Transport Characteristics Of Pathogens In Reclaimed Water Being Used In Copper-molybdenum Flotation Process

Based on the public health risk associated with the use of the reclaimed water for flotation process,The occurrences of pathogens in flotation process and interfacial adsorption of of pathogens onto ore particles were investigated.Based on contact angle and Zeta potential of model materials,the interaction energy in sorption of pathogens on Copper-molybdenum ores was calculated using both classical DLVOand extended DLVO theory,and the mechanism of pathogens adsorption was discussed.The public health risk associated with the use of the reclaimed water in the flotation was evaluated based on the quantitative microbial risk assessment(QMRA)approach.The results can be presented as follows:MS2,ΦX174 and E.coli in reclaimed water can be rapidly adsorbed onto ore particles.Since a near complete removal of pathogens are achieved in grinding process,more than 95%pathogens are attached onto tailings,the leftover pathogens are adsorbed by middling and tailings,which can pose a health risk to workers under a particular exposure levels.lintailing wastewater without any pathogens is safety to reuse to floatation process.The adsorption of pathogens onto ore particles is in agreement with XDLVO theory,which is governed by hydrophobic reactions and specific adsorption.The adsorption capacity orders of pathogens on Copper-molybdenum ores is ΦX174>MS2>E.coli,the maximum energy barrier calculated by the extend DLVO follows the order of E.coli>MS2>ΦX174,The E.coli is significantly irreversible adsorpted/inactivated on the surface of Copper-molybdenum ores due to the cell surface polymers bridging between the E.coli andCopper-molybdenum ores.Increase in solution pH from 7.5 to 9.5,remove of MS2,ΦX174 and E.coli decreases by 38.19%,9.30%,53.70%respectively,adsorption rate coefficient decreases by 26.6%,15.83%,69.10%respectively.The presence of PO43-、CO32-are able to compete the adsorptive sites which decreases the adsorption of pathogens onto ore particles.As the shielding effect of Ca2+and Mg2+,the remove of MS2,ΦX174 and E.coli increases by 0.64%,0.5%,35.57%respectively.Thcattachmcnt of pathogens on mineral particles increases significantly at the presence of collector kerosene,PJ053 and pH adjusting agents CaO,turpentine oil dose not have obvious influence on the adsorption of pathogens.The public health risk associated with use of reclaimed water in flotation process was conducted by the method of quantitative microbial risk assessment(QMRA).The concentration of Fecal Coliform reclaimed water are higher in wet season than dry season,more Fecal Coliform is observed in flotation water than ore particles.The annual infection probability of Fecal Coliform based on ingestion of 1 mL of ore particles ranges from 0.08 to 0.33during the dry and wet season,much higher than the maximum acceptable level(1.7 ×10-2).The values for ingestion of 1 mL flotation water range from 0 to 0.35,the probability of annual risk in acceptable level is 83%.The infection probability of Fecal Coliform are all in acceptable level using secondary effluent treated by ozone oxidation,which gives consideration to both flotation indexes and reuse safety,and can be applied to deal with the health risk associated with reuse of reclaimed water in flotation process.