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  • 1.
    Anbalagan, Anbarasan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB AB, Corporate Research, Västerås, Sweden.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Influence of hydraulic retention time on indigenous microalgae and activated sludge process2016In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 91, p. 277-284Article in journal (Refereed)
    Abstract [en]

    Integration of the microalgae and activated sludge (MAAS) process in municipal wastewater treatment and biogas production from recovered MAAS was investigated by studying the hydraulic retention time (HRT) of semi-continuous photo-bioreactors. An average total nitrogen (TN) removal efficiency (RE) of maximum 81.5 ± 5.1 and 64.6 ± 16.2% was achieved at 6 and 4 days HRT. RE of total phosphorous (TP) increased slightly at 6 days (80 ± 12%) HRT and stabilized at 4 days (56 ± 5%) and 2 days (55.5 ± 5.5%) HRT due to the fluctuations in COD and N/P mass ratio of the periodic wastewater. COD and organic carbon were removed efficiently and a rapidly settleable MAAS with a sludge volume index (SVI_10) of less than 117 mL g-1 was observed at all HRTs. The anaerobic digestion of the untreated MAAS showed a higher biogas yield of 349 ± 10 mL g VS-1 with 2 days HRT due to a low solids retention time (SRT). Thermal pretreatment of the MAAS (120 °C, 120 min) did not show any improvement with biogas production at 6 days (269 ± 3 (untreated) and 266 ± 16 (treated) mL gVS-1), 4 days (258 ± 11(untreated) and 263 ± 10 (treated) mL gVS-1) and 2 days (308 ± 19 mL (treated) gVS-1) HRT. Hence, the biogas potential tests showed that the untreated MAAS was a feasible substrate for biogas production. Results from this proof of concept support the application of MAAS in wastewater treatment for Swedish conditions to reduce aeration, precipitation chemicals and CO2 emissions. 

  • 2.
    Johansson, Lena
    et al.
    Royal Institute of Technology.
    Gustafsson, Jon-Petter
    Royal Institute of Technology, Sweden.
    Phosphate removal using blast furnace slags and opoka-mechanisms2000In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Water Research, ISSN 0043-1354, Vol. 34, no 1, p. 259-265Article in journal (Refereed)
    Abstract [en]

    The abiotic sorption efficiency of on-site wastewater treatment systems can be improved by using a strongly sorbing filter material that, if it retains phosphorus (P) in a plant available way, can be used as fertiliser when P saturation is achieved. Two materials, blast furnace slag and the siliceous sedimentary rock opoka, have shown a high P sorption capacity and were included in a set of experiments to investigate the P retention mechanisms from model P-solution. Experiments focusing on the P sorption, capacity and calcium (Ca) and PO4 determination were carried out. The pH was also measured. The P sorption experiment showed that some slags were efficient P retainers, while the opoka was the least efficient P retainer. The pH decreased in all samples as a function of P addition. In the slag samples, the Ca concentration also decreased as a function of P addition, suggesting Ca-P precipitation as the major P removal mechanism for the slag. The Ca and PO4 speciation data ruled out the formation of amorphous calcium phosphates and/or octacalcium phosphate as the major P removal mechanism. However, the calculated ion activity products displayed clear evidence that hydroxyapatite had precipitated above a certain critical supersaturation limit. This would explain the poor P retention efficiency of the opoka samples in this study as the ion activity products were too low. The finding that direct hydroxyapatite formation is the predominant P removal mechanism might have important implications for their possible use as fertiliser due to the poor solubility of hydroxyapatite.

  • 3.
    Johansson Westholm, Lena
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Substrates for phosphorus removal - potential benefits for on-site wastewater treatment?2006In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 40, no 1, p. 23-26Article in journal (Refereed)
    Abstract [en]

    A large number of substrates potential for removal of phosphorus (P) in wastewater has been reviewed. The substrates consist of natural materials, industrial by-products and man-made products. Most substrates have been investigated in batch and column studies in the laboratory; others have also been tested in field trials. The results from these investigations vary, but a few substrates, e.g. wollastonite, slag material and, to some extent, light weight aggregate products, have demonstrated promising properties with regard to P-sorption capacity and hydraulics. The problems of normalisation of data are discussed, as well as the substrates potential benefits for on-site wastewater treatment.

