Rein Munter

Ozonation, Ozone/UV and UV/H2O2 Degradation of Chlorophenols

Abstract The performance of the O3, O3/UV and UV/H2O2 processes for degradation of six chlorophenols (4-chlorophenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol) were studied in laboratory reactors. Comparative study showed that chlorophenols can be degraded successfully by all of the methods studied, whilst traditional ozonation at high pH was determined to be the most effective method to treat chlorophenols. Even though the molar absorptivity of chlorophenols is known to be relatively high in the UV-region, the combination of UV-radiation with ozone did not accelerate the degradation of chlorophenols further. The toxicity of degradation products formed during ozonation of chlorophenols has been compared with the toxicity of pure chlorophenols utilizing Daphnia magna 24 hours test. Ozonation of chlorophenols yielded less toxic or even nontoxic products for Daphnia magna compared with parent compounds.

Polychlorinated biphenyls-containing electrical insulating oil contaminated soil treatment with calcium and magnesium peroxides.

Calcium and magnesium peroxides were applied for the treatment of soil contaminated by polychlorinated biphenyls-containing electrical insulating oil (Aroclor 1016). The removal of PCB-containing electrical insulating oil was achieved with the addition of either calcium peroxide or magnesium peroxide alone and dependent on dosages of the chemical. A 21-d treatment of 60% watered soil with the moderate addition (chemical/oil weight ratio of 0.005/1) of either calcium peroxide or magnesium peroxide resulted in nearly complete (96 ± 2%) oil removal, unsubstantial increase in soil pH and almost no changes in oxygen consumption and dehydrogenase activity, making it suitable for the soil decontamination.

Catalytic Ozonation of m-Dinitrobenzene

The efficiency of catalytic ozonation with homogeneous (containing dissolved ions of Fe2+, Mn2+, Cu2+, Ni2+, Co2+, V5+, Cr3+, Mo6+) and heterogeneous (MnO2, Ni2O3, Fe2O3, CuO, Al2O3, CoO, V2O5, Cr2O3, MoO3, TiO2) catalysts and non-accompanied ozonation was compared for degradation of m-dinitrobenzene (m-DNB). Several transition metals in homogeneous and heterogeneous form improved significantly the ozone performance for degradation of m-DNB. This improvement was found to be due to supplementary formation of reactive species (hydroxyl radicals) and better ozone utilization. The effects observed were found to be strongly dependent on the treatment conditions.

Modelling of Chlorophenol Treatment in Aqueous Solutions. 1. Ozonation and Ozonation Combined with UV Radiation under Acidic Conditions

Abstract Treatment of 2-chlorophenol (2-CP), 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) in aqueous solutions with direct photolysis (254 nm), ozonation and ozonation with photolysis was studied. A model was developed to simulate chlorophenol treatment in a semibatch column using these processes under acidic conditions in which the chemical reactions are slow. Satisfactory results were obtained in simulating the chlorophenol and ozone concentrations, and the concentrations of an aromatic quinone, hydrogen peroxide and chloride ions formed in the course of the processes. Chlorophenol oxidation systems, however, appeared to be very complex and the formation of intermediate and final products were dependent on the reaction conditions. The degradation rate of chlorophenols was not enhanced by the combination of ozone with UV radiation compared with ozonation alone. Oxidation at low pH in both processes proceeded mainly through reactions with molecular ozone.

Fenton treatment efficacy for the purification of different kinds of wastewater

The Fenton chemistry comprises both the classical Fenton reagent and its modification, so-called Fenton-like techniques, which have received great attention as a promising technology for wastewater treatment. In the present study real wastewater from different sources (leachate from oil shale semicoke landfill, pharmaceutical effluents from medical ointment production, municipal landfill leachate and wastewater originated from food-processing) were treated by means of Fenton/Fenton-like systems. The effectiveness of wastewater treatment was assessed by COD removal. Additionally, biodegradability improvement (BOD7/COD) and acute toxicity reduction of investigated wastewater samples were observed. The application of the Fenton chemistry to wastewater samples with different origin resulted generally in 70% or higher COD removal. Thus, the Fenton could be effectively applied both as a single treatment method and pre-treatment step to improve subsequent biodegradability of wastewater effluents.

Cost Effectiveness of Ozonation and AOPs for Aromatic Compound Removal from Water: A Preliminary Study

The capital and operating costs for several aromatic compounds (phenanthrene, 2,4-dimethylphenol, 2,4,6-trichlorophenol, nitrobenzene) removal from polluted groundwater using ozonation and advanced oxidation have been estimated on the basis of the laboratory experiments in semibatch conditions. The pollutants initial concentration was in the range of 0.01–1.0 mM. In the calculations the polluted groundwater flow rate was taken 40 m3/h with the initial pH = 7.0. It is shown that polluted groundwater purification from the aromatic pollutants with the initial concentration in the range of 0.01–1.0 mM using ozonation and advanced oxidation is economically feasible.

