MCA report includes major functional groups as % of reads as a summary for operators.
Biological wastewater treatment units contain an ecosystem where diverse organisms collaborate to treat the wastewater. These microbial communities play essential roles in removing pollutants, recycling nutrients, and maintaining water quality. While there are thousands of different Genera of microorganisms in a typical wastewater treatment plant, grouping them into functional groups helps make monitoring populations.
The following is how Aster Bio’s Microbial Community Analysis (MCA) reports key functional groups for aerobic wastewater treatment systems. The common “critical” groups are listed below:
Ammonia Oxidizing Bacteria (AOB)
AOB are pivotal players in nitrogen removal. These bacteria initiate the nitrification process by converting ammonia (NH₃) into nitrite (NO₂⁻). This transformation reduces ammonia toxicity and prepares the nitrogen for further oxidation. AOB are found in the aerobic zones of wastewater treatment systems, where oxygen is readily available to fuel their activities.
Nitrite Oxidizing Bacteria (NOB)
Working in tandem with AOB, NOB complete the nitrification process by oxidizing nitrite into nitrate (NO₃⁻). This step is crucial for preventing nitrite accumulation, which can be toxic to aquatic life. Together, AOB and NOB ensure the efficient removal of nitrogenous compounds, contributing to the ecological balance of receiving water bodies. Side note, some of the more common NOB organisms are capable of Complete Ammonia Oxidation (COMAMMOX) – so we often have higher levels of NOB than AOB in aerobic systems.
Nitrate Reducing Bacteria (NRB)
Nitrate reducing bacteria come into play during denitrification, a process that occurs in anoxic (oxygen-depleted) zones. These bacteria convert nitrate into nitrogen gas (N₂), which is released harmlessly into the atmosphere. Denitrification not only reduces nitrogen pollution but also prevents excessive algal growth in water bodies, protecting aquatic ecosystems. NRB are very common in the environment, key is getting conditions correct for these organisms to use their nitrate reducing pathways.
Phosphorus Accumulating Organisms (PAO)
Phosphorus control is another critical aspect of wastewater treatment, and PAOs are the specialists in this domain. While microorganisms use phosphate for metabolism, these microorganisms absorb and store excess phosphorus as polyphosphate during aerobic conditions. In anaerobic conditions, they release the stored phosphorus to power the uptake of soluble organic acids. Once in aerobic zones, the PAO organisms digest the adsorbed organics and store energy as polyphosphate in their cells. The uptake of excess phosphate into biosolids is why PAOs play a key role in preventing eutrophication in rivers, lakes, and oceans.
Glycogen Accumulating Organisms (GAO)
GAOs often coexist with PAOs but can be problematic in enhanced biological phosphorus removal (EBPR) systems. Unlike PAOs, GAOs focus on accumulating glycogen and do not store phosphorus effectively. Their competition with PAOs can disrupt the phosphorus removal process, making it essential to balance their populations in treatment systems. In most cases, GAO populations increase in warmer water temperatures.
Filamentous Organisms
Filamentous bacteria are crucial for maintaining the structural integrity of activated sludge. Their long, thread-like structures form a matrix that helps flocs bind together, improving the settling and separation of solids during treatment. However, an overabundance of filamentous bacteria can lead to sludge bulking, impacting the efficiency of treatment plants. Most of our common filaments are triggered by low D.O., high organic acids, sulfides, low F/M, and in cases of low nutrients (usually industrial).
Foaming Organisms
Foaming organisms, such as certain types of Nocardia and Microthrix, can cause operational challenges in wastewater treatment plants. These bacteria produce excessive foam, which can hinder aeration and clog equipment. Identifying and controlling foaming organisms is essential to ensure smooth plant operations and maintain treatment efficiency.
Achieving the Dynamic Balance
The success of wastewater treatment relies on a dynamic balance among these microorganisms. By using traditional monitoring along with newer technologies, operators can optimize environmental conditions, and address issues like sludge bulking and foaming. These efforts ensure the harmonious coexistence of microbes and the effective removal of pollutants.