Computational Modelling of Nutrient Recovery from the Greenhouse Water Cycle Using Monovalent Selective Electrodialysis

Abstract

Eutrophication significantly degrades freshwater systems by decreasing water quality and disrupting the natural ecosystem. Greenhouse effluent, a significant contributor to eutrophication, is usually composed of primary (nitrates, phosphates, and potassium) and secondary (calcium, magnesium, and sulphates) nutrients, as well as ions damaging to crops (sodium, chloride) that limit effluent reuse. Monovalent selective electrodialysis (MSED), a variant of conventional electrodialysis (ED), may hold the key to combatting eutrophication while maximizing wastewater reuse: the technology can recycle nutrients for irrigation rather than disposal into the environment. In addition, it can reduce sodium accumulation, the primary barrier to achieving 100% reuse, in greenhouse wastewater. MSED has proven effective in brackish water treatment, removing harmful monovalent species and retaining beneficial multivalent species. However, a computational model to investigate its performance in treating greenhouse effluent, which differs notably in ionic composition relative to brackish water, is unavailable in the literature. This paper studies the competitive transport between various ionic species in greenhouse effluent and provides an experimentally-validated performance model for the feasibility of MSED adoption in greenhouses. The results illustrate MSED’s promise in desalinating greenhouse wastewater. MSED saves 93% of phosphates, 85% of sulphates, 78% of calcium, and 90% magnesium, while removing 87% of sodium and 91% of chloride.