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The main goal of this study was to develop a cost-efficient biological method for the removal of sulfate from mining effluents in cold conditions. A consortium of cold-tolerant sulfate-reducing bacteria (SRB) was tested at 6 °C regarding the utilization of economically viable, low-cost carbon sources, i.e., whey, conditioned sewage sludge, and peat, in the removal of sulfate from synthetic mining water. Succinate was used as a reference carbon source. Of all the studied low-cost carbon sources, conditioned sewage sludge proved to be the most efficient. Nuclear magnetic resonance (NMR) spectroscopy revealed that sewage sludge contained propionic acid, which proved to be utilizable by SRB under cold conditions. Peat both adsorbed the sulfate and acted as a nutrient source in the sulfate reduction process. When whey was used as a carbon source, only a slight decrease in sulfate concentration was detected. Succinate was found to work in a truly predictable and efficient way as a carbon source in biological sulfate reduction, even at the lowest concentration tested. The use of conditioned sewage sludge increased the bacterial diversity in liquid cultivations significantly. However, the number of SRB was highest in the succinate cultivations. HIGHLIGHTS Cold-tolerant sulfate-reducing bacteria (SRB) were successfully cultivated using low-cost carbon sources.; Kemicond-treated sewage sludge was the most efficient low-cost carbon source.; Simultaneous sulfate adsorption and reduction were observed with natural peat.; Organic compounds utilized and produced by the bacteria were characterized by nuclear magnetic resonance (NMR).; Synthetic mining water was treated to model real water pollution control.

The aim of this study was to develop a biological method for the simultaneous removal of sulfate and metals from acidic low-temperature mining effluents. A mixed consortium of cold-tolerant sulfate-reducing bacteria (SRB) and other microorganisms was immobilized on glass beads and exploited in an up-flow biofilm reactor for the continuous treatment of actual and synthetic mining-impacted waters (MIWs) with initial sulfate concentrations between 1580 and 5350 mg L-1. The proton acidity of the mine waters was neutralized by microbial sulfidogenesis. Metals present in the MIWs were precipitated either off-line or in-line, inside the reactor vessel. High sulfate reduction rates (SRRs), from 1000 to 4500 mg L-1 d-1 at a temperature of 11.7 ± 0.2 °C, were achieved (sulfate removal 43–87%). The bacterial consortium was found to be robust and resistant to changes in growth conditions during the bioreactor experiment. The relative abundance of SRB and the SRR increased at higher sulfate concentrations. Sulfidogenic bioreactors have the potential for treatment of acid mine drainage even at low temperature. It was demonstrated that neutral reactor conditions and high SRRs were maintained when acidic influent was fed into the reactor.

In this study, two-step surface modification of sawdust using triethanolamine (at 180 °C) and iodomethane (at 42 °C) was performed to produce a novel quaternized biosorbent, TEA-I-SD. The characterization studies revealed significant morphological changes in the sawdust and successful quaternization with a nitrogen content of 5.75%. The highest vanadium removal (96.2%) was achieved at pH 4 (dosage 1 g/L, initial vanadium concentration 19.1 mg/L). Equilibrium was achieved within 8 h of contact time and the adsorption kinetics were well fitted with the pseudo-second-order model. Both film diffusion and intra-particle diffusion contributed to the adsorption process, while the latter was the rate-limiting step. The maximum vanadium adsorption capacity of TEA-I-SD (35.0 mg/g, pH 4) was close to the theoretical value obtained from the Langmuir model. The best fit was achieved with the Redlich-Peterson model, exhibiting a monolayer adsorption phenomenon. Tests with real mine water containing 11 mg/L of vanadium also confirmed its high removal (91.3%, dosage 1 g/L) using TEA-I-SD at pH 4. The TEA-I-SD could be reused three times without significant capacity loss after regeneration, although the desorption efficiency was rather low (synthetic solution: 38.5–40.5% and mine water: 26.2–43.1%).

Aminated peat (termed PG-Peat) produced using polyethylenimine and glycidyltrimethylammonium chloride was used for the removal of sulphate from real acid mine drainage (AMD) in batch and column mode sorption studies. In the batch tests, the highest sulphate removal capacity achieved was 125.7 mg/g. PG-Peat was efficient and rapid in sulphate removal from AMD even at low temperatures (2–5 °C), achieving equilibrium within a contact time of 30 min. The PG-Peat column treating real AMD showed even higher sulphate uptake capacity (154.2 mg SO42−/g) than the batch sorption studies. The regenerative and practical applicability of PG-Peat was also tested in column set-ups using synthetic sulphate solutions (at pH 5.8 and pH 2.0). The sulphate uptake capacity obtained was higher in column mode when the solutions were treated at acidic pH (2.0) compared to pH 5.8. This could be attributed to the presence of cationized amine groups on PG-Peat under acidic pH conditions. Almost complete sulphate desorption was achieved with NaCl in the column that treated synthetic sulphate solution at pH 5.8, while the lowest desorption rates were observed in the column that treated acidic synthetic sulphate solution (pH 2).

Geopolymers are functional materials that can be used in various environmental applications such as adsorbents in pollutant removal from wastewaters. Metakaolin geopolymer (MK-GP) has been proven to be especially suitable for ammonium (NH4 +) removal. In this research, the optimal reagent and raw material ratios in the preparation of MK-GP in terms of NH4 + adsorption capacity were investigated. The response surface methodology based on the face-centered central composite design was used to optimize the levels of three factors: the amounts of hydroxide, silicate, and metakaolin. In addition, the effect of Na or K as the charge-balancing cation was studied. Empirical models were fitted to the experimental data using multiple linear regression. The significance of the models was confirmed by means of analysis of variance. Optimal NH4 + removal efficiency was achieved when the amounts of hydroxide and silicate were maximized, the amount of metakaolin was minimized, and Na-based reagents were used. These trends are most likely a result of optimized conversion of metakaolin into MK-GP.

