Study On Sewage/wastewater Treatment Technology And Its Application With Modified Basalt Fiber(MBF) Biocarrier

With the increasing prominence of water pollution problems,human health and the environment are seriously affected.Under the background of"double carbon",the existing wastewater biological treatment processes（such as oxidation ditch process,A²/O process,A/O process,traditional activated sludge method,etc.）generally have problems of high energy consumption,complex operation and large floor space.The biological contact oxidation method with carrier as the core has the characteristics of high volumetric load,strong adaptability,low residual sludge and easy operation and management,which is widely used,but the carrier has many technical bottlenecks（such as low biomass,easy to fall off,poor mass transfer,serious secondary pollution,etc.）,which affects the treatment effect and application of biocarrier.The new modified basalt fiber（MBF）is an inorganic micron-level material with the advantages of good chemical stability,corrosion resistance,large specific surface area,good hydrophilicity and bioaffinity,etc.,which has a broad application prospect.In this paper,we conducted an in-depth study on the water treatment technology of the new inorganic micron MBF biocarrier,firstly,we conducted a preliminary investigation on the wastewater treatment effect of MBF bio-nest,then we analyzed the growth process and formation law of MBF bio-nest,and by constructing MBF bio-nest reactor,we optimized the parameters of lateral spacing（HS）,longitudinal spacing（VS）and filling ratio（FR）to obtain the optimal parameter range of MBF bio-nest reactor,and finally,we conducted experimental research and efficiency evaluation on three typical wastewaters:alcohol wastewater,waste leachate and lithium battery slurry wastewater,and formed the following main conclusions.（1）In order to initially investigate the effect of MBF as biocarrier for wastewater treatment,MBF biocarrier was introduced in the reactor to study the water treatment effect,DO mass transfer effect,microbial activity and adsorption characteristics of MBF bio-nest.The results showed that the micron-sized MBF biocarrier could form spherical aggregates in the aeration tank with sizes larger than 10 cm or more.In the bioreactor using MBF biocarrier（R-BF）,the NH₄⁺-N removal efficiency of the R-BF reactor increased from 77.79%to 82.17%when the carbon to nitrogen ratio was increased from 5:1 to 20:1,while the TN removal efficiency of the R-BF reactor increased from 60.10%to 82.07%.Mass transfer effect and bio-vitality analysis using DO microelectrodes and laser scanning confocal microscopy（CLSM）showed that DO could be distributed in a gradient to reach the core of the MBF bio-nest and live microorganisms could be detected at the core.FTIR tests indirectly showed that functional groups of polysaccharides（PS）and proteins（PN）in tightly bound extracellular polymers（TB-EPS）played a key role in the bio-nest formation plays a key role.（2）The growth process and formation law of bio-nests cultured under two microenvironments,anaerobic and aerobic,were studied.The results showed that the formation process of MBF bio-nests is a dynamic process of microbial adsorption,growth and shedding,which can be divided into four periods:adaptation,forming,maturation and stabilization.The bioactivities of the inner,middle and outer layers(Y_28N,Y_28Z and Y_28W)of the MBF nests were 63.89%,80.03%and 88.15%,respectively,at the 28th d of stabilization in the anaerobic environment.The bioactivities of the inner,middle and outer layers(H_28N,H_28Z and H_28W)were 64.60%,81.44%and 88.56%,respectively,during the stabilization period of 28th d.The microbial communities were gradually enriched and diversified during the growth and formation of MBF bio-nest,and the biochemical cycle was enhanced.The MBF bio-nest formed under aerobic environment were more advantageous in the removal of organic pollutants,and the MBF bio-nest formed under anaerobic environment were more advantageous in the removal of TN.（3）The MBF bio-nest reactor was constructed,optimized and evaluated for efficiency.The optimum HRT of the MBF bio-nest reactor was 6 h.The optimum parameters were:HS of 17.27 cm,VS of 15.04 cm and FR of 62.51%,and the highest removal rates of COD,NH₄⁺-N,TN and TP were 91.03%,89.4%,85.96%and71.29%,respectively.The secondary substrate removal model fit resulted in y=2.17284x-0.12833 with a correlation coefficient R² of 0.916;the modified Stover-Kincannon model fit resulted in y=2.19289x-4.33381 with a correlation coefficient R² of 0.918,U_max of 0.231 kg/m³/d and 0.506 kg/m³/d for K_B;the fitted curve for the Monod model had a correlation coefficient of 0.971,K_s of 1089.67 mg/L and q_max of 0.787 mg-N/mg VSS/d.The bioactivities of the MBF bio-nest formed from the inner to outer samples a-f under the optimal operating parameters were in the order of 36.57%,49.80%,The higher bioactivity,EPS,PS,PN,Humic Substance and microbial biomass in the MBF bio-nests promoted the formation of rich community diversity and microbial growth in the nest,and the degree of influence on the microbial community structure was From largest to smallest,EPS>PS>PN>Humic Substance>Activity.（4）The study evaluated the efficacy of MBF bio-nest treatment technology for three typical wastewaters（alcohol wastewater（high organic wastewater）,waste leachate and lithium battery slurry wastewater）.a)Alcohol wastewater:the MBF bio-nest reactor treated organic loading rate of 15.243 kg/m³·d and nitrogen loading rate of 1.068 kg/m³·d under low DO（1.0±0.3 mg/L）.The removal rates of COD,NH₄⁺-N and TN were 99.1%,97.9%and 97.8%,respectively,when the high concentration organic wastewater with a loading rate of 1.068 kg/m³·d was treated in the MBF bio-nest reactor under low DO（1.0±0.3 mg/L）conditions.The high biological activity（55.78%）,abundant biomass and diverse community structure in the bio-nest enabled R-BF to achieve high removal rates with low residual sludge production and energy consumption.b)Waste leachate:The MBF bio-nest enhanced the water treatment effect and heavy metal adsorption performance of the biological contact oxidation reactor for waste leachate.The application of MBF biocarrier in biological contact oxidation reactors can solve the problem of poor denitrification efficiency of traditional biochemical reactors and also reduce the cost of current landfill leachate treatment technologies due to advanced oxidation,membrane treatment and other complex processes.c)Lithium battery slurry wastewater:MBF bio-nest enhanced the treatment capability of R-BF for lithium battery slurry wastewater with low carbon to nitrogen ratio.Under low DO（0-1 mg/L）condition,R-BF achieved optimal pollutant removal while saving aeration energy.Kinetic modeling showed that the R-BF had efficient nitrogen removal performance for lithium battery slurry wastewater up to 4.462 kg/m³/d.The rich community diversity and microbial growth in the bio-nest enabled the R-BF to achieve efficient pollutant removal and produce low residual sludge production.In addition,the multidimensional structure of the MBF bio-nest solves the problem of high microbial enrichment and microbial exfoliation that cannot be achieved by conventional biofilms.The related functional groups of carbon and nitrogen cycles are the synergistic effects of hydrolytic fermentation,nitrification/denitrification and simultaneous nitrification denitrification（SND）,which together contribute to the treatment of wastewater.Through the above study,the water treatment technology of MBF bio-nest has high efficiency and practicality in treating wastewater,which can provide theoretical basis for the use of MBF bio-nest and scientific support for its application.Therefore,MBF bio-nest has a very broad application prospect in the direction of sewage/wastewater treatment.