A comparison between model and rule based control of a periodic activated sludge process

1998 ◽  
Vol 37 (12) ◽  
pp. 343-351 ◽  
Author(s):  
S. Isaacs ◽  
D. Thornberg
Keyword(s):  
Activated Sludge ◽  
Inorganic Nitrogen ◽  
Test Scenario ◽  
Rule Based ◽  
Criterion Functions ◽  
Model Predictions ◽  
Simple Rules ◽  
Fixed Phase ◽  
Total Inorganic Nitrogen ◽  
Better Than

Two strategies for control of nitrogen removal in an alternating activated sludge plant are compared. One is based on simple model predictions determining the cycle length at the beginning of each cycle. The other is based on simple rules relating present ammonia and nitrate concentrations. Both strategies are close in efficiency measured as effluent total (inorganic) nitrogen and both perform better than using fixed phase lengths for a test scenario describing a typical dry weather diurnal variation. After modifying the criterion functions of the rule based strategy the two strategies are found to produce equivalent controls, which means that the optimal criteria of the model based strategy can be fulfilled without the need for model predictions.

Rule based control of a periodic activated sludge process

1998 ◽  
Vol 38 (3) ◽  
pp. 281-289 ◽  
Author(s):  
S. Isaacs ◽  
D. Thornberg
Keyword(s):  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Control Strategy ◽  
Periodic Operation ◽  
Rule Based ◽  
Criterion Functions ◽  
Strategy Performance ◽  
Working Region ◽  
And Control ◽  
Selection Of

A rule based control strategy for automatically adjusting phase lengths and aeration intensity for an activated sludge nutrient removal process based on a periodic operation is examined using simulations based on the Activated Sludge Model No. 1. The strategy is based on four criterion functions, two which determine the switching of the roles of two nitrifying/denitrifying reactors and two which adjust the dissolved oxygen setpoint levels in the two reactors as functions of ammonia and nitrate concentrations. Trajectory plots of reactor concentrations in the ammonia-nitrate plane are shown to be a useful means of visualizing process and control performance. Together, the trajectories from a working region in the ammonia-nitrate plane, the size and location of which can to some extent be predetermined by selection of the criterion functions. The presented results include the influence of one of the criterion functions on control strategy performance, how an incompatibility between two criterion functions can lead to unsymmetric reactor loading, and the effect of allowing simultaneous nitrification and denitrification during nitrifying periods by reducing the dissolved oxygen level as ammonia is consumed.

scholarly journals Comparative Analysis of Hydrogenotrophic Denitrification in up and down Flow Reactors

2019 ◽  
Vol 15 (2) ◽  
pp. 87-91
Author(s):  
Rabin Maharjan ◽  
Iswar Man Amatya ◽  
Ram Kumar Sharma
Keyword(s):  
Comparative Analysis ◽  
Flow Reactor ◽  
Flow Direction ◽  
Inorganic Nitrogen ◽  
Flow Reactors ◽  
Total Inorganic Nitrogen ◽  
The Difference ◽  
Tin Removal ◽  
Better Than

Use of ground water containing ammonical nitrogen has been increasing in Kathmandu valley. The use of locally and cheaply fitted Hydrogenotrophic Denitrification (HD) has been taken as an effective way to remove the nitrates in this study. Comparative analysis of HD reactors had been studied for the determination of the effective flow direction of water as Up Flow or Down Flow. The result reviled that flow direction as Down Flow HD reactor performed slightly better than Up Flow HD reactor. The maximum NO3-N conversion reached 100% for Down Flow and 98.65% for Up Flow reactor with maximum of total inorganic nitrogen (TIN) removed were 41.11% and 33.89% for Down Flow and Up Flow reactor respectively. The difference in NO3-N conversion and TIN removal were observed. As the NO2-N was accumulated, suggesting NO3 conversion is higher than NO2 conversion thus, and majorly incomplete denitrification existed. The NO2-N in water reached to maximum of 78.89 mg/l and 72.55 mg/l for Down Flow and Up Flow rector.

scholarly journals The duration-energy-size enigma for acoustic emission

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Blai Casals ◽  
Karin A. Dahmen ◽  
Boyuan Gou ◽  
Spencer Rooke ◽  
Ekhard K. H. Salje
Keyword(s):  
Acoustic Emission ◽  
Mean Field Theory ◽  
Mean Field ◽  
Maximum Amplitude ◽  
Time Profile ◽  
Power Law Distribution ◽  
Model Predictions ◽  
Ae Signal ◽  
Strain Signal ◽  
Better Than

