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The algal-bacterial process has received more attention in the present scenario as a new low-cost method towards pollutant removal from wastewater because symbiotic relationship between algae and bacteria is efficient when compared to traditional secondary treatments. The present work evaluated the optimum concentration of microalgal-bacterial consortia for significant reductions in physicochemical parameters of raw domestic wastewater. In the study, three different concentrations (20%, 30% and 40%) of microalgal-bacterial consortia were studied at 8 hours and 16 hours HRT. Among the different concentrations of consortia studied, 30% consortia gave maximum removal efficiency at both the HRTs. The maximum removal efficiency of phosphate, ammonia, BOD and COD was about 99.79%, 94.85%, 89.02% and 88.96%, respectively, at 8 hours HRT. However, at 16 hours, HRT maximum removal efficiency observed was 97.40%, 94.05%, 83.52% and 88.40% for phosphate, ammonia, BOD and COD respectively. The study depicts that microalgal-bacterial consortia can efficiently remediate nutrients and organic matter from domestic wastewater in both cases when sunlight was ample and even with minimal / no sunlight; hence this system can work effectively throughout the day with much lesser HRT and higher removal efficiency.

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Even after secondary treatment, wastewater has a high convergence of nutrients, which frequently causes eutrophication and different destructive impacts on biological systems. Wastewater treatment is a critical activity that must be considered necessary for the improvement of society. The secondary contamination of sludge formation and disposal also makes the treatment difficult. The vitality and financial amount required for tertiary treatment of wastewater remain an issue for local bodies, limiting its use for treatment. Hence, to address most of the challenges of sewage treatment, an algal-based system can be more affordable and biologically secure with the additional advantages of asset recuperation and reusing. Phycoremediation system even eliminates the need for tertiary treatment. The paper illustrates the benefits and challenges of phycoremediation, with some recent studies on microalgae as a wastewater treatment alternative along with the factors affecting the wastewater treatment through microalgae. The in-depth knowledge of the microalgal treatment in every aspect could result in an advancement to the conventional treatment process if applied in the field.

Conventional domestic wastewater treatment in most developing countries is confined to secondary treatments, mainly focusing on solids and organics removal, which results in eutrophication when the effluents are discharged into receiving bodies. Thus, to resolve the issues associated with the conventional treatment system, in the present study, microalgae was introduced in the primary treated effluent collected from a sewage treatment plant to study the efficiency of the system in reducing eutrophication and other challenges of secondary treatment. Phycoremediation is an effective and eco-friendly treatment alternative that reduced the primary-treated effluent’s PO4-P, NH3-N and COD concentration to 97.89%, 98.81%, and 88.24%, respectively at the identical HRT practiced for secondary treatment. One-way ANOVA was also conducted to determine the effectiveness of the system statistically. The experimental and statistical analysis proved that microalgal treatment could resolve the challenges of conventional secondary treatments if adopted for domestic wastewater.