Catalytic destruction of chloramine to nitrogen using chlorination and activated carbon--case study.

The paper presents the results of laboratory and pilot studies on the removal of chloramine from potable water using chlorination with a less-than-breakpoint dosage of chlorine, followed by treatment with catalytic activated carbon. The effect of the chlorine-to-nitrogen ratio, temperature, and carbon contact time were investigated to optimize conditions for chloramines removal and minimize the production of ammonia. Results demonstrated that prechlorination of water, followed by treatment with catalytic activated carbon, can degrade monochloramine to nitrogen gas as a main product. For all chlorine-to-ammonia ratios studied, the observed rates of monochloramine removal were higher at a temperature of 20 degrees C than they were at 5 degrees C. Generation of ammonia was slightly higher at the lower temperature. However, at both temperatures, practically all monochloramine was destroyed, and only insignificant amounts of ammonia were formed when a chlorine-to-ammonia ratio of 7:1 was applied. The described method is simple and cost-effective, because it eliminates the requirement of removal of ammonia, typically formed during the treatment of chloramines with activated carbon.

Application of aerobic respirometry: studies on the impact of humate on biological treatment of municipal sewage.

This paper describes an application of aerobic respirometry to investigate the influence of humic matter (humate) on biological processes in dilution water and in municipal sewage. Standard product PolySeed, a consortium of bacteria considered to be representative of those found in an activated sludge, was used as a source of biomass. The results indicate that aerobic respirometry is a simple and convenient method for studies of biological processes. It was observed that an addition of humate at doses up to 2000 mg 1(-1) stimulated biological processes both in dilution water and in sewage. Also, it was found that humate is effective in suppressing an inhibitory effect of phenol and copper on the biomass. The results of the studies suggest than the application of humate has great potential in wastewater treatment, as it can serve as a source of additives, stimulating biological activity and removing toxic inhibitors of biological processes.

Respirometric studies on the impact of humic substances on the activated sludge treatment: mitigation of an inhibitory effect caused by diesel oil.

This paper describes the results of aerobic respirometric studies on the application of humic substances (humate) to mitigate an inhibitory effect of petroleum hydrocarbons (diesel oil) on the returned activated sludge (RAS) in sewage from a municipal treatment plant. Initial results of the respirometric tests and non-linear regression analysis showed that diesel oil had an inhibitory effect on the activity of biomass and that kinetic data complied with the Haldane model for inhibitory wastes. Humate addition significantly enhanced the oxygen uptake by RAS. Application of humate at the dose of 2000 mg 1(-1) to the sewage contaminated with 10 mg l(-1) of diesel oil resulted in almost complete recovery of the biomass oxygen uptake. Non-linear regression analysis of the respirometric data indicated that this system complied with the Monod model for non-inhibitory wastes. Thus, the application of humic substances to mitigate the inhibitory effects of oil spills in wastewater treatment plants seems to be an attractive alternative to the treatments using activated carbon or specialized sorbents.

Fenton reaction in the presence of humates. Treatment of highly contaminated wastewater at neutral pH.

This paper presents the results of a treatability study conducted on highly contaminated wastewater using Fenton reaction at neutral pH, in the presence of humic substances. It has been found that addition of hurmates significantly accelerates the degradation of cyanide, thiocyanide, phenols and arsenic by ferrous iron and hydrogen peroxide. Only negligible amounts of contaminants of concern were removed when humates were added without the Fenton reagent. The mechanism of the humates effect is discussed. It is suggested that the combination of Fenton reagent with humates could provide a convenient and economical way for treatment of highly contaminated water at neutral pH.

Mutagenicity of pyridine- and quinoline-carbohydroxamic acid derivatives.

11 pyridine- and 6 quinoline-carbohydroxamic acids were tested for mutagenicity on Salmonella typhimurium TA100 and TA98. The results are compared with those obtained for benzohydroxamic acid and 4 naphthohydroxamic acids. Most of them were mutagenic on both these tester strains. Of the pyridine derivatives, pyridine-2-carbohydroxamic acid was the most potent mutagen. Quaternarization of the pyridine-ring nitrogen prevented the induction of mutation to a marked extent. Among the quinoline derivatives, quinoline-6-carbohydroxamic acid showed potent mutagenicity similar to that of 2-naphthohydroxamic acid. The present study supports the proposal made previously that the mechanism for mutagenicity of hydroxamic acids involves Lossen rearrangement of the acid conjugates produced by enzymic acylation (or perhaps phosphorylation or sulfation) of the hydroxamic acids, followed by carbamoylation of the target molecule in the cell by the resultant isocyanate. The multiplicity of factors determining the mutagenic potency of hydroxamic acids is discussed.

