Reed Biochar Addition to Composite Filler Enhances Nitrogen Removal from BDBR Systems in Eutrophic Rivers Channel

Yajun Chang,Xiaojing Liu,Jie Liu,Linhe Sun,Jian Cui,Shiqun Han,Dongrui Yao,Qiang Tang

doi:10.3390/w13182501

Abstract

With the rapid development of urbanization in China, the eutrophication or black stink of urban rivers has become a critical environmental problem. As a research hotspot in wastewater purification, biofilm technology has shortcomings, such as insufficient carbon sources for denitrification. This study used a Biofilm Denitrification Batch Reactor (BDBR) system constructed using reed biochar as the carbon source required in denitrification, significantly accelerating the biofilm formation. To determine the suitable amount of biochar for water purification from the urban eutrophic rivers by the BDBR system, 0%, 5%, 10%, and 15% reed biochar was added to the viscose fiber combined packing. The combined packing reactor involved in this study had a high removal efficiency of the eutrophication channel COD throughout the experiment. However, adding 5% and 10% biochar in the combined filler effectively increased the number of nitrifying and denitrifying bacteria on the biofilm, improved the dominant bacteria diversity and microbial activity, and enhanced denitrification efficiency in the BDBR system. It provides new ideas and methods for developing and applying in situ denitrification technology for urban polluted rivers.

Highlights

The eutrophication or black stink of urban rivers has become a crucial environmental problem due to the rapid development of urbanization in China [1,2,3]
We found that 26 days were enough for biofilm formation in a Biofilm Denitrification Batch Reactor (BDBR) system under the operating parameters, significantly accelerating the biofilm formation process and achieving the rapid startup and stable operation of the BDBR system by adding the reed biochar into the combined filler
The results discovered that the biofilm biomass increased with the biochar content in the combined packing, adding 5% and 10% biochar, not 15% in the combined filler, can effectively increase nitrifying and denitrifying bacteria in the BDBR system and improve the dominant bacteria diversity and microbial activity

Summary

Introduction

The eutrophication or black stink of urban rivers has become a crucial environmental problem due to the rapid development of urbanization in China [1,2,3]. The remediation technologies mainly include physical, chemical, and biological methods [6,7,8]. Of these methods, biological methods are mostly encouraged and recommended because they are more economical and environmental-friendly than physical or chemical methods for urban rivers remediation [6,9]. Biological methods based on purification of the aquatic plants and microbial degradation have some drawbacks in practical applications. The purification performance of aquatic plants is low in winter, and nutrients would re-enter the waterbody after the plants withered [10]; the added external microorganisms might not reproduce rapidly to become a dominant flora due to their poor adaptability to a new

Methods

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Discussion

Conclusion