Study on the control effect of electrokinetic drainage of pore water on nitrogen release flux at the mud-water interface

doi:10.11949/0438-1157.20221012

Abstract

Abstract:

Pore water is a crucial storage medium and a key source of sediment nitrogen. The separation and removal of nitrogen rich pore water is a potential scheme to control the release of endogenous nitrogen. A novel electrokinetic drainage of pore water device was used in a simulation study to understand its efficacy on internal nitrogen release. A total of three groups of experiments were set up: control, gravity drainage (0 V/cm voltage gradient) and intermittent energization (0.5 V/cm voltage gradient, 4 h On/4 h Off). In this research, we analyzed the characteristics of nitrogen concentration and release flux at the sediment-water interface, monitored the pore water and sediment nitrogen fraction, pH and other physicochemical parameters, and then assessed the effect of electrically induced and discharged pore water on the release flux of nitrogen at the sediment-water interface and the influencing factors. The results show that electrokinetic drainage of pore water can reduce the nitrogen release flux at the sediment-water interface effectively. The cumulative dissolved total nitrogen (DTN) release flux at the sediment-water interface was 282.28 mg N/m² after 632 h of intermittent energization, which was 95.61% lower than that in the control group. Electric drainage of pore water makes the anode pore water acidic and the cathode pore water alkaline, and the change of pH promotes the activation of transformable nitrogen (TTN) in the sediment. The removal rate of sludge ion-exchanged nitrogen (IEF-N) increased from 11.11%—12.97% to 12.59%—22.31%. After electric drainage of pore water, the total nitrogen removal amount of sediment is 47015.72 mg/m³, and the cumulative energy consumption is 162.38 kWh/m³.

Key words: electrokinetic remediation, electrochemistry, deposition, remediation, nitrogen release flux, pore water, nitrogen fraction

摘要：

孔隙水是底泥氮素污染的主要载体和释放源头，对富含氮素的孔隙水予以分离和脱除是控制内源氮释放的潜在方案。以富营养化湖泊底泥为研究对象，采用自制底泥孔隙水电动导排装置，在上覆水深度为20 cm的条件下进行底泥孔隙水电动导排，共设置对照、重力排水(0 V/cm电压梯度)和间歇通电(0.5 V/cm电压梯度，4 h On/4 h Off)3组实验，分析了泥-水界面氮浓度及释放通量的变化特征，监测了孔隙水及底泥中氮形态、pH等理化参数，评估了电动导排孔隙水对泥-水界面氮释放通量的控制效果及影响因素。结果表明：电动导排孔隙水可有效降低泥-水界面的氮释放通量，实验进行632 h后，通电实验组泥-水界面累计DTN释放通量为282.28 mg N/m²，与对照组相比氮释放通量削减95.61%。电动导排孔隙水使阳极孔隙水呈酸性，阴极孔隙水呈碱性，pH的改变促进了底泥中可转化态氮(TTN)的活化，与重力排水相比，电动导排孔隙水后底泥离子交换态氮(IEF-N)去除率由11.11%~12.97%提升至12.59%~22.31%。电动导排孔隙水后底泥总氮脱除量为47015.72 mg/m³，累计能耗为162.38 kWh/m³。

关键词: 电动导排, 电化学, 沉积物, 修复, 氮释放通量, 孔隙水, 氮形态

CLC Number:

X 506

Junjun GU, Rui LI, Xingyi WU, Xianqiang TANG, Yanping HU. Study on the control effect of electrokinetic drainage of pore water on nitrogen release flux at the mud-water interface[J]. CIESC Journal, 2022, 73(11): 5118-5127.

顾鋆鋆, 黎睿, 吴兴熠, 汤显强, 胡艳平. 电动导排孔隙水对泥-水界面氮释放通量的控制效果研究[J]. 化工学报, 2022, 73(11): 5118-5127.

Figures/Tables 12

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条件	通量范围/（mg N/m²）	释放速率范围/(mg N/(m²·h))	平均释放速率/（mg N/(m²·h)）	累计释放通量/（mg N/ m²）
对照	79.59~1332.03	2.13~26.53	9.15	6430.85
0 V/cm	-363.17~513.62	-5.04~13.48	2.08	1461.30
0.5 V/cm	-228.00~216.52	-9.50~6.81	0.45	282.28

条件	通量范围/（mg N/m²）	释放速率范围/(mg N/(m²·h))	平均释放速率/（mg N/(m²·h)）	累计释放通量/（mg N/ m²）
对照	79.59~1332.03	2.13~26.53	9.15	6430.85
0 V/cm	-363.17~513.62	-5.04~13.48	2.08	1461.30
0.5 V/cm	-228.00~216.52	-9.50~6.81	0.45	282.28

氮形态	去除率/%
	0 V/cm		0.5 V/cm
	中部	电极	阳极	中部	阴极
IEF-N	12.97	11.11	12.59	22.31	13.26
WAEF-N	-1.86	0.77	8.16	7.46	0.88
SAEF-N	6.92	7.08	3.89	-12.56	-35.28
SOEF-N	7.14	19.15	2.74	8.52	24.51

氮形态	去除率/%
	0 V/cm		0.5 V/cm
	中部	电极	阳极	中部	阴极
IEF-N	12.97	11.11	12.59	22.31	13.26
WAEF-N	-1.86	0.77	8.16	7.46	0.88
SAEF-N	6.92	7.08	3.89	-12.56	-35.28
SOEF-N	7.14	19.15	2.74	8.52	24.51

电压梯度/（V/cm）	位置	导排前有机质含量/%	导排后有机质含量/%
0	中部	9.03	8.29
0	电极	9.03	7.46
0.5	阳极	10.96	9.22
	中部	10.96	8.46
	阴极	10.96	7.48