摘要
土壤含水层处理系统(soil aquifer treatment,SAT)是一种重要的人工回灌地下水方式。以再生水为回灌水源时,水中含有的"三氮"可能会对回灌区地下水造成污染风险。研究各种因素对在SAT中去除再生水中"三氮"的影响具有重要意义。本研究中,通过高200cm、内径50cm土柱试验,研究了SAT系统中粒径、干湿比(落干期与淹水期的比值)、在系统表层增加生物炭及渗透流速对实际再生水"三氮"去除效果的影响。结果表明,在干湿比1∶1条件下,实际河道细砂和中细砂柱底部出水中NH4-N平均去除率分别为73%和66%,去除机理主要为吸附和硝化作用,NO2-N基本被去除。系统中硝化作用导致NO3-N浓度升高,出水中NO3-N浓度平均增长了3.0%~4.1%。在深度115cm以上,中细砂柱内比细砂柱内的硝化作用更强,这导致了更高的NH4-N去除率和更低的NO3-N去除率。延长落干期后(干湿比3∶1),系统具有了更强的复氧能力,促进了硝化作用,使得NH4-N的平均去除率提高了20%,而NO3-N的降低了3%~4%,增加了NO3-N污染风险。在中细砂层添加5%重量生物炭后,吸附性能增强,使其对NH4-N平均去除率增加了20%~32%,但对NO3-N影响不明显。渗透流速与NH4-N的去除和NO3-N的增加均呈负相关。综合分析可得出,影响SAT系统去除"三氮"的最主要因素是干湿比和渗透流速,在回补水源中NH4-N浓度较高时,可考虑在SAT系统表层添加生物炭以增强其去除效果。
Soil aquifer treatment(SAT)is an important method of artificial groundwater recharge.However,when reclaimed water is used as recharging source,the nitrogen species in water may pose pollution risks to groundwater in the recharging area.It is of great significance,therefore,to study the effects of various factors on nitrogen removal from reclaimed water in SAT.In this study,through soil column experiments(using a column of 200 cm in height and 50 cm in inner diameter),the effects of particle size,dry/wet ratio,biochar addition,temperature and infiltration rates on nitrogen removal were studied.The results showed that under the dry/wet ratio of 1∶1,the average removal efficiencies for NH4-N in the effluents of fine and medium-fine sand columns were 73% and 66%,respectively,by adsorption and nitrification mainly,while NO_(2)^(-)N was almost totally removed.Nitrification resulted in a NO_(3)^(-)N concentration increase in the filtration system by 3.0%-4.1% on average in the effluent.Above the depth of 115 cm,nitrification was stronger in the medium-fine sand column than in the fine sand column,which resulted in a higher NH_(4)^(-)N and lower NO_(3)^(-)N removal rates.After prolonging the drying period(using dry/wet ratio 3∶1),the filtration system showed a stronger reoxygenation capacity promoting nitrification.It led to a 20% increase in the average NH4-N removal rate and 3%-4% reduction of NO_(3)^(-)N,thus increasing the risk of NO_(3)^(-)N pollution.After adding 5%biochar(by weight)to the medium-fine sand layer,the adsorption performance was enhanced,and the average NH4-N removal rate was increased by 20%-32%,but the effect on NO3-N was not obvious.The infiltration rate was negatively correlated with NH4-N removal and NO_(3)^(-)N increase.Based on the comprehensive analysis,it can be concluded that the main factors affecting nitrogen removal in SAT are the dry/wet ratio and infiltration rate.When NH_(4)^(-)N concentration in the water source is high,biochar can be added to the surface layer in SAT to enhance its nitrogen removal efficiency.
作者
高珩
谭行
任宇
朱乐诚
毕二平
GAO Heng;TAN Hang;REN Yu;ZHU Lecheng;BI Erping(Beijing Key Laboratory of Water Resources and Environmental Engineering,School of Water Resources and Environment,China University of Geosciences(Beijing),Beijing 100083,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2021年第5期125-135,共11页
Earth Science Frontiers
基金
国家科技重大专项(2018ZX07109-004-1)。
关键词
再生水
土壤含水层处理
三氮
吸附
硝化作用
生物炭
渗透流速
reclaimed water
soil aquifer treatment
nitrogen
adsorption
nitrification
biochar
infiltration rate