**3. Results**

#### *3.1. Changes in Physicochemical Parameters of Treated Textile E*ffl*uent*

The graphs in Figures 2–4 represent the changes in the physicochemical parameters of the dye-enriched tap water treated by floating treatment wetlands. The floating wetlands had a positive impact and predominately reduced the pH, EC, TSS, TDS, COD, BOD and color within the retention period of 20 days. All of the above-mentioned pollutants were reduced sharply in vegetated treatments (T2D1, T2D2, T2D3 and T3D1, T3D2, T3D3) as compared to non-vegetated treatments. However, the vegetated treatments inoculated with bacterial consortium (T3D1, T3D2, T3D3) achieved highest pollutants removal rate, outperforming all other treatments in all three types of dyes.

In the treatment containing dye 1, *P. australis* and bacterial consortium (T3D1), maximum pollutants removal e fficiency was achieved. In this treatment, pH was reduced to 6.7 from 8.5, EC was reduced from 6.13 to 1.00 mS cm<sup>−</sup>1, TDS was reduced from 400 to 60 mg <sup>L</sup>−1, TSS was reduced from 92 to 19 mg <sup>L</sup>−1, COD was reduced from 310 to 30 mg <sup>L</sup>−1, BOD was reduced from 121 to 20 mg L−<sup>1</sup> and color was reduced from 40.0 to 6.0 m<sup>−</sup>1.

Similarly, in the case of dye 2, maximum pollutant removal e fficiency was obtained from T3D2, in which pH was reduced to 6.8 from 8.5, EC was reduced from 6.13 to 1.02 mS cm<sup>−</sup>1, TDS was reduced from 400 to 63 mg <sup>L</sup>−1, TSS was reduced from 92 to 21 mg <sup>L</sup>−1, COD was reduced from 308 to 33 mg <sup>L</sup>−1, BOD was reduced from 121 to 18 mg L−<sup>1</sup> and color was reduced from 40.0 to 6.7 m<sup>−</sup>1.

As in the case of dye 1 and dye 2, the maximum pollutant removal rate was achieved by T3D3 containing dye 3, *P. australis* and bacterial consortium. In this treatment, pH was reduced to 6.7 from 8.5, EC was reduced from 6.15 to 1.05 mS cm<sup>−</sup>1, TDS was reduced from 401 to 62 mg <sup>L</sup>−1, TSS was reduced from 91 to 24 mg <sup>L</sup>−1, COD was reduced from 309 to 31 mg <sup>L</sup>−1, BOD was reduced from 120 to 19 mg L−<sup>1</sup> and color was reduced from 40.0 to 6.4 m<sup>−</sup>1.

**Figure 2.** Effect of floating treatment wetlands on pH (**A**), EC (**B**), TDS (**C**), TSS (**D**), COD (**E**), BOD (**F**) and color (**G**) after 20 days of retention time. D1: Bemaplex Navy Blue DRD. Each value is a mean of three replicates and error bars represent the standard deviation. Lettering shows that various treatments are significantly different at *p* ≤ 0.05.

**Figure 3.** Effect of floating treatment wetlands on pH (**A**), EC (**B**), TDS (**C**), TSS (**D**), COD (**E**), BOD (**F**) and color (**G**) after 20 days of retention time. D2: Bemaplex Rubine DB. Each value is a mean of three replicates and error bars represent the standard deviation. Lettering shows that various treatments are significantly different at *p* ≤ 0.05.

**Figure 4.** Effect of floating treatment wetlands on pH (**A**), EC (**B**), TDS (**C**), TSS (**D**), COD (**E**), BOD (**F**) and color (**G**) after 20 days of retention time. D3: Bemaplex Black DRKP Bezma. Each value is a mean of three replicates and error bars represent the standard deviation. Lettering shows that various treatments are significantly different at *p* ≤ 0.05.

