Turning Poultry Wastewater Into Clean Water And Protein-Rich Biomass For Aquaculture

Can wastewater from poultry processing be treated in a way that not only protects waterways but also recovers valuable resources?

Phaisit Buaban, a Master’s student in Environmental Engineering and Management program at the Asian Institute of Technology (AIT), is exploring how a special group of light-powered microorganisms known as purple phototrophic bacteria (PPB) can help “close the loop” by treating high-strength industrial wastewater while producing nutrient-rich biomass with potential use as aquaculture feed ingredients.

Supervised by Dr. Anish Ghimire, Assistant Professor, EEM, Phaisit’s thesis“Evaluation of Anaerobic Photobioreactor Utilizing Purple Phototrophic Bacteria for the Treatment of Poultry Processing Wastewater,” investigates whether PPB can offer an energy-efficient alternative to conventional treatment, while also supporting resource recovery from nutrient-rich wastewater.

Poultry processing uses large amounts of water and generates wastewater containing organic matter and nutrients. If not effectively treated, these pollutants can contribute to oxygen depletion and nutrient pollution in receiving waters. In Thailand, industrial discharge regulations require facilities to substantially reduce organic pollution, nitrogen, and suspended solids before releasing effluent. At the same time, this wastewater contains recoverable nutrients, meaning it can be viewed not only as a disposal challenge but also as a potential resource when treated using appropriate technologies.

To support the study, the research team collected wastewater samples from a poultry processing factory near Bangkok and confirmed that the wastewater contained high concentrations of organic matter and nutrients, making it a challenging wastewater stream that requires effective treatment before discharge.

Purple phototrophic bacteria (PPB) offer a different pathway. These microorganisms can grow without oxygen and use light as an energy source, allowing them to capture carbon, nitrogen, and phosphorus as they build new cells. In practice, this means PPB can simultaneously remove pollutants while generating protein-rich biomass, opening possibilities for applications such as biofertilizer or aquaculture feed ingredients.To test PPB under realistic conditions, the research team built and operated an anaerobic photobioreactor—a closed treatment system that provides the anaerobic environment PPB prefer, along with infrared light to support their growth. The setup also included units to separate and recirculate bacterial biomass, helping retain the most effective microorganisms in the system for continued treatment.

Anaerobic Photobioreactor Setup at the Ambient Laboratory, Environmental Engineering and Management Program, Faculty of Civil and Environmental Engineering, AIT

The photobioreactor system was operated for more than 116 days to assess how effectively PPB could treat the wastewater under different setups. The study compared a basic approach that recirculates biomass through a settling tank with an enhanced setup that uses a ceramic membrane to retain more beneficial bacteria in the system.

Key findings from the study included:

• The PPB system removed a large share of pollutants from poultry processing wastewater- about a 90% reduction (measured as COD) in organic pollution under its best-performing conditions.
• Adding a ceramic microfiltration membrane helped the reactor hold onto more PPB biomass, which supported more consistent treatment performance, even at shorter hydraulic retention times.

The treated effluent was also compared with Thailand’s industrial discharge requirements. Results showed that the system can achieve compliant effluent under stable operation, with the membrane-coupled setup providing the most reliable compliance.

A key advantage of PPB is that treatment can also produce useful biomass. In this study, the harvested PPB biomass contained approximately 55-59% crude protein (dry cell weight), indicating strong potential for future development as a protein-rich ingredient for applications such as aquaculture feed, supporting a more circular approach to wastewater management.

The study demonstrates how purple phototrophic bacteria (PPB) could support more sustainable industrial wastewater management by combining effective treatment with biomass generation for potential reuse. As for the next steps, further work can explore scale-up, long-term operation, and practical pathways for the safe use of recovered PPB biomass in real-world circular-economy applications.