Adaptive control of external carbon flow rate in an activated sludge process

1996 ◽  
Vol 34 (3-4) ◽  
Keyword(s):  
Adaptive Control ◽  
Activated Sludge ◽  
Flow Rate ◽  
Carbon Flow ◽  
Activated Sludge Process

Feedforward control of the external carbon flow rate in an activated sludge process

2001 ◽  
Vol 43 (1) ◽  
pp. 115-122 ◽  
Author(s):  
P. Samuelsson ◽  
B. Carlsson
Keyword(s):  
Activated Sludge ◽  
Flow Rate ◽  
Feedforward Control ◽  
Nitrate Concentration ◽  
Carbon Flow ◽  
Biological Nitrogen Removal ◽  
Biological Processes ◽  
Activated Sludge Process ◽  
Process Disturbances ◽  
Biological Nitrogen

Biological nitrogen removal in an activated sludge process is obtained by two biological processes: nitrification and denitrification. Denitrifying bacteria need sufficient amounts of readily metabolized carbon. The objective of this paper is to develop an automatic control strategy for adjusting the external carbon flow rate so that the nitrate concentration in the last anoxic compartment is kept at a low pre-specified level. A simple model based feedforward control combined with a standard feedback PI controller is suggested. Simulation results show that the suggested controller, despite being simple, effectively attenuates process disturbances.

Sensitivity of Effluent Variables in Activated Sludge Process

2017 ◽  
Vol 13 (2) ◽  
Author(s):  
B Vivekanandan ◽  
K Jeyannathann ◽  
A. Seshagiri Rao
Keyword(s):  
Activated Sludge ◽  
Flow Rate ◽  
Oxygen Transfer Rate ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Maximum Flow ◽  
Activated Sludge Process ◽  
Flow Conditions ◽  
Treated Effluent ◽  
Influent Flow

Abstract The quality of a treated effluent changes when there is a sudden variation in the influent flow to the wastewater treatment plant during dry, rain, and storm weather conditions. In this study, various influent flow conditions in an activated sludge process are considered that affect the sensitivity of effluent variables such as chemical oxygen demand (COD), biological oxygen demand (BOD), nitrate nitrogen (SNO), ammonical nitrogen (SNH), and total nitrogen (TN) with respect to varying internal recycle flow rate (Qa), sludge recycle flow rate (Qr), sludge wastage flow rate (Qw) and oxygen transfer rate co-efficient of aerobic tanks (KLa(3,4,5)). The analysis has been carried out based on benchmark simulation model no.1 (BSM 1) plant layout which comprises of two models namely activated sludge model no.1 (ASM 1) and simple one dimensional (Simple 1-D) Takacs model. Based on the present analysis, it is observed that the changes in influent flow rate have larger impact on the effluent variables. This variation can be subdued by introducing additional tanks to smoothen the perturbations or using internal recycle rate from the fifth tank in order to maintain the flow around the optimal influent flow rate. The sludge wastage rate has a greater impact on all effluent variables except nitrogenous variables during maximum flow conditions.

Fuzzy Control of a Dynamic Activated Sludge Process for the Forecast and Control of Effluent Suspended Solid Concentration

1993 ◽  
Vol 28 (11-12) ◽  
pp. 355-367 ◽  
Author(s):  
Y. P. Tsai ◽  
C. F. Ouyang ◽  
M. Y. Wu ◽  
W. L. Chiang
Keyword(s):  
Fuzzy Control ◽  
Activated Sludge ◽  
Flow Rate ◽  
Suspended Solid ◽  
Aeration Tank ◽  
Activated Sludge Process ◽  
Solid Concentration ◽  
Suspended Solid Concentration ◽  
And Control ◽  
Influent Flow

The effluent total BOD (or COD) concentration of the activated sludge process (A.S.P.) usually increases with suspended solid concentration. How to reduce effluent S.S. concentration, therefore, is the key issue of treatment efficiency for A.S.P. The varied return sludge and influent flow rate are two major operational factors of those affecting effluent S.S. concentration. However, the wastewater flow rate and substrate concentration in municipal wastewater treatment plant, due to the differences of city scale and life style, are significantly time-varied every day. Based on the above, the purpose of this study is to control in timely fashion return sludge flow rate with the variation of influent flow rate to minimize effluent S.S. concentration and meanwhile decrease the effluent total BOD (or COD) concentration. The fuzzy control theory is utilized in this study to forecast and control effluent S.S. concentration and further predict the MLSS concentration in aeration tank. It reveals that the inferred control strategies not only enable one to decrease effluent S.S.

