Olli Dahl

Utilization of steel, pulp and paper industry solid residues in forest soil amendment: Relevant physicochemical properties and heavy metal availability

Industrial residue application to soil was investigated by integrating granulated blast furnace or converter steel slag with residues from the pulp and paper industry in various formulations. Specimen analysis included relevant physicochemical properties, total element concentrations (HCl+HNO3 digestion, USEPA 3051) and chemical speciation of chosen heavy metals (CH3COOH, NH2OH·HCl and H2O2+H2O2+CH3COONH4, the BCR method). Produced matrices showed liming effects comparable to commercial ground limestone and included significant quantities of soluble vital nutrients. The use of converter steel slag, however, led to significant increases in the total concentrations of Cr and V. Subsequently, total Cr was attested to occur as Cr(III) by Na2CO3+NaOH digestion followed by IC UV/VIS-PCR (USEPA 3060A). Additionally, 80.6% of the total concentration of Cr (370 mg kg(-1), d.w.) occurred in the residual fraction. However, 46.0% of the total concentration of V (2470 mg kg(-1), d.w.) occurred in the easily reduced fraction indicating potential bioavailability.

Heavy metals leaching in bottom ash and fly ash fractions from industrial-scale BFB-boiler for environmental risks assessment

Abstract The bottom ash and fly ash from the co-combustion of wood residues and peat at a bubbling fluidised bed boiler (296 MW) contained only quartz (SiO 2 ), microcline (KAlSi 3 O 8 ) and albite (NaAlSi 3 O 8 ). Thus, X-ray powder diffraction (XRD) was not useful for clarifying the difference in the release of associated heavy metals from ash matrices. In order to assess the release of heavy metals from ashes under changing environmental conditions, they were sequentially extracted and fractionated by the BCR-procedure into acid soluble/exchangeable (CH 3 COOH), reducible (NH 2 OH–HCl) and oxidizable (H 2 O 2 /CH 3 COONH 4 ) phases. The CH 3 COOH extractable fraction in conjunction with the total heavy metals concentrations were used to calculate the risk assessment code values for heavy metals leaching from the ash matrix. The leaching studies indicate that the heavy metals in the bottom ash and fly ash are bound to different fractions with different strengths. From the environmental and utilization perspectives, heavy metals in ashes posed different levels of environmental contamination risk. Only As in the bottom ash posed a very high risk. High risk metals were Cd in the bottom ash as well as As, Cd and Se in the fly ash.

Drying/Fractionation of Deinking Sludge with a High-Velocity Cyclone

Due to the increasing pressure to eradicate solid waste generation, research efforts should be directed toward reducing the volume and increasing the heat value of wastewater treatment sludges with cost-effective and environmentally viable methods. Thus, the potential drying and simultaneous fractionation of deinking sludge was investigated using a high-velocity pilot cyclone dryer. The sludge was processed with an input rate of approximately 500 kg h−1 leading to an increase in the solid content from 67.9 to 96.3–98.9%, indicating very efficient moisture removal. Although the scanning electron microscope (SEM) images supported the removal of fiber/particle adhesion in the processed samples, the process was not effective enough to separate sludge fibers and mineral particles. Additional fractionation would thus be needed to increase the utilization potential of the dried sludge streams.

Social sustainability performance indicators – experiences from process industry

Sustainable industrial development can be advanced through the development and application of sustainability metrics. This study addressed the application of social sustainability metrics to the measurement of sustainability performance within process industry and to metal production at the plant level in particular. The applied social sustainability indicators are one part of the overall sustainability index which aims at presenting a balanced and holistic view of plant-level sustainability performance. Application of plant-level indicators can support informed decision-making and fill in potential gaps in corporate-level assessments and reporting initiatives with respect to plant-level social sustainability performance. The social part of the overall index provides information on both in-plant sustainability performance and on the direct and in-direct impacts of plant operations on the surrounding society with special emphasis on the supply chain and emerging social due diligence aspects. The results of pilot implementation of social indicators in Ruukki Lappohja plant indicated a very high level of social sustainability performance with minor areas of improvement such as social risk management auditing covering the whole supply chain, suppliers communication on social responsibility requirements to workers and sub-suppliers, signing of the code of conduct by employees and reporting on policies on local community relations, safety in supply chain covering suppliers and contractors and factory health and safety performance in relation to average field of industry performance in this field.

Total and extractable heavy metal, phosphorous and sulfur concentrations in slaker grits from the causticizing process of a pulp mill for use as a soil amendment

Abstract The utilization of solid residues allows industry to reduce and recycle waste materials and produce beneficial by-products. The total heavy metal concentrations in slaker grits originating from the chemical recovery process of a pulp mill are lower than the current Finnish statutory limit values for fertilizers used in agriculture and in forestry. In addition, slaker grits are strongly alkaline pH (13.1), have elevated total calcium concentration (331 g kg−1; d.w.), contain calcite (CaCO3), as well as a neutralizing value of 39.4% (Ca equivalents, d.w.). Thus, 0.96 tonnes of slaker grits would be required to replace 1 tonne of a commercial ground limestone product. This indicates that slaker grits have great potential as an industrial residue-based fertilizer and liming agent for use in agriculture and forestry. Since, before such use, it is necessary to assess the mobility of elements in the grits, the three-stage BCR sequential extraction procedure was carried out. Results from sequential extractions showed that the partitioning of Mn (47%), Co (47.1%), Ni (43.1%) and S (94%) was highest in the exchangeable fraction, in which acetic acid (CH3COOH) is used as extractant. The partitioning of Fe (96.5%) and Ti (75.6%) was highest in the easily reduced fraction, in which hydroxylamine hydrochloride (NH2OH–HCI) is used as extractant. The partitioning of Cr (90.8%), V (75.4%), Zn (78.3%), Ba (62.1%), Al (99.4%) and P (99.8%) was highest in the oxidizable fraction, in which hydrogen peroxide (H2O2) is first applied to a heated medium (i.e.85°C) for dissolving organic matter, after which ammonium acetate (NH4COOH) is used as extractant.

