The effects of free chlorine and chloramine on growth and respiration rates of larval lobsters (Homarus Americanus)

The length, dry weight and standard respiration rate of larval lobsters (Homarus americanus) were monitored for 19 days following a 60 min exposure at 25°C to 1.0 mg I⁻¹ applied free chlorine and 1.0 mg I⁻¹ applied chloramine. Compared to control organisms, significantly lower increases in dry weight (P < 0.05) and significant reductions in standard respiration rates (P < 0.01) were measured among exposed organisms; greater differences were detected among chloramine exposed organisms. From these results it can be concluded that acute exposure to either free chlorine or chloramine results in subsequent reductions in growth and metabolic activity of larval lobsters.     

Some physiological responses of rainbow trout (Salmo gairdneri) to intermittent monochloramine exposure

Rainbow trout (Salmo gairdneri) were exposed for 2.5 h to monochloramine (NH₂Cl) at an average concentration of 0.16 or 0.23 mg l⁻¹ (and with peak concentrations of 0.4 or 0.6 mg l⁻¹) three times daily. This simulates conditions in the outfall area of many electric power plants. Heart rate, opercular movement, cough frequency, arterial PO₂, lactate, hemoglobin and methemoglobin were monitored. The trout responded to chloramine pulses with slight increases in opercular movement, bradycardia, and a large increase in cough rate. These factors approached control rates between periods of exposure to a peak concentration of 0.4 mg l⁻¹, but not when the peak was 0.6 mg l⁻¹. Neither hemoglobin or lactate changed, while arterial PO₂ decreased slightly but not significantly. Methemoglobin concentration increased markedly at the end of each period of exposure with some recovery between them. In contrast to free chlorine, which causes acute hypoxemia due to gill damage, chloramine at these concentrations causes little if any hypoxemia. The elevated methemoglobin levels, not seen following exposure to free chlorine, indicate that perhaps chloramine is entering the blood stream to an extent that does not occur with free chlorine. Methemoglobinemia is probably not the proximate cause of death.     

Reduction of aquatic toxicity of linear alkylbenzene sulfonate (LAS) by biodegradation

Partial biodegradation of LAS is shown to significantly reduce the specific toxicity (i.e. per unit weight) of the remaining LAS to Daphnia magna (water fleas) and Pimephales promelas (fathead minnows). This results from the fact that the longer homologs and more terminal isomers, which are the more toxic, are also the more rapidly degraded under bacterial action. The acute aquatic LC₅₀ of LAS may range from 0.5 to 50 mg/l depending mainly upon the chain length of the particular homolog. A high molecular weight commercial type LAS with LC₅₀ around 2 mg/l before biodegradation may show Daphnia LC₅₀'s of 30–40 mg/l. for the LAS remaining after 80–85% degradation.A further contribution to this toxicity reduction may occur if the methylene blue analytical method is used to determine the amount of LAS remaining, since some of the biodegradation intermediates show methylene blue activity but no significant toxicity. For example, sulfophenylundecanoate, a model of early intermediates, shows Daphnia and fathead lc₅₀'s 200 and 75 mg/l., respectively. Sulfophenylbutyrate, modeling somewhat later intermediates, gives lc₅₀ values around 5000–10,000 mg/l. Dialkyl tetralin/indane sulfonates (the major non-linear components in commercial LAS) exhibit 1/2–1/10 the toxicity of the corresponding LAS homologs.These results re-emphasize that analysis simply for methylene blue active substances (MBAS) gives no basis for predicting the aquatic toxicity of an environmental sample. And furthermore, that meaningful water quality criteria and standards cannot be established in terms of MBAS content while based on toxicity studies on intact, undegraded LAS.     

The toxicity of various mining flotation reagents to rainbow trout (Salmo gairdneri)

Preliminary testing of eight collectors (xanthates) and four frothers in 96-h static and 28-day flow-through bioassays using rainbow trout as the test organism show a great disparity in the toxicity of the chemicals administered in these two ways.For the short-term tests, the relative toxicity of the compounds is expressed as an lc₅₀ or as a range of concentration in mg l⁻¹ in which the lc₅₀ is expected to fall. Of the collectors tested in this way sodium ethyl and potassium amyl xanthate were the most toxic, with lc₅₀'s in the range of 30–50 mg l⁻¹. Among the frothers, xylenol (cresylic acid) was found to be the most toxic (5.6 mg l⁻¹ >lc₅₀ > 3.2 mg l⁻¹) while polypropylene glycol was least toxic (lc₅₀ > 1000 mg l⁻¹).The long-term tests using potassium ethyl, sodium isopropyl, sodium ethyl, and potassium amyl xanthate indicated that in the flow-through system, the toxicity of the chemicals was in the order of 100 fold greater compared with the static bioassay results.     

