Effect of external electric current on denitrification efficiency and sludge flocculation of anoxic zone using AO process

doi:10.16085/j.issn.1000-6613.2020-2269

Abstract

Abstract:

Biological nitrogen removal could be achieved using nitration liquid internal circulation in AO process, which was difficult to ensure the anoxic condition of anoxic zone and thus led to unsatisfactory nitrogen removal and poor sludge flocculation. In order to enhance biological nitrogen removal, external electric current was used to enhance the sludge activity and bioflocculation in the anoxic zone. The changes of sludge contact angle, zeta potential and particle size were explored and the composition of extracellular polymeric substances (EPS) was analyzed using three-dimensional excitation emission matrix fluorescence spectroscopy (3D-EEM) and Fourier transform infrared spectroscopy (FTIR) under different current intensities. The effects of external electric current on the pollutants removal and sludge properties were investigated. The results showed that removal efficiencies of TN and COD and enzyme activity increased with the increase of the current intensity when the current intensity was lower than 30mA. When current intensity was 30mA, ORP was -135mV, and nitrate reductase activity and removal efficiency of TN were the highest [0.37μg/(mg·min) and 79.43%]. When current intensity was 40mA, dehydrogenase activity and removal efficiency of COD were the highest [50.86mg/(L·h) and 80.65%]. When current intensity was lower than 40mA, the ratio of protein (PN)/polysaccharide (PS), contact angle and average particle size of sludge increased and zeta potential of sludge decreased with the increase of current intensity, which was beneficial to sludge flocculation. Fluorescence intensity of tryptophan and tyrosine was improved and there were no obvious changes in functional groups of EPS based on the analysis of 3D-EEM and FTIR. When the current intensity was 40mA, the bioflocculation of sludge was the optimum and flocculation ability (FA) was 40.33%. Effluent suspend solid (ESS) was 13.95mg/L and sludge volume index (SVI) was 66.5mL/g. When current intensity was higher than 40mA, sludge flocculation gradually deteriorated with the increase of current intensity. Therefore, the efficiency of biological denitrification and the sludge flocculability could be improved when the current intensity was controlled at 40mA.

Key words: electric current, wastewater, bioreactors, denitrification, enzyme, extracellular polymeric substances, flocculation

摘要：

AO工艺利用硝化液内循环实现生物脱氮，很难保证缺氧区的缺氧条件，导致脱氮效果不理想，污泥絮凝性差。为了达到强化生物脱氮的目的，本研究采用外加电流提高缺氧区的污泥活性和生物絮凝性，探索不同电流强度下污泥接触角、zeta电位和污泥粒径的变化，结合三维荧光光谱（3D-EEM）与傅里叶变换红外光谱（FTIR）分析胞外聚合物（EPS）的组成，考察外加电流对污染物去除和污泥性质的影响。结果表明：当电流强度低于30mA时，随着电流强度的增加，TN和COD去除率提高，酶活性增强。当电流强度为30mA时，ORP为-135mV，硝酸盐还原酶活性达到最强[0.37μg/（mg·min）]，TN去除率达到最高79.43%；当电流强度为40mA时，脱氢酶活性达到最强[50.86mg/（L·h）]，COD去除率达到最高80.65%。当电流强度低于40mA时，随着电流强度的提高，蛋白质（PN）与多糖（PS）的比值增加，污泥接触角增大，zeta电位减小，平均粒径升高，污泥絮凝性增强；由3D-EEM和FTIR分析可知，色氨酸和酪氨酸类的荧光强度增强，EPS的官能团无明显变化。当电流强度为40mA时，污泥重絮凝能力（FA）为40.33%，出水悬浮物（ESS）为13.95mg/L，污泥容积指数（SVI）为66.5mL/g，污泥絮凝性最好。随着电流强度的继续提高，污泥絮凝性逐渐变差。因此，将电流强度控制在40mA，可以同时实现提高生物脱氮效率和污泥絮凝性的目的。

关键词: 电流, 废水, 生物反应器, 反硝化脱氮, 酶, 胞外聚合物, 絮凝性

CLC Number:

X703

ZHANG Lanhe, YUAN Zhentao, ZHAO Haojie, ZHAO Juntian, ZHU Yining, CHEN Zicheng, JIA Yanping, TIAN Shulei. Effect of external electric current on denitrification efficiency and sludge flocculation of anoxic zone using AO process[J]. Chemical Industry and Engineering Progress, 2021, 40(11): 6369-6377.

