Influence of sludge properties and hydraulic loading on the performance of secondary settling tanks - full-scale operational results

2004 ◽  
Vol 50 (7) ◽  
pp. 179-186 ◽  
Author(s):  
R.J. Vestner ◽  
F. Wolfgang Günthert
Keyword(s):  
Suspended Solids ◽  
Loading Rate ◽  
Settling Tank ◽  
Full Scale ◽  
Volume Loading ◽  
Solids Concentration ◽  
Sludge Properties ◽  
And Performance ◽  
Secondary Settling ◽  
Flocculation Time

Full-scale investigations at a WWTP with a two-stage secondary settling tank process revealed relationships between significant operating parameters and performance in terms of effluent suspended solids concentration. Besides common parameters (e.g. surface overflow rate and sludge volume loading rate) feed SS concentration and flocculation time must be considered. Concentration of the return activated sludge may help to estimate the performance of existing secondary settling tanks.

Comparison of the 1D flux theory with a 2D hydrodynamic secondary settling tank model

2004 ◽  
Vol 50 (7) ◽  
pp. 195-204 ◽  
Author(s):  
G.A. Ekama ◽  
P. Marais
Keyword(s):  
Surface Area ◽  
Loading Rate ◽  
Settling Tank ◽  
Full Scale ◽  
Tank Model ◽  
Marked Influence ◽  
Solids Loading ◽  
Small Influence ◽  
Secondary Settling ◽  
Sloping Bottom

The applicability of the 1D idealized flux theory (1DFT) for design of secondary settling tanks (SSTs) is evaluated by comparing its predicted maximum surface overflow (SOR) and solids loading (SLR) rates with that calculated from the 2D hydrodynamic model SettlerCAD using as a basis 35 full scale SST tress tests conducted on different SSTs with diameters from 30 to 45m and 2.25 to 4.1m side water depth, with and without Stamford baffles. From the simulations, a relatively consistent pattern appeared, i.e. that the 1DFT can be used for design but its predicted maximum SLR needs to be reduced by an appropriate flux rating, the magnitude of which depends mainly on SST depth and hydraulic loading rate (HLR). Simulations of the sloping bottom shallow (1.5-2.5 m SWD) Dutch SSTs tested by STOWa and the Watts et al. SST, all with doubled SWDs, and the Darvill new (4.1 m) and old (2.5 m) SSTs with interchanged depths, were run to confirm the sensitivity of the flux rating to depth and HLR. Simulations with and without a Stamford baffle were also done. While the design of the internal features of the SST, such as baffling, have a marked influence on the effluent SS concentration for underloaded SSTs, these features appeared to have only a small influence on the flux rating, i.e. capacity, of the SST. In the meantime until more information is obtained, it would appear that from the simulations so far that the flux rating of 0.80 of the 1DFT maximum SLR recommended by Ekama and Marais remains a reasonable value to apply in the design of full scale SSTs – for deep SSTs (4 m SWD) the flux rating could be increased to 0.85 and for shallow SSTs (2.5 m SWD) decreased to 0.75. It is recommended that (i) while the apparent interrelationship between SST flux rating and depth suggests some optimization of the volume of the SST, that this be avoided and that (ii) the depth of the SST be designed independently of the surface area as is usually the practice and once selected, the appropriate flux rating is applied to the 1DFT estimate of the surface area.

Experiment of Polyester Wastewater Treatment by Aerobic Membrane Bioreactor and an Engineering Application

2012 ◽  
Vol 518-523 ◽  
pp. 2130-2137
Author(s):  
Si Hao Lv ◽  
Hui Chang ◽  
Zhi Hui Liang ◽  
Yan Yan Zeng ◽  
Hong Bo Fan
Keyword(s):  
Water Quality ◽  
Pilot Study ◽  
Membrane Bioreactor ◽  
Suspended Solids ◽  
Loading Rate ◽  
Engineering Application ◽  
Full Scale ◽  
Effluent Water ◽  
Small Influence ◽  
Volumetric Loading

A pilot study was carried out to evaluate the application of aerobic submerged MBR in treating polyester wastewater and a full scale system in which MBR was adopted as the key aspect was put forward to treat the polyester wastewater of Zhuhai Yuhua Polyester co., Ltd., China. The pilot study revealed that HRT could be affected by the influent COD, and a HRT larger than 36h was proposed for treating polyester wastewater by MBR. Volumetric loading rate and sludge loading rate ranged in 0.7-2.0 kgCOD/m3•d and 0.09~0.24 kgCOD/ kgMLSS•d respectively were of small influence on the COD removal. DO in the range of 2.5-4.0 mg/L seemed to be optimal for avoiding limitations due to oxygen concentration and creating an effective turbulence. The modified full scale system which includes anaerobic digesting tank and MBR followed by a stabilization pond was verified to be effective to treat the polyester wastewater in the latest two years. The results illustrated that the effluent water quality could meet the discharge limits of water pollutants (DB 44/26-2001) which was established in Guangdong, China. Observed sludge yield of the system fluctuated between 0.10-0.18 gMLSS/gCOD and averaged at 0.137 gMLSS/gCOD. The membrane permeate at around 10 L/m2h, TMP of less than 0.7bar, and total mixed liquor suspended solids (MLSS) between 6-7g/L were suitable to operate the MBR.

