| 1. |
- Al-Rubaei, Ahmed, et al.
(författare)
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Survey of the operational status of 25 Swedish municipal stormwater management ponds
- 2017
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Ingår i: Journal of environmental engineering. - : American Society of Civil Engineers (ASCE). - 0733-9372 .- 1943-7870. ; 143:6
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Tidskriftsartikel (refereegranskat)abstract
- During the past 50 years, wet stormwater ponds have been constructed to reduce negative environmental impacts of urban stormwater discharges on receiving aquatic environments. However, in many jurisdictions there is little information on the current operational status of such ponds and their functioning. This paucity of information prompted a field survey of 25 Swedish municipal stormwater ponds, aged between 3 and 26 years. The pond survey focused on estimating the pond hydraulic loading and efficiency, the state of littoral vegetation, characteristics of bottom sediment in the inlet and outlet zones (sizes and the chemistry), and the overall operational pond status, including the access for maintenance. The hydraulic efficiencies of ponds were estimated for pond footprint shapes and relative locations of the inlets and outlets using literature data. The estimated hydraulic efficiencies correlated well with the pond length-to-width ratios and the ratio of the pond surface area to the impervious area of the runoff contributing catchment (i.e., the hydraulic loading). Littoral vegetation was inspected visually and found to be overgrown at some facilities, which impeded the maintenance access. Benthic sediments in ponds contained silt and clay (<63 μm" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;"><63 μm<63 μm), sand and gravel fractions, and when compared with the literature data, such sediments appeared relatively coarse. Chemical characteristics of sediments reflected anthropogenic (traffic) activities, but without excessive contamination warranting special disposal requirements. Of the 25 ponds surveyed, four were fenced off and inaccessible to machinery. In fact, the design of these four ponds was such that it made inspection and maintenance very difficult, which may pose potential risks to ponds operation. Fifty-four percent of the investigated ponds were in need of minor maintenance, primarily because of sediment and litter accumulation in their inflow and outflow sections. The fact that the inspection survey revealed relatively few minor issues that could be corrected easily demonstrates the importance of relatively simple regular inspections serving to detect minor problems at an early stage before they would seriously impact pond functioning. The above survey methodology should be helpful for developing similar low-cost surveys in other jurisdictions.
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| 2. |
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| 3. |
- Bryhn, Andreas
(författare)
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Estimated trophic state effects and abatement costs in connection with improved urban sewage treatment in the Gulf of Riga
- 2012
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Ingår i: Journal of Environmental Engineering. - 0733-9372 .- 1943-7870. ; 138, s. 663–672-
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Tidskriftsartikel (refereegranskat)abstract
- Environmental conflicts of interest are important to account for when environmental policies are designed. This paper explores the quantitative connection between urban wastewater treatment, coastal eutrophication, and fish biomass in the mesotrophic Gulf of Riga (northern Europe). The probable effect on the water quality from one clearly defined abatement measure, improved urban sewage treatment, has been studied. The implementation cost and the likely effect on total fish biomass also have been assessed. Computer simulations by using the previously published model CoastMab suggested that good water quality according to the European Union (EU Marine) Strategy Framework Directive could be achieved if urban sewage treatment would be upgraded to Nordic and German standards, and not only around the Gulf of Riga but also in the whole Baltic Sea drainage basin. The Secchi depth would double according to these simulations, whereas total phosphorus and summer chlorophyll concentrations would decrease by 54% and 53%, respectively. The total fish biomass should be expected to decrease by approximately 42% if good water quality (as defined in EU directives) should be achieved. However, changes in total fish biomass also could be offset by changes in other important determinants, such as climate-related variables or fishing pressure. The study estimated that it could take approximately 20-40years after abatement action for the trophic state in the Gulf to stabilise again. Upgrading urban sewage treatment to this extent would cost 468-1,118million Euro per year. Treatment could have substantial positive effects on the water quality of the Gulf but could also have adverse side effects on the total fish biomass.
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| 4. |
- Brännvall, Evelina, et al.
