Production of Bioflocculants Prepared from Wastewater Supernatant of Anaerobic Co-Digestion of Corn Straw and Molasses Wastewater Treatment

Abstract

a Novel bioflocculants (BS-MBF) were prepared using the wastewater supernatant from anaerobic co-digestion of corn straw and molasses wastewater as a nutrient resource. Acetic acid and ethanol were the dominant fermentation products during the anaerobic digestion process and were estimated to be 50.5% and 30.0%, respectively, after 150 d of operation. Equal volumes of bioflocculant producing bacteria F2 (Rhizobium radiobacter) and F6 (Bacillus sphaericus) were mixed to form F + , which was inoculated to wastewater supernatant at different times. A maximum flocculation activity of 91.3% was achieved, and 2.32 g/L of purified bioflocculant was extracted when a compound medium from 110-d wastewater supernatant was used. The removal efficiencies of heavy metals from simulated electroplating wastewater were tested by using these prepared bioflocculants. The optimal conditions for heavy metal removal to BS-MBF were found to be at 374 mg/L at an initial pH of 6.0 and a contact time of 40 min. The adsorption capacities for Cu 2+ and Zn 2+ reached more than 90%, while for Cr 6+ it reached approximately 30%. Overall, the study showed for the first time that wastewater supernatant from anaerobic co-digestion of corn straw and molasses wastewater can be used for producing bioflocculants, which can be effectively used to remove heavy metals from electroplating wastewater.

Microbial Flocculants as an Alternative to Synthetic Polymers for Wastewater Treatment: A Review

“…More recently, it was demonstrated that Rhizobium radiobacter and Bacillus sphaericus were effective for the elimination of Zn 2+ , Cu 2+ , Cr 6+ , and Ni 2+ from simulated electroplating wastewater. A bioflocculant dose of 374 mg/L (acting at pH 6 for 40 min) allowed 90% removal for both Zn 2+ and Cu 2+ , 65% for Ni 2+ , and only 30% for Cr 6+ [22]. In addition, Yao et al (2013) [77] reported significant removal of Fe 3+ and Pb 2+ from wastewater using B. mucilaginosus bioflocculant.…”

“…Similarly, wastewater and sludge, which are abundant raw materials containing enough carbon, nitrogen, phosphorus, and micronutrients, could sustain microbial growth for bioflocculant production. According to Zhao et al (2017), Rhizobium radiobacter and Bacillus sphaericus were able to synthesize flocculating materials while growing in wastewater supernatant of anaerobic co-digestion (corn straw and molasses wastewater) [22]. Methanol wastewater was used as a growth medium to produce bioflocculant useful for arsenite removal [34].…”

“…In addition to organic pollutant removal, microbial bioflocculants were shown to be able to remove metals from an ion solution and real wastewater, as represented in Table 5 [17,22,34,44,[74][75][76][77][78][79]. Among the works using real wastewater, a bacterial culture broth of two strains (xn11 + xn7) was used to flocculate electroplating wastewater (Cr (VI) initial concentration of 280 mg/L).…”

An Environmental and Economic Analysis of Flocculation Technology Applied to a Corn-Based Ethanol Plant

“…In most cases, chemical flocculants can negatively impact the environment and health. Bio-based flocculants, a type of biodegradable macromolecular flocculants, can advantageously replace chemical flocculants by being biodegradable and less harmful to the environment [25,26].…”

“…Bio-based flocculants can either be produced by microorganisms such as bacteria and fungi, or extracted from natural resources, such as trees [28]. Zhao et al [25] studied the production and optimization of bio-based flocculants by using wastewater supernatant from corn straw and molasses wastewater from anaerobic digestion (AD) to remove heavy metals. They produced relevant results and concluded that such wastewater could be used to produce bio-based flocculants for effectively removing heavy metals from electroplating wastewater.…”