  • 4.
    Nilsson, Charlotte
    et al.
    KTH Royal Institute of Technology.
    Renman, Gunno
    KTH Royal Institute of Technology.
    Johansson Westholm, Lena
    Mälardalen University, School of Business, Society and Engineering.
    Renman, Agniezska
    KTH Royal Institute of Technology.
    Drizo, Aleksandra
    Effect of organic load on phosphorus and bacteria removal from wastewater using alkaline filter materials2013In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 47, no 16, p. 6289-6297Article in journal (Refereed)
    Abstract [en]

    The organic matter released from septic tanks can disturb the subsequent step in on-site wastewater treatment such as the innovative filters for phosphorus removal. This study investigated the effect of organic load on phosphorus (P) and bacteria removal by reactive filter materials under real-life treatment conditions. Two long-term column experiments were conducted at very short hydraulic residence times (average ~5.5h), using wastewater with high (mean ~120mgL-1) and low (mean ~20mgL-1) BOD7 values. Two alkaline filter materials, the calcium-silicate material Polonite and blast furnace slag (BFS), were tested for the removal capacity of total P, total organic carbon (TOC) and Enterococci. Both experiments showed that Polonite removed P significantly (p<0.01) better than BFS. An increase in P removal efficiency of 29.3% was observed for the Polonite filter at the lower concentration of BOD7 (p<0.05). Polonite was also better than BFS with regard to removal of TOC, but there were no significant differences between the two filter materials with regard to removal of Enterococci. The reduction in Enterococci was greater in the experiment using wastewater with high BOD7, an effect attributable to the higher concentration of bacteria in that wastewater. Overall, the results demonstrate the importance of extensive pre-treatment of wastewater to achieve good phosphorus removal in reactive bed filters and prolonged filter life.

  • 5.
    Nõlvak, H.
    et al.
    Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, 46 Vanemuise St., Tartu, Estonia.
    Truu, M.
    Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, 46 Vanemuise St., Tartu, Estonia.
    Oopkaup, K.
    Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, 46 Vanemuise St., Tartu, Estonia.
    Kanger, K.
    Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, 46 Vanemuise St., Tartu, Estonia.
    Krustok, I.
    Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, 46 Vanemuise St., Tartu, Estonia.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Truu, J.
    Institute of Ecology and Earth Sciences, Faculty of Science and Technology, University of Tartu, 46 Vanemuise St., Tartu, Estonia.
    Reduction of antibiotic resistome and integron-integrase genes in laboratory-scale photobioreactors treating municipal wastewater2018In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 142, p. 363-372Article in journal (Refereed)
    Abstract [en]

    Wastewater treatment systems receiving municipal wastewater are major dissemination nodes of antibiotic resistance genes (ARGs) between anthropogenic and natural environments. This study examined the fate of antibiotic resistome and class 1–3 integron-integrase genes in photobioreactors that were treating municipal wastewater diluted (70/30) with lake or tap water for the algal biomass production. A combined approach of metagenomic and quantitative (qPCR) analysis was undertaken. Municipal wastewater treatment in the photobioreactors led to reduced antibiotic resistome proportion, number of ARG subtypes, and abundances of individual ARGs in the bacterial community. The ARGs and intI1 gene abundances and relative abundances in the discharges of the photobioreactors were either comparable or lower than the respective values in the effluents of conventional wastewater treatment plants. The reduction of the resistome proved to be strongly related to the changes in the bacterial community composition during the wastewater treatment process as it was responding to rising pH levels caused by intense algal growth. Several bacterial genera (e.g., Azoarcus, Dechloromonas, and Sulfuritalea) were recognized as potential hosts of multiple antibiotic resistance types. Although the lake water contributed a diverse and abundant resistome and intI genes profile to the treatment system, it proved to be considerably more beneficial for wastewater dilution than the tap water. The diversity (number of detected resistance types and subtypes) and proportion of the antibiotic resistome, the amount of plasmid borne integron-integrase gene reads, and the abundances and relative abundances of the majority of quantified ARGs (aadA, sul1, tetQ, tetW, qnrS, ermB, blaOXA2-type) and intI1 gene as well as the amount of multi-resistance determinants were significantly lower in the discharges of photobioreactors where lake water was used to dilute wastewater.

  • 6.
    Westholm, Lena Johansson
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Substrates for Phosphorus Removal - Potential benefits for on-site wastewater treatment?2006In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 40, no 1, p. 23-36Article in journal (Refereed)
    Abstract [en]

    A large number of substrates potential for removal of phosphor-us (P) in wastewater has been reviewed. The substrates consist of natural materials, industrial by-products and man-made products. Most substrates have been investigated in batch and column studies in the laboratory; others have also been tested in field trials. The results from these investigations vary, but a few substrates, e.g. wollastonite, slag material and, to some extent, light weight aggregate products, have demonstrated promising properties with regard to P-sorption capacity and hydraulics. The problems of normalisation of data are discussed, as well as the substrates potential benefits for on-site wastewater treatment.

1 - 6 of 6
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