Microalgae based wastewater treatment: a shifting paradigm for the developing nations.

Decreased water quality in freshwater resources due to untreated or partially treated wastewater disposal resulting in eutrophication has led to water scarcity. Hence, the present work was aimed to determine the effectiveness of Chlorella vulgaris for municipal wastewater treatment in terms of various physico-chemical parameters and nutrient removal. Primary treated effluent was collected from a sewage treatment plant as an influent for the study. Parameters analyzed during the lab-scale batch study of 7 hours of detention time were pH, EC, TDS, TSS, TS, COD, phosphate, ammonia, nitrate and DO. Removal efficiency reached 98.32, 97.26 and 84.71% for phosphate, ammonia and COD, respectively, for non-filtered effluents. However, filtered effluent removal efficiency reached 98.53, 98.63 and 89.41% for phosphate, ammonia and COD, respectively. The study revealed that microalgal treatment, if incorporated in conventional wasteater treatment, can be a solution to the limitations of the activated sludge process. It could be a promising technique for low income and developing countries, which could efficiently reduce the effluent concentration to much lesser than the desirable limits in an eco-friendly and cost-effective way. Statement of novelty Municipal wastewater treatment in most developing countries is confined to aerobic secondary treatments, which are costly and are not efficient in removing nutrients from the treated effluents before discharging and leading to the imbalance and eutrophication in the receiving bodies. Hence in this study, an attempt was made to study the effectiveness of Chlorella vulgaris for wastewater treatment at a detention time of 7 hours without any external aeration. The present study revealed that microalgae have efficiently removed organics and nutrients to much lesser than the desirable limit. Thus, if the Chlorella vulgaris is introduced in the wastewater treatment system can reduce the nutrients and organics concentrations without the need for aeration, which can be an energy-saving and cost-effective approach.

Sustainable treatment of domestic wastewater through microalgae.

The present work evaluated the optimum concentration of microalgal cells for domestic wastewater treatment in terms of removal in nutrients and physicochemical parameters. In the study, three different concentrations (20, 30, and 40%) of microalgae was considered at 8 hours and 24 hours of Hydraulic Retention time (HRT). Among the different microalgal concentrations studied 30% microalgae concentration gave maximum removal at both the HRTs. The maximum removal efficiency of phosphate, ammonia and COD for the non-filtered sample was 87.67, 96.88, and 80.39%, respectively, for filtered sample it was about 91.32, 100, and 83.64%, respectively at 8 hours HRT. However, at 24 hours HRT maximum removal efficiency observed was 97.92, 92.22, and 93.47% for ammonia, COD and phosphate respectively in case of non-filtered sample whereas in filtered samples maximum removal efficiency was 100, 94.44, and 95.51% for ammonia, COD and phosphate respectively. From the study, it was found that microalgae can effectively remove nutrients and organic contents to desirable limits even at a low HRT of 8 hours. At the urban sector, if microalgae are incorporated in a conventional wastewater treatment system will enhance the cost-effective efficiency by lowering the HRT and increasing the removal efficiency with footprints of sustainable treatment.