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Malmö, Sweden

Bernstad A.,Lund University | La Cour Jansen J.,Center for Chemistry and Chemical Engineering | Aspegren H.,VA SYD
Waste Management and Research | Year: 2011

The environmental impact of an extended property close source-separation system for solid household waste (i.e. a systems for collection of recyclables from domestic properties) is investigated in a residential area in southern Sweden. Since 2001, households have been able to source-separate waste into six fractions of dry recyclables and food waste sorting. The current system was evaluated using the EASEWASTE life cycle assessment tool. Current status is compared with an ideal scenario in which households display perfect source-separation behaviour and a scenario without any material recycling. Results show that current recycling provides substantial environmental benefits compared to a non-recycling alternative. The environmental benefit varies greatly between recyclable fractions, and the recyclables currently most frequently source-separated by households are often not the most beneficial from an environmental perspective. With optimal source-separation of all recyclables, the current net contribution to global warming could be changed to a net-avoidance while current avoidance of nutrient enrichment, acidification and photochemical ozone formation could be doubled. Sensitivity analyses show that thetype of energy substituted by incineration of non-recycled waste, as well as energy used in recycling processes and in the production of materials substituted by waste recycling, is of high relevance for the attained results. © The Author(s) 2011.

Gustavsson D.J.I.,VA SYD | La Cour Jansen J.,Lund University
Water Science and Technology | Year: 2011

Biological treatment in wastewater treatment plants (WWTPs) is a source of nitrogen oxides (N 2O, NO and NO 2) emitted to the atmosphere. Aerobic ammonia-oxidising bacteria (AOB) have been suggested to be the main source of these emissions. In a full-scale sludge liquor treatment plant at Sjölunda WWTP, it was shown that significant emissions of N 2O, NO and NO 2 do occur. The plant is operated with nitritation alone, which gives an environment enriched in aerobic AOB. During normal operation, emissions of N 2O, NO and NO 2 were found to be 3.8%, 0.06% and 0.01% of the ammonium nitrogen load. The N 2O emissions were larger than the recommended estimated figure of the Intergovernmental Panel on Climate Change (IPCC) for a complete wastewater treatment plant. The N 2O emissions correlated positively with the length of the previous anoxic period, i.e., settling and decantation, and with the ammonium oxidation rate. The NO and NO 2 emission profiles were similar and dependent on ammonium oxidation and DO level, but the NO 2 concentrations were always lower. © IWA Publishing 2011.

Bengtsson L.,Lund University | Milloti S.,VA SYD
Hydrological Processes | Year: 2010

Short-term very intensive storms in the years 1980-2007 from rain gauges in Malmö have been analysed to find intensities of long return periods and to investigate trends. Observations from different stations have been pooled into series to which probability functions have been adjusted. Quality control of short-term precipitation records is emphasized. In order to investigate whether high rain intensities are different today compared to back in time, new and old rain data have been compared. Trends over the last 25 years have been computed for storms of duration 10 min to 1 h, and for 89 years of daily rains. A literature review of investigations of changing rain intensities is presented. It is found that 10- to 25-year long rain series from single stations are too short to give good estimates of storms of long recurrence time because a single event influences much. The largest observed rains in Malmö in the investigated period have a return period of about 20-50 years. For the very short-term storms, 50-year old intensity-duration-frequency curves do not differ much from those derived from new data. Trend analysis shows changing short-term high storm intensities only for storms of 10-min duration. © 2010 John Wiley & Sons, Ltd.

Bernstad A.,Lund University | Davidsson T.,Lund University | Tsai J.,Lund University | Persson E.,Lund University | And 2 more authors.
Waste Management | Year: 2013

An unconventional system for separate collection of food waste was investigated through evaluation of three full-scale systems in the city of Malmö, Sweden. Ground food waste is led to a separate settling tank where food waste sludge is collected regularly with a tank-vehicle. These tank-connected systems can be seen as a promising method for separate collection of food waste from both households and restaurants. Ground food waste collected from these systems is rich in fat and has a high methane potential when compared to food waste collected in conventional bag systems. The content of heavy metals is low. The concentrations of N-tot and P-tot in sludge collected from sedimentation tanks were on average 46.2 and 3.9. g/kg TS, equalling an estimated 0.48 and 0.05. kg. N-tot and P-tot respectively per year and household connected to the food waste disposer system. Detergents in low concentrations can result in increased degradation rates and biogas production, while higher concentrations can result in temporary inhibition of methane production. Concentrations of COD and fat in effluent from full-scale tanks reached an average of 1068. mg/l and 149. mg/l respectively over the five month long evaluation period. Hydrolysis of the ground material is initiated between sludge collection occasions (30. days). Older food waste sludge increases the degradation rate and the risks of fugitive emissions of methane from tanks between collection occasions. Increased particle size decreases hydrolysis rate and could thus decrease losses of carbon and nutrients in the sewerage system, but further studies in full-scale systems are needed to confirm this. © 2012 Elsevier Ltd.

Gustavsson D.J.I.,VA SYD | Tumlin S.,Gryaab AB
Water Science and Technology | Year: 2013

This study estimates the carbon footprints of 16 municipal wastewater treatment plants (WWTPs), all situated in Scandinavian countries, by using a simple model. The carbon footprint calculations were based on operational data, literature emission factors (efs) and measurements of greenhouse gas emissions at some of the studied WWTPs. No carbon neutral WWTPs were found. The carbon footprints ranged between 7 and 108 kg CO2e P.E.-1 year-1. Generally, the major positive contributors to the carbon footprint were direct emissions of nitrous oxide from wastewater treatment. Whether heat pumps for effluents have high coefficient of performance or not is extremely important for the carbon footprint. The choice of efs largely influenced the carbon footprint. Increased biogas production, efficient biogas usage, and decreased addition of external fossil carbon source for denitrification are important activities to decrease the carbon footprint of a WWTP. © IWA Publishing 2013.

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