Multidimensional assessment of (bio)electrochemical GAC-packed bed filters for laundry greywater treatment

Abstract

As water demand outpaces supply, scarcity has become a critical global challenge. Wastewater reuse presents a viable solution, driving the development of innovative, low-cost, and energy-efficient technologies such as bioelectrochemical systems (BESs). Granular activated carbon (GAC) was used as a volumetric electrode in GACpacked bed filters to treat synthetic laundry greywater with high surfactant concentration. Five configurations were assessed, including biological and non-biological microbial fuel cells (MFCs), microbial electrolysis cells (MECs), and an abiotic GAC control. GAC-packed (bio)electrochemical filters achieved over 90 % soluble COD removal in BESs and 86.18 % in abiotic systems through biodegradation and adsorption. Complete sodium dodecyl sulfate and lactate removal further demonstrated system efficacy. Results showed that turbidity reduction exceeded 85 %, with MECs achieving 98.30 %. Nitrate (84-100 %), sulfate (70-89 %), and phosphate (28-86 %) removals met international water quality standards. Chloride, calcium, and magnesium remained within acceptable irrigation thresholds, and effluent pH and EC complied with regulations. However, sodium removal was inadequate (SAR: 4.38 f 0.72; Na%: 71 f 0.02 %), requiring further treatment, representing an unsolved aspect of GAC-packed bed filters. Biological systems stabilized ionic fluctuations, while non-biological ones exhibited greater variability due to abiotic desorption. MECs exhibited a volumetric current density of 124.53 f 0.067 mA/m3, whereas MFCs had significantly lower outputs (0.016 f 0.009 mA/m3). A cost analysis estimated a Levelized Cost of Water of 0.1-0.2 USD/L, which is higher than the reported values for other technologies. High capital costs remain a key barrier, and integrating renewable energy is essential for economic feasibility.