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  • 1.
    Andersson, Sofia
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology (closed September 2009).
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology (closed September 2009).
    Bioaugmentation for enhanced denitrification in a labscale treatment system2006In: Proceedings of the Second IASTED International Conference on Advanced Technology in the Environmental Field / [ed] Ubertini, L, ACTA Press, 2006, p. 63-67Conference paper (Refereed)
    Abstract [en]

    The effect of bioaugmentation was investigated in a predenitrification lab-scale wastewater treatment system. The aim was to investigate the difference between two approaches to bioaugmentation: one in which suspended overnight culture was used as inoculum and another where bacteria immobilized in 1% agar beads were used. Pure cultures of the denitrifying bacteria Comamonas denitrificans ATCC 700936T were used in the experiments. The effect of bioaugmentation on the system was monitored using fluorescent in situ hybridization (FISH) and denitrification activity tests. The bioaugmentation with suspended bacteria showed a rapid initial (4 days) increase in denitrification activity. After 8 days the activity declined to the level of the reference system and cells of C. denitrificans were no longer detectable. Augmentation with agar-embedded bacteria resulted in a small increase in activity and very few bacteria of C. denitrificans could be observed.

  • 2.
    Andersson, Sofia
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Influence of microbial interactions and EPS/polysaccharide composition on nutrient removal activity in biofilms formed by strains found in wastewater treatment systems2011In: Microbiology Research, ISSN 0944-5013, E-ISSN 1618-0623, Vol. 166, no 6, p. 449-457Article in journal (Refereed)
    Abstract [en]

    The study of biofilm function, structure and microbial interactions might help to improve our understanding of biofilm wastewater treatment processes. However, few reports specifically address the influence of interactions within multispecies biofilms on microbial activity and biofilm composition. Thus, the relationship between biofilm formation, denitrification activity, phosphorus removal and the composition of extracellular polymeric substances (EPS), exopolysaccharides and the bacterial community was investigated using biofilms of denitrifying and phosphorus removing strains Comamonas denitrificans 110, Brachymonas denitrificans B79, Aeromonas hydrophila L6 and Acinetobacter calcoaceticus ATCC23055. Denitrification activity within the biofilms generally increased with the amount of biofilm while phosphorus removal depended on bacterial growth rate. Synergistic effects of co-growth on denitrification (B. denitrificans B79 and A. hydrophila L6) and phosphorus removal (C. denitrificans 110 with either A. calcoaceticus or A. hydrophila L6) were observed. B. denitrificans B79 was highly affected by interspecies interactions with respect to biofilm formation, denitrification activity and EPS composition, while C. denitrificans 110 remained largely unaffected. In some of the dual and quadruple strain biofilms new exopolysaccharide monomers were detected which were not present in the pure strain samples.

  • 3.
    Andersson, Sofia
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Land, Carl Johan
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Biological nutrient removal by individual and mixed strain biofilmsManuscript (Other academic)
  • 4.
    Andersson, Sofia
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Land, Carl Johan
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Characterization of extracellular polymeric substances from denitrifying organism Comamonas denitrificans2009In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 82, no 3, p. 535-543Article in journal (Refereed)
    Abstract [en]

    Extracellular polymeric substances (EPS) play an important role in the formation and activity of biofilms in wastewater treatment (WWT). The EPS of the denitrifying biomarker Comamonas denitrificans strain 110, produced in different culture media and growth modes, were characterized. The EPS mainly contained protein (3-37%), nucleic acids (9-50%), and carbohydrates (3-21%). The extracellular DNA was found to be important for initial biofilm formation since biofilm, but not planktonic growth, was inhibited in the presence of DNase. The polysaccharide fraction appeared to consist of at least two distinct polymers, one branched fraction (A) made up of glucose and mannose with a molecular weight around 100 kDa. The other fraction (B) was larger and consisted of ribose, mannose, glucose, rhamnose, arabinose, galactose, and N-acetylglucosamine. Fraction B polysaccharides were mainly found in capsular EPS which was the dominant type in biofilms and agar-grown colonies. Fraction A was abundant in the released EPS, the dominant type in planktonic cultures. Biofilm and agar-grown EPS displayed similar overall properties while planktonic EPS showed clear compositional disparity. This study presents results on the physiology of a key WWT organism, which may be useful in the future development of improved biofilm techniques for WWT purposes.

  • 5.
    Andersson, Sofia
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Rajarao, Gunaratna Kuttuva
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Persistence and competition of denitrifying biofilms subjected to a natural wastewater floraManuscript (Other academic)
  • 6.
    Andersson, Sofia
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Land, Carl Johan
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Biofilm formation and interactions of bacterial strains found in wastewater treatment systems2008In: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 283, no 1, p. 83-90Article in journal (Refereed)
    Abstract [en]

    Biofilm formation and adherence properties of 13 bacterial strains commonly found in wastewater treatment systems were studied in pure and mixed cultures using a crystal violet microtiter plate assay. Four different culture media were used, wastewater, acetate medium, glucose medium and diluted nutrient broth. The medium composition strongly affected biofilm formation. All strains were able to form pure culture biofilms within 24 h in at least one of the tested culture media and three strains were able to form biofilm in all four culture media, namely Acinetobacter calcoaceticus ATCC 23055, Comamonas denitrificans 123 and Pseudomonas aeruginosa MBL 0199. The adherence properties assessed were initial adherence, cell surface hydrophobicity, and production of amyloid fibers and extracellular polymeric substances. The growth of dual-strain biofilms showed that five organisms formed biofilm with all 13 strains while seven formed no or only weak biofilm when cocultured. In dual-strain cultures, strains with different properties were able to complement each other, giving synergistic effects. Strongest biofilm formation was observed when a mixture of all 13 bacteria were grown together. These results on attachment and biofilm formation can serve as a tool for the design of tailored systems for the degradation of municipal and industrial wastewater.

  • 7.
    Andersson, Sofia
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Nilsson, Mirja
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Assessment of carrier materials for biofilm formation and denitrification2008In: Vatten, ISSN 0042-2886, Vol. 64, p. 201-207Article in journal (Refereed)
  • 8.
    Desta, Adey F.
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology (closed September 2009).
    Dalhammer, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology (closed September 2009).
    Kittuva, Gunatrana R.
    KTH, School of Biotechnology (BIO), Environmental Microbiology (closed September 2009).
    A modified culture-based study of bacterial community composition in a tannery wastewater treatment plant2010In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 62, no 11, p. 2543-2549Article in journal (Refereed)
    Abstract [en]

