Work

Investigation of hydrodynamic and mass transfer characteristics in a draft tube spouted bed bioreactor (DTSBBR) for simultaneous COD and nitrate removal

Year: 2026

Type: article

Abstract: Because interactions among microbial growth kinetics, biofilm formation, hydrodynamic conditions, and mass transfer constraints frequently limit process stability and scale-up, the simultaneous removal of chemical oxygen demand (COD) and nitrate from wastewater remains a significant challenge in biological treatment systems. The hydrodynamic and mass transfer characteristics of a Draft Tube Spouted Bed Bioreactor (DTSBBR) were examined for the simultaneous removal of chemical oxygen demand (COD) and nitrate from synthetic wastewater under different operating parameters. In a biofilm-assisted reactor, performance was assessed at dilution rates (0.6, 0.9, and 1.2/h) and granular activated carbon (GAC) loads (10, 20, and 30 g). The biofilm thickness, substrate diffusion, external mass transfer coefficient, Reynolds number (Re), Schmidt number (Sc), and Sherwood number (Sh) were precisely studied and evaluated under the influence of reactor hydrodynamic studies. The COD elimination confirmed higher mass transfer capability compared to the nitrate values because of diffusion-limited denitrification kinetics, with Sherwood numbers ranging from 4.60 to 7.10 and mass transfer coefficients between 0.66*10 –6 and 1.04*10 –6 m/s. The empirical correlations S h = 0.86 Re 0.52 Sc 0.33 for COD and S h = 0.76 Re 0.50 Sc 0.33 for nitrate were obtained by diffusion-controlled substrate transport and substantial hydrodynamic dependence. The Monod kinetic experiments showed µmax values of 0.25/h for COD and 0.23/h for nitrate, with a constant Ks of 25 mg/L for COD and 14 mg/L for nitrate. The obtained results confirmed that DTSBBR provided consistent simultaneous organic and nitrogen removal, enhanced biofilm activity, and efficient substrate transport, demonstrating its applicability for advanced biological wastewater treatment applications.

Source: Scientific Reports

DOI: 10.1038/s41598-026-67006-x

Authors: Kirankumar Rathod, Keshava Joshi, Lokeshwari Navalgund, Nabisab Mujawar Mubarak, Subhash Chandra

Institutions: Visvesvaraya Technological University, Imam Mohammad ibn Saud Islamic University, Chitkara University, Saveetha University, GITAM University

Language: English

Topic: Wastewater Treatment and Nitrogen Removal

Subfield: Pollution

Field: Environmental Science

Domain: Physical Sciences

SDGs: Clean water and sanitation, Responsible consumption and production

Open Access status: gold

Estimated APC paid: $2,690