Simultaneous Removal Of Zn²⁺and SO₄^2- From Wastewater Of Zinc Pyrithione Synthesis By Sulphate-reducing Bacteria

As an effective and safe antibacterial agent,zinc pyrithione has been intensively applied widely including in the production of shampoo,medicines,pesticides,dyes,catalysts and marine vessels,especially in shampoo.The wastewater in the production of pyrithionc zinc is a kind of acidic wastewater,containing a high concentration of zinc sulfate and still remains traces of the products of pyrithionc zinc.At present,in the treatment of heavy metal and high salinity wastewater,the most commonly used method is physical-chemical method.However,these methods all have the disadvantages of low efficiency,high costs,and the secondary pollution on the environment.Therefore,it is of great significance to treat wastewater with complex composition and high concentration by biological method.Sulfate-reducing bacteria used in pyrithione zinc production wastewater treatment can remove Zn²⁺ and SO₄^2-simultaneously,which can improve the treatment efficiency and reduce the cost of wastewater treatment.The main work of this study is as follows:1.Acquired of efficient and zinc tolerance SRB.To treat high concentration of Zn²⁺ and SO₄^2-in acid pyrithione zinc production wastewater more effectively,High zinc and acid tolerance of SRB had been acquired from leachate by screening and domestication.The effects of different concentrations of ZPT on the growth and metabolism of SRB were studied.2.Effects of main factors on SRB.The effects and mechanism of Zn²⁺,pH,temperature and inoculum size on the metabolism of SRB were studied by batch reaction under different ZPT concentrations.3.Effect of Fe⁰ on SRB metabolism.The removal efficiencies of Zn²⁺ and SO₄^2-by SRB and SRB+ Fe⁰ systems were investigated over time.The mechanism of Fe⁰ on the activity of SRB was discussed.The results showed that the high concentration of Zn²⁺ could inhibit the activity of SRB,and the highest tolerance of Zn²⁺ is 350 mg/L.The growth of SRB was inhibited in acidic environment and the suitable pH for SRB growth is from 7 to 8.At ambient temperature,low temperature had the strongest inhibitory effect on SRB.the suitable temperature for SRB is from 30 to 35?.When the inoculum was increased from 5%to 10%,the metabolic capacity of SRB was enhanced,but there no positive effect when the inoculation amount continued to increase.The metabolism of SRB was strikingly promoted by Fe⁰.Fe⁰ has an obvious effect in promoting treatment efficiency and effect.At the same time,it was found that ZPT had little effect on SRB under the suitable environmental factors,but the toxic effect of ZPT on SRB was enhanced in the condition of unsuitable growth.Under the suitable reaction conditions:initial zinc ion concentration is less than 250 mg/L,pH 7-8,temperature of 30?35 ?,inoculation amount is greater than 10%,sulfate reducing bacteria has a good effect on the removal of Zn²⁺ and SO₄^2-in the production of zinc pyrithione wastewater,the removal rate of Zn²⁺ can reach 90%,the removal rate of SO₄^2-can reach 85%.