Modelling of Chlorophenol Treatment in Aqueous Solutions. 2. Ozonation under Basic Conditions

Abstract Ozonation of 2-chlorophenol (2-CP), 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) in basic aqueous solutions is discussed. In such conditions (pH=9.5), ozonation of chlorophenols proceeds rapidly due to the presence of the dissociated form of the phenolic compound. No ozone occurs in the bulk of the liquid and, in modelling, it becomes necessary to account for the reactions in the liquid film. Two approaches were tested: 1) the film and bulk balances were solved sequentially, and the diffusional fluxes coupling the balances were obtained by solving numerically the concentration profiles in the film; 2) the bulk mass balances were solved without the film mass balances by applying the enhancement factor calculated from existing correlations. The results of both approaches are compared with experimental data. The formation mechanism of an aromatic quinone, hydrogen peroxide and chloride ions during the ozonation appeared to differ under basic conditions from that under acidic conditions. Hy...

Comparison of Mass Transfer Efficiency and Energy Consumption in Static Mixers

The aim of this study was to compare the pressure drop (Δp) generated by a static mixer with sieve plates in two-phase downflow (water as a continuous phase), and the mass transfer efficiency (kLa, a) with the performance of other static mixers (Sulzer, Kenics, Karman, etc.). The relationships for Δp, kLa and interfacial area (a) calculation depending on liquid and gas phase velocities and geometry of the plates (sieves) in this static mixer are presented. kLa was found to be strictly proportional to the power consumption (P/V) and its values were quite close to those obtained in Sulzer & Kenics mixers with an 8-element mesh. Enhancement factors for oxygen absorption in the sodium sulphite solution and for ozone absorption in Lake Ülemiste water were calculated and the plausible values of the interfacial area (a) were estimated.

Which is the Best Oxidant for Complexed Iron Removal from Groundwater: The Kogalym Case

A short overview of the significance of a preoxidation stage groundwater treatment is presented. As an example the case of complexed iron removal from Kogalym groundwater (Tjumen, Siberia, Russian Federation) using different preoxidants (ozone, oxygen, chlorine, hydrogen peroxide, and potassium permanganate) is discussed. The key problem is stable di-and trivalent iron-organic complexes in groundwater which after aeration tend to pass through the hydroanthracite-sand gravity filters. The total organic carbon (TOC) content in raw groundwater is in the range of 3.2–6.4 mg/L, total iron content 2.7–6.0 mg/L and divalent iron content 2.4–4.0 mg/L. Separation from Kogalym groundwater by XAD-16 adsorbent humic matter fraction was homogeneous, with only 1 peak on the chromatogram with maximum Rt = 10.75 min and corresponding molecular mass 1911 (<2000). The final developed treatment technology is based on the water oxidation/reduction potential (ORP) optimization according to the iron system pE-pH diagram and consists of intensive aeration of raw water in the Gas-Degas Treatment (GDT) unit with the following sequence: filtration through the hydroanthracite and special anthracite Everzit, with intermediate enrichment of water with pure oxygen between the filtration stages.

Temporal changes in radiological and chemical composition of Cambrian-Vendian groundwater in conditions of intensive water consumption

Intensive groundwater uptake is a process at the intersection of the anthroposphere, hydrosphere, and lithosphere. In this study, groundwater uptake on a peninsula where only one aquifer system - the Cambrian-Vendian (CmV) - is available for drinking water uptake is observed for a period of four years for relevant radionuclides and chemical parameters (Cl, Mn, Fe, δ18O). Intensive groundwater uptake from the CmV aquifer system may lead to water inflow either from the sea, through ancient buried valleys or from the under-laying crystalline basement rock which is rich in natural radionuclides. Changes in the geochemical conditions in the aquifer may in turn bring about desorption of Ra from sediment surface. Knowing the hydrogeological background of the wells helps to predict possible changes in water quality which in turn are important for sustainable groundwater management and optimization of water treatment processes. Changes in Cl and Ra concentrations are critical parameters to monitor for sustainable management of the CmV groundwater. Radionuclide activity concentrations in groundwater are often considered rather stable, minimum monitoring frequency of the total indicative dose from drinking water is set at once every ten years. The present study demonstrates that this is not sufficient for ensuring stable drinking water quality in case of aquifer systems as sensitive as the CmV aquifer system. Changes in Cl concentrations can be used as a tool to predict Ra activity concentrations and distribute the production between different wells opening to the same aquifer system.