External nitrification in biological nutrient removal activated sludge systems

2001 ◽  
Vol 43 (1) ◽  
pp. 251-260 ◽  
Author(s):  
Z.-R. Hu ◽  
M. C. Wentzel ◽  
G. A. Ekama
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Mass Fraction ◽  
Large Scale ◽  
Oxygen Demand ◽  
P Uptake ◽  
Biological Nutrient Removal ◽  
Fixed Media ◽  
Media System ◽  
Polyphosphate Accumulating Organisms

A biological nutrient removal (BNR) activated sludge (AS) scheme incorporating external nitrification in a fixed media system is evaluated. A laboratory scale investigation of the scheme indicates that it holds considerable potential for BNRAS system intensification through major reduction in sludge age and oxygen demand and significant improvement in sludge settleability. Because the BNRAS system is not required to nitrify, its anoxic mass fraction can be considerably enlarged at the expense of the aerobic mass fraction creating conditions that (i) allow it to achieve high N removals with domestic wastewaters with high TKN/COD ratios and (ii) promote anoxic P uptake polyphosphate accumulating organisms (PAO) to develop in the system. From this, and earlier investigations with conventional BNR systems, it appears that anoxic P uptake biological excess P removal (BEPR) is only about two thirds of aerobic P uptake BEPR. Inclusion of anoxic P uptake PAOs in, and exclusion of nitrifiers from, the BNRAS system are not essential for the scheme. However, conditions that promote aerobic P uptake to maximize BEPR, are also conducive to nitrifier growth, which, if supported in the BNRAS system, would require virtual complete nitrification in the fixed media system to avoid nitrate interference with BEPR. Before the scheme can be implemented at large scale, an engineering and economic evaluation is required to quantify its potential benefits and savings.

The significance of denitrifying polyphosphate accumulating organisms in biological nutrient removal activated sludge systems

2002 ◽  
Vol 46 (1-2) ◽  
pp. 129-138 ◽  
Author(s):  
Z.-R. Hu ◽  
M.C. Wentzel ◽  
G.A. Ekama
Keyword(s):  
Experimental Data ◽  
Activated Sludge ◽  
Nutrient Removal ◽  
P Uptake ◽  
Biological Nutrient Removal ◽  
Advantages And Disadvantages ◽  
Polyphosphate Accumulating Organisms ◽  
Very High ◽  
Total P ◽  
Activated Sludge Systems

In this paper the advantages and disadvantages of denitrifying PAOs (polyphosphat accumulating organisms) in conventional BNRAS (biological nutrient removal activated sludge) and external nitrification BNRAS (ENBNRAS) systems are evaluated, with experimental data exhibiting a range of anoxic P uptake from low (<10%) to very high (>60%). The results indicate that the specific denitrification rate of the PAOs on internally stored PHB COD is about 1/5th of that of the “ordinary” heterotrophic organisms on SBCOD, and the PAOs contribute little (maximum 20%) to the denitrification in BNRAS systems even when the anoxic P uptake is high (60% of the total P uptake). Considering the unpredictable nature of anoxic P uptake and the reduction in BEPR it causes compared with aerobic P uptake BEPR, it is concluded that anoxic P uptake does not add a significant advantage to the BNR system.

Difficulties and developments in biological nutrient removal technology and modelling

1999 ◽  
Vol 39 (6) ◽  
pp. 1-11 ◽  
Author(s):  
George A. Ekama ◽  
Mark C. Wentzel
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
P Uptake ◽  
Biological Nutrient Removal ◽  
Filamentous Bulking ◽  
Recent Developments ◽  
Removal Technology ◽  
Hydrolysis Of ◽  
Activated Sludge Systems ◽  
P Removal

