Final Report Summary - WATERULTRAFILTRATION (Novel approaches for enhancing the treatment of drinking water by ultrafiltration and evaluating the mechanisms at nano-scale)
The objectives of the project were to evaluate novel approaches for enhancing the treatment of drinking water by an 'ultrafiltration' membrane process and investigate the underlying fundamental mechanisms of membrane performance. The project provided a Fellowship for Dr Wenzheng Yu to develop and extend his previous expertise in membrane technology at the Chinese Academy of Sciences, in collaboration with the host research group at Imperial College London (Professor Graham), which has complementary capabilities and activities in other water treatment unit processes. The research has been conducted through an extensive programme of laboratory bench-scale experiments using a specially developed experimental facility to assess the performance of the ultrafiltration technology with a range of novel pre-treatment methods.
At the beginning of the project, a novel experimental facility was assembled and commissioned in the Environmental Engineering laboratory at Imperial College London. Using this facility an extensive series of experiments were carried out involving a range of novel pre-treatment methods. The principal limitation affecting the cost-effectiveness of membrane processes is the phenomenon of pore blockage or 'fouling'. A key factor in fouling, and thus the performance of the membrane, is the formation of microbial extracellular polymeric substances (EPS) arising from the growth of bacteria; consequently, the selection of pre-treatment methods needs to be based on minimising biological effects. Thus, the focus of the experiments has mainly been on alternative oxidation/disinfection methods to inactivate bacteria, and physical separation arrangements to prevent coagulant material (with incorporated EPS) reaching the membrane surface. In order to establish the sustainability of each pre-treatment method, the experiments were operated for up to 2 months, during which the development of reversible and irreversible fouling could be fully monitored. In the first 12 months of the project Dr Yu has investigated the following:
1. Application of Fe(II)/manganate (K2MnO4), and ferrate (FeO4), as pre-treatment methods for controlling UF membrane fouling.
2. The role of coagulant sludge crystallization and sludge residence time in EPS increase and consequential membrane fouling.
3. Preventing flocs accumulation on, and within, membranes by incorporating the submerged ultrafiltration membrane within a granular media (sand) layer.
The subsequent 12 month phase of research investigated the following pre-treatment methods:
4. Effect of applying ozone in the submerged membrane tank and its optimal dose in controlling membrane fouling.
5. Application of ozone with a submerged MnO2-coated PVDF membrane for controlling membrane fouling, focusing on the catalytic effects of the MnO2 on ozone decomposition and OHº radical reactions.
6. Application of a magnetic ion exchange material (MIEX) and micro-sand before coagulation process on UF performance.
7. Combination of applying MIEX and ozone as a UF pre-treatment process.
8. Effect of Ultraviolet irradiation within the membrane tank on controlling membrane fouling with pre-coagulation.
In the original programme of work it was proposed to study ‘downstream processes’ in the later stages of the project, involving oxidation and carbon adsorption processes after the UF membrane. However, after completing the first year of study it was considered to be more beneficial and innovative to look in more detail at the benefits of oxidation processes in the pre-treatment stage (with and without catalytic coating of the membrane), together with more fundamental investigations of the membrane behaviour via short-period plate membrane tests.
In general, all of the novel techniques, with the exception of ferrate as a sole oxidant/coagulant, successfully enhanced membrane performance by reducing fouling effects, in comparison with conventional pre-treatment. In particular, the application of ozone with a submerged MnO2-coated PVDF membrane was especially beneficial by preventing any measurable degree of fouling over a period of 60 days. This is a very significant finding which requires further confirmatory work which is anticipated by the fellow and host scientist in the future. As well as the benefits to the UF membrane performance, the associated impact of the oxidation/degradation of organic micro-pollutants is also possible and, if proven, would make the technology an attractive alternative to conventional approaches for treating polluted surface waters.
Arising from the research has been a regular series of publications in leading scientific journals relating to each of the novel techniques applied. By the end of the project period, 11 scientific papers have been published, and 6 others are either in preparation or have been submitted. In addition, some of the principal results have been presented at various international conferences, namely in Japan (Sapporo, June 2014), Italy (Sicily, February 2015), the USA (Orlando, March 2015) and Germany (Aachen, September).
