| 1. |
- Johansson, Lena, 1967-
(författare)
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The use of LECA (Light Expanded Clay Aggregates) for the removal of phosphorus from wastewater
- 1997
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Ingår i: Water Science and Technology. - 0273-1223 .- 1996-9732. ; 35:5, s. 87-93
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Tidskriftsartikel (refereegranskat)abstract
- Increasing attention is being focused on the phosphorus retention capacity of wetlands. Several attempts have been made to improve the reduction of phosphorus in wastewater by the use of constructed wetlands. One way of improving the phosphorus reduction capacity is to use efficient filter materials in the wetland. Leca(R) (Light Expanded Clay Aggregates) has been tested in Norway, where laboratory and field investigations gave promising results. To further study the chemical removal mechanism of Leca, an experiment utilising five columns was performed. A phosphate solution was applied to the columns intermittently and samples were taken twice a week. Parallel to this study, a P-fractionation experiment was conducted to find out how the phosphate was sorbed to various components of the material. Both experiments showed that only a small amount of the applied phosphate was sorbed by the Leca. The amount sorbed was primarily attached to Al-complexes. In a second column experiment Opoka, a reactive medium rich in CaCO3, was added to Leca and sand to investigate the P-sorption capacity. The results from this investigation showed a higher P-uptake than in the previous column experiment. The lime additive clearly increased the P-sorption and, in this study, Leca in its pure form could be considered as chemically non-reactive.
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| 2. |
- Karlsson, Susanne, 1967-, et al.
(författare)
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Drinking water off-flavour caused by the formation of short-chain fatty acids in slow sand filters
- 1995
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Ingår i: Water Science and Technology. - 0273-1223 .- 1996-9732. ; 31:11, s. 49-54
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Tidskriftsartikel (refereegranskat)abstract
- A case study carried out at a municipal drinking water treatment plant in southern Sweden showed that the formation of short-chain fatty acids in slow sand filters can result in severe off-flavour problems. When an extract of the headspace of the surface layer of a sand filter was subjected to gas chromatographic analysis with sensory detection (GC sniffing), several strong, rancid odours were detected. Mass spectrometric analysis of the same extract, before and after methylation, showed that substantial amounts of butyric acid, valeric acid and isovaleric acid were present in the analysed sample. The off-flavour caused by these compounds was removed by repeated shock chlorination of the malfunctioning slow sand filter. Analysis of fatty acid esters may provide an early warning of the described off-flavour problem.
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| 3. |
- Rosen, B, et al.
(författare)
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A systematic approach to optimal upgrading of water and waste water treatment plants
- 1998
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Ingår i: Water Science and Technology. - 0273-1223 .- 1996-9732. ; 37:9, s. 9-16
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Tidskriftsartikel (refereegranskat)abstract
- Most of the future works in water and waste water treatment systems will involve the upgrading of existing facilities, for better performance and/or higher capacity. For the efficient implementation of any project, an upgrading strategy should be used, based on careful studies of the local conditions and the defined objectives to be reached. The paper presents a systematic approach to upgrading with emphasis on treatment plant extension, without investing in large volumes, by more efficient use of existing facilities, illustrated by some cases. The importance of real competition in obtaining a cost-effective implementation is stressed.
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| 4. |
- Alkan Olsson, Johanna, et al.
(författare)
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How participatory can participatory modeling be? Degrees of influence of stakeholder and expert perspectives in six dimensions of participatory modeling
- 2007
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 56:1, s. 207-214
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Tidskriftsartikel (refereegranskat)abstract
- The authors are involved in a project aiming at the development of a methodology for participatory modeling as a tool for public participation in water resource management. In this paper, some examples of different degrees of stakeholder influence in six key dimensions of participatory modeling are identified and discussed. Arnstein's (A ladder of citizen participation. Journal of the American Institute of Planners, 1969, 4, 216–224) critical discussion of different degrees of “real” decision-making power is taken as a point of departure to assess possible degrees of stakeholder influence. Can we as participatory modelers be sure that we are really inviting our research objects to an equal communicative relationship where local perspectives, knowledge and priorities are respected to the same extent as central and/or expert perspectives? This paper presents an approach that could be used as a tool for structured reflection to avoid unreflective tendencies towards expert knowledge dominance and low degree of stakeholders' real influence over the process.
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| 5. |
- Alpkvist, Erik, et al.
(författare)
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A new mathematical model for chemotactic bacterial colony growth
- 2004
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Ingår i: Water Science and Technology. - : Biriwa Education Services. - 0273-1223 .- 1996-9732. ; 49:11-12, s. 187-192
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Tidskriftsartikel (refereegranskat)abstract
- A new continuum model for the growth of a single species biofilm is proposed. The geometry of the biofilm is described by the interface between the biomass and the surrounding liquid. Nutrient transport is given by the solution of a semi-linear Poisson equation. In this model we study the morphology of a chemotactic bacterial colony, which grows in the direction of increasing nutrient concentration. Numerical simulations using the level set method and finite difference schemes are presented. The results show rich heterogeneous morphology.
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| 6. |
- Alpkvist, Erik, et al.