    Though culture-independent methods have been used in preference to traditional isolation techniques for characterization of microbial community of wastewater treatment plants, it is difficult to widely apply this approach in resource-poor countries. The present study aimed to develop a test to identify the culturable portion of bacterial community in a high-strength wastewater. Wastewater samples were collected from nitrification-denitrification and settling tanks of the treatment plant of Elmo Leather AB tannery located in Boras, Sweden. After cultivating on nutrient agar with the optimal dilution (10(-2)), phenotypic and biochemical identification of the bacteria were done with colony morphology, Gram reaction, growth on MacConkey, phenylethanol media, triple sugar Iron agar slants, catalase and oxidase tests. Biochemical grouping of the isolates was done based on their test results for MacConkey, phenylethanol media, triple sugar Iron agar and oxidase test reaction. From the biochemical groups, isolates were randomly selected for API test and 16SrRNA gene sequencing. The isolates from the denitrification, nitrification tank were identified to be Paracoccus denitrificans (67%), Azoarcus spp (3%) and Spingomonas wittichii (1%). From the settling tank, Paracoccus denitrificans (22%), Corynebacterium freneyi (20%) and Bacillus cereus (1%) were identified. The grouping based on biochemical test results as well as the identification based on sequencing has shown coherence except for discrepancies with the API test. The preliminary implications of the grouping based on culture-based characteristics and its potential application for resource-limited environmental microbial studies is discussed.

  • 9. Eriksson, M.
    et al.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Borg-Karlson, Anna-Karin
    KTH, Superseded Departments, Chemistry.
    Biological degradation of selected hydrocarbons in an old PAH/creosote contaminated soil from a gas work site2000In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 53, no 5, p. 619-626Article in journal (Refereed)
    Abstract [en]

    An old PAH/creosote contaminated soil (total similar to 300 mu g PAH/g soil) from a former gas work site in Stockholm, Sweden, has been treated at 20 degrees C with the addition of various nutrients and inoculated with bacteria (isolated from the soil) to enhance the degradation of selected hydrocarbons. Microcosm studies showed that the soil consisted of two contaminant fractions: one available, easily degraded fraction and a strongly sorbed, recalcitrant one. The bioavailable fraction, monitored by headspace solid phase microextraction, contained aromatics with up to three rings, and these were degraded within 20 days down to non-detectable levels (ng PAH/g soil) by both the indigenous bacteria and the externally inoculated samples. The nutrient additives were: a minimal medium (Bushnell-Haas), nitrate, nitrite, potting soil (Anglamark, Sweden), sterile water and aeration with Bushnell-Haas medium. After 30 days treatment most of the sorbed fractions were still present in the soil. Stirring or mechanical mixing of the soil slurries had the greatest effect on degradation, indicating that the substances were too strongly sorbed for the microorganisms. When stirring the choice of nutrient seemed less important. For the non-stirred samples the addition of nitrate with the bacterial inoculum showed the best degradation, compared to the other non-stirred samples. At the end of the experiments, accumulations of metabolites/degradation products, such as 9H-fluorenone, 4-hydroxy-9H-fluorenone, 9,10-phenanthrenedione and 4H-cyclopenta[def]phenanthrenedione were detected. The metabolite 4-hydroxy-9H-fluorenone increased by several orders of magnitude during the biological treatments. Microbial activity in the soil was measured by oxygen consumption and carbon dioxide production.

  • 10. Eriksson, M.
    et al.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Mohn, W. W.
    Bacterial growth and biofilm production on pyrene2002In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 40, no 1, p. 21-27Article in journal (Refereed)
    Abstract [en]

    Enrichment cultures inoculated with Arctic soil yielded a biofilm that grew on pyrene and phenanthrene. In a 60-day period, the biofilm degraded 20 mug ml(-1) pyrene or 39 mug ml(-1) phenanthrene. Single colonized pyrene crystals (approximately 1.5 x 0.75 X 0.35 mm) yielded 10(11) culturable heterotrophs and 10(5) biofilm propagules. Analysis of ribosomal intergenic spacers identified six phylotypes in a clone library from the pyrene biofilm. Analysis of 16S rRNA gene sequences indicated that the phylotypes. in order of decreasing abundance, are most closely related to members of the genera Polaromonas, Sphingomonas, Alcaligenes, Caulobacter and Variovorax. Two isolates capable of growth on pyrene. both Pseudomonas spp., were obtained from the pyrene enrichment culture. Growth of microbial biofilms on polycyclic aromatic hydrocarbons has not been reported previously, and this mode of growth may have important effects on substrate uptake.

  • 11. Eriksson, M.
    et al.
    Faldt, J.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Borg-Karlson, Anna-Karin
    KTH, Superseded Departments, Chemistry.
    Determination of hydrocarbons in old creosote contaminated soil using headspace solid phase microextraction and GC-MS2001In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 44, no 7, p. 1641-1648Article in journal (Refereed)
    Abstract [en]

    Headspace solid phase microextraction (HS-SPME) has been used together with GC-MS to analyze organic substances directly in a soil, heavily contaminated with PAHs/creosote (similar to 300 mg/kg soil), from an old gaswork site in Stockholm, Sweden. The HS-SPME results, both qualitative and quantitative, were compared with traditional liquid extraction using ethyl acetate/hexane (20:80). It was shown that the concentrations determined with HS-SPME at 60 degreesC correlated well, for compounds containing up to two and three aromatic rings (naphthalenes, acenaphthene, acenaphthylene and fluorenes, while a lower concentration was obtained for phenanthrene, anthracene, fluoranthene and pyrene. The total concentrations for each compound determined with HS-SPME ranged from 2 to 25 mug/g soil. Quantification was done using standard addition of compounds directly to the soil samples. The bioavailable fraction of the compounds in the contaminated soil at 20 degreesC was analyzed using external calibration by spiking sterile uncontaminated sand (same texture and particle size as the contaminated soil but without a heavily sorbed organic fraction) with hydrocarbon standards in different concentrations. Storage of exposed fibers at 20 degreesC showed that analysis should be done within two days to make qualitative measurements and earlier (as soon as possible) for quantitative determinations.

  • 12. Eriksson, M.
    et al.
    Sodersten, E.
    Yu, Z. T.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Mohn, W. W.
    Degradation of polycyclic aromatic hydrocarbons at low temperature under aerobic and nitrate-reducing conditions in enrichment cultures from northern soils2003In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 69, no 1, p. 275-284Article in journal (Refereed)
    Abstract [en]

    The potential for biodegradation of polycyclic aromatic hydrocarbons (PAHs) at low temperature and under anaerobic conditions is not well understood, but such biodegradation would be very useful for remediation of polluted sites. Biodegradation of a mixture of 11 different PAHs with two to five aromatic rings, each at a concentration of 10 mug/ml, was studied in enrichment cultures inoculated with samples of four northern soils. Under aerobic conditions, low temperature severely limited PAH biodegradation. After 90 days, aerobic cultures at 20degreesC removed 52 to 88% of the PAHs. The most extensive PAH degradation under aerobic conditions at 7degreesC, 53% removal, occurred in a culture from creosote-contaminated soil. Low temperature did not substantially limit PAH biodegradation under nitrate-reducing conditions. Under nitrate-reducing conditions, naphthalene, 2-methyl naphthalene, fluorene, and phenanthrene were degraded. The most extensive PAH degradation under nitrate-reducing conditions at 7degreesC, 39% removal, occurred in a culture from fuel-contaminated Arctic soil. In separate transfer cultures from the above Arctic soil, incubated anaerobically at 7degreesC, removal of 2-methylnaphthalene and fluorene was stoichiometrically coupled to nitrate removal. Ribosomal intergenic spacer analysis suggested that enrichment resulted in a few predominant bacterial populations, including members of the genera Acidovorax, Bordetella, Pseudomonas, Sphingomonas, and Variovorax. Predominant populations from different soils often included phylotypes with nearly identical partial 16S rRNA gene sequences (i.e., same genus) but never included phylotypes with identical ribosomal intergenic spacers (i.e., different species or subspecies). The composition of the enriched communities appeared to be more affected by presence of oxygen, than by temperature or source of the inoculum.

