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.

A review of the potential areas of algal biomass utilization has already been conducted. In addition to lowering the greenhouse effect and contributing to the decrease in the amounts of harmful substances in the air and water, attention has been paid to the possibility of utilizing algal biomass as a feedstock for the production of environmentally friendly products. The circular economy addresses the benefits to the environment, economy and society. The utilization of algal biomass benefits the environment by reducing greenhouse gases emissions as well as water and wastewater treatment, benefits the economy by producing biofuels, and benefits society by producing food, cosmetics, pharmaceuticals, fertilizers and feed for animals.

In this study, the responses of Dissolved Air Flotation (DAF), sedimentation, and sand filtration treatment processes on feed water with varied algal concentrations were investigated, based on a technical–economic analysis using data collected from a drinking water treatment plant (DWTP) in Guangxi, China. Cost-effective drinking water treatment processes for water sources with varied algae concentrations were proposed. The results showed that DAF was able to achieve almost 95% removal efficiency, while sedimentation was only able to reach 90% under different Polyaluminum Chloride (PACl)/dry cell weight concentrations in the DWTP. When algae concentrations increase, switching from sedimentation to DAF reduces treatment costs as DAF is more efficient for algae removal, which extends the backwashing interval of sand filtration. The threshold of sedimentation/DAF switching also depends on the quality requirement of the treated water. The lower the algae concentration in the treated water, the earlier the switch should be made from sedimentation to DAF. For instance, when the effluent thresholds are 1.2 mg·L⁻¹, 0.8 mg·L⁻¹, or 0.4 mg·L⁻¹, DAF should be adopted instead of sedimentation—at feed algae concentrations of 43.9 mg·L⁻¹, 31.5 mg·L⁻¹, and 17.3 mg·L⁻¹, respectively, in the raw water. The results set a baseline for a cost-effective drinking water treatment strategy based on a techno-economic model, which can precisely control the coagulation dosage and backwash interval of sand filtration coupled with sedimentation/DAF switching in algae-laden raw water.