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May 20, 2024

塩素の効能

npj Clean Water volume 4、記事番号: 48 (2021) この記事を引用する 6666 アクセス数 7 引用数 8 Altmetric Metrics の詳細 塩素溶液は生物学的物質の製造に広く使用されています。

npj クリーンウォーター 4 巻、記事番号: 48 (2021) この記事を引用

6666 アクセス

7 引用

8 オルトメトリック

メトリクスの詳細

塩素溶液は、生物学的に安全な飲料水の製造に広く使用されています。 使用時点 [POU] 飲料水処理システムの機能は、集中処理システムや配水ネットワークが実用的ではない場所で関心を集めています。 この研究では、POU 飲料水用途で使用される 3 つの塩素系消毒剤 (次亜塩素酸イオン [OCl-]、次亜塩素酸 [HOCl]、および電気化学的に活性化された溶液 [ECAS]) の抗菌および抗バイオフィルム活性を調査しました。 相対的な抗菌活性は、大腸菌を使用した殺菌懸濁液アッセイ (BS EN 1040 および BS EN 1276) 内で比較されました。 抗バイオフィルム活性は、疾病管理センター [CDC] バイオフィルム リアクター内で確立された固着性緑膿菌を利用して比較されました。 HOCl は、有機負荷 (ウシ血清アルブミン) の存在下、遊離塩素が 50 mg L-1 以上の浮遊性大腸菌に対して最大の抗菌活性を示しました。 しかし、ECAS は、遊離塩素 50 mg L-1 以上で、OCl および HOCl と比較して、緑膿菌バイオフィルムに対して有意に高い抗バイオフィルム活性を示しました。 この証拠に基づいて、HOCl が主な塩素種である消毒剤 (HOCl および ECAS) は、POU 飲料水用途に適切な代替塩素ベースの消毒剤となるでしょう。

人間の病気の主な原因は、生物学的に汚染された水の摂取によるものです1。 これは、平均して推定人口の 30% が、低所得国 (つまり、1 人当たりの国民総所得 [GNI] が 1,025 ドル未満) および後発開発途上国 (持続可能な開発に対する深刻な構造的障害に直面している 46 の低所得国) に特に関係します。基本的な衛生サービスを利用できる2. これは、生物学的に安全な水の生産と供給を確保するために主に集中型飲料水処理システムを利用しているアッパー中流国（1人当たりGNIが4,036ドルから12,475ドル）や高所得国（1人当たりGNI > 12,476ドル）とは対照的です3。 飲料水消毒の主な役割は、病原微生物を制御し、処理された水が生物学的に安全に飲めるようにすることです。 次亜塩素酸ナトリウム [NaOCl] の形の塩素は、低コストで効果的な抗菌特性があるため、最も一般的な消毒剤です4。 再分配ネットワーク内に残留塩素 (0.5 ～ 5 mg L-1) が存在すると、微生物の再増殖が制限され、配達時点で生物学的に安全な水を維持するのに役立ちます3。 糞便の存在を推測する大腸菌、全大腸菌群、腸球菌、ウェルシュ菌3,5などの指標微生物は、消毒処理プロセスの有効性を確保するために監視されます。 潜在的な病原性があるため、処理水中のこれらの指標微生物の推奨限度はゼロ CFU 100 mL-1 です。 残念なことに、塩素消毒剤を使用すると、トリハロメタン 8 やハロ酢酸 9 などの消毒副産物 [DBP]6,7 が生成されます。 このような副産物は、変異原性および発がん性の特性を示すことが知られており 10、したがって非常に望ましくない。

