Higher Chlorine Doses Research Articles

The Role of Chlorine in Oxygen Adsorption on Ag(111)

The effect of chlorine adsorption on oxygen adsorption on Ag(111) was studied with HREELS and TPD. Oxygen adsorption on Ag(111) and Ag(111) exposed to a low chlorine dose produces mainly atomic oxygen species at 170 K and room temperature. On Ag(111) exposed to a high chlorine dose and a surface with the same chlorine adsorption conditions, but followed by removal of chlorine, a molecular oxygen species was the only product of oxygen adsorption at 170 K or room temperature. The altered behavior of oxygen adsorption is due to surface defects created via chlorine adsorption. It was also found that these surface defects increase the adsorption rate of oxygen and promote the diffusion of oxygen into the subsurface.

The combined effects of chlorine and ammonia on litter breakdown in outdoor experimental streams

The response of Potamogeton crispus L. breakdown to controlled doses of different levels of chlorine and chlorine + ammonia was investigated over two years in outdoor experimental streams. In 1985, downstream riffles of 2 streams were dosed (observed in-stream concentrations) at ca. 10 µg/L Total Residual Chlorine (TRC), one stream at 64 µg/L TRC and one stream at 230 µg/L TRC. Two control streams were not dosed and the upstream riffles of each stream served as within stream controls. In 1986, the downstream riffle of one stream was dosed at 70 µg/L TRC and a second stream was dosed at 200 µg/L TRC. Four streams were also dosed with 2.5 mg/L NH3-N: one stream with no chlorine, one stream with ca. 10 µg/L TRC, one with 56 µg/L TRC, and one with 150 µg/L TRC. A seventh stream was dosed for 2 h at 2000 µg/L TRC and 2.5 mg/L ammonia and then allowed to recover (recovery stream). Each year, litter decomposition (degree day k values) was measured during two 35 day trials (Jun–Jul and Aug–Sep). In 1985, when streams were dosed with chlorine alone, decomposition was significantly reduced with the high (230 µg/L TRC) chlorine dose. Downstream decomposition was 27% (Jun–Jul) and 59% (Aug–Sep) of the upstream (control) rate. No other chlorine effects were found during this period. In Jun–Jul 1986, there was significantly lower decomposition in the downstream dosed sites of the 200 µg/L TRC alone stream, the 146 µg/L TRC + ammonia stream and the recovery stream; downstream decay rates were (respectively) 56%, 42% and 64% of the upstream control sites. No other up-down pairs were different in July 1986. In Aug–Sep, all three streams with chlorine + ammonia (6, 56 and 146 µg/L TRC + 2,5 mg/L ammonia) and the 70 µg/L TRC alone stream had significantly lower decomposition rates in the downstream dosed sites. For these streams, downstream decay rates ranged from 46% (high chlorine + ammonia) to 73% (low chlorine + ammonia) of the upstream control rates. No other up-down pairs were different during this trial. Up and downstream sites of the stream dosed with 2.5 mg/L ammonia alone were nearly identical for both trials (< 3% difference). These results indicate that TRC at less than 250 µg/L can significantly reduce litter decomposition and strongly suggest that addition of ammonia to chlorinated water can increase the toxic effect of chlorine.

Influence of chlorination pH and chlorine dose on the formation of mutagenic activity and the strong bacterial mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-5(2H)-furanone (MX) in water

Samples from two Dutch raw water sources were chlorinated in the laboratory at different pH:s and chlorine doses, and were analysed for mutagenic activity and the mutagenic compound 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX). Chlorination produced mutagenic activity as well as MX in both waters. The formation of MX was favoured by acidic reaction conditions and high chlorine doses, but in waters treated with excess chlorine at pH 9, no MX was detected. The mutagenicity was approximately on the same level after chlorination of both water types but the MX concentration was significantly higher in the water containing mainly humic material. MX was found to be quantitatively extracted from acidified waters by the XAD resin adsorption technique.