强化消毒法对水中粪肠球菌灭活效果研究

在实验室条件下,研究了自由氯、氯胺和二氧化氯在不同剂量下对水中粪肠球菌的灭活效果.结果表明,自由氯、氯胺和二氧化氯对水中粪肠球菌具有较好的灭活效果,当消毒剂投加量为1 ～4 mg/L,接触时间为30 min时,粪肠球菌的灭活率基本在99％以上;自由氯的消毒反应速率最快,其次是二氧化氯,氯胺的反应速率最慢.     

Inactivation of heterotrophic bacterial populations in finished drinking water by chlorine and chloramines

The die-off of heterotrophic bacteria from a finished drinking water reservoir, located in southern California, was evaluated using chloramines and free chlorine. Understanding the inactivation of hetertrophic populations is valuable because it reflects the response to disinfection of naturally occurring organisms in their native state and environments. Disinfection studies with the heterotrophic bacterial group were performed during summer and winter months using different chloramine application techniques at pH 6 and 8. In addition, bacteria surviving exposure to chloramines and free chlorine was influenced predominantly by the presence of highly chlorine tolerant, red-pigmented bacteria, identified as Flavobacterium spp. Inactivation by chloramines, though, was chiefly dependent upon the method of application and pH. Viable bacteria recovered from the indigenous population after 60 min of exposure to chloramines (1.0 mg l⁻¹, pH 8) included members of Pseudomonas, Acinetobacter and Flavobacterium. In general, with contact times of 1 h or more, free chlorine and chloramine solutions (1.0–1.6 mg l⁻¹, pH 8) reduced total count levels below 50 colony forming units ml⁻¹.     

Studies on the toxicity of ammonia, nitrate and their mixtures to guppy fry

Using guppy fry as the test fish the individual and joint toxicities of ammonia and nitrate were estimated in static tests at constant pH and temperature. The 72-h lc₅₀ values were 199 and 1.26 mg 1⁻¹ −N for potassium nitrate and free ammonia, respectively. The toxicities of mixtures of the two were additive except at very low ammonia to nitrate ratios. Watson's equation, a disinfection law relating toxicant concentration to survival, was applicable to both toxicants. The applicability of Chick's law and other kinetic models to fish toxicity was also evaluated.     

Formation of organic chloramines during water disinfection - chlorination versus chloramination

Many of the available studies on formation of organic chloramines during chlorination or chloramination have involved model organic nitrogen compounds (e.g., amino acids), but not naturally occurring organic nitrogen in water. This study assessed organic chloramine formation during chlorination and chloramination of 16 natural organic matter (NOM) solutions and 16 surface waters which contained dissolved organic nitrogen (DON). Chlorination rapidly formed organic chloramines within 10 min, whereas chloramination formed organic chloramination much more slowly, reaching the maximum concentration between 2 and 120 h after the addition of monochloramine into the solutions containing DON. The average organic chloramine formation upon addition of free chlorine and monochloramine into the NOM solutions were 0.78 mg-Cl₂/mg-DON at 10 min and 0.16 mg-Cl₂/mg-DON at 24 h, respectively. Organic chloramine formation upon chlorination and chloramination increased as the dissolved organic carbon/dissolved organic nitrogen (DOC/DON) ratio decreased (i.e., DON contents increased). Chlorination of molecular weight (10,000 Da) fractionated water showed that molecular weight of DON would not impact the amount of organic chloramines produced. Comparison of three different disinfection schemes at water treatment plants (free chlorine, preformed monochloramine, and chlorine/ammonia additions) indicated organic chloramine formation could lead to a possible overestimation of disinfection capacity in many chloraminated water systems that add chlorine followed by an ammonia addition to form monochloramine.     