Blast-furnace slag and metakaolin were geopolymerised, modified with barium or treated with a combination of these methods in order to obtain an efficient SO4(2-) sorbent for mine water treatment. Of prepared materials, barium-modified blast-furnace slag geopolymer (Ba-BFS-GP) exhibited the highest SO4(2-) maximum sorption capacity (up to 119mgg(-1)) and it compared also favourably to materials reported in the literature. Therefore, Ba-BFS-GP was selected for further studies and the factors affecting to the sorption efficiency were assessed. Several isotherms were applied to describe the experimental results of Ba-BFS-GP and the Sips model showed the best fit. Kinetic studies showed that the sorption process follows the pseudo-second-order kinetics. In the dynamic removal experiments with columns, total SO4(2-) removal was observed initially when treating mine effluent. The novel modification method of geopolymer material proved to be technically suitable in achieving extremely low concentrations of SO4(2-) (

Biological sulfate removal is challenging in cold climates due to the slower metabolism of mesophilic bacteria; however, cold conditions also offer the possibility to isolate bacteria that have adapted to low temperatures. The present research focused on the cold acclimation and characterization of sulfate-reducing bacterial (SRB) consortia enriched from an Arctic sediment sample from northern Finland. Based on 16S rDNA analysis, the most common sulfate-reducing bacterium in all enriched consortia was Desulfobulbus, which belongs to the δ-Proteobacteria. The majority of the cultivated consortia were able to reduce sulfate at temperatures as low as 6 °C with succinic acid as a carbon source. The sulfate reduction rates at 6 °C varied from 13 to 42 mg/L/d. The cultivation medium used in this research was a Postgate medium supplemented with lactate, ethanol or succinic acid. The obtained consortia were able to grow with lactate and succinic acid but surprisingly not with ethanol. Enriched SRB consortia are useful for the biological treatment of sulfate-containing industrial wastewaters in cold conditions.

A novel bio-based anion exchanger was developed to remove sulphate from synthetic solutions and mine water. Different modification parameters such as chemical dosage and reaction time were tested when using a unique combination of branched polyethylenimine (PEI) and glycidyltrimethylammonium chloride (GTMAC) to produce an aminated biosorbent (termed PG-Peat). The novel and environment-friendly modification method was shown by FTIR and XPS analyses to be able to introduce quaternary ammonium and N-H groups into PG-Peat. The optimal modification conditions (PEI: 0.26 mmol/g, GTMAC: 0.0447 mol/g, reaction time: 18 h) resulted in the maximum sulphate uptake capacity (189.5 ± 2.7 mg/g) with a partition coefficient value of 0.02 mg/g/μM under acidic conditions. At low pH, amine groups on the peat surface became cationized, thereby resulting in a higher sulphate removal capacity. Batch sorption tests using PG-Peat exhibited rapid sulphate sorption after only five minutes of contact. The sulphate uptake by PG-Peat was unaffected by the presence of varying chloride concentrations, while slightly lower uptake capacity was observed when different concentrations of nitrate were present. The biosorbent showed high recyclability, which was revealed in regeneration studies. Tests were performed involving real mine water, where PG-Peat showed its potential to be a highly efficient biosorbent for sulphate removal at low pH values, indicating its suitability for treating acidic mine waters.

Sulphate removal from mine water is a problem because traditional chemical precipitation does not remove all sulphates. In addition, it creates lime sediment as a secondary waste. Therefore, an inexpensive and environmental-friendly sulphate removal method is needed in addition to precipitation. In this study, carbon residues from a wood gasification process were repurposed as precursors to a suitable sorbent for SO42- ion removal. The raw material was modified using ZnCl2, BaCl2, CaCl2, FeCl3, or FeCl2. Carbon residues modified with FeCl3 were selected for further consideration because the removal efficiency toward sulphate was the highest. Batch sorption experiments were performed to evaluate the effects of the initial pH, initial SO42- ion concentration, and contact time on sulphate removal. The removal of SO42- ions using Fe-modified carbon residue was notably higher compared with unmodified carbon residue and commercially available activated carbon. The sorption data exhibited pseudo-second-order kinetics. The isotherm analysis indicated that the sorption data of Fe-modified carbon residues can be represented by the bi-Langmuir isotherm model.

Influence of altering magnetic field on chemical properties of water, scale formation and morphology was studied using polyethylene and copper pipes located both in a laboratory pilot-system and in an apartment complex formed by five different buildings each having four or five different homes. In the pilot network, magnetic field decreased calcium scaling by 15% in the both studied piping materials. Also, surface film on the copper pipe appeared to be less compact by the magnetic exposure. In the studies conducted in the apartment complex, magnetic field effectively mobilized earlier accumulated iron and copper from the copper pipe surfaces especially dealing with a hot water circuit.

Geopolymers are aluminosilicate compounds that are amorphous analogues of zeolites, and thus possess similar cation-exchange properties. Geopolymers have been successfully applied to remove toxic metals and organic dyes from aqueous solutions. In this study, geopolymer was synthesized from metakaolin and applied to remove ammonium (NH 4 + ) from model solutions and landfill leachate. Geopolymerization increased the ammonium removal capacity, surface area and average pore width and changed the chemical structure of metakaolin. The maximum NH 4 + removal capacity of the geopolymer was 21.07 mg g − 1 which was 46% higher than the capacity of the reference clinoptilolite–heulandite zeolite (14.42 mg g − 1 ). The adsorption data of the geopolymer and zeolite fitted best to the Langmuir–Freundlich isotherm and the removal kinetics followed the pseudo-second order kinetic equation. The spent geopolymer adsorbent was regenerated efficiently using 0.2 M NaCl and 0.1 M NaOH as a regenerant. A small-scale continuous field experiment with landfill leachate was performed and further indicated that the metakaolin-based geopolymer could be a feasible NH 4 + removal adsorbent.