Modelling Simulation and Control of an Existing Activated Sludge Wastewater Treatment Process

1976 ◽  
Vol 11 (1) ◽  
pp. 108-121
Author(s):  
N. Thérien ◽  
P. Harrington
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Flow Rate ◽  
Treatment Plant ◽  
Organic Substrate ◽  
Activated Sludge Process ◽  
Two Phase ◽  
Wastewater Treatment Process ◽  
Wastewater Stream ◽  
And Control

Abstract The dynamic response of the activated sludge process in the wastewater treatment plant of the Centre Hospitalier Universitaire de Sherbrooke was analysed with respect to large disturbances in both the flow rate and the quality of wastewater entering the plant. A mass balance conducted for the organic substrate and biomass entering and leaving the process led to a model consisting of two separate differential equations in terms of BOD and VSS with a two-phase bio-kinetic relationship for the reaction term. Predictions of the model for BOD and VSS variations in time were compared to experimental observations at the plant. A model using mean daily values for VSS and expressed in terms of BOD for the stream flowing out the clarifier unit in response to flow rate and BOD cyclic fluctuations of the entering wastewater stream to the process was found apt at describing the time at which BOD peaks in the process effluent occurred as well as predicting the magnitude of these peaks. The dynamic behaviour of the activated sludge process has been simulated for periods of one to several days using this model. Its use in predicting appropriate control action in time in order to improve the treatment efficiency is also indicated.

Control of an activated sludge process with nitrogen removal – a benchmark study

2002 ◽  
Vol 45 (4-5) ◽  
pp. 135-142 ◽  
Author(s):  
B. Carlsson ◽  
A. Rehnström
Keyword(s):  
Activated Sludge ◽  
Flow Rate ◽  
Control Strategies ◽  
Ammonia Level ◽  
Physical Models ◽  
Activated Sludge Process ◽  
Nitrate Level ◽  
Recirculation Flow ◽  
Set Up ◽  
Aeration Capacity

In this paper, a simulation benchmark of a predenitrifying activated sludge process is used to evaluate a number of control strategies. A main procedure has been to use feedforward terms that are based on simplified physical models. Important mass balance relations may then be incorporated in the control law. The nitrate level in the last anoxic zone is controlled by the dosage of an external carbon source and the nitrate level in the last aerobic zone is controlled by the internal recirculation flow rate. The ammonia level is controlled by a DO set-point controller. In order to be able to have as high a sludge level as possible without sludge escape, the sludge blanket height in the settler is controlled by the excess sludge flow rate. Compared to the default set up of the benchmark, the controllers could reduce the effluent nitrate significantly whereas the effluent ammonia was only marginally decreased. The main problem is that the aeration capacity defined in the benchmark is too low.

Adaptive control of external carbon flow rate in an activated sludge process

1996 ◽  
Vol 34 (3-4) ◽  
pp. 173-180 ◽  
Author(s):  
Carl-Fredrik Lindberg ◽  
Bengt Carlsson
Keyword(s):  
Flow Rate ◽  
Control Strategy ◽  
Nitrate Concentration ◽  
Reference Value ◽  
Pilot Scale ◽  
External Flow ◽  
Carbon Flow ◽  
Activated Sludge Process ◽  
Anoxic Zone ◽  
Nitrate Sensor

In this study an adaptive carbon flow rate controller is applied to a pre-denitrifying pilot-scale plant. The goal of the control strategy is to maintain a low nitrate concentration in the anoxic zone by controlling the external flow rate of the carbon source. Results from practical experiments show that the control strategy works well and the nitrate concentration could be kept close to a desired set-point (reference value). The used nitrate sensor needed, however, frequent maintenance. During the experiment the carbon flow rate was automatically varied to keep the nitrate concentration at a constant low level. We conclude that a low effluent nitrate concentration without an excessive carbon flow rate is hard to achieve without an automatic control strategy.

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