Performances and mechanisms for improving the river water quality by a simple integration of mussels and immobilized microorganisms.

The complexity of ecological remediation technology restricts its long-term application in engineering practice. In this study, a simple top-down mussels-bacteria (TDMB) integrated system used for river water quality improvement was constructed, and the long-term operation performances accompanied by the corresponding mechanisms were investigated. The results showed that during 161 days of operation, the average removal efficiency achieved was 75.45% for COD, 79.41% for ammonia nitrogen and 70% for total nitrogen (TN), while the contribution proportions of mussels and immobilized microorganisms in the TN removal were 28.07% and 69.77%, respectively. High-throughput sequencing revealed that the dominant microorganisms for immobilization were norank_SC-I-84 (10.52%), norank_PHOS-HE36 (9.58%), norank_Anaerolineaceae (3.04%), Nitrospira (2.64%), norank_Gemmatimonadaceae (2.36%) and norank_Pirellulaceae (2.113%), all of which were involved in nitrogen removal. This study provided a promising strategy and gained insight into the corresponding mechanisms for the remediation of polluted rivers.