The electrocoagulation (EC) process employed in the removal of phosphate from synthetic wastewater (SWW, 30 mg/l) was optimized, followed by successful scale-up experiments. The optimum process conditions (96% phosphate removal) for laboratory-scale SSW were found to be: anode/cathode = Al/Fe (although Fe/Al performed similarly), initial pH = 5, current density = 100 A/m 2 , treatment time = 15 min, supporting electrolyte = 1.0 g/l NaCl and electrode gap = 7 mm. Real industrial phosphate-containing mining wastewater (MWW) and dairy wastewater (DWW) were also treated with EC, with high pollutant removal efficiencies (optimal phosphate removal of 79% and 93% in 30 min and 60 min, respectively) achieved over the wide initial pH range studied. Electricity consumption and operating costs values in optimum conditions were low for all wastewaters: 0.75 kWh/m 3 and 0.17 €/m 3 for SSW (laboratory scale), 2.11 kWh/m 3 and 0.28 €/m 3 for MWW, and 1.46 kWh/m 3 and 0.31 €/m 3 for DWW. To summarize, the feasibility of using EC in removing phosphate from the wastewater types studied was proven. Utilization of the resulting EC sludge – a potentially valuable phosphorus source in the future (especially in granulated bio ash-based fertilizer products) – was also studied and is discussed.

Electrocoagulation (EC) treatment of 100 mg/L synthetic wastewater (SWW) containing humic acids was optimized (achieving 90% CODMn and 80% DOC removal efficiencies), after which real peat bog drainage waters (PBDWs) from three northern Finnish peat bogs were also treated. High pollutant removal efficiencies were achieved: Ptot, TS, and color could be removed completely, while Ntot, CODMn, and DOC/TOC removal efficiencies were in the range of 33–41%, 75–90%, and 62–75%, respectively. Al and Fe performed similarly as the anode material. Large scale experiments (1 m3) using cold (T = 10–11 °C) PBDWs were also conducted successfully, with optimal treatment times of 60–120 min (applying current densities of 60–75 A/m2). Residual values of Al and Fe (complete removal) were lower than their initial values in the EC-treated PBDWs. Electricity consumption and operational costs in optimum conditions were found to be low and similar for all the waters studied: 0.94 kWh/m3 and 0.15 €/m3 for SWW and 0.35–0.70 kWh/m3 and 0.06–0.12 €/m3 for the PBDWs (large-scale). Thus, e.g. solar cells could be considered as a power source for this EC application. In conclusion, EC treatment of PBDW containing humic substances was shown to be feasible.

The aim of this research was to investigate the effect of magnesium on the removal efficiency of sulphate as gypsum from mine water. The precipitation conditions were simulated with MINEQL + software and the simulation results were compared with the results from laboratory jar test experiments. Both the simulation and the laboratory results showed that magnesium in the mine water was maintaining sulphate in a soluble form as magnesium sulphate (MgSO4) at pH 9.6. Thus magnesium was preventing the removal of sulphate as gypsum (CaSO4·2H2O). However, change in the lime precipitation pH from 9.6 to 12.5 resulted in magnesium hydroxide (Mg(OH)2) precipitation and improved sulphate removal. Additionally, magnesium hydroxide could act as seed crystals for gypsum precipitation or co-precipitate sulphate further enhancing the removal of sulphate from mine water.

The aim of this research was to investigate whether by-products from quicklime manufacturing could be used instead of commercial quicklime (CaO) or hydrated lime (Ca(OH)2), which are traditionally used as neutralization chemicals in acid mine drainage treatment. Four by-products were studied and the results were compared with quicklime and hydrated lime. The studied by-products were partly burnt lime stored outdoors, partly burnt lime stored in a silo, kiln dust and a mixture of partly burnt lime stored outdoors and dolomite. Present application options for these by-products are limited and they are largely considered waste. Chemical precipitation experiments were performed with the jar test. All the studied by-products removed over 99% of Al, As, Cd, Co, Cu, Fe, Mn, Ni, Zn and approximately 60% of sulphate from acid mine drainage. However, the neutralization capacity of the by-products and thus the amount of by-product needed as well as the amount of sludge produced varied. The results indicated that two out of the four studied by-products could be used as an alternative to quicklime or hydrated lime for acid mine drainage treatment.

The main goal of this research was to investigate the possibility of the utilization of carbon residue from biomass gasification process with and without chemical activation as a low cost sorbent for iron(II), copper(II) and nickel(II) ions from an aqueous solution. Commercial activated carbon was used as a reference sample. Batch experiments were done to evaluate the influence of pH, initial metal concentration and contact time. The optimum pH required for maximum adsorption was found to be 4, 5 and 8, for iron, copper and nickel, respectively. According to the results, the removal of metals by carbon residue with and without chemical activation was higher than commercial activated carbon. The highest maximum experimental sorption capacities ( q m ,exp ) for iron, copper and nickel by activated carbon residue were 21, 23 and 18 mg g −1 , respectively. The experimental equilibrium sorption data were tested for the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) equations. Depending on the system the Langmuir or Freundlich isotherms have been found to provide the best correlation. The kinetics of iron, copper and nickel sorption by different adsorbent materials followed the pseudo-second-order model. Other tested kinetic models were the pseudo-first-order and the Elovich models. Weber Morris's intraparticle diffusion model showed that there are two or three different stages for the removal of metals.

Organic compounds decomposing in high temperature and pressure of a steam boiler plant water–steam cycle result in low molecular weight (LMW) organic acids and carbon dioxide. Subsequently a drop of pH value is observed in condensate which ultimately can cause corrosion. Organics may also contain for example chloride and release it to condensate. Thirdly decomposition products mask online cation conductivity measurements. This paper evaluates the use of activated carbon (AC) filtration as an option to remove the residues of organic compounds present in deionized make-up water. The experimental part was done using continuous flow bench scale AC filters (AC dry volume 3.75 l, flow rate 25 l/h, water temperature approximately 20 °C) at a steam boiler desalination plant. Four commercial ACs were tested and all proved equally efficient removing approximately 42–45% of total and 58–68% of dissolved organic carbon after 30 days of operation. The most efficiently removed organic fractions were LMW neutral compounds, decomposition products of humic substances and hydrophobic compounds. Biopolymers were not effectively removed. Coconut shell based ACs leached more Ca, Mg and Na ions compared to coal based while for silica there were no differences. Pre-acid washing of ACs was efficient in reducing the initial leaching of impurities. However, the differences between acid washed and non-acid washed AC diminished with time. A mixed bed (MB) ion exchanger as a polishing treatment after AC filters is required to control the leaching of impurities.