Filamentous bulking and the long sludge age required for nitrification are two important factors that limit the wastewater treatment capacity of biological nutrient removal (BNR) activated sludge systems. A growing body of observations from full-scale plants indicate support for the hypothesis that a significant stimulus for filamentous bulking in BNR systems in alternating anoxic-aerobic conditions with the presence of oxidized nitrogen at the transition from anoxic to aerobic. In the DEPHANOX system, nitrification takes place externally allowing sludge age and filamentous bulking to be reduced and increases treatment capacity. Anoxic P uptake is exploited in this system but it appears that this form of biological excess P removal (BEPR) is significantly reduced compared with aerobic P uptake in conventional BNR systems. Developments in the understanding of the BEPR processes of (i) phosphate accumulating organism (PAO) denitrification and anoxic P uptake, (ii) fermentation of influent readily biodegradable (RB)COD and (iii) anaerobic hydrolysis of slowly biodegradable (SB)COD are evaluated in relation to the IAWQ Activated Sludge Model (ASM) No.2. Recent developments in BEPR research do not yet allow a significant improvement to be made to ASM No. 2 that will increase its predictive power and reliability and therefore it remains essentially as a framework to guide further research.

Sludge production and oxygen demand in nutrient removal activated sludge systems

1996 ◽  
Vol 34 (5-6) ◽  
pp. 43-50 ◽  
Author(s):  
P. S. Barker ◽  
P. L. Dold
Keyword(s):  
Oxygen Consumption ◽  
Activated Sludge ◽  
Nutrient Removal ◽  
Suspended Solids ◽  
Model Simulation ◽  
Oxygen Demand ◽  
Biological Nutrient Removal ◽  
Solids Concentration ◽  
Volatile Solids ◽  
Activated Sludge Systems

Results of model simulations indicate that without the assumption of COD loss, predictions of oxygen consumption and volatile suspended solids production are significantly over-estimated for biological excess phosphorus removal (BEPR) activated sludge systems (and to a lesser extent anoxic-aerobic systems). These systems apparently consume less oxygen and produce less volatile solids than aerobic systems for the same amount of COD removal. A general model for biological nutrient removal systems has recently been presented by Barker and Dold. Three mechanisms for COD loss are suggested, based on results of COD balances for different types of activated sludge system. Model simulation results with and without the assumption of COD loss are discussed, as well as the influence of influent COD composition on predictions of volatile suspended solids concentration/production and oxygen consumption.

Comparison of aerobic and anoxic phosphorus uptake in ndbepr systems (uct and enbnras)

2002 ◽  
Vol 46 (4-5) ◽  
pp. 201-207 ◽  
Author(s):  
S.M. Vermande ◽  
S. Sötemann ◽  
G. Aguilera Soriano ◽  
M. Wentzel ◽  
J.M. Audic ◽  
...  
Keyword(s):  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Mass Fraction ◽  
Phosphorus Uptake ◽  
P Uptake ◽  
Biological Nutrient Removal ◽  
P Release ◽  
University Of Cape Town ◽  
The University ◽  
P Removal

Two Nitrification-Denitrification Biological Excess Phosphorus Removal (NDBEPR) systems have been operated for 8.5 months in order to compare their Biological Excess Phosphorus Removal (BEPR) performance. One of these systems, i.e. the University of Cape Town (UCT) system, exhibits mainly aerobic P uptake while the External Nitrification Biological Nutrient Removal Activated Sludge (ENBNRAS) system is characterised by high anoxic P uptake. It was observed that when operating with predominantly aerobic P uptake, the UCT system released more P than the ENBNRAS system, even though it had a lower anaerobic mass fraction. However, when the influent TKN/COD was high, i.e. >0.1, anoxic P uptake also occurred in the UCT system and P release dropped to lower levels than in the ENBNRAS. Accordingly, P uptake of the UCT system was 5 mg P/l influent higher than that of the ENBNRAS system, when it was predominantly aerobic, but 9 mg P/l influent lower when anoxic P uptake occurred. As a result, the UCT system achieved superior P removal when aerobic P uptake was predominant (23% higher), but when high influent TKN/COD promoted anoxic P uptake the P removal of the UCT system was poorer than that of the ENBNRAS system. This study clearly showed that anoxic P uptake is not beneficial to NDBEPR systems.

