Temperature modelling and prediction for activated sludge systems

2009 ◽  
Vol 59 (1) ◽  
pp. 125-131 ◽  
Author(s):  
S. Lippi ◽  
D. Rosso ◽  
C. Lubello ◽  
R. Canziani ◽  
M. K. Stenstrom
Keyword(s):  
Reference Data ◽  
Volume Ratio ◽  
Sensitivity Analyses ◽  
Temperature Model ◽  
Physiochemical Properties ◽  
Aeration System ◽  
Steady State Temperature ◽  
Biomass Activity ◽  
Tank Geometry ◽  
Activated Sludge Systems

Temperature is an important factor affecting biomass activity, which is critical to maintain efficient biological wastewater treatment, and also physiochemical properties of mixed liquor as dissolved oxygen saturation and settling velocity. Controlling temperature is not normally possible for treatment systems but incorporating factors impacting temperature in the design process, such as aeration system, surface to volume ratio, and tank geometry can reduce the range of temperature extremes and improve the overall process performance. Determining how much these design or up-grade options affect the tank temperature requires a temperature model that can be used with existing design methodologies. This paper presents a new steady state temperature model developed by incorporating the best aspects of previously published models, introducing new functions for selected heat exchange paths and improving the method for predicting the effects of covering aeration tanks. Numerical improvements with embedded reference data provide simpler formulation, faster execution, easier sensitivity analyses, using an ordinary spreadsheet. The paper presents several cases to validate the model.

A control strategy for reducing aeration costs during low loading periods

2004 ◽  
Vol 50 (7) ◽  
pp. 61-68 ◽  
Author(s):  
C. Sahlmann ◽  
J.A. Libra ◽  
A. Schuchardt ◽  
U. Wiesmann ◽  
R. Gnirss
Keyword(s):  
Flow Rate ◽  
Control Strategy ◽  
Oxygen Transfer ◽  
Air Flow ◽  
Air Flow Rate ◽  
Transfer Rates ◽  
Diffuser Flow ◽  
Aeration System ◽  
Oxygen Transfer Efficiency ◽  
Biomass Activity

The efficiency of the aeration system in a full-scale activated sludge basin with 3 separately controlled aeration zones was improved for the low loading period in summer. The air flow rate to each aeration zone is currently regulated to hold a preset dissolved oxygen concentration (DO). Four different DO setpoint combinations were tested, each one for a one week period, using dynamic off-gas testing to measure the standardised oxygen transfer efficiency (αSOTE). As the DO setpoints were lowered, the total air flow rate to the basin decreased initially. A low DO in the first zones slowed biomass activity and pushed the load towards the end of the aeration basin. The relationship between αSOTE and the specific diffuser flow rate qD is different for each zone. In Zone 1 there was a strong decrease in αSOTE as qD increased, while Zones 2 and 3 were fairly independent of qD, Zone 2 at a higher level than Zone 3. Aeration costs were reduced by 15% for the most efficient combination. To achieve even more savings, a control strategy adjusting oxygen transfer rates over the aeration basin to the necessary oxygen transfer rates is suggested. It is based on changing the DO setpoints to reach the lowest total air flow rate while meeting the effluent requirements.

scholarly journals Membrane integrated process for advanced treatment of high strength Opium Alkaloid wastewaters

2018 ◽  
Vol 77 (7) ◽  
pp. 1899-1908 ◽  
Author(s):  
Güçlü Insel ◽  
Ahmet Karagunduz ◽  
Murat Aksel ◽  
Emine Cokgor ◽  
Gokce Kor-Bicakci ◽  
...  
Keyword(s):  
Inorganic Nitrogen ◽  
Oxygen Demand ◽  
High Strength ◽  
Complete Removal ◽  
Advanced Treatment ◽  
Treated Effluent ◽  
Aeration System ◽  
Total Inorganic Nitrogen ◽  
Conductivity Parameter ◽  
Activated Sludge Systems

