Application of Freeze Concentration Technologies to Valorize Nutrient-Rich Effluents Generated from the Anaerobic Digestion of Agro-Industrial Wastes

Abstract

The production of biogas through anaerobic digestion implies the generation of 90–95% of digested raw material, namely digestate. A nutrient-rich stream is generally applied to cropland to enhance yields, due to its high abundance of nutrients. Nevertheless, the intensive digestate farming brings about nutrient saturation and groundwater contamination. The application of downstream emerging technologies that focus on the recovery of nutrients from digestate have been studied, yet freeze concentration technology (FC) has never been considered for this purpose. This study evaluates the performance of FC technology applied to concentrate nitrogen (N), phosphorus (P) and potassium (K) from an effluent of a reverse osmosis unit that is treating the digestate of agro-industrial waste effluents. For this aim, two lab-scale methodological approaches were investigated, namely, progressive FC (PFC) and suspension FC (SFC), set through the utilization of different FC configurations. The concentrates obtained in both FC methods agreed with the regulations for fertilizers in terms of nutrients and metals content; meanwhile, the diluted fraction can be delivered as water for irrigation in high-density livestock areas. The application of FC solves the transportation cost side effect of livestock waste on the one hand, and soil contamination with nutrient on the other hand.

Progressive stirred freeze concentration: Effect of operative parameters on vital statistics of beer

“…The $$$ {\overline{K}}_{\mathrm{app}} $$$ of the solids were higher than ethanol values, which may be associated with the compounds' higher molecular weight than ethanol (Uald‐Lamkaddam et al, 2021). The higher the molecular weight, the higher the solute occlusion in the ice.…”

“…T A B L E 3 Significance factors of the response surface analysis of the progressive stirred FC. ethanol (Uald-Lamkaddam et al, 2021). The higher the molecular weight, the higher the solute occlusion in the ice.…”

Experimental study on progressive freeze-concentration based desalination employing a rectangular channel crystallizer

“…16 The progressive freezeconcentration (PFC) process facilitates the unidirectional growth of ice and produces a single ice crystal over a cold surface with liquid motion beside the ice-liquid interface. 17 Researchers explored the PFC method for application in fruit 18 and vegetable 19 juice, synthetic urine, 20 sucrose and bovine serum albumin (BSA) solution, 21 whey proteinsucrose-salt mixtures, 22 dairy products, 23 biopesticides, 24 nutrient recovery from agro-industrial wastewater, 25 and Ca 2+ ion separation from wastewater. 26 Several groups of researchers applied the PFC method to desalinate brackish water, seawater and brine involving a single freezing-thawing stage.…”

Effects of Critical Operation and Cleaning Parameters on Performances and Economic Benefits of Biogas Slurry Concentration by Forward Osmosis Membrane

“…Concentrating and recycling biogas slurry is the fundamental way to solve the above-mentioned problems [ 8 ]. In biogas slurry concentration technology, membrane separation technology has become an ideal choice for biogas slurry concentration due to its cost-effective and convenient operation and no change in composition characteristics.…”