Dr Yu has interacted closely with Professor Graham throughout the Fellowship in terms of exchange of knowledge and pursuing the research objectives. Dr Yu's extensive knowledge of membrane technology enabled the experimental facility to be assembled (described above) which he was able to demonstrate to Professor Graham and Masters students in the host laboratory. This will enable Professor Graham to continue research on membrane filtration in the future. In turn, Professor Graham was able to familiarise Dr Yu in aspects of oxidation treatment by ozone, ferrate and manganate, and carbon adsorbents, which were new topics to Dr Yu. The synergistic combination of their respective expertise in Dr Yu's programme of research provided an excellent means of transferring knowledge to both researchers. Dr Yu has made visits to relevant, leading university groups in Germany (Berlin, Duisburg-Essen and Karlsruhe) and elsewhere in London (University College London), for the exchange of knowledge and information through seminars and technical discussions. Dr Yu has also been active in promoting his work through internal seminars at Imperial College London and by supervising Masters level student projects on topics related to the project objectives.
The final results of the project represent a comprehensive body of scientific research that has evaluated alternative novel approaches to preventing UF membrane fouling and thereby enhancing the performance of drinking water treatment processes employing UF membranes. The respective advantages of each approach are clearly described in the publications that are now available in the scientific literature. In particular the combination of ozone and MnO2-coated membrane offers the potential for long-term sustainable operation of the process without the need for periodic cleaning and maintenance of the membrane, plus the concurrent degradation of micro-pollutants (e.g. pesticides, pharmaceuticals) through the advanced oxidation present. This latter aspect has not been investigated in the project so far, but will be the subject of further work beyond the fellowship period.
In terms of wider impact of the results obtained during Dr Yu's fellowship, it is expected that these will be of direct value to designers and operators of full-scale UF membrane systems in Europe and internationally, and will lead to more cost-effective and reliable water treatment plants in practice. Dr Yu has also helped to develop new knowledge and expertise in membrane systems within the host organisation (Imperial College London), which will enable further research to continue. As an example, the host research group has received UK Government support, beginning in January 2016, to conduct further studies relating to sustainable membrane systems for drinking water treatment.
In conclusion, the fellowship has been highly successful in terms of two-way transfer of expertise between Dr Yu and Professor Graham's research areas, in undertaking a highly productive programme of research which has benefitted from the synergy of their expertise, and which will form the basis for on-going collaboration between their groups in the future.
At the beginning of the project, a novel experimental facility was assembled and commissioned in the Environmental Engineering laboratory at Imperial College London. Using this facility an extensive series of experiments were carried out involving a range of novel pre-treatment methods. The principal limitation affecting the cost-effectiveness of membrane processes is the phenomenon of pore blockage or 'fouling'. A key factor in fouling, and thus the performance of the membrane, is the formation of microbial extracellular polymeric substances (EPS) arising from the growth of bacteria; consequently, the selection of pre-treatment methods needs to be based on minimising biological effects. Thus, the focus of the experiments has mainly been on alternative oxidation/disinfection methods to inactivate bacteria, and physical separation arrangements to prevent coagulant material (with incorporated EPS) reaching the membrane surface. In order to establish the sustainability of each pre-treatment method, the experiments were operated for up to 2 months, during which the development of reversible and irreversible fouling could be fully monitored. In the first 12 months of the project Dr Yu has investigated the following:
1. Application of Fe(II)/manganate (K2MnO4), and ferrate (FeO4), as pre-treatment methods for controlling UF membrane fouling.
2. The role of coagulant sludge crystallization and sludge residence time in EPS increase and consequential membrane fouling.
3. Preventing flocs accumulation on, and within, membranes by incorporating the submerged ultrafiltration membrane within a granular media (sand) layer.
The subsequent 12 month phase of research investigated the following pre-treatment methods:
4. Effect of applying ozone in the submerged membrane tank and its optimal dose in controlling membrane fouling.
5. Application of ozone with a submerged MnO2-coated PVDF membrane for controlling membrane fouling, focusing on the catalytic effects of the MnO2 on ozone decomposition and OHº radical reactions.