  • 13. Ghebremichael, K. A.
    et al.
    Gunaratna, K. R.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Single-step ion exchange purification of the coagulant protein from Moringa oleifera seed2006In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 70, no 5, p. 526-532Article in journal (Refereed)
    Abstract [en]

    The coagulant protein from Moringa oleifera (MO) seed was purified using a single-step batch ion exchange (IEX) method. Adsorption and elution parameters were optimized. Impact of the purification on the reduction of organic and nutrient release to the water was studied. The matrix was equilibrated using ammonium acetate buffer, and the optimum ionic strength of NaCl for elution was 0.6 M. The time for adsorption equilibrium was between 90 and 120 min. Maximum adsorption capacity of the matrix, estimated with the Langmuir model, was 68 mg protein/g adsorbent. The purified protein does not release organic and nutrient loads to the water, which are the main concerns of the crude extract. This work suggests that a readily scalable single-step IEX purification method can be used to produce the coagulant protein and it can be carried out with locally available facilities. This will promote the use of MO in large water treatment plants and other industries.

  • 14. Ghebremichael, K. A.
    et al.
    Gunaratna, K. R.
    Henriksson, H.
    Brumer, Harry
    KTH, School of Biotechnology (BIO), Glycoscience.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    A simple purification and activity assay of the coagulant protein from Moringa oleifera seed2005In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 39, no 11, p. 2338-2344Article in journal (Refereed)
    Abstract [en]

    Use of extracts from Moringa oleifera (MO) is of great interest for low-cost water treatment. This paper discusses water and salt extraction of a coagulant protein from the seed, purification using ion exchange, its chemical characteristics, coagulation and antimicrobial properties. The coagulant from both extracts is a cationic protein with pI greater than 9.6 and molecular mass less than 6.5 kDa. Mass spectrometric analysis of the purified water extract indicated that it contained at least four homologous proteins, based on MS/MS peptide sequence data. The protein is thermoresistant and remained active after 5 h heat treatment at 95 degrees C. The coagulant protein showed both flocculating and antibacterial effects of 1.1-4 log reduction. With samples of high turbidity, the MO extract showed similar coagulation activity as alum. Cecropin A and MO extract were found to have similar flocculation effects for clay and microorganisms. Simple methods for both the purification and assay of MO coagulating proteins are presented, which are necessary for large-scale water treatment applications.

  • 15. Grunditz, C.
    et al.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Development of nitrification inhibition assays using pure cultures of Nitrosomonas and Nitrobacter2001In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 35, no 2, p. 433-440Article in journal (Refereed)
    Abstract [en]

    Restricted requirements for nitrogen reduction at wastewater treatment plants have increased the need for assays determining the inhibition of nitrification. In this paper, two new essays studying ammonia oxidation and nitrite oxidation, respectively, are presented. As test organisms, pure cultures of Nitrosomonas and Nitrobacter isolated from activated sludge are used. The assays are performed in test tubes where the bacteria are incubated with the compound or wastewater to be tested. The nitrification rate is measured during 4h and compared with reference samples. The test organisms were characterised with respect to temperature, pH and cell activity. Optimum temperature was 35 degreesC for Nitrosomonas and 38 degreesC for Nitrobacter; optimum pH was 8.1 for Nitrosomonas and 7.9 for Nitrobacter. There was a linear relationship between the nitrification rate and the cell concentration in the studied interval. The cell activity decreased slightly with storage time. A significant level of inhibition was calculated to 11% for the Nitrosomonas assay, and to 9% for the Nitrobacter assay. The assays are applicable to determination of nitrification inhibition in samples of industrial waste waters or influents of treatment plants, or chemical substances likely to be found in wastewater.

  • 16. Gumaelius, L.
    et al.
    Magnusson, G.
    Pettersson, B.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Comamonas denitrificans sp nov., an efficient denitrifying bacterium isolated from activated sludge2001In: International Journal of Systematic and Evolutionary Microbiology, ISSN 1466-5026, E-ISSN 1466-5034, Vol. 51, p. 999-1006Article in journal (Refereed)
    Abstract [en]

    To find a biomarker for denitrification in activated sludge, five denitrifying strains isolated from three wastewater treatment plants were studied. These strains were selected from among 1500 isolates for their excellent denitrifying properties. They denitrify quickly and have no lag phase when switching from aerobic to anoxic conditions. All strains have the cd(1)-type of nitrite reductase. The strains are Gram-negative rods and they all grow as filamentous chains when cultivated in liquid solution. The strains differ in colony morphology when grown on nutrient agar. Almost full-length 16S rDNA sequences were determined and phylogenetic analysis revealed that these strains are positioned among members of the genus Comamonas in the beta -subclass of the Proteobacteria. Signature nucleotides and bootstrap percentages were also analysed to verify this position. Strains 110, 123(T), 2.99g, 5.38g and P17 were less than or equal to 96.7 % similar to known strains, but greater than or equal to 99.7 % similar to each other, as judged from their 16S rDNA sequences, and grouped tightly together in the phylogenetic tree. Sequence motifs in the 16S rRNA gene were also found, suggesting the monophyletic origin of these strains. Nevertheless, some strains differed from the others, for example strain 110 branches early from the other strains and 5.38g is phenotypically more inert. Therefore, it is proposed that strains 110, 123(T), 2.99g and P17 are classified into a new species, Comamonas denitrificans sp. nov., while the taxonomic status of strain 5.38g will have to await the outcome of further studies. The type strain of Comamonas denitrificans is 123(T) (ATCC 700936(T)).

