Optimizing Membrane Processes for Sustainable Water and Wastewater Treatment

Abstract

Water scarcity is one of the most critical global challenges. However, there are also critical water challenges that are deeply connected to food and energy, as these resources are integral components of growth and human life. This dissertation focuses on developing simulation models to demonstrate membrane capabilities of a multitude of applications, including integration of solar energy with nanofiltration membranes to produce standalone fit-for-purpose systems for off-grid water and energy co-production, selective ammonia recovery via humidity-assisted sweeping gas membrane distillation (SGMD), and synthesizing membranes to improve ion selectivity. Off-grid solar nanofiltration units with co-production of water and energy was capable of achieving higher cost reduction compared to when having separate units for energy and water production. SGMD offers a compact, efficient alternative to air stripping for ammonia recovery in wastewater treatment, while minimizing energy loss (86% reduction) and enhancing ammonia recovery and reuse. Simulations of a hypothetical calcium-permeable reverse osmosis carrier-based membrane show that selective Ca²⁺ transport mitigates gypsum scaling and extends the achievable water recovery ratio. These advancements highlight the versatility of membrane processes in addressing critical challenges in resource recovery, decentralized water treatment, and optimized desalination processes. Additionally, the study critically evaluates the theoretical assumptions of the Donnan Steric Pore Model with dielectric exclusion in nanofiltration, enabling the development of a simplified predictive model. By advancing our understanding of membrane transport and properties, we can improve the design of membranes and increase the adoption of membrane technologies with sustainable systems, resource recovery, and water recovery.