Integration of Ultra- and Nanofiltration for Potato Processing Water (PPW) Treatment in a Circular Water Recovery System

Abstract

The article analyzes integrated ultrafiltration (UF) and nanofiltration (NF) processes for potato processing wastewater treatment for the purpose of which a laboratory filtration system for flat sheet membranes with the effective surface area of 1.4 × 10−2 m2 (UF: polysulfone, cut-off: 10,000 Da; NF: polypiperazine amide, cut-off: 150–300 Da) was used. As part of the study, the effect of the transmembrane pressure of UF (0.2 MPa and 0.4 MPa) and NF (1.0 MPa and 1.8 MPa) on the permeate flux and rejection coefficient was investigated and the impact of sewage preparation methods on the degree of pollution reduction was determined. Moreover, a method for a fouling layer removal from the UF membranes is also proposed. The results of the analyses conducted by the authors show that the pretreatment stage offers additional advantages to TSS and turbidity removal. In both cases (0.2 and 0.4 MPa), UF used after the pretreatment process resulted in a 97–99% reduction in these impurities. The analysis of the determined rejection coefficients shows that the use of NaOH and H2O2 for the regeneration of the UF membrane has a positive effect on filtration efficiency. Regarding NF, the rejection coefficients for most tested parameters were higher for the 1.8 MPa process compared to 1.0 MPa, and approximately 80% of water was recovered.