Heinz Bader

Photometric method for the determination of low concentrations of hydrogen peroxide by the peroxidase catalyzed oxidation of n n diethyl p phenylenediamine dpd

The concentration of hydrogen peroxide (H2O2) in distilled water, drinking water and in different types of surface and rain waters can be easily determined by a photometric method in which N,N-diethyl-p-phenylenediamine (DPD) is oxidized by a peroxidase catalyzed reaction. DPD is available as a commercial reagent. In all waters its oxidation occurs with a stoichiometric factor of 2.0 and leads to an absorbance (at 551 nm) of 21,000 ± 500 M−1cm−1 per H2O2. In the presence of other hydroperoxides H2O2 can be determined by comparison with a blank in which the H2O2 is destroyed with sulfite, and the sulfite residual masked with formaldehyde. The detection limit is 0.2 μg l−1 in distilled water and about 0.3 μg l−1 in most types of natural waters when 10 cm cells and a spectrophometer are used. We consider the DPD method to be a candidate for a standard method for drinking water analysis because it is easy to perform and to calibrate for absolute determinations.

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

Abstract 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.

Significance of urban and agricultural land use for biocide and pesticide dynamics in surface waters

Biocides and pesticides are designed to control the occurrence of unwanted organisms. From their point of application, these substances can be mobilized and transported to surface waters posing a threat to the aquatic environment. Historically, agricultural pesticides have received substantially more attention than biocidal compounds from urban use, despite being used in similar quantities. This study aims at improving our understanding of the influence of mixed urban and agricultural land use on the overall concentration dynamics of biocides and pesticides during rain events throughout the year. A comprehensive field study was conducted in a catchment within the Swiss plateau (25 km(2)). Four surface water sampling sites represented varying combinations of urban and agricultural sources. Additionally, the urban drainage system was studied by sampling the only wastewater treatment plant (WWTP) in the catchment, a combined sewer overflow (CSO), and a storm sewer (SS). High temporal resolution sampling was carried out during rain events from March to November 2007. The results, based on more than 600 samples analyzed for 23 substances, revealed distinct and complex concentration patterns for different compounds and sources. Five types of concentration patterns can be distinguished: a) compounds that showed elevated background concentrations throughout the year (e.g. diazinon >50 ng L(-1)), indicating a constant household source; b) compounds that showed elevated concentrations driven by rain events throughout the year (e.g. diuron 100-300 ng L(-1)), indicating a constant urban outdoor source such as facades; c) compounds with seasonal peak concentrations driven by rain events from urban and agricultural areas (e.g. mecoprop 1600 ng L(-1) and atrazine 2500 ng L(-1) respectively); d) compounds that showed unpredictably sharp peaks (e.g. atrazine 10,000 ng L(-1), diazinon 2500 ng L(-1)), which were most probably due to improper handling or even disposal of products; and finally, e) compounds that were used in high amounts but were not detected in surface waters (e.g. isothiazolinones). It can be safely concluded that in catchments of mixed land use, the contributions of biocide and pesticide inputs into surface waters from urban areas are at least as important as those from agricultural areas.

Kinetics of reactions of chlorine dioxide (OClO) in water—I. Rate constants for inorganic and organic compounds

The kinetics of chlorine dioxide consumption by a wide range of inorganic and organic compounds, including a comprehensive series of phenols, have been determined using conventional batch-type and stopped-flow methods. In all cases, the rate law was first-order in chlorine dioxide and first-order in substrate. The methods allowed us to determine second-order rate constants over a range from 10−5 to 105 M−1s−1. Measured rate constants were high for nitrite, hydrogen peroxide, ozone, iodide, iron (II), and, whenever the pH was not very low, for phenolic compounds, tertiary amines, and thiols. Bromide, ammonia, structures containing olefinic CC double bonds, aromatic hydrocarbons, primary and secondary amines, aldehydes, ketones and carbohydrates were unreactive under conditions of water treatment. For substrates that are weak acids, such as phenols, or weak bases, the effect of pH on the reaction rate showed that the rate constants for the deprotonated compounds are much higher than those for the protonated species.