Effects of chronic chlorine exposure on litter processing in outdoor experimental streams

SUMMARY 1. The effects of chlorine on litter (Potamogeton crispusL.) processing were examined using six outdoor experimental streams. Downstream portions of two streams were dosed at c. 10 μg l−1 Total Residual Chlorine (TRC), one stream at 64 μgl1, and one stream at 230μg l−1. Two control streams were not dosed; upstream riffles of each stream served as instream controls.2. Two 35 day litter breakdown (per cent AFDW remaining) experiments indicated significantly lower decay rates in the high dose riffle. No other concentration of chlorine significantly affected decay rate.3. A third experiment, conducted in medium and high dose streams, indicated that high dose chlorine exposure reduced litter decomposition rates significantly, and reduced microbial colonization, microbial electron transport system activity, and microbial litter decomposition after 4 days but not after 11 days of exposure. The number of amphipod shredders colonizing litter bags was also reduced significantly with high chlorine dose.4. A fourth experiment, after dosing was terminated, provided direct evidence that amphipod shredders were important in facilitating litter decomposition: litter bags stocked with amphipods had significantly higher decomposition rates than bags which excluded shredders.5. Overall results indicate that the high dose (c. 230 μgl−1 TRC) of chlorine reduced litter processing rates partly by reducing initial microbial conditioning, but primarily by reducing the colonization of amphipod shredders.

Chlorine utilization during trihalomethane formation in the presence of ammonia and bromide

The chlorination of humic substances in the presence of ammonia and bromide and the resultant formation of trihalomethanes (THM) are described. The presence of ammonia substantially reduced but did not eliminate THM production during the chlorination of waters containing humic substances. The presence of bromide ion in waters containing humic substances leads to increased THM formation, both in the presence and in the absence of ammonia. In waters containing ammonia, bromide, and humic substances, brominated haloforms can form upon chlorination. Brominated species comprise a larger portion of the total THMs at higher chlorine doses within the free chlorine region of the breakpoint curve than at lower dose in the subbreakpoint region. Although the THM formation reaction is slow and may not be complete even after 1 week of reaction time, the initial rate of formation is competitive with the relatively rapid reactions of bromide oxidation and chloramine formation. After free chlorine is converted to chloramines, THM production should theoretically cease. THMs will form in parallel with chloramine formation. This behavior has important implications for water utilities that use a raw water source containing low but significant levels of ammonia such as the Biscayne Aquifer, or are considering chloramine disinfection asmore » a THM control strategy.« less

Chlorine leaching and replenishing studies on a bimetallic reforming catalyst

Factors which influence the loss and retention of chlorine on an industrial bimetallic reforming catalyst have been studied. Temperature showed a marked effect on chlorine loss during calcination and reduction, the loss being greater during reduction than during calcination. Activation energies for chlorine loss were 6 Kcal mol −1 for calcination and 2.6 Kcal mol −1 for reduction in the temperature range 470–550° C. Increase in feed moisture content during reforming enhanced the loss of chlorine significantly. The following correlation between chlorine loss and feed moisture content was obtained: Chlorine loss (wt %) = 2.8 (moisture in feed, ppm) 0.45 Depletion of chlorine from the catalyst resulted in considerable decrease in the aromatization activity. Addition of chlorine to the moisture containing feed in different proportions showed that an optimum level of chlorine should be maintained in the feed for a given moisture level (e.g., 20 ppm Cl for 100 ppm H 2O) in order to achieve a balanced product pattern. Higher chlorine levels resulted in considerable yield loss, indicating enhancement of hydrocracking reactions. The catalyst's chlorine content has been correlated with feed moisture and chlorine levels by: Chlorine in catalyst (wt %) = 0.438 (Cl in feed, ppm) 0.17 (moisture in feed,ppm) 0.1 Carbon deposition on the catalyst was found to be minimal with 0.9 to 1.1% chlorine in the catalyst. Addition of chlorine to the moisture containing feed was found to balance the effect of moisture on support sintering and stabilize the support surface area. The effect of chlorine addition on reactivating a reforming catalyst deactivated by moisture was also studied, using continuous and pulse modes of chlorination. The lost activity of the catalyst was fully recovered by both modes of chlorine injection. However, for pulse chlorination, the reformate yield suddenly dropped immediately after chlorine injection. As the reforming continued, reformate yield and aromatics produced on feed basis increased progressively, indicating suppression of hydrocracking activity and increase of aromatization (or dehydrocyclization) activity. Higher chlorine dosage however, resulted in considerable yield loss in both modes. Addition of chlorine in successive pulses resulted in recovering and maintaining catalyst activity close to the original level.