AbstractAcoustic emission (AE) measurements of avalanches in different systems, such as domain movements in ferroics or the collapse of voids in porous materials, cannot be compared with model predictions without a detailed analysis of the AE process. In particular, most AE experiments scale the avalanche energy E, maximum amplitude Amax and duration D as E ~ Amaxx and Amax ~ Dχ with x = 2 and a poorly defined power law distribution for the duration. In contrast, simple mean field theory (MFT) predicts that x = 3 and χ = 2. The disagreement is due to details of the AE measurements: the initial acoustic strain signal of an avalanche is modified by the propagation of the acoustic wave, which is then measured by the detector. We demonstrate, by simple model simulations, that typical avalanches follow the observed AE results with x = 2 and ‘half-moon’ shapes for the cross-correlation. Furthermore, the size S of an avalanche does not always scale as the square of the maximum AE avalanche amplitude Amax as predicted by MFT but scales linearly S ~ Amax. We propose that the AE rise time reflects the atomistic avalanche time profile better than the duration of the AE signal.

scholarly journals Simulation of denitrification and ozone loss for the Arctic winter 2002/2003

2005 ◽  
Vol 5 (6) ◽  
pp. 1437-1448 ◽  
Author(s):  
J.-U. Grooß ◽  
G. Günther ◽  
R. Müller ◽  
P. Konopka ◽  
S. Bausch ◽  
...  
Keyword(s):  
Inorganic Nitrogen ◽  
Potential Temperature ◽  
Three Dimensional ◽  
Lagrangian Model ◽  
The Arctic ◽  
Particle Nucleation ◽  
Ozone Loss ◽  
Dimensional Version ◽  
Total Inorganic Nitrogen ◽  
Catalytic Cycles

Abstract. We present simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the Arctic winter 2002/2003. We integrated a Lagrangian denitrification scheme into the three-dimensional version of CLaMS that calculates the growth and sedimentation of nitric acid trihydrate (NAT) particles along individual particle trajectories. From those, we derive the HNO3 downward flux resulting from different particle nucleation assumptions. The simulation results show a clear vertical redistribution of total inorganic nitrogen ( ), with a maximum vortex average permanent removal of over 5ppb in late December between 500 and 550K and a corresponding increase of of over 2ppb below about 450K. The simulated vertical redistribution of is compared with balloon observations by MkIV and in-situ observations from the high altitude aircraft Geophysica. Assuming a globally uniform NAT particle nucleation rate of 7.8x10-6cm-3h-1 in the model, the observed denitrification is well reproduced. In the investigated winter 2002/2003, the denitrification has only moderate impact (≤14%) on the simulated vortex average ozone loss of about 1.1ppm near the 460K level. At higher altitudes, above 600K potential temperature, the simulations show significant ozone depletion through -catalytic cycles due to the unusual early exposure of vortex air to sunlight.

EFFECTS OF INORGANIC NITROGEN AND PHOSPHORUS FERTILIZERS ON SELECTED SITES OF NATIVE GRASSLAND IN WESTERN CANADA

1965 ◽  
Vol 45 (3) ◽  
pp. 229-237 ◽  
Author(s):  
M. R. Kilcher ◽  
S. Smoliak ◽  
W. A. Hubbard ◽  
A. Johnston ◽  
A. T. H. Gross ◽  
...  
Keyword(s):  
Inorganic Nitrogen ◽  
Total Yield ◽  
First Year ◽  
Western Canada ◽  
Phosphorus Fertilizer ◽  
Nitrogen And Phosphorus ◽  
Native Grass ◽  
Yield Increase ◽  
Native Grassland ◽  
Better Than

N, P, and N + P at 60, 26, and 60 + 26 lb per acre were applied on native grass sites during three successive years at seven, locations in Western Canada. Single applications of the N fertilizer resulted in 3- or 4-year total yield increases of 300 to 600 lb per acre at six locations. At Summerland the 3-year increase was nearly 1400 lb. Phosphorus fertilizer by itself provided very little yield increase. N + P gave yield increases that were only slightly better than those from N alone.Residual responses to fertilizer were important, especially in the 12- to 16-in. rainfall locations. Only about one-third of the total yield increase occurred in the first year, with the remainder coming in the subsequent seasons.Weeds, where present, showed a marked response to fertilizer N in the first season; in subsequent years the response largely disappeared.