Interactions of aluminium (1 mM) and silicon (0.1–2 mM) in aqueous solutions were studied at a low ionic strength medium representing fresh water and water treatment process environments, attempting to quantify elemental relationships of the formed precipitates as well as their surface charge properties with a novel combination of analytical techniques. FESEM analyses showed that the Al:Si ratio in the obtained precipitates was clearly affected by the Al:Si ratio in the initial aqueous solution. According to XRD, the precipitates originated from the 1 mM Al and the 1 mM Al + 0.1 mM Si solutions were gibbsite, while for the initial Al:Si ratios equalling to 1:0.5 or higher, only amorphous material was precipitated. Zeta potential decreased as a function of the initial silicon content, and reached negative values at pH 6.2 with the initial concentrations of 1 mM Al + 2 mM Si. In contrast, for the total surface charge, a maximum value was found between pH 4.5 and 5, and it clearly decreased with the amount of silicon present. To conclude, the dissolved silicon had a significant effect on the formation of charged aluminium species. This may have considerable environmental and health effects. A reaction mechanism for the formation of hydroxyaluminosilicates from silicic acid and aluminium hydroxide was proposed.

An evaluation was made of the performance of a commercial industrial-scale ultrafiltration (UF)-based process for treatment of highly concentrated oily wastewaters. Wastewater samples were gathered from two plants treating industrial wastewaters in 2008, and in 2011 (only from one of the plants), from three points of a UF-based treatment train. The wastewater samples were analyzed by measuring the BOD7, COD, TOC and total surface charge (TSC). The inorganic content and zeta potentials of the samples were analyzed and GC-FID/MS analyses were performed. The removal performances of BOD7, COD, TOC and TSC in 2008 and 2011 for both plants were very high. Initial concentrations of contaminants in 2011 were lower than in 2008, therefore the COD and TSC reductions were also lower in 2011 than three years before. Regardless of the high performance of UF-based processes in both plants, at times the residual concentrations were considerable. This could be explained by the high initial concentrations and also by the presence of the dissolved compounds that were characterized. Linear correlation was observed between COD and TOC, and between COD and TSC. The correlation between COD and TSC could be utilized for process control purposes.

During the last two decades, and particularly during the last few years, the environmental sector has shown a largely growing interest in the treatment of different types of water and wastewater by electrocoagulation (EC). The aim of this work was to review studies, conducted mainly during 2008-2011, on the wide and versatile range of feasible EC applications employed in the purification of different types of water and wastewater. The EC applications discussed here were divided into 7 following categories: tannery, textile and colored wastewater; pulp and paper industry wastewater; oily wastewater; food industry wastewater; other types of industrial wastewater; surface water as well as model water and wastewater containing heavy metals, nutrients, cyanide and other elements and ions. In addition, this paper presents an overview of the optimum process conditions (treatment times, current densities, and initial pH) and removal efficiencies (mostly high) achieved for the EC applications discussed. In the vast majority of the studies discussed in this review, the aforementioned values were found to be in the range of 5 - 60 min (typically less than 30 min), 10 - 150 A/m 2 and near neutral pH, respectively. Both operating costs and electrical energy consumption values were found to vary greatly depending on the type of solution being treated, being between 0.0047 - 6.74 €/m 3 and 0.002 - 58.0 kWh/m 3 , but in general they were rather low (typically around 0.1 - 1.0 €/m 3 and 0.4 - 4.0 kWh/m 3

The aim of this research was to investigate sulphate removal from mine water by precipitation as ettringite (Ca6Al2(SO4)3(OH)12·26H2O) and the utilisation of the precipitate as a sorbent for arsenate removal. The mine water sulphate concentration was reduced by 85–90% from the initial 1400 mg/L during ettringite precipitation depending on the treatment method. The precipitation conditions were also simulated with MINEQL + software, and the computational results were compared with the experimental results. The precipitated solids were characterised with X-ray diffraction and a scanning electron microscope. The precipitated solids were tested as sorbents for arsenate removal from the model solution. The arsenic(V) model solution concentration reduced 86–96% from the initial 1.5 mg/L with a 1 g/L sorbent dosage. The effect of initial arsenate concentration on the sorption of arsenate on the precipitate was studied and Langmuir, Freundlich, and Langmuir-Freundlich sorption isotherm models were fitted to the experimental data. The maximum arsenate sorption capacity (qm = 11.2 ± 4.7 mg/g) of the precipitate was obtained from the Langmuir-Freundlich isotherm. The results indicate that the precipitate produced during sulphate removal from mine water by precipitation as ettringite could be further used as a sorbent for arsenate removal.

Ab initio molecular dynamics (AIMD) based on density functional theory has been used to study small aluminium–oxygen complexes in water. Such Al–O clusters have been seen in several recent mass spectrometry studies. In this study, we have focused on trimeric Al–O clusters. The initial very compact trimeric Al–O structures opened up and formed linear Al–O chains. The typical Al–O coordination number in these chain structures was 5. We have performed long (up to 200 ps) AIMD simulations and these chain structures are stable on the nanosecond time scale. We have also studied the reactivity of the Al–O dimer and solvated Al. We found a formation path for the trimeric cluster, which has a action barrier (0.04 eV) and a reaction free energy of − 0.55 eV. This suggests that the association of a dimer and a monomer Al–O species is fast and thermodynamically a very favourable process.

Electrocoagulation (EC) test runs of oil-in-water (O/W) emulsions (0.6% and 2%) prepared from bio oils and synthetic oils with stainless steel (SS) or aluminum (Al) anode were performed in a batch mode with a novel bench scale EC apparatus. The efficiency of EC for breaking O/W emulsions was evaluated versatilely by measuring COD, TOC, total surface charge (TSC) and turbidity. Particle sizes with laser diffraction and BOD were also measured for a number of test runs. The turbidity of the studied emulsions decreased the most, between 75% and 100% whereas COD, TSC and TOC reductions were in the range of 25–95%, 40–98% and 20–75%, respectively. The most successful reductions were measured for tall oil and synthetic oil emulsions. BOD values were also found to decrease during test runs. Laser diffraction measurements proved that the emulsification of the oils, as well as the breaking of the emulsions, were both successful. There was no significant difference between treatment results when using a SS or Al anode. However the sludge produced using a SS anode was substantially thicker in structure and thus easier to separate. To summarize, the EC of O/W emulsions studied in this work was found to be cost-effective and feasible even without specific optimization of the process parameters.

