**Denitrification in the Presence of Chlorophenols: Progress and Prospects**

Emir Martínez‐Gutiérrez, Anne‐Claire Texier, Flor de María Cuervo‐López and Jorge Gómez

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.68860

#### Abstract

[26] Chen YX, Yin J, Wang KW. Long‐term operation of biofilters for biological removal of ammonia. Chemosphere. 2005;58:1023‐1030. DOI: 10.1016/j.chemosphere.2004.09.052.

[27] Sheridan B, Curran T, Dodd V, Colligan J. Biofiltration of odour and ammonia from a pig unit‐A pilot‐scale study. Biosystems Engineering. 2002;82:441‐453. DOI: 10.1006/

[28] Kim H, Xie Q, Kim YJ, Chung JS. Biofiltration of ammonia gas with sponge cubes coated with mixtures of activated carbon and zeolite. Environmental Technology. 2002;23:839‐

[29] Melse RW, Moi G. Odour and ammonia removal from pig house exhaust air using a

[30] Anthonisen AC, Loehr RC, Prakasam TBS, Srinath EG. Inhibition of nitrification by ammonia and nitrous‐acid. Journal Water Pollution Control Federation. 1976;48:835‐852.

[31] Kim NJ, Hirai M, Shoda M. Comparison of organic and inorganic packing materials in the removal of ammonia gas in biofilters. Journal of Hazardous Materials. 2000;B72:77‐

[32] Ottengraf SPP. Exhaust gas purification. In: Rehm HJ, Reed G, editors. Biotechnology.

[33] Kanagawa T, Qi HW, Okubo T, Tokura N. Biological treatment of ammonia gas at high

[34] Amann RI, Binder RJ, Olson S, Chisholm SW, Devereux R, Stahl DA. (1990) Combination of 16S ribosomal RNA targeted oligonucleotide probes with flow cytometry for ana‐ lyzing mixed microbial populations. Applied and Environmental Microbiology, 56, pp.

[35] Choi JH, Kim YH, Joo DJ, Choi SJ, Ha TW, Lee DH, Park IH, Jeong YS. (2003) Removal of ammonia by biofilters: A study with flow‐modified system and kinetics, Journal of the

[36] Gracian C, Malhautier L, Fanlo JL, Cloirec PLe. (2002) Biofiltration of air loaded with

[37] Lin C, Stahl DA. (1995) Comparative analyses reveal a highly conserved endoglucanase in the cellulolytic genus Fibrobacter. Journal of Bacteriology, 177, pp. 2543‐2549.

ammonia by granulated sludge. Environmental Progress, 21, pp.237‐245.

biotrickling filter. Water Science and Technology. 2004;50:275‐282.

1986. Vol. 8. Weinheim: VCH Verlagsgesellschaft. pp. 426‐452.

loading. Waster Science and Technology. 2004;50:283‐290.

Air & Waste Management Association,53, pp. 92‐101.

bioe.2002.0083.

74 Nitrification and Denitrification

DOI: 10.2307/25038971.

1919‐1925.

847. DOI: 10.1080/09593332308618355.

90. DOI: 10.1016/S0304‐3894(99)00160‐0.

Diverse industrial effluents may contain recalcitrant compounds such as chlorophenols. Besides, excessive use of pesticides in agriculture is a major cause of the appearance of chlorophenols in surface and groundwater. To mitigate and control the effects of chlorophenols in the environment, various methods have been developed for their elimination. Biological processes represent a sustainable and economical alternative that can lead to the mineralization of chlorophenols and be effective for the removal of these pollutants from different water bodies, such as rivers, groundwater, and wastewater. Some studies have reported that chlorophenols mineralization and nitrate reduction may simultaneously be performed. Other works have suggested that a reductive dechlorination occurs such as the first step and later, the phenol formed is subsequently mineralized by denitrification. However, the published information can be confusing as the denitrifying process is often associated with the sole nitrate consumption without corroborating the total reduction of nitrate to N2. Additionally, there are alternative systems that combine biological process with a chemical or electrochemical process for chlorophenols removal. This chapter focuses on the advances accomplished in the study of the removal of chlorophenols under denitrifying conditions with the aim of having a clearer panorama of the treatment alternatives that can be applied for treatment of this type of effluents.

Keywords: denitrification, chlorophenols, rates, anaerobic, combined systems

### 1. Introduction

Human activities generate effluents from production processes and domestic activities which may contain nitrogen and carbon pollutants. This pollution alters the global nitrogen and carbon cycles. Inorganic nitrogen is mainly present in the aqueous effluents such as nitrate, nitrite, and ammonium, causing serious problems to ecosystems and to public health.

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

These compounds can achieve high levels of toxicity to aquatic organisms and may promote the growth of aquatic plants, which accelerate the eutrophication process of water bodies [1]. The ingestion of nitrite and nitrate by infants can promote methemoglobinemia and the formation of nitrosamines, which might be carcinogens [2]. On the other hand, diverse industrial effluents may contain recalcitrant compounds such as chlorophenols, which are derivatives of phenol that contain one or more covalently bonded chlorine atoms. Chlorophenols have been utilized for wood preservation, as well as for manufacturing of pesticides, antiseptics, and dyes. However, the excessive use of pesticides in agriculture is one of the major causes of the appearance of chlorophenols in surface and groundwater [3]. Depending on their concentration, they can be toxic compounds, causing damage to the cell membranes as well as uncoupling oxidative phosphorylation [4].

To diminish the adverse effects of chlorophenols in the environment, various methods have been developed for their elimination, including physical, chemical, electrochemical, and biological processes. The first three methods appear to be faster, but everything indicates that they are expensive and generate collateral contamination, making them less environmentally friendly processes than the biological treatment. Biological processes represent a sustainable and costeffective alternative that can lead to the mineralization of chlorophenols and can be effective for the removal of these pollutants from different water bodies, such as rivers, groundwater, and wastewater. Most of the information on disposal of chlorophenols under anaerobic conditions has been obtained under methanogenic conditions. There is evidence that shows that removal of chlorophenols by methanogenic microbial consortia is initiated by a reductive dechlorination and ends with the formation of methane and CO2 [5], although more chlorinated chlorophenols are not always completely mineralized and less chlorinated compounds are obtained as end products [6]. Chlorophenol mineralization coupled to denitrification is still poorly documented. In this regard, there are few studies showing the possibility of chlorophenol consumption coupled to reduction of nitrate, although it is suggested that the pathway is different to reductive dechlorination [7]. Other studies suggested that reductive dechlorination occurs at first and later the phenol formed is subsequently mineralized by denitrification process [8]. However, the published information can be confusing, as the denitrifying process is often associated with the sole nitrate consumption without corroborating the total reduction of nitrate to N2.

Considering that efficient removal of recalcitrant compounds such as chlorophenols requires detailed analysis, this chapter focuses on the advances accomplished in the study of the removal of chlorophenols under denitrifying conditions. First, the physicochemical characteristics of the chlorophenols that confer their recalcitrant and toxic properties are presented. Then, general aspects of denitrification, such as microbiology and biochemistry, as well as the influence of various environmental factors, are presented. In physiological terms, the elimination of chlorophenols under denitrifying conditions is discussed, presenting the different configurations of reactors studied, types of inoculum, as well as the different strategies used to increase their consumption. Finally, the recently studied systems that combine the biological process with a chemical or electrochemical process, in order to increase the consumption of chlorophenols without the generation of toxic waste, are also presented.
