Impact Of Heavy Metals In Livestock Wastewater On The Diversity Of Anaerobic Microorganism

In the thesis, the anaerobic treatment system running and bacterial diversity are studied with Cu²⁺ and Zn²⁺ added into livestock wastewater, providing reference to the treatment of livestock wastewater containing heavy metals. It is concluded that:?1? With no heavy metals added, the conditions for livestock wastewater treatment by anaerobic system were selected and optimized. The final optimum operating conditions are:inlet TOC 1000mg/L, pH 7.5 ?test result:7-8?.?2? Under the condition of adding Cu²⁺, the removal rate decreases from 99.49% to 42.20% with the concentration of Cu²⁺ increasing to 4.7224mg/L from 1.2605mg/L; TOC removal rate decreases from 85.48% to 13.89%; the amount of methane produced decreases from 155.30mL to 67.78mL; the inhibition rate of Test Group 3 ?Ccu=2.23mg/L? reaches 49.77%, so 2.23mg/L is the half inhibitory concentration.?3? Under the condition of adding Zn²⁺, Zn²⁺ absorbing capacity gradually increases but the removal rate decreases with the concentration of Zn²⁺ increasing to 29.8278mg/L from 3.0699mg/L; TOC removal rate decreases from 81.29% to 27.48%; the amount of methane produced decreases from 343.85mL to 83.67mL;the inhibition rate of Test Group 4 (C_Zn=13.64mg/L) reaches 49.59 percent, so 13.6381mg/L is the half inhibitory concentration.?4? Under the condition of adding Cu²⁺-Zn²⁺, the Cu and Zn content in anaerobic activated sludge also tend to be saturated with the increase of Cu²⁺ and Zn²⁺concentration, and finally become saturated, no longer increasing with Cu²⁺ and Zn²⁺ concentration increases. TOC removal rate decreases from 75.27% to 18.76%; the amount of methane produced from 228.91mL to 118.93mL; the inhibition rate of Test Group 51 (C_Cu=3.78mg/L, C_Zn=3.10mg/L)/Test Group 15 (C_Cu=1.24mg/L, C_Zn=17.14mg/L), Test Group 24 (Ccu=1.63mg/L, C_Zn=13.65mg/L), Test Group 33 (C_Cu=1.67mg/L, C_Zn=8.65mg/L) Test Group 43 (C_Cu=2.30mg/L, C_Zn=8.37mg/L) and Test Group 51 (C_Cu=3.78mg/L, C_Zn=3.10mg/L) have an inhibition rate of about 50%, so it is the half inhibitory concentration.?5? After PCR-DGGE technique and high-throughput sequencing, the phylum, class, order, family and genus that anaerobic microorganisms belong to undergone significant changes. It is found that with the increase of Cu²⁺-Zn²⁺ concentration, the abundance of bacterial population in granular sludge decreased significantly, and the bright stripes in all test groups decreased significantly in the DGGE experiment except Test Group 11 (Ccu=1.32mg/L, C_Zn=3.07mg/L), where bright stripes increased a little, which shows that Cu²⁺-Zn²⁺ of low concentration plays a promoting role on anaerobic microorganisms and Cu²⁺-Zn²⁺ of high concentration plays an inhibiting role on anaerobic microorganisms. Through the comparison of the microorganisms phylum distributions of Test Group 55 (C_Cu=3.77mg/L, C_Zn=17.34mg/L) combined by the controL group, Test Group 11 (Ccu=1.32mg/L, C_Zn=3.07mg/L), Test Group 15 (C_Cu=1.24mg/L, C_Zn=17.14mg/L) and Test Group 51 (C_Cu=3.78mg/L, C_Zn=3.10mg/L), Cu²⁺-Zn²⁺ of low concentration_<sub>plays_a promoting role on some microorganisms, such as Fimicutes, and some microorganisms will receive inhibition, such as Chloroflexi. Through the comparison between ACE sample sparse index and sample heat map, as well as PCA analysis, plot and other analysis, the control group showed a high degree of similarity with Test Group 15 (C_Cu=1.24mg/L, C_Zn=17.143mg/L), and also Test Group 51 (Ccu=3.78mg/L, C_Zn=3.10mg/L) and Test Group 55 (C_Cu=3.77mg/L, C_Zn=17.34mg/L).