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Resource recovery with membrane processes: overcoming limitations and increasing performance and economics
Schwiebert, Alexander M.
Schwiebert, Alexander M.
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2025
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2026-11-11
Abstract
Resource recovery from water and wastewater is of increasing importance due to stressors such as climate change, which decreases water availability, especially in the western United States. Several solutions to mitigate water stress have been proposed and are being implemented, and membrane processes offer unique benefits and high potential for enhancing both water supplies and recovery of valuable resources.
This thesis examines two ways in which membrane processes can be utilized to increase resource recovery. The first focuses on increasing resource recovery in membrane desalination processes. The goal was to increase water recovery in a closed-circuit reverse osmosis system by implementing a scaling detection system, which enables a water recovery of over 90% from a gypsum-rich solution without scaling occurring by detecting crystal growth as it occurs in solution. From the highly concentrated brine, gypsum was recovered, which can be reintroduced to the economy. The second focus was on utilizing membranes for the recovery of nitrogen from nitrogen rich streams. Anaerobic digester centrate was collected, analyzed and a pretreatment process developed. Nitrogen was then recovered from the pretreated centrate through a membrane contactor process. This was done in lab-scale experiments at 1.5 L/min with up to 30 L batches to optimize conditions for pilot-scale testing at 75 L/min with over 5,500 L batches. Pilot-scale testing was then implemented with an ultrafiltration pilot system as a pretreatment process. The ultrafiltration system removed solids and foulants from the centrate, before nitrogen was recovered with a membrane contactor system. The pretreatment process combined with the membrane contactors system allowed for >80% of nitrogen recovery without nitrogen recovery performance declining.
The economic viability of the pretreatment and membrane contactor processes for a 20 MGD wastewater treatment facility was investigated in a techno-economic analysis, with data from piloting applied for the economic evaluation of the process in a model. The results indicate large economic benefits for wastewater treatment facilities larger than 10 MGD. Sensitivity analysis of key parameters for the economic viability of the process for a 20 MGD wastewater treatment facility was conducted. Base (NaOH) cost, aeration demand, and electricity cost were found to have a large impact on economic viability of the process.
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