Constructing The Acid Mine Wastewater Treatment System By Taking The Straw As Carbon Source

The anaerobic treatment represented by the Sulfate-Reducing Bacteria(SRB)has advantages such as stable process,strong adaptation,and good recoverability in acid wastewater treatment,and is of relatively good actual application prospect.In this research,laboratory culture is used in the early stage to determine the optimal inoculation stage of the SRB solution.On this basis,methanoic acid,lactic acid,sodium lactate,sodium formate,leach liquor of rice straw,ethyl alcohol,glucose,methyl alcohol,and sucrose are used as the organic substrates for enrichment culture of the SRB solution.Static experiment is conducted,with the leach liquor of rice straw as the carbon source,to compare the impact of different inoculum sizes,initial pH values,temperatures,and Fe²⁺content on the SRB solution activity,and then to determine the optimal growing environment for the bacteria solution.Then,domestication and subculture are implemented for the SRB solution to enable the SRB solution to adapt to the acid environment.In this way,dynamic experiment can be further carried out for the SRB solution after being inoculated and domesticated in the first-level anaerobic reactor.Through observing the impact of different Hydraulic Retention Time(HRT),?(COD)/?(SO₄^2-)in water ingress,and multiple carbon source additions on the anaerobic reactor processing effect,the operating process parameter settings for the first-level anaerobic reactor are optimized.The second-level anaerobic reactor is used to process simulated acid heavy metal wastewater,and the indicators of the wastewater are measured and compared with those in Integrated Wastewater Discharge Standard(GB 8978-1996),to evaluate the feasibility of using the second-level anaerobic reactor for actual wastewater treatment.This research will serve as the theoretical guide for using the second-level anaerobic reactor in actual acid mine wastewater treatment.The following lists related experiments:(1)The indoor culture experiment indicates that the SO₄^2-removal rate of rice straw extraction liquid system was up to 67%,which was lower than that of the system using sodium lactate as carbon source.In perspective of economic suitability,the SRB solution under enrichment culture using the leach liquor of rice straw as carbon source shows certain superiority.(2)The static experiment shows that increasing the inoculation size has positive impact on the removal of sulfate,a pH value greater than or less than 7 has negative impact on the removal of sulfate,temperature greater than or lower than 35?prohibits the activity of the SRB solution,and in the range of 25-400 mg/L of Fe²⁺,increasing the content of Fe²⁺will firstly increase the removal rate and then lower the removal rate of sulfate.The optimal growth environment conditions for the SRB solution are inoculation size of 15%,initial pH value of 7.0,temperature of 35?,and Fe²⁺content of 50 mg/L.(3)The dynamic experiment shows that the SRB solution after domestication and subculture can effectively increase the treatment effect of the first-level anaerobic reactor on acid wastewater,and compared with the SRB solution before domestication and subculture,the SRB solution after domestication and subculture increases the removal rate of SO₄^2-in the effluent by 6 times,and the pH value by 1.2.The load increasing experiment shows that the load of SO₄^2-in water ingress greater than 3000 mg/L has negative impact on the wastewater treatment for the reactor.Prolonging the HRT can promote the treatment efficiency,and consequently increase the load of SO₄^2-in water ingress.The optimal process for the first-level anaerobic reactor is HRT of 24 hours,?(COD)/?(SO₄^2-)in water ingress of 2 to 3,carbon source addition every 6 days,and load of SO₄^2-in water ingress of 3000 mg/L.(4)The first-level anaerobic reactor has a low removal rate of COD.Increasing the reaction orders can lower the COD concentration in effluent.After 36 consecutive days of wastewater treatment in the second-level anaerobic reactor,the SO₄^2-concentration in the effluent is 82.01mg/L,COD concentration is 1023.6 mg/L,the pH value is 7.95,and the concentrations of Cu²⁺Fe²⁺,Mn²⁺,Zn²⁺,and Ni²⁺are 0.85 mg/L,0.63 mg/L,1.25 mg/L,4.21 mg/L,and 0.72mg/L,respectively.According to the integrated wastewater discharge standard,the SO₄^2-concentration,pH value,and heavy metal concentrations comply with the discharge standard,and the COD concentration of the effluent significantly decreases compared with that of the first-level anaerobic reactor but still does not comply with the discharge standard.In the post phase,the reactor with the SRB solution inoculated can be used for further treatment of the effluent to obtain the water quality that complies with the discharge standard.