Comparison of chlorine and chloramine in the release of mercury from dental amalgam

The purpose of this project was to compare the ability of chlorine (HOCl/OCl⁻) and monochloramine (NH₂Cl) to mobilize mercury from dental amalgam. Two types of amalgam were used in this investigation: laboratory-prepared amalgam and samples obtained from dental-unit wastewater. For disinfectant exposure simulations, 0.5 g of either the laboratory-generated or clinically obtained amalgam waste was added to 250 mL amber bottles. The amalgam samples were agitated by end-over-end rotation at 30 rpm in the presence of 1 mg/L chlorine, 10 mg/L chlorine, 1 mg/L monochloramine, 10 mg/L monochloramine, or deionized water for intervals of 0 h, 2 h, 4 h, 8 h, and 24 h for the clinically obtained amalgam waste samples and 4 h and 24 h for the laboratory-prepared samples. Chlorine and monochloramine concentrations were measured with a spectrophotometer. Samples were filtered through a 0.45 µm membrane filter and analyzed for mercury with USEPA standard method 245.7. When the two sample types were combined, the mean mercury level in the 1 mg/L chlorine group was 0.020 mg/L (n = 25, SD = 0.008). The 10 mg/L chlorine group had a mean mercury concentration of 0.59 mg/L (n = 25, SD = 1.06). The 1 mg/L chloramine group had a mean mercury level of 0.023 mg/L (n = 25, SD = 0.010). The 10 mg/L chloramine group had a mean mercury level of 0.024 mg/L (n = 25, SD = 0.011). Independent samples t-tests showed that there was a significant difference between the natural log mercury measurements of 10 mg/L chlorine compared to those of 1 mg/L and 10 mg/L chloramine. Changing from chlorine to chloramine disinfection at water treatment plants would not be expected to produce substantial increases in dissolved mercury levels in dental-unit wastewater.     

Effects of Chlorine and chloramine on uptake of inorganic nitrogen by phytoplankton

Chlorine (Cl₂) and chloramine had a debilitating effect on the ability of phytoplankton to take up nitrate and ammonia. Chlorine at an initial concentration of 0.028 mg/l depressed uptake of nitrate by 50%. Uptake of nitrate and ammonia in the presence of 0.1 mg Cl₂/1 or 0.1 mg chloramine/1 did not follow Michaelis-Menten kinetics as did the respective controls. Small quantities of Cl₂ or chloramine may destroy or inactivate enzymes in the cell membrane that are responsible for uptake of nitrate.     

Chlorination of pure bacterial cultures in aqueous solution

The fate and distribution of chlorine in aqueous solutions containing four pure bacterial cultures was studied. Solutions were subjected to chlorination at different initial free chlorine concentrations. Resulting concentrations of residual chlorine were determined by both DPD/FAS titration and membrane introduction mass spectrometry (MIMS). In all cases, false-positive breakpoint chlorination curves, probably attributable to the formation of chloroorganic-N compounds, were observed by DPD/FAS titration, while little or no inorganic residual chloramine was found by MIMS. Free chlorine was observed in similar quantities by both methods after chlorine demand by bacterial cellular materials in solution was satisfied. These results indicated the residual chloramines existed in the form of organic chloramines; these compounds are generally recognized as being poor antimicrobial agents. Further investigation confirmed that the bacterial cells were the source of organic-N compounds. The kinetics of chlorination of pure bacterial suspensions was also studied. The pattern of residual chlorine decay following chlorination of the bacterial suspensions indicated rapid initial free chlorine consumption, followed by slow free chlorine consumption, with trace quantities of inorganic chloramine being formed.     

生长环境对消毒剂灭活粪肠球菌影响效果的试验研究

通过改变培养基稀释度和培养温度以及添加无机生长元素（氯化钾、硫酸镁、三氯化铁）研究了自由氯、氯胺和二氧化氯对不同生长环境下所培养的粪肠球菌的灭活情况。结果表明，当粪肠球菌在100倍稀释的肉汤培养基上生长时，达到3log去除率氯和二氧化氯所需的0值分别增加了2．1和5．5倍，而氯胺所需的D值变化很小；将粪肠球菌的生长温度从22℃调整至44．5℃时，达到3log去除率氯胺所需的C≠值下降了2倍，自由氯和二氧化氯所需的C￡值则变化不大；在营养肉汤培养基中投加K＋（4mmol／L）、Mg2＋（0．4mmol／L）和Fe3＋（0．08mmol／L）后，粪肠球菌对自由氯和二氧化氯的抗性提高了，对氯胺的抗性则变化不大，达到3log去除率自由氯和二氧化氯所需的C￡值最大分别增加了约2．3和19倍。     

Effect of HRT,SRT and temperature on the performance of activated sludge reactors treating bleached kraft mill effluent

