Rate constants of reactions of ozone with organic and inorganic compounds in water—III. Inorganic compounds and radicals

Second-order rate constants for reactions of ozone with 40 inorganic aqueous solutes are reported. Included are compounds of sulfur (e.g. H₂S, H₂SO₃, HOCH₂SO₃H), chlorine (e.g. Cl⁻, HOCl, NH₂Cl, HClO₂, ClO₂), bromine (e.g. Br⁻, HOBr), nitrogen (e.g. NH₃, NH₂OH, N₂O, HNO₂) and oxygen (e.g. H₂O₂), as well as free radicals (e.g. O₂⁻, OH^•). Most of these compounds exhibit an increase in rate constant with increasing pH corresponding to their degree of dissociation. Rate constants are based on ozone consumption rates measured by conventional batch-type or continuous-flow methods (10⁻³-10⁺⁶ M⁻¹ s⁻¹ range) and determinations of stoichiometric factors. Also listed are data determined by pulse-irradiation techniques using kinetic spectroscopy (10¹⁰ M⁻¹ s⁻¹ range). Additional literature data are reviewed for completeness. Results are discussed with respect to water treatment and environmental processes.     

Ozonation of water containing chlorine or chloramines. Reaction products and kinetics

Ozone reacts with free aqueous chlorine when present as hypochlorite ion (OCl⁻) with a second order rate constant of 120 ± 15 M⁻¹ s⁻¹ at 20°C. About 77% of the chlorine reacts to produce Cl⁻ and 23% is oxidized to ClO⁻₃. No ClO⁻₄ is formed. Conversion of chlorine to monochloramine reduces the ozone reaction rate to 26 ± 4 M⁻¹ s⁻¹, independent of pH, NH₂Cl is transformed quantitatively to NO⁻₃ and Cl⁻ by O₃. Rate data for other chloramines are also presented. The direct reaction of ozone with chlorine accounts for a significant amount of the chlorine and ozone demand found when the two oxidants are used in combination under water works conditions.     

Methyl bromide in surface drinking waters: Gas-chromatographic determination by the headspace technique

A sensitive method for the gas-chromatographic determination of methy bromide in surface drinking waters is reported. The analytical principle is based on the conversion of methyl bromide into methyl iodide by reaction with sodium iodide. Reaction parameters (amount of sodium iodide added, temperature, reaction time and salinity) are reported to provide a simple, precise and sensitive analytical method with a CH₃Br detection threshold of approx. 5 × 10⁻³μgl⁻¹.     

Effects of ozonation and ultraviolet irradiation on biodegradability of oil shale wastewater organic solutes

Ozonation and u.v. irradiation were evaluated for their abilities to (1) mineralize organic solutes that remained in a biooxidized oil shale process wastewater and (2) effect sufficient structural modification of the remaining biorefractory organic solutes to promote secondary biooxidation. Full-spectrum u.v. radiation (5 h, total dose of 10.2 × 10⁶ J l⁻¹) failed to mineralize or effect the biooxidation of any of the biorefractory carbon. Although ozonation (5 h, total dose of 1.6 g O₃ l⁻¹) directly mineralized only 8% of the biorefractory carbon, it enhanced secondary biooxidation; 26% of the refractory carbon was mineralized by an acclimated microbial inoculum. When u.v. irradiation and ozonation were combined simultaneously, a synergistic effect was observed; 3 h of combined treatment (5.9 × 10⁶ J l⁻¹ and 0.83 g O₃ l⁻¹) was as effective a pretreatment for secondary biooxidation as was 5 h of ozonation. Sequential application of primary biooxidation, 6 h of combined u.v./ozonation, and secondary biooxidation removed only 59% of the dissolved organic carbon; total reduction of 87% was achieved by using a culture in the secondary biooxidation step that was specifically adapted to this oxidized water. Each time-course sample was analyzed for the distribution of polar and nonpolar organic solutes. In general, ozonation and combined u.v./ozonation mineralized carbon from the nonpolar fraction; biooxidation of formerly refractory carbon was promoted by oxidation of nonpolar carbon to yield more polar or lower-molecular-weight species.     

