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Mikkeli, Finland

Vepsalainen M.,University of Eastern Finland | Selin J.,UPM Kymmene Oyj | Rantala P.,UPMKymmene Oyj | Pulliainen M.,Savcor Forest Oy | And 5 more authors.
Environmental Technology | Year: 2011

The precipitation of dissolved sulphide ions by electrocoagulation was studied at laboratory scale using pulp and paper mill wastewaters. Concentrations of dissolved organic carbon and phosphorus were analysed before and after the electrocoagulation process to examine the suitability of the process for treatment of sulphide odour from pulp and paper mill wastewater. The electrochemical cell used in this study was constructed from monopolar dissolving iron electrodes. The dissolved iron concentration was directly proportional to the applied electric charge (C/L) at the tested current densities. Electrochemically produced ferrous iron (Fe2+) precipitated dissolved sulphide ions efficiently. Electricity consumption of the treatment was 4-8 C/mg S2- while iron consumption was 1.1-2.2 mg/mg S2- during the initial phase of the sulphide precipitation when the applied electric charge was 10-60 C/L. When 60 C/L was applied, 88% of dissolved sulphides and 40% of phosphorus was precipitated. The reduction in DOC was low during the sulphide precipitation. According to these results, electrocoagulation can precipitate dissolved sulphides effectively and thereby reduce sulphide odours of pulp and paper mill wastewaters. © 2011 Taylor & Francis.

Sarkka H.,Lappeenranta University of Technology | Kolari M.,Kemira Oyj | Pulliainen M.,Savcor Forest Oy | Sillanpaa M.,Lappeenranta University of Technology
Current Organic Chemistry | Year: 2012

Oxidizing radical formation was tested in paper mill water together with biocides. The investigation of electrochemical behavior of biocides on SS 2343 and MMO (mixed metal oxide) electrode surfaces was conducted in synthetic paper mill water (cPMW). Hydrogen peroxide and peracetic acid gave response to the polarization on the anodic and cathodic sides on the SS 2343 electrode surface. At the MMO electrode the phenomenon was not observed. Other biocides did not show response with the polarization treatment. Hence, hydrogen peroxide polarized together with stainless steel electrode could cause radical reactions in paper mill water, and thus improve the process efficiency compared to hydrogen peroxide used alone. A synergistic effect of hydrogen peroxide with the polarization at the SS 2343 electrode could also help to keep the paper making process less sensitive to slime problems caused by microbes living in this environment. © 2012 Bentham Science Publishers.

Vilve M.,University of Eastern Finland | Vilhunen S.,University of Eastern Finland | Vepsalainen M.,Savcor Forest Oy | Kurniawan T.A.,University of Eastern Finland | And 3 more authors.
Environmental Science and Pollution Research | Year: 2010

