Abstract
As a kind of high-organic-content contamination source, extracellular polymeric substances (EPS) secreted by cyanobacteria have become an important factor restricting the safety of supply water. In the dynamic batch mode water supply system, cyanobacterial EPS accelerated the decay rate of residual chlorine, resulting in a 21–26 times increase of the total viable bacteria count within 72 h. The water turbidity exceeded upper limit of the standards for drinking water quality within 4 h, with an increase of 306–332% within 72 h. The biological stability was reduced with BDOC and AOC increased by 41.4–43.8% and 331–396%, respectively. The main cause is that cyanobacterial EPS act as nutrients and metabolic energy for microorganisms, promoting their metabolic activity and secretion of extracellular organic components. This leads to the metabolic accumulation of tryptophan, fulvic acids and humic acids in the pipeline, thus further promoting the regeneration of bacteria. Compared with the influence of biofilm on pipe wall caused by long-term use of water supply network, the contribution of cyanobacterial EPS to the water contamination of pipe network is increased several times. Therefore, even in the presence of residual chlorine, the secondary contamination caused by cyanobacterial EPS in the water supply system could not be neglected.
Highlights
Published: 16 December 2021In order to improve the quality and safety of water supply, various water treatment processes in the water treatment plants are continuously upgraded and optimized, but the problem of secondary contamination of water quality in the water supply network is ignored [1,2,3]
The change of drinking water quality in the water supply network is caused by many factors, which are mainly affected by the content of residual pollutants in the treated water from the water purification plant and the breeding degree of microorganisms in the water supply pipeline [4,5]
Substances consumconsuming chlorine was less in the pipe network, and the residual chlorine decayed slowly ing chlorine was less in the pipe network, and the residual chlorine decayed slowly to 0.43 to 0.43 mg/L after 72 h (Figure 3)
Summary
In order to improve the quality and safety of water supply, various water treatment processes in the water treatment plants are continuously upgraded and optimized, but the problem of secondary contamination of water quality in the water supply network is ignored [1,2,3]. The change of drinking water quality in the water supply network is caused by many factors, which are mainly affected by the content of residual pollutants in the treated water from the water purification plant and the breeding degree of microorganisms in the water supply pipeline [4,5]. Even if the residual contamination source was trace or the content of BDOC exceeded 0.25 mg/L, it would pose a serious threat to the safety of water supply [13,14].
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