Winery wastewater purification by reverse osmosis and oxidation of the concentrate by solar photo-Fenton

• RO is considered quite efficient in purifying winery wastewater.
• RO permeate fulfills the quality criteria to be used for irrigation purposes.
• Toxicity and phytotoxicity of the permeate are substantially reduced by RO.
• RO concentrate can be successfully treated further by solar photo-Fenton process.
• Polyphenols can be almost completely concentrated to the concentrate stream.

Membrane processes have received in recent years considerable attention for the separation and concentration of inorganic and organic compounds from various wastewater streams. This work investigated the efficiency of a pilot-scale reverse osmosis (RO) process on the treatment of winery wastewater with an initial chemical oxygen demand (COD) of 5350 mg L−1. The removal of COD by the RO process reached 97% resulting in a permeate with residual COD level lower than 150 mg L−1. Furthermore, the total nitrogen removal reached 67%, total phosphorous 76.2%, total suspended solids 94%, total solids 96%, and conductivity 94%. These results demonstrated an excellent solid and soluble salts separation. Toxicity and phytotoxicity assays in the feed, concentrate and permeate samples were also performed, showing that the toxicity of the original effluent could be reduced or even eliminated through the RO process. Moreover, the volume recovery achieved in the recirculation mode was 65%, whereas in the single pass was 50%. Further treatment of the concentrate (COD 10290 mg L−1) by solar photo-Fenton oxidation achieved a COD reduction of 75%. In an effort to evaluate the capacity of the RO process to concentrate valuable polyphenols, five selected compounds were examined. The process proved to be quite efficient in almost completely concentrating them in the concentrate stream.