粒状铁与甲醇支持的生物-化学联用法去除富氧地下水中硝酸盐

针对富氧地下水中硝酸盐,采用粒状铁和甲醇支持的生物-化学联用法开展了批实验研究,优化了脱氮反应参数,初步探讨了脱氧脱氮的能力及途径。结果表明,该法的优化参数是粒状铁种类为GI-北京,m（粒状铁）∶m（水）为3∶800,粒状铁粒径为0.425~1.0 mm,反应时间为5 d,甲醇用量为210.59 mg.L-1。生物-化学法、粒状铁和好氧异养菌完全脱氧所需的时间分别是174、206和2 746 min。生物-化学法脱氧依赖于粒状铁化学还原和好氧异养菌有氧呼吸,并且前者起着关键作用。随着反应时间的增加,异养脱氮、自养脱氮和化学还原各自引起的NO3-去除率亦增加。当反应时间≤5 d时,自养脱氮和化学还原的去除率均〈10%,而当反应时间为5 d时,生物-化学法的NO3-去除率达到近100%。生物-化学法内存在异养脱氮、自养脱氮和化学还原3种脱氮途径,其中异养脱氮是最主要的途径,且三者存在共生、协同和促进作用。生物-化学法脱氮期间硝酸盐还原速率≥亚硝酸盐还原速率。生物-化学法去除地下水中硝酸盐是有效可行的。

A combined biological-chemical approach supported by granulated iron and methanol for nitrate removal from oxygen rich groundwater

According to the target contaminant-nitrate（NO3） in oxygen rich groundwater,a combined biological-chemical approach supported by granulated iron and methanol was put forward.Batch tests were conducted to optimize denitrification reaction parameters,and preliminarily explode the capacities and pathways of deoxygenation and denitrification.The results indicated,the optimal parameters,i.e.,granulated iron type of GI-Beijing,granulated iron： water ratio of 3： 800（in weight）,granulated iron particle size of 0.425~1.0 mm,reaction time of 5 day,methanol mass concentration of 210.59 mg.L-1,were identified.174 min,206 min and 2746 min were needed to completely remove DO for the biological-chemical approach,granulated iron and aerobic heterotrophic bacteria,respectively.The deoxygenation of the approach depended on granulated iron-based chemical reduction and aerobic heterotrophic bacteria-based aerobic respiration,and the former played a key role.With increasing reaction time,NO3 percent removal by respective heterotrophic denitrification（HD）,autotrophic denitrification（AD） and chemical reduction（CR） increased.The percent removal efficiencies by AD and CR were lower than 10% at reaction time ≤ 5 days,whereas the corresponding value by the approach was close to 100% at reaction time of 5 days.The biological-chemical approach relied on 3 denitrification pathways-HD,AD and CR,and HD was the most important pathway.There existed symbiotic,synergistic and promotive effects of CR,HD and AD within the system of the approach.Nitrate reduction rate was greater than（or equal to） nitrite reduction rate during denitrification by the approach.It’s feasible and effective for the biological-chemical approach to remove nitrate from groundwater.