Free Bioreactors Research Articles

Enhanced simultaneous removal of sulfamethoxazole and zinc (II) in the biochar-immobilized bioreactor: Performance, microbial structures and gene functions

Biochar-immobilized functional bacteria Bacillus SDB4 was applied for sulfamethoxazole (SMX) and zinc (Zn2+) simultaneous removal in the bioreactor. Under the optimal operating conditions of HRT of 10 h, pH of 7.0, SMX concentration of 10 mg L−1 and Zn2+ concentration of 50 mg L−1, the removal efficiencies of SMX and Zn2+ by the immobilized reactor (IR) were 97.42% and 96.14%, respectively, 20.39% and 30.15% higher than those by free bioreactor (FR). SEM-EDS and FTIR results revealed that the functional groups and light metals on the carrier promoted the biosorption and biotransformation of SMX and Zn2+ in IR. Moreover, the improvement of SMX and Zn2+ removal might be related to the abundance enhancement of functional bacteria and genes. Bacillus SDB4 responsible for SMX and Zn2+ removal was the main strain in IR and FR. Biochar increased the relative abundance of Bacillus from 32.12% in FR to 38.73% in IR and improved the abundances of functional genes (such as carbohydrate metabolism, replication and repair and membrane transport) by 1.82%–11.04%. The correlations among the physicochemical properties, microbial communities, functional genes and SMX-Zn2+ co-contaminant removal proposed new insights into the mechanisms of biochar enhanced microbial removal of antibiotics and heavy metals in biochar-immobilized bioreactors.

Phenol biodegradation in hybrid hollow-fiber membrane bioreactors

Hollow-fiber membrane bioreactors were developed with granular activated carbon (GAC) for the biodegradation of phenol using Pseudomonas putida. Hollow fibers showed similar structure with/without GAC incorporated; while GAC hollow fiber had a stronger phenol adsorption capacity. In batch biotransformation experiments, complete depletion of 1000 mg phenol l−1 (at which concentration free cells cannot grow) was accomplished in the reactor within 18 h in the hybrid bioreactor, comparing with 23 h in the GAC free bioreactor. Desorption and bioregeneration of the hollow-fiber membrane were believed to be the key for the enhancement of bioreactor performance. At continuous running, the GAC bioreactor showed its superiority over the GAC free bioreactor during start-up and elevated loading phase. More than 90% of the phenol was transformed in the GAC bioreactor when the phenol loading was <24 mg h−1. The better bioreactor performance may be due to the enhanced mass transportation and adsorption capacity with the incorporation of GAC.

Hybrid-Hollow-Fiber Membrane Bioreactor for Cometabolic Transformation of 4-Chlorophenol in the Presence of Phenol

Hybrid-hollow-fiber membrane bioreactors were developed for the enhanced cometabolic biotransformation of phenol and 4-chlorophenol (4-cp) by Pseudomonas putida ATCC49451. Bioreactor performance was investigated, compared, and analyzed under batch and continuous operating modes. The spinning solutions contained polysulfone (PS), N -methyl-2-pyrrolidone, and various weight ratios of granular activated carbon (GAC) (GAC: PS of 0, 1:4, and 1:2). The bioreactor fabricated with 1:2 GAC hybrid-hollow-fiber membranes demonstrated the best performance for the removal of phenol and 4-cp, both under batch and continuous operations. Under batch operation, 500 mg L−1 phenol and 4-cp were completely removed within 23 h in the bioreactor, compared with 26 and 30 h for the 1:4 GAC and GAC free bioreactors. Sorption, biotransformation, desorption, and bioregeneration were identified as the four steps for substrate removal during batch operation. The 1:2 GAC hollow-fiber membrane bioreactor also manifested superiority ove...