Seasonal and treatment-process variations in invertebrates in drinking water treatment plants
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RESEARCH ARTICLE
Seasonal and treatment-process variations in invertebrates in drinking water treatment plants Zhiling Wu (✉)1, Xianchun Tang2, Hongbin Chen (✉)2 1 School of Environmental Science and Safety Engineering, Tianjin University of Technology, Tianjin 300384, China 2 School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
HIGHLIGHTS
GRAPHIC ABSTRACT
• Seasonal and treatment-process variations in invertebrates in a DWTP were analyzed. • The propagation and leakage of invertebrates in BAC filter were the most serious. • Invertebrates can survive and reproduce in chlorine disinfected clear water tanks. • Proportions of endogenous invertebrates increased along the treatment process.
ARTICLE INFO Article history:
Received 16 March 2020 Revised 30 May 2020 Accepted 7 July 2020 Available online 10 October 2020 Keywords: Invertebrates Drinking water Seasonal variations Treatment process
ABSTRACT Problems associated with excessive propagation and leakage of invertebrates in drinking water have received increasing attention in recent years. We performed a monthly survey of invertebrate abundance and taxa in the effluent of each treatment stage in a drinking water treatment plant between May 2015 and April 2016 and analyzed seasonal and treatment-process variations in invertebrates. The results showed that invertebrate abundances in raw water, effluent of the biological activated carbon (BAC) filter, and finished water significantly correlated with water temperature, whereas no correlation was observed between water temperature and invertebrate abundance in the effluents of the sedimentation tank and sand filter. The dominant taxa in the effluent of each treatment stage were rotifers, nematodes, and crustaceans. The sedimentation tank could efficiently remove invertebrates with an annual average removal rate of 92%. The propagation and leakage of invertebrates occurred in the sand and BAC filters but more seriously in the latter. The average reproduction rate in the BAC filter was 268.8% with rotifers as the taxon that leaked the most. Invertebrate survival and reproduction were also observed in the chlorine-disinfected clean water reservoir with an average reproduction rate of 41.9%. Owing to differences in chlorine resistance, the reproduction ability of the dominant taxa was in the order nematodes>crustaceans>rotifers. The proportion of endogenous invertebrates gradually increased along the treatment process. The average proportion of endogenous invertebrates in the finished water was higher than 79.0%. Our findings suggested that waterworks should pay more attention to endogenous invertebrate growth. © Higher Education Press 2020
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Introduction
Biological risks caused by invertebrates in water supply systems are attracting increasing public attention. Invertebrates in purification systems come mainly from exogenous input (e.g., raw water) or endogenous growth.
✉ Corresponding authors E-mail: [email protected] (Z.Wu); [email protected] (H.Chen)
Invertebrates are widely found in
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