Abstract
The present study evaluated the performance of microalgae Chlorella vulgaris in an Enterobacter sp. MN17-assisted textile industry wastewater treatment system for decolorization, removal of heavy metals (Cu, Cr, Pb, and Cd), and chemical oxygen demand (COD). Different dilutions (5, 10, and 20%) of wastewater were prepared to decrease the pollutant toxicity for culturing microalgae and bacteria. Reduction of color, COD, and metal contents by microalgal treatment of wastewater varied greatly, while removal efficiency (RE) was significantly enhanced when endophytic bacterial strain MN17 inoculum was applied. Most notable, results were found at a 5% dilution level by Enterobacter sp. MN17-inoculated C. vulgaris medium, as chromium (Cr), cadmium (Cd), copper (Cu), and lead (Pb) concentrations were decreased from 1.32 to 0.27 mg L−1 (79% decrease), 0.79–0.14 mg L−1 (93% decrease), 1.33–0.36 mg L−1 (72% decrease), and 1.2–0.25 mg L−1 (79% decrease), respectively. The values of COD and color were also significantly decreased by 74% and 70%, respectively, by a C. vulgaris–Enterobacter sp. MN17 consortium. The present investigation revealed that bacterial inoculation of microalgae significantly enhanced the removal of coloring agents and heavy metals from textile wastewater by stimulating the growth of algal biomass. This study manifested the usefulness of microalgae–bacterial mutualism for the remediation of heavy metals, COD, and color in industrial effluents. Microalgae consortia with growth promoting bacteria could be a breakthrough for better bioremediation and bioprocess economy. Thus, further studies are needed for successful integration of microalgae–plant growth promoting bacterial (PGPB) consortium for wastewater treatments.
Highlights
The textile industry is the most important sector in Pakistan’s economy, contributing about 9%to gross domestic product (GDP), but its impact on the environment is getting worse day by day.Recently, it has become a common practice to discharge wastewater originating from various production processes of textile and dying industrial units directly into water channels
The growth of C. vulgaris reached its maximum level after day 4 and levelled off, whereas for the consortium, the C. vulgaris response was much better even after 96 h
Growth on the first day was the the same for both cases but on the second day showed the highest difference, which might be the result same for both cases but on the second day showed the highest difference, which might be the result of more CO2 incorporation to the biomass, which further increased nutrient uptake (Figure 1)
Summary
It has become a common practice to discharge wastewater originating from various production processes of textile and dying industrial units directly into water channels. This indiscriminate discharge of industrial effluents is posing serious threats to human and animal health [1]. 3840 m3 /day of water is used in these processes of the textile industry [2]. These activities are held responsible for environmental water pollution due to the use of huge amounts of water throughout all the processing operations and release about 35 billion tons of wastewater with high values of pH, electrical conductivity (EC), and total suspended solids (TSS) [3]. More than 70 types of chemicals are present in textile effluents including 30 chemical types that are unable to be removed [4]
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