Biological treatment of wastewater with high concentrations of zinc and sulfate ions from zinc pyrithione synthesis

An enriched and domesticated bacteria consortium of sulfate-reducing bacteria(SRB)was used to treat wastewater from zinc pyrithione(ZPT)production,and the effects of different reaction parameters on sulfate reduction and zinc precipitation were evaluated.The single-factor experimental results showed that the removal rates of Zn2+and24SO?decreased with an increased ZPT concentration ranging from3.0to5.0mg/L.Zn2+and24SO?in wastewater were effectively removed under the conditions of30?35°C,pH7?8and an inoculum concentration of10%?25%.The presence of Fe0in the SRB system enhanced Zn2+and24SO?removal and may increase the resistance of SRB to the toxicity of Zn2+and ZPT in wastewater.A Box?Behnken design was used to evaluate the influence of the main operating parameters on the removal rate of24SO?.The optimum parameter values were found to be pH7.45,33.61°C and ZPT concentration of0.62mg/L,and the removal rate of24SO?reached a maximum of91.62%under these optimum conditions.

Effect of Terminalia chebula Retz. extraction with water on Staphylococcus epidermidis activity and its biofilm formation

Background:Based on modern pharmacological studies,Terminalia chebula Retz.exhibits antimicrobial activity against a variety of bacteria.Previously,we found Terminalia chebula Retz.exhibited excellent antibacterial activity against Malassezia restricta.Methods:We determined the minimal inhibitory concentration(MIC)and minimum bactericidal concentration of Terminalia chebula Retz.extraction with water(TRW)against Staphylococcus epidermidis(including Staphylococcus epidermidis 1-15)using the microdilution method.Staphylococcus epidermidis 1(SE11),which was the most sensitive to TRW,was selected as the test bacterium for subsequent experiments.The time-kill curve of TRW on SE11 was generated using the viable count method.Further,an in vitro biofilm model of SE11 was constructed using the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-((phenylamino)carbonyl)-2H-tetrazolium hydroxide test,semi-quantitative crystal violet experiment,and scanning electron microscopy.The effects of TRW on the total amount of biofilm formation,the number of viable biofilm bacteria,and biofilm microstructure of SE11 were also determined using a semi-quantitative crystal violet experiment,viable count method,and scanning electron microscopy.Finally,the electrical conductivity and soluble protein content of the SE11 suspensions were determined.Results:The average MIC of TRW against SE11 was 0.75±1.09 mg/mL.TRW(1/2MIC and 2MIC)and zinc pyrithione(1/2MIC and 2MIC)had no significant effect on total biofilm inhibition in the adhesion stage(P>0.05)and the aggregation stage(P>0.05).Further,TRW(1/2MIC and MIC)and zinc pyrithione(1/2MIC and MIC)had no significant effect on viable biofilm bacteria in the adhesion stage(P>0.05)and aggregation stage(P>0.05).TRW destroyed the integrity of the SE11 cell membrane,resulting in leakage of intracellular substances.Conclusion:TRW inhibits SE11 biofilm formation and is similar to zinc pyrithione in the adhesion and aggregation stages,which provides a theoretical basis for its application in the field of antimicrobial additives.