Effect of Activated Sludge Processes on Secondary Settling Tank Efficiencies

1988 ◽  
Vol 20 (4-5) ◽  
pp. 153-163 ◽  
Author(s):  
Z. Koníček ◽  
J. Burdych
Keyword(s):  
Settling Tank ◽  
Standard Test ◽  
Density Current ◽  
Secondary Settling ◽  
Final Settlement ◽  
Activated Sludge Processes ◽  
Harmful Effects ◽  
Current Zone ◽  
Better Than ◽  
Number Of Particles

Some calculations and experimental work on the turbulence in aeration tanks using different aeration systems and its effect on floc cohesion are presented. Vigorous aeration causes floc dispersion and it can be quantified in standard test conditions using velocity gradient calculations and comparing these with the numbers of particles in the supernatant liquor after 30 minutes settlement of the sludge. Tests on final settlement tanks indicated that the density current is of prime importance and that the harmful effects of this can be overcome by installing deep inlets and arranging to have the outlet weir inset and as near to the inlet as possible. Mixing calculations also indicated that circular tanks are more efficient than rectangular and that if the latter were used transverse flow is better than longitudinal flow. A test on a full scale plant indicated that flocculation occurred in the density current zone of the final tank so that the number of particles in the supernatant decreased to an extent similar to that produced by mild agitation.

A one-dimensional model for a secondary settling tank including density current and short-circuiting

1995 ◽  
Vol 31 (2) ◽  
pp. 215-224 ◽  
Author(s):  
René Dupont ◽  
Claus Dahl
Keyword(s):  
Settling Tank ◽  
Treatment Plant ◽  
Density Current ◽  
One Dimensional ◽  
Solids Concentration ◽  
Primary Particles ◽  
Flux Model ◽  
Secondary Settling ◽  
Soluble Components ◽  
Sludge Concentration

This paper presents a dynamic one-dimensional flux model for the secondary settling tank which is suitable for use with the latest innovations in models for activated sludge tanks, and which takes into account observed effects of density current and short-circuiting. The components of the influent to the settling tank are divided into three fractions. Soluble components, non-settleable particulate components (primary particles), and settleable particulate components. (macroflocs). Soluble components and primary particles are considered to follow the hydraulic flow in the settling tank. The transport of macroflocs in the settling tank is modelled according to the traditional flux theory on a layer model of the settling tank extended with a model for density current and short-circuiting. For modelling of the density current in the inlet region of the settler a dynamic inlet height is introduced. The short-circuiting is modelled by the introduction of a factor which accounts for the dilution in the suspended solids concentration at the bottom of the settling tank down to the concentration in the return sludge flow. Settling velocities of the macroflocs for both free and hindered sedimentation are measured, and a new model for the settling velocity is proposed. The model is validated with data from the wastewater treatment plant Lynetten, Copenhagen, Denmark. It was found that the suspended sludge concentration profile and the suspended sludge concentration in the return sludge were predicted well with the model.

An equation for the empirical design of anoxic zones used to eliminate rising sludges at nitrifying activated sludge plants

1996 ◽  
Vol 33 (3) ◽  
pp. 185-194 ◽  
Author(s):  
M. Sarioglu ◽  
N. Horan
Keyword(s):  
Activated Sludge ◽  
Empirical Equation ◽  
Nitrate Nitrogen ◽  
Critical Concentration ◽  
Settling Tank ◽  
Limited Information ◽  
Batch Experiments ◽  
Anoxic Zone ◽  
Secondary Settling ◽  
Anoxic Zones

Anoxic zones are designed for the removal of nitrogen in nitrifying activated sludge plants. This can be carried out either to achieve a nitrogen discharge consent or to eliminate the problem of rising sludges. The rising sludge problem is mostly encountered in medium and small size plants in warm conditions and there is limited information as to the appropriate design of anoxic zones to protect against rising sludges in the secondary sedimentation tanks. Therefore a series of batch experiments were undertaken in order to establish the critical concentration of nitrate-nitrogen which causes rising sludge in the secondary settling tank and the effect of environmental factors such as temperature (15°C to 30°C) and residual carbon source (100 to 600 mg/1 COD) were examined. Based on the results of these experiments an empirical equation was presented which can be used to size an anoxic zone to eliminate rising sludges. The application of this equation at full-scale plants is discussed.