张兰河, 袁镇涛, 赵浩杰, 赵君田, 祝艺宁, 陈子成, 贾艳萍, 田书磊. 外加电流对AO工艺缺氧区脱氮效率与污泥絮凝的影响[J]. 化工进展, 2021, 40(11): 6369-6377.

Figures/Tables 8

COD /mg·L^-1	TN /mg·L^-1	TP /mg·L^-1	c(NH $_{4}^{+}$ -N) /mg·L^-1	c(PO $_{4}^{3 -}$ -P) /mg·L^-1	T/℃
480±20	71±3	7±1	60±5	6.5±1	20±5

COD /mg·L^-1	TN /mg·L^-1	TP /mg·L^-1	c(NH $_{4}^{+}$ -N) /mg·L^-1	c(PO $_{4}^{3 -}$ -P) /mg·L^-1	T/℃
480±20	71±3	7±1	60±5	6.5±1	20±5

References 32

1	张兰河, 王旭明, 邱晓春. 序批式生物反应器脱氮除磷理论与工艺[M]. 北京: 科学出版社, 2014: 1-2.
	ZHANG Lanhe, WANG Xuming, QIU Xiaochun. Theory and process of nitrogen and phosphorus removal using sequencing batch reactor[M]. Beijing: Science Press, 2014: 1-2.
2	王文明, 危建新, 刘耘东, 等. 日本污水脱氮除磷深度处理工艺分析[J]. 环境工程学报, 2015, 9(3): 1194-1200.
	WANG Wenming, WEI Jianxin, LIU Yundong, et al. Analysis on sewage advanced treatment process for nitrogen and phosphorus removal in Japan[J]. Chinese Journal of Environmental Engineering, 2015, 9(3): 1194-1200.
3	JIANG X, YING D W, YE D, et al. Electrochemical study of enhanced nitrate removal in wastewater treatment using biofilm electrode[J]. Bioresource Technology, 2018, 252: 134-142.
4	HAO R X, LI S M, LI J B, et al. Denitrification of simulated municipal wastewater treatment plant effluent using a three-dimensional biofilm-electrode reactor: operating performance and bacterial community[J]. Bioresource Technology, 2013, 143: 178-186.
5	HE Y, WANG Y H, SONG X S. High-effective denitrification of low C/N wastewater by combined constructed wetland and biofilm-electrode reactor (CW-BER)[J]. Bioresource Technology, 2016, 203: 245-251.
6	徐忠强, 郝瑞霞, 任晓克, 等. 包埋法固定化细胞技术用于三维电极生物膜反应器[J]. 中国给水排水, 2018, 34(19): 37-42.
	XU Zhongqiang, HAO Ruixia, REN Xiaoke, et al. Application of entrapping method in three-dimensional biofilm-electrode reactor for advanced nitrogen removal[J]. China Water & Wastewater, 2018, 34(19): 37-42.
7	ZHANG L H, JIA J P, YING D W, et al. Electrochemical effect on denitrification in different microenvironments around anodes and cathodes[J]. Research in Microbiology, 2005, 156(1): 88-92.
8	SURESH A, GRYGOLOWICZ-PAWLAK E, PATHAK S, et al. Understanding and optimization of the flocculation process in biological wastewater treatment processes: a review[J]. Chemosphere, 2018, 210: 401-416.
9	ZHANG W J, CAO B D, WANG D S, et al. Influence of wastewater sludge treatment using combined peroxyacetic acid oxidation and inorganic coagulants re-flocculation on characteristics of extracellular polymeric substances (EPS)[J]. Water Research, 2016, 88: 728-739.
10	宋悦, 魏亮亮, 赵庆良, 等. 活性污泥胞外聚合物的组成与结构特点及环境行为[J]. 环境保护科学, 2017, 43(2): 35-40.
	SONG Yue, WEI Liangliang, ZHAO Qingliang, et al. Chemical structure and environmental behavior of extracellular polymeric substances in sludge: a review[J]. Environmental Protection Science, 2017, 43(2): 35-40.