Modeling the biotransformation of trimethoprim in biological nutrient removal system

2018 ◽  
Vol 2017 (1) ◽  
pp. 144-155
Author(s):  
Olumuyiwa O. Ogunlaja ◽  
Wayne J. Parker
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Pilot Scale ◽  
Biological Nutrient Removal ◽  
Ammonia Oxidizing Bacteria ◽  
Nitrification Inhibition ◽  
Batch Tests ◽  
Microbial Groups ◽  
Polyphosphate Accumulating Organisms ◽  
Removal System

Abstract A pilot scale biological nutrient removal (BNR) process, batch experiments and modeling exercises were employed to investigate the removal and biotransformation of trimethoprim (TMP) in a BNR activated sludge process. The concentrations of the active microbial groups – ammonia oxidizing bacteria (AOB), ordinary heterotrophic organisms (OHOs) and polyphosphate accumulating organisms (PAOs) – in the BNR bioreactor were quantified through modeling of the pilot bioreactor. The overall TMP removal efficiency for the pilot BNR process was 64 ± 14% while the TMP biotransformation efficiencies in the anaerobic, anoxic and aerobic zones were 22 ± 20%, 27 ± 8% and 36 ± 5% respectively. Batch tests with and without nitrification inhibition showed that AOB played a role in the biotransformation of TMP in BNR activated sludge. A pseudo first order model which incorporated the contributions of PAOs, OHOs and AOB to the overall biodegradation of TMP was found to describe the biodegradation of TMP in batch tests with and without nitrification inhibition. This model showed that PAOs, OHOs and AOB contributed towards the biotransformation of TMP in aerobic BNR activated sludge with the biotransformation rate constants following the trend of kAOB > kOHOs > kPAOs.

Considerations in the Process Design of Nutrient Removal Activated Sludge Processes

1983 ◽  
Vol 15 (3-4) ◽  
pp. 283-318 ◽  
Author(s):  
G A Ekama ◽  
I P Siebritz ◽  
G V R Marais
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Concentration Ratio ◽  
Oxygen Demand ◽  
Biological Nutrient Removal ◽  
Nitrogen And Phosphorus ◽  
Effluent Quality ◽  
Biological Nitrogen ◽  
Activated Sludge Processes ◽  
P Removal

The average influent wastewater characteristics - (i) the COD concentration, (ii) the TKN/COD concentration ratio, (iii) the rapidly biodegradable COD concentration, (iv) the maximum specific growth rate of the nitrifiers at 20°C attainable in the wastewater, (v) the maximum and minimum temperatures, and (vi) the P/COD concentration ratio - are shown to govern the design of, and effluent quality from single sludge activated sludge processes for both biological nitrogen and phosphorus removal. The TKN/COD ratio governs the selection of the process type: For the Phoredox process, complete denitrification is essential to obtain excess P removal, and this is shown to be feasible only for TKN/COD ratios less than 0,07 to 0,08 mgN/mgCOD; as the TKN/COD ratio increases above 0,08, complete denitrification becomes increasingly unlikely, and the UCT or Modified UCT processes are appropriate because in these processes complete denitrification is not essential to achieve excess P removal - in these processes N and P removal can be traded off against each other depending on the critical nutrient to be removed. Primary sedimentation significantly reduces the biological nutrient removal potential of activated sludge process because it increases the TKN/COD and P/COD ratios and reduces the COD load; however it significantly reduces the process volume and total oxygen demand.