  • 17. Jonsson, K.
    et al.
    Grunditz, C.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Jansen, J. L.
    Occurrence of nitrification inhibition in Swedish municipal wastewaters2000In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 34, no 9, p. 2455-2462Article in journal (Refereed)
    Abstract [en]

    The occurrence of substances inhibiting nitrification in Swedish municipal wastewaters was investigated using three methods: a screening method based on activated sludge and two pure culture methods based on Nitrosomonas and Nitrobacter. Influent samples from 109 wastewater treatment plants collected every day during one specific week were investigated. The three test methods were also compared. The results of the screening method showed that about 60% of the plants received wastewater containing inhibitory substances, although only 4% had considerable inhibition (>20%). With the two pure culture methods, inhibition was found at about 45% of the plants investigated, with considerable inhibition found at 13% and 20% of the plants with the Nitrosomonas and the Nitrobacter methods, respectively. The limit of detection was determined to be 5% inhibition for the screening method, 11% inhibition for the Nitrosomonas method and 13% inhibition for the Nitrobacter method. The pure culture methods found more samples strongly inhibitory or stimulating than the screening method. The highest correlation between the inhibition results from the three methods was found between the screening method and the Nitrosomonas method. It was also shown for sludge from several activated sludge treatment plants, that they were adapted to the toxic compounds present in the influent. At high inhibition this acclimatisation was less pronounced. No correlation was found for any of the methods between the inhibition and parameters such as the size of the plant, the geographic location, the content of ammonia, COD or conductivity in the influent, the presence of leachate or the percentage of industrial wastewater in the influent, or types of industries in the catchment area. However, the constantly highest inhibition was found at a plant with a large number of different industries connected. Any clear pattern for the variation of inhibition during the week was not found.

  • 18.
    Kyambadde, Joseph
    et al.
    KTH, Superseded Departments, Biotechnology.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Kansiime, Frank
    Makerere University.
    Functional assessment of horizontal surface flow constructed wetlands receiving pre-treated domestic wastewater in Uganda.In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932Article in journal (Other academic)
  • 19.
    Kyambadde, Joseph
    et al.
    KTH, School of Biotechnology (BIO).
    Kansiime, F.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO).
    Distribution and activity of ammonium-oxidizing bacteria in Nakivubo wastewater channel and wastewater treatment wetland,Uganda2006In: Acta Hydrochimica et Hydrobiologica, ISSN 0323-4320, E-ISSN 1521-401X, Vol. 34, no 1-2, p. 137-145Article in journal (Refereed)
    Abstract [en]

    The pollution profiles of Nakivubo channel and wetland, and the spatial distribution of ammonium-oxidizing bacteria and the corresponding ammonium-oxidation activities along Nakivubo channel and wetland are presented. A set of physico-chemical and biochemical variables was monitored, and numbers and activity of ammonium-oxidizing bacteria in the water, sediment and epiphyton were quantified to estimate their influence on the nitrification and nitrogen bio-conversions in general, and to determine the factors influencing the distribution of ammonium-oxidizing bacteria in Nakivubo channel and wetland. Considerable numbers of ammonium-oxidizing bacteria and ammonium-oxidation activities were found upstream of Nakivubo channel suggesting that the physico-chemical conditions were suitable for the survival of nitrifying bacteria. However, the longitudinal decline in numbers and activity of ammonium-oxidizers was probably due to (1) high biodegradable organic matter input which supported proliferation of heterotrophs, consuming the little available oxygen, (2) hydro-sedimentary conditions of the channel, (3) die-off due to presence of toxic and inhibitory chemicals and metal compounds. The removal of biochemical oxygen demand was significantly higher than that of nitrogen indicating lower self-purification efficiency for nitrogen. A comparison of the ammonium-oxidation activity of the different phases indicated that epiphytic nitrification was more important than that of sediment and water compartments of the wetland, whereas sediment and suspended nitrifiers were equally important for nitrification upstream of Nakivubo channel.

  • 20.
    Kyambadde, Joseph
    et al.
    KTH, School of Biotechnology (BIO).
    Kansiime, Frank
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO).
    Nitrogen and phosphorus removal in substrate-free pilot constructed wetlands with horizontal surface flow in Uganda2005In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 165, no 1-4, p. 37-59Article in journal (Refereed)
    Abstract [en]

    In constructed wetlands (CWs) with horizontal sub-surface flow, nutrient removal, especially phosphorus, is limited because the root biomass fills the pore spaces of the substrate (usually gravel), directing wastewater flow to deeper wetland media; plants are not regularly harvested; the litter formed by decomposing vegetation remains on the surface of the substrate and thus does not interact with the wastewater; and the substrate media often used provide only limited adsorption. Effective nutrient removal including rootzone oxidation, adsorption and plant uptake therefore requires sufficient interaction of wastewater with the treatment media. We assessed the feasibility of biological nutrient removal from wastewater using substrate-free CWs with horizontal flow, planted with two tropical macrophytes namely, Cyperus papyrus and Miscanthidium violaceum. The objectives were to evaluate the system treatment efficiency under semi-natural conditions, and to assess microbial and plant biomass contributions to nutrient removal in the CWs. Results showed high removal efficiencies for biochemical oxygen demand, ammonium-nitrogen (NH4-N) and phosphorus (P) fractions in papyrus-based CWs (68.6-86.5%) compared to Miscanthidium (46.7-61.1%) and unplanted controls (31.6-54.3%). Ammonium oxidizing bacteria in CW root-mats (108-109 cells/gram dry weight) and residual nitrite and nitrate concentrations in the water phase indicated active system nitrification. Papyrus showed higher biomass production and nutrient uptake, contributing 28.5% and 11.2%, respectively, of the total N and P removed by the system compared to 15% N and 9.3% P removed by Miscanthidium plants. Compared to literature values, nitrification, plant uptake and the overall system treatment efficiency were high, indicating a high potential of this system for biological nutrient removal from wastewaters in the tropics.

  • 21.
    Kyambadde, Joseph
    et al.
    KTH, Superseded Departments, Biotechnology.
    Kansiime, Frank
    Makerere University .
    Gumaelius, Lena
    KTH, Superseded Departments, Biotechnology.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    A comparative study of Cyperus papyrus and Miscanthidium violaceum-based constructed wetlands for wastewater treatment in a tropical climate2004In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 38, no 2, p. 475-485Article in journal (Refereed)
    Abstract [en]

    The treatment efficiencies of constructed wetlands containing Cyperus papyrus L. (papyrus) and Miscanthidium violaceum (K. Schum.) Robyns (synonymous with Miscanthus violaceum (K. Schum) Pilg.) were investigated in a tropical climate (Kampala, Uganda). Papyrus showed higher ammonium-nitrogen and total reactive phosphorus (TRP) removal (75.3% and 83.2%) than Miscanthidium (61.5% and 48.4%) and unplanted controls (27.9% ammonium-nitrogen). No TRP removal was detected in control effluent. Nutrients (N and P) were significantly higher (p < 0.015) in papyrus than Miscanthidium plant tissues. Plant uptake and storage was the major factor responsible for N and P removal in treatment line 2 (papyrus) where it contributed 69.5% N and 88.8% P of the total N and P removed. It however accounted for only 15.8% N and 30.7% P of the total N and P removed by treatment line 3 (Miscanthidium violaceum). In addition, papyrus exhibited a significantly larger (p = 0.000) number of adventitious roots than Miscanthidium. Nitrifying bacteria attached to papyrus (2.15 x 10(6) +/- 1.53 x 10(5) MPN/g DW) and Miscanthidium roots (1.30 x 10(4) +/- 8.83 x 10(2) MPN/g DW) and the corresponding nitrification activities were consistent with this finding. Epiphytic nitrifiers appeared more important for total nitrification than those in peat or suspended in water. Papyrus root structures provided more microbial attachment sites, sufficient wastewater residence time, trapping and settlement of suspended particles, surface area for pollutant adsorption, uptake, assimilation in plant tissues and oxygen for organic and inorganic matter oxidation in the rhizosphere, accounting for its high treatment efficiency.

