Abstract
Biofouling is a major concern for numerous reverse osmosis membrane systems. UV pretreatment of the feed stream showed promising results but is still not an established technology as it does not maintain a residual effect. By conducting accelerated biofouling experiments in this study, it was investigated whether low fluence UV in situ treatment of the feed using UVC light-emitting diodes (UVC-LEDs) has a lasting effect on the biofilm. The application of UVC-LEDs for biofouling control is a novel hybrid technology that has not been investigated, yet. It could be shown that a low fluence of 2 mJ∙cm−2 delays biofilm formation by more than 15% in lab-scale experiments. In addition, biofilms at the same feed channel pressure drop exhibited a more than 40% reduced hydraulic resistance. The delay is probably linked to the inactivation of cells in the feed stream, modified adsorption properties or an induced cell cycle arrest. The altered hydraulic resistance might be caused by a change in the microbial community, as well as reduced adenosine triphosphate levels per cells, possibly impacting quorum sensing and extracellular polymeric substances production. Due to the observed biofilm attributes, low fluence UV-LED in situ treatment of the feed stream seems to be a promising technology for biofouling control.
Highlights
Many regions worldwide suffer from water scarcity [1,2]
The applied fluence of 2 mJ·cm−2 is 10 or more times lower compared to the fluences applied for UV disinfection as biofouling control previously reported in the literature [58,59,60,61]
Findings of this study reveal that UV pretreatment using UVC-LEDs in the immediate vicinity of reverse osmosis (RO) membrane surfaces is capable of delaying biofouling already at low fluences
Summary
Many regions worldwide suffer from water scarcity [1,2]. Especially if no conventional water resources are available, water reuse [3], brackish groundwater or seawater desalination are viable approaches to provide alternative water supplies [4,5,6]. The adhesion phase is influenced by the microorganism species, their population density and physiological responses, as well as the concentration and composition of dissolved organic matter in the feed water [18,19]. Stress conditions, such as DNA damage, are known to lead to prophage induction to biofilms, which can further lead to biofilm dispersal or disruption [118,143]. ATP is seen as an indicator for active biomass in general [78] [15] (p. 26)
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