11	LIU X M, SHENG G P, LUO H W, et al. Contribution of extracellular polymeric substances (EPS) to the sludge aggregation[J]. Environmental Science & Technology, 2010, 44(11): 4355-4360.
12	YU G H, HE P J, SHAO L M. Characteristics of extracellular polymeric substances (EPS) fractions from excess sludges and their effects on bioflocculability[J]. Bioresource Technology, 2009, 100(13): 3193-3198.
13	BASUVARAJ M, FEIN J, LISS S N. Protein and polysaccharide content of tightly and loosely bound extracellular polymeric substances and the development of a granular activated sludge floc[J]. Water Research, 2015, 82: 104-117.
14	CAO B D, ZHANG W J, DU Y J, et al. Compartmentalization of extracellular polymeric substances (EPS) solubilization and cake microstructure in relation to wastewater sludge dewatering behavior assisted by horizontal electric field: effect of operating conditions[J]. Water Research, 2018, 130: 363-375.
15	SHI S N, XU J, ZENG Q Z, et al. Impacts of applied voltage on EMBR treating phenol wastewater: performance and membrane antifouling mechanism[J]. Bioresource Technology, 2019, 282: 56-62.
16	魏民, 郑国臣, 李建政, 等. 表征水体中生物活性及脱氢酶检测方法研究[J]. 东北水利水电, 2012, 30(8): 43-46, 72.
	WEI Min, ZHENG Guochen, LI Jianzheng, et al. Study on detection method of biological activity and dehydrogenase in water[J]. Water Resources & Hydropower of Northeast China, 2012, 30(8): 43-46, 72.
17	LI S S, MA B R, ZHAO C K, et al. Long-term effect of different Cu(Ⅱ) concentrations on the performance, microbial enzymatic activity and microbial community of sequencing batch reactor[J]. Environmental Pollution, 2019, 255: 113216.
18	何志江, 赵媛, 张源凯, 等. 活性污泥表面性质对絮凝沉降性能与出水悬浮物的影响[J]. 环境科学, 2016, 37(8): 3135-3143.
	HE Zhijiang, ZHAO Yuan, ZHANG Yuankai, et al. Influence of activated sludge surface properties on flocculating settling and effluent suspend solid[J]. Environmental Science, 2016, 37(8): 3135-3143.
19	张兰河, 张明爽, 郭静波, 等. Fe³⁺在A²O工艺缺氧区的转化规律及其对污泥絮凝性的影响[J]. 化工学报, 2019, 70(3): 1089-1098.
	ZHANG Lanhe, ZHANG Mingshuang, GUO Jingbo, et al. Transformation of Fe³⁺ and its effect on anoxic sludge flocculation in A²O process[J]. CIESC Journal, 2019, 70(3): 1089-1098.
20	张兰河, 赵倩男, 张海丰, 等. Ca²⁺对污泥硝化活性和絮凝沉降性能的影响[J]. 环境科学, 2019, 40(9): 4160-4168.
	ZHANG Lanhe, ZHAO Qiannan, ZHANG Haifeng, et al. Effect of Ca²⁺ on the nitrification activity and the flocculation and sedimentation performances of the activated sludge[J]. Environmental Science, 2019, 40(9): 4160-4168.
21	WANG K, SHENG Y X, CAO H B, et al. Impact of applied current on sulfate-rich wastewater treatment and microbial biodiversity in the cathode chamber of microbial electrolysis cell (MEC) reactor[J]. Chemical Engineering Journal, 2017, 307: 150-158.
22	王晓玲, 宋铁红, 殷宝勇, 等. 利用主要缺氧段ORP作为连续流单污泥污水脱氮除磷系统调控参数[J]. 环境科学, 2015, 36(7): 2617-2625.