  • 22.
    Kyambadde, Joseph
    et al.
    KTH, Superseded Departments, Biotechnology.
    Kansiime, Frank
    Makerere University.
    Gumaelius, Lena
    KTH, Superseded Departments, Biotechnology.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Hydraulic loading, stability and water quality of Nakivubo wetland, Uganda2004In: African Journal of Aquatic Science, ISSN 1608-5914, E-ISSN 1727-9364, Vol. 29, no 2, p. 213-220Article in journal (Refereed)
    Abstract [en]

    Nakivubo wetland, which has performed tertiary water treatment for Kampala city for the past 40 years, is ecologically stressed by agricultural and infrastructural developments. Field studies were carried out to assess the hydraulic loading, pollution profile, stability and water quality of this wetland. The upper and lower Nakivubo wetland receive 4.13-7.66 x 104 and 3.50-10.32 X 104m3/day of water respectively, of which 48.3-57.9% of total hydraulic loading to the upper wetland was carried by sampling station S1. The influent water to the upper wetland had a total BOD5 and NH4-N loading ranging from 2.6-4.4 x 103kg BOD/day and 0.79-1.68 x 103kg NH4-N/day respectively. The National Water and Sewerage Corporation's effluent constituted a large proportion of BOD and NH4-N loading into Nakivubo wetland. Zinc, copper and chromium were detected in trace amounts at most sampling stations. However, lead was occasionally detected at Kibira channel (station S5) at a concentration of 0.4mg/l, which is higher than the permitted Ugandan discharge limit of 0.1mg/l (NEMA 1999). The wetland showed a very high removal efficiency for BOD, ranging from 77.4%-86.3%, compared to ammonium-N which ranged from -66.1% to 33.1% indicating limitations with the nitrification process. A low self-purification for zinc, copper and chromium was also observed in the upper Nakivubo wetland, possibly due to poor plant-wastewater interaction resulting from wetland drainage. In the lower Nakivubo wetland conductivity and dissolved oxygen were generally higher in papyrus- than in Miscanthidium-vegetated zones. However, the BOD and ammonium-N loadings did not vary significantly (P = 0.217 and P = 0.359 respectively) between the two vegetated zones.

  • 23.
    Larsdotter, Karin
    et al.
    KTH, School of Biotechnology (BIO), Bioprocess Technology.
    Jansen, Jes La Cour
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Biologically mediated phosphorus precipitation in wastewater treatment with microalgae2007In: Environmental technology, ISSN 0959-3330, E-ISSN 1479-487X, Vol. 28, no 9, p. 953-960Article in journal (Refereed)
    Abstract [en]

    A lab-scale continuous microalgal culture was grown on sterile-filtered wastewater in order to clarify the phosphorus removing mechanisms in a microalgal treatment step that treats residual phosphorus from a hydroponic wastewater treatment pilot plant. The phosphorus assimilation was dependent on algal biomass production, whereas the chemical precipitation was dependent on phosphorus load, i.e. an increase in average precipitation rate with decreased hydraulic retention time was observed. The chemical precipitation was mainly a result of the increased pH, which was biologically mediated by the photosynthesising algae. The precipitate was composed of a calcium phosphate with magnesium included, magnesium hydroxide and calcite. A significant nitrogen removal was also experienced, which implies that the microalgal wastewater treatment is appropriate both for phosphorus and nitrogen removal.

  • 24.
    Larsdotter, Karin
    et al.
    KTH, School of Biotechnology (BIO), Bioprocess Technology.
    Jansen, Jes La Cour
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Microalgae as a phosphorus trap after hydroponic wastewater treatmentManuscript (Other academic)
  • 25.
    Larsdotter, Karin
    et al.
    KTH, School of Biotechnology (BIO), Bioprocess Technology.
    Jansen, Jes la Cour
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO).
    Phosphorus removal from wastewater by microalgae in Sweden: a year-round perspective2010In: Environmental technology, ISSN 0959-3330, E-ISSN 1479-487X, Vol. 31, no 2, p. 117-123Article in journal (Refereed)
    Abstract [en]

    The phosphorus and nitrogen removing capacity of a microalgal treatment step in Sweden was studied during an annual cycle. The treatment step had been constructed for extended phosphorus removal in a hydroponic wastewater treatment system, which had been built in a greenhouse. Two culture depths (17 and 33 cm) were compared as well as the effect of additional illumination during winter. The results showed large fluctuations in algal biomass production and phosphorus removal as a result of season. The phosphorus removal efficiency showed a clear correlation with pH, and the shallow cultures generally had higher phosphorus removal efficiencies than the deeper cultures. The efficiencies were between 60% and 100% during summer but mostly lower than 25% during winter, except in the shallow culture with extra illumination where efficiencies of 60-80% were recorded even during winter. A nitrogen removal efficiency of around 40% was reached for most parts of the year, and efficiencies of up to 60-80% were achieved during summer in the shallow cultures. In conclusion, the results showed that a large proportion of the phosphorus could be removed on a year-round basis, hence reducing the need for chemical precipitation, and also that significant nitrogen removal is possible.

  • 26.
    Larsdotter, Karin
    et al.
    KTH, Superseded Departments.
    Norström, Anna
    KTH, Superseded Departments.
    Dalhammar, Gunnel
    KTH, Superseded Departments.
    Theoretical energy requirements for hydroponic wastewater treatment2004In: Vatten, ISSN 0042-2886, Vol. 60, p. 187-191Article in journal (Refereed)
    Abstract [en]

    Hydroponic wastewater treatment takes advantage of the nutrient removing capacity of green plants. In addition to the nutrient assimilation, the roots provide a growth substrate for microorganisms involved in the biological treatment processes. However, to maintain year-round performance by the plants, additional energy must be provided at higher latitudes, even if the hydroponics are situated in a greenhouse. To evaluate the energy demand by hydroponics in Sweden, two theoretical operational conditions have been compared. These conditions were based on A: requirements by winter resting plants, 10°C and 400 lux 16 h day-1, and B: good growth, 20°C and 2000 lux 16 h day-1. Further, five Swedish cities at different latitudes and their respective demands to reach the two conditions were compared. These cities were Lund (55°72' N), Visby (57°38' N), Stockholm (59°35' N), Östersund (63°20' N) and Kiruna (67°83' N). The calculations showed that under Swedish conditions, the extra heat demand always exceeds the light demand on a yearly basis except for the high temperature and light standard in Lund. The yearly light requirements are similar for the five cities, whereas the heat energy displays strong latitude dependence, e.g. the yearly heat demand in Kiruna is almost seven times higher than in Lund to reach an average indoor temperature of 10°C.