Bromide concentration in Swedish precipitation, surface and ground waters

The occurrence of bromide in precipitation, surface and ground waters in Sweden has been investigated (300 samples). The concentration of bromide in precipitation is 0.05–0.15 μM in the south and <0.05 μM in the north of Sweden. The concentrations of bromide and chloride are well correlated. For river water the same areal distribution pattern as for precipitation is found, but the concentrations are 2–4 times higher. The molar ratio Br/Cl is 1 × 10⁻³ which is lower than that for sea water (1.54 × 10⁻³) and, most likely, also lower than for precipitation. A detailed study of Lake Mälaren has been made. The north-eastern feeder streams, passing an area of post-glacial clay, showed unusually high bromide concentrations (0.3–3 μM) and Br/Cl quotients (2 × 10⁻³-8 × 10⁻³). No correlation between the concentrations of bromide and chloride was found. Rough calculations indicate that fertilizers and chemicals added to the fields could only contribute a minor fraction of the bromide found. Analysis of 18 ground water samples indicated increased bromide levels as compared to surface waters.     

Oxidation of sulfhydryl groups by monochloramine

In recent years there has been an increased used of monochloramine (NH₂Cl) for water disinfection because of its low trihalomethane formation potential. Monochloramine is also the predominant disinfectant upon chlorination of wastewater effluents. In an effort to more clearly understand the disinfectant's mode of action in inactivating microorganisms, a study was undertaken to evaluate the compound's reactions with sulfhydryl (−SH) groups. The extent of oxidation of these groups was dependent upon the molar ratio of −SH to NH₂Cl. When this ratio was >2:1, the reaction was reversible and ceased at disulfide formation. However, at a ratio of < 2:1, the reaction proceeded irreversibly beyond the disulfide; this reaction continued in the presence of a monochloramine residual. Not all −SH groups in Escherichia coli B were available for reaction. Masking of these groups within bacterial proteins prevented their complete oxidation at monochloramine doses as high as 100 mg 1⁻¹. The extent to which sulfhydryls are oxidized in bacteria may play an important role in further research on microbial reactivation.     

Ozonation of pyrene in aqueous solution

The reaction of pyrene with ozone was studied in aqueous solution at low (10–200 μg l⁻¹) substrate concentration and with ozone concentrations (5 mg l⁻¹) approximating to those used in potable water treatment. Degree of reaction and the formation of polyaromatic/aromatic reaction products were assessed using a technique of solvent extraction and derivatisation with gas chromatographic (GC), gas chromatographic-mass spectrometric (GC-MS), high performance liquid chromatographic (HPLC) and u.v. spectrometric analysis of extracts. A freeze drying/derivatisation technique with GC and GC-MS analysis was employed for the isolation/identification of short chain polar aliphatic reaction products. Substantial destruction of pyrene was recorded within 1 min of reaction with ozone. Polyaromatic/aromatic compounds did not persist; reaction products are likely to be short chain polar aliphatic compounds. Products of this type were isolated but not identified in the study.     

Water quality criteria for European freshwater fish: Report on ammonia and inland fisheries

In establishing water quality criteria for European inland fisheries, the effect of ammonia is an important factor to be considered. Sewage effluent, effluents from certain industries and from agriculture are common sources of ammonia in water.The harmful effects of ammonia on fish are related to the pH value and the temperature of the water due to the fact that only the un-ionized fraction of ammonia is poisonous. The un-ionized fraction increases with rising pH value, and with rising temperature.Fish differ slightly in their tolerance to ammonia depending on species. The difference in tolerance being more significant for short periods of exposure. The difference in tolerance is, however, not great enough to justify different criteria for different species.The lowest toxic concentration found for salmonids is 0·2 mg NH₃ 1⁻¹ (un-ionized), but other adverse effects caused by prolonged exposure are only absent at concentrations lower than 0·025 mg NH₃ 1⁻¹ (un-ionized). Concentrations of total ammonia which contain this amount of un-ionized ammonia vary from 19·6 mg 1⁻¹ (pH 7·0, 5°C) to 0·12 mg 1⁻¹ (pH 8·5, 30°C).The criterion should not be applied to temperatures below 5°C or to pH values above 8·5 when other factors have to be taken into consideration.     

