###### Abstract  
Residual biomass from various industries represents an important source of valuable compounds, used as raw materials for the production of a wide range of new products and also in various treatment and valorization processes or/and sanitation services, thus responding to the principles of sustainable development, waste recovery, and a green and circular economy. The aim of this work is to make use of residual _Bacillus_ sp. biomass (resulting from a process of removing fatty acids from municipal wastewater) immobilized in alginate that, although it results in large quantities from biotechnological processes, is not reported to be valorized in dye biosorption processes, except in few specific applications. The biosorption potential of residual _Bacillus_ sp. biomass in the reactive Brilliant Red HE-3B textile dye removal from aqueous systems was studied in a fixed-bed column. The effects of various experimental operating parameters, such as bed depth (h), flow rate (\(F_{v}\)), were investigated, and the modeling of experimental data based on Thomas and Yoon-Nelson kinetic models was satisfactorily achieved. The obtained results reconfirm that the studied residual biomass can be also considered as a good biosorbent in dynamic operating system, and can be beneficially used in the treatment of wastewater containing small quantities of organic dyes. B _Bacillus_ sp. residual biomass; biosorption reactor design; dynamic biosorption; flow rate effect; Bred reactive anionic dye; Thomas and Yoon-Nelson models  
Received: 22 March 2021  
Accepted: 11 May 2021  
14 May 2021  
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**Crystal**  
**Crystal**
Attention in recent years has been focused on the use of various \"living\" techniques for treating contaminated environmental components, especially with organic pollutants, harnessing and developing known information from the self-purification processes of environmental components [13; 14; 15; 16; 17; 18]. Biological treatment is a flexible process that can be easily adapted to a multitude of wastewaters, characterized by different concentrations and compositions in polluting compounds, and has a few advantages related to the chemical treatment processes linked with the lack of need for separation of colloids and dispersed solid particles before treatment, lower energy consumption, and the possibility of using open tanks/reactors, thus resulting in lower costs and no need for waste/gas treatment. Chemical treatment related to biological treatment has the advantages of low sludge production, mineralization of non-biodegradable compounds, and smaller reactor volumes. The combination of physical-chemical and biological treatment processes for increasing large amounts of residuals/pollutants to be eliminated from final treated water/ wastewater are preferred. Adsorption continues to be among the often applied methods to retain certain categories of organic or inorganic pollutants, due mainly to advantages that are difficult to neglect: equipment for applications is easy to design and operate under advantageous conditions, the possibility of using a wide range of adsorbent materials (well-known commercial adsorbents, or \"low cost\" ones), and application-dependent in terms of the type of pollutant and the required process conditions. One alternative to adsorption onto commercial adsorbents (activated carbon, silica gel, exchangeable resins) is the use of residual biomass or different (bio)adsorbents capable of replacing the above mentioned well-known commercial adsorbents [8; 9; 10; 11; 12; 13; 14; 15]. In this context, a viable treatment technique with vast practical applications is biosorption, a separation method that is based on the formation of extracellular and intracellular bonds, interactions that are dependent on the nature of the chemical species, the structure of the biosorptive material, the microbial metabolism, and the transport process [14; 15; 17; 19].