biodegradable dissolved organic carbon (BDOC)

Biodegradable Dissolved Organic Carbon (BDOC): Fueling Microbial Life in Water Treatment

Dissolved organic carbon (DOC) is a ubiquitous component of natural waters, playing a crucial role in aquatic ecosystems. However, not all DOC is created equal. While some forms are recalcitrant and resistant to degradation, others are readily utilized by microorganisms as a source of energy and nutrients. This readily biodegradable fraction of DOC is known as biodegradable dissolved organic carbon (BDOC).

Understanding BDOC

BDOC is defined as the portion of TOC (total organic carbon) that is easily degraded by microbes. This means that it can be consumed by microorganisms, leading to the production of carbon dioxide (CO2) and other byproducts.

Why is BDOC important in water treatment?

• Nutrient source for microbes: BDOC provides a readily available food source for beneficial microbes in water treatment systems. These microbes play a crucial role in various treatment processes, such as:

  • Biological nutrient removal: Microbes utilize BDOC to remove nutrients like nitrogen and phosphorus, preventing eutrophication and algal blooms.
  • Biofiltration: Biofilters rely on microbial activity to remove contaminants like organic matter, pathogens, and pharmaceuticals.
  • Bioaugmentation: Deliberately adding beneficial microbes to enhance the degradation of specific contaminants.

• Impact on water quality: High BDOC levels can indicate a potential for microbial growth and subsequent problems such as taste and odor issues, biofilm formation, and the production of disinfection byproducts.

• Treatment process optimization: Understanding BDOC levels allows for optimizing treatment processes by:

  • Tailoring microbial populations: Adjusting operational conditions (e.g., aeration, nutrient addition) to favor the growth of specific microbial communities.
  • Monitoring treatment effectiveness: Tracking BDOC removal can provide insights into the efficiency of biological treatment processes.

Measuring BDOC:

While there is no single standard method for measuring BDOC, various techniques are employed, including:

• Biological Oxygen Demand (BOD): This classical method measures the amount of oxygen consumed by microbes during a specific incubation period.
• Respiration measurements: Using respirometers, the CO2 produced by microbes during BDOC degradation can be measured.
• Stable isotope techniques: These methods utilize labeled isotopes to track the fate of organic carbon in microbial processes.

BDOC in different water treatment systems:

• Wastewater treatment: BDOC is crucial for the biological nutrient removal processes in wastewater treatment plants, where microbes play a vital role in removing nitrogen and phosphorus.
• Drinking water treatment: While BDOC removal is not a primary concern in drinking water treatment, understanding its role in microbial activity is important for ensuring water quality and preventing the formation of disinfection byproducts.
• Surface water treatment: BDOC levels can fluctuate depending on the source water and season, impacting the efficiency of biological treatment processes.

Conclusion:

BDOC plays a vital role in water treatment by fueling microbial activity and influencing the effectiveness of various processes. Understanding its levels and characteristics is crucial for optimizing treatment systems and maintaining high water quality. By monitoring and managing BDOC, we can ensure the efficient and sustainable operation of water treatment facilities, protecting our precious water resources.