(författare)
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Description of mechanical response including detachment using a novel particle model of biofilm/flow interaction
- 2007
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Ingår i: Water Science and Technology. - : Biriwa Education Services. - 0273-1223 .- 1996-9732. ; 55:8-9, s. 265-273
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial biofilms, while made up of microbial-scale objects, also function as meso- and macro-scale materials. In particular, macro-scale material properties determine how biofilms respond to large-scale mechanical stresses, e.g. fluid shear. Viscoelastic and other constitutive properties influence biomass structure (through growth and fluid shear stresses) by erosion and sloughing detachment. In this paper, using the immersed boundary method, biofilm is modelled by a system of viscoelastic, breakable springs embedded in a fluid flow, evolving according to the basic physical laws of conservation of mass and momentum. We demonstrate in the context of computer simulation biofilm deformation and detachment under fluid shear stress.
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| 7. |
- Alpkvist, Erik, et al.
(författare)
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Simulation of nitrification of municipal wastewater in moving-bed biofilm process : approach based on a 2D continuum model for growth and detachment
- 2007
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Ingår i: Water Science and Technology. - : Biriwa Education Services. - 0273-1223 .- 1996-9732. ; 55:8-9, s. 247-255
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a complete mathematical model of a Moving Bed biofilm process for waste-water treatment, in particular for the nitrification process. The model is based on a bottom up approach adopting a multidimensional model for the biofilm growth and metabolism and a global mass balance model for the whole reactor. The model shows that oxygen is limiting the amount of biomass involved in the nitrification process. Furthermore, it suggests the existence of an optimal amount biomass for an optimal reactor turnover rate. Studies of two specific new suspended carriers show that the model output is dependable on the geometry of the carrier, and to a satisfactory extent agreeable with measurements.
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| 8. |
- Amaral, Andreia, et al.
(författare)
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Modelling gas-liquid mass transfer in wastewater treatment : when current knowledge needs to encounter engineering practice and vice versa
- 2019
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Ingår i: Water Science and Technology. - : NLM (Medline). - 0273-1223 .- 1996-9732. ; 80:4, s. 607-619
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Tidskriftsartikel (refereegranskat)abstract
- Gas-liquid mass transfer in wastewater treatment processes has received considerable attention over the last decades from both academia and industry. Indeed, improvements in modelling gas-liquid mass transfer can bring huge benefits in terms of reaction rates, plant energy expenditure, acid-base equilibria and greenhouse gas emissions. Despite these efforts, there is still no universally valid correlation between the design and operating parameters of a wastewater treatment plant and the gas-liquid mass transfer coefficients. That is why the current practice for oxygen mass transfer modelling is to apply overly simplified models, which come with multiple assumptions that are not valid for most applications. To deal with these complexities, correction factors were introduced over time. The most uncertain of them is the α-factor. To build fundamental gas-liquid mass transfer knowledge more advanced modelling paradigms have been applied more recently. Yet these come with a high level of complexity making them impractical for rapid process design and optimisation in an industrial setting. However, the knowledge gained from these more advanced models can help in improving the way the α-factor and thus gas-liquid mass transfer coefficient should be applied. That is why the presented work aims at clarifying the current state-of-the-art in gas-liquid mass transfer modelling of oxygen and other gases, but also to direct academic research efforts towards the needs of the industrial practitioners.
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| 9. |
- Amneklev, Jennie, et al.
(författare)
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Upstream silver source mapping - a case study in Stockholm, Sweden
- 2014
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 69:2, s. 392-397
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Tidskriftsartikel (refereegranskat)abstract
- Silver (Ag) can be a problem for wastewater treatment plants (WWTP) and their capability to use sewage sludge as a soil fertilizer. Due to a high accumulation rate in soils, the levels of Ag in the incoming water at the WWTP must be reduced. This study aims to identify major diffuse emission sources in the technosphere through a comprehensive substance flow analysis of Ag in Stockholm, Sweden. Large inflows and stocks of Ag were present in electrical and electronic goods and appliances as well as in jewellery and silverware. The total inflow was 3.2 tonnes (4.2 g/person), the total stock was 100 tonnes (140 g/person) and the total outflow was 330 kg (430 mg/person). Major identified Ag sources with emissions ending up in the WWTP (total 26 kg, 34 mg/person) were food, amalgam and beauty products (via urine and faeces, 12 mg/person or 11% of incoming amount), and textiles (via washing, 17 mg/person or 16% of incoming amount). This study explains approximately 35% of the total 80 kg Ag in the incoming water at Henriksdal WWTP in Stockholm. Plastic, photography and beauty products were identified as possible sources of Ag that need to be examined further.
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| 10. |
- Andersen, Henrik Rasmus, et al.
(författare)
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Estrogenic personal care products in a greywater reuse system
- 2007
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 56:12, s. 45-49
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Tidskriftsartikel (refereegranskat)abstract
- The occurrence and fate of parabens in a greywater system was assessed. The potential for removal of residual paraben concentrations in effluent greywater with chlorine dioxide was also investigated. The influent to the greywater plant was characterised by considerable variation, with concentrations from below the detection limit to 40 μg/L and the five commonly used parabens in consumer products were frequently detected. After the biological treatment only two paraben were detected with concentration from 65–120 ng/L. Chlorine dioxide treatment of the biologically treated effluent with dosages down to 0.75 mg/L resulted in more than 97% reduction of all parabens. Formation of the by-product chloroform was insignificant from the chlorine dioxide treatment.
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