Collaborative Research: Prechlorination, aging, and backwashing effects on spatiotemporal ultrafiltration fouling: Optimizing productivity by combining experiments and theory

Worldwide, approximately 4 billion people experience severe water shortages at least one month per year and over 500 million people experience shortages throughout the year. Wastewater reclamation is increasingly being utilized by water utilities in the United States and worldwide to increase their supply of drinking water. In many wastewater-reclamation plants, a hollow fiber (HF) ultrafiltration (UF) membrane system is combined with a disinfection pretreatment step (e.g., chlorination) to remove suspended solids in secondary treated wastewater including bacteria, viruses, and other pathogens.

However, the filtration efficiency and water production decrease during operation as the pores of the membrane HFs become clogged by the removed suspended solids. Thus, the HF UF membrane modules of wastewater reclamation systems needed frequent cleaning (multiple times per day) during their operation. The overarching goal of this project is to develop and validate a new generation of mathematical and computational models that could guide the operation and optimization of an HF UF membrane system with the aim of maximizing its water production while reducing its energy consumption during wastewater reclamation.

To advance this goal, the Principal Investigators (PIs) propose to carry out an integrated experimental and modeling research program to build and validate mathematical/computational models of membrane operation that take into account the effects of membrane module geometry, fiber packing density, and chlorine pretreatment on the filtration efficiency and water production of an HF UF membrane system. The successful completion of this research will benefit society though the development of new fundamental knowledge and modeling tools that could guide the operation of UF HF membrane systems in wastewater reclamation plants to improve and maximize water production while reducing the energy required to operate such systems.

Additional benefits to society will be achieved through student education and training including the mentoring of three graduate students at Florida State University, Worcester Polytechnic Institute, and Texas A&M University.

Hollow fiber (HF) ultrafiltration (UF) membrane modules/systems are increasingly being used in wastewater reclamation plants to remove suspended solids, bacteria, viruses, and other pathogens from secondary treated wastewater. However, the development of validated mathematical and computational models that could accurately simulate the operation and performance of an UF HF membrane module/system has remained elusive.

The goal of this project is to derive a mechanistic understanding of spatiotemporal variations in the performance of HF UF membrane module/system over multiple time and spatial scales. To advance this goal, the Principal Investigators (PIs) propose to leverage analytical solutions of fluid flow equations starting with a single fiber, moving to a “few” fibers arranged in different patterns to reproduce the geometry and hydraulic properties of a commercial HF UF membrane module.

In addition, the PIs propose to develop and validate a computational model that could be used to simulate the performance of an HF UF membrane module with the goal of identifying optimal operational parameters including chlorine pretreatment concentration, the flux/pressure regimes during forward filtration, and the membrane backwash pressure and run time during cleaning. The successful completion of this research has the potential for transformative impact through the generation of new fundamental knowledge and validated mathematical/computational models to guide the design, operation, and optimization of HF UF membrane modules/systems in wastewater reclamation plants.

To implement the educational and training goals of this project, the PIs propose to develop an online course to increase public literacy in water filtration and water reuse in collaboration with Lifeology—a platform that brings together scientists, communicators, and writers to design and produce educational materials to engage broader audiences. In addition, the PIs plan to leverage existing outreach programs at their respective institutions to design and implement K-12 teacher training programs with a focus on the development of lesson plans related to water quality and treatment.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.