scholarly journals The Impact of Local Hydrodynamics on High-Rate Activated Sludge Flocculation in Laboratory and Full-Scale Reactors

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 131 ◽  
Author(s):  
Sophie Balemans ◽  
Siegfried E. Vlaeminck ◽  
Elena Torfs ◽  
Leonie Hartog ◽  
Laura Zaharova ◽  
...  
Keyword(s):  
Activated Sludge ◽  
High Velocity ◽  
Numerical Data ◽  
Full Scale ◽  
High Rate ◽  
Homogeneous Distribution ◽  
Local Velocity ◽  
Local Conditions ◽  
Velocity Gradients ◽  
The Impact

High rate activated sludge (HRAS) processes have a high potential for carbon and energy recovery from sewage, yet they suffer frequently from poor settleability due to flocculation issues. The process of flocculation is generally optimized using jar tests. However, detailed jar hydrodynamics are often unknown, and average quantities are used, which can significantly differ from the local conditions. The presented work combined experimental and numerical data to investigate the impact of local hydrodynamics on HRAS flocculation for two different jar test configurations (i.e., radial vs. axial impellers at different impeller velocities) and compared the hydrodynamics in these jar tests to those in a representative section of a full scale reactor using computational fluid dynamics (CFD). The analysis showed that the flocculation performance was highly influenced by the impeller type and its speed. The axial impeller appeared to be more appropriate for floc formation over a range of impeller speeds as it produced a more homogeneous distribution of local velocity gradients compared to the radial impeller. In contrast, the radial impeller generated larger volumes (%) of high velocity gradients in which floc breakage may occur. Comparison to local velocity gradients in a full scale system showed that also here, high velocity gradients occurred in the region around the impeller, which might significantly hamper the HRAS flocculation process. As such, this study showed that a model based approach was necessary to translate lab scale results to full scale. These new insights can help improve future experimental setups and reactor design for improved HRAS flocculation.

Rain events and their effect on effluent quality studied at a full scale activated sludge treatment plant

2006 ◽  
Vol 54 (10) ◽  
pp. 201-208 ◽  
Author(s):  
B.-M. Wilén ◽  
D. Lumley ◽  
A. Mattsson ◽  
T. Mino
Keyword(s):  
Activated Sludge ◽  
Laboratory Data ◽  
Treatment Plant ◽  
Full Scale ◽  
Plant Performance ◽  
Particle Removal ◽  
Effluent Quality ◽  
Trickling Filters ◽  
Rain Events ◽  
The Impact

The effect of rain events on effluent quality dynamics was studied at a full scale activated sludge wastewater treatment plant which has a process solution incorporating pre-denitrification in activated sludge with post-nitrification in trickling filters. The incoming wastewater flow varies significantly due to a combined sewer system. Changed flow conditions have an impact on the whole treatment process since the recirculation to the trickling filters is set by the hydraulic limitations of the secondary settlers. Apart from causing different hydraulic conditions in the plant, increased flow due to rain or snow-melting, changes the properties of the incoming wastewater which affects process performance and effluent quality, especially the particle removal efficiency. A comprehensive set of on-line and laboratory data were collected and analysed to assess the impact of rain events on the plant performance.

Strong selection pressures impact the capacity of flocculating activated sludge bacteria to granulate

2013 ◽  
Vol 67 (8) ◽  
pp. 1678-1687 ◽  
Author(s):  
G. A. C. Ehlers ◽  
S. J. Turner
Keyword(s):  
Particle Size ◽  
Activated Sludge ◽  
Extracellular Polymeric Substances ◽  
High Rate ◽  
Volume Index ◽  
Size Analysis ◽  
Liquid Separation ◽  
Granule Formation ◽  
Selection Pressures ◽  
The Impact

