MLSS and MLVSS testing - mixed liquor suspended solids and mixed liquor volatile suspended solids (waste water)
Introduction
In the realm of wastewater treatment, striking the right balance between effective pollutant removal and sustainable processes is essential for protecting our environment. To achieve this, wastewater treatment plants rely on advanced techniques like the Mixed Liquor Suspended Solids (MLSS) and Mixed Liquor Volatile Suspended Solids (MLVSS) testing. These tests play a crucial role in assessing the health and efficiency of biological treatment systems, offering valuable insights into the overall water quality and treatment performance. In this blog, we will delve into the significance of MLSS and MLVSS testing and how they contribute to creating a cleaner and greener world.
Understanding Mixed Liquor Suspended Solids (MLSS)
MLSS refers to the concentration of suspended solids present in the mixed liquor of an activated sludge process within a wastewater treatment plant. The mixed liquor comprises microorganisms, organic matter, and inorganic particles actively involved in the biological degradation of pollutants. Accurate MLSS measurement is essential to gauge the effectiveness of the biological treatment process and ensure optimal treatment conditions.
Exploring Mixed Liquor Volatile Suspended Solids (MLVSS)
MLVSS specifically measures the concentration of volatile suspended solids within the mixed liquor. These volatile solids consist of biologically active components, such as microorganisms that consume organic matter during the treatment process. By differentiating volatile solids from total suspended solids (TSS), operators can assess the biological activity and health of the microbial community.
Risks Associated mixed liquor suspended solids and mixed liquor volatile suspended solids in wastewater
|
Risk |
Description |
|
Poor Treatment Performance |
- Low MLSS: Insufficient biomass to degrade organic matter effectively. - High MLSS: Overloading the system, leading to biomass washout. |
|
Bulking and Foaming |
- High MLSS: Excessive growth of filamentous bacteria causing poor sludge settling and carryover of solids in effluent. |
|
Sludge Settling Issues |
- High MLSS: Poor sludge settling in clarifiers, leading to high suspended solids in the treated effluent. |
|
Increased Energy Consumption |
- High MLSS: Requires more energy for aeration in the activated sludge process. |
|
Nutrient Imbalance |
- High MLSS: May cause elevated nitrogen and phosphorus levels in effluent, leading to eutrophication in receiving waters. |
|
Toxicity and Inhibition |
- High MLSS: Accumulation of toxic substances in biomass, inhibiting wastewater treatment microorganisms. |
|
Sludge Disposal Challenges |
- High MLSS: Increased sludge production, leading to difficulties in dewatering and disposal. |
Importance of testing
Testing MLSS (Mixed Liquor Suspended Solids) and MLVSS (Mixed Liquor Volatile Suspended Solids) is of paramount importance in wastewater treatment processes for several reasons:
|
Importance of Testing MLSS and MLVSS in Wastewater Treatment |
Description |
|
Process Efficiency Assessment |
Monitoring MLSS and MLVSS levels helps evaluate the effectiveness of the treatment process. High MLSS can lead to poor settling and separation of solids, reducing treatment efficiency. Low MLSS levels may indicate inadequate biomass, resulting in incomplete pollutant removal. |
|
Process Control |
MLSS and MLVSS data provide critical information for process control and optimization. Operators can adjust aeration rates, chemical dosing, and sludge wasting to maintain the desired microbial population and ensure consistent treatment performance. |
|
Sludge Settling and Clarification |
Proper sludge settling is essential to separate treated water from activated sludge. MLSS testing helps determine if the settling process is functioning correctly and identifies potential issues, such as sludge bulking, which can affect the efficiency of secondary clarifiers. |
|
Sludge Volume and Disposal |
MLSS concentration affects the volume of sludge generated during the treatment process. Higher MLSS levels lead to more sludge production, impacting disposal and handling costs. Monitoring MLSS helps optimize sludge management strategies. |
|
Biological Activity Assessment |
MLVSS measures the concentration of volatile suspended solids, indicating the amount of active and biodegradable biomass in the mixed liquor. Higher MLVSS values suggest a healthier microbial population responsible for organic matter removal, promoting better treatment efficiency. |
|
Detecting Upsets and Process Changes |
Frequent monitoring of MLSS and MLVSS allows operators to detect changes in the treatment process promptly. Sudden fluctuations or deviations can indicate process upsets, enabling corrective actions before the system's performance is significantly impacted. |
|
Compliance with Discharge Limits |
Proper management of MLSS and MLVSS ensures compliance with discharge permits and environmental regulations. Efficient pollutant removal is essential to prevent violations and potential environmental harm. |
|
Energy Efficiency |
Optimizing MLSS and MLVSS levels reduces energy consumption in aeration processes. Maintaining appropriate biomass concentration minimizes unnecessary oxygen supply, contributing to overall energy savings in the treatment plant. |
|
Predictive Maintenance |
Monitoring MLSS and MLVSS trends helps identify patterns indicating potential equipment issues or wear. Early detection of problems allows for proactive maintenance, reducing the risk of equipment failures and downtime. |
Market overview
In 2022, the global environmental testing market was valued at approximately USD 11.07 billion. Experts predict that this market will experience substantial growth with a compound annual growth rate (CAGR) of 7.8% from 2023 to 2030
Regulations and standards
The standards and regulations for MLSS and MLVSS in India are defined by the Central Pollution Control Board (CPCB). The CPCB has published the following guidelines for MLSS and MLVSS:
- MLSS concentration: The MLSS concentration should be between 1500 and 3000 mg/l.