In this study a novel coagulant, aluminium formate, was synthesised and its coagulation performance was evaluated. Aluminium formate can be synthesised from aluminium hydroxide and formic acid at atmospheric pressure and at a temperature of 60 °C. The speciation of the products obtained was studied using electrospray ionisation mass spectrometry. Aluminium formate was found to form mainly small cationic species in water. The coagulation performance was studied in removal of natural organic matter from surface water. Polyaluminium chloride and aluminium sulphate were used as reference coagulants. The results suggest that aluminium formate removes natural organic matter at least as well as the reference coagulants. Raw water characteristics were found to have an impact on the coagulation efficiency of the coagulants studied. Aluminium formate was found to be a potential water treatment chemical for applications where conventionally used coagulants cause problems.

The manometric respirometric method was applied to a characterisation of organic material in pulp and paper mill wastewater, which is usually high in organic content and inhibitory substances. Preliminary tests, including experiments with an extra microbial seed as well as dilution series, were carried out before the characterisation analyses in order to optimise the method. Three different physical-chemical methods were then used to characterise organic fractions. Influent organic fractions were specified with two methods in which the determination of the soluble biodegradable and the soluble inert fraction differed. In the third method, the influent fractions as well as the new metabolic products generated during the biodegradation process and an estimate of the mineralised part of the influent biodegradable fraction were determined without any hypothetical conversion factors. The results showed that a remarkable part of the detected oxygen demand was consumed for the biotransformation of biodegradable fractions into new inert organic products, not only for mineralisation. The amount of these new metabolic products, measured after biochemical oxygen demand analyses, was significant. It was also noticed that volatile organic compounds can have an influence on the chemical oxygen demand value of effluents.

A five-stage sequential extraction procedure was used to determine the distribution of 11 metals (Cd, Cr, Cu, Mo, Pb, Zn, As, Co, V, Ni, Ba), and sulphur (S) in bottom ash and in fly ash from a fluidized bed co-combustion (i.e. wood and peat) boiler of Stora Enso Oyj Oulu Mill at Oulu, Northern Finland, into the following fractions: (1) water-soluble fraction (H2O); (2) exchangeable fraction (CH3COOH); (3) easily reduced fraction (NH2OH—HCl); (4) oxidizable fraction (H2O2 + CH3COONH 4); and (5) residual fraction (HF + HNO3 + HCl). Although metals were extractable in all fractions, the highest concentrations of most of the metals occurred in the residual fraction. From the environmental point of view, this fraction is the non-mobile fraction and is potentially the least harmful. The Ca concentrations of 29.3 g kg—1 (dry weight) in bottom ash and of 68.5 g kg— 1 (dry weight) in fly ash were correspondingly approximately 18 and 43 times higher than the average value of 1.6 g kg— 1 (dry weight) in arable land in Central Finland. The ashes were strongly alkaline pH (∼ 12) and had a liming effects of 9.3% (bottom ash) and 13% (fly ash) expressed as Ca equivalents (dry weight). The elevated Ca concentrations indicate that the ashes are potential agents for soil remediation and for improving soil fertility. The pH and liming effect values indicate that the ashes also have a pH buffering capacity. From the environmental point of view, it is notable that the heavy metal concentrations in both types of ash were lower than the Finnish criteria for ash utilization.

Pulp and paper mill wastewater was characterizated, before (influent) and after (effluent) biological wastewater treatment based on an activated sludge process, by microfiltration (8, 3, 0.45 and 0.22microm) and ultrafiltration (100, 50, 30 and 3kDa) of the wastewater samples into different size fractions. Various parameters were measured on each fraction: molecular weight distribution (MWD) using high performance size exclusion chromatography (HPSEC), total organic carbon (TOC), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus (Tot-P), phosphate phosphorus (PO(4)-P), electrical conductivity, pH, turbidity, charge quantity and zeta potential. The MWD, TOC and COD(Cr) results indicated that the majority of the material present in both the influent and effluent was in the medium molecular weight (MW) range (i.e. MW10kDa) with three main MW sub-fractions. There were no significant differences in the range of the MWD between the influent and effluent samples. The magnitude of the MWD in the effluent was about one half that in the influent, the greatest reduction being in the 6kDa fraction. The 3kDa fractions of both the influent and effluent showed a considerable increase in BOD(7), probably due to the removal of compounds harmful to bacteria in 3kDa ultrafiltration. Influent turbidity decreased considerably in microfiltration (8-0.22microm). As the turbidity was removed by 0.22microm filtration, the anionic charge quantity started to decrease. Particles in the influent and effluent contained 19-29% and 14-20% of the total phosphorus, respectively. The major phosphorus fraction was in the form of soluble phosphate.

An online high temperature capillary electrophoresis instrument (HotUCE), a potentiometer and an ion chromatograph were used in studies on corrosive ions and changes in potential at normal pulping process temperatures in experimental liquors modelling pulp cooking processes at mills. The aim was to evaluate the stress corrosion cracking (SCC) susceptibility of stainless steels. The HotUCE instrument and the potentiometer were online coupled with an autoclave, where welded duplex stainless steel samples were immersed for 500 h in simulated high ionic strength hot black liquor (HBL), hot white liquor (HWL) or green liquor (GL) at 130, 150 or 170 °C, respectively. The results showed that only minor amounts of oxidized sulphur compounds were formed. The concentrations of corrosive sulphur anions were calculated against sulphur standards. Amounts of sulphur species in the liquor correlated with the changes in the potential of the duplex stainless steel specimens during the cooking experiments. The formation of sulphite during cooking was greater in HWL than in HBL. Changes in the potential showed that reduction processes occurred during the SCC tests. The results indicate that the SCC risk is enhanced at higher temperatures, probably, due to the increased formation of thiosulphate.

