Most activated sludge systems use F/M (Food/Microorganisms) for system control. While not perfect, it is very useful for adjusting wasting rates and monitoring system performance.  The most common formula uses MLVSS as a proxy for active biomass. Since VSS tests require the use of muffle furnace and extra time, many systems use MLSS instead. Key is just to be consistent on which number you use for the M portion of the equation. 

While almost everyone has a spreadsheet for calculating F/M, I have created an online calculator for when you need quick calculations.  Calculator App

​Permanente Link to App:
https://steady-zuccutto-eb3a54.netlify.app

Conventional activated sludge (CAS) systems have been the cornerstone of wastewater treatment for decades. However, advancements in technology have introduced alternatives that offer significant advantages. Three notable systems—Moving Bed Biofilm Reactor (MBBR), Membrane Bioreactor (MBR), and Granular Activated Sludge (GAS)—are gaining popularity due to their enhanced efficiency, robustness, and sustainability. All systems work by supporting higher biomass concentrations than seen in conventional activated sludge. This post explores the benefits of these modern wastewater treatment technologies over conventional activated sludge systems.

Moving Bed Biofilm Reactor (MBBR)

• Efficient Biomass Retention: MBBR systems use plastic carriers to support biofilm growth, allowing for a higher concentration of biomass compared to CAS systems. This results in more efficient pollutant removal.
• Reduced Footprint: Due to the higher biomass concentration, MBBR systems require smaller reactor volumes, making them ideal for space-constrained locations.
• Operational Stability: MBBR systems are less sensitive to fluctuations in influent quality and hydraulic loading, providing more stable treatment performance.
• Low Maintenance: The media sloughs excess biomass as needed which simplifies operation and maintenance, reducing the risk of clogging and the need for frequent cleaning.
• Energy Efficiency: 
  
  

​Membrane Bioreactor (MBR)

• Superior Effluent Quality: MBR systems combine biological treatment with membrane filtration, producing high-quality effluent with low levels of suspended solids, bacteria, and pathogens.
• Space-Efficient Design: The integration of membranes allows for compact system design, making MBRs suitable for urban and decentralized applications.
• Flexibility: MBR systems can handle variable influent loads and concentrations, ensuring consistent performance even under challenging conditions.
• Enhanced Biomass Retention: The use of membranes in MBR systems enables high biomass concentrations, improving the overall treatment efficiency and reducing sludge production.
  
  

Granular Activated Sludge (GAS)

• High Settling Velocity: GAS granules have a higher settling velocity compared to conventional flocs, allowing for more efficient solid-liquid separation and reducing the need for large settling tanks.
• Enhanced Nutrient Removal: The unique structure of GAS granules promotes the coexistence of aerobic and anaerobic zones, facilitating simultaneous nitrification-denitrification and phosphorus removal.
• Compact System: The high biomass concentration in GAS systems allows for smaller reactor volumes, making them suitable for space-limited installations.
• Improved Stability: GAS systems exhibit high resilience to shock loads and toxic compounds, maintaining stable performance under varying operational conditions.

Microthrix parvicella is a filamentous bacterium that causes bulking and foaming in activated sludge systems. It becomes a bigger problem in winter months for several reasons:
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• Temperature Sensitivity: Microthrix parvicella thrives at lower temperatures, which are common in winter. As temperatures drop, the metabolic activities of other bacteria slow down, giving it a competitive advantage.
• Reduced Settling Rates: The filamentous nature of Microthrix parvicella leads to poor settling in the secondary clarifiers. In winter, the slower metabolic rates of other bacteria exacerbate this issue, resulting in increased sludge volume and poor effluent quality.
• Foaming Issues: It is one of the bacteria capable of growth on Fats, Oils, Grease (FOG)  producing hydrophobic foam, which can lead to operational problems in aeration basins and secondary clarifiers. The cold weather can make it more difficult to control and remove this foam.
• Bulking Problems: When over abundant, filaments lead to bulking, where the sludge fails to compact in the clarifier bed. This is particularly problematic in winter when the overall biological activity is reduced, making it harder to manage the sludge.

