinated methylphenoxymethylphenols (predioxins) during chlorination of methylphenols in dilute aqueous solution

Aqueous methylphenol ( o-, m- and p-isomers) solutions were treated with hypochlorite at 20°C under various experimental conditions. Changes in the compositions of the chlorination products in water were determined by using gas chromatographic (GC) and GC—mass spectrometric analyses of diethyl ether extracts. The chlorination of methylphenols in dilute aqueous solutions produced a series of highly chlorinated compounds, including chloromethylphenols, chloromethylbenzoquinones and chlorinated carboxylic acids. Tentative identifications were also made for other compounds with following molecular formulae: C 14H 5Cl 2O 2, C 14H 4Cl 3O 2 and C 14H 3Cl 4O 2. On the basis of the thin-layer chromatographic and GC behaviour and mass fragmentation patters, the compounds are considered to be chlorinated methylphenoxymethylphenols. The production of some of these compounds is dependent on the number of equivalents of chlorine per mol of compound and the reaction pH. These results show that treatment with chlorine of water contaminated with phenolic compounds leads to the production of chlorinated phenoxyphenols (predioxins), which are precursors of the highly toxic chlorinated dibenzo- p-dioxins.

Chemical changes of organic compounds in chlorinated water : IX. Formation of polychlorinated phenoxyphenols during the reaction of phenol with hypochlorite in dilute aqueous solution

Aqueous phenol solutions were treated with hypochlorite at 20°C under various experimental conditions. Changes in the composition of the chlorination products in water were determined by using gas chromatographic (GC) and GC-mass spectrometric analyses of diethyl ether extracts. Chlorination of phenol in dilute aqueous solution produced a series of highly chlorinated compounds, including chlorophenols, chlorobenzoquinones and chlorinated carboxylic acids. Tentative identifications were also made for other compounds with the following proposed molecular formulae: C 12H 8Cl 2O 2, C 12H 7Cl 3O 2, C 12H 6Cl 4O 2 and C 12H 5Cl 5O 2. On the basis of thin-layer chromatographic and GC behaviour, these compounds are considered to be chlorinated phenoxyphenols. Production of some of these compounds is dependent on the equivalents of chlorine per mole of compound and the reaction pH. These results show that treatment with chlorine of water contaminated with phenolic compounds leads to the production of chlorinated phenoxyphenols.

Formation of mutagens following chlorination of humic acid A model for mutagen formation during drinking water treatment

Aqueous chlorination of humic acids results in the formation of compounds with direct-acting mutagenic activity in the Ames/Salmonella plate assay for tester strains TA98, TA100, TA1535, TA1537 and TA1538. The addition of a rat-liver microsomal fraction (S9) plus cofactors causes a substantial decrease of activity, the extent of which is tester strain dependent. The non-chlorinated humic acids are not mutagenic either in the presence or absence of S9. Formation of mutagenic activity and of total organic halogen (TOX) is linearly related to humic concentration in the range of 0.2–1.6 mg/ml total organic carbon (TOC), and to chlorine concentration in the range of 0.1–1.0 chlorine equivalents per mole of carbon. The mutagenic activity is due predominantly to non-volatile compounds. Mutagenic activity is also detectable, after sample concentration by lyophilization, upon chlorination at a humic acid level of 0.02 mg/ml TOC. The specific mutagenic activities (per mg TOX), and also the degree of chlorine incorporation into humic acid, at 0.02 mg/ml TOC are similar to those present after chlorination at 1 mg/ml TOC. Production of mutagens is greatly dependent on the chlorination pH, with a pattern of decreasing mutagenic activity with increasing pH. This order of activity can be at least partially explained by the alkali lability of the compounds. Chlorination of commercial humic acids is proposed as a model for examination of mutagen formation during water chlorination.

Mutagenic reaction products of aqueous chlorination of catechol

Aqueous chlorination of catechol (4 and 8 mM) at varying reagent ratio has been shown to produce high mutagenicity with the Ames Selmonella strain TA100. The mutagenicity peaks at 3 equivalents of chlorine per mole of catechol. But the mutagens are unstable in neutral and alkaline solutions. Substituted catechols produce less mutagenic solutions than catechol on aqueous chlorination. If the chlorine is replaced with equivalent chlorine dioxide very little mutagenicity is produced. Among the reaction products; are chlorinated catechols; all of these were synthesized, none was mutagenic but some were toxic. The simple oxidation products, o-benzoquinone and chloro- o-benzoquinone, have been identified and through synthesis were proven to be mutagenic. Some possible ring fracture products also become mutagenic after reaction with aqueous chlorine. Catechol and other simple phenolic substrates are model compounds for the aqueous reaction of chlorine with wood pulp, sewage water and potable water.

Certification Corner

This month's “Certification Corner” covers ferrous sulfate dosage equivalents, available chlorine equivalents, gauge pressure, calculation of total dynamic head and water horsepower, pipe carrying capacity, carbon dioxide removal, free available chlorine residual, and filter media growth.

Certification Corner

Questions in this month's “Certification Corner” cover carrying capacity of water mains, use of activated carbon, characteristics of “strong” and “weak” acids, the amperometric titration method, calcium hypochlorite, water horsepower calculation, distribution system pressure, and liquid and gaseous chlorine equivalents.

Active site chlorination of D-amino acid oxidase by N-chloro-D-leucine.

N-Chloro-D-leucine is an irreversible inhibitor or D-amino acid oxidase on a time scale of seconds. Studies with N-[36C]chloro-D-leucine, N-chloro-D-[1-14C]leucine and N-chloro-D-[4,5-3H]leucine show that the modified enzyme has been chlorinated at a site, or sites, on the apoenzyme. The 36Cl measurements agree with titrations of catalytic activity in showing that two chlorine equivalents are incorporated per active site flavin. Kinetically, the interaction with N-chloro-D-leucine behaves in a manner which is consistent with consecutive chlorinations of an amino acid residue, or residues, in the active site region by the first 2 molecules of N-chloro-D-leucine to be processed by the enzyme. The effect of chlorination of the enzyme on the steady state parameters for oxidation of D-alanine is entirely explained by a single perturbation, namely, a 1000-fold reduction in the specific rate of flavin reduction as measured directly by rapid reaction techniques.