Sequential extraction partitioning of metals, sulfur, and phosphorus in bottom ash from a coal-fired power plant

A five-stage sequential extraction procedure was used to determine the partitioning of 16 metals (Cd, Cr, Cu, Mo, Pb, Zn, As, Co, V, Ni, Ba, Al, Be, Fe, Mn, and Ti), sulfur (S), and phosphorus (P) in bottom ash from a coal-fired power plant of Fortum Power and Heat Oy Inkoo Power Plant in southern 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 extractable in all fractions, the highest concentrations of most of the metals occurred in the residual fraction. Although, from the utilization point of view, the total element concentrations in the bottom ash were lower than the current Finnish limit values for fertilizers used in agriculture and in forestry, the partitioning study helps to evaluate the extractability efficiency of different elements. The knowledge of extractability of elements is important if inorganic materials and by-products, e.g. waste, are utilized.

Chemical characterisation of biosludge from a wastewater treatment plant in a neutral sulphite semi-chemical pulp mill by single and sequential extraction of heavy metals and micro-/macronutrients — a case study

The main impetus for utilising the biosludge from the neutral sulphite semi-chemical pulping process is the Finnish legislation which from 1st January 2016 prohibits the deposition of this residue in landfills in Finland. The dry matter content of the biosludge in this case study was low (12.1 mass %), meaning that incineration of this residue is uneconomical. The biosludge was rich in P (6260 mg kg−1). This, together with the high total organic carbon value of 459 g kg−1 and the metal concentrations (As, Cd, Cr, Cu, Ni, Pb, Zn and Hg) lower than the Finnish permissible limits for land application, supports wide and various end-uses for this residue. Except for S (27600 mg kg−1) and Cd (1.4 mg kg−1), the other heavy metal concentrations in the biosludge were lower than the maximum values for heavy metal concentrations in a non-contaminated soil referred to the literature. From the utilisation perspective, and in view of the high levels of S and Na, this residue could efficiently be used, for example, to landscape landfills.

Anaerobic co-digestion of acetate-rich with lignin-rich wastewater and the effect of hydrotalcite addition

The methane potential and biodegradability of different ratios of acetate and lignin-rich effluents from a neutral sulfite semi-chemical (NSSC) pulp mill were investigated. Results showed ultimate methane yields up to 333±5mLCH4/gCOD when only acetate-rich substrate was added and subsequently lower methane potentials of 192±4mLCH4/gCOD when the lignin fraction was increased. The presence of lignin showed a linear decay in methane production, resulting in a 41% decrease in methane when the lignin-rich feed had a 30% increase. A negative linear correlation between lignin content and biodegradability was also observed. Furthermore, the effect of hydrotalcite (HT) addition was evaluated and showed increase in methane potential of up to 8%, a faster production rate and higher soluble lignin removal (7-12% higher). Chemical oxygen demand (COD) removal efficiencies between 64 and 83% were obtained for all samples.

Social metrics in the process industry: Background, theory and development work

Sustainable development as the leading global development paradigm and sustainability as a cornerstone of modern industrial development have guided this development work on social metrics in the process industry. This study addresses the development of social metrics in the process industry and for metal production, in particular, at the plant level. The developed social indicators are one part of the overall sustainability index that aims to present a balanced and holistic view of plant-level sustainability performance, encompassing information on all different dimensions. This development work was preceded by the benchmarking and review of existing global reporting frameworks, initiatives and the literature. Current indicators of industrial sustainability mainly satisfy the needs of corporate-level management and capital investors. Therefore, plant-level indicators are critically needed to support and fill potential gaps in corporate-level assessments and management with a special emphasis on plant-level sustainability. The purpose of our development work for social indicators was to operationalise the concept of sustainability and associated performance measurement at the plant level. The development of social indicators was carried out through workshops with industry partners. As a joint effort, eight core social indicators and their associated sub-indicators were developed. We also report the results of our benchmarking and review of existing frameworks, initiatives and the literature. The social part of the overall sustainability index provides the information on both in-plant sustainability performance and the direct and indirect impacts of plant-level operations on the surrounding society including various stakeholders, interest groups and citizens.

The fundamental phenomena of nanobubbles and their behavior in wastewater treatment technologies

Abstract The importance of nanobubbles is widely acknowledged, particularly in terms of their role with respect to bubble size and stability. Nanobubbles are tiny spherical cap-shaped bubbles, and have several unique physical and mechanical characteristics. Longevity, virtual disappearance of buoyancy, high internal pressure, extremely large surface/volume ratio, high oxygen dissolution rate, and generation of free radicals are the important features of nanobubbles. Their peculiar characteristics have led to many applications in the various fields of science and technology, including industrial, biological, and medical fields. This paper aims to provide a state-of-the-art for nanobubble technology. The fundamentals about existence and stability of nanobubbles are reviewed. Understanding of zeta potential values in nanobubbles is reviewed. The current methods of generation and measurement of nanobubbles are reviewed. Finally, the current applications and promising potential applications of nanobubbles are discussed, such as application of nanobubbles in flotation technology, applications of nanobubbles as cleaning agents and applications of nanobubbles in degradation of organic pollutants. In spite of its fantastic properties, use of nanobubble technology is limited to medical applications. Therefore, the recent developments in nanobubble technology are fascinating and promising but challenging as well.