Tuula Tuhkanen

Removal of NOM in the different stages of the water treatment process

Natural organic matter (NOM) is abundant in natural waters in Finland and in many ways affects the unit operations in water purification. In this study, the organic matter content in water in different stages of a full-scale treatment process over 1 year was measured. The full-scale treatment sequence, studied at the Rusko water treatment plant in Tampere, Finland, consisted of coagulation, flocculation, clarification by sedimentation or flotation, activated carbon (AC) filtration, and disinfection. High-performance size exclusion chromatography (HPSEC) was used for separation to determine changes in the humic substances content during the purification process. In addition, total organic carbon (TOC), KMnO4-number, and UV-absorbance at wavelength 254 nm (UV254) were measured. High molecular weight (HMW) matter was clearly easier to remove in coagulation and clarification than low molecular weight (LMW) matter. Furthermore, depending on the regeneration of the activated carbon filters, activated carbon filtration was effective to a degree but did not remove most of the lowest molecular weight compounds. Significant correlation was established among HPSEC, KMnO4, UV254 absorbance, and TOC. HPSEC proved to be a fast and relatively easy method to estimate NOM content in water and, in fact, gave more information than traditional methods on the type of NOM in a water sample. It also helped the process performance follow-up.

Removal of Pharmaceuticals in Drinking Water Treatment: Effect of Chemical Coagulation

The removal of selected pharmaceuticals (diclofenac, ibuprofen, bezafibrate, carbamazepine and sulfamethoxazole) by chemical coagulation was studied. Jar test experiments were done in MilliQ water, in lake water and in commercial humic acid solutions using aluminium (pH 6) and ferric sulphate (pH 4.5). The concentrations of the pharmaceuticals in the studied water samples were determined by HPLC analysis and UV detection. In MilliQ water coagulation, the pharmaceuticals were poorly removed (< 10%) with the exception of diclofenac, which was removed up to 66% with ferric sulphate. This compound was also the only pharmaceutical removed (30%) during the lake water coagulation with ferric sulphate. In the presence of dissolved humic matter, diclofenac as well as ibuprofen and bezafibrate could be removed by ferric sulphate coagulation. The removal of diclofenac reached a maximum of 77%, while 50% of ibuprofen and 36% of bezafibrate were removed. Hence, a high amount of high-molecular-weight dissolved organic matter enhanced the removal of ionisable pharmaceuticals. The non-ionisable compounds, carbamazepine and sulfamethoxazole, were not affected by the coagulation processes studied. Although conditions such as high humic material content, low coagulation pH and ferric coagulant increase the removal of certain ionic pharmaceuticals, it can be concluded that by coagulation it is not possible to entirely remove pharmaceuticals from water.

Oxidative treatment of simulated dyehouse effluent by uv and near-UV light assisted Fenton's reagent

UV/Fenton, near-UV-visible/Fenton, dark Fenton, and H2O2/UV reactions have been used to treat simulated dyehouse effluents representing wastewater from the textile dyeing and rinsing process. Experiments were carried out in a lab - scale photochemical reactor using concentrations of 0.5–25 mM H2O2, 0.04-0.5 mM Fe2+-ion and different dilutions of textile wastewater. To assess the extent of mineralization, decolourization kinetics and the effect of different fight sources on treatment efficiency, DOC, optical density at 254 nm and 600 nm wavelength and residual H2O2 concentrations were measured during the course of the advanced oxidation reactions. Comparative evaluation of the obtained results revealed that the decolourization rate increased with applied H2O2 and Fe2+-ion dose as well as the strength of the synthetic textile wastewater. The best results were obtained by the near - UV/visible/Fenton process with a decolourization rate constant of 1.57 min−1, a UV254nm reduction of 97% and a DOC removal of 41% at relatively low doses of the H2O2 oxidant and Fe2+-ion catalyst within 60 min treatment time.