  • 27.
    Larsdotter, Karin
    et al.
    KTH, Superseded Departments.
    Norström, Anna
    KTH, Superseded Departments.
    Gumaelius, Lena
    KTH, Superseded Departments.
    Jansen, Jes La Cour
    Dalhammar, Gunnel
    KTH, Superseded Departments.
    A small scale hydroponics wastewater treatment system under Swedish conditions2003In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 48, no 11, p. 161-167Article in journal (Refereed)
    Abstract [en]

    A treatment plant using conventional biological treatment combined with hydroponics and microalgae is constructed in a greenhouse in the area of Stockholm, Sweden. The treatment plant is built for research purposes and presently treats 0.559 m(3) of domestic wastewater from the surrounding area per day. The system uses anoxic pre-denitrification followed by aerobic tanks for nitrification and plant growth. A microalgal step further reduces phosphorus, and a final sand filter polishes the water. During a three week period in July 2002 the treatment capacity of this system was evaluated with respect to removal of organic matter, phosphorus and nitrogen. 90% COD removal was obtained early in the system. Nitrification and denitrification was well established with total nitrogen reduction of 72%. Phosphorus was removed by 47% in the process. However, higher phosphorus removal values are expected as the microalgal step will be further developed. The results show that acceptable treatment can be achieved using this kind of system. Further optimisation of the system will lead to clean water as well as valuable plants to be harvested from the nutrient rich wastewater.

  • 28.
    Larsdottter, Karin
    et al.
    KTH, Superseded Departments.
    Söderbäck, E.
    Dalhammar, Gunnel
    KTH, Superseded Departments.
    Phosphorus removal from wastewater by microalgae in a greenhouse in Sweden.2004In: Water Environ. Manag. Ser., Vol. 3, p. 183-188Article in journal (Refereed)
  • 29.
    Leta, Seyoum
    et al.
    KTH, Superseded Departments, Biotechnology.
    Assefa, F.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Characterization of tannery wastewater and assessment of downstream pollution profiles along Modjo River in Ethiopia2003In: Ethiopian Journal of Biological Sciences, ISSN 1819-8678, Vol. 2, no 2, p. 157-168Article in journal (Refereed)
  • 30.
    Leta, Seyoum
    et al.
    KTH, School of Biotechnology (BIO).
    Assefa, F.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Enhancing biological nitrogen removal from tannery effluent by using the efficient Brachymonas denitrificans in pilot plant operations2005In: World Journal of Microbiology & Biotechnology, ISSN 0959-3993, E-ISSN 1573-0972, Vol. 21, no 4, p. 545-552Article in journal (Refereed)
    Abstract [en]

    Laboratory scale and pilot plant reactors were inoculated with an efficient denitrifier, Brachymonas denitrificans (CCUG 45880), in order to evaluate whether a bio-augmentation approach can be used to enhance biological nitrogen removal from tannery effluents. To determine the effectiveness of the introduced strain, denitrifying activity in the activated sludge was monitored by nitrate uptake rate ( NUR) measurement of NO3-N. Fluorescent in situ hybridization ( FISH) technique was used to monitor the growth of the augmented species. The laboratory scale nitrate removal efficiency with the introduced B. denitrificans (3.7 +/- 0.6 mg NO3-N gVSS(-1) h(-1)) was higher than that of the activated sludge without the addition of the bacteria (3.5 +/- 0.7 mg NO3-N gVSS(-1) h(-1)); the NUR in the pilot plant after and before the introduction of the strain was also of the magnitude of 12.0 +/- 1.4 and 10.6 +/- 1.4 mg NO3- N gVSS(-1) day(-1), respectively. In situ hybridization results revealed that the introduced denitrifying bacteria significantly facilitated the development of a dense denitrifying bacterial population in the activated sludge, which enhanced in situ denitrification activity. FISH data indicated that once introduced, B. denitrificans remained abundant throughout the experimental period. The ability to seed a bioreactor with bacterial strain capable of removing target pollutants from tannery effluents in a mixed microbial community suggests that this approach could have commercial applications.

  • 31.
    Leta, Seyoum
    et al.
    KTH, Superseded Departments, Biotechnology.
    Assefa, F.
    Gumaelius, Lena
    KTH, Superseded Departments, Biotechnology.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Biological nitrogen and organic matter removal from tannery wastewater in pilot plant operations in Ethiopia2004In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 66, no 3, p. 333-339Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to set-up a pilot plant and to evaluate its effectiveness for biological nitrogen and organic matter removal from tannery wastewater in Ethiopia. A pilot wastewater treatment plant consisting of a predenitrification-nitrification process was constructed and operated for 6 months. This was fed with a raw tannery wastewater obtained from the Modjo Tannery located 70 km south of the capital, Addis Ababa. Up to 98% total nitrogen and chemical oxygen demand, and 95% ammonium nitrogen removal efficiencies were achieved in the system. The average effluent ammonium nitrogen ranged from 8.4 mg l(-1) to 86.0 mg l(-1), whereas the average effluent for nitrate nitrogen ranged from 2.9 mg l(-1) to 4.4 mg l(-1). The average values of denitrification and nitrification rates determined by nitrate and ammonium uptake rates (NUR and AUR) were 8.0 mg NO3-N [g volatile suspended solids (VSS)](-1) h(-1) and 5.4 mg NH4-N (g VSS)(-1) h(-1), respectively, demonstrating that the treatment processes of the pilot plant were effective. Further studies of the effect of chromium III on AUR showed 50% inhibition at a concentration of 85 mg l(-1), indicating that this metal was not causing process inhibition during performance operations. Thus, the predenitrification-nitrification process was found to be efficient for simultaneous removal of nitrogen and organic substrates from tannery wastewaters.

