Midway Evaluation in Environmental Engineering - Koustubh Ravindra Karande

Title of thesis:
Electrodialysis for nutrient recovery from municipal wastewater: Membrane fouling and mitigation

Student:
Koustubh Ravindra Karande

Doctoral committee:
Dr. Frank Lipnizki, Professor at the Department of Process and Life Science Engineering, Lund University, Sweden Dr. Ólafur Ögmundarson, Associate Professor at the Faculty of Food Science and Nutrition, University of Iceland

Abstract:
Limited natural resources and increased food demand have put stress on the global fertilizer industry. In recent years, recovery of nutrients (such as nitrogen and phosphorus) from municipal wastewater has been considered as a sustainable alternative solution, towards achieving the UN SDG 6.3 (reducing release of untreated wastewater to water body) and SDG 12.2 (reducing stress on natural resources). Membrane-based electrodialysis (ED) has been adopted as an emerging technology for recovering nitrogen and phosphorus from wastewater due to its simple operation and high nutrient recovery rates. This study employed ED with sacrificial magnesium anode to recover nitrogen and phosphorus (towards struvite formation) from primary municipal wastewater and examined the effects of various operating conditions on ED membranes' fouling behaviour. The results revealed that (1) the volume ratio of the concentrate solution to feed solution influenced ED resistance and Mg corrosion rate; (2) in the feed chamber, the cation exchange membrane (CEM) was more susceptible to foulant depositions (especially organics) than the anion exchange membrane (AEM); the total foulant density was linearly correlated with the increased electrical resistance; (3) higher nutrient concentration and lower organic concentration in the feed enhanced nutrient recovery rates and reduced foulant accumulation, towards high potential of struvite formation; (4) higher current density promoted nutrient recovery, but also caused serious membrane fouling, even for the wastewater containing low organic contents; (5) increasing crossflow velocity induced strong shear force along the membrane surface to alleviate membrane fouling and improve ion diffusivity due to enhanced turbulence which benefited nutrient recovery. Further studies involving development of membrane fouling control strategy, long-term ED performance for struvite production, and the techno-economic-environmental impact assessment will be conducted.