Membrane fouling – the deposition of organic and inorganic matter on the membrane surface – is a major technical obstacle affecting membrane-based water treatment processes. Fouling results in decreased membrane permeance, selectivity, and shorter useful life due to irreversible fouling. Despite significant efforts to mitigate fouling through, e.g., low-fouling membrane coatings, fouling is inevitable due to the high convective fluxes driving foulants to the membrane surface. Consequently, physical and chemical cleaning strategies, known collectively as cleaning-in-place (CiP) protocols, are indispensable to ensure the sustainable use of membrane technology in water treatment.

Most CiP formulations entail proprietary mixtures of buffered surfactants and chelants that dissolve organic foulants and disperse colloidal metal-organic complexes. Application of CiP solutions often follows manufacturer-specified cleaning conditions, including cross-flow velocity, duration and frequency of cleaning cycles. Such operating conditions, however, are not optimised for specific feed water and foulant chemistries. Moreover, the important influence of CiP solution temperature is often neglected. Solution temperature plays a key role in membrane cleaning, as the interactions responsible for foulant adhesion to the membrane become weaker with rising temperature¹. However, the role of temperature in CiP has not been studied systematically. Incomplete knowledge about the influence of operating conditions has hindered development of efficient CiP protocols.

This PhD project will formulate tailored CiP strategies for membranes in Scottish Water (SW) treatment plants. The overarching goal is twofold: i) to identify the CiP temperature resulting in optimal membrane performance; ii) to identify CiP formulations (or mixtures thereof) suitable for application at ambient feed water temperatures (i.e., in cold water). Considering that CiP at SW membrane plants is often carried out at ambient water temperature (T_amb = 10 °C or lower), we anticipate significant improvements in cleaning efficiency if CiP were carried out at slightly higher temperatures. The cost of CiP operations at above-ambient temperatures will be weighed against the improvement in process performance (stemming from mitigated fouling) by a technoeconomic analysis. Lastly, we will perform a life cycle assessment of CiP protocols to identify CiP candidates meeting SW’s sustainability goals.

Training and mentoring

This project offers a unique training opportunity in the fundamentals of colloid and interface science, as well as membrane-based processes for water quality control. The student will be mentored by a supervisory team with complementary expertise, who will provide training in a wide variety of experimental techniques. In addition, the student will acquire industrial experience through a placement at a Scottish Water membrane plant.

References

(1) BinAhmed, S.; Hozalski, R. M.; Romero-Vargas Castrillón, S. Feed Temperature Effects on Organic Fouling of Reverse Osmosis Membranes: Competition of Interfacial and Transport Properties. ACS ES&T Eng. 2021, 1 (3), 591–602. https://doi.org/10.1021/acsestengg.0c00258.

(2) Porcelli, N.; Judd, S. Chemical Cleaning of Potable Water Membranes: The Cost Benefit of Optimisation. Water Res. 2010, 44 (5), 1389–1398. https://doi.org/10.1016/j.watres.2009.11.020.

Please note that applications will be reviewed on a continuing basis until the position is filled. Thus, the advert might close for applications before the closing date.