Epidemiologic Study of Drinking Water Chlorination and Wisconsin Female Cancer Mortality&lt;xref ref-type="fn" rid="fn2"&gt;2&lt;/xref&gt;

The association between gastrointestinal, urinary tract, brain, lung, and breast cancer mortality and drinking water trihalomethane exposure, as estimated by average daily chlorine dosage of water source 20 years past, was investigated for Wisconsin white females by use of a death certificate-based case-control study design. A total of 8,029 cancer deaths and 8,029 controls (noncancer deaths) matched on county of residence, year of death, and age were taken from mortality records of 28 counties for the years 1972-77. Data on characteristics and treatment of municipal water supplied to the residences of cases and controls were obtained from questionnaires sent to the water superintendents of the 202 waterworks associated with the sample. By the use of logistic regression analysis, odds ratios for site-specific cancer death associated with high, medium, and low chlorine-dosed water as compared to unchlorinated water exposure were determined; the control variables were urbanicity, marital status, and occupation. With the exception of cancer of the colon, no anatomic cancer site was significantly associated with any chlorine dose exposure category. For colon cancer, odds ratios of 1.51 [95% confidence interval (Cl) = 1.06-2.14], 1.53 (95% Cl=1.08-2.00, and 1.53 (95% Cl-1.11-2.11) were obtained for high-, medium-, and low-dose chlorination, respectively (P less than or equal to 0.02). For colon cancer cases and controls exposed to water sources affected by rural runoff, odds ratios of 3.30 (95% Cl=1.45-7.47), 3.60 (95% Cl=1.57-8.26), and 2.74 (95% Cl=1.10-6.88) were observed for high, medium, and low chlorine dosages 20 years past (P less than or equal to 0.025).

Optimization of Chlorine Disinfection Efficiency

In order to show that savings in chlorine can be achieved by improved process design, parallel chlorination studies were conducted in an optimized chlorination pilot plant and each full-scale system at six different sewage treatment plants. Concurrent flow-through fish bioassays were also conducted at each location. At all test sites the optimized pilot plant used significantly lower chlorine dosages and residuals to achieve the same degree of disinfection, and its effluent was markedly less toxic than the full-scale effluents. The reasons for the good pilot plant results were variously good initial mixing, better chlorine control, plug flow contact, and better operation. Nitrified effluents required relatively high chlorine dosages for adequate disinfection. In most cases the disinfection efficiency could be expressed by the product of chlorine residual and contact time. The degree of bacterial kill obtained during initial mixing was a function of chlorine residual. Sulfur dioxide removed all chlorine-induced toxicity from the effluents.

Mechanism of disinfection: Effect of chlorine on cell membrane functions

To elucidate the mechanism of disinfection by chlorine, its effects on some vital properties associated with cell membrane of Escherchia coli were studied. There was no significant change in Zeta potential at bactericidal doses of chlorine. Treatment with chlorine induced the leakage of macromolecules from the cells indicating the permeability changes of the membrane. Proteins and RNA were detected in the supernatant when the cells were treated with chlorine dose of 1.5 mg 1 −1 (100 μg Cl mg −1 N). The presence of DNA was observed only at high chlorine doses. The studies on oxidative phosphorylation of cell free extract indicated the complete cessation of phosphate uptake at a dose of 0.4 mg 1 −1 (30 μg Cl mg −1 N). There was about 70% decrease in the oxygen uptake corresponding to chlorine dose of 0.8 mg 1 −1.