Advanced Oxidation of Synthetic Dyehouse Effluent by O3, H2O2/O3 and H2O2/UV Processes

Ozonation, hydrogen peroxide combination with ozone, and UV light processes were investigated for the treatment of synthetic dyehouse effluent containing six reactive dyestuffs and their assisting chemicals. The decrease in DOC, UV - absorbance at 254 nm, decolourization kinetics, and acute toxicity towards the bioluminescent marine bacteria Vibrio fischeri were used to examine the treatment performance of these oxidation processes. Data indicated that in all examined processes rapid and complete decolourization could be achieved, but optimum oxidation conditions such as H2O2 dose and reaction pH had to be established for effective treatment. Toxicity of the samples decreased abruptly to non - detectable levels during the first minutes of all advanced oxidation processes. However, none of the oxidation combinations was able to bring about effective mineralization of the wastewater within 60 min reaction period. For comparative purposes, the electrical energy requirements per order of pollutant removal wer...

Photodegradation of ethylenediaminetetraacetic acid (EDTA) and ethylenediamine disuccinic acid (EDDS) within natural UV radiation range

The rate of photodegradation of two chelating agents, ethylenediaminetetraacetic acid (EDTA) and an isomeric mixture of ethylenediamine disuccinic acid (EDDS), was analysed in humic lake water and in distilled water using exposure to sunlight, and in the laboratory using lamps emitting UV radiation in the range 315-400 nm. Degradation was studied using Fe(III) complexes and sodium salts of chelates. Fe(III) complexes were illuminated at pH 3.1 and 6.5. The results demonstrated that the rate of photodegradation of Fe(III)-EDTA and Fe(III)-EDDS complexes seems to be pH dependent. In the laboratory experiments degradation occurred much faster when the original pH was 3.1 rather than 6.5. The photodegradation of the isomeric mixture of EDDS was markedly faster than the degradation of EDTA both in the laboratory and field experiments, and both in humic and distilled water. The results indicated that in natural waters photodegradation of EDDS is independent of initial speciation of EDDS, while degradation of EDTA is dependent on its existence as Fe(III)-EDTA species.

Comparison of the Effiency of Aluminium and Ferric Sulphate in the Removal of Natural Organic Matter During Drinking Water Treatment Process

The removal of natural organic matter by coagulation in the drinking water treatment train was studied for a period of two years. In the middle of the study, the coagulation/flotation process was modified by replacing the aluminium sulphate by ferric sulphate. At the same time, the filtration unit was enhanced by adding a sand filter unit before the activated carbon filtration and by changing new carbons on to the activated carbon filters. A special aim was to compare the efficiency of the aluminium and ferric coagulants in the organic matter removal by several methods, including high-performance size-exclusion chromatography. A comparison of quantity and characteristics of organic matter in treated water before and after treatment process modification provided an insight into process performance. Approximately 95% of high molar mass organic substances were removed in the process with both coagulation agents. The greatest difference between the coagulants occurred in the removal of organic matter having molar masses of 1000-4000 g mol−1. These intermediate molar mass organic compounds were removed 25 % more efficiently with iron-based coagulant than with aluminium-based. Low molar mass material was poorly removed regardless of the coagulant. On average, only 10 % of this fraction was removed. According to different measuring techniques used in the study, the ferric sulphate coagulation was 10 % more efficient in the overall organic matter removal compared to the aluminium sulphate coagulation. Turbidity removal was more efficient with aluminium than with ferric sulphate. Turbidity even increased during winter in ferric sulphate coagulation. However, turbidity was effectively removed in filtrations.

Oxidation by Fenton's reagent combined with biological treatment applied to a creosote-comtaminated soil.