Ozonation of Water: “Oxidation-Competition Values” of Different Types of Waters Used in Switzerland

Abstract In order to transfer experience from one waterwork to another, it is helpful to know (i) the spontaneous ozone requirement, (ii) the lifetime of the ozone, and (iii) the oxidation efficiency of the secondary oxidants derived from decomposed ozone (OH* radicals) in the different waters. The spontaneous ozone requirement of surface and ground waters (0.1 to 1 mg/l) and the lifetime of the ozone (30 to 2,000 sec at pH 8) can easily be measured. The effect of the secondary oxidants (OH* radicals) can best be characterized by following the elimination rate of the individual suitable referenced micropollutant as a function of the amount of ozone decomposed. This way the “Oxidation-Competition Value”, Ω, of the water can be determined. This Ω is a linear sum of the concentrations of all impurities which consume OH* radicals, multiplied by the individual “Oxidation-Competition Coefficient.” The Ω values have been determined for 40 different types of waters. For the elimination of benzene (reference solut...

Improved ammonia oxidation by ozone in the presence of bromide ion during water treatment

Ammonia oxidation by ozone proceeds more rapidly in the presence of bromide ion than in its absence. Unlike the direct ozonation of ammonia, the bromide-catalyzed process is little affected by changes in pH. A reaction scheme is proposed in which bromide is oxidized to HOBr, which then brominates ammonia to produce NH2Br. NH2Br in turn reacts with O3 to form NO3− and also to generate Br−, which thus acts as a catalyst. In accordance with the reaction model, zero-order kinetics for ammonia consumption are observed. This work points out once again the importance of Br− as a water quality parameter due to its role as a catalyst in both ozonation and chlorination processes in general.

The formation of trichloronitromethane (chloropicrin) and chloroform in a combined ozonation/chlorination treatment of drinking water

Chlorination of waters from mesotrophic Lake Zurich and eutrophic Greifensee formed about 0.4 and 2 μg 1−1 of trichloronitromethane (TCNM) respectively. Pre-ozonation increased these values to about 2 and 6 μg 1−1. The formation of chloroform was about 40 times higher than that of TCNM, but decreased somewhat, when pretreatment with ozone was performed. Posttreatment with activated carbon eliminates most TCNM but only part of the chloroform. The addition of nitrilotriacetic acid (NTA) or ethylenediamine tetraacetic acid (EDTA) complexing agents applied in detergents and other products, had only a small incremental effect on the formation of chloropicrin, which became significant only when the combined oxidation process was performed in distilled water. In contrast, the addition of triethanolamine to water greatly increased the TCNM formation when ozonation preceded chlorination of water. The possible role of NTA as a presursor for TCNM is further discussed by considering the kinetics of the reaction of ozone with NTA and its ozonolytic products, the iminodiacetic acid and glycine.

OZONE INITIATED OXIDATIONS OF SOLUTES IN WASTEWATER: A REACTION KINETIC APPROACH

Summary Some solutes present in secondary effluents are oxidized by a direct reaction of molecular ozone during an ozonation process. These oxidations are very selective. Their rates can be calculated from the concentration of ozone and the 2nd order reaction rate constants measured for specified solutes in water. Part of the ozone decomposes in water, leading to the formation of secondary oxidants. Of these, the OH. radicals easily oxidize even inert types of organic solutes, but they are non-selective and become consumed by fast reactions. The amount of decomposed ozone required to achieve a desired degree of elimination of a specified solute by OH. radicals is therefore proportional to the sum of the rates with which the sum of solutes present in the wastewater consumes OH. radicals. At elevated pH values, even carbonate ions and free ammonia contribute to this OH. radical consumption. The yield of the oxidations and its dependence on water composition can be estimated from reaction-rate constants.