Biodegradability of ozonation products as a function of COD and DOC elimination by the example of humic acids

Ozone pretreatment studies of humic acids were conducted to evaluate the effects of ozonation on the biodegradability of the oxidation products as a function of COD-, DOC-elimination, decrease of u.v.-absorbance and ozone consumption. A 50–60% decrease of the COD-value and a 30% decrease of the DOC-value lead to biodegradable products (BOD₅/COD = 0.4) in most cases independent of the pH-value and the initial concentration. To reach these results 3.4–4 mg ozone are consumed per mg initial DOC. With this ozone consumption complete decolorization of the solutions is achieved and the value of u.v./DOC decreases from 4 to 0.8 m² g⁻¹.     

Investigations on natural Hungarian zeolite for ammonia removal

Use of natural zeolites deposited at Tokaj mountain, Hungary, for ammonia removal from synthetic and municipal wastewaters was studied. The optimal ion exchange conditions found were as follows: Na-form clinoptilolite, 0.5–1.0 mm in particle size and about 5–7 BV h⁻¹ loading rate. Using synthetic wastewater in the column of 9.5 cm i.d. × 92 cm, about 4.50 mg NH₃-N g⁻¹ clinoptilolite ammonia breakthrough capacity was achieved. For regeneration of the ion exchange bed, 10–20 BV of regenerant were necessary to remove the 98–99%, of ammonia with flow rate of a 5–7 BV h⁻¹.     

Residual oxidant decay and bromate formation in chlorinated and ozonated sea-water

Oxidant decay and bromate formation were studied under light and dark conditions in 5.15 and 30‰ artificial sea-water and 5‰ natural estuarine water following ozonation or chlorination. For both oxidants, light exposure accelerated the residual oxidant decay rates which were inversely related to sample salinities in artificial sea-water. Significant quantities of bromate were produced in light-exposed, chlorinated samples with an initial residual oxidant concentration of 70 μM (5mg l⁻¹ as total residual chlorine) but not at lower residual oxidant concentrations or in non-photolyzed samples. No bromate was formed in any of the chlorinated natural estuarine water samples. Bromate production was much greater in ozonated samples than in chlorinated ones and was formed in two distinct stages. Photolytic bromate formation decreased with increasing bromide concentration in both chlorinated and ozonated artificial sea-water. Bromate formation was completely inhibited in the presence of NH₃-N and estuarine sediment. The same free radical mechanism is proposed for both ozone-induced and photolytic-induced bromate formation in artificial sea-water.     

Ozonation of seawater: preliminary observations on the oxidation of bromide, chloride and organic carbon

Exhaustive ozonation of surface seawater results in a rapid oxidation of Br⁻¹ to BrO⁻¹, and there is evidence for the transitory formation of CIO^-. The dissolved organic carbon is 25% oxidized in 1 h under similar conditions. The possible formation of other oxidation products is discussed.     

Factors affecting nutrient loads in some Iowa streams

The export and concentration of inorganic nitrogen and total phosphorus from 34 watersheds in a northwestern Iowa lake district were measured during March 1971–August 1973. Annual nutrient losses were approximately 0.35 kg ha⁻¹ P. 6.7 kg ha⁻¹ NO₃-N, and 1.0 kg ha⁻¹ NH₃-N. A statistical analysis of the relationship between land-use and plant nutrients was used to determine differences among streams. Animal units in feedlots were significantly correlated with phosphorus and ammonia nitrogen (mg l⁻¹ and kg ha⁻¹ yr⁻¹). Nitrate nitrogen was negatively correlated with the percentage of watershed in marshland. Tile drainage and surface runoff from grasslands, feedlots, cornfields, and soybean fields were analyzed for nitrogen and phosphorus in spring 1974: mean values are given.     

Utilisation de la clinoptilolite en potabilisation des eaux—elimination de l'ion NH4

