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Chemical Cleaning of Ultrafiltration Membrane Fouled by Humic Substances: Comparison between Hydrogen Peroxide and Sodium Hypochlorite.

ABSTRACT: Chemical cleaning is indispensable for the sustainable operation of ultrafiltration (UF) system in water and wastewater treatment. Sodium hypochlorite (NaClO) is an established cleaning agent for membranes subject to organic and microbial fouling, but concerns have been raised about the generation of toxic halogenated by-products during NaClO cleaning. Hydrogen peroxide (H₂O₂) is a potential "green" cleaning agent that can avoid the formation of halogenated by-products. In this work, cleaning efficacy of H₂O₂ and NaClO for UF membrane fouled by humic substances (HS) was evaluated under a wide pH range, and change of HS's properties due to reaction with cleaning agents was examined. The cleaning efficacy of H₂O₂ was lower than that of NaClO at pH 3-9, but it increased to a level (91.4%) comparable with that of NaClO at pH 11. The extents of changes in properties and fouling potential of HS due to reacting with cleaning agents were consistent with their cleaning efficacy. H₂O₂ treatment at pH 11 significantly increased negative charge of HS molecules, decomposed high-MW molecules, and reduced its fouling potential. Therefore, considering treatment/disposal of cleaning waste and cleaning efficacy, H₂O₂ cleaning under strong alkaline condition can be a good choice for HS-fouled membrane.

SUBMITTER: Li K

PROVIDER: S-EPMC6678075 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Chemical Cleaning of Ultrafiltration Membrane Fouled by Humic Substances: Comparison between Hydrogen Peroxide and Sodium Hypochlorite.

Li Kai K Li Shu S Huang Tinglin T Dong Chongzhe C Li Jiawei J Zhao Bo B Zhang Shujia S

International journal of environmental research and public health 20190718 14

Chemical cleaning is indispensable for the sustainable operation of ultrafiltration (UF) system in water and wastewater treatment. Sodium hypochlorite (NaClO) is an established cleaning agent for membranes subject to organic and microbial fouling, but concerns have been raised about the generation of toxic halogenated by-products during NaClO cleaning. Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) is a potential "green" cleaning agent that can avoid the formation of halogenated by-products. In ...[more]

PMID: 31323814

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Project description:BackgroundBurkholderia cepacia complex bacteria are opportunistic pathogens, which can cause severe respiratory tract infections in patients with cystic fibrosis (CF). As treatment of infected CF patients is problematic, multiple preventive measures are taken to reduce the infection risk. Besides a stringent segregation policy to prevent patient-to-patient transmission, clinicians also advise patients to clean and disinfect their respiratory equipment on a regular basis. However, problems regarding the efficacy of several disinfection procedures for the removal and/or killing of B. cepacia complex bacteria have been reported. In order to unravel the molecular mechanisms involved in the resistance of biofilm-grown Burkholderia cenocepacia cells against high concentrations of reactive oxygen species (ROS), the present study focussed on the transcriptional response in sessile B. cenocepacia J2315 cells following exposure to high levels of H2O2 or NaOCl.ResultsThe exposure to H2O2 and NaOCl resulted in an upregulation of the transcription of 315 (4.4%) and 386 (5.4%) genes, respectively. Transcription of 185 (2.6%) and 331 (4.6%) genes was decreased in response to the respective treatments. Many of the upregulated genes in the NaOCl- and H2O2-treated biofilms are involved in oxidative stress as well as general stress response, emphasizing the importance of the efficient neutralization and scavenging of ROS. In addition, multiple upregulated genes encode proteins that are necessary to repair ROS-induced cellular damage. Unexpectedly, a prolonged treatment with H2O2 also resulted in an increased transcription of multiple phage-related genes. A closer inspection of hybridisation signals obtained with probes targeting intergenic regions led to the identification of a putative 6S RNA.ConclusionOur results reveal that the transcription of a large fraction of B. cenocepacia J2315 genes is altered upon exposure of sessile cells to ROS. These observations have highlighted that B. cenocepacia may alter several pathways in response to exposure to ROS and they have led to the identification of many genes not previously implicated in the stress response of this pathogen.

Dataset Information

Chemical Cleaning of Ultrafiltration Membrane Fouled by Humic Substances: Comparison between Hydrogen Peroxide and Sodium Hypochlorite.

Publications

Chemical Cleaning of Ultrafiltration Membrane Fouled by Humic Substances: Comparison between Hydrogen Peroxide and Sodium Hypochlorite.

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