Laboratory scale research on the effects of hydraulic retention time (HRT), solids residence time (SRT), high operating temperatures and temperature shocks on activated sludge (AS) treatment of kraft pulping effluent was performed using two 51 continuously fed bioreactors. Baseline performance of the reactors was established at 35°C by operating the reactors at steady state (HRT 10–12 h; SRT 12–15 d) for a period of two months. During this period percent removal of BOD, COD, and toxicity averaged 87.9 ± 4.3, 32.4 ± 9.0, 97.7 ± 0.4, respectively. Reactor MLVSS was 1675 ± 191 mg/l, effluent VSS was 45.5 ± 11.2 mg/l and specific oxygen uptake rate was 16.5 ± 3.3 mg O₂/g MLVSS·h. Varying HRT between 12 and 4 h and SRT between 5 and 15 d indicated that HRT had more of an effect on treatment performance than SRT. Longer HRTs led to improved BOD, COD, toxicity and AOX removal, while longer SRTs were not shown to significantly affect performance. Shorter HRTs and longer SRTs led to significant increases in specific oxygen uptake rates (SOURs). For reactors operated at temperatures between 41 and 50°C, removal of BOD and acute toxicity was comparable to that observed at mesophilic temperatures. COD removal was improved over that observed at mesophilic temperatures, possibly as a result of improved dissolution of organic compounds at the higher temperatures. The effect of temperature shocks (decreases of 7°, 16.5°, 32° and 40.5°C) on reactor performance was proportional to the size of the disturbance. Reactor performance returned to pre-shocking levels within 12–24 h for the two smaller temperature shocks. Approximately 72 h was needed for the system to recover from the two larger temperature shocks (32° and 40.5°C).     

Occurrence and production of chloramines in the chlorination of creatinine in aqueous solution

Occurrence and production of stable chloramines in the chlorination of creatinine, a constituent of perspiration and urine, in aqueous media were studied. Creatinine (5 x 10(-5)M) was treated with free chlorine in aqueous solutions at molar ratios of 0.5-8 (chlorine/creatinine) at pH 7.0 at room temperature for several days. At lower ratios of chlorine, two stable N-chlorocreatinine derivatives, which were determined as dichloramine fractions by the DPD method, were isolated by HPLC and identified by EI-MS and (1)H-NMR. One was 2-chloroamino-1-methylimidazolin-4-one (creatinine chloramine) and the other was 2-chloroamino-5-hydroxy-1-methylimidazolin-4-one (hydroxycreatinine chloramine). In addition, the formation of methylamine was identified by GC-MS analyses of its imine derivative formed with pentafluorobenzaldehyde. Methylamine forms stable chloramines, which might be determined as mono- and/or di-chloramine fractions together with free chlorine by the DPD method in the reaction mixtures at higher molar ratios of chlorine. In practice, small amounts of methylamine (ca. 19 microg/L) were detected in water samples collected from several swimming pools. Hence, methylamine may be an origin of elusive organic chloramine formed in the chlorination of swimming pools. A probable mechanism of the occurrence and processing of chlorination products of creatinine is suggested.     

Kinetics of the oxidation of cylindrospermopsin and anatoxin-a with chlorine, monochloramine and permanganate

Cyanobacteria produce toxins that may contaminate drinking water sources. Among others, the presence of the alkaloid toxins cylindrospermopsin (CYN) and anatoxin-a (ANTX) constitutes a considerable threat to human health due to the acute and chronic toxicity of these compounds. In the present study, not previously reported second-order rate constants for the reactions of CYN and ANTX with chlorine and monochloramine and of CYN with potassium permanganate were determined and the influence of pH and temperature was established for the most reactive cases. It was found that the reactivity of CYN with chlorine presents a maximum at pH 7 (rate constant of 1265 M(-1)s(-1)). However, the oxidation of CYN with chloramine and permanganate are rather slow processes, with rate constants <1 M(-1)s(-1). The first chlorination product of CYN was found to be 5-chloro-CYN (5-Cl-CYN), which reacts with chlorine 10-20 times slower than the parent compound. The reactivity of ANTX with chlorine and chloramines is also very low (k<1M(-1)s(-1)). The elimination of CYN and ANTX in surface water was also investigated. A chlorine dose of 1.5 mg l(-1) was enough to oxidize CYN almost completely. However, 3 mg l(-1) of chlorine was able to remove only 8% of ANTX, leading to a total formation of trihalomethanes (TTHM) at a concentration of 150 microg l(-1). Therefore, chlorination is a feasible option for CYN degradation during oxidation and disinfection processes but not for ANTX removal. The permanganate dose required for CYN oxidation is very high and not applicable in waterworks.     

自由氯、氯胺和顺序氯化对饮用水消毒效果的试验研究

研究了自由氯、氯胺和顺序氯化三种消毒方式对大肠埃希氏菌和粪肠球菌的灭活效果.结果表明,自由氯浓度越高,对细菌的灭活速率和最终灭活率越大;氯胺浓度越高,对细菌的灭活速率和最终灭活率越大;顺序氯化消毒效果优于单独使用自由氯或氯胺时的消毒效果.同时,还探讨了pH和温度对三种消毒方式的影响.     