In this study, we investigated the feasibility of using Fenton oxidation to remove sorbed polycyclic aromatic hydrocarbons (PAHs) in aged soil samples with creosote oil from a wood preserving site. The optimal dosage of reagents was determined by a statistical method, the central composite rotatable experimental design. The maximum PAH removal was 80% with a molar ratio of oxidant/catalyst equal to 90:1. In general low molecular weight PAHs (3 rings) were degraded more efficiently than higher molecular weight PAHs (4 and 5 rings). The hydrogen peroxide decomposition kinetic was studied in the presence of KH(2)PO(4) as stabilizer. The kinetic data were fitted to a simple model, the pseudo-first-order which describes the hydrogen peroxide decomposition. The PAH kinetic degradation was also studied, and demonstrated that non-stabilized hydrogen peroxide was consumed in less than 30 min, whilst PAH removal continued for up to 24h. In a second part of the work, a combined chemical and biological treatment of the soil was carried out and shown to be dependent on the pre-oxidation step. Different reagent doses (H(2)O(2):Fe) were used (10, 20, 40, 60:1) in the pre-treatment step. An excess of hydrogen peroxide resulted in a poor biological removal, thus the optimal molar ratio of H(2)O(2):Fe for the combined process was 20:1. The combined treatment resulted in a maximum total PAH removal of 75% with a 30% increase in removal due to the biodegradation step. The sample with highest PAH removal in the pre-oxidation step led to no further increase in removal by biological treatment. This suggests that the more aggressive chemical pre-oxidation does not favour biological treatment. The physico-chemical properties of the pollutants were an important factor in the PAH removal as they influenced chemical, biological and combined treatments.

Treatment of Industrial Landfill Leachates By Chemical And Biological Methods: Ozonation, Ozonation + Hydrogen Peroxide, Hydrogen Peroxide And Biological Post-Treatment For Ozonated Water

Abstract The objective of this study was to determine a suitable treatment method for variable waters from a forest industry landfill site. The main target was to find out the impact of different chemical treatments on the composition and biodegradability of those waters. Earlier studies have shown that biological treatment alone is not a suitable treatment method for these waters. That is why ozonation, ozonation+hydrogen peroxide and hydrogen peroxide treatment were studied in a laboratory scale. The ozonated waters were also biologically post-treated. All the methods studied were able to degrade a part of the organic compounds and convert them into a more biodegradable form. Also the BOD/COD -ratio increased significantly. The removal of organic compounds by ozonation was 30 - 50 %. Hydrogen peroxide addition did not improve the degradation. The combination of pre-ozonation and biological post-treatment gave a total TOC removal between 50 - 95 %.

A study of toxicity, biodegradability, and some by-products of ozonised nitrophenols

Abstract Treatment performances of ozonation applied for the degradation of nitrophenols (NPs) were assessed in terms of biodegradability improvement, and toxicity reduction. Among the by-products formed during the ozonation of 4-nitrophenol and 2,4-dinitrophenol at initial pH 9.5 4-nitrocatechol, p-quinone, and hydroquinone were identified. The by-products of NPs ozonation were much more biodegradable than NPs. The degree of organically bounded nitrogen conversion to nitrate was 66–100% at pH 2.5 and 38–87% at initial pH 9.5. The reduction of ozone consumption and acceleration of NPs degradation rate was achieved during the ozonation of NP mixture at initial pH 9.5. According to Daphnia magna acute toxicity test, a complete detoxification of ozonised solutions was achieved. Thus, ozonation can be applied as a very effective treatment method for detoxification and biodegradability improvement of NPs containing wastewater. The achieved biodegradability improvement and detoxification of treated NPs supports the potential use of ozonation to improve the capacity of conventional biological treatment to remove these toxic and poorly biodegradable compounds.

Microbial growth in drinking waters treated with ozone, ozone/hydrogen peroxide or chlorine

Abstract The effects of ozonation, hydrogen peroxide treatment and chlorination on the quality of organic matter and microbiological growth in drinking water were studied in a pilot plant. All oxidants degraded organic matter (humus) increasing the concentration of assimilable organic carbon (AOC). Even though the oxidants efficiently decreased microbial numbers, microbial regrowth occurred in all drinking waters. Microbial regrowth was strong especially after ozone/hydrogen peroxide treatment. Chlorination combined with ozone and hydrogen peroxide decreased microbial numbers most efficiently. However, microbial growth started even in chlorinated samples within 2-3 days.