#### *3.2. Removal of Heavy Metals from Water*

The concentration of six heavy metals (Cu, Fe, Mn, Ni, Zn and Pb) considerably reduced in the FTWs-treated water samples (Table 1). All vegetated treatments (T2 and T3) showed significantly better removal of trace metals from the dye-polluted water (D1, D2 and D3) as compared to the non-vegetated treatments (T1D1, T1D2 and T1D3). Next, the efficiency of bacterial augmented treatments (T3D1, T3D2 and T3D3) was significantly better than non-inoculated vegetated treatments (T2D1, T2D2 and T2D3). In treatment T3D1, the metal concentrations for Cu, Ni, Zn, Fe, Mn and Pb were reduced by up to 75%, 73.3%, 86.9%, 75%, 70% and 76.7%, respectively, in the 20 days retention time. Similar results were achieved for dye 2 and dye 3 in the case of treatment T3, in which bacterial inoculation efficiently removed the metals from dye water as compared to non-inoculated vegetated treatments (T2) and un-vegetated non-inoculated treatments (T1).


**Table 1.** Percentage (%) reduction in concentration of metals with time by floating treatment wetlands.

T symbolizes treatments (T1, T2, T3) and D symbolizes dye (D1: Bemaplex Navy Blue DRD, D2: Bemaplex Rubine DB, D3: Bemaplex Black DRKP Bezma). Values represent the means of three replicates and standard deviations are presented in parenthesis. Lettering shows that various treatments are significantly different at *p* ≤ 0.05.

#### *3.3. Bacterial Persistence in Roots, Shoots and Water*

The presence of a significantly high population of bacteria in water (Table 2), roots and shoots (Table 3) in the bacterial inoculated treatment (T3) as compared to non-inoculated treatments (T1 and T2) confirmed the persistence of inoculated bacteria during the treatment process in inoculated treatments for all three dyes. The bacteria showed the highest population in wastewater compared to roots and shoots. On the other hand, the count of bacteria was found higher in roots than shoots.


**Table 2.** Average concentration of bacteria in water (colony forming unit (CFU) mL−1).

Dye 1: Bemaplex Navy Blue DRD, Dye 2: Bemaplex Rubine DB, Dye 3: Bemaplex Black DRKP Bezma. Values represent the means of three replicates and standard deviations are presented in parenthesis. Lettering shows that various treatments are significantly different at *p* ≤ 0.05.

#### *3.4. Plant Growth in Response to Bacterial Inoculation*

It is well established that the presence of toxic pollutants in water inhibits plant growth and ultimately phytoremediation efficiency. The root and shoot length (Table 4) and root and shoot dry mass (Table 5) were noted at the end of the experiment and it was found that the plants grown in dye water inoculated with bacteria (T3) showed more growth as compared to the plants grown only in dye water. The plants grown in only tap water with no dye showed maximum growth out of all treatments. The dye water hindered the growth of plants and root and shoot length were reduced in case of all three dyes. Similarly, the plants grown in dye water inoculated with bacteria gained high shoot and root dry biomass due to good growth as compared to plants grown in dye water without bacterial inoculation. These results showed that despite the toxic effect of dyes, the inoculation of bacteria to dye water predominantly increased the length and dry weight of shoot and root of *P. australis*.


**Table 3.** Average concentration of bacteria in roots and shoots (CFU mL−1).

Dye 1: Bemaplex Navy Blue DRD, Dye 2: Bemaplex Rubine DB, Dye 3: Bemaplex Black DRKP Bezma. Values represent the means of three replicates and standard deviations are presented in parenthesis. Lettering shows that various treatments are significantly different at *p* ≤ 0.05.



Dye 1: Bemaplex Navy Blue DRD, Dye 2: Bemaplex Rubine DB, Dye 3: Bemaplex Black DRKP Bezma. Values represent the means of three replicates and standard deviations are presented in parenthesis. Lettering shows that various treatments are significantly different at *p* ≤ 0.05.


**Table 5.** Shoot and root dry weight of the plants.

Dye 1: Bemaplex Navy Blue DRD, Dye 2: Bemaplex Rubine DB, Dye 3: Bemaplex Black DRKP Bezma. Values represent the means of three replicates and standard deviations are presented in parenthesis. Lettering shows that various treatments are significantly different at *p* ≤ 0.05.
