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Sousi M, Salinas-Rodriguez SG, Liu G, Dusseldorp J, Kemperman AJB, Schippers JC, Van der Meer WGJ, Kennedy MD. Comparing the bacterial growth potential of ultra-low nutrient drinking water assessed by growth tests based on flow cytometric intact cell count versus adenosine triphosphate. Water Res 2021; 203:117506. [PMID: 34371231 DOI: 10.1016/j.watres.2021.117506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Revised: 06/24/2021] [Accepted: 07/27/2021] [Indexed: 06/13/2023]
Abstract
The bacterial growth potential (BGP) of drinking water is widely assessed either by flow cytometric intact cell count (BGPICC) or adenosine triphosphate (BGPATP) based methods. Combining BGPICC and BGPATP measurements has been previously applied for various types of drinking water having high to low growth potential. However, this has not been applied for water with ultra-low nutrient content, such as remineralised RO permeate. To conduct a sound comparison, conventionally treated drinking water was included in this study, which was also used as an inoculum source. BGPICC, BGPATP, intact cell-yield (YICC), and ATP-yield (YATP) were determined for conventionally treated drinking water (Tap-water) and remineralised RO permeate (RO-water). In addition, both BGPICC and BGPATP methods were used to identify the growth-limiting nutrient in each water type. The results showed that the BGPICC ratio between Tap-water/RO-water was ∼7.5, whereas the BGPATP ratio was only ∼4.5. Moreover, the YICC ratio between Tap-water/RO-water was ∼2 (9.8 ± 0.6 × 106 vs. 4.6 ± 0.8 × 106 cells/µg-C), whereas the YATP ratio was ∼1 (0.39 ± 0.12 vs. 0.42 ± 0.06 ng ATP/µg-C), resulting in a consistently higher ATP per cell in RO-water than that of Tap-water. Both BGPICC and BGPATP methods revealed that carbon was the growth-limiting nutrient in the two types of water. However, with the addition of extra carbon, phosphate limitation was detected only with the BGPICC method, whereas BGPATP was not affected, suggesting that a combination of carbon and phosphate is essential for biomass synthesis, whereas carbon is probably utilised for cellular activities other than cell synthesis when phosphate is limited. It was estimated that the intact cell-yield growing on phosphate would be 0.70 ± 0.05 × 109 cells/µg PO4-P.
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Affiliation(s)
- Mohaned Sousi
- Department of Water Supply, IHE Delft Institute for Water Education, Sanitation and Environmental Engineering, Westvest 7, Delft 2611 AX, the Netherlands; Faculty of Science and Technology, University of Twente, Drienerlolaan 5, Enschede 7522 NB, the Netherlands
| | - Sergio G Salinas-Rodriguez
- Department of Water Supply, IHE Delft Institute for Water Education, Sanitation and Environmental Engineering, Westvest 7, Delft 2611 AX, the Netherlands
| | - Gang Liu
- Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences, Key Laboratory of Drinking Water Science and Technology, Beijing 100085, PR China; Department of Water Management, Faculty of Civil Engineering and Geoscience, Delft University of Technology, Mekelweg 2, Delft 2628 CD, the Netherlands.
| | - Jos Dusseldorp
- Oasen Drinkwater, Nieuwe Gouwe O.Z. 3, Gouda 2801 SB, the Netherlands
| | - Antoine J B Kemperman
- Faculty of Science and Technology, University of Twente, Drienerlolaan 5, Enschede 7522 NB, the Netherlands
| | - Jan C Schippers
- Department of Water Supply, IHE Delft Institute for Water Education, Sanitation and Environmental Engineering, Westvest 7, Delft 2611 AX, the Netherlands
| | - Walter G J Van der Meer
- Faculty of Science and Technology, University of Twente, Drienerlolaan 5, Enschede 7522 NB, the Netherlands; Oasen Drinkwater, Nieuwe Gouwe O.Z. 3, Gouda 2801 SB, the Netherlands
| | - Maria D Kennedy
- Department of Water Supply, IHE Delft Institute for Water Education, Sanitation and Environmental Engineering, Westvest 7, Delft 2611 AX, the Netherlands; Department of Water Management, Faculty of Civil Engineering and Geoscience, Delft University of Technology, Mekelweg 2, Delft 2628 CD, the Netherlands
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Sousi M, Liu G, Salinas-Rodriguez SG, Chen L, Dusseldorp J, Wessels P, Schippers JC, Kennedy MD, van der Meer W. Multi-parametric assessment of biological stability of drinking water produced from groundwater: Reverse osmosis vs. conventional treatment. Water Res 2020; 186:116317. [PMID: 32841931 DOI: 10.1016/j.watres.2020.116317] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 08/16/2020] [Accepted: 08/17/2020] [Indexed: 06/11/2023]
Abstract
