Model-based evaluation of mechanisms and benefits of mainstream shortcut nitrogen removal processes

2015 ◽  
Vol 71 (6) ◽  
pp. 840-847 ◽  
Author(s):  
Ahmed Al-Omari ◽  
Bernhard Wett ◽  
Ingmar Nopens ◽  
Haydee De Clippeleir ◽  
Mofei Han ◽  
...  
Keyword(s):  
Nitrogen Removal ◽  
Control Strategies ◽  
Model Based ◽  
Main Challenge ◽  
Nitrite Oxidizing Bacteria ◽  
Shortcut Nitrogen Removal ◽  
Target Ratio ◽  
Removal Processes ◽  
Selection Mechanisms ◽  
The Impact

The main challenge in implementing shortcut nitrogen removal processes for mainstream wastewater treatment is the out-selection of nitrite oxidizing bacteria (NOB) to limit nitrate production. A model-based approach was utilized to simulate the impact of individual features of process control strategies to achieve NO−2-N shunt via NOB out-selection. Simulations were conducted using a two-step nitrogen removal model from the literature. Nitrogen shortcut removal processes from two case studies were modeled to illustrate the contribution of NOB out-selection mechanisms. The paper highlights a comparison between two control schemes; one was based on online measured ammonia and the other was based on a target ratio of 1 for ammonia vs. NOx (nitrate + nitrite) (AVN). Results indicated that the AVN controller possesses unique features to nitrify only that amount of nitrogen that can be denitrified, which promotes better management of incoming organics and bicarbonate for a more efficient NOB out-selection. Finally, the model was used in a scenario analysis, simulating hypothetical optimized performance of the pilot process. An estimated potential saving of 60% in carbon addition for nitrogen removal by implementing full-scale mainstream deammonification was predicted.

scholarly journals Model-Based Analysis of Feedback Control Strategies in Aerobic Biotrickling Filters for Biogas Desulfurization

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 208
Author(s):  
Luis Rafael López ◽  
Mabel Mora ◽  
Caroline Van der Heyden ◽  
Juan Antonio Baeza ◽  
Eveline Volcke ◽  
...  
Keyword(s):  
Closed Loop ◽  
Control Strategies ◽  
Biotrickling Filter ◽  
Process Performance ◽  
Control Loops ◽  
Biotrickling Filters ◽  
Model Based ◽  
Outlet Concentration ◽  
The Impact ◽  
Model Based Analysis

Biotrickling filters are one of the most widely used biological technologies to perform biogas desulfurization. Their industrial application has been hampered due to the difficulty to achieve a robust and reliable operation of this bioreactor. Specifically, biotrickling filters process performance is affected mostly by fluctuations in the hydrogen sulfide (H2S) loading rate due to changes in the gas inlet concentration or in the volumetric gas flowrate. The process can be controlled by means of the regulation of the air flowrate (AFR) to control the oxygen (O2) gas outlet concentration ([O2]out) and the trickling liquid velocity (TLV) to control the H2S gas outlet concentration ([H2S]out). In this work, efforts were placed towards the understanding and development of control strategies in biological H2S removal in a biotrickling filter under aerobic conditions. Classical proportional and proportional-integral feedback controllers were applied in a model of an aerobic biotrickling filter for biogas desulfurization. Two different control loops were studied: (i) AFR Closed-Loop based on AFR regulation to control the [O2]out, and (ii) TLV Closed-Loop based on TLV regulation to control the [H2S]out. AFR regulation span was limited to values so that corresponds to biogas dilution factors that would give a biogas mixture with a minimum methane content in air, far from those values required to obtain an explosive mixture. A minimum TLV of 5.9 m h−1 was applied to provide the nutrients and moisture to the packed bed and a maximum TLV of 28.3 m h−1 was set to prevent biotrickling filter (BTF) flooding. Control loops were evaluated with a stepwise increase from 2000 ppmv until 6000 ppmv and with changes in the biogas flowrate using stepwise increments from 61.5 L h−1 (EBRT = 118 s) to 184.5 L h−1 (EBRT = 48.4 s). Controller parameters were determined based on time-integral criteria and simple criteria such as stability and oscillatory controller response. Before implementing the control strategies, two different mass transfer correlations were evaluated to study the effect of the manipulable variables. Open-loop behavior was also studied to determine the impact of control strategies on process performance variables such as removal efficiency, sulfate and sulfur selectivity, and oxygen consumption. AFR regulation efficiently controlled [O2]out; however, the impact on process performance parameters was not as great as when TLV was regulated to control [H2S]out. This model-based analysis provided valuable information about the controllability limits of each strategy and the impact that each strategy can have on the process performance.

