Ultrafiltration as tertiary treatment for industrial reuse

In this paper we present the results obtained from tests conducted on ultrafiltration treatment of a secondary effluent designated for possible industrial reuse. Tests were carried out at Empoli Wastewater Treatment Plant (WWTP) (Florence, Italy) with the use of a hollow fiber pilot plant (mod. ZW-10, Zenon Environmental). Testing lasted for about 4 months, during which the pilot plant was fed by effluent from the wastewater treatment plant. Results show that the permeate was of high quality. The membranes were very efficient in reducing turbidity (94.5%) and TSS (98.7%). The reduction of COD (around 35%) was also good. The permeate also showed low SDI values (usually < 3%). With respect to microbiological parameters, treatment was shown to be above all efficient in the removal of Escherichia coli. The permeate already respects required quality standards set forth by a new technical law decree on water reuse, soon to be approved within Italian Legislation. Based on these test results, a preliminary design of a wastewater treatment plant with the complex of structures necessary to the distribution of the treated wastewater in the industrial area located closed to the plant, has been created. Under this design, treated water could be produced at a cost of 0.38 Euro/m³, which includes investment, financial charges and maintenance costs.