Biological nutrient removal in membrane bioreactors: denitrification and phosphorus removal kinetics

2007 ◽  
Vol 56 (6) ◽  
pp. 125-134 ◽  
Author(s):  
V. Parco ◽  
G. du Toit ◽  
M. Wentzel ◽  
G. Ekama
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Biological Nutrient Removal ◽  
Specific Rate ◽  
Mixed Liquor ◽  
Batch Tests ◽  
The Impact ◽  
Substrate Concentrations ◽  
P Removal

The impact of including membranes for solid liquid separation on the kinetics of nitrogen and phosphorus removal was investigated. To achieve this, a membrane bioreactor (MBR) biological nutrient removal (BNR) activated sludge system was operated. From batch tests on mixed liquor drawn from the MBR BNR system, denitrification and phosphorus removal rates were delineated. Additionally the influence of the high total suspended solids concentrations present in the MBR BNR system and of the limitation of substrate concentrations on the kinetics was investigated. Moreover the ability of activated sludge in this kind of system to denitrify under anoxic conditions with simultaneous phosphate uptake was verified and quantified. The denitrification rates obtained for different mixed liquor (ML) concentrations indicate no effect of ML concentration on the specific denitrification rate. The denitrification took place at a single specific rate (K2) with respect to the ordinary heterotrophic organisms (OHOs, i.e. non-PAOs) active mass. Similarly, results have been obtained for the P removal process kinetics: no differences in specific rates were observed for different ML or substrate concentrations. From the P removal batch tests results it seems that the biological phosphorus removal population (PAO) consists of 2 different sets of organisms denitrifying PAO and aerobic PAO.

Nutrient Removal Technology in North America and the European Union: A Review

2006 ◽  
Vol 41 (4) ◽  
pp. 449-462 ◽  
Author(s):  
Jan A. Oleszkiewicz ◽  
James L. Barnard
Keyword(s):  
European Union ◽  
North America ◽  
Activated Sludge ◽  
Total Nitrogen ◽  
Total Phosphorus ◽  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Biological Nutrient Removal ◽  
The European Union ◽  
The Impact

Abstract The European Union (EU) has implemented effluent (emission) standards since 1991, while North America practices a riskbased, imission approach. Progressing eutrophication and large fees for discharged loads push EU countries toward more stringent effluent concentrations, below total nitrogen (TN) levels of 10 mg/L and total phosphorus (TP) levels of 1 mg/L. In North America, the limit of treatment technology (LOT) concept has been defined as the lowest economically achievable effluent quality, which for TN is <1.5 to 3 mg/L and TP is <0.07 mg/L. These limits are becoming targets in fragile ecoregions in North America and drive the technology solutions towards a combination of advanced biological nutrient removal process trains, followed by chemical polishing and solids separation by granular or cloth filters or membranes. In Western Canada one-biomass biological nutrient removal processes are used, such as Westbank or Step-feed, often followed by filtration to achieve low effluent total phosphorus levels. Eastern Canada has a less stringent approach to nitrogen control and practices chemical phosphorus removal. Requirement for total nitrogen removal and rising costs of phosphorus precipitation drive designers towards advanced one-biomass processes and full utilization of carbon (for denitrification and phosphorus removal) available in raw wastewater and primary sludge. New processes are developed to take advantage of carbon available in waste activated sludge or even in the recycled activated sludge. Sludge treatment return streams have high nutrient loads and novel processes are introduced for their treatment, some utilizing generated nitrifier biomass for bio-augmentation of the main stream nitrification process. The impact of sludge processing on the liquid train and vice versa is now fully embedded in the design process.

Design Considerations for Nutrient Removal Activated Sludge Plants

1991 ◽  
Vol 23 (4-6) ◽  
pp. 781-790 ◽  
Author(s):  
A. R. Pitman
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Full Scale ◽  
Biological Nutrient Removal ◽  
Biological Phosphorus Removal ◽  
Anoxic Zone ◽  
Mixed Liquor ◽  
Design Considerations ◽  
Biological Phosphorus

