Search results for "Environmental engineering"
showing 10 items of 2674 documents
Radiation model of a TiO2-coated, quartz wool, packed-bed photocatalytic reactor
2010
The radiation field of a packed-bed photocatalytic reactor filled with quartz wool coated with titanium dioxide was modeled using the Monte Carlo technique and the following information: the radiation flux emitted by the lamps, the diameter size distribution of the quartz fiber cloth, the mass of quartz fibers and of TiO2 that was immobilized on the fiber surface as well as the refractive index and the spectral absorption coefficient of the materials of the system. Modeling predictions were validated with radiometer measurements of the transmitted radiation through the reactor, the root mean square error being < 9.7%. Finally, by means of a parametric study, the validated model was used to …
Design for recyclability and the avoidance of waste: the case of printed paper in Germany
1999
This paper discusses the generation of process waste in printed paper recycling and some factors affecting the amount of de-inking waste. The effects on waste generation by paper grades, which are designed for improved recyclability, are pointed out. The amount of waste generated is considered as the improvement in recyclability. This corresponds to a reduction in the use of materials that cannot be recycled, which, in the case of paper means lowering their mineral content. Two scenarios of a dynamic model of the fluxes of printed paper in Germany between 1993 and 2000 are used to analyse the amount of waste generated. No product changes are assumed in the first scenario, whereas improved …
Biodeterioration of cardboard-based liquid containers collected for fibre reuse.
1999
Liquid packaging board (LPB) collected in Germany is processed in Finland as recycled fibre and as plastic reject for incineration. The chemical, biological and physical changes occurring in recycled LPB bales were monitored during storage of six and 18 months. The moisture content in the core of the bales ranged from 7% to 53%, and pH values varied from 6.0 to 8.5. The average amount of mesophilic bacteria per container was 1.5 x 10(7) - 5 x 10(8), which means that recycled LPB pulp cannot be recommended for sanitary use. The concentration of CO2 inside the bale is an indicator of the activity of aerobic microorganisms and might be suitable for identifying deteriorated bales and removing t…
Pyrolysis-GC-MS and CuO-oxidation-HPLC in the characterization of HMMs from sediments and surface waters downstream of a pulp mill
1998
Abstract High molecular mass fractions of lignin and humic compounds in sediments and waters downstream of a pulp mill were characterized applying pyrolysis-gas chromatography-mass spectrometry. The results were compared to those obtained using reversed phase HPLC on the cupric oxide oxidation products. The chromatographic data of both pyrolysis and cupric oxide oxidation were also subjected to the principal component analysis (PCA). The sediment samples and fractions obtained by ultrafiltration of river water samples were freeze dried prior to characterization. The sediment samples were also extracted using 2 M sodium hydroxide solution. The extracts were ultrafiltrated, freeze dried and c…
Identification of lipophilic pollutants discharged from a Finnish pulp and paper mill.
1998
Lipophilic organic compounds originating from kraft pulping and papermaking were identified by straight gas chromatography/mass spectrometry (GC/MS) analyses. Samples analyzed included a primary clarifier effluent (PE) and a secondary clarifier effluent (SE) from the activated sludge treatment plant of a Finnish ECF-bleached (Elementally Chlorine Free) kraft pulp and paper mill. Liquid-liquid extraction composition of PE was compared with solid phase extraction (SPE) and dialysis of a semipermeable membrane device (SPMD) exposed to PE. Dichloromethane extracts of particulate material isolated from PE, sludges from both the primary and secondary clarifier, a sediment collected in the vicinit…
Photoinduced toxicity of retene to Daphnia magna under enhanced UV-B radiation.
2001
Abstract The effects of UV radiation on the acute toxicity of retene (7-isopropyl-1-methylphenanthrene) to Daphnia magna Straus were studied. Dehydroabietic acid (DHAA) from which retene is formed in the vicinity of pulp and paper industry was also studied. Pyrene, anthracene, and phenanthrene were used as model PAH compounds. The time taken for immobilization (ET50) was monitored under biologically effective UV-B dose rates of 240, 365, 565, and 650 mW m−2 (UV-A and visible light also present). Median effective concentrations (EC50) were determined after a 15-min UV exposure (565 mW m−2) followed by 24 h in the dark. Retene ( 10–320 μg l −1 ) was not acutely toxic in the dark. The inductio…
Thermophilic anaerobic digestion of pulp and paper mill primary sludge and co-digestion of primary and secondary sludge
2012
Anaerobic digestion of pulp and paper mill primary sludge and co-digestion of primary and secondary sludge were studied for the first time in semi-continuously fed continuously stirred tank reactors (CSTR) in thermophilic conditions. Additionally, in batch experiments, methane potentials of 210 and 230 m³CH₄/t volatile solids (VS)(added) were obtained for primary, and 50 and 100 m³CH₄/tVS(added) for secondary sludge at 35 °C and 55 °C, respectively. Anaerobic digestion of primary sludge was shown to be feasible with organic loading rates (OLR) of 1-1.4 kgVS/m³d and hydraulic retention times (HRT) of 16-32 d resulting in methane yields of 190-240 m³CH₄/tVS(fed). Also the highest tested OLR o…
Vertical distribution of AhR-activating compounds in sediments contaminated by modernized pulp and paper industry
2013
Increased ethoxyresorufin-O-deethylase (EROD) activity is a sensitive biomarker of exposure to the chemicals which activate the aryl hydrocarbon receptor (AhR) and induce the cytochrome P450 system, such as many polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs). Pulp bleaching was one of the main sources of PCDDs and PCDFs until elemental chlorine free (ECF) and total chlorine free bleaching processes since 1990s have remarkably decreased but not completely eliminate discharges of these chemicals. In addition, historically contaminated sediments may act as a source of these persistent contaminants. In this study, the contam…
Dissolution of resin acids, retene and wood sterols from contaminated lake sediments.
2005
The dissolution potency of hydrophobic resin acids (RAs), retene and wood sterols from sediments was studied. These wood extractives and their metabolites are sorbed from pulp and paper mill effluents to downstream sediments. With harmful components like these, sediments can pose a hazard to the aquatic environment. Therefore, sediment elutriates with water were produced under variable conditions (agitation rate and efficiency, time), and concentrations of the dissoluted compounds were analyzed. Both naturally contaminated field sediments and artificially spiked sediments were studied. By vigorous agitation RAs can be released fast from the sediment matrix and equilibrium reached within 3 d…
Potential of interactive multiobjective optimization in supporting the design of a groundwater biodenitrification process
2019
The design of water treatment plants requires simultaneous analysis of technical, economic and environmental aspects, identified by multiple conflicting objectives. We demonstrated the advantages of an interactive multiobjective optimization (MOO) method over a posteriori methods in an unexplored field, namely the design of a biological treatment plant for drinking water production, that tackles the process drawbacks, contrarily to what happens in a traditional volumetric-load-driven design procedure. Specifically, we consider a groundwater denitrification biofilter, simulated by the Activated Sludge Model modified with two-stage denitrification kinetics. Three objectives were defined (nitr…