	WANG Xiaoling, SONG Tiehong, YIN Baoyong, et al. ORP in the main anoxic stage as the control parameter for nitrogen and phosphorus removal in the single sludge system with a continuous flow[J]. Environmental Science, 2015, 36(7): 2617-2625.
23	ZHANG L H, ZHAO Q N, ZHANG M S, et al. Mg²⁺ distribution in activated sludge and its effects on the nitrifying activity and the characteristics of extracellular polymeric substances and sludge flocs[J]. Process Biochemistry, 2020, 88: 120-128.
24	WANG Z C, GAO M C, WANG Z, et al. Effect of salinity on extracellular polymeric substances of activated sludge from an anoxicaerobic sequencing batch reactor[J]. Chemosphere, 2013, 93(11): 2789-2795.
25	李恕艳, 李吉进, 张邦喜, 等. 菌剂对鸡粪堆肥腐殖质含量品质的影响[J]. 农业工程学报, 2016, 32(S2): 268-274.
	LI Shuyan, LI Jijin, ZHANG Bangxi, et al. Influence of inoculants on content and quality of humus during chicken manure composting[J]. Transactions of the Chinese Society of Agricultural Engineering, 2016, 32(S2): 268-274.
26	ZHANG B, CHEN N, FENG C P, et al. Adsorption for phosphate by crosslinked/non-crosslinked-chitosan-Fe(‍Ⅲ) complex sorbents: characteristic and mechanism[J]. Chemical Engineering Journal, 2018, 353: 361-372.
27	ZHU L, QI H Y, LYU M L, et al. Component analysis of extracellular polymeric substances (EPS) during aerobic sludge granulation using FTIR and 3D-EEM technologies[J]. Bioresource Technology, 2012, 124: 455-459.
28	袁冬琴, 王毅力. 活性污泥胞外聚合物(EPS)的分层组分及其理化性质的变化特征研究[J]. 环境科学, 2012, 33(10): 3522-3528.
	YUAN Dongqin, WANG Yili. Study on the stratification components of extracellular polymeric substances (EPS) in activated sludge and their variation characteristics in physicochemical properties[J]. Environmental Science, 2012, 33(10): 3522-3528.
29	张兰河, 王佳平, 陈子成, 等. Ca²⁺对序批式生物反应器活性污泥性能的影响[J]. 化工进展, 2018, 37(9): 3675-3681.
	ZHANG Lanhe, WANG Jiaping, CHEN Zicheng, et al. Effect of Ca²⁺ on the properties of activated sludge in the SBR[J]. Chemical Industry and Engineering Progress, 2018, 37(9): 3675-3681.
30	SU B S, QU Z, SONG Y H, et al. Investigation of measurement methods and characterization of zeta potential for aerobic granular sludge[J]. Journal of Environmental Chemical Engineering, 2014, 2(2): 1142-1147.
31	LI Z L, LU P L, ZHANG D J, et al. Population balance modeling of activated sludge flocculation: investigating the influence of extracellular polymeric substances (EPS) content and zeta potential on flocculation dynamics[J]. Separation and Purification Technology, 2016, 162: 91-100.
32	阮晓东, 刘俊新. 活性污泥TB-EPS的絮凝特性研究: 絮体的成长、破碎与再凝聚[J]. 环境科学学报, 2013, 33(3): 655-663.
	RUAN Xiaodong, LIU Junxin. Flocculation characteristics of flocs formed by tightly bound extracellular polymeric substances(TB-EPS)—The formation, breakup and regrowth of flocs[J]. Acta Scientiae Circumstantiae, 2013, 33(3): 655-663.

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