The capacity of activated sludge (AS) microbial populations to form dense granules offers the potential to establish efficiently settleable biomass. This has the potential to circumvent problems around ineffective solids–liquid separation and sensitivity to variable chemical oxygen demand (COD) loads. Although a number of studies have evaluated aerobic laboratory granulation reactors as high-rate treatment systems, the biological processes involved in aerobic granulation are not fully understood. Concomitantly, the impact of operation parameters such as organic loading rates is also important for granulation. The ability of a flocculating AS community to granulate under different selection pressures was evaluated in a laboratory sequencing batch reactor by determining levels of extracellular polymeric substances (EPS) and particle size fractions that developed under feast (4.74 g COD L−1) and famine (0.42 g COD L−1) nutrient regimes. The efficiency of solid–liquid separation was also measured. Aggregation indices showed levels >94% and a sludge volume index factor of up to 0.94, which strongly suggested granule formation; however, microscopy evaluation showed a mixture of flocs and granules. Particle size analysis revealed binomial distribution patterns of particles in the reactor which shifted to smaller tightly bound particles (<200 μm) although large particles (>600 μm) were also measured during famine conditions. This coincided with increases in EPS levels although EPS quantities were low and it is postulated that this could have impacted granule formation: the EPS in the bacterial aggregates were consumed since the AS community was starved.

Pilot-Scale Demonstration of Two-Phase Anaerobic Digestion of Activated Sludge

1991 ◽  
Vol 23 (7-9) ◽  
pp. 1179-1188 ◽  
Author(s):  
Sam Ghosh
Keyword(s):  
Anaerobic Digestion ◽  
Organic Acids ◽  
Activated Sludge ◽  
Loading Rate ◽  
Pilot Scale ◽  
Full Scale ◽  
High Rate ◽  
Methane Fermentation ◽  
Two Phase ◽  
Fermentation Products

An innovative pilot-scale two-phase anaerobic digestion process was developed to stabilize concentrated (7-5%) activated sludge at a 12-day SRT and a loading rate of 5 kg VS/m3 d. The pilot system exhibited an unusually high VS reduction of 73%, an aggregated carbohydrate-protein-lipid reduction of 71%, and a methane yield of 0.3 m3/kg VS added. Optimum acidogenic fermentation producing 9500 mg/l of organic acids was achieved at an HRT of 3 days and a loading rate of 16 kg VS/m3.d or higher. Enhanced acidogenic hydrolysis and prehydrolysis of polymerics and nocardial residues eliminated digester foaming. Sulfate and nitrate reductions, and syntrophic methane fermentation occurred during acidogenic conversions. Acetogenesis and aceticlastic methane fermentation were predominant in the methane digester, which generated 93% of the system methane production. Contrary to literature reports, there was no inhibition of acetogens or methanogens at a high ammonia-N concentration of 2500 mg/l and pH 7.7. The acid and methane digesters could be started quickly. They were resilient to temperature drops and loading fluctuations. Acid fermentation of 8% of the plant's WAS and addition of the resulting fermentation products (enzymes, organic acids, etc.) to the full-scale high-rate digester increased VS reduction by 46% and eliminated severe foaming. Full-scale two-phase digestion of WAS is scheduled to start in 1990.

Plastic anisotropic and damage evolution analysis of recycled aluminium alloy AA6061 at high rate of strain

2020 ◽  
Vol 14 (4) ◽  
pp. 7589-7599
Author(s):  
C. S. Ho ◽  
M. K. Mohd Nor ◽  
M. A. Ab Rani ◽  
N. Ma'at ◽  
M. T. Hameed Sultan ◽  
...  
Keyword(s):  
Aluminium Alloy ◽  
High Velocity ◽  
Aluminium Alloys ◽  
Damage Evolution ◽  
Deformation Behaviour ◽  
High Energy ◽  
High Rate ◽  
Primary Sources ◽  
Rate Dependency ◽  
The Impact

Aluminium alloys have been widely used in many applications, and its usage is increasing yearly due to its distinctive properties. Nevertheless, it required high energy consumption and pollution during the production of primary sources. This leads to the attention in producing secondary sources to substitute the primary aluminium. Recycling of aluminium alloys adopted in automotive structures is a great option to save thousands of energy and prevent tons of CO2 from being released to the atmosphere. Numerous investigations must be conducted to establish the mechanical behaviour before the specific applications can be identified. However, there is a challenge for such recycled aluminium to achieve the same application as the primary sources due to material properties degradation related to damage. It is still an open study area to be explored for a better understanding of the behaviours of recycled aluminium. Thus, in this work, the Taylor Cylinder Impact test is used to investigate anisotropic-damage behaviour of recycled aluminium alloy AA6061 undergoing high-velocity impact from 190m/s to 300 m/s using two length-to-diameter (L/D) ratios. The recovered samples are observed under an optical microscope (OM) and scanning electron microscope (SEM). A strong strain rate dependency can be seen as the damage evolution is increasing as the impact velocity increase. Further, the corresponding digitized footprints analysis exhibit plastic anisotropic and localized plastic strain in such recycled material. This can be clearly observed from the development of a non-symmetrical footprint within the impact surface. This test is the first to explore the deformation behaviour of recycled materials using high-velocity cylinder impact in a high rate of strain deformation regime.

