Biological Strategies for Tackling Elevated BOD in Lake Waters

Biochemical Oxygen Demand (BOD) is a critical indicator of organic pollution in lake ecosystems. When BOD levels exceed normal thresholds, it signals an excessive influx of biodegradable organic matter—originating from domestic sewage, industrial wastewater, or agricultural runoff. 

This triggers a cascade of ecological problems: heterotrophic microorganisms proliferate, dissolved oxygen is rapidly depleted, water quality deteriorates, fish kills occur, and eutrophication accelerates. Compared to physical interception and chemical precipitation, biological treatment methods offer distinct advantages—lower cost, minimal secondary pollution, and strong ecological compatibility—making them the preferred technical pathway for managing BOD exceedances in lakes.

Microbial Remediation: The Core Strategy

Microbial remediation is the cornerstone of BOD control. The underlying principle is straightforward: specific microorganisms—bacteria, fungi, and their consortia—metabolise organic pollutants, converting them into carbon dioxide, water, and inorganic salts. 

The selection and immobilisation of functional strains are key technical considerations. Research has shown that specially screened and acclimatised strains, such as Bacillus subtilis, can be implanted onto carrier surfaces to form biofilms approximately 0.5 to 0.8 millimetres thick. As polluted water flows through these carriers, the biofilm microorganisms efficiently adsorb and decompose organic matter.

For lakes with severely contaminated influent water—those failing to meet Class V standards of GB 3838‑2002—the immediate application of microbial preparations can rapidly degrade soluble organics, eliminate odours, and improve water transparency. In practical engineering, combined systems such as "microbial remediation tank plus adsorption tank" have proven effective; with water circulating through the fillers, BOD and other indicators decline significantly within hours of treatment.

Effective Microorganism (EM) technology has also gained traction as an eco-friendly approach. EM utilises naturally occurring beneficial microbes—often a mixture of anaerobic and aerobic species—to purify and restore aquatic environments. Studies have applied EM-Activated Solution, TeMo Decomposer, and Lactic Acid Bacteria to enhance lake water quality, with EM‑based rehabilitation contributing substantially to the restoration of degraded aquatic habitats.

Phytoremediation and Plant‑Microbe Synergy

Aquatic plants play an indispensable role in BOD reduction. Their mechanisms include direct interception of organic particles by root systems, flocculation through root exudates, and synergistic degradation by rhizosphere microorganisms. Floating Treatment Wetlands (FTWs), constructed with emergent aquatic plants, represent a typical phytoremediation approach. Constructed wetlands, in particular, are widely applied; under low influent concentrations, they can achieve substantial BOD removal.

Plant‑microbe synergistic systems further enhance treatment efficiency. By combining composite nitrogen‑removing bacterial agents with ecological pellets or modified mineral materials, water quality improves while submerged macrophyte growth is promoted, establishing a beneficial ecological cycle. Algae‑bacteria consortia leverage the symbiotic metabolic relationship between microalgae and bacteria to achieve simultaneous organic degradation and nutrient recovery, aligning with low‑carbon development principles.