scholarly journals A networked voting rule for democratic representation

2018 ◽  
Vol 5 (3) ◽  
pp. 172265 ◽  
Author(s):  
Alexis R. Hernández ◽  
Carlos Gracia-Lázaro ◽  
Edgardo Brigatti ◽  
Yamir Moreno
Keyword(s):  
Large Scale ◽  
Selection Process ◽  
General Relation ◽  
Community Size ◽  
Rule Based ◽  
Voting Rule ◽  
Large Populations ◽  
Negative Effect ◽  
High Connectivity ◽  
Better Than

We introduce a general framework for exploring the problem of selecting a committee of representatives with the aim of studying a networked voting rule based on a decentralized large-scale platform, which can assure a strong accountability of the elected. The results of our simulations suggest that this algorithm-based approach is able to obtain a high representativeness for relatively small committees, performing even better than a classical voting rule based on a closed list of candidates. We show that a general relation between committee size and representatives exists in the form of an inverse square root law and that the normalized committee size approximately scales with the inverse of the community size, allowing the scalability to very large populations. These findings are not strongly influenced by the different networks used to describe the individuals’ interactions, except for the presence of few individuals with very high connectivity which can have a marginal negative effect in the committee selection process.

scholarly journals Biological nutrient removal from industrial wastewater using a sequencing batch reactor

2018 ◽  
Author(s):  
◽  
Siphesihle Mangena Khumalo
Keyword(s):  
Industrial Wastewater ◽  
Batch Reactor ◽  
Inorganic Nitrogen ◽  
Laboratory Scale ◽  
Biological Nutrient Removal ◽  
Brewery Wastewater ◽  
Total Organic Nitrogen ◽  
Utilisation Rate ◽  
Rate Kinetics ◽  
Total Inorganic Nitrogen

South Africa is not an exception when it comes to the issue of fresh water scarcity perpetuated by environmental pollution among many other factors. Industrial wastewater particularly emanating from the brewing industry, contains high-strength organic, inorganic, and biological compounds which are toxic to the environment. Due to stringent industrial effluent dewatering standards enforced by both local and international environmental protection entities, industrial wastewater cannot be discharged into receiving water bodies prior to treatment. The overall aim of this study was to evaluate the performance or treatment efficacy of a laboratory scale sequencing batch reactor on biological nutrient removal using industrial wastewater from brewery. In this study, two laboratory scale sequencing batch reactors (SBRs) operated in a cyclic aerobic-anaerobic configuration inoculated with activated sludge were investigated for their removal of orthophosphates and nitrogen compounds from brewery wastewater. SBR-1 was investigated for nitrogen group pollutant removal and SBR-2 was investigated for orthophosphate removal. The findings of the study are reported based on overall removal efficacies for the following process monitoring parameters: orthophosphates, ammoniacal nitrogen, total Kjeldahl nitrogen, total nitrogen, total organic nitrogen, total inorganic nitrogen and NO3-N+NO2-N. From the investigation, the following overall removal efficacies were obtained: 69% orthophosphates, 69% ammoniacal nitrogen, 59% total Kjeldahl nitrogen, 60% total nitrogen, 64% total organic nitrogen, 67% total inorganic nitrogen and 56% NO3-N+NO2-N at an organic loading rate of 3.17 kg Total Chemical Oxygen Demand (TCOD) /m3.day with a food to microorganism ratio of 2.86 g TCOD/g Volatile Suspended Solids (VSS).day. These removal efficacies were attained for a hydraulic retention time of 18 hours for both SBRs with a solids retention time of 5 days for SBR-1 and 7 days for SBR-2. Both reactors were operated at a mesophilic temperature range of 23 to 26˚C and a pH range of 5 to 8.5. The temperature was left unadjusted because it was observed that it did not hinder any microbial activities during the biodegradation process. The Michealis-Menten’s and Monod models were implemented to study the substrate utilisation rate kinetics and microbial growth rate kinetics recording 15 141 g COD/m3.day; 12 518 g VSS/g VSS.day; 20 343 g COD/m3.day and 16 860 g VSS/g VSS.day for SBR-1 and SBR-2, respectively. The Monod model demonstrated a strong correlation fit between the substrate utilisation rate and microbial growth rate recording a polynomial correlation constant of R2 = 0.947 and 0.9582 for SBR-1 and SBR-2, respectively. The findings of this study showed that the cyclic aerobic-anaerobic configuration on a laboratory scale SBR inoculated with activated sludge for treatment of brewery wastewater for biological nutrients was feasible.

Sign in / Sign up

Export Citation Format

Share Document