Aeration control strategies for nitrogen removal: A pilot and model based investigation

2015 ◽  
Vol 2015 (3) ◽  
pp. 1-5
Author(s):  
Pusker Regmi ◽  
Mike Sadowski ◽  
Jose Jimenez ◽  
Bernhard Wett ◽  
Sudhir Murthy ◽  
...  
Keyword(s):  
Nitrogen Removal ◽  
Control Strategies ◽  
Model Based ◽  
Aeration Control

Model-Based Projection of Dementia Prevalence in China and Worldwide: 2020–2050

2021 ◽  
pp. 1-9
Author(s):  
Fangyu Li ◽  
Wei Qin ◽  
Min Zhu ◽  
Jianping Jia
Keyword(s):  
Control Strategies ◽  
Health Planning ◽  
Simulation Method ◽  
The United States ◽  
Dementia Prevalence ◽  
Risk Of Death ◽  
Model Based ◽  
People With Dementia ◽  
Number Of Patients ◽  
The Impact

Background: Current and future incidence and prevalence estimates of dementia are essential for public health planning. Objective: The objective was to establish prediction model of incidence and estimate the prevalence of dementia in the Chinese and worldwide population from 2020 to 2050. Methods: A model-based method was used to project the dementia prevalence from 2020 to 2050 in China, which required incidence, the mortality rate for individual without dementia, and the relative risk of death. Furthermore, we detected the impact of intervention on the prevalence projection for dementia using a simulation method. We applied the same method to other projections worldwide. Results: In 2020, the model predicted 16.25 million (95%confidence interval 11.55–21.18) persons with dementia in China. By 2050, this number would increase by approximately three-fold to 48.98 million (38.02–61.73). Through data simulation, if the incidence of dementia decreased by 10%every 10 years from 2020 after intervention and prevention, the number of dementia cases by 2050 was reduced by 11.96 million. This would reduce the economic burden by US $639.04 billion. In addition, using this model, dementia cases grew relatively slowly over the next few decades in the United States of America, the United Kingdom, and Japan, with percentage changes of 100.88%, 65.93%, and 16.20%, respectively. Conclusion: The number of people with dementia in China is large and will continue to increase rapidly. Effective interventions could reduce the number of patients drastically. Therefore, prevention and control strategies must be formulated urgently to reduce the occurrence of dementia.

scholarly journals A Literature Review of Wetland Treatment Systems Used to Treat Runoff Mixtures Containing Antibiotics and Pesticides from Urban and Agricultural Landscapes

Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3631
Author(s):  
Emily R. Nottingham ◽  
Tiffany L. Messer
Keyword(s):  
Point Source ◽  
Nitrogen Removal ◽  
Nitrate Nitrogen ◽  
Agricultural Landscapes ◽  
Emerging Contaminant ◽  
Wetland Ecosystems ◽  
Contaminant Mixtures ◽  
Wetland Treatment ◽  
Removal Processes ◽  
The Impact

Wetland treatment systems are used extensively across the world to mitigate surface runoff. While wetland treatment for nitrogen mitigation has been comprehensively reviewed, the implications of common-use pesticides and antibiotics on nitrogen reduction remain relatively unreviewed. Therefore, this review seeks to comprehensively assess the removal of commonly used pesticides and antibiotics and their implications for nitrogen removal in wetland treatment systems receiving non-point source runoff from urban and agricultural landscapes. A total of 181 primary studies were identified spanning 37 countries. Most of the reviewed publications studied pesticides (n = 153) entering wetlands systems, while antibiotics (n = 29) had fewer publications. Even fewer publications reviewed the impact of influent mixtures on nitrogen removal processes in wetlands (n = 16). Removal efficiencies for antibiotics (35–100%), pesticides (−619–100%), and nitrate-nitrogen (−113–100%) varied widely across the studies, with pesticides and antibiotics impacting microbial communities, the presence and type of vegetation, timing, and hydrology in wetland ecosystems. However, implications for the nitrogen cycle were dependent on the specific emerging contaminant present. A significant knowledge gap remains in how wetland treatment systems are used to treat non-point source mixtures that contain nutrients, pesticides, and antibiotics, resulting in an unknown regarding nitrogen removal efficiency as runoff contaminant mixtures evolve.

Model-based joint and task space control strategies for a kinematically redundant parallel manipulator

Robotica ◽  
2021 ◽  
pp. 1-17
Author(s):  
João Vitor de Carvalho Fontes ◽  
Fernanda Thaís Colombo ◽  
Natássya Barlate Floro da Silva ◽  
Maíra Martins da Silva
Keyword(s):  
Parallel Manipulator ◽  
Control Strategies ◽  
Parallel Manipulators ◽  
Torque Control ◽  
Redundancy Resolution ◽  
Task Space ◽  
Kinematic Redundancy ◽  
Model Based ◽  
The Impact ◽  
Computed Torque

