堆肥物以及堆肥物与铁屑联用原位修复硝酸盐污染地下水研究

摘要

针对地下水硝酸盐污染问题,借助柱实验开展堆肥物以及堆肥物与铁屑联用(以下简称堆肥物+铁屑)分别用于原位生物修复的动态模拟研究,考察生物反硝化的运行效果,探讨水化学参数的变化,分析硝酸盐的转化过程,确认地下水流速和进水硝酸盐浓度的影响,力求拓展纤维素类固体有机碳源的种类和提高纤维素固体有机碳源的反硝化速率.结果表明,堆肥物与堆肥物+铁屑引起的 NO3-去除率分别为75.08%~79.57%和82.24%~86.48%.堆肥物用于原位生物反硝化可行且高效,而且堆肥物+铁屑通过氢自养反硝化更能增强NO3-的去除.堆肥物与堆肥物+铁屑引起的反硝化速率分别为9.69和11.30 g·m-3·d-1,显著高于锯屑的反硝化速率(0.30 g·m-3·d-1).25~100 d时,堆肥物引起的总有机碳(TOC)质量浓度增量始终≤18.34 mg·L-1.在运行期间(0~100 d),堆肥物引起出水pH值始终低于进水值.堆肥物+铁屑引起TOC和pH值的变化展现出了与堆肥物相似的规律.运行10 d后,堆肥物以及堆肥物+铁屑将绝大部分NO3--N转化为气态氮.渗流速度和进水NO3-浓度显著影响堆肥物以及堆肥物+铁屑的生物反硝化效果.%In order to solve the problem of nitrate contamination in groundwater, dynamic simulation column studies on compost and compost+iron chip promoting in-situ bio-remediation were carried out. The objectives were to investigate the operating performances,to explore the changes in hydrochemical parameters,to analyze the transformation processes of ni-trate,to identify the effects of groundwater velocity and influent nitrate concentration,to broaden the types of fiber-based solid organic carbon sources and to improve their denitrification rates. Results show that NO3-removal efficiencies of com-post and compost+iron chip were 75.08%-79.57% and 82.24%-86.48%,respectively. Using compost for in-situ biolog-ical denitrification is feasible and efficient,and compost+iron chip performs better for nitrate removal via hydrogenotrophic denitrification. At the beginning of operation(≤8 d), compost readily led to the effluent NO2- concentration above the Chinese drinking water standard(GB 5749-2006), and meanwhile compost+iron chip readily resulted in the effluent NH4+concentration above the Chinese drinking water standard(GB 5749-2006).Denitrification rates of compost and com-post+iron chip were 9.69 and 11.30 g·m-3·d-1, respectively, which were significantly higher than the value of saw dust(0.30 g·m-3·d-1).Total organic carbon(TOC)increment(≤18.34 mg·L-1)was kept stable during the period of 25-100 d for compost. During the period of 0-100 d for operation,effluent pH was always lower than the corresponding influent value for compost.The similar trends of TOC and pH were observed for compost+iron chip.After 10 d,most of the influent NO3--N was transformed into gaseous nitrogen in the presence of compost and compost+iron chip, respectively.Removal efficiency decreased from 76.84% to 48.32% for compost and from 85.22% to 55.98% for compost+iron chip with Darcy velocity increasing from 0.5 to 2.0 m·d-1. Removal efficiency decreased from 76.44% to 44.87% for compost and from 85.42% to 65.46% for compost+iron chip with influent NO3- concentration increasing from 100.58 to 301.02 mg·L-1. Darcy velocity and influent nitrate concentration both have significant effects in biological denitrification performance of compost and compost+iron chip,respectively.