Bio-treatment of wastewater using mixed algal cultures

Abstract

This study was carried out to evaluate the efficiency of mixed algal cultures for wastewater treatment. Free and alginate-immobilized forms of mixed algal culture were used. The highest removal percentages of biological oxygen demand (BOD) were 86.4% and 71.2 % after 32hrs and 48 hrs. in case of free and immobilized cells, respectively. Moreover, the highest values of chemical oxygen demand (COD) removal were 83.74% and 59.71% after 32hrs and 48 hrs for free and immobilized cells, respectively. Treatment with free cells showed removal values for total dissolved salts (TDS), phosphorus and NH3-N were 20.5%, 34.6% and 43.8% respectively after 32 hours. While in case of immobilized cells the highest removal values 18.4%, 34% and 58.5%, for TDS, Phosphorus and NH3-N, respectively were recorded after 48 hrs. Generally, concentration of heavy metals decreased due to treatment with algal free and immobilized cells. As a result of treatment with algal free and immobilized cells, 100% and 95.9% of Cu wastewater content was removed after 8 hrs and 48 hrs, respectively. Moreover, 96.2% and 98.1% of Fe was removed after 32 and 48 hours due to application of free and immobilized cells, respectively. As a result of inoculation with the mixed algal cultures in free cells 99.4% of Mn and 84.2% of Zn content were removed after 32 hours. Whereas, 98.6% of Pb content was removed after only 8 hrs. In case of using the immobilized cells the highest removal percentages of the three heavy metals recorded after 48 hours as follow 97.8% of Mn, 89.0% of Pb and 97.37% of Zn. Accordingly, treatment of wastewater with mixed algal free or immobilized cells is a fruitful method to produce an effluent of high quality to be used for irrigation. Whereas, the algal free cells were found to be more efficient than the immobilized ones.