Optimization of a nanofiltration membrane process for tomato industry wastewater effluent treatment

The wastewater stream produced during tomato manufacturing is characterized by a dark color and bad smell, and is heavily polluted by organics, suspended solids and ground particles. The concentration of pollutants in the effluent can vary considerably with time and space due to the changes in the harvested fruit composition and season. A discharge in the municipal sewage system of these streams is not directly possible because of the high organic contents above the legally tolerated limits. This work deals with the treatment and purification of the wastewater stream from the tomato industry by a biological pretreatment step and a batch nanofiltration process step. For the latter, critical fluxes were measured at different recovery levels. This permits applying membrane process optimization methods based on the critical flux. The experiments show that the purification of the wastewater up to a water compatible with the municipal sewer system requirements is possible, with a recovery rate of 90%. Short-term fouling issues may be avoided at permeate fluxes about or below 8.2 l h−1 m2.