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| EPSRC Reference: |
GR/R68771/01 |
| Title: |
Tidal Flow Reed Bed Systems for High Strength Wastewater Treatment |
| Principal Investigator: |
Dr GJ Sun |
| Other Investigators: |
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| Researcher Co-investigator: |
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| Project Partner: |
| Agricultural Requisites & Mechanizations |
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| Department: |
Chemical Engineering |
| Organisation: |
Queen's University of Belfast |
| Scheme: |
Standard Research |
| Starts: |
17 April 2002 |
Ends: |
16 April 2004 |
Value (£): |
107,271
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| EPSRC Research Topic Classifications: |
| Energy Efficiency |
Water Engineering |
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| EPSRC Industrial Sector Classifications: |
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| Related Grants: |
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| Panel History: |
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Summary |
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As a 'green' technology with low energy consumption, reed bed systems have become popular in recent years for the treatment of a variety of effluents. However, when they are used to treat effluents with high BOD and NH4-N levels their efficacy is often limited by shortage of oxygen supply and poor water distribution. In order to overcome these problems, the concept of 'tidal flow' is introduced to create a new reed bed system where the bed matrix is alternately filled with wastewater and then drained. Such tidal flow operation enables the available matrix to be fully utilized, eliminating the problem of poor water distribution associated with conventional downflow reed beds. The rhythmical 'tides' generated in tidal flow systems repeatedly draw air from the atmosphere into the reed bed matrix, thus considerably improving the aeration of the matrix, enabling more pollutants to be aerobically decomposed. Preliminary studies on tidal flow systems have produced promising results. In the proposed project, trials will be carried out to determine the appropriate operating conditions for these systems. The mechanisms and kinetics for the reductions of some major pollutants will be investigated in both laboratoryand full-scale experiments. The relationships between operating parameters, pollutant loadings and pollutant removal rates will be studied, and simple models will be established for design purposes.
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| Final Report Summary |
As a 'green' technology with low energy consumption, reed bed systems have become popular in recent years for the treatment of a variety of effluents. However, when they are used to treat effluents with high BOD and NH4-N levels their efficacy is often limited by shortage of oxygen supply and poor water distribution. In order to overcome these problems, the concept of 'tidal flow' is introduced to create a new reed bed system where the bed matrix is alternately filled with wastewater and then drained. Such tidal flow operation enables the available matrix to be fully utilized, eliminating the problem of poor water distribution associated with conventional downflow reed beds. The rhythmical 'tides' generated in tidal flow systems repeatedly draw air from the atmosphere into the reed bed matrix, thus considerably improving the aeration of the matrix, enabling more pollutants to be aerobically decomposed. Preliminary studies on tidal flow systems have produced promising results. In the proposed project, trials will be carried out to determine the appropriate operating conditions for these systems. The mechanisms and kinetics for the reductions of some major pollutants will be investigated in both laboratoryand full-scale experiments. The relationships between operating parameters, pollutant loadings and pollutant removal rates will be studied, and simple models will be established for design purposes.
Summary of project outcomes (for non-specialist audiences)
Reed beds may provide a low-cost 'green' solution for the on-site treatment of some strong wastewaters, such as agricultural effluents and landfill leachates, if the problem of oxygen shortage and mal-water-distribution can be solved. This project investigates a novel 'tidal flow' system as a means to solve the problem. The term 'tidal flow' refers to an operation strategy that, repeatedly, allows reed bed matricies to be saturated with wastewater before being drained. When the matricies are saturated, maximum wastewater-biofilm contact is established. As the wastewater drains, air is drawn form the atmosphere into the matricies and the retreating wastewater acts as a passive pump to enhance the transfer of oxygen. The investigation firstly focused on optimising the operation of tidal flow. The results demonstrated that a shorter wastewater-biofilm contact time and longer aeration time benefits the removal of organic matter, a key pollutant, from the wastewater. Further experiments were then carried out in a lab- and field-scale tidal flow reed bed system. The relationships between the loading and removal of various pollutants were established. A simple mathematical model was developed to describe the clogging of bed matrices. Overall, the result demonstrated that tidal flow reed beds can be used as a primary stage in the treatment of strong wastewater because they provide greater pollutant removals than conventional reed beds; however, alternative operating and resting periods and the use of coarse substrate in the reed beds may be needed to prevent clogging and the blockage of wastewater flow.
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| Further Information: |
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| Organisation Website: |
http://www.qub.ac.uk |
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