Immediate one-step lime precipitation process for the valorization of winery wastewater to agricultural purposes

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 O-2 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.

Automated summary

The study analyzed winery wastewater from the Village of Vidigueira in southern Portugal, revealing challenges such as acidic pH, high COD, and turbidity. Adding lime solution can effectively remove pollutants from the wastewater, resulting in a precipitate rich in various elements.