Advanced treatment of sugarcane vinasse via hybrid photocatalytic sequencing batch biofilm reactor (HP-SBBR): A combined physicochemical and biological approach

Abstract

A large volume of undesired chemical liquid generated by ethanol distillation is known as sugarcane vinasse. It is an acidic, dark brown distillery spent wash rich in organic compounds that can cause toxicity to living organisms, soil and water acidification, and groundwater contamination. This study introduces a hybrid chemical and biological treatment approach combining photocatalysis and a sequencing batch biofilm reactor (HP-SBBR). Chemical coagulation with alum was applied as a pretreatment due to its compatibility and low cost. Subsequently, the bio-photocatalytic reaction in HP-SBBR with zinc oxide (ZnO) photocatalyst achieved substantial degradation, evidenced by 93.1 % COD reduction and 99.7 % decolourisation at a low loading rate of 0.024 kg·COD/m³·day. Kinetic studies and UV–vis spectra confirmed that the combination of light and microorganisms effectively reduce COD of sugarcane vinasse and improved the biodegradation index. Microbial analysis using 16S rDNA revealed predominant bacterial genera, including Pseudomonas sp. (28 %), Bacillus sp. (8 %), Tissierella sp. (7 %), and Azoarcus sp. (6 %). To assess toxicity, a phytotoxicity test using mung bean (Vigna radiata) showed an 85 % reduction in toxicity based on germination rate, indicating that treated vinasse is more suitable for reuse in agriculture. Although the integrated pre-coagulation and HP-SBBR system demonstrated strong technical feasibility and treatment performance, further studies on operating costs and technical constraints are necessary to evaluate its applicability and impact in full-scale vinasse management.