**1. Introduction**

The major sources of water pollution are industries, domestic discharges, urbanization, pesticides, fertilizers, and poorly managed farm wastes [1,2]. The textile industry significantly contributes to the economy of a country. However, it consumes a large amount of water, and thus generates a larger quantity of wastewater [3]. Textile industry wastewater contains harmful dyes, di fferent pigments, oil, surfactants, heavy metals, sulphates, and chlorides [4]. All these pollutants unfavorably a ffect the quality of water and aquatic life.

Dyes are key constituents of textile e ffluent. Textile dyes are considered as one of the worst polluters of our environment, including water bodies and soils [5]. These dyes also have adverse effects on human health. The dyes in textile wastewaters are carcinogenic, mutagenic, and genotoxic for all life forms [6]. Dyes in wastewater hinder the sunlight reaching to water, and thus decrease photosynthetic activity, reduce transparency, and disturb the ecosystem [3,4]. Additionally, di fferent chemicals are used in the textile industry and cause problems for life forms, as well as the environment upon direct contact with them [7]. Existing wastewater treatment technologies are ine fficient for the removal of dyes and associated pollutants from wastewater because of their persistent nature and resistance to degradation [8].

Incompletely treated or untreated wateris harmful to the environment and otherliving creatures [9,10]. All types of wastewater should be treated before dumping into open water bodies in order to minimize the spread of water pollution [11]. Textile wastewater can be treated by various methods based upon physical, chemical, and biological approaches. However, the by-products of these treatment processes can be toxic and difficult to dispose of safely [6,12]. Consequently, it is essential to devise and adopt an environmentally friendly and sustainable technique to treat textile wastewater.

Phytoremediation, i.e., use of plants to remove pollutants, is one of the best economical and sustainable approaches for wastewater treatment [13,14]. Plants can take up contaminants from water, soil, and air [15]. Over the past years, di fferent plants have been used to remediate dyes from textile wastewater. Di fferent plants species have di fferent nutrients/pollutants removal potential, and could exhibit grea<sup>t</sup> phytoremediation and stress tolerance [15–17]. Along with the applications of plants, di fferent eco-friendly mechanisms are now being adopted to treat textile wastewater, and they include plant seeds [18], bacteria [8], fungi [19,20], yeas<sup>t</sup> [21,22], and microalgae [23]. Recently, helminths have also been used to degrade dyes, for example, the nematode *Ascans lumbncoides* and the cestode *Momezia expansa* have been found to reduce azo dyes by anaerobic methods [24,25].

Although dyes are resistant to degradation, many microorganisms can completely decolorize and mineralize them [26]. The application of bacteria is an e fficient way to treat dyes, as they are not harmful for the environment. Di fferent bacteria have a high ability to degrade di fferent dyes; for example, *Pseudomonas* sp. and *Sphingomonas* sp. have been found useful in the degradation of dyes [3]. The specifically adaptive bacteria can produce reductase enzymes that can reductively cut the dyes in the presence of molecular oxygen [27]. In the current scenario, we must seek e fficient, eco-friendly, and economical technologies to treat textile wastewater with a minimum generation of waste materials [3]. Application of plants and bacteria has become a sustainable approach for wastewater treatment [18].

#### **2. Potential Pollutants in Textile Wastewater**

Textile wastewater contains highly variable dyes that have structural varieties including basic, acidic, reactive, azo, metal complex, and diazo dyes [28]. Typical characteristics of textile e ffluents include high temperature, the extensive range of pH, chemical oxygen demand (COD), biological oxygen demand (BOD), heavy metals, and a variety of contaminants such as dyes, salts, surfactants, dissolved solids, and suspended solids (Table 1) [28–30].


**Table 1.** Characteristics of textile wastewater.

*Sustainability* **2020**, *12*, 5801


Total Nitrogen; TP: Total Phosphorus; TA: Total Alkalinity; TH: Total Hardness; TKN: Total Kjeldahl Nitrogen.

#### *Sustainability* **2020**, *12*, 5801
