248

Bioremediation for Sustainable Environmental Cleanup

Table 14.4. Wastewater generation standard for Textile industries (mg L^–1).

Textile

industries

pH

Suspended

Solids

BOD3

Oil and

Grease

Bio-assay

Cr

Sulfide

Phenol

References

Cotton

Textile

Industry

5.5–9.0

100

150

10

90% survival of

fish after 96 hr in

100% effluent

_

_

_

CPCB 2000

Composite

Woolen Mill

5.5–9.0

100

100

10

90% survival of

fish after 96 hr in

100% effluent

2

2

5

CPCB 2000

14.6 Application of WH in Phytoremediation of Industrial Wastewater

14.6.1 Removal of Heavy Metals from Industrial Wastewater

WH is one of the common phytoremediation plants in India, has a strong capacity for heavy metal

accumulation (Bioaccumulation factor > 10,000 times), which leads to the removal of organic and

inorganic pollutants from water and wastewater (Yan and Guo 2017). It removes pollutants using

physical or biological treatment or a combination. WH is known for absorbing suspended solids

during the physical treatment process using precipitation and absorption processes. Metals and other

pollutants bound with the suspended solids are then co-precipitated (Huang and Xu 2008). The hairy

fibrous root system of the plant supports the accumulation of suspended solids, microorganisms,

colloids and protozoa (Zhou et al. 2005, Nawirska 2005). The absorbed pollutants are transferred

to the leaves and stems after accumulation by the roots, and roots protect the plant by accumulating

large amounts in the root and transfer a small number of pollutants to the leaves and stems (Cai

et al. 2004). Heavy metals are accumulated by the WH in the apoplast (Cell Wall) and then transferred

across the plasma membrane. The root walls of WH play an important role by blocking the pollutant

uptake with the help of pectin substances such as polygalacturonic acid and cellulose molecules.

This cellulose or polygalacturonic acid molecule contains carboxyl and aldehyde groups which help

exchange sites for pollutants like heavy metals by chelation. In this chelation process, amino- and/

or oxygen-containing functional groups play a key role in removing heavy metals from wastewater

(Zhang 2011). Among tolerance mechanisms, chelation in the cytosol attracts considerable attention:

heavy metal stress could induce the formation of biomacromolecules that form chelates with heavy

metal ions, thus lowering the activity of free heavy metal ions in plant cells and relieving the toxicity

(Yan and Guo 2017). Two metal binding peptides, i.e., metallothionein and phytochelatins, are

available in the phytoremediation plant cells; among them, metallothionein has the low-molecular­

weight polypeptide containing cysteine which helps in the formation of a non-toxic or low-toxic

complex with the combination of thiol (–SH) group (Margoshes and Vallee 1957).

A case study by Mokhtar et al. (2011) reported the removal of heavy metals in the textile

industry using WH, where 97.3% of Cu accumulation was reported. Similarly, the 5-wk study on

textile wastewater resulted in 94.87% removal of cadmium from the textile industry using WH

(Ajayi and Ogunbayo 2012). Seventy to ninety percent removals of heavy metals like Fe, Pb, Cu and

Cr have been observed in the study of Kolawole (2001). Another study by Mahmood et al. (2005)

on textile wastewater observed 86, 88 and 83% removal of Cr, Zn and Cu, respectively. Apart from

that more than 10% removal of methylene blue dye from textile wastewater has been observed in

the study of Nibret et al. (2019). Water hyacinth can also remove more than 60% Mn and Pb from

paper and pulp effluent (Kumar et al. 2016) and Na, K, Ca, Mg, Cd, Cr, Cu, Fe.