Enhanced azo dyes decolorization in bioaugmented floating treatment wetlands using Typha domingensis and Bacillus sp

The present study evaluated bioaugmented floating treatment wetlands (FTWs) for the effective remediation of textile waste enriched with the azo dyes Synozol Red K3 BS (SR), Synozol Yellow K3 RS, and Synozol Ultra Black DR (SB). Six strains of bacteria (SZ1-SZ6) were isolated, characterized and tested for the ability to decolorize dyes. Of these, the SZ1 strain, Bacillus sp., was observed to have a maximum removal rate of 92% for SR, 89.96% for SY and 54% for SB dyes in shake flask assays. The performance of SZ1 was further optimized under different physicochemical conditions, pH (1, 3, 5, 7, 9, 11, and 13), incubation temperature (30-40°C), incubation days (1, 3, 5, and 7), and inoculum size (1, 2, 3, and 4%). The results indicated that optimum conditions for maximum decolorization were at pH 7, temperature 37°C and 2% inoculum size. SZ1 was then optimized and further introduced in FTWs vegetated with Typha domingensis. Bioaugmented FTWs (T. domingensis + Bacillus sp.) achieved significantly more dye removal up to 95% compared with FTWs with only plants or bacteria. Moreover, growth parameters (root and shoot length) were improved in bioaugmented systems indicating reduced toxicity. The results demonstrated that Bacillus Sp. and T. domingensis were complementary effective in the performance of FTWs to treat the dye-contaminated water, which provided an environmentally friendly FTW-based remediation solution as compared to the conventional one.