Wastewater generated from the textile industry contains numerous pollutants, most notably dyes, which can cause adverse effects, including negative impact on aesthetics, eutrophication, decrease of photosynthetic activity and bioaccumulation of toxins in aquatic ecosystems, if discharged without adequate treatment. The cultivation of microalgae in the textile dye effluent has been identified as a promising alternative to conventional methods of wastewater treatment. During microalgae cultivation, dyes present in effluent are remediated through bioconversion/biodegradation or biosorption. Thus, treatment using microalgae reduces the color and nutrient load of textile effluent, which mitigates numerous negative environmental impacts caused by its discharge into the natural environment. Furthermore, compared to conventional treatment processes, use of microalgae for bioremediation of textile effluent provides the added advantage of generating valuable biomass that can be processed into bioproducts, biofuels and bioenergy. Wastewater-integrated cultivation would enhance the sustainability of microalgal biomass production by reducing the freshwater footprint and recovery of waste nutrients from effluent, thereby promoting the concept of a biobased economy. In this mini-review, the current status and future perspectives of using microalgae for bioremediation of textile dye wastewater were analyzed, with focus on various strategies reported in the literature. A critical review of the literature showed that most studies focused on wastewater treatment, while exploring applications for concomitantly generated biomass was a secondary consideration. Hence, the requirement of a paradigm shift in current research for valorization of microalgal biomass was highlighted. Moreover, it was concluded that comprehensive feasibility studies are necessary prior to industrial-scale bioremediation of textile dye effluent.

Large-scale cultivation of microalgae for the production of high-value compounds raises concerns on sustainability due to intense consumption of water resources. Use of wastewater for microalgae cultivation is considered a promising alternative, because it not only reduces water consumption, but also provides nutrients required for microalgae growth. In the present study, Haematococcus pluvialis and Chromochloris zofingiensis were cultivated in synthetic dairy wastewater (DWW) to identify the potential of developing highvalue product first biorefineries, with astaxanthin as the main product.H. pluvialis and C. zofingiensis cultivated in DWW achieved biomass concentrations of 0.55 ± 0.01 and 0.65 ± 0.01 g/L, respectively. Astaxanthin contents of 2.1 ± 0.1% and 0.4 ± 0.1% were observed in H. pluvialis and C. zofingiensis grown in DWW. Minimum freshwater consumption for cultivation was 69.93 L/g astaxanthin in control growth media, which could be eliminated by cultivation of microalgae in DWW. COD, TN, and TP removal efficiencies were in the range of 94%-96%, 79%-81%, and 57%-79%, respectively, indicating capability for simultaneous biomass production and phycoremediation. Presence of carbohydrates and lipids in residual biomass suggested the applicability as feedstock for biorefining. Potential avenues to integrate wastewater treatment, astaxanthin production, and valorization of residual biomass were discussed in context of high-value product first biorefineries.