Acute Toxic Effects Of Industrial And Municipal Wastewater On Scenedesmus Obliquus

The toxicity of seven industrial wastewaters (papermaking wastewater, printing and dying wastewater, pharmaceutical wastewater, pigment wastewater, refinery wastewater, acrylonitrile wastewater and coking wastewater) and municipal wastewater was investigated using the alga, Scenedesmus obliquus. Four endpoints, i.e. cell density, chlorophyll-A synthesis, superoxide dismutase (SOD) activity and cell membrane integrity, of alga were analyzed to characterize the acute toxic effects of wastewater. Performance for toxicity removal of wastewater treatment plants (WWTPs) with different treatment techniques (SBR, Linpor and conventional activated sludge) and sensitivity of the four endpoints of alga were compared.Firstly, toxic effects of industrial wastewaters on Scenedesmus obliquus and performance for toxicity removal of treatment techniques were investigated. Relationship between wastewater toxicity and physical-chemical indexes was explored and sensitivity of the four endpoints of alga was compared. The results showed that, all treatment techniques reduced the toxicity of industrial wastewaters significantly while the effluents still exhibited toxic effects on one or more endpoints of alga. NH3-N may be the main sourse of wastewater toxicity. The sensitivity order of the four endpoints was SOD activity> chlorophyll-A synthesis> cell density> cell membrane integrity.Secondly, the removal efficiency of WWTPs with different treatment techniques was investigated. Relationship between wastewater toxicity and physical-chemical indexes was explored and sensitivity of the four endpoints of alga was compared. The results showed that, all three techniques can completely remove the algal chlorophyll-A synthesis stimulation effect of influent, the algal cell growth stimulation effect was only completely removed by the conventional activated sludge technique, toxic effects on cell membrane integrity of two influents from WWTPs with SBR and conventional activated sludge techniques were completely removed, the acute toxicity on SOD activity was partially reduced in SBR and conventional activated sludge techniques while not significantly reduced by Linpor system. NaClO disinfection enhanced wastewater toxicity dramatically. The promotion effect of wastewater on algal chlorophyll-A synthesis was positively and significantly correlated with TOC and TP concentrations. The sensitivity order of the four endpoints was SOD activity> chlorophyll-A synthesis> cell density> cell membrane integrity.The study revealed that, industrial and municipal wastewater all presented acute toxic effects on Scenedesmus obliquus. Certain correlation existed between wastewater toxicity and physical-chemical indexes while the toxicity of wastewater cannot be predicted by one or several physical-chemical indexes. SOD activity and chlorophyll-A synthesis were more sensitive than cell growth, thus, could be used as endpoints for wastewater toxicity evaluation. Our results would aid to understand the acute toxicity of industrial and municipal wastewater, as well as the toxicity removal by currently utilized treatment techniques in China.