Hydrogen peroxide mediated photodegradation of phenol as studied by a flash photolysis/HPLC technique.

The technique of flash photolysis followed by high-performance liquid chromatography has been applied to the study of the photodegradation of phenol (I) in the presence of hydrogen peroxide. Progress of the reaction of I (0.1 mM) in undegassed aqueous solution ([H2O2]/[I] = 200/l) was observed by using multiple flashes (16 J). Analysis after a single flash indicated that catechol and hydroquinone were the primary products of the reaction. The reaction was found to be independent of pH in the range 7.0-9.0, but the yield of degradation decreased at pH > 9.0 and at pH < 7.0. The effects of the hydrogen peroxide concentration and flash energy on the chemical yield of the pollutant degradation, and product formation, were investigated as well. The mechanism of the reaction is discussed. A possibility of the application of flashlamps as powerful sources of the UV irradiation in industrial reactors for wastewater treatment is suggested.

The photolability of hydroxamic acids and its importance to the human environment.

Many xenobiotic and natural substances present in the natural environment undergo photochemical reactions which may result in the production of compounds more toxic than the starting components. One group of such substances is the hydroxamic acids. This review summarizes the structures, reactions, photochemistry and applications of hydroxamic acids, with particular emphasis on environmental aspects. The photochemistry of acyclic hydroxamic acids is shown to involve the generation of reactive acyl aminoxyl radical intermediates which may have biological consequences such as reactions with DNA. Thus, photoactivation of the carcinogenic properties of some hydroxamic acids present in the human environment can be expected.

Influence of some groundwater and surface waters constituents on the degradation of 4-chlorophenol by the fenton reaction.

The Fenton reaction has been applied to the degradation of 4-chlorophenol in aqueous solutions containing various anions. The rate of the reaction was found to decrease in the following order of anions (at the same concentrations): CIO (4) ~ NO (3)- > SO(4) (2-) > CI(-)> >HPO(4) (2-) > HCO(3)(-). Degradation of the pollutant containing the above anions at concentrations typical of those found in groundwater and surface waters was affected in a similar way. The results are discussed in terms of the effects of these anions on the rates of the oxidation of ferrous anion as well as on their role in the scavenging of hydroxyl radical

Degradation of carbon tetrachloride in the presence of iron and sulphur containing compounds.

The effect of several sulphur compounds: sodium sulphate, sodium sulphide, ferrous sulphide,pyrite and an organosulphonic acid on the kinetics of the iron (Fe °) induced degradation of carbon tetrachloride was examined under aerobic conditions. It was observed that all of the sulphur compounds investigated significantly accelerated the reaction. The mechanisms of the processes studied as well as their possible influence on the efficiency of the iron-induced dehalogenation of pollutants, both in situ and in above-ground treatment are discussed.

Utilization of landfill leachate parameters for pretreatment by Fenton reaction and struvite precipitation--a comparative study.

This paper reports results of laboratory studies on two pretreatment methods, struvite precipitation using aeration with H(3)PO(4) and Fenton oxidation. These methods utilized specific properties of the leachate: high magnesium content (172 mg L(-1)) for struvite precipitation and a high iron concentration (56 mg L(-1)) for Fenton treatment. Struvite precipitation (H(3)PO(4), 700 mg L(-1)) removed 36% of NH(3)-N and 24% of SCOD. Fenton treatment (at pH 3.5) required 650 mg L(-1) of H(2)O(2) and removed 66% of SCOD. The effect of each pretreatment on the returned activated sludge (RAS) was evaluated using respirometry. Both methods reduced the inhibitory effect of the leachate and substantially increased biokinetic parameters. The BOD(5)/SCOD ratio increased from 0.63 for raw leachate to 0.82 (struvite) and 0.88 (Fenton). Estimation of capital and operational costs of the total leachate treatment indicated that aeration with struvite precipitation, followed by biological treatment, would be the preferred option.