固定化硝化菌群联合芽孢杆菌处理对虾养殖废水

Treatment of shrimp wastewater by combination of immobilized nitrifying bacterial consortia and selected Bacillus population

摘要:

【背景】高度集约化的对虾养殖业面临着日益严重的水污染问题，同步高效降解养殖废水中的有机物、氨氮和亚硝酸盐是对虾养殖业健康可持续发展的重要保障之一。【目的】通过分别固定化硝化菌群(Nitrifying bacterial consortia，NBC)和芽孢杆菌，优化菌群空间结构，提高菌群功能，实现同步高效降解对虾养殖废水中的有机物、亚硝酸盐和氨氮，保障南美白对虾养殖的可持续发展。【方法】采集养殖虾塘底泥进行硝化细菌自养富集和连续培养，利用16S rRNA基因高通量测序技术分析硝化菌群组成。从5株芽孢杆菌中筛选化学需氧量(Chemical oxygen demand，COD)降解能力最强的菌株。选用吸附和成球效果好的无毒包埋材料，通过正交实验优化固定化配方提高机械强度。选择硝化菌群和芽孢杆菌最适使用浓度进行分别固定化并联合应用于对虾养殖废水的处理。【结果】高通量分析结果显示硝化菌群中变形菌门(Proteobacteria，61.10%)占绝对优势，具有自养硝化功能的类群丰度达12.69%并呈高多样性。还包含丰度达47.44%的具有反硝化功能或者潜在反硝化功能的优势菌群和丰度达12.85%的光合细菌，是高有机负荷下硝化作用的重要补充，并可通过反硝化作用实现真正脱氮。COD降解能力最强的是解淀粉芽孢杆菌(Bacillus amyloliquefacien) YL-10，48 h内COD降解率达100%。固定化最佳配方为贝壳粉5%、海藻酸钠3%、交联剂氯化钙为4%、优化后的固定化小球其机械强度可达129.68 mN。固定化使硝化菌群的氨氮和亚硝酸盐降解率分别提高了128.13%和130.11% (P<0.05)，但对芽孢杆菌YL-10的COD降解率无明显提高。1×108 CFU/mL为硝化菌群和芽孢杆菌YL-10在养殖废水中最适使用浓度。在固定化硝化菌群和芽孢杆菌YL-10联合作用下，对虾养殖废水的氨氮、亚硝酸盐和COD浓度在48 h内分别由初始的6.32±0.12、5.69±0.11和65.29±1.14 mg/L降至0.03±0.03、0.06±0.01和0 mg/L (P<0.05)，降解率分别为99.57%、99.03%和100%。【结论】通过优化固定化有效提高硝化菌群的硝化作用，联合COD降解能力强的芽孢杆菌，同步高效降解对虾养殖废水中的有机物、氨氮和亚硝酸盐，为规模化应用于南美白对虾高密度养殖提供科学依据。

Abstract:

[Background] The highly intensification of shrimp culture industry is facing an increasingly serious problem in water pollution. Simultaneously and high-efficiently degradation of organic matter, ammonia and nitrite in shrimp wastewater is one of important guarantees for the sustainable and healthy development of aquaculture. [Objective] In order to promote sustainable development of Litopenaeus vannamei culture in China, high-efficiently degradation of organic matter, ammonia and nitrite of aquaculture wastewater was developed by combination of immobilized nitrifying bacterial consortia (NBC) and selected Bacillus population. [Methods] High-throughput analysis of 16S rRNA gene was applied to study NBC’s community, which was enriched from the bottom mud of local shrimp ponds. We screened the strain with the highest COD (chemical oxygen demand) degrading capability from five Bacillus strains, and selected nontoxic immobilizing materials with good absorption capacity and ball performance. Further, the immobilized formula was optimized by orthogonal test to improve the mechanical strength. The optimum use concentrations of NBC and selected Bacillus strain were evaluated for high-efficiently degradation of COD, ammonia and nitrite in shrimp wastewater, respectively. [Results] High-throughput analysis of 16S rRNA gene showed that NBC was dominated by Proteobacteria (61.10%), and the abundance of autotrophic nitrifying bacteria in NBC was 12.69% with high diversity. NBC also contained denitrifying or potential denitrifying bacteria with an abundance of 47.44% and photosynthetic bacteria with an abundance of 12.85%. It is an important complement for nitrification under high organic loading and nitrogen removal through denitrification. Bacillus amyloliquefacien YL-10 has the highest COD degradation rate 100% in 48 h. The optimal formula for immobilization is 5% of shell powder, 3% of sodium alginate and 4% of calcium chloride. The mechanical strength of the embedding pellets is 129.68 mN. The immobilization significantly increased the degradation rate of ammonia and nitrite by 128.13% and 130.11%, respectively, but had no obvious effect on COD degradation. The optimum concentration of NBC and YL-10 was 1×108 CFU/mL. Under the joint action of immobilized NBC and YL-10, the concentrations of ammonia, nitrite and COD in shrimp farming wastewater were significantly reduced from (6.32±0.12), (5.69±0.11) and (65.29±1.14) mg/L to (0.03±0.03), (0.06±0.01) and 0 mg/L in 48 h (P<0.05), respectively. The degradation rates were 99.57%, 99.03% and 100%, respectively. [Conclusion] Organic matter, ammonia and nitrite in shrimp wastewater were biodegraded simultaneously and efficiently by combination of immobilized NBC and selected Bacillus population, which provides the scientific data reference for the large-scale practical application in high-density culture of L. vannamei.