Although water produced by reverse osmosis (RO) filtration has low bacterial growth potential (BGP), post-treatment of RO permeate, which is necessary prior to distribution and human consumption, needs to be examined because of the potential re-introduction of nutrients/contaminants. In this study, drinking water produced from anaerobic groundwater by RO and post-treatment (ion exchange, calcite contactors, and aeration) was compared with that produced by conventional treatment comprising (dry) sand filtration, pellet softening, rapid sand filtration, activated carbon filtration, and UV disinfection. The multi-parametric assessment of biological stability included bacterial quantification, nutrient concentration and composition as well as bacterial community composition and diversity. Results showed that RO permeate remineralised in the laboratory has an extremely low BGP (50 ± 12 × 103 ICC/mL), which increased to 130 ± 10 × 103 ICC/mL after site post-treatment. Despite the negative impact of post-treatment, the BGP of the finished RO-treated water was >75% lower than that of conventionally treated water. Organic carbon limited bacterial growth in both RO-treated and conventionally treated waters. The increased BGP in RO-treated water was caused by the re-introduction of nutrients during post-treatment. Similarly, OTUs introduced during post-treatment, assigned to the phyla of Proteobacteria and Bacteroidetes (75-85%), were not present in the source groundwater. Conversely, conventionally treated water shared some OTUs with the source groundwater. It is clear that RO-based treatment achieved an extremely low BGP, which can be further improved by optimising post-treatment, such as using high purity calcite. The multi-parametric approach adopted in this study can offer insights into growth characteristics including limiting nutrients (why) and dominating genera growing (who), which is essential to manage microbiological water quality in water treatment and distribution systems.
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Affiliation(s)
- Mohaned Sousi
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Westvest 7, AX Delft 2611, the Netherlands; Faculty of Science and Technology, University of Twente, Drienerlolaan 5, NB Enschede 7522, the Netherlands
| | - Gang Liu
- Key Laboratory of Drinking Water Science and Technology, Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; Department of Water Management, Faculty of Civil Engineering and Geoscience, Delft University of Technology, Mekelweg 2, CD Delft 2628, the Netherlands.
| | - Sergio G Salinas-Rodriguez
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Westvest 7, AX Delft 2611, the Netherlands
| | - Lihua Chen
- Department of Water Management, Faculty of Civil Engineering and Geoscience, Delft University of Technology, Mekelweg 2, CD Delft 2628, the Netherlands
| | - Jos Dusseldorp
- Oasen Drinkwater, Nieuwe Gouwe O.Z. 3, SB Gouda 2801, the Netherlands
| | - Peter Wessels
- Oasen Drinkwater, Nieuwe Gouwe O.Z. 3, SB Gouda 2801, the Netherlands
| | - Jan C Schippers
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Westvest 7, AX Delft 2611, the Netherlands
| | - Maria D Kennedy
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Westvest 7, AX Delft 2611, the Netherlands; Department of Water Management, Faculty of Civil Engineering and Geoscience, Delft University of Technology, Mekelweg 2, CD Delft 2628, the Netherlands
| | - Walter van der Meer
- Faculty of Science and Technology, University of Twente, Drienerlolaan 5, NB Enschede 7522, the Netherlands; Oasen Drinkwater, Nieuwe Gouwe O.Z. 3, SB Gouda 2801, the Netherlands
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Sousi M, Salinas-Rodriguez SG, Liu G, Schippers JC, Kennedy MD, van der Meer W. Measuring Bacterial Growth Potential of Ultra-Low Nutrient Drinking Water Produced by Reverse Osmosis: Effect of Sample Pre-treatment and Bacterial Inoculum. Front Microbiol 2020; 11:791. [PMID: 32411118 PMCID: PMC7201026 DOI: 10.3389/fmicb.2020.00791] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 04/02/2020] [Indexed: 12/20/2022] Open
Abstract
Measuring bacterial growth potential (BGP) involves sample pre-treatment and inoculation, both of which may introduce contaminants in ultra-low nutrient water (e.g., remineralized RO permeate). Pasteurization pre-treatment may lead to denaturing of nutrients, and membrane filtration may leach/remove nutrients into/from water samples. Inoculating remineralized RO permeate samples with natural bacteria from conventional drinking water leads to undesired nutrient addition, which could be avoided by using the remineralized RO permeate itself as inoculum. Therefore, this study examined the effect of pasteurization and membrane filtration on the BGP of remineralized RO permeate. In addition, the possibility of using bacteria from remineralized RO permeate as inoculum was investigated by evaluating their ability to utilize organic carbon that is readily available (acetate, glucose) or complex (laminarin, gelatin, and natural dissolved organic carbon), as compared with bacteria from conventional drinking water. The results showed that membrane filtration pre-treatment increased (140-320%) the BGP of remineralized RO permeate despite the extensive soaking and flushing of filters (>350 h), whereas no effect was observed on the BGP of conventional drinking water owing to its high nutrient content. Pasteurization pre-treatment had insignificant effects on the BGP of both water types. Remineralized RO permeate bacteria showed limitations in utilizing complex organic carbon compared with bacteria from conventional drinking water. In conclusion, the BGP bioassay for ultra-low nutrient water (e.g., remineralized RO permeate) should consider pasteurization pre-treatment. However, an inoculum comprising bacteria from remineralized RO permeate is not recommended as the bacterial consortium was shown to be limited in terms of the compounds they could utilize for growth.
