Effect On The Treatment Of Nitrobenzene Wastewater In Artificial Wetlands

Nitrobenzene which is main intermindates of medicine and dyestuff,materials of detonator and pesticide is widely used in the process of rapid industrialdevelopment. Meanwhile, a large number of nitrobenzene wastewater discharged intorivers and lakes could produce severe pollution and cause great harm, as nitrobenzenehas a strongly biological toxicity. Therefore the removal of nitrobenzene will becomean important task for environmentalists.At present, the principal treatment processes for nitrobenzene wastewater arephysical, chemical and biological processes. Physical processes can be used aschemical and biological pretreatment, such as adsorption. The equipment of physicalprocesses is relatively simple, the processing cost is not high, but causing secondarypollution easily; The removal efficiency of nitrobenzene wastewater by chemicaltreatment is higher, but the equipment used is complicated, the processing cost isrelatively high, and there are also the problem of secondary pollution; Biologicalprocess has low cost and small environmental interferences. But nitrobenzenewastewater usually only is treated by using biological method after the physical andchemical pretreatment, because it is very difficult to be degraded. It is pointed out thatthe effective combination of the three processes would be future developmentorientation of treatment technologies for nitrobenzene wastewater.The constructed wetland system is a special sewage treatment technology, whichis the combined effect of the physical, chemical and biological processes withpacking, plants, microorganisms.In recent years, the wetlands have been widely usedin dealing with industrial wastewater drained from farming, paper, rubber, oilindustry and urban sewage, and have achieved remarkable results. Compared withother treatment technologies, constructed wetlands investment, energy consumptionand running costs are low, and the technology has a good landscape effect.Removal of nitrobenzene from an artificial wastewater was investigated usinglaboratory-scale constructed wetlands under different conditions. The water hyacinth, EA(Echinodorus amazonicus), calamus-constructed wetland systems on removalefficiency of nitrobenzene were respectively66%～78%,79%～92%,83%～93%;After A. Baumannii (cc-2) was directly added in water hyacinth and otherplants-constructed wetlands, the purification capacity had improved. With thetreatment of emergent plant and A. Baumannii-constructed wetlands, the trends of NBremoval were in the order of EA and cc-2> calamus and cc-2> water hyacinth andcc-2. The efficiencies were greater than the results of their separate role, less thantheir role together, we could see a synergy between plants and the cc-2. The removalefficiency of the wetland without plant and cc-2was maintained more than70%between0.9g/(m3·d) and3.4g/(m3·d), however, when the pollution load was4.5g/(m~3·d), the removal rate of nitrobenzene decreased, making the pollution load downto the initial level, the removal rate of nitrobenzene could restore within2h. Theresult indicated high pollution load bearing capability could be obtained in the device.