- MLVSS/MLSS ratio: The MLVSS/MLSS ratio should be between 0.6 and 0.8.
- SVI: The SVI should be between 100 and 150 mL/g.
These guidelines are based on the best practices for wastewater treatment in India. The CPCB also publishes more specific regulations for wastewater treatment plants in different parts of India. The best way to determine the specific requirements for your plant is to contact your local pollution control authority.
Here are some of the CPCB's regulations for MLSS and MLVSS:
Therapeutic Wastewater Treatment Plant (TWTP): The MLSS concentration in a TWTP should be between 1500 and 2500 mg/l.
Municipal Sewage Treatment Plant (MSTP): The MLSS concentration in an MSTP should be between 2000 and 3000 mg/l.
Industrial Wastewater Treatment Plant (IWTP): The MLSS concentration in an IWTP should be between 2500 and 3500 mg/l
Testing methods
Gravimetric Method:
This method involves filtering a known volume of mixed liquor through a pre-weighed filter paper to separate the suspended solids. The filter is then dried and re-weighed to determine the mass of suspended solids.
For MLVSS, the same procedure is followed, but the filtered sample is first ignited in a muffle furnace to burn off volatile solids, leaving behind the MLVSS.
MLSS = (Final filter weight - Initial filter weight) / Volume of mixed liquor sample
MLVSS = (Final ignited filter weight - Initial filter weight) / Volume of mixed liquor sample
Imhoff Cone Method:
In this method, a sample of mixed liquor is allowed to settle in an Imhoff cone for a specific duration (usually 1 hour). The settled solids are then measured.
The difference between the initial and final volumes of settled solids gives the MLSS concentration.
Direct Microscopic Count:
This method involves taking a small sample of mixed liquor and examining it under a microscope. The number of microorganisms (biomass) is counted in a defined area, and the concentration is extrapolated to the entire sample volume.
Automated Instruments:
There are various automated instruments available that use optical methods to estimate the concentration of suspended solids in a mixed liquor sample. These instruments may employ turbidity or light scattering techniques.
Some modern instruments may be able to estimate MLVSS by using specific algorithms to differentiate between volatile and non-volatile suspended solids.
Eurofins role in MLSS and MLVSS testing (wastewater)
Eurofins is a global leader in providing laboratory testing and analytical services, including environmental testing for various industries, including wastewater treatment. Eurofins offers a wide range of services related to water and wastewater analysis, and they play a significant role in MLSS and MLVSS testing in wastewater treatment processes.
In the context of MLSS and MLVSS testing, Eurofins typically offers the following services:
Laboratory Analysis: Eurofins operates state-of-the-art laboratories equipped with advanced instruments and trained personnel to perform MLSS and MLVSS testing. They receive samples from wastewater treatment plants or other clients, and their laboratories conduct the necessary tests using standardized methods or client-specific protocols.
Gravimetric Analysis: Eurofins uses gravimetric methods to determine the concentration of MLSS and MLVSS in wastewater samples. As mentioned earlier, this involves filtering known volumes of mixed liquor through pre-weighed filter papers, drying, and weighing to calculate the suspended solids' mass.
Imhoff Cone Method: Eurofins may also use the Imhoff cone method to settle wastewater samples and measure the settled solids to determine MLSS concentrations.
Automated Instruments: Eurofins may utilize modern automated instruments that use optical techniques, such as turbidity or light scattering, to estimate the concentration of suspended solids in mixed liquor samples.
Data Reporting: After completing the analysis, Eurofins provides detailed reports with the test results, including MLSS and MLVSS concentrations, along with any other relevant parameters measured during the analysis.
Consulting Services: In addition to testing, Eurofins may offer consulting services to wastewater treatment facilities. They can provide expert advice on optimizing treatment processes, interpreting test results, and making recommendations for process improvements.
Eurofins Analytical Services India, located in Bangalore, has achieved a significant milestone by receiving recognition from the US Food and Drug Administration (FDA) under the Laboratory Accreditation for Analyses of Foods (LAAF) program. This makes Eurofins the first laboratory in Asia to receive such recognition.
References
- Kumar, K., Singh, G. K., Dastidar, M., & Sreekrishnan, T. (2014). Effect of mixed liquor volatile suspended solids (MLVSS) and hydraulic retention time (HRT) on the performance of activated sludge process during the biotreatment of real textile wastewater. Water Resources and Industry, 5, 1-8. https://doi.org/10.1016/j.wri.2014.01.001
- https://www.researchgate.net/publication/275585191_Prediction_of_the_effect_of_fine_grit_on_the_MLVSSMLSS_ratio_of_activated_sludge
- https://link.springer.com/article/10.1007/s11356-017-0615-9