(författare)
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Changes of fly ash properties during the ageing
- 2015
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Ingår i: Journal of environmental engineering. - 0733-9372 .- 1943-7870. ; 141:5
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Tidskriftsartikel (refereegranskat)abstract
- Aging of refuse-derived fuel (RDF) fly ashes was investigated in a long-term laboratory experiment. Aging affected the chemical stability of RDF fly ash in terms of leaching behavior, ANC, and mineralogical transformations. The design of experiment model evaluation showed that the use of RDF ashes in a top cover liner construction has the following advantages: most of the investigated hazardous elements like Pb, Cl, Cr, Cu, etc., will not be released from the ashes, and their buffer capacity will increase with time. However, aging has the disadvantage that leaching of Zn and SO 4 is likely to increase. The multivariate data analysis of the coefficients of variation did not reveal any systematic errors in the performance of the experiment. However, batch leaching test not always reflect the real situation in the landfill top cover environment.
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| 5. |
- Brännvall, Evelina, et al.
(författare)
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Factors influencing chemical and mineralogical changes in RDF fly ashes during aging
- 2014
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Ingår i: Journal of environmental engineering. - 0733-9372 .- 1943-7870. ; 140:3
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Tidskriftsartikel (refereegranskat)abstract
- The effects of aging should be considered for reliable long-term assessments of the environmental risks of the use of refuse-derived-fuel (RDF) fly ash as landfill top cover liner material. Mineral transformations that occur in RDF fly ash, and the effects of selected factors on these transformations, were studied on compacted fly ash specimens in an accelerated aging experiment using a reduced factorial design. Carbon dioxide concentration, temperature, relative air humidity, time, and the quality of added water were varied in six factor combinations. Acid neutralization capacity and leaching behavior were analyzed after four different periods of time. The results were evaluated with multivariate data analysis. A significant change in the acid neutralization capacity, a decrease in leaching of Ba, Ca, Cl − , Cr, Cu, Pb, K, and Na, and an increase in solubility of Mg, Si, Zn, and SO 2− 4 could be attributed to different aging conditions
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| 6. |
- From-Aldaron, M., et al.
(författare)
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Low Dosage Chemical Treatment for Improved Oxygenation of Pulp Mill Effluents
- 2018
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Ingår i: Journal of environmental engineering. - : American Society of Civil Engineers (ASCE). - 0733-9372 .- 1943-7870. ; 144:3
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Tidskriftsartikel (refereegranskat)abstract
- Most pulp and paper mills use aerobic biological treatment for their effluents. Aeration is the single most energy intensive process of a treatment plant. Surfactants, commonly occurring in pulping wastewaters, have been shown to decrease the oxygen transfer rate. The aim of this study was to decrease the surface activity of surfactants and thereby increase the oxygen transfer rate in pulp mill effluents by the use of chemical pretreatment in very low doses. Trials using 5 g/m(3) ferric iron showed statistically significant improvement on both k(L)a(@20) and surface tension. No sludge was precipitated owing to the very low ferric iron dosage. The novel use of chemical pretreatment, in very low doses, aiming specifically at improving oxygen transfer rate, is a promising concept for reducing the need for aeration in wastewater treatment and thus lower the electricity requirement of the wastewater treatment plant. (c) 2017 American Society of Civil Engineers.
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| 7. |
- Galfi, Helen, et al.
(författare)
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Inter-Event and Intra-Event Variations of Indicator Bacteria Concentrations in the Storm Sewer System of the City of Östersund, Sweden
- 2016
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Ingår i: Journal of environmental engineering. - 0733-9372 .- 1943-7870. ; 142:7
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Tidskriftsartikel (refereegranskat)abstract
- An episode of microbiological contamination of the drinking water supply of the City of Östersund, Sweden (63°10′45″N; 14°38′09″E) prompted a study of fecal pollution in four storm drainage catchments discharging in the vicinity of the water treatment plant intake, with the overall aim of determining the presence and variation of standard fecal indicator bacteria strains and total suspended solids (TSS) in stormwater from urban catchments with specific land uses and sizes varying from 5 to 40 ha. Four bacteria strains used as indicators of fecal pollution in Sweden were studied: total coliforms, enterococci, Escherichia coli (E. coli) and Clostridium perfringens (C. perfringens). In dry weather, indicator bacteria concentrations in storm sewers conveying baseflow did not exceed 100 colony forming units (CFU)/100 mL 100 colony forming units (CFU)/100 mL, but during wet weather, total coliform and enterococci concentrations increased 10 2 102 to 10 3 103 times, compared to those in baseflow, and considerably less in the case of E. coli and C. perfringens. Bacteria concentrations differed significantly among the sampling sites and in the majority of events observed in the four catchments; higher bacteria concentrations were observed during the early phases of runoff. Only in one catchment, positive correlations were observed between TSS and total coliforms, E. coli, and enterococci, suggesting similar sources; in the remaining catchments, no such correlations were observed. The collected indicator bacteria data represent a useful addition to the available data on indicator bacteria in stormwater in cold-climate regions.
