Permeation Increases Biofilm Development in Nanofiltration Membranes Operated with Varying Feed Water Phosphorous Concentrations

Unveiling the spatiotemporal dynamics of membrane fouling: A focused review on dynamic fouling characterization techniques and future perspectives

Membrane technology has emerged as a crucial method for obtaining clean water from unconventional sources in the face of water scarcity. It finds wide applications in wastewater treatment, advanced treatment, and desalination of seawater and brackish water. However, membrane fouling poses a huge challenge that limits the development of membrane-based water treatment technologies. Characterizing the dynamics of membrane fouling is crucial for understanding its development, mechanisms, and effective mitigation. Instrumental techniques that enable in situ or real-time characterization of the dynamics of membrane fouling provide insights into the temporal and spatial evolution of fouling, which play a crucial role in understanding the fouling mechanism and the formulation of membrane control strategies. This review consolidates existing knowledge about the principal advanced instrumental analysis technologies employed to characterize the dynamics of membrane fouling, in terms of membrane structure, morphology, and intermolecular forces. Working principles, applications, and limitations of each technique are discussed, enabling researchers to select appropriate methods for their specific studies. Furthermore, prospects for the future development of dynamic characterization techniques for membrane fouling are discussed, underscoring the need for continued research and innovation in this field to overcome the challenges posed by membrane fouling.

Characterization of young biofilm morphology, disinfection byproduct formation potential and toxicity of renewed water supply pipelines by phosphorus release from corroded pipes

The deterioration of drinking water quality due to corrosion of the water supply network has become inevitable and regular renewal of pipes has become a common means of doing so. Severely corroded pipes release certain nutrients (e.g., elemental phosphorus), however, little has been reported on the effect of old pipes on the young biofilm of new pipe sections and on ensuring water safety in the early stages of the water supply. The aim of our study was to model the effect of key phosphorus nutrients released from corroded old pipes on the morphological characteristics of young biofilms in new pipe sections, mediated disinfection byproducts (DBPs) production and their combined toxicity. Based on the experimental results, phosphorus showed significant differences in the morphological characteristics, spatial structure of extracellular polymers (EPS), functional abundance, disinfection byproduct formation potential (DBPsFP) and toxicity of young biofilms. Under residual chlorine (1.0 ± 0.2 mg/L) incubation, the functional abundance of young biofilm metabolism was dominant, particularly amino acid metabolism and carbohydrate metabolism. There is a dynamic balance between the trophic and shedding effects of phosphorus, where concentration changes affect young biofilm morphology and DBPFP. Relatively moderate phosphorus concentrations resulted in the highest density of PN/PS organic precursors in EPS and a clear advantage of DBPFP; relatively high phosphorus conditions had limited promotion of young biofilm, while membrane structure shedding was more pronounced, increasing young biofilm-mediated DBPs production. Nitrogen-containing disinfection byproducts (N-DBPs) in young biofilms had a clear toxicity advantage, with HANs and HNMs being key to controlling cytotoxicity and genotoxicity, respectively.

High Flux Nanofiltration Membranes with Double-Walled Carbon Nanotube (DWCNT) as the Interlayer

Nanofiltration (NF) membranes with a high permeability and rejection are of great interest in desalination, separation and purification. However, how to improve the permeation and separation performance still poses a great challenge in the preparation of NF membranes. Herein, the novel composite NF membrane was prepared through the interfacial polymerization of M-phenylenediamine (MPD) and trimesoyl chloride (TMC) on a double-walled carbon nanotube (DWCNT) interlayer supported by PES substrate. The DWCNT interlayer had a great impact on the polyamide layer formation. With the increase of the DWCNT dosage, the XPS results revealed an increase in the number of carboxyl groups, which decreased the crosslinking degree of the polyamide layer. Additionally, the AFM results showed that the surface roughness and specific surface area increased gradually. The water flux of the prepared membrane increased from 25.4 L/(m²·h) and 26.6 L/(m²·h) to 109 L/(m²·h) and 104.3 L/(m²·h) with 2000 ppm Na₂SO₄ and NaCl solution, respectively, under 0.5 MPa. Meanwhile, the rejection of Na₂SO₄ and NaCl decreased from 99.88% and 99.38% to 96.48% and 60.47%. The proposed method provides a novel insight into the rational design of the multifunctional interlayer, which shows great potential in the preparation of high-performance membranes.