  • 32.
    Leta, Seyoum
    et al.
    KTH, Superseded Departments, Biotechnology.
    Assefa, Fassil
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Protential of a predenitrification-nitrification process for biological sulphide removal from tannery effluentsManuscript (Other academic)
  • 33.
    Leta, Seyoum
    et al.
    KTH, Superseded Departments, Biotechnology.
    Gumaelius, Lena
    KTH, Superseded Departments, Biotechnology.
    Assefa, F.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    dentification of efficient denitrifying bacteria from tannery wastewaters in Ethiopia and a study of the effects of chromium III and sulphide on their denitrification rate2004In: World Journal of Microbiology & Biotechnology, ISSN 0959-3993, E-ISSN 1573-0972, Vol. 20, no 4, p. 405-411Article in journal (Refereed)
    Abstract [en]

    In order to identify potential microorganisms with high denitrifying capacity from tannery wastewaters, 1000 pure cultures of bacterial isolates from Modjo Tannery Pilot and Ethio-tannery wastewater treatment plants (WWTP), in Ethiopia, were investigated. Twenty-eight isolates were selected as efficient denitrifiers. These were Gram-negative rods, oxidase and catalase positive denitrifying organisms. The 28 denitrifying strains were further classified according to their biochemical fingerprints into three different phylogenetic groups (BPT1, BPT2 and BPT3) and seven singles. Isolates B79(T), B11, B12, B15, B28 and B38 belonging to the BPT3 cluster were found to be the most efficient denitrifying bacteria. All phenotypic studies, including cellular fatty acid profiles, showed that the 6 BPT3 isolates were closely related to each other. The 16S rRNA partial sequence analysis of type strain B79(T) (CCUG 45880) indicated a sequence similarity of 99% to Brachymonas denitrificans JCM9216 (D14320) in the beta-subdivision of proteobacteria. Further studies of the effects of chromium III and sulphide on the six Brachymonas denitrificans strains indicated that denitrification by the isolates were inhibited 50% at concentrations of 54 and 96 mg/l, respectively. The efficient isolates characterized in this study are of great value because of their excellent denitrifying properties and relatively high tolerance to the concentrations of toxic compounds (70 mg chromium/l and 160 mg sulphide/l) prevailing in tannery wastewaters.

  • 34.
    Marobhe, Nancy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Kuttuva, Gunaratna R.
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Effect of coagulant protein from Vigna and Parkinsonia seeds on bacteria isolated from Ruvu River in Tanzania2008In: World Journal of Microbiology & Biotechnology, ISSN 0959-3993, E-ISSN 1573-0972Article in journal (Other academic)
  • 35.
    Marobhe, Nancy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Kuttuva, Gunaratna R.
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Simple and rapid methods for purification and characterization of active coagulants from the seeds of Vigna unguiculata and Parkinsonia aculeata2007In: Environmental technology, ISSN 0959-3330, E-ISSN 1479-487X, Vol. 28, no 6, p. 671-681Article in journal (Refereed)
    Abstract [en]

    The coagulating properties of aqueous crude extracts and purified proteins of Vigna unguicilata and Parkinsomia aculeata seeds, which are traditional water coagulants in rural areas of Tanzania, were studied. The coagulation activity assays were done using one millilitre (ml) of kaolin water samples. Coagulating proteins were purified in two-step ion exchange chromatography. The properties of coagulant protein were compared with Moringa oleifera. Coagulating components eluted by 0.6 M NaCl in both coagulants are cationic proteins that have the molecular mass of about 6 kDa, which is very similar to that of M. oleifera. The proteins of V. unguiculata and P. aculeata eluted by 0.3 M NaCl also harbour coagulation activity but proteins eluted with 0.6 M NaCl have higher activity. The dosage for coagulation using purified proteins of both coagulants is about 5 to 10 times lower than that of crude seed extracts. The optimum floc settling time of water treated by crude seed extracts and purified proteins ranged between two and two and half hours. Coagulating proteins of both coagulants elated by 0.6 M NaCl are thermoresistant and retained coagulation activity of 87% to 92% after boiling for two hours at 80 degrees C and one hour at 95 degrees C. Thermotolerant proteins of V. unguiculata eluted by 0.6 M NaCl and P. aculeata have wider pH range of 5.5 to 8.5 for coagulation activity than those of M. oleifera proteins. The present investigation reveals the possibility of using purified natural coagulants for water treatment to produce safe drinking water.

  • 36. Mbwele, Lydia
    et al.
    Rajarao, Gunaratna
    Dalhammar, Gunnel
    Influence of microbial growth and carbon source in phosphorus uptake in wastewater treatmentManuscript (preprint) (Other academic)
  • 37. Mbwele, Lydia
    et al.
    Rajarao, Gunaratna
    Dalhammar, Gunnel
    Isolation of Phosphorus Removing Bacteria from a Waste Stabilisation Pond SystemManuscript (preprint) (Other academic)
  • 38.
    Mbwele, Lydia
    et al.
    KTH, Superseded Departments, Biotechnology.
    Rubindamayugi, M.
    Kivaisi, A.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Performance of a small wastewater stabilisation pond system in tropical climate in Dar es Salaam, Tanzania2003In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 48, no 11-12, p. 187-191Article in journal (Refereed)
    Abstract [en]

    Waste stabilisation ponds (WSP) are widely used in Tanzania. Their traditional design focuses on BOD and pathogen removal, but nutrient removal is equally important. WSP performance was evaluated to come up with information that would be used to evaluate pond performance. Samples were analysed twice a month for six months. Results showed total and faecal coliform removal by 4 log units (99.96 and 99.98% respectively). There was partial reduction of COD, BOD, (46% and 27% respectively), conductivity and total dissolved solids (32.6 and 32.4% respectively). Variation for the nutrients like inorganic phosphorus, ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen was not consistent and there was practically no reduction, although there is some nitrification taking place. From this study it may be concluded that BOD and nutrients may not be useful to evaluate pond performance. Instead parameters such as conductivity, total dissolved solids, coliform bacteria, dissolved oxygen, pH and chlorophyll would be suitable for that purpose, due to their consistent variation within cells of the pond system. But BOD and nutrient removal are important and have to be improved to enhance treatment in the WSP.

  • 39. Norstrom, Anna
    et al.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Lee, Natuschka M.
    The microbial characterization of a hydroponic treatment step for domestic wastewater - towards an expanded view on the plant-microbial hydroecology2008In: Journal of Environmental Engineering and Science, ISSN 1496-2551, E-ISSN 1496-256X, Vol. 7, no 6, p. 635-644Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to explore the microbial composition in the hydroponic step of a pilot plant for treatment of domestic wastewater under temperate climate conditions. The pilot plant was designed for nitrogen removal and operated at constant conditions. The microbial composition was investigated over a period of 6 month,; using fluorescence in situ hybridization (FISH) to identify key microbial groups. Nitrification rate measurements confirmed the presence and activity of aerobic nitrifying populations. The FISH analysis demonstrated that Proteobacteria, followed by Nitrospirae and Planctomycetes, represented the three most abundant bacterial groups. Interestingly, further FISH studies suggested the presence of one other bacterial group associated with ammonium-oxidizing processes: anaerobic ammonium-oxidizing bacteria within the Planctomycetales. This suggests that the nitrogen turnover in hydroponics systems may be attributed to more complex processes than previous models based only on those performed by aerobic ammonium-oxidizing bacteria.