ADVANCED TREATMENT OF BIOTREATED WATER OF SECONDARY SETTING TANKS FROM SUSPENDED SUBSTANCES BY VOLUME FILTER CARTRIDGES

2016 ◽  
Vol 6 (4) ◽  
pp. 49-53
Author(s):  
Arkady N. KIM ◽  
Alexandra Yu. ROMANOVA
Keyword(s):  
Wastewater Treatment ◽  
Polymeric Material ◽  
Suspended Solids ◽  
Settling Tank ◽  
Advanced Treatment ◽  
Suspended Substances ◽  
Secondary Settling ◽  
Filter Cartridge

The article considers the problem of removal of suspended substances from secondary setting tanks during wastewater treatment and suggests a technology of wastewater radvanced treatment from suspended solids with volume filter cartridge. The volume filter cartridge is placed inside a secondary settling tank - in front of the collection tray. Volume filter cartridge is a cylinder that is made of a porous polymeric material, the direction of filtration is determined as from outside to inside. The results of prototype installation use in secondary setting tank show that this technology allows to reduce the concentration of suspended solids by 75 %; BOD5 - up to 30 %; COD - up to 10 %.

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.

Solids routing in an activated sludge process during hydraulic overloads

1996 ◽  
Vol 34 (3-4) ◽  
pp. 9-16 ◽  
Author(s):  
Youngchul Kim ◽  
Wesley O. Pipes
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Quantitative Description ◽  
Settling Tank ◽  
Plant Performance ◽  
Activated Sludge Process ◽  
Mixed Liquor ◽  
Solids Concentration ◽  
Storm Flow ◽  
The Individual

In order to provide a quantitative description of solids wash-out from the settling tanks of an activated sludge process, a method for “routing” of the suspended solids through the settling tanks was developed. The objective was to develop a method which can be used to predict the mixed liquor suspended solids concentration (X) and the sludge blanket depth (SBD) in the clarifiers during transient hydraulic overloads. There were 27 individual hydraulic overloading events encountered during 31 months of study. The solids routing and the SBD prediction were performed for the individual storm flow events by using settling tank operating data. The results of solids routing analysis were found to be satisfactory. The mixed liquor solids concentration can be predicted within ± 10%. The application of a solids storage relationship developed for the settling tanks was found to be useful for describing the dynamic behavior of the SBD during transient hydraulic overloads. The solids wash-out predictions for rainstorm periods corresponded with the plant performance. Operational procedures for avoiding solids wash-out are also discussed.

scholarly journals Effect of Volume Loading Rate and C/N on Ship Domestic Sewage Treatment by Two Membrane Bioreactors

2019 ◽  
Vol 64 (3) ◽  
pp. 328-339
Author(s):  
Yuhang Cai ◽  
Asad A. Zaidi ◽  
Peiqi Sun ◽  
Yue Shi ◽  
Kun Zhang ◽  
...  
Keyword(s):  
Membrane Reactor ◽  
Urease Activity ◽  
Suspended Solids ◽  
Loading Rate ◽  
Sewage Treatment ◽  
Oxygen Demand ◽  
Domestic Wastewater ◽  
Domestic Sewage ◽  
Volume Loading ◽  
Interesting Phenomenon

Design of ship sewage treatment systems that not only satisfy the use of small space on board but also meets International Maritime Organisation (IMO) latest emission standards is still a challenging problem for ship industry. This study provides a comparative disquisition between two different MBR reactors i.e, air-lift multilevel circulation membrane reactor (AMCMBR) and anaerobic/anoxic/aerobic membrane reactor (AOA-MBR) for domestic sewage treatment. The influence of pollutants volume loading rate (VLR) and C/N on effluent chemical oxygen demand (COD), ammonium nitrogen (NH4+-N) and TN for marine domestic sewage was analyzed. The results revealed that AMCMBR showed better removal efficiencies for COD and TN than AOA-MBR. The volume of AMCMBR was only half of the AOA-MBR. In addition, high average value of mixed liquor volatile suspended solids (MLVSS)/mixed liquid suspended solids (MLSS) (i.e. 0.75) of AMCMBR indicated high biomass and good pollutants removal achieved by this reactor. An interesting phenomenon was found in the study regarding Urease activity for the two reactors. Urease activity for AMCMBR in different working conditions all exceeded AOA-MBR and there exist no clear difference of NR activities between AMCMBR and AOA-MBR except for low C/N ratio (i.e. 6 and 4). This phenomenon proved that AMCMBR has a greater performance for treating ship domestic wastewater.

Modeling and Simulation of the Activated Sludge Process at a Full-Scale WWTP

2012 ◽  
Vol 599 ◽  
pp. 505-509
Author(s):  
Pei Li Lu ◽  
Zhen Liang Li
Keyword(s):  
Activated Sludge ◽  
Settling Tank ◽  
Coupling Model ◽  
Full Scale ◽  
Model Parameters ◽  
Activated Sludge Process ◽  
Modeling Methodology ◽  
Sst Model ◽  
Lower Temperature ◽  
Secondary Settling

Model of a full-scale activated sludge process in a WWTP in Chongqing, China was established by coupling Activated Sludge Model No.2 (ASM2) and secondary settling tank (SST) model. Influent COD of the ASM2 was characterized through combined respirometric and physical-chemical assay and the model parameters were calibrated after evaluating their structural identifiability. The SST model is a flux model based on the consistent modeling methodology, in which a more detailed sludge settling velocity function was proposed to describe the most settling phenomena happened in SST, including discrete settling of floc, zone settling, and compression settling. The coupling model was used to simulate and optimize the operation of the activated sludge process It is concluded that: 1) the effluent COD, SS, TN and TP could be simulated well, 2) the sludge recycle ratio in the SST and the sludge concentration in the bioreactor were optimized to reduce waste sludge, increase the capability to resist load shocks and lower temperature, and improve effluent quality, and 3) an A2/O processes was proposed to upgrade the WWTP for improving the efficiency of N and P removal.

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