*2.2.2.1.1.6 Nitrate removal techniques*

There are a number of popular and conventional treatment methods available for reduction or removal of NO3ˉ in water bodies. In addition, several technologies are being investigated or proposed as denitrification methods. **Figure 4** presents an overview of some of the techniques used for NO3ˉ removal from water [23]. Reverse osmosis (RO) is considered as an ex situ and in situ application for the reduction of NO3ˉ from water. The efficiency of the process depends on the used pressure; this later should be sufficient to overcome the osmotic pressure [44]. According to Harries et al. [47], RO works well with NO3ˉ and NO2ˉ. Rejection of 96–98% was


**47**

*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention…*

found for monovalent ions, while 98–99% was found for divalent ions. In addition, ion exchange membranes (IEMs) have great potential in water denitrification. In fact, ion exchange is a reversible reaction between an electrolyte and a complex, where NO3ˉ and NO2ˉ, which have a negative ionic charge, will bind to the positively charged sites on the anion exchange beads of IEMs [44, 45]. For electrodialysis (ED), according to Mohsenipour et al. [46], the feed water supplied should have a turbidity that is lower than 2.0 nephelometric turbidity units. Furthermore, the concentration of free chlorine in water should be less than 0.5 mg/L, while these of hydrogen sulfide and manganese levels should be lower than 0.3 mg L. With electrodialysis systems about 70–85% of the water that is supplied to the system is

One of the common and promising purification methods is the biological treatment of wastewaters operated by denitrifying bacteria. The idea of using this process to remove NO3ˉ from drinking water has gained ground, especially in Europe [44]. Biological denitrification is mostly advised for the removal of relatively low concentration of N components. Furthermore, NO3ˉ are efficiently removed when an external organic carbon source, generally methanol, ethanol, or acetic acid, is added [48]. The rate of denitrification also depends on the type and concentration of carbon as well as carbon to nitrogen (C/N) ratio. The reduction of

Mohsenipour et al. [46] also reported the efficiency of NO3ˉ removal by a biological denitrification method using *Pseudomonas* bacteria and carbon source (starch of 1%) for initial NO3ˉ concentrations of 500 and 460 mg/L; the denitrification rates were respectively equal to 86 and 89% [49]. Furthermore, various conventional and nonconventional materials from different origins have been studied and conceived, as adsorbents, to limit the harmful effects of NO3ˉ [23]. Huang and Cheng [50] used powdered activated carbon (PAC) and carbon nanotubes (CNTs) for pollution reduction of NO3ˉ and demonstrated that the adsorption capacity of CNTs was found to be higher than PAC and decreased for pH higher than 5. Bamboo powder charcoal and nonactivated granular carbon (from coconut shells activated with zinc chloride) demonstrate good removal efficiency in NO3ˉ removal [51]. Natural adsorbents such as clay, zeolite, bentonite, and others were also studied [46, 52]. The effect of various variables such as pH, temperature, adsorbent dosage, other ions, and the amount of surfactant was tested on NO3ˉ removal, and it been demonstrated that except pH and temperature, the other variables are found to have a marked effect on NO3ˉ removal. It is should be noted that the removal of NO3ˉ has been conducted using modified and unmodified agricultural waste [74]. Mizuta [51] summarized the various sorbents which have been used so far

→ NO → N2O → N2 (3)

*DOI: http://dx.doi.org/10.5772/intechopen.86921*

**Figure 4.**

*Nitrate removal techniques.*

available for use as low NO3ˉ water [47].

NO3ˉ to nitrogen is done in four steps as shown in Eq. (3).

NO3 − → NO2 −

## **Table 2.**

*Summary of water quality guidelines for nitrogen.*

*Pollution of Water Sources from Agricultural and Industrial Effluents: Special Attention… DOI: http://dx.doi.org/10.5772/intechopen.86921*

**Figure 4.**

*Water Chemistry*

drinking water and in many surface waters. The USEPA [37] has set an enforceable standard called maximum contaminant level (MCL) in water for NO3ˉ at 10 parts per million (ppm) (10 mg/L) and for NO2ˉ at 1 ppm (1 mg/L), [59] and this is for all public water supplies. A summary of water quality guidelines for N-NO3ˉ, made by the USEPA, is reported in **Table 2** [39]. Furthermore, the intake limits for NO3ˉ in foods were set by the joint expert committee on food additives of the FAO/WHO and the European commission's scientific committee on food, at an acceptable daily intake for NO3ˉ of 0–3.7 mg (NO3ˉ)/kilogram (kg) body weight [40]. The same goes for Canada that set a MCL at 10 mg/L for NO3ˉ as N and 1 mg/L for NO3ˉ as N. For Morocco, the quality limits imposed by Order No. 1277-01 of 10 Shaaban 1423 (17 October 2002) setting quality standards for surface water used for the produc-

NO3ˉ ions can be detected through laboratory-based methods or in situ sensorbased methods. In general, they are two techniques for NO3ˉdetection, direct and indirect methods. While comparing the two methods, the major disadvantage of using a direct method is measurement errors due to interference from other contaminants [38, 42, 43]. Many methods are currently available to the laboratory technicians for the detection and analysis of NO3ˉ in a variety of sample matrices. The most commonly used techniques are (i) spectroscopic detection, (ii) electro-

