**Author details**

*M. aquaeolei* sp. *nov*. was found to grow under anoxic conditions in the presence of nitrate on succinate, citrate, or acetate, but not on glucose. It was also interesting that *H. campisalis* sp. *nov*.

**Table 3** summarizes the species capable of denitrifying under saline conditions. Most of the species were in the class of *γ-proteobacteria*. Species were found to even survive in a wide

Extensive research was conducted in the past for denitrifiers in treating municipal wastewater which typically contains TDS less than 1000 mg/L. Whether the knowledge acquired in regard to the stoichiometry, kinetics, metabolic pathways, and microbial communities and character-

Through the above short review, it was suggested that specific denitrification rates of mixed cultures decreased with an increasing salinity concentration. However, some specific species such as *H. campisalis* sp. *nov*. exhibited relatively high denitrification rates at 12.5% salinity with different carbon sources, similar to that of its freshwater counterparts. If biomass is properly acclimated and adapted to saline environments, the SDNR could be comparable to that

**Class Genus Species Salinity range Optimal salinity Reference** *γ-Proteobacteria Halomonas campisalis* sp. *Nov*. 1.17–26.3 % (w/v) 8.8% (w/v) [16]

*Halomonas chromatireducens*

*Marinobacter PAD-2 (closely* 

*Pseudomonas pantotrophus and* 

*β-Proteobacteria Azoarcus Azoarcus*-like

**Table 3.** Summary of halophilic denitrifying species.

sp. *nov*.

*related to M. alkaliphilus)*

*fluorescens*

species

*Halomonas daqingensis* sp. *nov*. 1.0–15.0% (w/v) 5–10% (w/v) [19] *Halomonas ventosae* sp. *nov*. 1.0–15.0 % (w/v) 8% (w/v) [20]

*Halomonas desiderata* sp. *nov*. 0–18% (w/w) [22] *Marinobacter aquaeolei sp. nov*. 0–20% (w/w) 5% (w/w) [23]

*Pseudomonas stutzeri* 1–4% (w/v) [8]

Cl−

Up to 3.5% (w/v)

 and 1.7% (w/v) SO4 2−

0.585–23.4% (w/v)

2.9% (w/v) [21]

[15]

3–18% (w/w) 3–6% (w/v) [9]

1.09% (w/v) Cl− [6]

istics is transferrable to halophilic counterparts is subject to further research.

grew on acetate, lactate, glycerol, and ethanol but not on methanol [16].

range of salinity as high as 23.4%.

6 Nitrification and Denitrification

at low-salinity concentrations.

**5. Summary and future perspective**

Ivan X. Zhu1 \* and Jian R. Liu2

\*Address all correspondence to: ivan.zhu@evoqua.com


## **References**

