|SONG, PENG - China Agriculture University|
|ZHOU, BO - China Agriculture University|
|ZHOU, HONGXU - China Agricultural University|
|ZHAO, ZHIRUI - China Agricultural University|
|LIU, YAOZE - China Agricultural University|
|LI, YUNKAI - China Agricultural University|
Submitted to: BIOFOULING
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2019
Publication Date: 5/30/2019
Citation: Song, P., Zhou, B., Feng, G.G., Brooks, J.P., Zhou, H., Zhao, Z., Liu, Y., Li, Y. 2019. The influence of chlorination timing and concentration on microbial communities in labyrinth channels: implications for biofilm removal. BIOFOULING. 35:401-415. https://doi.org/10.1080/08927014.2019.1600191.
Interpretive Summary: We examined the controlling mechanism and effects on the attached biofilm and microbial communities within labyrinth path of drip irrigation under different residual chlorine concentration using reclaimed water. The following main conclusions can be drawn: (1) The formation of attached biofilms in the labyrinthine flow path at meso-scale was regulated by changing microbial communities using chlorination. The content of biofilm PLFAs (fungi PLFA undetectable) was reduced by 12.52% - 53.75% after chlorination. The Proteobacteria (containing the inhibition of viscous EPS secretion) and Firmicutes (the cell wall thickness) became dominant bacteria, which was not conducive to the development of biofilm, also reduced the number of microorganisms and significantly reduced the diversity. (2) There was a significant negative correlation between the EPS content and the relative abundance of Acinetobacter and Thermomonas (R2=0.81, p<0.01; R2=0.45, p<0.05). As the relative abundance of the two were increased by 15.78%~110.90%, 6.51%~40.56%, the EPS content was decreased by 7.90%~40.38%, as a result, the content of SD in the flow path was reduced. (3) Chlorination could attribute to increasing the microbial activity by 0.54% - 19.22%, the biofilm resistance to chlorine was increased, which resulted in a potential risk of reducing the effect of chlorine sterilization. The chlorination at low concentration for long duration consumed more chlorine, which ensure more chlorine through the biofilms and achieve better regulation. (4) C0.80T3 chlorination significantly increased the emitter Dra by 26.93% - 39.90%, which reduced clogging of the labyrinthine flow path. It can be used to effectively regulate clogging for the labyrinthine flow paths.
Technical Abstract: Chemical chlorination is an effective method for controlling the formation of biofilms in enclosed pipelines. The relevant research has focused on urban water supply or precise micro-scale long straight pipelines, chlorination controlling mechanism for the formation of attached biofilms at the meso-scale complex pipelines was rarely investigated. For this purpose, we examined the controlling mechanism and effects on the attached biofilm and microbial communities within labyrinth path of drip irrigation under different residual chlorine concentration using reclaimed water. The result showed that chlorination could significantly reduce the formation of attached biofilms in the labyrinth path, the total amount of microbial phospholipid fatty acid (PLFAs) was reduced by 13 - 54%, the secretion of sticky extracellular polymeric substances (EPS) was decreased by 8- 40%; meanwhile, the species of microbes were reduced, the ace and chao index was decreased by 3-21% and 2% - 39%, respectively. The microbial diversity index was reduced and the shannon index declined by 2% - 21%. However, chlorination increased the microbial activity by 0.5% to 19.2%. The relative abundance of chlorotolerant bacteria (Acinetobacter and Thermonnus) increased, which could result in a potential risk of resistance to chlorine, thus, inhibited the effect of chlorination to some extent. Considering all those factors, keeping low concentration at 0.80 mg/L for 3 hours was effective for controlling formation of attached biofilms in labyrinth path. This method can effectively prevent emitter from clogging, it reduced the total amount of attached biofilm within labyrinth path by 43% while increased the discharge ratio variation (Dra) by 40%. The research results can provide reference for the analysis of the formation mechanism and control the attached biofilm in the reclaimed water pipe network.