Ulrika Welander

Nitrification of landfill leachate using suspended-carrier biofilm technology

The possibility of nitrifying municipal landfill leachate using suspended-carrier biofilm technology was studied in three laboratory-scale reactors filled with three different types of carrier media. The effects of the temperature and the hydraulic retention time (HRT) on the volumetric nitrification rate were investigated. Steady-state nitrification rates were obtained in the processes after approximately 1 month of operation. The nitrification rate showed a rather weak dependence on the temperature, the rate at 5°C being approximately 77% of the rate at 20°C. The HRT had a more pronounced effect on the rate of nitrification, showing a considerable increase in nitrification rate with a decreased HRT. The highest efficiency was achieved for a carrier media consisting of small cubes of macroporous cellulose. A maximum nitrification rate of 40 g (NH+4-N)/(m3 reactor h) was obtained by use of this carrier at 20°C, an HRT of 14 h and a carrier filling degree of 10% of the reactor volume.

Denitrification at low temperatures using a suspended carrier biofilm process

The denitrification process was studied in a stirred lab-scale suspended carrier biofilm reactor at low temperatures (3-20 degrees C). The reactor was filled to 50% with Kaldnes K1 carriers. The denitrification rate showed only a rather weak dependence on the temperature, the rate at 3 degrees C being approximately 55% of that at 15 degrees C. The maximum denitrification rate obtained at 15 degrees C was 2.7 g NO(x)(-)-Nm(-2)carrier d (-1). The maximum denitrification rate at 3 degrees C during an 8-day period was found to be constant. During the 8 days, the hydraulic retention time was approximately 1.5h and the inlet NO(3)(-)-N concentration was 30 mg x l(-1).

Microbial Degradation of Organic Pollutants in Soil in a Cold Climate

Abstract Cold-adapted microorganisms are potentially interesting for use in environmental biotechnology applications since a large part of the biosphere has low temperatures during at least parts of the year. Many studies have shown that both oil-contaminated and uncontaminated soils in the Arctic, the Antarctic and the Alps contain microbes that can degrade different hydrocarbons deriving from oils. A few studies have also been conducted on degradation of herbicides in soils at low temperatures. Furthermore, phenols and some polychlorinated biphenyl (PCB) congeners have proved to be degradable at low temperatures, using microorganisms isolated from sediments or soils. Additions of nitrogen and phosphorous to polluted soils have been shown to enhance the degradation of hydrocarbons in many cases. Bioaugmentation with hydrocarbon degrading cold-adapted microorganisms has given varying results. The inoculated microorganisms have probably been out-competed by the indigenous microorganisms in some cases. Different ways to increase the efficiency of microbial degradation of organic pollutants in soil in a cold climate is discussed.

Physical and Chemical Treatment of a Nitrified Leachate from a Municipal Landfill

Leachate from a Swedish municipal landfill in the methanogenic phase was nitrified and then treated by various physical and chemical methods: oxidation with Fentons reagent and with ozone, precipitation with ferric chloride and with aluminum sulphate and adsorption onto activated carbon. The leachate was analyzed by measuring the COD (chemical oxygen demand), the BOD7 (biochemical oxygen demand) and the TOC (total organic carbon). Specific organic compounds were analyzed by GC/MS (gas chromatography and mass spectrometry) while the molecular weight of the organic matter was determined by ultrafiltration. The nitrification process resulted in 20–30% of the COD being removed. The maximum COD removed after nitrification and oxidation was 80% using Fentons reagent and 54% using ozone. The combination of nitrification and precipitation gave a maximum COD removal of 68% using ferric chloride and 54% using aluminum sulphate, while nitrification and adsorption onto activated carbon gave a maximum COD removal of...

Microbial diversity in a continuous system based on rice husks for biodegradation of the azo dyes Reactive Red 2 and Reactive Black 5

In the present study the degradation of two common azo dyes used in dye houses today, Reactive Black 5 and Reactive Red 2 was evaluated in biofilters. In two experiments, bioreactors performed over 80% decolorization at a hydraulic retention time of only 28.4h with little production of metabolites. Molecular analyses showed a diverse and dynamic bacterial community composition in the bioreactors, including members of the Bacteroidetes, Acinetobacter (Gammaproteobacteria) and Clostridium (Firmicutes) that possess the capacity to reduce azo dyes. Collectively, the results indicate that the development of mixed bacterial communities from natural biomaterials contributes to an efficient and robust degradation performance in bioreactors even at high concentration of dyes.