Background, aim, and scope: Chlorinated volatile organic compounds (CVOCs), widely used in industry as solvents and chemical intermediates in the production of synthetic resins, plastics, and pharmaceuticals, are highly toxic to the environment and public health. Various studies reported that Fenton's oxidation could degrade a variety of chlorinated VOCs in aqueous solutions. In acidic conditions, ferrous ion catalyzes the decomposition of H2O2 to form a powerful •OH radical. In this study, wastewater from wash of ion-exchange resin containing typical CVOC, 1,2-dichloroethane, was treated using Fenton's oxidation. To reduce environmental load and processing costs of wastewater, Fenton process as a simple and efficient treatment method was applied to degrade 1,2-dichloroethane of wash water. Materials and methods: The water samples were collected from three different washing stages of ion-exchange resin. The degradation of 1,2-dichloroethane and total organic carbon (TOC) of wash water of ion-exchange resin by Fenton process was studied with response surface method (RSM). Design of the experiments was conducted by central composite face, and factors included in three models were Fe2+ and H2O2 doses and treatment time. Relevant quadratic and interaction terms of factors were investigated. Results: According to ANOVA, the model predicts well 1,2-dichloroethane reduction of all water samples and TOC reduction of samples 2 and 3. The Fe2+ and H2O2 doses used in the present study were most suitable when 1,2-dichloroethane concentration of the wash water is about 120 mg L-1. In that case, Fenton's oxidation reduced 1,2-dichloroethane and TOC up to 100% and 87%, respectively, according to the RSM model. With 90-min reaction time and H2O2 dose of 1,200 mg L-1, the required Fe2+ doses for 1,2-dichloroethane and TOC were 300 and 900 mg L-1, respectively. The optimal H2O2/Fe2+ stoichiometric molar ratio was between 4-6. Then, concentration of Fe2+ was low enough and the amount of residual sludge can thus be reduced. It seems that most of TOC and part of 1,2-dichloroethane were removed by coagulation. Discussion: Up to a certain extent, increase of Fe2+ and H2O2 doses improved the removal of 1,2-dichloroethane and TOC. High Fe2+ doses increased the formation of ferric-based sludge, and excessive H2O2 doses in sample 2 decreased the degradation of 1,2-dichloroethane. Excess amount of hydrogen peroxide may scavenge hydroxyl radicals, thus leading to loss of oxidative power. Also, the residual hydrogen peroxide of different samples increased with increasing H2O2 dose and H2O2/Fe2+ molar ratio and decreasing treatment time probably also due to scavenging reactions. Due to the saturated nature of 1,2-dichloroethane, the oxidation mechanism involves hydrogen abstraction before addition of hydroxyl radical, thus leading to lower rate constants than for direct hydroxyl radical attack, which for one increases the treatment time. Conclusions: Complete removal of 1,2-dichloroethane was attained with initial concentration >120 mg L-1. Also, TOC degraded effectively. Wash water with higher concentration of 1,2-dichloroethane requires longer treatment times and higher concentrations of Fe2+ and H2O2 for sufficient 1,2-dichloroethane removal. Recommendations and perspectives: Due to the results achieved in this study, Fenton's oxidation could be recommended to be used for organic destruction of wash water of ion-exchange resin. Residual sludge, the main disadvantage in Fenton process, can be reduced by optimizing the ferrous dose or by using heterogeneous treatment where most of the reusable iron remains in the solid phase. © 2010 Springer-Verlag.

Vepsalainen M.,VTT Technical Research Center of Finland | Vepsalainen M.,Lappeenranta University of Technology | Pulliainen M.,Savcor Forest Oy | Sillanpaa M.,Lappeenranta University of Technology
Separation and Purification Technology | Year: 2012

This study analyzed the effect of electrocoagulation cell construction on NOM removal from Finnish surface water. Three types of cells were used in this research: one that only had aluminum electrodes, one that had aluminum anodes and inert cathodes, and one that had inert anodes and aluminum cathodes. Main water quality parameters such as TOC, apparent color, and concentrations of residual metals were measured from the samples. A statistical model was made from the results using partial least squares (PLSs) regression. According to the results, electrocoagulation was able to produce high quality water with low NOM concentration. Lowest measured TOC concentration was 4.02 mg/l (78% removal). The potential applications of water after the treatment could be potable water or industrial fresh water. Aluminum originating from the anodes or cathodes had similar NOM removal efficiency. According to TOC and ζ-Potential results, the mechanism of NOM removal was similar to chemical coagulation in different pHs. It seems that in low pH, double layer compression was the main destabilization mechanism whereas in higher pH, adsorption and bridging dominated.© 2012 Elsevier B.V. All rights reserved.

Vepsalainen M.,VTT Technical Research Center of Finland | Vepsalainen M.,Lappeenranta University of Technology | Kivisaari H.,University of Jyvaskyla | Pulliainen M.,Savcor Forest Oy | And 2 more authors.
Separation and Purification Technology | Year: 2011

This study investigated the effect of electrocoagulation treatment on toxic pollutant removal from pulp mill effluents. Synthetic wastewaters containing wood rosin and copper or pure resin acids were used to investigate the removal of resin acids and copper by electrocoagulation. Removal of pollutants by electrocoagulation was also tested with real debarking effluent. In this study, statistical experimental design and partial least squares modeling were used to investigate the effect of initial pH, current (current density) and treatment time. Electrocoagulation and subsequent filtration removed resin acids and copper from the synthetic wastewaters with high efficiency. Toxicity to algae (Pseudokirchneriella subcapita) was completely eliminated by the treatment, however reduction of bacterial toxicity (Vibrio fischeri) was more limited. While the initial EC50 value for bacteria in debarking effluent was around 8-14 vol%, toxicity was approximately halved by electrocoagulation. Toxicity removal from the debarking effluents was associated with color removal. © 2011 Elsevier B.V. All rights reserved.

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