Abstract In this study, an integrated aerobic membrane bioreactor (MBR)-nanofiltration (NF) system has been applied for advanced treatment of Opium processing wastewaters to comply with strict discharge limits. Aerobic MBR treatment was successfully applied to high strength industrial wastewater. In aerobic MBR treatment, a non-fouling unique slot aeration system was designed using computational fluid dynamics techniques. The MBR was used to separate treated effluent from dispersed and non-settleable biomass. Respirometric modeling using MBR sludge indicated that the biomass exhibited similar kinetic parameters to that of municipal activated sludge systems. Aerobic MBR/NF treatment reduced chemical oxygen demand (COD) from 32,000 down to 2,500 and 130 mg/L, respectively. The MBR system provided complete removal of total inorganic nitrogen; however, nearly 50 mgN/L organic nitrogen remained in the permeate. Post NF treatment after MBR permeate reduced nitrogen below 20 mgN/L, providing nearly total color removal. In addition, a 90% removal in the conductivity parameter was reached with an integrated MBR/NF system. Finally, post NF application to MBR permeate was found not to be practical at higher pH due to low flux (3–4 L/m2/hour) with low recovery rates (30–40%). As the permeate pH lowered to 5.5, 75% of NF recovery was achieved at a flux of 15 L/m2/hour.

Diffused aeration systems from theory to design

1978 ◽  
Vol 5 (1) ◽  
pp. 32-41 ◽  
Author(s):  
Jatinder K. Bewtra ◽  
Donald S. Mavinic
Keyword(s):  
Oxygen Transfer ◽  
Climatic Conditions ◽  
Air Bubbles ◽  
Cold Regions ◽  
Surface Aeration ◽  
Conventional Activated Sludge ◽  
Aeration System ◽  
Tank Geometry ◽  
Counter Current ◽  
Mechanical Surface

Aeration has been used successfully in northern Canada and other cold regions for treating domestic and industrial waste waters by aerated lagoons, extended aeration package units and conventional activated sludge plants. Many of these installations used diffused aeration because this system has shown several advantages over mechanical surface aeration. The advantages of using diffused aeration in cold regions for oxygenation as well as for mixing are discussed in this paper.The parameters affecting the efficiency of oxygen transfer and the mixing of the tank contents are identified and the influence of varying these operating parameters on the performance of diffused aeration systems under cold climatic conditions is discussed. Equations showing the influence of temperature, airflow rates, submergence and tank geometry on the overall oxygen transfer coefficient are presented.A process of aeration, employing counter-current flow of air bubbles and waste water, is shown to result in increased contact time and therefore higher oxygenation efficiencies. A typical example for designing a diffused aeration system in cold regions has been worked out.

The Selector Effect on Filamentous Bulking in Long Sludge Age Activated Sludge Systems

1991 ◽  
Vol 23 (4-6) ◽  
pp. 867-877 ◽  
Author(s):  
D. M. D. Gabb ◽  
D. A. Still ◽  
G. A. Ekama ◽  
D. Jenkins ◽  
G. v. R. Marais
Keyword(s):  
Activated Sludge ◽  
Phosphorus Removal ◽  
Sufficient Conditions ◽  
Extensive Investigation ◽  
Intermittent Aeration ◽  
Nitrogen And Phosphorus ◽  
Nitrogen And Phosphorus Removal ◽  
Aeration System ◽  
Microthrix Parvicella ◽  
Activated Sludge Systems

A survey of long sludge age activated sludge plants in South Africa showed that bulking was widespread in nitrogen and nitrogen and phosphorus removal plants with the dominant causative filamentous organisms being the low F/M types 0092, 0675, 0041, Microthrix parvicella, 0914 and 1851. The literature suggests that in aerobic systems proliferation of the low F/M filaments can be controlled by aerobic selector reactors. From an extensive investigation into the selector reactors, and the effect these stimulate, it was concluded that in long sludge age systems, irrespective of whether or not a selector effect is present in the sludge, (1) under completely aerobic conditions low F/M filaments do not proliferate, (2) sequential or alternating anoxic-aerobic periods like intermittent aeration are necessary, though not sufficient, conditions for the proliferation of low F/M filaments, and (3) an aerobic selector installed on an intermittent aeration system did not control low F/M filament proliferation.