scholarly journals Plasticization Effect of Bio-Based Plasticizers from Soybean Oil for Tire Tread Rubber

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 623 ◽  
Author(s):  
Haoshu Xu ◽  
Tao Fan ◽  
Neng Ye ◽  
Weidong Wu ◽  
Daye Huang ◽  
...  
Keyword(s):  
Soybean Oil ◽  
Crosslink Density ◽  
Plasticization Effect ◽  
Additive Content ◽  
Resistance Property ◽  
Modified Soybean Oil ◽  
Aging Resistance ◽  
Harmful Effects ◽  
Tread Rubber ◽  
Better Than

Modified soybean oil (MSO) is synthesized from soybean oil (SO) and sulfur, aiming to reduce the double bond quantity of SO and avoid harmful effects on the crosslink density and mechanical properties of rubber. MSO modified with different weight percentages of sulfur is then used to plasticize tire tread rubber (TR). It is found that the crosslink density and modulus of MSO- plasticized rubber are significantly improved compared with that of SO-plasticized TR. MSO modified with 6 wt % sulfur (MSO-6%) exhibits the best plasticization effect on TR, thus, the plasticization effect of MSO-6% on TR was further studied by adjusting its additive content. Thereafter, the Mooney viscosity, Payne effect, mechanical property of different amount of MSO-6% plasticized TR are studied to investigate their plasticization effect. At the same additive content of plasticizer, the plasticization effect of MSO-6% and a commonly used aromatic hydrocarbon plasticizer (AO) is compared to determine the potential application of MSO on tire tread rubber. It is found MSO shows similar plasticization effect on TR compared with AO. More important, the aging resistance property and wear resistance property of MSO-6% plasticized rubber are better than those of AO-plasticized rubber. Therefore, MSO-6% is a promising bio-based plasticizer for tire tread rubber.

Assessing the Performance of a Secondary Settling Tank by Means of flow Modeling

2006 ◽  
Vol 2006 (5) ◽  
pp. 6695-6706
Author(s):  
R. Garcia ◽  
D. Bessette ◽  
B. Post ◽  
B.W. Roff
Keyword(s):  
Settling Tank ◽  
Flow Modeling ◽  
Secondary Settling

Retrofitting and Operation of Small Extended Aeration Plants for Advanced Treatment – Some Experiences in Japan

1993 ◽  
Vol 28 (10) ◽  
pp. 377-385 ◽  
Author(s):  
K. Moriyama ◽  
M. Takahashi ◽  
Y. Harada
Keyword(s):  
Phosphorus Removal ◽  
Settling Tank ◽  
Phosphorus Release ◽  
Biological Phosphorus Removal ◽  
Removal Process ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Oxic Zone ◽  
Secondary Settling ◽  
Biological Phosphorus

Some experiences concerning a retrofit design and operation for nutrients removal in small extended aeration plants are presented. In this study a new biological phosphorus removal process as well as a biological nitrogen removal process based on a sequential oxic-anoxic-oxic process is investigated. The denitrification in the first oxic zone has a high removing effect for nitrogen, and the oxidation reduction potential (ORP) value and dissolved oxygen (DO) concentration are useful indexes to maintain the optimum conditions of the first oxic zone for simultaneous denitrification. It is verified that the simultaneous denitrification can alleviate the alkalinity deficit problem against full nitrification by a stoichiometric analysis of alkalinity throughout the entire process. Additionally, a biological phosphorus removal process which uses a sludge blanket zone of secondary settling tank for phosphorus release is proposed.

scholarly journals Specific cost modelling for secondary treatment of wastewater

2021 ◽  
Vol 263 ◽  
pp. 04065
Author(s):  
Nikolay Makisha
Keyword(s):  
Wastewater Treatment ◽  
Settling Tank ◽  
Membrane Bioreactors ◽  
Conventional Activated Sludge ◽  
Cost Modelling ◽  
Cost Item ◽  
Treatment Facilities ◽  
Secondary Settling ◽  
Technological Treatment ◽  
Technological Modeling

