Removal of Nutrients from Fertilizer Plant Wastewater Using <i>Scenedesmus</i> sp.: Formation of Bioflocculation and Enhancement of Removal Efficiency

Abstract

Eutrophication of surface water has become an environmental concern in recent decades. High concentrations of nutrients, especially nitrogen- and phosphorus-rich species, have contributed to the process of eutrophication, highlighting a demand for effective and economical methods of removing nitrogen and phosphorus from wastewater. This study aimed to investigate the ability of a green microalga species, Scenedesmus sp., to remove nitrogen and phosphorus, as well as chemical oxygen demand (COD) and biochemical oxygen demand (BOD 5 ), from fertilizer plant wastewater. Different microalgae concentrations from 10 mg/L to 60 mg/L were used to assess the growth rate, biomass production, and removal ability. The results indicated that Scenedesmus sp. grew well in the wastewater (with a growth rate from 0.3 to 0.38/day) and produced up to 70.2 mg/L of dry biomass. The algal species was able to remove ammonium (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:msubsup><mml:mrow><mml:mtext>NH</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math>), nitrate (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:msubsup><mml:mrow><mml:mtext>NO</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math>), phosphate (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:msubsup><mml:mrow><mml:mtext>PO</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math>), total phosphorus (TP), COD, and BOD 5 with removal rates up to 93%, 84%, 97%, 96%, 93%, and 84%, respectively. Autobioflocculation (AFL) was observed in all cultures with flocculation activity of up to 88.3% in the highest algal biomass treatment. The formation of bioflocculation enhanced the removal of nutrients, COD, and BOD 5 from wastewater effluent. The results indicated that wastewater from a fertilizer plant could be used as a cost-effective growth medium for algal biomass. The autoflocculation of microalgae could be used as a more practical approach for wastewater treatment using microalgae to eliminate eutrophication.