| 1. |
- Alexandersson, Tomas, et al.
(författare)
-
Biological treatment of whitewater in a laboratory process in order to determine kinetic parameters for model development
- 2004
-
Ingår i: Water Science and Technology. - 0273-1223. ; 50:3, s. 195-206
-
Tidskriftsartikel (refereegranskat)abstract
- Implementation of an in-mill biological treatment plant is one solution to the problems associated with closure of whitewater systems. It is, however, important to operate the treatment with low concentration of nutrients in the effluent. The effect on the COD reduction from decreased additions of NH4-N and PO4-P were investigated in three parallel aerobic suspended carrier reactors during treatment at 46 to 48degreesC of whitewater from a recycled paper mill producing liner and fluting. In the reference reactor, a COD reduction of 89% was achieved and 45.6 mg NH4-N/(g COD reduced) and 11.6 mg PO4-P/(g COD reduced) was consumed at an organic load around 20 kg COD/(m(3.)d). Reduced additions of NH4-N decreased the COD reduction. Addition of 56% of the consumption of NH4-N in the reference reactor resulted in a COD reduction of 80%. The response from decreased addition of PO4-P was different compared to NH4-N but it could not be determined if this is due to unsuitable experimental design or a different reaction mechanism. Reducing the addition of PO4-P to 26% of the consumption of PO4-P in the reference reactor, decreased the COD reduction to 83%. The main conclusion from the experiment is: biological treatment has the potential of treating whitewater from recycled paper mills with low effluent nutrient concentrations.
|
|
| 2. |
- Alpkvist, Erik, et al.
(författare)
-
A new mathematical model for chemotactic bacterial colony growth
- 2004
-
Ingår i: Water Science and Technology. - : Biriwa Education Services. - 0273-1223 .- 1996-9732. ; 49:11-12, s. 187-192
-
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.
|
|
| 3. |
- Batstone, Damien, et al.
(författare)
-
Industrial applications of the IWA anaerobic digestion model No. 1 (ADM1)
- 2003
-
Ingår i: Water Science and Technology. - 0273-1223. ; 47:12, s. 199-206
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the IWA anaerobic digestion model No. 1 (ADM1) is applied to two case studies from contract work on industrial treatment plants. The first was the assessment of acid addition for pH decrease and avoidance of calcium carbonate (CaCO3) precipitation in a paper mill fed UASB. The simulation work found, with a high degree of confidence, that acid dosing was neither economical for pH control, nor had any real effect on the CaCO3 levels present in the reactor. A specific calcium carbonate precipitation equation was added to the ADM1 to undertake this study. The second case study was an assessment of the benefits of thermophilic (as opposed to mesophilic operation) for reduced ammonia inhibition, improved stability and gas production in a solids digester at a gelatine production facility. Here, it was predicted that thermophilic operation could not attain either goal to a satisfactory extent. In addition to demonstrating the application of the ADM1 to the two systems, we have also assessed the predictions generated in the case studies in terms of quality and utility.
|
|
| 4. |
- Biswas, AK, et al.
(författare)
-
Workshop 3 (synthesis) : water, poverty alleviation and social programs
- 2003
-
Ingår i: Water Science and Technology. - 0273-1223 .- 1996-9732. ; 47:6, s. 129-132
-
Tidskriftsartikel (refereegranskat)abstract
- Poverty is a complex issue, which must be understood in a holistic manner. Low and variable income is certainly a key element, but it is far from enough to portray poverty. The various characteristics of poverty and their relative strength are determined through contextually specific circumstances, in terms of history, environmental preconditions, socio-cultural traits, etc. Much of this context is made up of local and national circumstances. The consequences of globalisation must, however, increasingly to be taken into account. At a larger scale, it is also relevant to mention that climate change will have a negative, although largely unpredictable, impact for the people in some parts of the world. For those who are already living on marginal lands or who are exposed to water problems, climate change is likely to create considerable adverse effects.
|
|
| 5. |
- Brion, G, et al.
(författare)
-
Probing Norwalk-like virus presence in shellfish, using artificial neural networks.
- 2004
-
Ingår i: Water Science and Technology. - 0273-1223 .- 1996-9732. ; 50:1, s. 125-9
-
Tidskriftsartikel (refereegranskat)abstract
- A database was examined using artificial neural network (ANN) models to investigate the efficacy of predicting PCR-identified Norwalk-like virus presence and absence in shellfish. The relative importance of variables in the model and the predictive power obtained by application of ANN modelling methods were compared with previously developed logistic regression models. In addition, two country-specific datasets were analysed separately with ANN models to determine if the relative importance of the input variables was similar for geographically diverse regions. The results of this analysis found that ANN models predicted Norwalk-like virus presence and absence in shellfish with equivalent, and better, precision than logistic regression models. For overall classification performance, ANN modelling had a rate of 93%, vs 75% for the logistic regression. ANN models were able to illuminate the site-specific relationships between indicators and pathogens.