Precipitation of heavy metals from landfill leachates by microbially‐produced sulphide

Abstract Four leachates from two landfills in Sweden were treated for the removal of heavy metals with the aid of sulphate‐reducing bacteria (SRB). Both continuous and batch experiments were performed. A packed‐bed process was used for sulphide production. The metals studied were As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. The continuous experiments showed that Cd and Cu were most efficiently removed and that Cr was the most difficult to precipitate. In a continuous experiment with one of the leachates, the removal of Cd, Cu and Zn depended upon the retention time in the system. In the batch experiments, precipitation of the metals was a relatively fast process. No significant differences in metal concentrations were found between experiments terminated after a day and those terminated after a week. In a batch experiment involving one of the leachates, the precipitation of Cd and Cu was shown to be dependent upon the metal: sulphide ratio. Removal of the metals increased with an increase in the sulphide:metal ratio up to 45:1. The process with SRB showed an interesting potential for removal of heavy metals from leachates. One of the two leachates for which the highest metal removals were obtained came from a landfill for hazardous waste.

Hydrogen peroxide degradation by immobilized cells of alkaliphilic Bacillus halodurans

Whole cells of Bacillus halodurans LBK 261 were used as a source of catalase for degradation of hydrogen peroxide. The organism, B. halodurans grown at 55°C and pH 10, yielded a maximum catalase activity of 275 U g−1 (wet wt.) cells. The catalase in the whole cells was active over a broad range of pH with a maximum at pH 8–9. The enzyme was optimally active at 55°C, but had low stability above 40°C. The whole cell biocatalyst exhibited a Km of 6.6 mM for H2O2 and Vmax of 707 mM H2O2 min−1 g−1 wet wt. cells, and showed saturation kinetics at 50 mM H2O2. The cells were entrapped in calcium alginate and used for H2O2 degradation at pH 9 in batch and continuous mode. In the batch process, the immobilized preparation containing 1.5 g (wet wt.) cells could be recycled at least four times for complete degradation of the peroxide in 50 mL solution at 25°C. An excess of immobilized biocatalyst could be used in a continuous stirred tank reactor for an average of 9 days at temperatures upto 55°C, and in a packed bed reactor (PBR) for 5 days before the beads started to deform.

Decolorization of a mixture of textile dyes using Bjerkandera sp. BOL-13.

Abstract The white‐rot fungus Bjerkandera sp. BOL‐13 was evaluated regarding decolorization of four textile dyes Reactive blue 21, Reactive black 5, Reactive orange 13 and Reactive yellow 206. Experiments were performed in batch and continuous modes. The total dye concentration in all experiments was 100 mg l−1. The results of the batch experiments showed that the fungus decolorized all dyes but at different rates. There was, however, an increase in the ultraviolet (UV) absorbance when a medium with a low concentration of nitrogen was used. No increase in UV range was observed when the nitrogen concentration was increased. A continuous experiment was performed to study the decolorization of a mixture of three of the dyes Reactive blue 21, Reactive black 5 and Reactive orange 13. Scanning of inlet and outlet samples showed that the absorbance at the peaks in the visible range decreased by 60–66%. The UV absorbance of the outlet increased during the first days of operation after which it decreased again to reach the same level as the inlet. The hydraulic retention time in the reactor was 3 days. The medium containing the higher nitrogen concentration was used in the continuous experiment.

Degradation of organic compounds in a municipal landfill leachate treated in a suspended-carrier biofilm process

Degradation of organic compounds in a municipal landfill leachate treated in a suspended-carrier biofilm process

Energy performance and greenhouse gas emissions of kelp cultivation for biogas and fertilizer recovery in Sweden

The cultivation of seaweed as a feedstock for third generation biofuels is gathering interest in Europe, however, many questions remain unanswered in practise, notably regarding scales of operation, energy returns on investment (EROI) and greenhouse gas (GHG) emissions, all of which are crucial to determine commercial viability. This study performed an energy and GHG emissions analysis, using EROI and GHG savings potential respectively, as indicators of commercial viability for two systems: the Swedish Seafarm projects seaweed cultivation (0.5ha), biogas and fertilizer biorefinery, and an estimation of the same system scaled up and adjusted to a cultivation of 10ha. Based on a conservative estimate of biogas yield, neither the 0.5ha case nor the up-scaled 10ha estimates met the (commercial viability) target EROI of 3, nor the European Union Renewable Energy Directive GHG savings target of 60% for biofuels, however the potential for commercial viability was substantially improved by scaling up operations: GHG emissions and energy demand, per unit of biogas, was almost halved by scaling operations up by a factor of twenty, thereby approaching the EROI and GHG savings targets set, under beneficial biogas production conditions. Further analysis identified processes whose optimisations would have a large impact on energy use and emissions (such as anaerobic digestion) as well as others embodying potential for further economies of scale (such as harvesting), both of which would be of interest for future developments of kelp to biogas and fertilizer biorefineries.