Evaluation of Chitosans as Coagulants—Flocculants to Improve Sand Filtration for Drinking Water Treatment
The World Health Organization (WHO) reports that two billion people worldwide lack access to safely managed water sources, including 1.2 billion who already have access to improved water sources. In many countries, household point-of-use (POU) water-treatment options are used to remove or deactivate...
Main Authors: | , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
MDPI AG
2023-01-01
|
Series: | International Journal of Molecular Sciences |
Subjects: | |
Online Access: | https://www.mdpi.com/1422-0067/24/2/1295 |
_version_ | 1797441450679468032 |
---|---|
author | Eleanor B. Holmes Hemali H. Oza Emily S. Bailey Mark D. Sobsey |
author_facet | Eleanor B. Holmes Hemali H. Oza Emily S. Bailey Mark D. Sobsey |
author_sort | Eleanor B. Holmes |
collection | DOAJ |
description | The World Health Organization (WHO) reports that two billion people worldwide lack access to safely managed water sources, including 1.2 billion who already have access to improved water sources. In many countries, household point-of-use (POU) water-treatment options are used to remove or deactivate microorganisms in water, but not all POU technologies meet WHO performance requirements to achieve safe drinking water. To improve the effectiveness of POU technologies, the use of multiple treatment barriers should be used as a way to increase overall treatment performance. The focus of this research is to evaluate multiple barrier treatment using chitosan, an organic coagulant–flocculant, to improve microbial and turbidity reductions in combination with sand filtration. Bench-scale intermittently operated sand filters with 16 cm layers of sands of two different grain sizes representing slow and rapid sand filters were dosed daily over 57 days with microbially spiked surface water volumes corresponding to household use. <i>E. coli</i> bacteria and MS2 coliphage virus reductions were quantified biweekly (N = 17) using culture methods. Bacteria and virus removals were significantly improved over sand filtration without chitosan pretreatment (Wilcoxon Rank-Sum, <i>p</i> < 0.05). When water was pretreated at an optimal chitosan dose of 10 mg/L followed by sand filtration, log<sub>10</sub> reductions in bacteria and viruses met the two-star WHO performance level of effectiveness. Microbial and turbidity reductions generally improved over the filter operating period but showed no trends with filtration rates. |
first_indexed | 2024-03-09T12:23:14Z |
format | Article |
id | doaj.art-e5bbad2421224e019b5d8bd0945b8be7 |
institution | Directory Open Access Journal |
issn | 1661-6596 1422-0067 |
language | English |
last_indexed | 2024-03-09T12:23:14Z |
publishDate | 2023-01-01 |
publisher | MDPI AG |
record_format | Article |
series | International Journal of Molecular Sciences |
spelling | doaj.art-e5bbad2421224e019b5d8bd0945b8be72023-11-30T22:38:14ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672023-01-01242129510.3390/ijms24021295Evaluation of Chitosans as Coagulants—Flocculants to Improve Sand Filtration for Drinking Water TreatmentEleanor B. Holmes0Hemali H. Oza1Emily S. Bailey2Mark D. Sobsey3Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USADepartment of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USADepartment of Public Health, College of Pharmacy & Health Sciences, Campbell University, Buies Creek, NC 27506, USADepartment of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USAThe World Health Organization (WHO) reports that two billion people worldwide lack access to safely managed water sources, including 1.2 billion who already have access to improved water sources. In many countries, household point-of-use (POU) water-treatment options are used to remove or deactivate microorganisms in water, but not all POU technologies meet WHO performance requirements to achieve safe drinking water. To improve the effectiveness of POU technologies, the use of multiple treatment barriers should be used as a way to increase overall treatment performance. The focus of this research is to evaluate multiple barrier treatment using chitosan, an organic coagulant–flocculant, to improve microbial and turbidity reductions in combination with sand filtration. Bench-scale intermittently operated sand filters with 16 cm layers of sands of two different grain sizes representing slow and rapid sand filters were dosed daily over 57 days with microbially spiked surface water volumes corresponding to household use. <i>E. coli</i> bacteria and MS2 coliphage virus reductions were quantified biweekly (N = 17) using culture methods. Bacteria and virus removals were significantly improved over sand filtration without chitosan pretreatment (Wilcoxon Rank-Sum, <i>p</i> < 0.05). When water was pretreated at an optimal chitosan dose of 10 mg/L followed by sand filtration, log<sub>10</sub> reductions in bacteria and viruses met the two-star WHO performance level of effectiveness. Microbial and turbidity reductions generally improved over the filter operating period but showed no trends with filtration rates.https://www.mdpi.com/1422-0067/24/2/1295HWTSPOUchitosancoagulationsand filtrationbacterial reduction |
spellingShingle | Eleanor B. Holmes Hemali H. Oza Emily S. Bailey Mark D. Sobsey Evaluation of Chitosans as Coagulants—Flocculants to Improve Sand Filtration for Drinking Water Treatment International Journal of Molecular Sciences HWTS POU chitosan coagulation sand filtration bacterial reduction |
title | Evaluation of Chitosans as Coagulants—Flocculants to Improve Sand Filtration for Drinking Water Treatment |
title_full | Evaluation of Chitosans as Coagulants—Flocculants to Improve Sand Filtration for Drinking Water Treatment |
title_fullStr | Evaluation of Chitosans as Coagulants—Flocculants to Improve Sand Filtration for Drinking Water Treatment |
title_full_unstemmed | Evaluation of Chitosans as Coagulants—Flocculants to Improve Sand Filtration for Drinking Water Treatment |
title_short | Evaluation of Chitosans as Coagulants—Flocculants to Improve Sand Filtration for Drinking Water Treatment |
title_sort | evaluation of chitosans as coagulants flocculants to improve sand filtration for drinking water treatment |
topic | HWTS POU chitosan coagulation sand filtration bacterial reduction |
url | https://www.mdpi.com/1422-0067/24/2/1295 |
work_keys_str_mv | AT eleanorbholmes evaluationofchitosansascoagulantsflocculantstoimprovesandfiltrationfordrinkingwatertreatment AT hemalihoza evaluationofchitosansascoagulantsflocculantstoimprovesandfiltrationfordrinkingwatertreatment AT emilysbailey evaluationofchitosansascoagulantsflocculantstoimprovesandfiltrationfordrinkingwatertreatment AT markdsobsey evaluationofchitosansascoagulantsflocculantstoimprovesandfiltrationfordrinkingwatertreatment |