Research on wastewater treatment focuses on removing contaminants efficiently, recovering resources, and reducing environmental and health impacts.

Traditional treatment trains combine physical, chemical, and biological processes. Primary treatment uses screening, grit removal, and sedimentation to remove large solids. Secondary treatment relies on microorganisms in systems such as activated sludge, trickling filters, and rotating biological contactors to break down organic matter and nutrients. Disinfection with chlorine, ozone, or ultraviolet light reduces pathogens before discharge.

Advanced research targets more persistent pollutants. Membrane technologies like microfiltration, ultrafiltration, nanofiltration, and reverse osmosis provide high quality effluent but face challenges with fouling and energy demand. Membrane bioreactors integrate biological degradation with filtration, offering compact systems and better control, particularly for reuse applications.

Nutrient removal is a central focus. Enhanced biological phosphorus removal and biological nitrogen removal use specialized microbial communities to convert dissolved nutrients into forms that can be separated from treated water, limiting eutrophication in receiving waters.

Emerging contaminants such as pharmaceuticals, personal care products, and hormones require advanced oxidation processes, activated carbon adsorption, and specialized biological pathways. Research also examines antibiotic resistance genes and their control in treatment systems.

A major trend is moving from waste disposal to resource recovery. Anaerobic digestion produces biogas from sludge, contributing renewable energy. Processes are being developed to recover phosphorus and nitrogen as fertilizers and to reuse treated water in agriculture, industry, and groundwater recharge.

Ongoing work integrates digital monitoring, sensors, and modeling to improve process control, reduce energy use, and adapt treatment strategies to climate variability and growing urban populations.