Biological Methods for Reducing Total Phosphorus in Water

Excessive phosphorus in water bodies is a major cause of eutrophication, leading to ecological imbalances and health risks. Biological phosphorus removal (BPR) has emerged as a sustainable and cost-effective solution. This article outlines key biological strategies for mitigating phosphorus pollution.

1. Enhanced Biological Phosphorus Removal

EBPR relies on polyphosphate-accumulating organisms (PAOs), which absorb phosphorus beyond their metabolic needs under alternating anaerobic and aerobic conditions. In anaerobic environments, PAOs release stored phosphorus and consume volatile fatty acids (VFAs) to synthesize polyhydroxybutyrate (PHB). When oxygen is reintroduced, they metabolize PHB for energy, absorbing excess phosphorus as intracellular polyphosphates. The phosphorus-rich biomass is then removed via sedimentation or filtration.

2. Novel Microbial Consortia

Beyond traditional PAOs, recent studies highlight Tetrasphaera bacteria as potent phosphorus removers. These microbes can simultaneously degrade nitrogen and phosphorus while utilizing diverse carbon sources (e.g., glucose, amino acids). In one trial, enriching Tetrasphaera with targeted inhibitors increased phosphorus removal efficiency by 85% and enabled phosphorus recovery from sludge.

3. Bioelectrochemical Systems

Bioelectrochemical technologies, such as microbial fuel cells, use electroactive biofilms to remove phosphorus synergistically with electricity generation. These systems eliminate the need for separate reactors or external aeration, achieving up to 55% phosphorus removal alongside nitrogen degradation.

4. Bio-Induced Phosphorus Crystallization

Microorganisms like yeast can secrete extracellular polymeric substances (EPS) that induce magnesium ammonium phosphate (struvite) crystallization. This method combines biological and chemical processes, allowing phosphorus recovery as a valuable fertilizer precursor.

Challenges and Outlook

Optimizing carbon source ratios (BOD:P > 40:1), maintaining strict anaerobic conditions (ORP < -150 mV), and controlling nitrate levels are critical for success. Future efforts should focus on integrating phosphorus recovery into EBPR systems, leveraging "microbial dark matter" like novel Tetrasphaera strains, and scaling bioelectrochemical methods for decentralized use.

Biological methods—from PAO-based EBPR to emerging microbial and electrochemical strategies—offer scalable pathways to reduce aquatic phosphorus while promoting resource circularity.