There are a number of popular and conventional treatment methods available for reduction or removal of NO3ˉ in water bodies. In addition, several technologies are being investigated or proposed as denitrification methods. **Figure 4** presents an overview of some of the techniques used for NO3ˉ removal from water [23]. Reverse osmosis (RO) is considered as an ex situ and in situ application for the reduction of NO3ˉ from water. The efficiency of the process depends on the used pressure; this later should be sufficient to overcome the osmotic pressure [44]. According to Harries et al. [47], RO works well with NO3ˉ and NO2ˉ. Rejection of 96–98% was

**NO2ˉ mg/L as nitrogen**

32.8 (maximum) 0.06 (maximum) when the chloride is less than or

3.0 (30-d average) 0.02 (30-d average) when the chloride is less than

equal to 2

or equal to 2

3.7 (30-d average) None proposed

tion of drinking water, has also set a MCL at 50 mg/L for NO3ˉ [41].

chemical detection, and (iii) chromatography detection.

*2.2.2.1.1.5 Nitrate detection methods*

*2.2.2.1.1.6 Nitrate removal techniques*

**Water use NO3ˉ mg/L as** 

*Summary of water quality guidelines for nitrogen.*

Freshwater aquatic life—acute

Freshwater aquatic life—chronic

Marine aquatic life—chronic

**nitrogen**

Drinking water 10 (maximum) 1 (maximum)

Marine aquatic life—acute None proposed None proposed

Livestock watering 100 (maximum) 10 (maximum) Wildlife 100 (maximum) 10 (maximum) Recreation and esthetics 10 (maximum) 1 (maximum)

**46**

**Table 2.**

*Nitrate removal techniques.*

found for monovalent ions, while 98–99% was found for divalent ions. In addition, ion exchange membranes (IEMs) have great potential in water denitrification. In fact, ion exchange is a reversible reaction between an electrolyte and a complex, where NO3ˉ and NO2ˉ, which have a negative ionic charge, will bind to the positively charged sites on the anion exchange beads of IEMs [44, 45]. For electrodialysis (ED), according to Mohsenipour et al. [46], the feed water supplied should have a turbidity that is lower than 2.0 nephelometric turbidity units. Furthermore, the concentration of free chlorine in water should be less than 0.5 mg/L, while these of hydrogen sulfide and manganese levels should be lower than 0.3 mg L. With electrodialysis systems about 70–85% of the water that is supplied to the system is available for use as low NO3ˉ water [47].

One of the common and promising purification methods is the biological treatment of wastewaters operated by denitrifying bacteria. The idea of using this process to remove NO3ˉ from drinking water has gained ground, especially in Europe [44]. Biological denitrification is mostly advised for the removal of relatively low concentration of N components. Furthermore, NO3ˉ are efficiently removed when an external organic carbon source, generally methanol, ethanol, or acetic acid, is added [48]. The rate of denitrification also depends on the type and concentration of carbon as well as carbon to nitrogen (C/N) ratio. The reduction of NO3ˉ to nitrogen is done in four steps as shown in Eq. (3).

$$\rm NO\_3^- \rightarrow \rm NO\_2^- \rightarrow \rm NO \rightarrow \rm N\_2O \rightarrow \rm N\_2 \tag{3}$$

Mohsenipour et al. [46] also reported the efficiency of NO3ˉ removal by a biological denitrification method using *Pseudomonas* bacteria and carbon source (starch of 1%) for initial NO3ˉ concentrations of 500 and 460 mg/L; the denitrification rates were respectively equal to 86 and 89% [49]. Furthermore, various conventional and nonconventional materials from different origins have been studied and conceived, as adsorbents, to limit the harmful effects of NO3ˉ [23]. Huang and Cheng [50] used powdered activated carbon (PAC) and carbon nanotubes (CNTs) for pollution reduction of NO3ˉ and demonstrated that the adsorption capacity of CNTs was found to be higher than PAC and decreased for pH higher than 5. Bamboo powder charcoal and nonactivated granular carbon (from coconut shells activated with zinc chloride) demonstrate good removal efficiency in NO3ˉ removal [51]. Natural adsorbents such as clay, zeolite, bentonite, and others were also studied [46, 52]. The effect of various variables such as pH, temperature, adsorbent dosage, other ions, and the amount of surfactant was tested on NO3ˉ removal, and it been demonstrated that except pH and temperature, the other variables are found to have a marked effect on NO3ˉ removal. It is should be noted that the removal of NO3ˉ has been conducted using modified and unmodified agricultural waste [74]. Mizuta [51] summarized the various sorbents which have been used so far

for the elimination of NO3ˉ and demonstrated that hydrotalcite-type compounds/ layered double hydroxides and chemically modified adsorbents are found promising sorbents for enhanced removal of NO3ˉ from water. Tyagi et al. [53] made a summary of relevant published data with some of the latest important findings on the use of nanomaterials as NO3ˉ adsorbents. These nanoparticles can be metallic, semiconductor, or polymeric. **Table 3** reports some of the different nanomaterials used for NO3ˉ removal along with their experimental working parameters such as pH, adsorbent dose, initial NO3ˉ concentration, and temperature.
