Mercury Pollution And Mercury Wastewater Treatment Technology In Guizhou Province

Guizhou is the greatest mercury (Hg) production center in China, and it’s alsothe highest Hg pollution area. Hg pollution and ecological risk study in a largeregional scale was necessary. Through the investigation of Hg pollution source andenvironmental media in Guizhou, the distribution of Hg and methymercury (MeHg) inatmosphere, water and soils were presented by ArcGIS software to illustrate thepollution of Hg in Guizhou province.Then the geoaccumulation index and potentialecological risk index were applied to assess the pollution and ecological risk of totalmercury (THg) in soils, respectively. For surface water, single factor method wasemployed to evaluate THg pollution and the safety threshold method to assess theecological risks of reactive mercury (RHg) and methylmercury (MeHg). Single indexmethod was applied to assess the ecological risk of THg in organisms. In the last,different Hg wastewater treatment technologies were developed for Hg concentrationdifferences in process of production. HCl-treated Microcystis was applied to removeHg from high Hg concentration of wastewater, and FeCl3-treated volcanic rock werefor the treatment of low Hg concentration of wastewater. The results showed:1) high mercury pollution was appeared in those Hg mining areas located in theNortheast and Southwest of Guizhou province. It is obvious that the total Hgconcentrations in contaminated sites were regionally higher than other places, and theHg levels in crops were excessive. High MeHg concentrations were presented inurban rivers as well as waters close to mining areas, indicate that the distribution ofMeHg in waters should be related to the mining and human living. But Hg content offish in these waters was below the national food standars.2) There was a serious Hg pollution in soils close to mercury-related mines andfactories. The proportion of serious Hg pollution, heavy pollution, emphasis pollutionand moderate pollution for these39soil samples in mercury mines or factories were79.49%、10.26%、7.69%and2.56%, respectively. Meanwhile, the potential ecologicalrisk of THg in soils of these areas were extremely high. There was a moderate Hg pollution in soils of the other areas, and the potential ecological risk was acceptable.The Hg pollution was serious in water close to mercury mine, lead-zinc mine andorganic chemistry factory, however the ecological risk of Hg was negligible due tolow concentration of RHg and MeHg. And in general, the ecological risk of Hg in fishof Guizhou water bodies was also negligible.3) The high adsorption by the algal was obtained under the treatment of0.1mol/L HCl. HCl-modified algal adsorbent had a fast adsorption rate for Hg fromhigh Hg concentration of wastewater, adsorption equilibrium at30min. Theadsorption rate was up to95%in the dosage range of0.1%to0.4%, and was notsignificant in the acidic environment. The biosorption processes obeyed theFreundlich isotherm model. The high desorption efficiency for Hg was achieved using5mol/L HCl, and the regeneration studies showed that the algal could be used for aminimum of five repetitive cycles for the removal of Hg. FeCl3modified volcanicrock had a rapid adsorption rate for Hg from <0.5mg/L Hg wastewater, up to75%～85%after15min, the adsorption equilibrium at1h. The adsorption was effected by pHin water, and the adsorption rate was up to92%in alkalicondition. The adsorptionprocesses obeyed the Freundlich isotherm model. The regeneration was achievedusing1mol/L HCl for desorption.