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In the present study, we report the first operation of a pilot scale ion exchange membrane bioreactor (IEMB). It treated 1–2 m3/d of water contaminated with nitrate. IEMB was made up of anion exchange membrane spiral module integrated with a fixed bed bioreactor (FBBR), a novel configuration for an IEMB system. Nitrate elimination was accomplished through Donnan dialysis using chloride as counter ion followed by heterotrophic denitrification in an anoxic FBBR employing glycerol as electron donor and carbon source. The performance of IEMB revealed an excellent nitrate removal at the selected operating conditions, successfully eliminating a nitrate loading rate of 5.0 kg NO 3 −/m3/d and producing 30 ± 5 mg/L nitrate in the effluent at steady state. Anion exchange membrane being non-selective also transferred a significant concentration of sulphate from the feed-side to the bio-side leading to sulphate accumulation in FBBR. As a result, denitrification performance was affected due to the activation of sulphate reducing bacteria leading to the upset of FBBR. Batch experimental study aiming to screen the effect of nitrate to sulphate ratio on denitrification, demonstrated the possible occurrence of sulphate reduction at [nitrate]/[sulphate] < 0.2, exhibiting a highly negative oxidation reduction potential (ORP) value (−450 mV). This signifies that a minimum [nitrate]/[sulphate] > 0.2 is required as to suppress sulphate reduction phenomenon during denitrification. IEMB calibration for denitrification using glycerol as a carbon source revealed that 100 % stoichiometric donor/acceptor (C/N) ratio was suitable for producing sufficient nitrate biodegradation and acceptable ORP value (~−220 mV). Present work established promising application prospects of IEMB comprising nitrate selective membrane module for the treatment of high nitrate wastewater with a treatment capacity of 1.5 m3/d at optimized operating conditions. • Established IEMB treated high nitrate contaminated water with a capacity of 1.5 m3/d. • Exit nitrate from the IEMB satisfied legal limits of different countries. • ORP reflects the availability of electron donor for efficient denitrification. • Activity of coexisting bacterial communities depends on nitrate to sulphate ratios. • Improper [nitrate]/[sulphate] ratio impairs denitrification and initiate sulphate reduction. [ABSTRACT FROM AUTHOR]

Eutrophication, driven by excessive nutrient concentrations in water bodies, is a critical global environmental issue affecting water quality, ecosystems, and human health. Discharging nutrient-rich secondary effluents from municipal wastewater treatment plants exacerbates this problem. This study aimed to assess the effectiveness of a pilot-scale Ion Exchange Membrane Bioreactor (IEMB) in removing nitrate from secondary treated effluent. The process involved Donnan dialysis (DD) followed by heterotrophic denitrification in an anoxic fixed bed bioreactor (FBBR). DD process demonstrated an efficiency of over 75 % when nitrate was externally spiked in the secondary treated effluent and over 90 % without spiking, reaching final concentrations below 5.65 mg NO 3 –N/L and 1.1 mg NO 3 –N/L, respectively. Furthermore, denitrification in FBBR was greater than 95 % at C/N ratio of 1.8–2 provided in the form of glycerol at an HRT of 2 h when nitrate was not spiked externally. Though sulphate accumulation occurred in the receiver (bio-side) during DD, denitrification outperformed sulphate reduction, as confirmed by the favourable oxidation-reduction potential (ORP) readings (−50 to −200 mV) in the FBBR reactor. Optimal conditions for nitrate removal, considering chemical and energy consumption, resulted in a cost of $0.237 per cubic meter of treated secondary effluent during continuous operation. A life cycle assessment (LCA) was also conducted to understand the environmental impacts of the IEMB. In light of these findings, IEMB showed a promising potential for tertiary wastewater treatment, providing an economical and sustainable solution for nutrient removal and indirect potable reuse of treated wastewater. [Display omitted] • Pilot scale IEMB treated high nitrate secondary effluent at a capacity of 2.88 m3/d. • Transport in DD was influenced by initial concentration, driving ion, feed composition. • Sulphate had minimal effect on denitrification as denitrifiers dominated FBBR. • Operational cost of treating 1 m3 of secondary effluent for nitrate was $0.237. • LCA showed IEMB has lesser environmental impacts than RO. [ABSTRACT FROM AUTHOR]