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Wastewater Treatment: Biological
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Water Resources and Hydrological Systems, 2020
Shaikh Ziauddin Ahammad, David W. Graham, Jan Dolfing
Key operating parameters and typical values for activated sludge systems are provided in Table 1. All parameters ultimately are used to guide and pseudo-control biosolids levels, and they profoundly affect process performance. The total suspended solids in the aeration tank are known as mixed-liquor suspended solids (MLSS). This term refers to the amount of solids in a certain volume of the water (usually milligram of solids per liter). The actual biomass fraction of the solids is estimated as the solids that can be volatilized at 550°C. The volatile fraction is known as mixed-liquor volatile suspended solids (MLVSS). Therefore, MLVSS is frequently used as a proxy for the active biomass treating the waste. MLVSS ranges from about 70% to 90% of the MLSS concentration in most activated sludge systems.[6]
Aerobic Biological Oxidation
Published in Gaetano Joseph Celenza, Industrial Waste Treatment Process Engineering, 2019
Reactor microbiology, SRT, and cell growth rate were discussed so that the design engineer understands that biological system design does not involve a “black box” but a complex reactor design developed to assure the operator a range of conditions to control process stability and optimize treatment efficiency. This begins with a representative and convenient measure of total microorganism concentration as an operating and design indicator. Regardless of the level of design sophistication, the system mixed liquor volatile suspended solids (MLVSS) is commonly considered a direct measure of the biological microorganisms, its mass quantity adjusted to the feed BOD (or COD) to achieve the required treatment effectiveness. However, when suspended solids become the primary, or the sole, reactor sizing consideration, other design objectives may be neglected; such as Selection of an SRT, along with sludge management criteria, to fix the cell growth rate(s) governing specific viable reactor microorganismsSelection not only of a single reactor microorganism concentration to balance feed substrate, but an operating range to assure operating flexibilityAvoiding the introduction of high feed nonbiodegradable components, which reduces the reactor active microorganism concentration
Industrial Wastewater Treatment
Published in Saleh S. Al Arni, Mahmoud M. Elwaheidi, Concise Handbook of Waste Treatment Technologies, 2020
Saleh S. Al Arni, Mahmoud M. Elwaheidi
The concentration of suspended solids in the mixed liquor (Mixed Liquor Suspended Solids, MLSS) and the activated sludge concentration in mixed liquor (amount of organic or volatile suspended solids MLVSS) are usually measured in milligrams per liter (mg/l). After the treatment of wastewater in the aeration tank, the mixed liquor passes into the secondary clarifier (sedimentation tank), where solid–liquid separation process takes place by sedimentation (the solid is known as activated sludge). For more details, see Section 10.5 on mass balance.
Influence of activated sludge dissolved oxygen concentration on a membrane bioreactor performance with intermittent aeration
Published in Journal of Environmental Science and Health, Part A, 2021
Alicia Checa Fernández, Luz Marina Ruiz, Jorge Ignacio Pérez, Miguel Gómez
The MLvSS/MLSS ratio values (Table 1) were lower than the most frequent values in MBR systems.[20] A low MLvSS/MLSS ratio indicates inert material accumulation, sludge stabilization, and a decrease in biological activity.[25,26] An increase in the SRT causes a considerable decrease in the substrate/biomass ratio (F/M), meaning lower substrate availability for the microorganisms of the activated sludge. If the F/M ratio continues to decline, the biodegradable fraction falls rapidly and the concentration of microorganisms decreases, causing the activated sludge to work under endogenous conditions. Therefore, endogenous respiration and sludge mineralization are promoted in such a way that the concentration of MLvSS may be reduced during the process, causing the MLvSS/MLSS ratio to be lower than usual values. High temperature and high HRT favor this trend.[21] However, taken individually the operational variables did not show significant effects on the MLvSS/MLSS ratio (Table 2). Operational conditions bring the biomass to endogenous conditions,[25] so that further increases in the operational variables do not change the MLvSS/MLSS ratio, since the biodegradable fraction is practically depleted.
The design for wastewater treatment plant (WWTP) with GPS X modelling
Published in Cogent Engineering, 2020
The combined process oxidizes a high proportion of the influent organics relative to the NH3-N concentration. In combined carbon oxidation-nitrification processes the ratio of BOD (biological oxygen demand) to TKN is greater than 5, whereas in separate processes the BOD to TKN ratio in the second stage is greater than 1 and less than 3. Total Kjeldahl Nitrogen (TKN) is a parameter used to measure organic nitrogen and ammonia. The TKN content of influent municipal wastewater is characteristically between 35 and 60 mg/L. TKN is a regular parameter that indicated the total concentration of organic nitrogen and ammonia. The ratio of BOD5 to TKN can be used as an indicator for efficiency of removal nitrogen and providing useful information in the rate of biodegradability in WWTP design. The term MLSS means (Mixed liquor suspended solids) is the concentration of suspended solids, in an aeration tank during the activated sludge process, which occurs during the treatment of waste water. The F/M ratio is a measure of the amount of food, or BOD, that is given to the microorganisms in the aeration tank. Additionally, MLVSS is defined as mixed liquor volatile suspended solids. MVLSS is generally defined as the microbiological suspension in the aeration tank of an activated-sludge biological wastewater treatment plant or it is represented the concentration of biomass in the activated sludge. The MLVSS is calculated as shown in Table 9. The hydraulic retention time (HRT) in wastewater treatment plant is a measure at an average length of time holding the wastewater in a tank. In addition, the biomass yield is defined as the ratio of the amount of biomass produced to the amount of substrate consumed (g biomass/g substrate). Moreover, in most aeration treatment systems, it is necessary to calculate the detention time is necessary in order for the microorganisms in the aeration system to absorb, adsorb and remove the contaminants (bacteria food) in the wastewater. Other calculations like sludge age, sludge produce and sludge produce in term of TTS are explained in Table 9 as a part of the calculations of the design of aeration tank.