Schistosomiasis and the Chlorination of Sewage Effluent

Summary A study was undertaken in Puerto Rico to determine the effect of chlorine at different dosage levels on the hatched and unhatched miracidium of Schistosoma mansoni. Results indicate that in sewage effluent with a BOD between 25 and 45 mg per liter, the free-swimming miracidium is killed in 1 or 2 minutes when the 30-minute chlorine residual is 0.2 mg per liter. From three experiments each employing 13 dosage levels to secondary sewage effluent (pH range 7.0–9.0, BOD range 20–48 mg per liter), the highest chlorine dosage tolerated for 15 minutes by the unhatched miracidium was an initial 2.0 mg per liter and a 15-minute residual of 0.9 mg per liter. No unhatched miracidia in effluent survived an initial dosage of 2.4 mg per liter with a 15-minute residual of 1.5 mg per liter or above. Primary sewage treatment effluent with a higher BOD (115 mg per liter) required a higher chlorine dosage (11.3 mg per liter initial, 8.5 mg per liter residual at 15 minutes). The writer believes that chlorination at a level sufficiently high to give a 15-minute residual of at least 2.5 mg per liter would be of value in ridding sewage effluent in Puerto Rico of viable S. mansoni eggs and miracidia.

THE EFFECT OF UNTREATED AND CHLORINATED WATER ON THE KEEPING QUALITY OF BUTTER

SummaryThe investigation had as its principal objects, determination of the microbiological effectiveness of the chlorination of polluted water supplies used for buttermaking, the influence of high chlorine dosages on butter flavour and an examination of the reproducibility of butter grading by subjective methods.A preliminary trial in which pasteurized sweet cream was made into butter using polluted as well as chlorinated water, revealed that there were marked differences in the condition and quality of the finished product. Butter washed with contaminated water developed rancidity within twenty‐one days at 37 to 41 °F. whereas water from the same source, but which contained 5 p. p.m. residual chlorine, resulted in butter which retained a pleasing flavour and aroma for six weeks.In the main experiment, six duplicate lots of unsalted butter were made from ripened cream, using treated and untreated water from the same source, with identical buttermaking methods. The untreated water contained large numbers of psychrophilic bacteria, including Pseudomonas putrefaciens. These organisms grew actively in unsalted butter held at 45 to 50°F. Chlorination of the water with varying dosages of from 10 to 200 p. p.m. available chlorine, sixteen hours before use, resulted in practically a complete destruction of the spoilage organisms. The cream used during the main experiment was ripened at 40 to 50°F. for two days after pasteurizing by the H. T.S. T. method before churning. On microbiological examination, the butter produced from this cream was found to contain large numbers of spoilage organisms, and became rancid within four weeks when stored at 45 to 50°F. However, the microbiological results indicate the superior quality of those butters made with chlorinated water.A consensus of the grading results obtained, substantiates the anticipated superior quality of butter made using chlorinated water, compared with that made with an impure supply. No chlorine taint was detected in the butter, although water containing as much as 100 to 200 p. p.m. residual chlorine had been used in preparing two of the samples. The arbitrary nature of subjective grading is reflected in the differing conclusions arrived at by individual members of the graders' panel.

Proposed Plan for Ammonia‐Chlorine Treatment in Chicago

To meet the lake pollution situation, Chicago is preparing to change the method of treating the water for the south side from chlorination at the three pumping stations to the use of ammonia and chlorine at the 68th Street and Dunne cribs. The principal reason for this new policy is because pollution of the lake in the vicinity of these cribs has increased to such an extent that the chlorination equipment at the pumping stations is taxed at times almost to capacity to provide sufficient chlorine for effective disinfection. The bacterial pollution of the southern end of Lake Michigan in the vicinity of these cribs increased from 1927 to 1930, as shown in figure 1. Since 1931 there has been a slight drop in bacterial pollution, due to the decline in industrial activities in the Calumet region, but the industrial waste pollution has in the last two years become a serious problem. The industrial wastes, principally those from the oil refineries, caused a prolonged period of offensive taste in Chicago water late in December, 1932 and in the early part of January, 1933. During some of these taste periods the water had the property of absorbing large quantities of chlorine, necessitating high chlorine dosages in order to obtain sufficient residual chlorine for effective disinfection. It is expected that pollution will increase to even a greater extent in a few years when a decree of the U. S. Supreme Court becomes effective which requires that diversion from Lake Michigan into the Drainage Canal be reduced from 6500 to 5000 c.f.s. on December 31, 1935 and to 1500 c.f.s. on December 31, 1938. When these reductions in diversion become effective frequent reversals of the Calumet and Chicago rivers may be expected, discharging pollution into the lake waters. At most of the Chicago pumping stations the water pumped into the distribution system reaches the first consumers only a few minutes