The objective of this study is to develop a technique to remove ammonium ion from water intended for potable purposes. An ion exchange method is used with a selective ion exchanger, a natural cation zeolite, clinoptilolite. Glass columns (Fig. 1) are used for laboratory experiments. These experiments show that the NH₄⁺ exchange capacity is very small compared to its total capacity 2.17 meq g⁻¹; its value depends essentially on the NH₄⁺ initial concentration and less on the Ca²⁺ concentration in the influent water. Figure 3 illustrates the practical exchange capacity relative to the initial concentration of ammonium ion for a soft water (Ca²⁺ = 35–50 mg l⁻¹). We were particularly interested in waters weak in ammonium ion concentration (NH₄⁺ = 1–3 mg l⁻¹). In this case and for 1 and 2 mg l⁻¹ NH₄⁺ concentration in water, the practical capacity is only 0.06 and 0.108 meq g⁻¹ respectively. The leakage is smaller than the ECC limit (European Community Council) for drinking waters (NH₄⁺ 0.5 mg l⁻¹) and the treated volume of water to breakthrough, defined at 0.5 mg l⁻¹ of NH₄⁺, is 720 BV (BV = bed volume) in both cases.In another way Fig. 6 shows that hard waters (due to Ca²⁺ ions) are more difficult to treat than soft waters. The practical capacity is smaller than before and the NH₄⁺-leakage is greater. To lessen NH₄⁺-leakage to less than 0.5 mg l⁻¹ for soft waters down-flow and up-flow, regeneration is used. Figure 7 shows that up-flow regeneration is more attractive than down-flow regeneration.Cycle reproducibility (Figs 4 and 5) shows that the regeneration conditions satisfied our requirements: in this case, the salt consumption is 180 eq of salt per eq of NH₄⁺ eliminated. This prompted us to try to reuse the regenerant (with NH₄⁺ ion). An increase of NH₄⁺-leakage is noticed in the presence of an NH₄⁺-residual in the regenerant. This increase is more significant with down-flow regeneration.After these laboratory experiments, we carried out a semi-industrial pilot-plant. Our objective was first to verify the laboratory results and secondly to study clinoptilolite behaviour relative to the time it was used. Two plexiglass columns comprise the pilot-plant shown in Fig. 9; soft water is used for these experiments. The first column is regenerated with fresh salt solution. The cycles obtained, considering their initial NH₄⁺-concentration, are reproduced in Fig. 10. For 2 mg l⁻¹ NH₄⁺ in the influent water, the leakage is about 0.2 mg l⁻¹ and the treated volume to breakthrough (0.5 mg l⁻¹ of NH₄⁺) is about 750 BV. The second column is regenerated with a recycled solution. The quality of the cycles decreases with the number of reuse of the regenerant as shown in Fig. 11. Nevertheless, it is interesting to note that after 3 reuses, the performance decrease is only 25% and the leakage, although it increases is smaller than 0.5 mg l⁻¹.Pilot results allowed us to propose a treatment of 30,000 m³ day⁻¹; the cost per cubic meter water treated, relative to NH₄⁺-removal, is about 0.165 FF (0.033 US $) for a plant and 0.77 FF (0.014 US $) for the same plant at the seaside. Using two serial columns decreased the cost by about 40–50%.     

Nitrification kinetics in activated sludge at various temperatures and dissolved oxygen concentrations

Activated sludge from a domestic sewage works was enriched with nitrifying bacteria by running a laboratory fermenter on ammonia-supplemented sewage. This enriched culture was used to determine respirometrically the kinetics of microbial nitrification. It was demonstrated that the reaction fits the Michaelis-Menten model for temperatures from 10 to 35°C, having a temperature optimum at 15°C (K₃ 0.72 mg 1⁻¹ NH₃). Nitrification is unaffected by high dissolved oxygen concentration 38 mg 1⁻¹ O₂ at 30°C) after acclimatisation. Nitrite concentrations > 20 mg 1⁻¹ are inhibitory to the reaction.     

An automated procedure for the determination of total Kjeldahl nitrogen

A procedure for the determination of total Kjeldahl nitrogen in surface fresh waters and organic wastes is described. Organic nitrogen compounds are converted to ammonium sulphate by a catalytic (red mercuric oxide) acid-sulphate digestion. The digest time is 3 h and allows for a maximum of 36 samples, 2 blanks and 2 standards to be processed simultaneously. There is no pH adjustment required following the digestion. Calibration curves covering the ranges (i) 0.5–100 μg NH₃---Nl⁻¹ and (ii) 10–1000 μg NH₃---Nl⁻¹ were linear within ±2%. The detection limit of the method is 0.5 μg TKNl⁻¹. The concentration range of TKN for which the method is suitable is 0.5 μg Nl⁻¹–40 mg Nl⁻¹. The method displayed a high tolerance to interferences from copper, iron, mercury and hardness. Digest procedure gave a high recovery and reproductibility over a wide range of nitrogen compounds tested.     

