Treatment Of Simulated Industrial Saline Wastewater By Halophilic Bacteria-plant Complex Ecological Floating Bed

In recent years,the scale of China's industrial production continues to expand,water consumption and wastewater discharge also continue to increase,one of which is saline wastewater,which has a great impact on the environment.With the increasing attention to surface and groundwater quality,the discharge and treatment of saline wastewater has been paid more and more attention.Among the many technologies for the treatment of saline wastewater,the ecological floating bed technology has the functions of cost-effectiveness,simple operation,and landscaping,which is suitable for the treatment of salt-containing wastewater with low salinity and small discharge.However,there are many organic pollutants in industrial salt-containing wastewater,which can hardly be effectively treated by ecological floating bed technology alone.In addition,salt ions inhibit the growth of plants,thus reducing the desalting function of the ecological floating bed.In view of this,this paper established halotolerant bacteria-plant complex ecological floating bed,and introduced AM fungi,through halotolerant bacteria degradation of organic pollutants,AM fungi to enhance the plant's salt tolerance and salt absorption efficiency,so as to improve the ecological floating bed treatment of salt-containing wastewater function.The main results are as follows:Experiments on floating bed plants inoculated with different AM fungi showed that:(1)AM fungi were acclimated for 15 days at the salt concentration of 5500 mg/L(H-AM)and 3500 mg/L(L-AM)respectively.The AM fungi-plants symbiont was taken out and inoculated into the floating bed plants with untreated AM fungi(N-AM)at the same time,the results showed that the contents of chlorophyll and root activity of floating bed plants in H-AM group were significantly higher than those in N-AM group,and the contents of MDA were decreased,especially in the environment without salt stress,compared with the control group,the root activity of H-AM group increased by 163.79%,while L-AM group had no significant positive effect.(2)Under salt stress,after inoculation with AM fungi,the root activity and chlorophyll content of floating bed plants were significantly increased,and the accumulation of MDA content in leaves was reduced.When the salt concentration reached 9000 mg/L,the activity of SOD enzyme in leaves was reduced.(3)After inoculation with AM fungi,the accumulation of Na+ in plants was reduced to a certain extent,and the absorption of K,Ca,Mg and other elements in floating bed plants was increased,especially the K+content of the aboveground parts of floating bed plants in the L-AM group increased significantly.The pot experiment of adding halotolerant bacteria to floating bed showed that:(1)Under salt stress,the addition of salt-tolerant microorganisms increased plant biomass and antioxidant enzyme activity to a certain extent,and decreased the accumulation of MDA and proline,at the same time,Na+uptake and Ca2+/Na+ ratio of aboveground and underground parts of plants were decreased,but K+/Na+ ratio was increased.(2)The absorption of di-2-ethyl hexyl phthalate(DEHP)in floating bed plants was reduced after the addition of halotolerant bacteria,especially when the concentration of DEHP in water was 20 mg/L and 40 mg/L,the uptake of DEHP by aboveground and underground parts of plants decreased by 52.9%,51.5%and 91.1%,72.0%respectively.(3)During the domestica-tion period,the species richness of salt-tolerant microorganisms increased gradually,and at the later stage,the growth rate was faster,while the diversity of microbial community showed a trend of decreasing first and then increasing.The effect of regular harvesting on the continuous salt absorption capacity of floating bed plants showed that:(1)Regular harvesting can significantly increase the absorption of Na+ by floating bed plants,and the Na+concentration in the aboveground and underground parts of plants increased by 56.4%and 30.0%after 10 days of harvesting,but reduced the absorption of K,Ca,Mg and other elements by plants.(2)After inoculation with AM fungi,both the aboveground and underground parts of the plant reduced the absorption of Na+,indicating that the inoculation of AM fungi reduced the stress of salt on plants.(3)Regardless of before and after harvesting,with the increase of treatment time,the absorption of Na,K,Ca,Mg and other elements of aboveground plants gradually increased,but the absorption of Ca2+ and Mg2+by underground plants decreased after 40 days.The experiments of halotolerant bacteria-plant composite ecological floating bed treatment to simulate industrial saline wastewater showed that:(1)Analysis of the microbial community in the three stages before,during,and after the experimental treatment period.In the mid-term,the growth rate of microorganisms was the fastest,and its richness was 1.84 times higher than that in the early stage,while the growth rate was slow in the later stage.In addition,some new species appeared in the later period,when the number of Actinobacteria increased,indicating that Actinobacteria adapted to the saline wastewater environment and became the dominant species.(2)The removal rate of TDS,COD,TN,TP and DEHP in the wastewater was improved by the composite ecological floating bed.After 37 days of treatment,the removal rate was 45.87%,74.1%,57.1%,63.1%and 94.9%,respectively,which was 6.91%,8.0%,7.6%,7.0%and 7.7%higher than that of the single floating bed.(3)Under salt stress,a series of photosynthetic parameters such as net photosynthetic rate,stomatal conductance and intercellular carbon dioxide concentration of plants were increased after the addition of halotolerant bacteria,indicating that it enhanced the photosynthesis of plants and alleviated the stress of wastewater on plants.