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| 8. |
- Granström, Karin, 1974-, et al.
(författare)
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Characterization of Wood-Dryer Condensate with Assessment of Toxicity to Microorganisms
- 2017
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Ingår i: Journal of environmental engineering. - : American Society of Civil Engineers (ASCE). - 0733-9372 .- 1943-7870. ; 143:7
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Tidskriftsartikel (refereegranskat)abstract
- Drying of wood causes airborne emissions that can be reduced by recirculating all or part of the drying medium. This favors both emission control and energy efficiency, but results in a condensate that contains significant amounts of organic compounds. Drying operations have been requested by municipal regulatory bodies to clean the condensate before release. The industry has tested biological treatment of condensate from biomass dryers, but maintaining the viability of microorganisms has been a challenge. In this study, the effect of drying gas temperature and the final wood moisture content on the chemical composition and acute toxicity of the condensate was tested. Results showed that whereas the condensate from wood drying was extremely toxic to Vibrio fischeri employed in Microtox assays, the undefined mixed culture present in biosludge from a pulp and paper mill treatment plant were considerably less affected. (C) 2017 American Society of Civil Engineers.
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| 9. |
- Karlsson, Kristin, et al.
(författare)
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Environmental Risk Assessment of Sediments Deposited in Stormwater Treatment Facilities : Trace Metal Fractionation and Its Implication for Sediment Management
- 2016
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Ingår i: Journal of environmental engineering. - 0733-9372 .- 1943-7870. ; 142:11
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Tidskriftsartikel (refereegranskat)abstract
- To gather further data about metal mobility in accumulated sediments in stormwater treatment facilities, metal mobility in sediments from sedimentation tanks, gully pot sediment traps, and sedimentation ponds was investigated using the sequential extraction procedure. This method allows distinguishing the metal speciation between ion-exchangeable, carbonate-associated, reducible, organic matter/sulfide-associated, and residual fractions. The metal fractionation reveals that, for all treatment facilities, the majority of Cd, Cu, Pb, and Zn and a significant amount of Ni were in potentially mobile forms. Cd, Pb, and Zn are, to a large extent, associated with Fe-Mn oxides while Cu is commonly present as Cu–organic matter complexes. The metals in these potentially mobile fractions may represent a potential environmental hazard, e.g., due to release during maintenance (sediment removal) when the chemical phase distribution might change.
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| 10. |
- Lüdtke, Maximilian, et al.
(författare)
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Impact of Temperature-Dependent Reaction Rates on Methane Yields in Intermittently Fed Mesophilic Sludge Digestion
- 2018
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Ingår i: Journal of environmental engineering. - : American Society of Civil Engineers (ASCE). - 0733-9372 .- 1943-7870. ; 144:1
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Tidskriftsartikel (refereegranskat)abstract
- Efficient anaerobic digestion (AD) of sludge is crucial for the overall energy balance, minimization of carbon footprint, and the economy for most wastewater-treatment plants (WWTPs). In recent years, intermittent feeding (IF) has become increasingly interesting because it has been shown to better condition the digester microbiology for overloading events. Additionally, IF is required when AD facilities move toward being active players in grid balancing via on-demand delivery and storage of green energy (i.e., power-to-gas). In this study, six laboratory-scale IF digesters were operated at 34, 37, and 40°C in a 300-day experiment to determine the impact of temperature on methane yield and long-term stability at typical conditions for conventional WWTP sludge digestion. The results show that IF led to no significant differences in methane yield observed among tested temperatures at an organic loading rate of 3 kg VS m-3 days-1 and a hydraulic retention time of 16 days. However, in an on-demand energy-delivery scenario, increased temperature could be interesting because of significantly increased methane production in the first hours following feeding.
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