Influence of high NaCl and NH4Cl salt levels on methanogenic associations

The effect of high levels of NaCl and NH₄Cl on the activity and attachment of methanogenic associations in semi-continuous flow-through reactor systems has been evaluated. Two well-functioning reactors received shock concentrations of NaCl and NH₄Cl while two other reactors were adapted to increasing levels of the salts during a period of 45 days. The methanogenic associations, grown on a medium containing mainly acetate and ethanol, were found to be more resistant to NaCl and NH₄Cl than previously reported. Initial inhibition occurred at shock treatments of 30 gl⁻¹ for both salts. The reactors which were gradually exposed to increasing levels of the salts, adapted well and their tolerance levels surpassed those of the non-trained counterparts. Initial inhibition and fifty percent inhibition was observed at 65 and 95 gl⁻¹ respectively for adaptation to NaCl. Initial inhibition for the reactor adapting to NH₄Cl occurred at 30 gl⁻¹ and a 50% inhibition was observed at 45 gl⁻¹ of NH₄Cl. For the reactors receiving NH₄Cl, the free ammonia-N should be kept below a concentration of 80–100 mg l⁻¹ for optimal performance. The bacterial populations in the reactors consisted mostly out of Methanosarcina (> 99% of the biomass)     

Simultaneous nitrification and denitrification in a CEM (cation exchange membrane)-bounded two chamber system

A novel process was developed to induce a simultaneous oxidation of ammonia and denitrification in a single system consisting of two chambers separated by a cation exchange membrane. One was an anoxic chamber and the other was an aerobic chamber. The maximum mass flux via the membrane was calculated as 0.83 mg NH₄⁺-N/m² s in a batch test when the initial concentration of NH₄⁺ was 700 mg N/L. And it was observed that NO₃⁻ and NO₂⁻ moved via the membrane in a reverse direction when NH₄⁺ was transported. When the system was operated in a continuous mode by feeding a wastewater containing glucose and NH₄⁺, it was observed that soluble chemical oxygen demand and NH₄⁺ were simultaneously removed showing 99% and 71  86% of efficiency, respectively. Denitrification occurred in the anoxic chamber and nitrification was carried out in the aerobic chamber.     

Mechanism and kinetics of sulfamethoxazole photocatalytic ozonation in water

The photocatalytic ozonation of sulfamethoxazole (SMT) has been studied in water under different experimental conditions. The effect of gas flow rate, initial concentration of ozone, SMT and TiO₂ has been investigated to establish the importance of mass transfer and chemical reaction. Under the conditions investigated the process is chemically controlled. Both, SMT and TOC kinetics have been considered. Fast and slow kinetic regime of ozone reactions have been observed for SMT and TOC oxidation, respectively. Application of different inhibitors allows for the establishment of reaction mechanism involving direct ozonation, direct photolysis, hydroxyl radical reactions and photocatalytic reactions. Rate constants of the direct reaction between ozone and protonated, non-protonated and anionic SMT species have been determined to be 1.71 × 10⁵, 3.24 × 10⁵ and 4.18 × 10⁵ M⁻¹ s⁻¹, respectively. SMT quantum yield at 313 nm was found to be 0.012 moles per Einstein at pH 5 and 0.003 moles per Einstein at pHs 7 and 9. Main contributions to SMT removal were direct ozone reaction, positive hole oxidation and hydroxyl radical reactions. For TOC removal, main contributions were due to positive hole oxidation and hydroxyl radical reactions.     

An improved hydrazine reduction method for the automated determination of low nitrate levels in freshwater

An automated nitrate determination is described in which nitrate is reduced to nitrite with hydrazine sulphate under alkaline conditions in the presence of Cu²⁺ and Zn²⁺. Interferances encountered in natural water samples were eliminated by the addition of Zn²⁺ to the Cu²⁺ catalyst solution.The method is suitable for the determination of low NO₃−N concentrations and compares favourably with the manual copperised cadmium technique for freshwater samples containing 10–800 mg m⁻³ NO₃−N. The method is also linear at nitrate concentrations below 10 mg N m⁻³. The standard deviations (S.D.) of blanks and of samples containing 2 mg NO₃−N m⁻³ were 0.013 and 0.06 mg N m⁻³ respectively at an analysis rate of 30 samples h⁻¹.