Hydraulic Resistances of Membrane Filters and their Role in Industrial-Scale Make-Up Water Treatment

Abstract

This study presents the design and evaluation of a multistage membrane filtration system to produce ultrapure quality make-up water for thermal power plants using the Danube River as the feedwater source. Laboratory-scale filtration experiments were performed using a flat-sheet test cell to determine the hydraulic resistances of ultrafiltration, nanofiltration, and reverse osmosis membranes under varying transmembrane pressures. The experimental results confirm a linear correlation between the applied pressure and the permeate flow rate for all three membrane types under the tested conditions and establish a resistance-in-series model that provides the basis for upscaling calculations. The flow rate requirement for a single block of Paks power plant is 26.1 m³/h of ultrapure water, using 90% recovery per membrane stage. Two-stage microfiltration was applied to sufficiently remove the suspended solid content from raw water. The proposed system comprises ultrafiltration, nanofiltration, two-stage reverse osmosis, and electrodeionization, achieving a cumulative recovery of 53.14% and requiring a raw water feed of 49.11 m³/h. To drive the process, 5 centrifugal pumps were selected across different pressure zones (3, 9, 20, 31, 35 bar), with a total shaft power of 132.6 kW, corresponding to a specific energy consumption of 5.079 kWh/m³. This research provides a viable framework for scaling laboratory membrane setup to industrial pure water production, underscoring the necessity of an abundant feedwater source to compensate for the tradeoffs in multi-stage recovery.