Incidence of Sphaerotilus Natans in Laboratory Scale Activated Sludge Systems

1989 ◽  
Vol 21 (4-5) ◽  
pp. 29-41 ◽  
Author(s):  
D. M. D. Gabb ◽  
G. A. Ekama ◽  
D. Jenkins ◽  
G. v. R. Marais
Keyword(s):  
Activated Sludge ◽  
Surface Area ◽  
Volume Ratio ◽  
Full Scale ◽  
Laboratory Scale ◽  
Sphaerotilus Natans ◽  
Attached Growth ◽  
Mixed Liquor ◽  
Activated Sludge Systems

Bulking in activated sludge systems due to proliferation of Sphaerotilus natans is very common in laboratory-scale but rare in full-scale systems. From two laboratory-scale studies it is concluded that a cause for proliferation was attached growth of S.natans on the walls of the feed lines and reactor surfaces continuously seeding the mixed liquor. It is suggested that S.natans bulking in laboratory-scale systems is common compared to full-scale systems because the surface area/volume ratio of the former is orders of magnitude higher than that of the latter so that the potential for seeding from attached growths in laboratory-scale plants is correspondingly higher. It would appear that in laboratory-scale activated sludge systems regular cleaning of the feed lines and daily scrubbing of the reactor and other wetted surfaces will eliminate S.natans bulking due to seeding of the mixed liquor from these surfaces.

Activated Sludge Nitrification in Temperate Climate

1992 ◽  
Vol 25 (4-5) ◽  
pp. 177-184 ◽  
Author(s):  
J. la Cour Jansen ◽  
G. H. Kristensen ◽  
K. D. Laursen
Keyword(s):  
Steady State ◽  
Energy Balance ◽  
Activated Sludge ◽  
Temperate Climate ◽  
Design Phase ◽  
Temperature Model ◽  
Plant Operator ◽  
Steady State Temperature ◽  
Winter Temperatures ◽  
Wind Exposure

In Denmark winter temperature of the wastewater is typically 5-10°C, and ammonia concentrations below 1-4 mg/l are normal discharge limits under these conditions. Special attention is needed in design and operation of treatment plants in order to fulfill such limits. Based on a simple energy balance a steady-state temperature model is developed and verified at full scale treatment plants. The model enables a good estimate of expected winter temperatures in the design phase. Deep tanks and good protection against wind exposure are shown to be attractive means to avoid a too low process temperature during winter periods. Successful winter nitrification can be obtained if the plant operator is supplied with tools to identify arising problems. A procedure to predict if the actual plant nitrification capacity is approaching the necessary capacity based on the load is described and tested.

Biosensors for nitrogen control in wastewaters

1996 ◽  
Vol 34 (1-2) ◽  
pp. 213-220 ◽  
Author(s):  
A. G. Massone ◽  
K. Gernaey ◽  
H. Bogaert ◽  
A. Vanderhasselt ◽  
A. Rozzi ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Biological Activity ◽  
Carbon Source ◽  
Wastewater Treatment Plants ◽  
Nitrogen Control ◽  
Biomass Activity ◽  
On Line ◽  
Removal Processes ◽  
Nitrate And Nitrite ◽  
Activated Sludge Systems

The control of nitrogen removal processes in activated sludge systems requires not only on-line values of the parameters such as ammonium, nitrate and nitrite, but also an evaluation on the nitrifying and denitrifying biomass activity, influent toxicity and carbon source requirements for denitrification. This paper describes four different biosensors, two on denitrification and two on nitrification. They all measure the biological activity of the nitrifying or denitrifying bacteria. Three of them measure nitrogen and carbon species, the fourth biosensor measures influent toxicity. These instruments open new perspectives for efficient on-line monitoring of wastewater treatment plants.

