Toxicity Of Coking Wastewater And Graphene Oxide On Aquatic Organisms

Anaerobic/anoxic/oxic(A/A/O)process is commonly used for the coking wastewater treatment.However,limit is known about its in bio-toxicity removal from coking wastewater.In addition,the graphene oxide(GO),a promising carbon-based nanomaterial,exhibits the unique electronic and mechanical properties.The versatile manufacture and application of GO made it inevitably release into the aquatic environment.However,limit is known about the potential risk of GO in aquatic environment.Our study mainly includes two parts as follows.(1)The toxicity profile of coking wastewater from the A/A/O process was investigated with crustacean(D.magna)and zebra fish(D.rerio),in respect to acute toxicity,oxidative damage and genotoxicity.The potential relationship between the bio-toxicity and physiochemical parameters was analyzed.The results showed that the acute toxicity of raw influent was reduced gradually along with A/A/O process and the anaerobic tank was observed to play a dominant role in the acute toxicity removal.The effluent from A/A/O process presented no acute toxicity to D.magna and D.rerio.Moreover,the oxic and anoxic tank reduced the oxidative damage and the effluent from A/A/O process still exhibited oxidative damage.In addition,the genotoxicity to D.rerio was removed stepwise by A/A/O process,although the final effluent still presented genotoxicity to D.rerio.The results indicated that the A/A/O process was efficient in acute toxicity removal,but not effective in the removal of oxidative damage and genotoxicity.The results of correlation analysis revealed that the acute toxicity to D.magna and D.rerio was significantly and positively correlated with organic chemicals and ammonia nitrogen.No significant correlations were found between the oxidative damage and genotoxicity and the physiochemical parameters.Our study gained an insight into the performance of conventionally biological processes in bio-toxicity removal and helped the introduction of toxicity index in the regulation system of wastewater discharge.(2)The acute toxicity and semi-chronic toxicity of GO was tested using D.magna.And the toxicity mechanism of GO to D.magna was explored preliminarily by the light microscopy,the measurement of reactive oxygen species(ROS)level,superoxide dismutase(SOD)and catalase(CAT)activities and malonaldehyde(MDA)content.Moreover,the influence of humic acid(HA)on GO toxicity was evaluated.The results showed that the 48 h-LC50 of GO in acute toxicity tests was 84.2 mg/L.The 21 d-LC50 in semi-chronic toxicity tests was 3.3 mg/L.When the concentration of GO reached 1 mg/L,the reproduction of D.magna was significantly delayed in the production time of the first brood;The offspring number of the first brood was inhibited,as well as the offspring number of the most productive brood and the total number of offspring.The results revealed that gut clogging and oxidative damage might be the main obvious toxicity path of GO to D.magna.HA mitigated the acute toxicity and oxidative damage induced by GO when the concentration of HA was 25 mg/L.This study provided the basic toxicity information of GO in respect of its industrial application and gave an example of the toxicity research for novel chemicals.