Mitigating Microthrix parvicella foaming involves several strategies:

• Optimize FOG Removal: Reducing fats, oils, and grease (FOG) in the influent also reduces  Microthrix parvicella's food source. This can be achieved through improved pretreatment processes such as grease traps and skimmers.
  
• Maintain Proper Aeration: Ensuring adequate oxygen levels in the treatment process also favors development of healthy floc forming biomass. Regular monitoring and adjustment of aeration rates are essential.
  
• Chemical Dosing: The use of chemicals for disinfection (targeting filaments via oxidation) can help control the growth of filamentous bacteria. However, this approach should be used with caution to avoid negative impacts on the overall treatment process especially in winter months.
  
• Sludge Management: Proper sludge handling and disposal practices can prevent the accumulation of filamentous bacteria. Regular sludge wasting and maintaining appropriate sludge age are important factors.
  
• Foam Control Agents: The application of foam control agents, such as silicone-based antifoams, can help reduce foam formation and improve operational efficiency.
  
• Surface Wasting: Removing foam and sludge from the surface of the aeration basin can help control foaming organisms such as M. parvicella and Nocardia forms.

​Bioremediation has been a popular method to clean polluted soils since the 1980s. Utilizing the natural ability of microorganisms to detoxify and degrade pollutants, bioremediation can often be done at a lower cost while also being less damaging to the environment. Here are some of the most common techniques:  

• Bioventing:
  • How it works: Air is pumped into the subsurface to increase oxygen levels, stimulating the growth of naturally occurring microbes that break down contaminants.  
  • Best for: Volatile organic compounds (VOCs) like gasoline and solvents.  

 

• Biosparging:
  • How it works: Similar to bioventing, but air is injected under pressure to enhance the distribution of oxygen within the soil.  
  • Best for: VOCs, especially in deeper soil layers.

 

• Landfarming:
  • How it works: Contaminated soil is excavated and spread onto prepared beds. Nutrients and moisture are added to encourage microbial activity.  
  • Best for: Hydrocarbon contamination (like oil spills).  

 

• Composting:
  • How it works: Contaminated soil is mixed with organic materials (like manure or wood chips) to create a controlled environment for microbial degradation.
  • Best for: A wide range of contaminants, including pesticides and some metals.
    
    
• Bioreactors:
  • How it works: Contaminated soil is treated in a contained environment (like a tank or vessel). This allows for better control of environmental conditions (temperature, moisture, nutrient levels).
  • Best for: Highly contaminated soils or those with specific contaminant types.
    
    
• Phytoremediation:
  • How it works: Plants are used to absorb, accumulate, or degrade contaminants.  
  • Best for: Metals, some organic compounds, and radionuclides.
    
    

Key Considerations:

• Type of Contaminant: The specific type and concentration of contaminants will determine the most suitable technique.
• Soil Characteristics: Factors like soil type, moisture content, and depth of contamination influence the effectiveness of different methods.
• Cost: Bioremediation can be cost-effective, but the specific costs vary depending on the technique, site conditions, and the extent of contamination.  
• Time: Bioremediation can take time to achieve desired results, sometimes months or even years.  
  
  

Bioaugmentation vs Biostimulation Options
Bioaugmentation works by adding select microbes to rapidly establish an active biomass suited for contaminants present and local environmental conditions. Biostimulation uses nutrients and bioremediation methods while relaying on an indigenous biomass to develop which can remediate the soil. The main benefits from using bioaugmentation is the ability to reduce active bioremediation project time and reduce potential variation in treatment outcomes.

Lab Tray Study with PAH Contamination - Bioaugmentation versus Biostimulation

​Staffing limits are becoming a factor in how much analytical can be done onsite in many treatment systems. I have been working with several smaller systems with staff that services multiple smaller treatment plants. For operations side on biological treatment sections, it is good to know what data helps in case troubleshooting is needed. What tests must be run and how often frequently depend on influent variation, treatment system design capacity, equipment operating efficiently, and other local factors. Here are what I consider the most vital onsite tests and how they help you make operational decisions.