In this biological oxygen demand (BOD) study, the manometric respirometric BOD OxiTop® method was used to monitor the biodegradation of two summer grade (SFO 1 and 2) and two winter grade light fuel oils (WFO 1 and 2) in OECD 301 F conditions, in groundwater, and in two different Finnish forest soils (mineral-poor and mineral-rich). The biodegradation measurements in the OECD 301 F conditions were carried out in two nutrient solutions for 28 days. In both solutions WFO 1 reached the highest biodegradation degree, 32% in the solution OECD 301 F, and 70% in a solution containing additional ammonium chloride. In groundwater conditions all the biodegradation degrees of fuel oils remained below 2% within the 28-day period. SFO 1 reached the highest 30 day biodegradability (4%) in mineral-poor soil, 18% in mineral-rich soil. In a 189-day measurement in a mineral-rich soil, the biodegradation degree for the SFO 1 was 94%. The manometric respirometric method proved to be a very suitable and practicable measurement method for the purpose of biodegradation studies of highly volatile light fuel oils, because in this method samples are treated to a lesser degree than in conventional methods, and dilutions are not needed. Results also indicated a considerable effect of conditions on the biodegradability in both water and soil environments. The results of these biodegradation studies could be used when planning in situ treatment methods based on natural biodegradation. In situ treatment methods are eco-efficient, and are especially suitable for sparsely populated sites.

The purpose of this research was to investigate the effectiveness of short-chain cationic polyelectrolytes of different molecular weights and charge densities in reducing turbidity and selectively removing toxic wood extractives from chemical birch pulp filtrate. The effects of chemical type, dosage and temperature were of interest. An effective performance was achieved with a copolymer of acrylamide and methacrylate of medium molecular weight and medium charge density at 72 °C and pH 5–6. The dosage range optimum for reducing the turbidity was 102–142 mg/L. Up to 92% of the wood extractives was selectively removed.

Properties of water treatment chemicals were investigated by a novel combination of analytical methods. Oligomer distribution, total surface charge, zeta potential and conductivity were evaluated in simulated systems containing highly and moderately basic polyaluminium chlorides, aluminium sulfate (alum), ferric chloride and ferric sulfate. Species were quantified on the basis of mass spectro-metric results. Polyaluminium chemicals gave rise to an intensive and completely cationic distribution of mainly Al13-based oligomers and high surface charges. Both cationic distribution and charge decreased with increase of pH and increased with concentration of the chemical. The other chemicals produced a wider oligomeric distribution of smaller species, including anions. The dimeric form was typical for iron. In the case of the sulfate-containing chemicals, sulfate was present in the majority of oligomers and zeta potentials were stable. For the chemicals without sulfate, pH values needed to be high enough...

Multimodal zeta potential distribution in chemical birch pulp process water was studied by filtrating the water into fractions and subsequently measuring zeta potential, charge quantity, turbidity and organic substances. Filtrations were made using 12 microm, 1.6 microm, 1.2 microm, 0.45 microm and 0.1 microm membranes. The number of populations with different zeta potentials diminished with filtration. With the unfiltrated water, 12 microm and 1.6 microm filtrates, three or four different zeta potentials were observed. When the filtration was performed with a 1.2 microm membrane or smaller, only two populations of different zeta potentials were detected. The charge quantity steadily approached zero from unfiltrated water towards a 1.6 microm fraction filtrate. After that, it remained constant. Turbidity constantly decreased when using smaller membranes. The amount of wood extractives decreased to half with 0.1 microm filtration. No significant difference in the amount of carbohydrates and lignin between the filtrated fractions and the unfiltrated water was detected. A comparison dealing with particle size analysis between two different apparatuses was also made.

Hydrolysis and speciation of aluminium sulfate octadecahydrate Al 2 ( SO 4 ) 3 · 18 H 2 O was studied by electrospray time of flight mass spectrometry (ESI TOF MS). Several novel polymeric species were determined. Highly charged polymers, characterized by other methods, such as the Keggin cation [Al13O4(OH)24(H2O)12]7+ and the octameric aluminium hydroxide cluster [Al8(OH)14(H2O)18](SO4)5 16H2O, were found using ESI-MS as the anions [Al13O4(OH)25(SO4)4]2− and [Al8O(OH)14(SO4)5(H2O)4]2−. All the main species identified contained sulfate or hydrogen sulfate. The compositions of the determined ions mimicked those of several stable mineral forms.

The mining industry is a major contributor of various toxic metals and metalloids to the aquatic environment. Efficient and economical water treatment methods are therefore of paramount importance. The application of natural or low-cost sorbents has attracted a great deal of interest due to the simplicity of its process and its potential effectiveness. Geopolymers represent an emerging group of sorbents. In this study, blast-furnace-slag and metakaolin geopolymers and their raw materials were tested for simultaneous removal of Ni(II), As(III) and Sb(III) from spiked mine effluent. Blast-furnace-slag geopolymer proved to be the most efficient of the studied materials: the experimental maximum sorption capacities for Ni, As and, Sb were 3.74 mg/g, 0.52 mg/g, and 0.34 mg/g, respectively. Although the capacities were relatively low due to the difficult water matrix, 90–100% removal of Ni, As, and Sb was achieved when the dose of sorbent was increased appropriately. Removal kinetics fitted well with the pseudo-second-order model. Our results indicate that geopolymer technology could offer a simple and effective way to turn blast-furnace slag to an effective sorbent with a specific utilization prospect in the mining industry.

The use of organic peracids in wastewater treatment is attracting increasing interest. The common beneficial features of peracids are effective anti-microbial properties, lack of harmful disinfection by-products and high oxidation power. In this study performic (PFA), peracetic (PAA) and perpropionic acids (PPA) were synthesized and compared in laboratory batch experiments for the inactivation of Escherichia coli and enterococci in tertiary wastewater, oxidation of bisphenol-A and for corrosive properties. Disinfection tests revealed PFA to be a more potent disinfectant than PAA or PPA. 1.5 mg L(-1) dose and 2 min of contact time already resulted in 3.0 log E. coli and 1.2 log enterococci reduction. Operational costs of disinfection were estimated to be 0.0114, 0.0261 and 0.0207 €/m(3) for PFA, PAA and PPA, respectively. Disinfection followed the first order kinetics (Hom model or S-model) with all studied peracids. However, in the bisphenol-A oxidation experiments involving Fenton-like conditions (pH = 3.5, Fe(2+) or Cu(2+) = 0.4 mM) peracids brought no additional improvement to traditionally used and lower cost hydrogen peroxide. Corrosion measurements showed peracids to cause only a negligible corrosion rate (