Based on more than 10 years' experience with biological nutrient removal in Johannesburg, this paper highlights aspects which should be borne in mind in the design of such processes. Feed sewage quality and the question of treating raw or settled sewage are considered. More importantly, methods of rendering the feed more suitable for biological phosphorus removal are detailed. As nitrate feedback to the anaerobic zone can often mitigate against good phosphorus removal, methods of obviating this are covered. In this respect the need for, and placement of a second anoxic zone are discussed. Process type and configuration are covered as well as zone retention periods and the split of process volume into unaerated and aerated fractions. Aeration systems and the tailoring of aeration to process needs are also discussed. Two problems that have been experienced in many full-scale plants are bulking sludges and prolific growths of nuisance scums. Methods of minimising these problems are discussed. Finally, mixed liquor and return sludge recycles; aspects to be borne in mind in the design of final clarifiers and the provision of standby chemical addition are discussed.

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.

Practical Experience with Biological Phosphorus Removal Plants in Johannesburg

1983 ◽  
Vol 15 (3-4) ◽  
pp. 233-259 ◽  
Author(s):  
A R Pitman ◽  
S L V Venter ◽  
H A Nicholls
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Operating Experience ◽  
Practical Experience ◽  
Biological Nutrient Removal ◽  
Biological Phosphorus Removal ◽  
Factors Affecting ◽  
Process Improvements ◽  
Biological Phosphorus

This paper describes three years operating experience with two full-scale biological nutrient removal activated sludge plants. Factors affecting biological phosphorus removal are highlighted and possible process improvements suggested.

Efficient Biological Nutrient Removal in a Membrane Bioreactor Using Denitrifying Phosphorus Removal and Simultaneous Nitrification and Denitrification

2014 ◽  
Vol 507 ◽  
pp. 693-701
Author(s):  
Jiu Yi Li ◽  
Nian Peng Wu ◽  
Jin Li ◽  
Ai Min Wang ◽  
Yong Chen ◽  
...  
Keyword(s):  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Membrane Bioreactor ◽  
Phosphorus Release ◽  
Biological Nutrient Removal ◽  
Return Flow ◽  
Denitrifying Phosphorus Removal ◽  
Bioreactor System ◽  
Removal Processes ◽  
The Impact

Biological nutrient removal (BNR) is generally integrated in municipal wastewater treatment plants to alleviate the impact of treated effluent on receiving watersheds. This paper studies the performance of BNR in a membrane bioreactor system consisting of anaerobic, anoxic, micro-aerobic and aerobic compartments treating a synthetic wastewater containing low organic matters. The membrane bioreactor system designed an anti-stream, stepwise return flow scheme to produce ideal conditions for the occurrence of simultaneous nitrification and denitification and denitrifying phosphorus removal processes. The proposed membrane reactor system has established higher biomass concentrations and ideal environments for biological nutrient removal processes, which results in high nutrient removal efficiencies treating low organic wastewaters. Four compartment configurations in the reactor system minimized the impact of oxidized nitrogen species in return flow on phosphorus release in the anaerobic tank and the anti-stream, stepwise return flow scheme encouraged the utilization of nitrate as the electronic acceptor in phosphorus uptake in the micro-aerobic tank. Denitrifying phosphorus removal and simultaneous nitrification and denitrification processes are the main mechanisms responsible for efficient nutrient removal. High phosphorus release activities and high phosphate concentration in the anaerobic tank make it is potentially feasible to recover phosphorus resource from wastewater.

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.

Nitrification Kinetics in Single-Sludge Biological Nutrient Removal Activated Sludge Systems

1992 ◽  
Vol 25 (6) ◽  
pp. 195-214 ◽  
Author(s):  
C. W. Randall ◽  
V. M. Pattarkine ◽  
S. A. McClintock
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Municipal Wastewater ◽  
Biomass Concentration ◽  
Biological Nutrient Removal ◽  
Mixed Liquor ◽  
Nitrification Kinetics ◽  
Anoxic Zones ◽  
Complete Nitrification ◽  
Activated Sludge Systems

Nitrification kinetics as a function of mixed liquor temperature were compared for a conventional fully-aerobic activated sludge system and a system accomplishing biological nutrient removal (BNR) by incorporation of anaerobic and anoxic zones using the UCT configuration. The systems treated the same municipal wastewater and both had flow rates of 151 L/day. The nitrification rates were greater in the nutrient removal system compared to the conventional system as long as the aerobic MCRT was above the minimum for complete nitrification. It was concluded that BNR systems require less aerobic volume than fully aerobic systems to accomplish nitrification because the aerobic biomass concentration is greater in the BNR systems, particularly if the UCT configuration is used. Nonetheless, BNR systems require more total volume to accomplish complete nitrification than fully aerobic systems, and the volume differential increases as mixed liquor temperatures decrease.