|
|
| 6. |
- Bäckström, Magnus
(författare)
-
Grassed swales for stormwater pollution control during rain and snowmelt
- 2003
-
Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 48:9, s. 123-134
-
Tidskriftsartikel (refereegranskat)abstract
- The retention of suspended solids, particles and heavy metals in different grassed swales during rain events and snowmelt is discussed. The experimental results derived from investigations performed in existing grassed swales in the Luleae. region, Northern Sweden. During high pollutant loading rates, grassed swales retain significant amounts of pollutants, mainly due to sedimentation of particulate matter. Low to moderate removal efficiencies could be expected for heavy metals, especially metals in solution (i.e. the dissolved phase). When grassed swales receive urban runoff with low pollutant concentrations, they may release rather than retain pollutants. Swales are important snow deposit areas in the city and particle bound pollutants do to a large extent remain in the swale after snowmelt. However, dissolved pollutants (i.e. dissolved heavy metals) are likely to escape the swale with the melt water. Grassed swales may be regarded as facilities that even out the peaks in pollutant loads without being capable of producing consistent high removal rates. This suggests that swales should be considered as primary treatment devices. Possible design parameters for grassed swales are mean hydraulic detention time, surface loading rate or specific swale area.
|
|
| 7. |
- Bäckström, Magnus
(författare)
-
Sediment transport in grassed swales during simulated runoff events
- 2002
-
Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 45:7, s. 41-49
-
Tidskriftsartikel (refereegranskat)abstract
- Particle trapping in nine different grassed swales was measured successfully with a standardised runoff event simulation procedure. The percentage of total suspended solids removed ranged from 79 to 98%. It was found that sedimentation processes, rather than grass filtration governed the overall particle trapping efficiency. The highest particle trapping efficiency was observed in the field swales with dense, fully developed turf. A high infiltration rate was beneficial for the particle trapping and an increased swale length made it possible for smaller particles to be captured. A densely vegetated, ten metre long swale, receiving a stormwater flow of 1.0 litres per second, may capture a majority of the waterborne particles with settling velocities larger than 0.1 metres per hour. A simple model of particle trapping efficiency in grassed swales was developed and tested. It was found that mean swale residence time could be used as a design parameter for particle removal in grassed swales. The suggested exponential relationship between mean swale residence time and particle settling velocity associated with a certain trapping efficiency is so far only valid for a limited range of swale designs and residence times.
|
|
| 8. |
- Bäckström, Magnus, et al.
(författare)
-
Stormwater management in a catchbasin perspective - best practices or sustainable strategies?
- 2002
-
Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 46:6-7, s. 159-166
-
Tidskriftsartikel (refereegranskat)abstract
- A strategy for sustainable stormwater management is needed. This study has focused on the relative importance of stormwater as a pollutant source in a catchbasin, if Best Management Practices (BMPs) result in pollutant removal or pollutant redistribution, and methods for screening of stormwater strategies. Stormwater is most likely an important pathway for pollutants in a catchbasin perspective. True pollutant removal can only be achieved if the pollutant sources are eliminated. Until that is reached, we should have the best possible control of the pollutant fluxes in the watershed. This study indicates that the search for a sustainable stormwater strategy could be easier to handle if different "screens" could be used. The Swedish environmental objectives, which try to encapsulate all aspects of sustainability, may be used as a foundation for a "sustainability screen". By using this screen, the "unsustainable" features of different stormwater strategies could be pointed out. A "standards and legislation screen" will be based on the EU Water Framework Directive. As this study has shown, it is doubtful whether the conventional BMPs, such as stormwater ponds and infiltration facilities, produce a sufficient pollutant control.
|
|
| 9. |
- Cimbritz, Michael, et al.
(författare)
-
Particle-visualisation - a tool for determination of rise velocities
- 2004
-
Ingår i: Water Science and Technology. - 0273-1223. ; 50:12, s. 229-236
-
Tidskriftsartikel (refereegranskat)abstract
- Particles from post denitrifying Kaldnes Moving Bed(TM) Process were studied using an optical borescope, a visualisation technique that provides opportunities for both qualitative and quantitative studies of the separation mechanism in Dissolved Air Flotation (DAF). Rise rates for particle/bubble aggregates were estimated showing great variability. Two groups of aggregates were distinguished; relatively small floes (<100 mum) with single bubble's attached rising comparatively slowly and large flocs (>100 mum) with several bubbles attached rising very fast. The high rise rates for large aggregates are discussed, possibly explained and suggested as the reason for the effective separation of large particles noticed in previous studies. Removal efficiency of different size categories of particles in DAF were investigated on the basis of particle size analysis indicating increased separation efficiency with increasing particle size.
|
|
| 10. |
- Cimbritz, Michael, et al.
(författare)
-
Separation characteristics in dissolved air flotation - pilot and full-scale demonstration
- 2003
-
Ingår i: Water Science and Technology. - 0273-1223. ; 48:3, s. 89-96
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents practical implications for particle separation in Dissolved Air Flotation (DAF). The objectives were to localise where particles are separated from the water phase and to determine what particles, in terms of size, are removed by the DAF-process. Both pilot- and full-scale plants were investigated. Particle sizes were analysed with a light-blocking particle counter and an optical borescope was used for visualisation of particle-bubble aggregates. It was found that particles are preferably separated upstream in the process, i.e. close to the contact zone. Furthermore, separation efficiency for particles increased with increasing particle size.
|
|