Point-of-use [POU] drinking water treatment systems do not require distribution networks and therefore negate the need to maintain residual chlorine levels. The World Health Organization recommends free chlorine concentrations of between 0.2 and 0.5 mg L−1 at point of delivery and use3. The use of conventional chlorine-based disinfectants, such as hypochlorite (OCl-), within POU water disinfection requires the storage and transportation of hazardous chemicals and can also cause the formation of harmful DBPs and the deterioration of taste and odour11. Ultraviolet and ozone are well established as disinfection technologies within both decentralised/POU12,13 and large scale drinking water treatment14,3.3.CO;2-1." href="/articles/s41545-021-00139-w#ref-CR15" id="ref-link-section-d367130989e520"15, but an added benefit of implementing electrochemcially activated solutions [ECAS] is it has capability to be used externally to water treatment systems as part of food production16,17 or in healthcare settings18,19. A limited number of studies have compared ECAS against commonly used chlorine agents for decentralised disinfection applications20,21. Although these preliminary studies were promising, neither study reported the pH of the ECAS studied or their effectiveness against biofilms./p>95%), and dissolved chlorine [Cl2] (<5%)25,26. Additional metastable antimicrobial species including; OH-, O3, H2O2 and O2- are also theorised to be generated although there lifetime and activity within active solutions is debated27,28. The antimicrobial properties of ECAS result from a combination of HOCl and the metastable species that give rise to the observed high ORP values. The mode of action of such solutions is then physical rupture of the inner and outer cell membranes19,29, leading to disruption and failure of microbial functionality, such as energy generation mechanisms23./p>5-log reduction) and there was no significant difference between the three disinfectants, whereby HOCl resulted in a complete log reduction, for OCl- a log reduction of 7.871 ± 0.74 log10 CFU mL−1 was achieved whilst ECAS achieved a 6.806 ± 1.09 log10 CFU mL−1 reduction. At 50 mg L−1 FC, OCl- did not achieve the required 5-log reduction (4.531 ± 0.15 log10 CFU mL−1), resulting in significantly lower antimicrobial activity compared to both HOCl and ECAS (p < 0.0001), whereby there was no significant difference between HOCl and ECAS treatment (p > 0.05). At the lowest FC concentration tested (25 mg L−1) ECAS was the only disinfectant to reduce the bacterial load ≥5 log10 CFU mL−1 (Fig. 2), resulting in a 6.077 ± 1.441 log10 CFU mL−1 log reduction. The log reductions obtained for OCl- and HOCl treatment were both significantly less than ECAS (p < 0.001), whereby HOCl resulted in a 3.207 ± 0.505 log10 CFU mL−1 log reduction, which was significantly greater than the 1.945 ± 0.222 log10 CFU mL−1 log reduction exhibited by OCl- (p = 0.0011). The 5-log reduction CT values for OCl-, HOCl and ECAS with a low organic load demonstrated that NaOCl exhibited the highest CT value (88.96 mg min L−1), followed by HOCl (34.78 mg min L−1) and then ECAS (20.94 mg min L−1)./p> 0.05). However, ECAS resulted in the greatest log reduction (1.606 ± 0.954 log10 CFU mL−1), followed by HOCl (0.978 ± 0.202 log10 CFU mL−1) and OCl- (0.025 ± 0.004 log10 CFU mL−1). The organic loading tested under dirty conditions does not represent concentrations expected within POU drinking water systems. However, results highlight the need to reduce organics present to ensure sufficient antimicrobial activity throughout disinfection stages of drinking water treatment./p> 0.05). In fact, there was no significant reduction in biofilm density between 0 (control) and 5 mg L−1 FC (p > 0.05) for any test disinfectant. Overall, the results demonstrate a dose-response of increasing antimicrobial efficacy with increasing FC concentrations. Interestingly, for ECAS the greatest increase in antimicrobial activity (p = 0.009) occurred at ≥25 mg L−1 FC, whereas the greatest increases for HOCl and OCl- were observed between 0 and 25 mg L−1 (p < 0.0001)./p>25 mg L−1 (i.e. 50, 100, 150 mg L−1). Interestingly, there was no significant difference in the antimicrobial activity exhibited by ECAS at an FC concentration of 25 mg L−1 in either the presence or absence of low organic loading (clean BSA conditions). This shows that low concentrations of organic matter do not unduly interfere with the mechanism of action for ECAS under these experimental conditions. ECAS exhibits very high ORP value (>+1100 mV), due to both reactive chlorine and oxygen species, which in turn drives rapid oxidation reactions. However, the presence of higher concentrations of organic matter will ultimately reduce the ORP through oxidation-reduction reactions50, contributing to a resultant reduction in antimicrobial activity of ECAS, as has been previously observed50,51. Interestingly, previous work by Robinson et al. in 201352 demonstrated that antimicrobial activity of ECAS could be maintained when stored for a 398 day period at 4 °C in the dark, despite showing no detectable FC after 277 days (e.g. < 0.01 mg L−1). This demonstrates the importance of the additional antimicrobial species, other than those that are chlorine derived, contributing to an increased antimicrobial activity. Thus, helping explain the greater antimicrobial activity of ECAS at a FC of 25 mg L−1 in the presence of clean BSA conditions when compared to equivalent HOCl and NaOCl solutions. Further increasing the organic loading of BSA (3.0 g L−1; dirty BSA conditions) within the bactericidal assay greatly reduced the antimicrobial activity of OCl- and ECAS at all FC concentrations tested. In comparison the antimicrobial activity of HOCl was not significantly reduced at FC concentrations >25 mg L−1. Therefore, it is clear that HOCl produced via the dissolution of NaDCC demonstrates a greater antimicrobial activity against planktonic bacteria under dirty BSA conditions. Chemically derived HOCl is more stable than electrochemically generated HOCl solutions, as they do not possess metastable antimicrobial species, that form at the anodic surface53. Chemically derived HOCl also degrades at a slower rate when exposed to sunlight (UV)54, in comparison to electrochemically generated HOCl which degrade at an increased rate55. This highlights the importance of selecting the most appropriate disinfectant for use in POU treatment systems. For example, in instances where filtration or removal of organic matter from bulk water is not standard practice or is difficult, HOCl would provide greater antimicrobial efficacy, compared to NaOCl or ECAS./p>3.3.CO;2-1./p>