Lagoon Systems

• High Frequency/Daily
  • Observe - water color, foam, and other visual clues
  •  Temperature, D.O., pH - and check probes to ensure no malfunctions are happening
• Important but not necessarily daily
  • BOD/COD
  • Nutrients (ammonia, phosphate)
  • Oxygen Uptake Rate (OUR)
  • Basic microscopic exam - often centrifuge lagoon sample first for better protozoa observation

Basic Activated Sludge

• High Frequency/Daily
  • Observe - water color, foam, and other visual clues
  • Temperature, D.O., pH - and check probes to ensure no malfunctions are happening
  • SV30 - use same vessel each time 
  • Check recycle and wasting rates
  • Clarifier bed depth 
• Important but not necessarily Daily
  • BOD/COD
  • Nutrients (ammonia, phosphate)
  • Oxygen Uptake Rates (OUR)
  • MLSS/MLVSS - good to know both, but MLSS can be used for adjustments and is faster
  • Microscopic exam - phase contrast helps to count filamentous organisms in systems subject to bulking
  • Calculate F/M, MCRT, SVI, SOUR - watch trends and variation here

For help in conducting Microscopic Exam - I have created a "Bug Poster" - it helps you identify common indicator organisms such as protozoa in biological treatment units. 
​https://asterbio.com/bug-poster/

Grease, primarily from residential and commercial kitchens, can cause significant operational issues if not managed properly. This post reviews educating the public on the grease problem, emphasizes restaurant grease trap maintenance, outlines collection system pretreatment programs, and explain how bioaugmentation can assist in grease degradation within biological treatment plants.

Understanding the Grease Problem
Grease, fats, and oils are byproducts of cooking and food preparation. When these substances enter the wastewater system, they tend to solidify and create blockages, leading to backups, overflows, and increased maintenance costs. The impact of grease on wastewater treatment plant comes from the fact that insoluble grease/fatty acids take longer to decompose biologically than other soluble organics and nuisance organisms such as M. parvicella and Nocardia forms (foaming) thrive on grease.

Step 1 - Educating the Public (Keep Grease Out)
Public awareness is the first line of defense against grease-related issues. Programs to educate residents and businesses about the proper disposal of grease helps to reduce the amount entering the wastewater system. Simple actions, such as wiping grease from dishes before washing and disposing of it in the trash, can make a substantial difference. Community outreach programs, informative brochures, and social media campaigns are effective tools for spreading this message.

Step 2 - Restaurant Grease Trap Education & Maintenance
Restaurants and other food service establishments are major contributors to grease in the wastewater system. Proper maintenance of grease traps is crucial to prevent grease from entering the sewer lines. I find it interesting that many restaurant workers do not know about the grease trap and how odors blamed on "dumpsters/trash" is actually coming from a poorly maintained trap. Regular cleaning and inspection ensure that they function correctly. Establishments should also train their staff on best practices for grease management and disposal. By adhering to these practices, restaurants can play a significant role in reducing the grease load on wastewater treatment plants. Grease trap microbial products are often subject to debates regarding their ability to reduce FOG entering the collection system. Data collected in studies has demonstrated that well designed grease trap microbial blends when dosed appropriately along with normal inspection/maintenance helps with trap maintenance and lower grease/long chain fatty acids entering the collection system.

Step 3 - Collection System Pretreatment
Pretreatment programs are essential for managing grease before it reaches the wastewater treatment plant. These programs involve installing and maintaining equipment designed to capture and remove grease from the wastewater. Regular inspections and maintenance of the collection system can prevent grease build-up and ensure the smooth operation of the treatment facility. Pretreatment programs also include regulatory measures, such as permits and inspections, to enforce compliance among businesses that discharge grease-laden wastewater. In problem sections of collection systems, you can use added biological cultures to reduce grease accumulation in pipes and lift stations. A side benefit is these grease control programs can also reduce odors and H2S. These cultures must be added upstream of the problem section and allowed to form a beneficial biofilm on pipe walls. In effect, you are transforming the pipe walls and lift station into a biological pretreatment section.

Can Bioaugmentation Aid in Grease Degradation at the Biological Treatment Plant?
Despite best efforts to minimize grease entry into the wastewater system, some grease inevitably makes its way to the treatment plant. Here, bioaugmentation can play a role in enhancing grease degradation. Bioaugmentation involves introducing specific microorganisms into the biological treatment process. These microorganisms accelerate the degradation of fats, oils, and grease, improving the overall performance of the treatment plant.