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Affiliation(s)
- Mohaned Sousi
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Delft, Netherlands
- Faculty of Science and Technology, University of Twente, Enschede, Netherlands
| | - Sergio G. Salinas-Rodriguez
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Delft, Netherlands
| | - Gang Liu
- Key Laboratory of Drinking Water Science and Technology, Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- Department of Water Management, Faculty of Civil Engineering and Geoscience, Delft University of Technology, Delft, Netherlands
| | - Jan C. Schippers
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Delft, Netherlands
| | - Maria D. Kennedy
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Delft, Netherlands
- Department of Water Management, Faculty of Civil Engineering and Geoscience, Delft University of Technology, Delft, Netherlands
| | - Walter van der Meer
- Faculty of Science and Technology, University of Twente, Enschede, Netherlands
- Oasen Drinkwater, Gouda, Netherlands
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Sousi M, Liu G, Salinas-Rodriguez SG, Knezev A, Blankert B, Schippers JC, van der Meer W, Kennedy MD. Further developing the bacterial growth potential method for ultra-pure drinking water produced by remineralization of reverse osmosis permeate. Water Res 2018; 145:687-696. [PMID: 30212807 DOI: 10.1016/j.watres.2018.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 08/15/2018] [Accepted: 09/02/2018] [Indexed: 06/08/2023]
Abstract
Ensuring the biological stability of drinking water is essential for modern drinking water supply. To understand and manage the biological stability, it is critical that the bacterial growth in drinking water can be measured. Nowadays, advance treatment technologies, such as reverse osmosis (RO), are increasingly applied in drinking water purification where the produced water is characterized by low levels of nutrients and cell counts. The challenge is, therefore, how to measure the low bacterial growth potential (BGP) of such ultra-pure water using the available methods which were originally developed for conventionally treated drinking water. In this study, we proposed a protocol to assess BGP of ultra-pure drinking water produced by RO and post-treatment (including remineralization). Natural bacterial consortium from conventional drinking water was added to all water samples during this study to ensure the presence of a wide range of bacterial strains. The method development included developing an ultra-pure blank with high reproducibility to lower the detection limit of the BGP method (50 ± 20 × 103 intact cells/mL) compared with conventional blanks such as bottled spring water, deep groundwater treated by aeration and slow sand filtrate of surface water supply. The ultra-low blank consists of RO permeate after adjusting its pH and essential mineral content under controlled laboratory conditions to ensure carbon limitation. Regarding the test protocol, inoculum concentrations of >10 × 103 intact cells/mL may have a significant contribution to the measured low levels of BGP. Pasteurization of water samples before measuring BGP is necessary to ensure reliable bacterial growth curves. The optimized method was used to assess BGP of ultra-pure drinking water produced by RO membranes and post-treatment (including remineralization), where the BGP has decreased more than 6-fold to a level of 90 ± 20 × 103 intact cells/mL compared with conventionally treated water (630 ± 70 × 103 intact cells/mL).
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Affiliation(s)
- Mohaned Sousi
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Westvest 7, 2611 AX, Delft, the Netherlands; Faculty of Science and Technology, University of Twente, Drienerlolaan 5, 7522 NB, Enschede, the Netherlands
| | - Gang Liu
- Oasen Drinkwater, Nieuwe Gouwe O.Z. 3, 2801 SB, Gouda, the Netherlands; Department of Water Management, Faculty of Civil Engineering and Geoscience, Delft University of Technology, Stevinweg 1, 2628 CN, Delft, the Netherlands.
| | - Sergio G Salinas-Rodriguez
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Westvest 7, 2611 AX, Delft, the Netherlands
| | - Aleksandra Knezev
- Het Waterlaboratorium, J.W. Lucasweg 2, 2031 BE, Haarlem, the Netherlands
| | - Bastiaan Blankert
- Oasen Drinkwater, Nieuwe Gouwe O.Z. 3, 2801 SB, Gouda, the Netherlands
| | - Jan C Schippers
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Westvest 7, 2611 AX, Delft, the Netherlands
| | - Walter van der Meer
- Faculty of Science and Technology, University of Twente, Drienerlolaan 5, 7522 NB, Enschede, the Netherlands; Oasen Drinkwater, Nieuwe Gouwe O.Z. 3, 2801 SB, Gouda, the Netherlands
| | - Maria D Kennedy
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, Westvest 7, 2611 AX, Delft, the Netherlands; Department of Water Management, Faculty of Civil Engineering and Geoscience, Delft University of Technology, Stevinweg 1, 2628 CN, Delft, the Netherlands
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