Abstract One alternative to overcome the presence of singularities within Parallel Manipulators’ workspace is kinematic redundancy. This design alternative can be realized by adding an extra active joint to a kinematic chain. Due to this addition, the IKM presents an infinite number of solutions requiring a redundancy resolution scheme. Moreover, Parallel Manipulators’ control may require complex strategies due to their coupled and complex dynamic and kinematic relations. In this work, a model-free, a joint space computed torque, and a hybrid joint-task-space computed torque control strategies are experimentally compared for a kinematically redundant parallel manipulator. The latter is a novel strategy that requires the measurement of the end-effector’s pose, which is performed by an eye-to-hand limited frame rate camera. The impact of up to three kinematic redundancy levels is also experimentally evaluated using prepositioning and ongoing positioning redundancy resolution schemes. The data are assessed by evaluating a prescribed trajectory executed using a planar kinematically redundant parallel manipulator. These results indicate that kinematic redundancy can not only be used as an alternative design for reducing the presence of singular regions, as claimed in the literature, but also be used along with model-based control strategies for improving dynamic performance and accuracy of parallel manipulators.

scholarly journals Sensor bias impact on efficient aeration control during diurnal load variations

2021 ◽  
Author(s):  
Oscar Samuelsson ◽  
Gustaf Olsson ◽  
Erik Lindblom ◽  
Anders Björk ◽  
Bengt Carlsson
Keyword(s):  
Energy Efficiency ◽  
Automatic Control ◽  
Total Nitrogen ◽  
Nitrogen Removal ◽  
Oxygen Sensor ◽  
Control Strategies ◽  
Sensor Data ◽  
Negative Effects ◽  
Total Nitrogen Removal ◽  
The Impact

Abstract This study highlights the need to increase our understanding of the interplay between sensor drift and the performance of the automatic control system. The impact from biased sensors on the automatic control systems is rarely considered when different control strategies are assessed in water resource recovery facilities. Still, the harsh measurement environment with negative effects on sensor data quality is widely acknowledged. Simulations were used to show how sensor bias in an ammonium cascade feedback controller impacts aeration energy efficiency and total nitrogen removal in an activated sludge process. Response surface methodology was used to reduce the required number of simulations, and to consider the combined effect of two simultaneously biased sensors. The effects from flow variations, and negatively biased ammonium (−1 mg/L) and suspended solids sensors (−500 mg/L) reduced the nitrification aeration energy efficiency by between 7 and 25%. Less impact was seen on total nitrogen removal. There were no added non-linear effects from the two simultaneously biased sensors, apart from an interaction between a biased ammonium sensor and dissolved oxygen sensor located in the last aerated zone. Negative effects from sensor bias can partly be limited if the expected bias direction is considered when the controller setpoint-limits are defined.

Outcompeting nitrite-oxidizing bacteria in single-stage nitrogen removal in sewage treatment plants: A model-based study

2014 ◽  
Vol 66 ◽  
pp. 208-218 ◽  
Author(s):  
Julio Pérez ◽  
Tommaso Lotti ◽  
Robbert Kleerebezem ◽  
Cristian Picioreanu ◽  
Mark C.M. van Loosdrecht
Keyword(s):  
Nitrogen Removal ◽  
Sewage Treatment ◽  
Single Stage ◽  
Sewage Treatment Plants ◽  
Model Based ◽  
Nitrite Oxidizing Bacteria

Strategies for Success: The Impact of Self-Control Strategies on Behavior

2014 ◽  
Author(s):  
Christine Ringler ◽  
Andrea Morales ◽  
Steven Nowlis
Keyword(s):  
Control Strategies ◽  
Self Control ◽  
Strategies For Success ◽  
The Impact

Nitrogen removal from wastewater treatment lagoons

1999 ◽  
Vol 39 (6) ◽  
pp. 191-198 ◽  
Author(s):  
Timothy J. Hurse ◽  
Michael A. Connor
Keyword(s):  
Wastewater Treatment ◽  
Nitrogen Removal ◽  
Treatment Plant ◽  
Ammonia Removal ◽  
Contour Plot ◽  
Removal Mechanism ◽  
Dissolved Oxygen Concentration ◽  
Physical Processes ◽  
Contour Plots ◽  
Removal Processes

In an attempt to gain a better understanding of ammonia and nitrogen removal processes in multi-pond wastewater treatment lagoons, an analysis was carried out of data obtained during regular monitoring of Lagoon 115E at the Western Treatment Plant in Melbourne. To do this, a contour plot approach was developed that enables the data to be displayed as a function of pond number and date. Superimposition of contour plots for different parameters enabled the dependence of ammonia and nitrogen removal rates on various lagoon characteristics to be readily assessed. The importance of nitrification as an ammonia removal mechanism was confirmed. Temperature, dissolved oxygen concentration and algal concentration all had a significant influence on whether or not sizeable nitrifier populations developed and persisted in lagoon waters. The analysis made it evident that a better understanding of microbial, chemical and physical processes in lagoons is needed before their nitrogen removal capabilities can be predicted with confidence.

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