Reduction of wastewaters and valorisation of by-products from "Serpa" cheese manufacture using nanofiltration.

Second cheese whey (SCW) is a by-product of cheese and curd cheese production that is usually not recovered and therefore contributes substantially to the negative environmental impact of the cheese manufacture plants. Membrane technology, namely nanofiltration (NF), is used in this work for the recovery of SCW organic nutrients, resulting from "Serpa" cheese and curd production. The SCW is processed by NF to recover a rich lactose fraction in the concentrate and a process water with a high salt content in the permeate. The permeation experiments were carried out in a plate and frame NF unit, where two NF membranes (NFT50 and HR-95-PP) were characterized and tested. The NF permeation experiments were performed accordingly with two different operation modes: total recirculation and concentration. In order to select the best membrane and operating pressure for the SCW fractionation, total recirculation experiments were carried out. After the membrane selection, the concentration experiments showed that the selected membrane (NFT50) at 30 bar allows a water recovery of approximately 80%, concentrating the second cheese whey nutrients approximately 5 times. Therefore, the NF operation can successfully reduce the wastewater organic load and simultaneously contribute to the valorisation of the cheese and curd cheese manufacture by-products.

Flocculation/flotation/ultrafiltration integrated process for the treatment of cork processing wastewaters.

Membrane fouling is the major problem in the treatment by ultrafiltration (UF) of the cork processing wastewaters. This problem leads to drastic reduction on the permeate fluxes and has been associated with wastewaters phenolic/tannic colloidal matter. The present work proposes a flocculation/flotation/ultrafiltration integrated process for the treatment of these wastewaters. A flocculation study was carried out in jar-test equipment with chitosan. The zeta-potential and the particle size were monitored at different pH values and for different chitosan concentrations. The results showed an increase of the zeta-potential when chitosan is added and a significant increase of the effluent particle size with the decrease of the pH. A dissolved-air flotation study was performed with the flocculated wastewater. The parameters varied were the operating pressure and the recycle ratio. It was observed that for higher pressures and at a recycle ratio of 0.19 the polyphenols removal was higher. The UF experiments were carried out in flat-sheet cells of 13.2 cm2 of membrane surface area at transmembrane pressures of 1-3 bar. A commercial membrane (Ropur-TS60) and four cellulose acetate membranes with molecular weight cutoff (MWCO) ranging from 4.5 to 86 kDa were used. The flocculation/flotation pretreatment led to the enhancement of the UF permeate fluxes. For the membrane with higher MWCO, the permeate flux enhancement reached 130%.