Acute toxicity test using cyanide on Daphnia magna by flow-through system

This study describes the acute toxicity of sodium cyanide on the crustacean Daphnia magna (Cladocera). A new flow-through system was innovated in which the microorganism continuously exposure to the toxicity of sodium cyanide during the test. We used twelve different concentration of sodium cyanide from low values (0 mg CN/L) to high values (1 mg CN/L) on bioassay test. D. magna were exposed to the concentrations for 24, 48, 72 and 96 h at 20–25°C. We controlled the three important parameters such as temperature, pH and DO to meet the standard requirements. The LC₅₀ values for 24, 48, 72 and 96 h (95% confidence limits in parentheses) were estimated statistically by the probit methods and were 0.171 (0.163–0.179), 0.12 (0.112–0.128), 0.07 (0.062–0.078) and 0.019 (0.011–0.027) mg/L respectively. Finally, we proposed two new values for SAR (safe application rate) and SAFE Coefficients.     

Response of zebra mussel veligers to chemical oxidants

Experimental studies using chlorine, hydrogen peroxide and ozone showed two responses by zebra mussel veligers. First, veligers readily perceived the presence of oxidants (> 0.1 mg/l for chlorine and ozone) and responded by retracting the velum and ceasing swimming and feeding activities. Under these conditions, veligers are prevented from attaching to solid surfaces. Second, continuous exposure to these oxidants caused death. Complete mortality by chlorine or ozone (0.5–1 mg/l) at 18–22°C required continuous exposure of about 18 and 5 h, respectively. Either chlorine or ozone should be effective in controlling zebra mussel veligers. Hydrogen peroxide was observed to be effective in preventing attachment but only at high doses relative to chlorine and ozone.     

纯培养条件下细菌需氯量和存活性的试验研究

以埃希氏大肠杆菌和粪肠球菌作为研究对象,在纯培养条件下考察了自由氯、氯胺和二氧化氯的投加量以及细菌初始浓度对需氯量的影响.结果表明:灭活率达到99.9％时,两种细菌的需氯量均随初始菌浓度和消毒剂投加量的提高而增大,粪肠球菌的需氯量大于埃希氏大肠杆菌;投加自由氯时两种细菌的需氯量差别最大,其次是二氧化氯,氯胺的差别最小.     

Effect of free ammonia concentration on monochloramine penetration within a nitrifying biofilm and its effect on activity, viability, and recovery

Chloramine has replaced free chorine for secondary disinfection at many water utilities because of disinfection by-product (DBP) regulations. Because chloramination provides a source of ammonia, there is a potential for nitrification when using chloramines. Nitrification in drinking water distribution systems is undesirable and may result in degradation of water quality and subsequent non-compliance with existing regulations. Thus, nitrification control is a major issue and likely to become increasingly important as chloramine use increases. In this study, monochloramine penetration and its effect on nitrifying biofilm activity, viability, and recovery was investigated and evaluated using microelectrodes and confocal laser scanning microscopy (CLSM). Monochloramine was applied to nitrifying biofilm for 24 h at two different chlorine to nitrogen (Cl₂:N) mass ratios (4:1 [4.4 mg Cl₂/L] or 1:1 Cl₂:N [5.3 mg Cl₂/L]), resulting in either a low (0.23 mg N/L) or high (4.2 mg N/L) free ammonia concentration. Subsequently, these biofilm samples were allowed to recover without monochloramine and receiving 4.2 mg N/L free ammonia. Under both monochloramine application conditions, monochloramine fully penetrated into the nitrifying biofilm within 24 h. Despite this complete monochloramine penetration, complete viability loss did not occur, and both biofilm samples subsequently recovered aerobic activity when fed only free ammonia. When monochloramine was applied with a low free ammonia concentration, dissolved oxygen (DO) fully penetrated, but with a high free ammonia concentration, complete cessation of aerobic activity (i.e., oxygen utilization) did not occur and subsequent analysis indicated that oxygen consumption still remained near the substratum. During the ammonia only recovery phase, different spatial recoveries were seen in each of the samples, based on oxygen utilization. It appears that the presence of higher free ammonia concentration allowed a larger biomass to remain active during monochloramine application, particularly the organisms deeper within the biofilm, leading to faster recovery in oxygen utilization when monochloramine was removed. These results suggest that limiting the free ammonia concentration during monochloramine application will slow the onset of nitrification episodes by maintaining the biofilm biomass at a state of lower activity.