Nutrients and pharmaceuticals removal from wastewater by culture and harvesting of Chlorella sorokiniana

• Removal of nitrates and phosphates was close to 100% at the end of the batch.
• Phosphates removal was higher than nitrates in the semicontinuous culture.
• Removal of salicylic acid and paracetamol was around 70% at the end of the batch.
• Removal rates were 2.3 times higher for salicylic acid than for paracetamol.
• AlCl3 provided efficiencies above 95% in 1 min with 200 mg g−1 dose.

This work aimed to study both the removal of nutrients and pharmaceuticals, namely salicylic acid or paracetamol, from water by the culture of Chlorella sorokiniana. The removal of nutrients was nearly complete at the end of the batch culture; above 70% for nitrates and 89% for phosphates in the semicontinuous culture. The pharmaceuticals removal kinetics were 2.3 times greater for the salicylic acid than paracetamol, reaching volumetric efficiencies above 93% for salicylic acid in the semicontinuous culture. Finally, to separate the microalgae biomass from treated water, metal salts, synthetic polyelectrolytes and a biopolymer were tested as coagulants–flocculants. The best flocculation results were achieved with AlCl3 (95.23% with 200 mg g−1, 1 min incubation time). However, given that resulting flocs had different characteristics, flocculants must be chosen on the basis of the subsequent use of the biomass.

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