Immediate one-step lime precipitation process for the valorization of winery wastewater to agricultural purposes
2021
Luz, Silvana | Rivas, Javier | Afonso, Alexandra | Carvalho, Fátima
The winery wastewater (WW) of the Village of Vidigueira, in south of Portugal, presented an acid pH (4.26 ± 0.029), a high content of chemical oxygen demand (COD = 3236 ± 30.43 mg L⁻¹), turbidity (160.0 ± 7.68 NTU), total P (155.5 ± 6.36 mg L⁻¹) K (100.5 mg L⁻¹), and low level of metals: Pb, Cd, Cu, Ni, Mn, Fe, Zn. The K and the total P content could make them attractive from an agricultural point of view. However, the high turbidity biochemical oxygen demand (BOD₅ = 1266.7 ± 208.7 mg O₂ L⁻¹) fecal coliforms (45 ± 29.8 ufc/100 mL) and toxicological total phenols 13.239 ± 3.007 mg galic acid L⁻¹ is the main limiting parameters. By using 5 g L⁻¹ of lime solution, the best reactional conditions are achieved: pH = 12 with a minimum volume of the produced sludge’s, 33.5 ± 4.92 mL L⁻¹. These reactional conditions allow reaching high removal levels of BOD₅, turbidity, total P, and total phenols: 77.9, 98.7%, 87.1%, and 99.9%, respectively. Simultaneously, the fecal coliforms and Enterococcus are 100% eliminated. The precipitate obtained is rich in calcium (2.7891 ± 0.4350 mg Ca kg⁻¹) organic matter (10.05 ± 0.11%), P (895.0 ± 35.4 mg P₂O₅ kg⁻¹), and K (990.0 ± 84.9 mg K₂O kg⁻¹). During carbonatation reactions, the pH (7.46) and electrical conductivity (EC) (1.805 dS m⁻¹) decreased spontaneously while the Ca²⁺, K⁺, and F⁻ kept high: 426.53 mg L⁻¹, 240.53 mg L⁻¹, 176.03 mg L⁻¹, respectively.
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