This study presents a simple method for metal re-coating of silica optical fibre Bragg gratings. No vacuum techniques or any high-temperature methods such as dip or melt coating techniques are required. Optical fibres with metallic coatings such as aluminium, copper, tin and gold are commercially readily available. These coatings are usually applied in connection with the fibre drawing process, and these coating techniques cannot be used for coating existing fibres. Bragg-gratings are often written into the optical fibre after the original coating has been removed and therefore the fibre needs to be re-coated subsequent to the writing process in order to protect the fibre. Since no company providing metallic re-coating services was located, the coating process had to be developed. Researchers developing for instance high-temperature fibre optical Bragg-grating sensors will need a simple and cheap method for metal coating of fibres. The coating method presented in this work is developed with emphasis to further embedding the coated fibres into solid metal using, for example, vacuum brazing techniques. The method is based on electroplating, and therefore, the fibres can be coated with any metal or metal alloy applicable by this technique.

Hydrolysis of 0.100, 0.010, and 0.001 mol L−1 aqueous solutions of AlCl3·6H2O, each at two pH values ranging from 3.27 to 7.00, was compared by electrospray ionization time-of-flight mass spectrometry. The differences between 4 h and 14 day aged solutions were also studied. Various charges and compositions for species of the same size were observed. At lower pH values, dimeric and trimeric aluminium oxo-hydroxo-complexes were the major molecular species. With higher pH levels, precipitation and formation of took place. Multiple charged signals assigned to polynuclear complexes (Al10–Al15) were found at a narrow pH area range before precipitation occurred. The diversity of different species increased strongly as a function of concentration. The pH of the solution dominated the profile even more than the concentration. All the main species were formed in 4 h.

The hydrolysis reactions of FeCl3 in 0.1 mM aqueous solutions were monitored by electrospray ionisation time-of-flight mass spectrometry (ESI-ToF-MS). In contrast to the other ionisation techniques, electrospray ionisation provides information on the composition of the elemental cores even in water and salt cluster ions. Therefore, the technique facilitates detection of the bonding of the chloride ions in the oxo-hydroxo-iron cores. A variety of mononuclear and polynuclear iron-oxohydroxo-chloride complexes were characterised from the cationic and anionic mass spectra of iron(III) solutions. Oxidation and reduction reactions of iron, as well as competition between OH- and Cl- ions within one iron core, were also observed.

The biological oxygen demand (BOD) test is widely used in many wastewater treatment plants. The conventional BOD tests are usually time-consuming and the results are often out of date for process control purposes. The aim of this research was to compare the manometric respirometric test with common chemical methods in the determination of BOD of wastewater from a pulp and paper mills as well as to evaluate theBOD7values of both wastewaters from the short-term respirometric measurements. The results showed that there were differences in theBOD7values of paper mill samples measured by conventional and respirometric methods. The main cause was found to be the dilution solution used in the conventional BOD tests. Using the same mineral solution in the respirometric measurements diminished the difference remarkably. Evaluation of theBOD7value after two or three days incubation was proved to work very well and the estimated results were close to measured values (deviations 1%–12%).

A five-stage sequential leaching procedure was used to determine the distribution of 11 metals (Cd, Cu, Pb, Cr, Mo, Zn, As, Co, V, Ni, Ba), and sulfur (S) in bottom ash and in fly ash from a fluidized bed co-combustion (i.e. wood and peat) boiler of a municipal district heating plant at Oulu, Northern Finland, into the following fractions: (1) water-soluble fraction (H2O), (2) exchangeable fraction (CH3COOH), (3) easily reduced fraction (NH2OH-HCl), (4) oxidizable fraction (H2O2 + CH3COONH4), and (5) residual fraction (HF + HNO3 + HCl). Although the metals were leachable in all fractions, the highest concentrations of most of the metals occurred in the residual fraction. This kind of strong mineral acid mixture can never be found in nature, and therefore the residual fraction is not likely to be dissolved easily in the environment. The ashes were strongly alkaline (pH 9.1) and had a liming effect (i.e. neutralizing value) of 3.7% (bottom ash) and 7.1% (fly ash) expressed as Ca equivalents (dry wei...

Earlier characterization of some hydrolysis products of AlCl3·6H2O was confirmed by electrospray ionization tandem mass spectrometry with increasing collision energy of projectile ions. At lower collision energies, the aqua ligands were stripped off. At higher energies, two hydroxo groups formed a bridging oxo group with loss of one water molecule. Aluminum complexes could also capture aqua ligands in the collision chamber so long as the parent ion did not fragment, and the fragment ion spectra broadened toward higher m/z values. The chloro ligands were eliminated as hydrochloric acid. The aluminum cores remained highly intact. Copyright © 2004 John Wiley & Sons, Ltd.

A simple and rapid, on-line compatible chelation pretreatment method to leach technically notable metals, especially manganese, from pulp matrix to aqueous phase for ICP-AES analysis has been developed. DTPMP was found to be the best chelating agent. Mn was leached almost quantitatively (>95%) and good recoveries were also obtained for Ba, Mg and Zn. Recoveries of Al and Fe were 15–40% and 40–60%, respectively—depending on the pulp type. Optimum contact time was 15 mins and optimum temperature 85 °C. For the 11 elements studied, the quantification limits range from 0.05mg/kg pulp (Mn) to 2.1 mg/kg pulp (Al). The repeatability and reproducibility range from 0.3% (Ca, Mn) to 11% (Cu) and from 1.7% (Mg) to 15% (Cu), respectively. The ruggedness of the method against different pulp matrices was good.