Optimisation of Aeration Efficiency: A Design Procedure for Secondary Treatment Using a Hybrid Aeration System

1989 ◽  
Vol 21 (10-11) ◽  
pp. 1403-1419 ◽  
Author(s):  
V. K. Thomas ◽  
B. Chambers ◽  
W. Dunn
Keyword(s):  
Plug Flow ◽  
Design Procedure ◽  
Aeration Tank ◽  
Surface Aeration ◽  
Aeration System ◽  
Fine Bubble ◽  
Oxygen Transfer Efficiency ◽  
Aeration Efficiency ◽  
Attractive Option ◽  
Activated Sludge Systems

The fine-bubble diffused air (FBDA) system of aeration is most efficiently operated in low rate activated sludge systems. The aeration technique is, however, subject to poor oxygen transfer efficiency and diffuser clogging under increased loading conditions such as are experienced close to the tank inlet in plug-flow systems. Mechanical, surface aeration systems, though apparently less efficient, do not suffer from these disadvantages. The ideal aeration tank configuration, for optimum aeration efficiency is therefore:–inlet anoxic zone–completely mixed surface aerated zone–plug-flow, fine-bubble diffused air zone with tapered aeration–clarification tanks. An overall aeration efficiency of 1.5-2.0 kg/kwh is predicted for nitrifying systems, together with an increased diffuser lifetime compared to a conventional FBDA tank. The design procedure is illustrated using parameters for a large UK works. Despite greater civil costs, the reduced running costs and NPC of the hybrid system make it an attractive option when compared to a plug-flow FBDA system or a conventional surface aeration plant.

NUMERICAL SIMULATION OF HIGH-TEMPERATURE IONIZED AIR RADIATION ON UNSTRUCTURED GRIDS

2009 ◽  
Vol 23 (03) ◽  
pp. 281-284
Author(s):  
XUEQIANG LIU ◽  
YIBIN WANG ◽  
YIZHAO WU
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Reference Data ◽  
Unstructured Grids ◽  
Temperature Model ◽  
Gamma Prime ◽  
Ionized Air ◽  
Volume Method ◽  
Equilibrium Effect ◽  
Two Temperature

A numerical method which is based on unstructured grids to compute high-temperature ionized air radiation is described. The multi-species N-S equations are used and the chemical model includes 11 species ( O 2, N 2, O , N , NO , NO +, N +, O +, N +2, O +2, e -) and 20 reactions. For simulating thermal non-equilibrium effect, the two-temperature model is considered. The finite volume method (FVM) is used for spatial and directional discretization for the RTE on unstructured grids. The code can deal with different kinds of species and radiative bands. Particularly, the Delta, Epsilon, Beta prime and Gamma prime bands of NO are considered in this paper. The numerical results of MESES-C for hypersonic flow with high-temperature ionized radiation are shown, and compared well with the reference data and experimental data.

A comparison among different methods for evaluating the biomass activity in activated sludge systems: preliminary results

2002 ◽  
Vol 46 (1-2) ◽  
pp. 413-417 ◽  
Author(s):  
G. Andreottola ◽  
L. Baldassarre ◽  
C. Collivignarelli ◽  
R. Pedrazzani ◽  
P. Principi ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Oxygen Uptake Rate ◽  
Cost Savings ◽  
Pollutant Degradation ◽  
Recirculation Flow ◽  
Preliminary Results ◽  
Biomass Activity ◽  
Working Parameters ◽  
Effluent Characteristics ◽  
Activated Sludge Systems

In order to improve activated sludge plant operation (achieving higher efficiency and cost savings) beside influent and effluent characteristics and working parameters (e.g. dissolved oxygen, total and volatile suspended solids, pH, recirculation flow rate, etc.), the biomass activity should be monitored, the bacteria being responsible for the pollutant degradation. Since conventional cultivation based methods are inadequate to quantify environmental microorganisms (due to scarce number of cultivable microorganisms and time-consuming procedures) several “non-conventional” techniques were applied in this study, in order to compare the obtainable information and their routine feasibility. Different measurements (VSS concentration, Oxygen Uptake Rate, microbial counts by cultural and biomolecular methods – MPN-PCR, ATP content, dehydrogenase activity, microbial cell viability and enzymatic activity) were carried out on mixed liquor samples, taken from a municipal activated sludge plant (440,000 p. e.). The preliminary results of the research are presented in this paper.

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