低剂量硝酸钙联合低氧曝气对黑臭底泥的修复探究

Restoration of Black-Odorous Sediment by Low-Dosage Calcium Nitrate Combined with Hypoxic Aeration

底泥内源污染是导致黑臭水体“反弹”的主要因素.为防止水体黑臭现象反复,以低剂量硝酸钙为修复剂,联合低氧曝气技术修复底泥,降低因ρ(NO3^--N)剧增而造成的生态风险,并对修复过程中菌群转化规律进行探究.结果表明:①当硝酸钙投加量为底泥质量的1.2%、低氧曝气量为0.05~0.10 m^3/h时修复效果最佳,其上覆水中ρ(DO)和ORP分别升至4.08 mg L和119.9 mV,NH3^-N、TOC(总有机氮)去除率平均值分别达42.5%和84.9%.②底泥中NH 3-N和AVS(酸挥发性硫化物)去除率平均值分别达76.8%和97.4%,投加低剂量硝酸钙不会造成NO3^--N在底泥中长期累积.③高通量测序分析表明,底泥优势菌群在纲水平上由梭菌纲(Clostridia)转变为γ-变形菌纲(Gamma-proteobacteria),其相对丰度达60.0%,且厌氧菌群被有效抑制;在属水平上出现产黄杆菌属(Rhodanobacter)、硫杆菌属(Thiobacillus)和热单胞菌属(Thermomonas)等脱氮菌群.研究显示,低剂量硝酸钙+低氧曝气技术可有效改善底泥-上覆水体系DO条件,加快系统的脱氮速率,抑制AVS的生成,促进底泥优势菌群转化并降低生态风险.

The internal source pollution of sediment is the main factor that leads to the recurrence of black-odorous water.To prevent this phenomenon,low dosage calcium nitrate was combined with hypoxic aeration technology to repair the sediment of black-odorous water.The purpose of this study is to reduce the ecological risks caused by the increase of nitrate nitrogen concentration,and to explore microbial transformation during the remediation process.The results showed that:(1)When the mass ratio of calcium nitrate sediment and intermittent hypoxic aeration were 1.2%and 0.05-0.10 m^3/h,respectively,the black-odorous sediment restoration effect was the best.The concentrations of dissolved oxygen(DO)and oxidation reduction potential(ORP)in overlying water increased to 4.08 mg L and 119.9 mV,respectively,and the removal rate of ammonia nitrogen(NH3^-N)and total organic carbon(TOC)reached 42.5%and 84.9%.(2)The contents of NH3^-N and acid volatile sulfide(AVS)in sediment were reduced by 76.8%and 97.4%,respectively.Low dosages of calcium nitrate are unable to result in nitrate nitrogen accumulation in the sediment.(3)The results of high-throughput sequencing showed that the dominant bacterial community in sediment was transformed from Clostridia to Gamma-proteobacteria(abundance of 60%)at Class level.Denitrifying bacteria,such as Rhodanobacter,Thiobacillus and Thermomonas,were found at Genus level.The study revealed that low-dosages calcium nitrate+hypoxic aeration technology can effectively improve the DO conditions of the sediment-overlying water system,inhibit the formation of AVS and promote the growth of dominant denitrifying bacteria.