The impact of precipitation and external carbon source addition on biological nutrient removal in activated sludge systems – experimental investigation and mathematical modeling

2012 ◽  
Vol 7 (1) ◽  
Author(s):  
J. Makinia ◽  
J. Drewnowski ◽  
M. Swinarski ◽  
K. Czerwionka ◽  
M. Kaszubowska ◽  
...  
Keyword(s):  
Carbon Source ◽  
Activated Sludge ◽  
Carbon Sources ◽  
Full Scale ◽  
Biological Nutrient Removal ◽  
Batch Experiments ◽  
Carbon Addition ◽  
Reference Case ◽  
External Carbon Source ◽  
The Impact

The aim of this study was to determine the effects of chemical precipitation and addition of external carbon sources on the denitrification capability and enhanced biological phosphorus removal (EBPR) interactions at the ‘Wschod’ WWTP (600,000 PE) in Gdansk (northern Poland). For this purpose, different kinds of batch experiments were carried out with the settled wastewater (without pretreatment and after coagulation-flocculation) and external carbon sources (ethanol and fusel oil). Precipitation of colloidal and particulate organic fractions has a significant effect on denitrification and EBPR. The removal of these two fractions by coagulation-flocculation resulted in the reduced process rates (30–70%). The experimental investigations were supported by both lab-scale and full-scale simulations using a newly developed model as an expansion of the Activated Sludge Model No. 2d (ASM2d). The new model accurately predicted the effects of precipitation and external carbon addition in batch experiments. Full-scale simulations revealed that addition of external carbon source can compensate the effects of precipitation resulting in a similar NO3-N behavior compared to the reference case (without precipitation and external carbon addition). The combined effects of precipitation and addition of external carbon source resulted in a significantly different PO4-P behavior compared to the reference case.

Aerobic sludge digestion at cold temperatures

1977 ◽  
Vol 4 (4) ◽  
pp. 445-454 ◽  
Author(s):  
D. S. Mavinic ◽  
D. A. Koers
Keyword(s):  
Low Temperature ◽  
Activated Sludge ◽  
Continuous Flow ◽  
Reaction Rates ◽  
Full Scale ◽  
High Rate ◽  
Effect Of Temperature ◽  
Feed System ◽  
Cold Temperatures ◽  
Valid Comparison

Continuous flow, daily fill and draw, and batch aeration digesters were studied on a laboratory scale, to develop low temperature characteristics and design criteria for aerobic digestion of waste-activated sludge. These results were compared against full-scale data, from three independent sources. Raw sludge used in these studies was obtained from a municipal high-rate activated sludge plant. The digestion systems were operated at temperatures of 20, 10, and 5 °C, and at six different sludge ages. Measurements of all parameters studied were made under steady-state conditions.The results show that the effect of low temperature on aerobic digester performance is pronounced. The combined effect of temperature and sludge age is shown to be an important design parameter. Kinetic reaction rates and temperature coefficients were calculated on the basis of total volatile suspended solids. It was shown that batch and continuous feed system reaction rates are not interchangeable. The laboratory results further show that there is little difference between continuous flow and daily fill and draw digestion characteristics, except at 5 °C. Difficulties encountered in making a valid comparison between the laboratory and full-scale results are also discussed.