6. Application of a magnetic ion exchange material (MIEX) and micro-sand before coagulation process on UF performance.
7. Combination of applying MIEX and ozone as a UF pre-treatment process.
8. Effect of Ultraviolet irradiation within the membrane tank on controlling membrane fouling with pre-coagulation.
In the original programme of work it was proposed to study ‘downstream processes’ in the later stages of the project, involving oxidation and carbon adsorption processes after the UF membrane. However, after completing the first year of study it was considered to be more beneficial and innovative to look in more detail at the benefits of oxidation processes in the pre-treatment stage (with and without catalytic coating of the membrane), together with more fundamental investigations of the membrane behaviour via short-period plate membrane tests.
In general, all of the novel techniques, with the exception of ferrate as a sole oxidant/coagulant, successfully enhanced membrane performance by reducing fouling effects, in comparison with conventional pre-treatment. In particular, the application of ozone with a submerged MnO2-coated PVDF membrane was especially beneficial by preventing any measurable degree of fouling over a period of 60 days. This is a very significant finding which requires further confirmatory work which is anticipated by the fellow and host scientist in the future. As well as the benefits to the UF membrane performance, the associated impact of the oxidation/degradation of organic micro-pollutants is also possible and, if proven, would make the technology an attractive alternative to conventional approaches for treating polluted surface waters.
Arising from the research has been a regular series of publications in leading scientific journals relating to each of the novel techniques applied. By the end of the project period, 11 scientific papers have been published, and 6 others are either in preparation or have been submitted. In addition, some of the principal results have been presented at various international conferences, namely in Japan (Sapporo, June 2014), Italy (Sicily, February 2015), the USA (Orlando, March 2015) and Germany (Aachen, September).
Dr Yu has interacted closely with Professor Graham throughout the Fellowship in terms of exchange of knowledge and pursuing the research objectives. Dr Yu's extensive knowledge of membrane technology enabled the experimental facility to be assembled (described above) which he was able to demonstrate to Professor Graham and Masters students in the host laboratory. This will enable Professor Graham to continue research on membrane filtration in the future. In turn, Professor Graham was able to familiarise Dr Yu in aspects of oxidation treatment by ozone, ferrate and manganate, and carbon adsorbents, which were new topics to Dr Yu. The synergistic combination of their respective expertise in Dr Yu's programme of research provided an excellent means of transferring knowledge to both researchers. Dr Yu has made visits to relevant, leading university groups in Germany (Berlin, Duisburg-Essen and Karlsruhe) and elsewhere in London (University College London), for the exchange of knowledge and information through seminars and technical discussions. Dr Yu has also been active in promoting his work through internal seminars at Imperial College London and by supervising Masters level student projects on topics related to the project objectives.
The final results of the project represent a comprehensive body of scientific research that has evaluated alternative novel approaches to preventing UF membrane fouling and thereby enhancing the performance of drinking water treatment processes employing UF membranes. The respective advantages of each approach are clearly described in the publications that are now available in the scientific literature. In particular the combination of ozone and MnO2-coated membrane offers the potential for long-term sustainable operation of the process without the need for periodic cleaning and maintenance of the membrane, plus the concurrent degradation of micro-pollutants (e.g. pesticides, pharmaceuticals) through the advanced oxidation present. This latter aspect has not been investigated in the project so far, but will be the subject of further work beyond the fellowship period.
In terms of wider impact of the results obtained during Dr Yu's fellowship, it is expected that these will be of direct value to designers and operators of full-scale UF membrane systems in Europe and internationally, and will lead to more cost-effective and reliable water treatment plants in practice. Dr Yu has also helped to develop new knowledge and expertise in membrane systems within the host organisation (Imperial College London), which will enable further research to continue. As an example, the host research group has received UK Government support, beginning in January 2016, to conduct further studies relating to sustainable membrane systems for drinking water treatment.
In conclusion, the fellowship has been highly successful in terms of two-way transfer of expertise between Dr Yu and Professor Graham's research areas, in undertaking a highly productive programme of research which has benefitted from the synergy of their expertise, and which will form the basis for on-going collaboration between their groups in the future.