Research On Construction And Enhanced Wastewater Treatment Efficiency Of Mycelial Pellet As A Biomass Carrier

Bioaugmentation was one of popular directions in wastewater treatmentresearches and played an important role in the field of improving water quality andsystem operational stability. The technology enhanced the removal efficiency totarget pollutants relied on biological carrier to maintain the concentration andactivity of functional bacteria. Therefore, the development of biological carrierswith compatibility and without changing the treatment process was necessary tomaximize the effectiveness of bioaugmentation technology. Biomass materials suchas straw, bamboo and others had been the research focus as biological carriersrecently. Based on this, the study was to develop mycelial pellet as a new biomasscarrier in bioaugmentation, and mycelial pellet as a carrier immobilized functionalbacteria was used to remove recalcitrant pollutants.The preparation conditions and characterizations of growth and structure werestudied with Aspergillus Y3. The results showed that sucrose and ammoniumchloride were the best carbon and nitrogen sources for the growth of mycelial pellet,and the best concentrations were10g/L and1g/L, respectively. Temperature andshear force influenced the preparation process of mycelial pellet significantly. Thebiomass of mycelia increased by the temperature rose within a certain range, and themaximum biomass of mycelia about5.25g/L was gained under the shear force of160r/min rotation speed. Mycelial pellet grew rapidly (72h was used from sporesinoculated to mycelial pellet maturation), and had good settlement performance(Settling velocity of mycelial pellet with3mm diameter was about0.01m/s).Mycelial pellet had a good adsorption to bacteria (7.7×1010cfu/g dry weightmycelia) because of its large pore structure, positive surface charged, adhesioncoursed by extracellular polymeric substances. And mycelial pellet or combinedpellet with functional bacteria could be freeze-dried.There was a poor structural stability in application process of mycelial pellet asa biomass carrier because its large pore structure characteristic. Therefore,structural stability of mycelial pellet was enhanced by adding bio-flocculant. It wasfound that the integrity rate of mycelial pellet was raised from75.1%to83.6%and the dry weight from0.0677g/100mL to0.0767g/100mL by adding bio-flocculantwithout changing the internal structure. In addition, directional shear stress tomycelial pellet obtained by improving reactor hydraulics conditions so that thedamage caused by confusion stress could be avoided. It was also an effective meanto improve the structural stability extend service life of mycelial pellet.The feasibility of target pollutants removal by mycelial pellet as a biomasscarrier was studied in sequencing batch reactors (SBR). The results showed thatpurification of aniline was stable after7cycles running of the system, and theremoval efficiency of aniline was0.9mg/(mg biomass·d), significantly higher thanthe control system with activated sludge,0.6mg/(mg biomass·d). It was proved thatmycelial pellets as biomass carrier is feasible. The effectively immobilized offunctional bacteria, stability maintaining of bacterial structure in system, and targetpollutants degradation were achieved. Tourmaline was used to improve thedegradation ability and adaptability of combined mycelial pellet, and reduced thestart-up time of SBR system from7cycles to only1cycle with more stability.Diversity and functional of bacteria immobilized on mycelial pellet wererealized based on the theory of niche separation and principle of microbialco-metabolism. And the combined mycelial pellet was used in sequencing batchair-lift reactor (SBAR) system. The results showed that the effluent indicators of thesystem were stable and had a strong resistance to the impact load with graduallyincreasing of influent aniline concentration. Aniline degradation andnitrification-denitrification processes were well conducted, with nitrogen removalrate about80%solving the problem that ammonia concentration was high ineffluent of aniline wastewater treatment system. The bacterial structure in systemwas stable and rich in diversity, and was mainly formed by Proteobacteria andActinobacteria, including the bacteria enhanced.Mycelial pellet immobilized phenol-degrading bacteria was selected to degradewastewater contained phenolic compounds in SBR as a supplement experiment toverify it had common adaptability to substrates as a biomass carrier. The resultsshowed that phenol-degrading bacteria grew and worked continuously in system.Phenolic compounds and TOC were removed stable after5cycles running, withtotal phenol removal efficiency of0.5mg/(mg biomass·d), significantly higher thanthe control activated sludge system0.4mg/(mg biomass·d). The bacterial structure in system was stable and rich in diversity, and was mainly formed by Proteobacteria,Actinobacteria and Bacteroidetes. Immobilization of function bacteria, maintainingthe bacteria structure and system stability, and degradation of target pollutants wereachieved by mycelial pellet as a biomass carrier.