The article is devoted to the study of model cost indicators of wastewater treatment facilities as one of the factors for ensuring sustainable development. It is noted that the greatest contribution in terms of cost formation is provided by the stage of biological wastewater treatment. As part of the study, a techno-economic simulation was conducted to compare two technological treatment schemes: conventional activated sludge scheme in aeration reactor and secondary settling tank, and treatment by means of membrane bioreactors. In the course of technological modeling, the concentrations of pollutants after treatment were obtained and compared for each of the schemes, as well as the values of possible harm to water bodies were calculated. Within the framework of cost modeling, capital and operating costs were obtained for the two variants, and key differences in their formation were analyzed. It is noted that the classical cleaning scheme requires the construction of a larger volume of structures, while for schemes with a membrane bioreactor, a significant cost item is the purchase of the actual membrane modules, but as the system performance increases, the share of these costs decreases.

scholarly journals Comparison of respiratory protection during workload between different wearing methods of replaceable particulate respirators and powered air-purifying respirators

2021 ◽  
Author(s):  
Hiroka Baba ◽  
Kazunori Ikegami ◽  
Shingo Sekoguchi ◽  
Taiki Shirasaka ◽  
Hajime Ando ◽  
...  
Keyword(s):  
Resting State ◽  
Health Problems ◽  
Protective Equipment ◽  
Respiratory Protection ◽  
The Difference ◽  
Better Than ◽  
Number Of Particles

This study evaluated the difference in respiratory protection between replaceable particulate respirators (RPRs) and powered air-purifying respirators (PAPRs), with different wearing methods during workload. Participants wore RPRs or PAPRs in the ways that workers wore them in actual workplaces. We measured the number of particles inside and outside the respiratory protective equipment (RPE) during workload for each wearing variation. The fit factor (FF) of RPRs in the workload state was significantly lower than that in the resting state, indicating inadequate respiratory protection. In contrast, the FF of PAPRs during workload was significantly lower than that at rest; however, respiratory protection was maintained. PAPR did not show a significant decrease in FF owing to the wearing variations during workload. In conclusion, PAPRs were found to be superior to RPRs in terms of respiratory protection. PAPRs are better than RPRs for workers who have to wear RPE inappropriately due to health problems.

scholarly journals Electric Vehicle Relay Lifetime Prediction Model Using the Improving Fireworks Algorithm–Grey Neural Network Model

2020 ◽  
Vol 10 (6) ◽  
pp. 1940 ◽  
Author(s):  
Xuelian Pang ◽  
Zhuo Li ◽  
Ming-Lang Tseng ◽  
Kaihua Liu ◽  
Kimhua Tan ◽  
...  
Keyword(s):  
Neural Network ◽  
Electric Vehicle ◽  
Network Model ◽  
Neural Network Model ◽  
Standard Test ◽  
Running Speed ◽  
Test Function ◽  
Fireworks Algorithm ◽  
Convergence Performance ◽  
Better Than

The relay reliability has an impact on the reliability of the entire electric vehicle system. This paper contributes to propose the improving fireworks algorithm optimizing the grey neural network model to predict the relay lifetime. This paper shows how the mutation operation and mapping operation in the fireworks algorithm are used to improve the convergence ability and running speed; the convergence performance and running speed of improved fireworks algorithm are tested with standard test function and compared with fireworks algorithm; and the grey neural network model–improved fireworks algorithm is used to predict the relay life and compared with grey model, grey neural network, and grey neural network model–fireworks algorithm. The results show that the convergence accuracy of the improved fireworks algorithm is better than the fireworks algorithm. The running time of improved fireworks algorithm is the shortest; the improved fireworks algorithm–grey neural network model has the best prediction effect and the root mean square error value is 6.75% smaller than the fireworks algorithm–grey neural network model.

Sign in / Sign up

Export Citation Format

Share Document