scholarly journals Optimizing water and resource recovery facilities (WRRF) for energy generation without compromising effluent quality

Water SA ◽  
2021 ◽  
Vol 47 (2 April) ◽  
Author(s):  
George A Ekama
Keyword(s):  
Activated Sludge ◽  
Energy Generation ◽  
Resource Recovery ◽  
Biological Nutrient Removal ◽  
Effluent Quality ◽  
P Content ◽  
Primary Separation ◽  
The Impact ◽  
Final Effluent ◽  
P Removal

The primary separation unit (PSU) splits the organic load on the water and resource recovery facility (WRRF) between the primary sludge (PS) anaerobic digester (AD), where energy can be generated, and the biological nutrient removal (BNR) activated sludge (AS) reactor, where energy is consumed. With a CHONP element mass-balanced plant-wide stoichiometric and kinetic steady-state model, this paper explores quantitatively the impact of four cases of increasing organics removal efficiencies in the PSU on (i) settled wastewater characteristics, (ii) balanced solids retention time (SRT) of the Modified Ludzack-Ettinger (MLE) and University of Cape Town/Johannesburg (UCT/JHB) systems for lowest economical effluent N and P concentrations, (iii) reactor volume, (iv) energy consumption for aeration, pumping and mixing, (v) energy generation by AD of PS and waste activated sludge (WAS), (vi) N&P content of the PS and WAS AD dewatering liquor (DWL) and (vii) final effluent N and P concentrations with and without enhanced biological P removal (EBPR), and looks for an optimum WRRF layout for maximum energy recovery without compromising effluent quality. For the low biogas yield from the WAS AD, decreasing as the SRT of the BNRAS system gets longer and with the added complexity of N&P removal from the digested sludge DWL, makes AD of WAS undesirable unless P recovery is required. Because the wastewater biodegradable particulate organics (BPO) have a low N&P content, it is better to divert more biodegradable particulate organics to the PSAD with enhanced primary separation than digest WAS – the PSAD DWL can be returned to the influent with relatively small impact on final effluent N and P concentration.

Treatment of a milkpowder/butter wastewater using the AAO activated sludge configuration

1997 ◽  
Vol 36 (10) ◽  
pp. 79-86 ◽  
Author(s):  
Michael J. Donkin ◽  
John M. Russell
Keyword(s):  
Activated Sludge ◽  
Removal Efficiency ◽  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Suspended Solids ◽  
Synthetic Wastewater ◽  
Biological Nutrient Removal ◽  
In Series ◽  
Aerobic Reactor ◽  
Original Size

A laboratory-scale nutrient removal activated sludge system, based on the AAO configuration, was used to treat a synthetic wastewater from a milkpowder/butter factory. In this system, substrate is fed to anaerobic and anoxic selectors in series with an aerobic reactor. Sludge is returned to the anaerobic selector, and mixed liquor from the aerobic reactor is recycled to the anoxic selector. The overall system is operated at an HRT of 7 days and a nominal sludge age of 20 days. This system was prone to prolonged bulking periods, with filamentous bacteria Sphaerotilus natans, Type 0411 and Haliscomenobacter hydrossis being identified in the mixed liquors, although effective clarifier operation prevented loss of suspended solids. Theory suggests that selectors may be used to circumvent low F:M bulking, and to bring about enhanced biological nutrient removal. An investigation of the initial design revealed that relatively high nitrite levels were present in the system, and a larger anoxic selector with an HRT of 820 minutes was substituted for the original one with an HRT of 48 minutes. This resulted in a decrease in nitrite and a equivalent increase in nitrate in the system. Overall nitrogen removal remained unchanged at 66%, and SVI levels did not improve. On resetting the anoxic selector to its original size, the effect was not reversed. Phosphorus removal efficiency was detrimentally affected by the anoxic sizing experiment (49% to 20%), and this may be linked to the raised level of nitrate in the system. COD removal efficiency remained excellent throughout the trial at over 90% removal.

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