Composition and Abundance Distribution of Filamentous Bacteria During the Variable- and Low-Temperature Operation Periods of Wastewater Treatment Plants

Activated sludge microorganisms in sewage treatment plants are crucial for controlling water pollution and protecting public health and the ecological environment. Activated sludge must have biodegradation, easy sedimentation, and separation functions. Filamentous bacteria play an essential role in floc formation and structure. However, low temperature, low load and low dissolved oxygen (DO) will destroy the balance between beneficial structural action and harmful overgrowth. In this study, the high-throughput sequencing (HTS) dataset of 16s rRNA gene sequence V3–V4 amplicons from 30 activated sludge samples from the Chuanhu Sewage Treatment Plant in Changchun was analyzed to investigate the abundance distribution of filamentous bacteria and further determine the main operating parameters and environmental factors. The experimental results showed that the filamentous bacterial community accounted for a large part of the entire microbial community, with the total filamentous bacterial percentage in each sample ranging from 7.32% to 56.81%, with large fluctuations in abundance and consistent with the SVI value. Although most of them were in flocs, they occasionally caused sedimentation problems when the water temperature was low. With 14 species of filamentous bacteria detected, the population structure of filamentous bacteria in the thermophilic, variable-temperature and low-temperature periods was universal and specific. The groups with a detection frequency of 100%, high abundance, and significant fluctuations in distribution were Microthrix parvicella and Nostocoida limicola I. The Pearson correlation analysis showed that the total abundance of filamentous bacteria and the fluctuation distribution of dominant filamentous bacteria abundance were significantly correlated with water temperature, sludge load, sludge age, and mixed liquid suspended solids (MLSS).