Model based evaluation of plant improvement strategies for biological nutrient removal

1999 ◽  
Vol 39 (4) ◽  
pp. 45-53 ◽  
Author(s):  
H. M. van Veldhuizen ◽  
M. C. M. van Loosdrecht ◽  
F. A. Brandse
Keyword(s):  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
P Uptake ◽  
Biological Nutrient Removal ◽  
Adequate Description ◽  
Control Scheme ◽  
Detailed Simulation ◽  
High Fraction ◽  
Biokinetic Parameters ◽  
P Removal

An activated sludge model for biological N- and P-removal was developed, which describes anoxic and aerobic P-uptake based on bacterial metabolism. This model was tested in practice on two wastewater treatment plants, which are BCFS®-processes, which contain activated sludge with a high fraction of denitrifying P-removing bacteria (DPB's). The model appeared to be able to give an adequate description of the performance of these treatment plants under different conditions. If the process parameters are well defined almost no calibration of the biokinetic parameters was necessary. In the simulation of Dalfsen wwtp, which has a complex control scheme, it was possible to give an adequate simulation of the control actions and the concentration profiles in a rather simple way, showing that detailed simulation of these controllers was not necessary. With the calibrated model it was possible to analyse bottlenecks and give suggestions for upgrading of the concerned treatments plants. The simulation results were used in decisions on investments.

scholarly journals Modelization of Nutrient Removal Processes at a Large WWTP Using a Modified ASM2d Model

2018 ◽  
Vol 15 (12) ◽  
pp. 2817 ◽  
Author(s):  
Jakub Drewnowski ◽  
Jacek Makinia ◽  
Lukasz Kopec ◽  
Francisco-Jesus Fernandez-Morales
Keyword(s):  
Nutrient Removal ◽  
Carbon Sources ◽  
Oxygen Demand ◽  
Full Scale ◽  
Biological Nutrient Removal ◽  
Organic Substrates ◽  
Modified Model ◽  
Rate Limiting Step ◽  
Uptake Rates ◽  
Rate Limiting

The biodegradation of particulate substrates starts by a hydrolytic stage. Hydrolysis is a slow reaction and usually becomes the rate limiting step of the organic substrates biodegradation. The objective of this work was to evaluate a novel hydrolysis concept based on a modification of the activated sludge model (ASM2d) and to compare it with the original ASM2d model. The hydrolysis concept was developed in order to accurately predict the use of internal carbon sources in enhanced biological nutrient removal (BNR) processes at a full scale facility located in northern Poland. Both hydrolysis concepts were compared based on the accuracy of their predictions for the main processes taking place at a full-scale facility. From the comparison, it was observed that the modified ASM2d model presented similar predictions to those of the original ASM2d model on the behavior of chemical oxygen demand (COD), NH4-N, NO3-N, and PO4-P. However, the modified model proposed in this work yield better predictions of the oxygen uptake rate (OUR) (up to 5.6 and 5.7%) as well as in the phosphate release and uptake rates.

scholarly journals Dynamic control of nutrient-removal from industrial wastewater in a sequencing batch reactor, using common and low-cost online sensors

2015 ◽  
Vol 73 (4) ◽  
pp. 740-745 ◽  
Author(s):  
Jan Dries
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Industrial Wastewater ◽  
Sequencing Batch Reactor ◽  
Batch Reactor ◽  
Low Cost ◽  
Dynamic Control ◽  
Oxygen Demand ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

On-line control of the biological treatment process is an innovative tool to cope with variable concentrations of chemical oxygen demand and nutrients in industrial wastewater. In the present study we implemented a simple dynamic control strategy for nutrient-removal in a sequencing batch reactor (SBR) treating variable tank truck cleaning wastewater. The control system was based on derived signals from two low-cost and robust sensors that are very common in activated sludge plants, i.e. oxidation reduction potential (ORP) and dissolved oxygen. The amount of wastewater fed during anoxic filling phases, and the number of filling phases in the SBR cycle, were determined by the appearance of the ‘nitrate knee’ in the profile of the ORP. The phase length of the subsequent aerobic phases was controlled by the oxygen uptake rate measured online in the reactor. As a result, the sludge loading rate (F/M ratio), the volume exchange rate and the SBR cycle length adapted dynamically to the activity of the activated sludge and the actual characteristics of the wastewater, without affecting the final effluent quality.

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