  • 40.
    Norström, Anna
    et al.
    KTH, School of Biotechnology (BIO).
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO).
    Lee, Natuschka
    Investigation of the microbial composition in the hydroponic step of a treatment system for domestic wastewater with fluorescent in situ hybridization (FISH).In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992Article in journal (Other academic)
  • 41.
    Norström, Anna
    et al.
    KTH, School of Biotechnology (BIO).
    La Cour Jansen, Jes
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO).
    Energy savings versus year‐round production in a small hydroponic system for wastewater treatment.In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732Article in journal (Other academic)
  • 42.
    Norström, Anna
    et al.
    KTH, Superseded Departments, Biotechnology.
    Larsdotter, Karin
    KTH, Superseded Departments, Biotechnology.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Theoretical energy requirements for maintenance of green plants in hydroponic wastewater treatment.2004In: Vatten, ISSN 0042-2886, no 3, p. 187-191Article in journal (Other academic)
    Abstract [en]

    Hydroponic wastewater treatment takes advantage of the nutrient removing capacity of green plants. In addition to the nutrient assimilation, the roots provide a growth substrate for microorganisms involved in the biological treatment processes. However, to maintain year-round performance by the plants, additional energy muse be provided at higher latitudes, even if the hydroponics are situated in a greenhouse. To evaluate the energy demand by hydroponics in Sweden, two theoretical operational conditions have been compared. These conditions were based on A: requirements by winter resting plants, 10°C and 400 lux 16 h day-1, and B: good growth. 20°C and 2000 lux 16 h day-1. Further, five Swedish cities at different latitudes and their respective demands to reach the two conditions were compared. These cities were Lund (55°72' N), Visbv (57°38' N) Stockholm (59°35’ N), Ostersund (63°20’ N) and Kiruna (67°83’ N). The calculations showed that under Swedish conditions, the extra heat demand always exceeds the light demand on a yearlv basis except for the high temperature and light standard in Lund. The yearly light requirements are similar for the five cities, whereas the heat energy displays strong latitude dependence, e.g. the yearly heat demand in Kiruna is almost seven times higher than in Lund to reach an average indoor temperature of 10°C.

  • 43.
    Okoli, Chuka
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology. KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Fornara, Andrea
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Qin, Jian
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Characterization of Superparamagnetic Iron Oxide Nanoparticles and Its Application in Protein Purification2011In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 11, no 11, p. 10201-10206Article in journal (Refereed)
    Abstract [en]

    The application of surface modified magnetic adsorbent particles in combination with magnetic separation techniques has received considerable awareness in recent years. There is a particular need in protein purification and analysis for specific, functional and generic methods of protein binding on solid supports. Nanoscale superparamagnetic iron oxide particles have been used to purify a natural coagulant protein extracted from Moringa oleiferaseeds. Spectrophotometric analysis of the coagulant protein was performed using synthetic clay solution as substrate. Protein binding with carboxyl and silica surface modified superparamagnetic iron oxide nanoparticles (SPION) were compared with the known carboxyl methyl cellulose (CMC) beads of ∼1 m. SPION modified with carboxyl surface showed higher binding capacity towards the coagulant protein compared to the CMC beads. The high surface area to volume ratio of the carboxyl-coated SPION resulted in high binding capacity and rapid adsorption kinetics of the crude protein extract. The purification and molecular weight of coagulant protein is analyzed by SDS-PAGE. This approach utilizes the most efficient, feasible and economical method of coagulant protein purification and it can also be applicable to other proteins that possess similar properties.

  • 44.
    Ottoson, Jakob
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Norström, Anna
    KTH, School of Biotechnology (BIO).
    Dalhammar, Gunnel
    KTH, School of Biotechnology (BIO).
    Removal of micro-organisms in a small-scale hydroponics wastewater treatment system2005In: Letters in Applied Microbiology, ISSN 0266-8254, E-ISSN 1472-765X, Vol. 40, no 6, p. 443-447Article in journal (Refereed)
    Abstract [en]

    Aims: To measure the microbial removal capacity of a small-scale hydroponics wastewater treatment plant. Methods and Results: Paired samples were taken from untreated, partly-treated and treated wastewater and analysed for faecal microbial indicators, i.e. coliforms, Escherichia, coli, enterococci, Clostridium perfringens spores and somatic coliphages, by culture based methods. Escherichia coli was never detected in effluent water after >5.8-log removal. Enterococci, coliforms, spores and coliphages were removed by 4.5, 4.1, 2.3 and 2.5 log respectively. Most of the removal (60-87%) took place in the latter part of the system because of settling, normal inactivation (retention time 12.7 d) and sand filtration. Time-dependent log-linear removal was shown for spores (k = -0.17 log d-1, r2 = 0.99). Conclusions: Hydroponics wastewater treatment removed micro-organisms satisfactorily. Significance and Impact of the Study: Investigations on the microbial removal capacity of hydroponics have only been performed for bacterial indicators. In this study it has been shown that virus and (oo)cyst process indicators were removed and that hydroponics can be an alternative to conventional wastewater treatment.

  • 45. Sanden, B.
    et al.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Application of an amperometric immunosensor for the enumeration of Nitrobacter in activated sludge2000In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 54, no 3, p. 413-417Article in journal (Refereed)
    Abstract [en]

    A competitive immunosensor using a monoclonal antibody has been developed for the enumeration of Nitrobacter in activated sludge and other environmental samples. Its cross-reactivity was tested against a number of bacterial strains and isolates. All strains of the nitrite-oxidising genera Nitrobacter and Nitrococcus reacted strongly with the monoclonal antibody. The nitrite-oxidising Nitrospira moscoviensis, as well as the ammonia oxidising bacteria and the heterotrophic bacteria tested, did not show any affinity towards the antibody in the immunosensor. The numbers of Nitrobacter were analysed in sludge samples from several wastewater treatment plants in Sweden. Detectable amounts were found in all samples. This study shows the adequacy of using this immunosensor for the enumeration of Nitrobacter in natural environments.

  • 46. Svenson, A.
    et al.
    Sanden, B.
    Dalhammar, Gunnel
    KTH, Superseded Departments, Biotechnology.
    Remberger, M.
    Kaj, L.
    Toxicity identification and evaluation of nitrification inhibitors in wastewaters2000In: Environmental Toxicology, ISSN 1520-4081, E-ISSN 1522-7278, Vol. 15, no 5, p. 527-532Article in journal (Refereed)
    Abstract [en]

    In order to reduce the content of nitrogen in treated wastewater, microbial processes conducting nitrification of nitrogenous compounds and denitrification to gaseous nitrogen are included in the sewage wastewater treatment process. A set of compounds has been found inhibitory to these microorganisms. A procedure is presented for identification of nitrification inhibitors in wastewaters. This includes fractionation of the wastewater sample and location of the inhibitory effect using a nitrification inhibition assay where pure cultures of Nitrobacter are used. A series of unsaturated fatty acids and two monoterpenes were found to constitute the inhibitory effect in a wastewater sample from a plant for drying wood-derived fuel.

1 - 46 of 46
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