| 1. |
- Aspegren, H., et al.
(author)
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The Urban Water System - a Future Swedish Perspective
- 1997
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In: Water Science and Technology. - 0273-1223. ; 35:9, s. 33-44
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Journal article (peer-reviewed)abstract
- It is argued, that the use of water can no longer be regarded as an almost free commodity. The idea to assess and value the environmental impact of the water use represents a true change of paradigm. The key issue is that any future wastewater treatment system has to be evaluated according to a quantitative criterion. This has to consider: •hygienic aspects: we believe that nobody will accept a lower hygienic standard than today. •environmental impact: the wastewater impact on the environment has steadily increased the need for better treatment. We need to be prepared for changes in the society by having a readiness manifested as continuing dynamic research environment in this area. Too often the knowledge build-up has been re-active instead of pro-active. •economising resources: wastewater treatment looks and probably should look quite different in densely populated urban areas and in rural areas. Considering resource handling one has to consider already invested capital costs, land use, water re-use, organic and nutrient use and re-use, as well as overall use of energy. •user aspects: technical functionality, economy and liability in different aspects require profound consideration. A sustainable wastewater treatment has to adapt to a local environment and the total resource demand has to be calculated, including a direct environmental impact on receiving waters, air and soil as well as energy consumption and nutrient recycling. Thus, there is an apparent need for. •quantitative performance index: the quest for sustainable development has to be based on objective reasons as well as subjective ones. An integrated performance index is part of a necessary decision making model for the design and operation of wastewater treatment systems. In this index, it is evident that a trade-off should be made between the pursued quality of the process outputs (liquid, solids, gas) and the associated efforts (investments, operation) required to achieve this considering the inputs (wastewater). In order to make this trade-off, however, a common framework is needed to quantitatively compare the different objectives. A metric to judge the sustainability of different options will facilitate a fruitful dialogue between e.g. politicians, ecologists, engineers and economists. Only a truly interdisciplinary approach can help to solve the challenges ahead.
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| 2. |
- Jeppsson, Ulf, et al.
(author)
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An evaluation of a dynamic model of the secondary clarifier
- 1996
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In: Water Science and Technology. - : IWA Publishing. - 0273-1223. ; 34:5, s. 19-26
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Journal article (peer-reviewed)abstract
- The main objective of the paper is to support and illustrate recent theoretical results on the mathematical modelling of the secondary clarifier. A new settler model is compared with a traditional layer model by means of numerical simulations. Emphasis is put on the numerical solution's ability to approximate the analytical solution of the conservation law written as a non-linear partial differential equation. The new settler model is consistent in this respect. Another important conclusion is that a layer model dividing the settler into only ten layers (normally used in settler models) is too crude an approximation to capture the detailed dynamic behaviour of the settler. All simulations presented are performed with the settler models coupled to the IAWQ Activated Sludge Model No. 1.
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| 3. |
- Jeppsson, Ulf, et al.
(author)
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On the modelling of the dynamic propagation of biological components in the secondary clarifier
- 1996
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In: Water Science and Technology. - : IWA Publishing. - 0273-1223. ; 34:5, s. 85-92
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Journal article (peer-reviewed)abstract
- When coupling a model of the biological reactor to a model of the settler, difficulties appear because of the different representations used for the particulate material. A combined model of the entire activated sludge process needs to include an algorithm for the dynamic propagation of the biological components of the particulate material through the secondary clarifier. In particular, this is of importance for an accurate description of the sludge that is recycled to the biological reactor. Two one-dimensional algorithms have been evaluated by means of numerical simulations. The first algorithm investigated is the one by Otterpohl and Freund in 1992 and some inherent problems of this method are discussed. For example, it will produce oscillating solutions as the number of layers in the settler model increases. Therefore, an alternative algorithm is proposed. It is based on a percentage vector that describes the different particulate biological components as fractions of the total suspended solids concentration. The vector is updated for every layer in the settler model by a robust numerical method. The algorithm is derived analytically, is computationally efficient and does not exhibit any oscillatory behaviour.
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| 4. |
- Jönsson, Karin, et al.
(author)
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Screening method for evaluation of inhibition of nitrification in Sweden
- 1999
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In: Water Science and Technology. - 0273-1223. ; 40:2, s. 175-178
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Journal article (peer-reviewed)abstract
- An investigation with respect to inhibition of nitrification of wastewater from 109 Swedish municipal wastewater treatment plants was performed. Flow proportional, 24-hour composite samples were collected during one week, and then analysed using the screening method. Inhibition of nitrification above 10% was found at only 20 plants. In general, the load of inhibiting substances is limited in Swedish municipal wastewater according to this study. The inhibition found is not connected to any special category of treatment plants with respect to the size of the plant. Neither was any general pattern of inhibition during the week found in this investigation. It was also shown that the screening method can be used for detecting small quantities of inhibiting substances if different dilutions of the same sample are analysed.