The Impact of High-Speed Rail on the Spatial Structure of Chinese Urban Agglomerations

2020 ◽  
Vol 46 (3) ◽  
pp. 379-397
Author(s):  
Chunyang Wang
Keyword(s):  
High Speed ◽  
River Delta ◽  
City Size ◽  
High Speed Rail ◽  
Local Conditions ◽  
Urban Agglomerations ◽  
Large Cities ◽  
Spatial Systems ◽  
Economic Concentration ◽  
The Impact

This paper measures the spatial evolution of urban agglomerations to understand be er the impact of high-speed rail (HSR) construction, based on panel data from fi ve major urban agglomerations in China for the period 2004–2015. It is found that there are signi ficant regional diff erences of HSR impacts. The construction of HSR has promoted population and economic diff usion in two advanced urban agglomerations, namely the Yang e River Delta and Pearl River Delta, while promoting population and economic concentration in two relatively less advanced urban agglomerations, e.g. the middle reaches of the Yang e River and Chengdu–Chongqing. In terms of city size, HSR promotes the economic proliferation of large cities and the economic concentration of small and medium-sized cities along its routes. HSR networking has provided a new impetus for restructuring urban spatial systems. Every region should optimize the industrial division with strategic functions of urban agglomeration according to local conditions and accelerate the construction of inter-city intra-regional transport network to maximize the eff ects of high-speed rail across a large regional territory.

Rehabilitation and Upgrading of the Beni Suef City Wastewater Treatment Plant

1990 ◽  
Vol 22 (7-8) ◽  
pp. 131-138
Author(s):  
Ahmed Fadel
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
Primary Treatment ◽  
High Rate ◽  
Shock Load ◽  
Economic Evaluations ◽  
Activated Sludge Process ◽  
Trickling Filter

Many of Egypt's cities have existing treatment plants under operation that have been constructed before 1970. Almost all of these treatment plants now need rehabilitation and upgrading to extend their services for a longer period. One of these plants is the Beni Suef City Wastewater Treatment Plant. The Beni Suef WWTP was constructed in 1956. It has primary treatment followed by secondary treatment employing intermediate rate trickling filters. The BOD, COD, and SS concentration levels are relatively high. They are approximately 800, 1100, and 600 mg/litre, respectively. The Beni Suef city required the determination of the level of work needed for the rehabilitation and upgrading of the existing 200 l/s plant and to extend its capacity to 440 l/s at year 2000 A description of the existing units, their deficiencies and operation problems, and the required rehabilitation are presented and discussed in this paper. Major problems facing the upgrading were the lack of space for expansion and the shortage of funds. It was, therefore, necessary to study several alternative solutions and methods of treatment. The choice of alternatives was from one of the following schemes: a) changing the filter medium, its mode of operation and increasing the number of units, b) changing the trickling filter to high rate and combining it with the activated sludge process, for operation by one of several possible combinations such as: trickling filter-solids contact, roughing filter-activated sludge, and trickling filter-activated sludge process, c) dividing the flow into two parts, the first part to be treated using the existing system and the second part to be treated by activated sludge process, and d) expanding the existing system by increasing the numbers of the different process units. The selection of the alternative was based on technical, operational and economic evaluations. The different alternatives were compared on the basis of system costs, shock load handling, treatment plant operation and predicted effluent quality. The flow schemes for the alternatives are presented. The methodology of selecting the best alternative is discussed. From the study it was concluded that the first alternative is the most reliable from the point of view of costs, handling shock load, and operation.

Upgrading Wastewater Treatment Plants with Anaerobic Selectors

1990 ◽  
Vol 22 (7-8) ◽  
pp. 35-43
Author(s):  
K. D. Tracy ◽  
S. N. Hong
Keyword(s):  
Phosphorus Removal ◽  
Wastewater Treatment Plants ◽  
Full Scale ◽  
High Rate ◽  
Nitrogen Control ◽  
Biological Phosphorus Removal ◽  
Conventional Activated Sludge ◽  
And Performance ◽  
Activated Sludge Processes ◽  
Biological Phosphorus

The anaerobic selector of the A/0™ process offers many advantages over conventional activated sludge processes with respect to process performance and operational stability. This high-rate, single-sludge process has been successfully demonstrated in full-scale operations for biological phosphorus removal and total nitrogen control in addition to BOD and TSS removal. This process can be easily utilized in upgrading existing treatment plants to meet stringent discharge limitations and to provide capacity expansion. Upgrades of two full-scale installations are described and performance data from the two facilities are presented.

Sign in / Sign up

Export Citation Format

Share Document