Nanofiltration of Brewery Wastewater for Agricultural Reuse

Abstract

With global water scarcity and demand continuing to rise, alternative water sources are being explored for agricultural irrigation. The brewery industry, among the largest industrial water consumers, generates wastewater typically characterized by high biological oxygen demand (BOD) and chemical oxygen demand (COD) due to organic compounds, as well as total suspended solids (TSS) and nutrients such as phosphorous and nitrogen species. It can also have high sodium concentrations and microbial contaminants such as E. coli that serves as an indicator of fecal contamination. This thesis evaluates the application of nanofiltration (NF) as a tertiary treatment for brewery to assess its potential for agricultural reuse in accordance with Dutch and EU water reuse regulations, Regulation 2020/741.
The relevant reuse standards were first identified to establish target water quality limits. Then six brewery wastewater samples were collected at different time points to characterize influent variability. Physical, chemical and biological parameters were analyzed, including particle size distribution (PSD), TSS, ion concentrations, alkalinity, total organic carbon (TOC), and E. coli as an indicator pathogen of fecal contamination. The results found maximum particle sizes that could cause pore blocking of polymeric membrane fibers and particle load to be a risk for fouling propensity, leading to the investigation of sand filtration as a pretreatment. Comparison of the measured results to the reuse standards identified sodium, sulfate, nitrate, ammonium, and E. coli concentrations were found to exceed their respective thresholds, 120 mg/L, 100 mg/L, 10 mg/L, 1.5 mg/L and 10 CFU/ 100mL, confirming the need for tertiary treatment before being reused for irrigation.
Two nanofiltration membranes, a 0.9 nm ceramic Inopor membrane and a polymeric NX Filtration dNF80 membrane, were experimentally assessed. Experiments were performed at 2 and 4 bars, using both direct and sand filtered influents, including a prolonged fouling test, to evaluate permeability, flux stability, and removal efficiency.
The polymeric membrane achieved higher removal efficiencies of TOC (81% ± 3%) removal and 7 – 55% higher removal efficiency of multivalent ions (phosphate, sulfate, Ca2+ and Mg2+). The ceramic membrane showed more consistent biological removal efficiencies, with all but one fouling test qualifying for class A reuse and 6 – 60% higher removal efficiency for most monovalent ions (Cl-, NO-2, Br-, NO3-, Na+, NH+4, and K-). During the fouling tests, the polymeric membrane recovered 93 - 96% of 5 L over four hours, while the ceramic membrane achieved 15 – 16% recovery of 2 L over 24 hours. The polymeric membrane showed higher fouling sensitivity, while the ceramic membrane had higher stability. Sand filtration pretreatment improved flux stability for both membranes, and higher pressure increased polymeric permeability but did not affect the ceramic membrane.
While the complexity of differences in membrane composition, material, and geometry prevented definitive identification of individual exclusion mechanisms, the findings provide valuable insight into how these factors collectively influence nanofiltration performance. Overall, NF effectively bridges the gap between brewery wastewater and agricultural reuse regulations. The polymeric membrane offers higher organic and multivalent ion removal and higher flux but greater fouling propensity. Whereas the ceramic membrane has a higher resistance to fouling and lower but stable flux. Sodium, nitrate, and ammonium, remain the key limitations for reuse.