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| 5. |
- Olsson, Gustaf, et al.
(author)
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Operation and Control of Wastewater Treatment - A Scandinavian Perspective over 20 years
- 1998
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In: Water Science and Technology. - 0273-1223. ; 37:12, s. 1-13
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Journal article (peer-reviewed)abstract
- This paper aims to review the development of wastewater treatment operation and control over the last two decades. Due to the authors' background and experiences there is a special emphasis on the Scandinavian perspective. Since the developments in these countries have been in the forefront in the wastewater treatment area we believe that it may give a reasonable view of the progress also in other countries. The results of regulatory, technical and economical driving forces are discussed. A brief historical review of the progress of nutrient removal is made, and current methodologies for the operation and control of nutrient removal systems is reviewed.
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| 6. |
- Olsson, Gustaf, et al.
(author)
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Reviewing, assessing and speculating
- 1998
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In: Water Science and Technology. - 0273-1223. ; 37:12, s. 397-401
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Journal article (pop. science, debate, etc.)abstract
- A concise assessment is made of the scientific and technical programme of the 7th IAWQ Workshop on Instrumentation, Control and Automation of Water and Wastewater Treatment and Transport Systems. Although progress has been made in certain areas, others are identified as crucial targets for further research and development.
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| 7. |
- Rosén, Christian, et al.
(author)
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Disturbance detection in wastewater treatment plants
- 1998
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In: Water Science and Technology. - 0273-1223. ; 37:12, s. 197-205
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Journal article (peer-reviewed)abstract
- The development in sensor technology has made many wastewater treatment systems data rich but not necessarily information rich. To extract the adequate information from several sensors is not trivial, and it is not sufficient to consider only the time series. Different tools for detecting unusual on-line measurement data and deviating process behaviour are discussed. In this paper various dimension reduction as well as advanced filtering methods are considered in order to extract adequate information for fault detection and diagnosis. Both the operator and the process engineer can take advantage of such methods for proper monitoring of the plant, in particular extreme events and their causes.
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| 8. |
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| 9. |
- Adamsson, Marie, 1966, et al.
(author)
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Toxicity Identification Evaluation of ammonia, nitrite and heavy metals at the Stensund Wastewater Aquaculture plant, Sweden.
- 1998
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In: Water Science and Technology. - 0273-1223. ; 38:3, s. 151-157
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Journal article (peer-reviewed)abstract
- The Stensund Wastewater Aquaculture plant was built in 1989. The plant is contained in a greenhouse because of its northern location with a temperate climate; The plant receives wastewater from 40 persons and has a residence time of 30 days. The purification concept is to use a constructed aquatic food chain (algae, zooplankton and fish) combined with hydroponic culture of higher plants to further deplete the nutrients in the wastewater. However, the production of algae and zooplankton has not been working as expected from pilot studies. The purpose of this investigation was to study if toxic chemicals were limiting the production of zooplankton (Daphnia magna) in the aquaculture treatment system. Grab samples were taken at six sites and tested for acute toxicity to Daphnia magna and analyzed for BOD, COD, ammonium-, nitrite-, nitrate- and total nitrogen, total phosphorus and heavy metals (Cd, Ci, Cu, Ni, Pb, Zn). Toxicity to D. magna was also determined after addition of EDTA, sodium thiosulphate and pH adjustment of the,water to 6, 7 and 8, in order to assess if heavy metals and/or pH-dependent toxicants were present Potential toxicants, with concentrations high enough to intoxicate Daphnia magna, were Cu, ammonia and nitrite. Subsequent improvement of nitrification reduced the ammonia and nitrite concentrations as well as the toxicity. Furthermore, the improved production of algae and Daphnia at the Stensund Wastewater Aquaculture plant verified that the primary cause of toxicity was ammonia. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
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| 10. |
- Johansson, Lena, 1967-
(author)
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The use of LECA (Light Expanded Clay Aggregates) for the removal of phosphorus from wastewater
- 1997
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In: Water Science and Technology. - 0273-1223 .- 1996-9732. ; 35:5, s. 87-93
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Journal article (peer-reviewed)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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