Uniform corrosion of titanium was studied in alkaline hydrogen peroxide environments simulating pulp bleaching conditions. Corrosion rates of unalloyed Grade 2 and alloyed Grade 5 were determined as a function of hydrogen peroxide anion (HOO−) concentration. Influences of calcium and silicate inhibitors and iron and manganese were investigated. Without inhibition titanium corroded at HOO− content of 200 mg/l: Grade 2 0.4 mm/y and Grade 5 1.4 mm/y. Addition of calcium (Ca2+) and silicate (SiO32−) diminished the corrosion of Grade 2 to critical anion level 400 mg/l, but could not protect Grade 5 even at the HOO− concentration of 300 mg/l. Presence of iron and manganese raised the critical levels of the both grades. High HOO− anion level was observed as a notable potential difference between titanium and platinum. Gleichmasige Flachenkorrosion von Titan unter alkalischen Wasserstoffperoxidbedingungen: Einfluss der Ubergangsmetalle und der Inhibitoren Kalzium und Silikat Gleichmasige Flachenkorrosion von Titan wurde in alkalischen Wasserstoffperoxidbedingungen, die Papierbleichbedingungen simulieren, untersucht. Die Korrosionsgeschwindigkeiten von unlegierter Guteklasse 2 und legierter Guteklasse 5 wurden als Funktion der Wasserstoffperoxidanionen(HOO−)konzentration bestimmt. Einflusse von Kalzium- und Silikatinhibitoren sowie von Eisen und Mangan wurden untersucht. Ohne Inhibierung betrug die Korrosion von Titan bei einem HOO−-Gehalt von 200 mg/l bei der Guteklasse 2 0,4 mm/Jahr und bei der Guteklasse 5 1,4 mm Jahr. Die Zugabe von Kalzium (Ca2+) und Silikat (SiO32−) verminderte die Korrosion der Guteklasse 2 auf ein kritisches Anionenniveau von 400 mg/l; konnte aber Guteklasse 5 selbst bei einer HOO−-Konzentration von 300 mg/l nicht schutzen. Die Anwesenheit von Eisen und Mangan erhohte die kritischen Niveaus fur beide Guteklassen. Hohe HOO−-Anionengehalte wurden als betrachtliche Potentialdifferenz zwischen Titan und Platin beobachtet.

Biodegradation of different tall oil soaps was studied in order to examine the behaviour of these bioproducts in natural environments and to study their biodegradation rates. The rates of biodegradation were studied by modelling the biodegradation phenomenon as a pseudo-first-order reaction. Biodegradation was studied in seven different environments. Four of these were water phases: groundwater in aerobic and anaerobic conditions, river water and Office of Environmental Compliance and Documentation (OECD) 301 F standard conditions. In addition, three solid phases, sand, acidic forest soil and topsoil, were used as a solid matrix. The results showed that the matrix and the concentration had a strong effect on both the rate and degree of the biodegradation reaction. As a result, all of the tall oil soaps were about 57–85 % biodegradable in OECD 301 F conditions, but only moderately biodegradable in Finnish river water taken in the summer. When compared to the sample taken in the autumn, the biodegradation degree was considerably higher. In groundwater, biodegradation degree was low, even negligible in anaerobic conditions. With ten times less sample content, the biodegradation degrees in groundwater and surface water increased to 60 % for all the tall oil soaps, with one soap, in particular, up to 80 % during 100 days of measurement. In the topsoil, biodegradation was vague, and in slightly acidic forest soil, the decomposition reactions were complex. This is probably due to gas formation in the side reactions. In sand, tall oil soaps did not biodegrade at all.

Peracetic acid (PAA) has been studied for wastewater disinfection applications for some 30 years and has been shown to be an effective disinfectant against many indicator microbes, including bacteria, viruses, and protozoa. One of the key advantages compared to, e.g., chlorine is the lack of harmful disinfection by-products. In this paper a pilot-scale study of PAA-based disinfection is presented. Indicator microbes (E. coli, total coliforms and coliphage viruses) as well as chemical parameters (pH, oxidation-reduction potential (ORP), chemical and biochemical oxygen demand (COD and BOD), and residual PAA and hydrogen peroxide) were studied. The main aim of this investigation was to study how these selected chemical parameters change during PAA treatment. Based on the results, disinfection was efficient at C·t values of 15 to 30 (mg·min)/l which equals to a PAA dose of 1.5 to 2 mg/l and a contact time of 10 to 15 min. In this concentration area changes in pH, COD and BOD were negligible. However, hydrogen peroxide residues may interfere with COD measurements and apparent COD can be higher than the calculated theoretical oxygen demand (ThOD). Additionally PAA or hydrogen peroxide residues interfere with the BOD test resulting in BOD values that are too low. Residual PAA and ORP were found to correlate with remaining amounts of bacteria. Keywords : tertiary wastewater disinfection, peracetic acid, total coliform, E. coli , coliphages

The adsorption of Ethylenediaminetetraacetic acid (EDTA) and its metal complexes, Cu, Fe(III), Hg, Mn and Ni, onto lake sediment was studied. The results reveal that EDTA and metal–EDTA complexes, even though being hydrophilic compounds, are indeed adsorbed within one months' contact time to some extent (6.3–24.8%). Less than 10% of Ni–EDTA, Cu–EDTA and EDTA salt was adsorbed, while the mass amount of Mn–EDTA, Hg–EDTA and Fe(III)–EDTA found in sediment exceeded 15% after the contact period. Thus, adsorption of metal–EDTA chelates might be a relevant process in their removal from the aquatic environment. The metal–EDTA chelates in aqueous and solid phases were determined by gas chromatography–nitrogen phosphorus detection (GC–NPD) system. The complexes were extracted by phosphate solution prior to analysis. The ability of EDTA to desorb adsorbed heavy metals from sediments is also discussed.

A rapid X-ray fluorescence addition method has been developed for quantification of the technically most important metals in wood pulp matrix (Mn, Fe, and Cu). Pretreatment consisted of just two steps: first, acid was added to the sample to achieve homogeneous distribution of the metals; the pulp was then pressed lightly on to Mylar film. Total analysis time was less than 10 min. The concentration range investigated was up to 15 mg kg–1 for Mn and up to 5 mg kg–1 for Fe and Cu. Metal concentrations in Scandinavian pulps are not expected to exceed these amounts. The quantification limit was 2 mg kg–1 for all three metals. The reproducibilities and repeatabilities were concentration-dependent and varied between 3 and 19% and between 1 and 17%, respectively. The squares of the linear correlation coefficients between measured intensity and added metal concentration were 0.994, 0.950, and 0.932 for Mn, Fe, and Cu, respectively.