Exploring biofilm-forming bacteria for integration into BioCircuit wastewater treatment

Abstract

This study aimed to investigate the presence of biofilm-forming bacteria within high sulfide sludge obtained from a rubber wastewater treatment plant and assess their suitability for application within a BioCircuit System (BCS) as a symbiotic community for treating nutrient-rich wastewater. The sludge samples were collected and subjected to microbial culture techniques, wherein pure cultures were isolated based on morphological characteristics observed under a light microscope, followed by assessment of motility using swarm agar. Subsequent identification was conducted utilizing the 16S rRNA gene sequencing method, and the isolated bacteria were introduced into the BCS. A 12 mL microbial fuel cell test was conducted to evaluate their power generation capabilities. The wastewater treatment process involved inoculating the BCS with 20% crude rubber wastewater sludge, and the system was initiated at a flow rate of 0.5 L/min for a month. Upon achieving an open-circuit voltage exceeding 50 mV, the BCS was operated at incremental flow rates (0.5-1.0, 1.0-1.5, and 1.5-2.0 mL/ min) over a period of 6 months. Real-time monitoring of voltage, flow rate, and energy consumption was facilitated through an internet-of-things online program. Weekly sampling and analysis of influent and effluent, focusing on chemical oxygen demand (COD), sulfate, and sulfide concentrations, were conducted. Additionally, the BioCircuit voltage was recorded every 5 minutes. The results revealed the presence of six group-forming shaped bacteria identified as Bacillus tequilensis, Bacillus sp., Ferribacterium limneticum, Bacillus weihenstephanesis, and Mycobacterium sp., respectively. The optimal flow rate of 1.5 L/min yielded a maximum voltage of 1.2 V and demonstrated high wastewater treatment efficiency. Economically, the BCS operation exhibited a power consumption rate of 0.257 kWhr/m3 of treated wastewater, leading to an 88.90% reduction in carbon footprint compared to aerated lagoon treatment, equivalent to 50.94 kg CO2/m3 of treated wastewater or 183,384 kg CO2/yr for a 10 m3 plant. These findings underscore the potential of the BCS in conjunction with group-forming shaped bacteria communities for various industrial wastewater treatment applications.