Application of Cyanobacterial Consortium to Remove Ammoniacal-N, Phenol, and Nitrate from Synthetic Coke-Oven Wastewater as Tertiary Treatment

Abstract

This investigation focused on phycoremediation of pollutants from synthetic coke-oven wastewater using a cyanobacterial consortium of Leptolyngbya sp. and Planktothrix sp., and biomass production. Lethal dose analysis was performed for test strains with varying concentrations of pollutants, and maximum biomass obtained were 322.7±22.54, 322.3±12.06, and 352±12.53 mg L−1 at 2 mg L−1 phenol, 175 mg L−1 ammoniacal-N, and 30 mg L−1 nitrate, respectively. A one-factor-at-a-time (OFAT) approach was followed to determine suitable operating conditions for maximum removal by varying pH (8–10); inoculum size (IS) (5%–10%); and initial concentrations (ICs) of phenol (2–3 mg L−1), ammoniacal-N (150–200 mg L−1), and nitrate (30–40 mg L−1). The most preferred condition as analyzed by OFAT was pH=8; IS=10%; and initial concentrations of phenol=2.5 mg L−1, a mmoniacal-N=175 mg L−1, and nitrate=30 mg L−1. Response surface methodology (RSM) was used to obtain the optimum condition for removal of the pollutants and biomass production. Further experiments were performed at the optimum conditions as analyzed by OFAT and RSM with synthetic treated coke-oven wastewater (STCW) containing mixed pollutants, and the results were compared. Both OFAT and RSM analysis results were effective for real wastewater treatment, but from an economic point of view, OFAT analysis results were more suitable. Biomolecules, namely carbohydrate, protein, and lipid molecules, were extracted from treated cyanobacterial biomass to assess the prospect of value-added product formation. Mechanistic pathways for metabolism of pollutants were discussed.