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| Influence of types of plant husk carriers on biofilm characteristics and wastewater treatment |
| Received:May 28, 2020 |
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| KeyWord:plant husks;biofilm biomass;extracellular polymeric substances;docosahexaenoic acid;wastewater treatment |
| Author Name | Affiliation | E-mail | | HU Xiao-bing | College of Architectural Engineering, Anhui University of Technology, Ma'anshan 243002, China
Engineering Research Center of Water Purification and Utilization Technology Based on Biofilm Process, Ministry of Education, Ma'anshan 243032, China | | | WANG Kun | College of Architectural Engineering, Anhui University of Technology, Ma'anshan 243002, China | 18855571192@163.com | | SHEN Yi-jun | College of Architectural Engineering, Anhui University of Technology, Ma'anshan 243002, China
Engineering Research Center of Water Purification and Utilization Technology Based on Biofilm Process, Ministry of Education, Ma'anshan 243032, China | | | ZHANG Lin | College of Architectural Engineering, Anhui University of Technology, Ma'anshan 243002, China | | | YAO You-chang | College of Architectural Engineering, Anhui University of Technology, Ma'anshan 243002, China | | | LIN Rui | College of Architectural Engineering, Anhui University of Technology, Ma'anshan 243002, China | | | GU Xian-jing | College of Architectural Engineering, Anhui University of Technology, Ma'anshan 243002, China | |
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| Abstract: |
| This study aimed to improve the utilization of plant husks by investigating the potential of three waste plant husks from Arachis hypogaea Linn., Juglans regia, and Macadamia ternifolia F. Muell. The surface microstructures of these husks were characterized via scanning electron microscopy(SEM), and their chemical groups were analyzed via Fourier transform infrared spectroscopy(FTIR), to explore their feasibility as carriers to be used in sequencing batch biofilm reactors. The results showed that the surfaces of the husks were rough, porous, and rich in hydrophilic chemical groups such as OH and COOH. These characteristics are favorable for microbial attachment. The biofilm biomass of peanut husks quickly increased from 6.80 mg·cm-3 to 24.66 mg·cm-3 in the early test stage and then slowly decreased. Due to softening and decomposition, the biofilm biomass of peanut husks was continuously decreasing, until it reached the same level as the early test stage. Too many decaying metabolites accumulating in the biofilm gave rise to peanut husks producing the lowest extracellular polymeric substance(EPS)content(49.90 mg·g-1)and lower docosahexaenoic acid(DHA)content in the biofilm, with poor and high removal rate of chemical oxygen demand(COD)and NH4+-N(about 65%). Walnut and macadamia husks showed higher biofilm biomass, and the biomass increased rapidly from 7.98 mg·cm-3 to 26.75 mg·cm-3 and from 8.45 mg·cm-3 to 25.96 mg·cm-3, respectively, in the early test stage, followed by slower increases. Suspended in the reactor wastewater, walnut husks were subjected to strong hydraulic shear action, which enhanced the mass transfer effect of pollutants in the biofilm and promoted the microbial secretion of EPS, resulting in the highest EPS content of the tested husks(66.44 mg·g-1). The DHA contents of the two biofilms first increased and then stabilized, and the highest DHA content measured was 81.72 mg·g-1·h-1, indicating high biofilm activity. The two kinds of plant husks exhibited increasing removal rates of COD and NH4+-N, with the highest measured rate being around 90%. Walnut and macadamia husks were therefore suitable long-term carriers, as their structures were stable, their biofilm characteristics were optimal, and their pollutant removal effects were sufficient. |
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