Electrodialysis is used in food and bio-based industries for selective separation and recovery of target ions and neutral molecules. Anion exchange membranes (AEM) are prone to fouling due to their complex interactions with organics. Currently, research has focussed mainly on fouling tests using model organic foulants. In this study, three different complex industrial feed streams: corn steep liquor (CSL), citric acid by-product (CA), and cheese whey (CW), were used to foul two commercial AEM types: Fujifilm type-10 (homogeneous) and RALEX (heterogeneous). A 1.5 - 2.3 fold higher membrane resistance after fouling was a result of a difference in membrane structure, ion exchange capacity, water uptake, and thickness (depending on the feed used). Liquid Chromatography - Organic Carbon Detection (LC-OCD) analysis of feed revealed highly hydrophilic (CDOC) fractions in CSL (85%), CA (87%), and CW (100%). This analysis was extended to foulant desorption solutions (NaCl (35 g/L) and EtOH-water-H2SO4 mixtures), which revealed that > 90 % of humic substances (HS) and building blocks (BB) desorbed when using NaCl (35 g/L), following a (concentration wise) desorption order: HS > BB > LMWN > BP > LMWA. For the EtOH-water-H2SO4 solution, low molecular weight neutrals and acids (LMW(A + N)) were desorbed majorly (>60%) and followed a desorption order: LMWN > LMWA > BB > BP > HS. Desorption due to the ion-exchange mechanism was dominant for NaCl (35 g/L) solution, while foulantdesorbant polar interactions were prevalent for the EtOH-water-H2SO4 solution. Upon foulant desorption using NaCl (35 g/L) solution, RALEX AEM owing to the presence of nanovoids in them, showed a 1.5 - 4 fold higher concentration difference vs. FF10 AEM, while this difference was not dominantly observed when EtOHwater-H2SO4 mixture was used. This study revealed that LMW fractions could possibly enter into the membrane matrix whereas HS and BB fractions owing to their high molecular weight, majorly adsorbed on surfaces.

Production of struvite (MgNH4PO4·6H2O) from waste streams is increasingly implemented to recover phosphorus (P), which is listed as a critical raw material in the European Union (EU). To facilitate EU-wide trade of P-containing secondary raw materials such as struvite, the EU issued a revised fertilizer regulation in 2019. A comprehensive overview of the supply of struvite and its quality is presently missing. This study aimed: i) to determine the current EU struvite production volumes, ii) to evaluate all legislated physicochemical characteristics and pathogen content of European struvite against newly set regulatory limits, and iii) to compare not-regulated struvite characteristics. It is estimated that in 2020, between 990 and 1250 ton P are recovered as struvite in the EU. Struvite from 24 European production plants, accounting for 30% of the 80 struvite installations worldwide was sampled. Three samples failed the physicochemical legal limits; one had a P content of <7% and three exceeded the organic carbon content of 3% dry weight (DW). Mineralogical analysis revealed that six samples had a struvite content of 80–90% DW, and 13 samples a content of >90% DW. All samples showed a heavy metal content below the legal limits. Microbiological analyses indicated that struvite may exceed certain legal limits. Differences in morphology and particle size distribution were observed for struvite sourced from digestate (rod shaped; transparent; 82 mass% < 1 mm), dewatering liquor (spherical; opaque; 65 mass% 1–2 mm) and effluent from upflow anaerobic sludge blanket reactor processing potato wastewater (spherical; opaque; 51 mass% < 1 mm and 34 mass% > 2 mm). A uniform soil-plant P-availability pattern of 3.5–6.5 mg P/L soil/d over a 28 days sampling period was observed. No differences for plant biomass yield were observed. In conclusion, the results highlight the suitability of most struvite to enter the EU fertilizer market.

In search of more sustainable approaches for water reclamation from petrochemical industries, Membrane Distillation (MD) has become an alternative to pressure driven membrane technologies. In the present study, the efficiency of a Direct Contact MD (DCMD) configuration with hydrophobic and oleophobic commercially available membranes was examined, aiming to reject the main petrochemical pollutants such as acetate, propionate, and phenol. The influence of the feed and distillate temperatures, cross-flow velocity and pH on the flux and quality of the obtained distillate was further studied in a systematic way. The highest overall rejection efficiency of acetate, propionate, and phenol of approximately > 97% was obtained with the oleophobic membrane at pH similar to 13. The rejection of phenol was mainly influenced by pH, as this impacts its dissociation and thus its volatility. Moreover, to calculate the rejection of the components a novel mathematical method for lab-scale experiments was developed. This method is based on (dynamic) mass balances and was shown to be superior to state-of-the-art methods, which can greatly overestimate rejection. The method is independent of the experimental time and avoids the dilution effect of the initial water in the distillate vessel. The findings underline the importance of correct calculation of rejection in MD, to obtain results valuable for practical application.