Study On Treatment Of Saline Wastewater Using Three-dimensional Ecological Floating Bed Enhanced By AM

The treatment of saline wastewater has attracted increasing attention due to its extensive existence and great environmental hazards.At present,there are developed technologies for the treatment of high-concentration and large-flow saline wastewater,but few available technologies can be used to treat low-concentration(TDS<10000 mg/L)and low-flow saline wastewater.Ecological floating bed(EFB)technology may play an important role in the treatment of saline wastewater.However,salt removal efficiency of EFB may be low due to the fact that salt is removed by plant uptake and plant is sensitive to salt stress.Therefore,in this paper,AM fungi was used to increase plant tolerance to salt stress and increase EFB efficiency in salt removal,and make EFB three-dimensional to realize the utilization of EFB in limited space,indoor and outdoor,and cold regions.The main research results are as follows:(1)The screening experiment of EFB plants under salt stress showed that,five kinds of wet plants inoculated with AMF were treated with NaCl solution at different concentrations(0 g/L,3 g/L,6 g/L).The growth rate,SOD enzyme activity,soluble protein,and shoot K+/Na+of Canna indica,Cyperus alternifolius and Thalia dealbata are relatively higher than other two plants,indicating that these three plants have strong salt tolerance;Na+ion contents in the shoots of Ipomoea aquatica and Typha orientalis are higher than these of other three plants,showing that these two plants had Na+uptake ability.Consider all above factors,we chose Canna indica,Cyperus alternifolius and Ipomoea aquatica as EFB plants in this experiment.(2)The experiment about inter-colonization between mycorrhizal and non-mycorrhizal plants through root touching under salt stress showed that,in different concentrations(0 g/L,3 g/L,6 g/L)of NaCl solution,mycorrhizal Canna indica could infect non-mycorrhizal plants(Canna indica,Cyperus alternifolius,Ipomoea aquatica)through the root touching in saline water.The mycorrhizal colonization rate of Canna indica was 52.67%.After one month later,in water with 6 g/L NaCl mycorrhizal colonization rates reached to 31.33%,20.67%and 12%in Canna indica,Cyperus alternifolius and Ipomoea aquatica that were non-mycorrhizal before experiment respectively The experiment showed that under salt stress,the new root of EFB plant can be infected by the AM structure existed in the old roots independent of plant species.This can make EFB plant maintain high infection level of AM structure.(3)Experiment on factors affecting salt removal from saline wastewater using three-dimensional ecological floating bed enhanced by AM(AM-TEFB)showed that,? Salt removal efficiency could be increased by increasing water flow rate.The removal rates of TDS and Na+at a flow rate of 80 ml/min were higher than these at 40 ml/min;? Salt removal efficiency was slightly affected by wastewater TN concentrations(10 mg/L,40 mg/L)There was no significant difference in the removal of TDS and Na+,the removal rate of TP was lower at 40 mg/L TN relative to 10mg/L TN;?Salt removal efficiency could be increased by increasing wastewater P concentrations.The removal rates of TDS and Na+at 8 mg/L TP were higher than these at 2 mg/L TP.(4)Studies on the spatial differences in physiological and biochemical characteristics of AM-TEFB showed that the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),intercellular CO2 concentration(Ci),photochemical quenching(qP)and electron transfer rate(ETR)in the leaves of upper plants were higher than those in the leaves of the lower plants.However,there was slight difference between upper and lower plants in the effective quantum yield(Fv'/Fm')and non-photochemical quenching(qN).There was no significant difference in the contents of K+,Na+,Ca2+and Mg2+in the upper and lower plants.The above indexes in the leaf towards sun were higher than these backwards sun,but the difference is not significant(P>0.05).This showed that the AM-TEFB plant growth may be affected by light,and this should be fully considered when AM-TEFB is applied.(5)Research on the effect of AM-TEFB on the treatment of saline wastewater showed that,AM-TEFB had a good purification effect on saline wastewater,and the removal rates of TDS and COD reached 36.02%and 72.1%.The removal rates of TN were 64.6%and 54.2%in the two stages,and were 67.0%and 51.1%for TP removal respectively.No evident difference was found in the saline wastewater between AM-TEFB and two-dimension EFB.