scholarly journals The use of simultaneous chemical precipitation in modified activated sludge systems exhibiting biological excess phosphate removal: Part 6: Modelling of simultaneous chemical-biological P removal - review of existing models

Water SA ◽  
2004 ◽  
Vol 27 (2) ◽  
Author(s):  
DW De Haas ◽  
MC Wentzel ◽  
GA Ekama
Keyword(s):  
Activated Sludge ◽  
Chemical Precipitation ◽  
Phosphate Removal ◽  
Activated Sludge Systems ◽  
P Removal

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.

Enhanced nutrient removal MBR system with chemical addition for low effluent TP

2011 ◽  
Vol 64 (6) ◽  
pp. 1298-1306 ◽  
Author(s):  
Wen-jun Liu ◽  
Zhi-rong Hu ◽  
R. L. Walker ◽  
P. L. Dold
Keyword(s):  
Activated Sludge ◽  
Model Simulation ◽  
Chemical Precipitation ◽  
Pilot Test ◽  
Activated Sludge Model ◽  
Effluent Quality ◽  
Precipitation Model ◽  
Optimizing Design ◽  
Dynamic Loading Conditions ◽  
P Removal

A pilot study was conducted to test an membrane bioreactor (MBR) process for combined biological and chemical P removal to achieve a very low effluent total phosphorus (TP) concentration of 0.025 mg P/L. With the data from the pilot test, a simulation study was performed to demonstrate that: (1) the pilot system behaviour (effluent quality, MLSS, etc.) can be modelled accurately with an activated sludge model combined with a chemical precipitation model; and (2) with the calibrated model, simulation scenarios can be performed to further understand the pilot MBR process, and provide information for optimizing design and operation when applied at full-scale. Results from the pilot test indicated that the system could achieve very low effluent TP concentration through biological P removal with a limited chemical addition, and chemical addition to remove P to very low level did not affect other biological processes, i.e., organic and nitrogen removal. Simulation studies indicate that the process behaviour can be modelled accurately with an activated sludge model combined with a chemical precipitation model, and the calibrated model can be used to provide information to optimize system design and operation, e.g., chemical addition control under dynamic loading conditions is important for maintaining biological P removal.

Observations Supporting Phosphate Removal by Biologically Mediated Chemical Precipitation – A Review

1983 ◽  
Vol 15 (3-4) ◽  
pp. 43-63 ◽  
Author(s):  
Erik Arvin
Keyword(s):  
Biological Treatment ◽  
Chemical Precipitation ◽  
Phosphate Removal ◽  
Bulk Precipitation ◽  
Low Magnesium ◽  
Removal Mechanisms ◽  
Precipitation Inhibitors ◽  
Polyphosphate Accumulation ◽  
Bicarbonate Alkalinity ◽  
P Removal

Chemical precipitation of phosphorus in biological treatment plants may be mediated biologically in at least two ways. First the elevated P-concentrations created by anaerobic phosphate release from bacteria can initiate and accelerate calcium phosphate precipitation. Secondly biological denitrification in fixed biofilms and possibly also in bacterial floes can lead to phosphate precipitation due to the elevated pH-conditions inside the biofilms. In both cases the bulk precipitation conditions must be generally favourable, i.e. the calcium concentration should be reasonably high, roughly above 50 mg/ℓ, and the concentration of precipitation inhibitors low: magnesium, pyrophosphates and bicarbonate (alkalinity). With respect to accelerated bulk precipitation it is also essential that the pH is relatively high, preferably above 7.5. Biologically mediated phosphate precipitation is only two P-removal mechanisms out of several mechanisms. Apart from normal biological P-assimilation phosphate can be removed through polyphosphate accumulation in bacteria and through normal chemical bulk precipitation. The paper gives a survey of the mechanisms. Virtually all the published literature on P-removal in biological treatment plants contain insufficient data to evaluate the alternative P-removal mechanisms. In particular there is a need for agreement on procedures with which to characterize the P-fractions in the sludge in order to determine how much P is removed by the bacteria and by mineral phases. Still much qualitative and quantitative knowledge is required on both the biological and chemical P-removal mechanisms before reasonable optimization strategies and design criteria can be outlined.

Denitrification kinetics in biological N and P removal activated sludge systems treating municipal wastewaters

1999 ◽  
Vol 39 (6) ◽  
pp. 69-77 ◽  
Author(s):  
George A. Ekama ◽  
Mark C. Wentzel
Keyword(s):  
Activated Sludge ◽  
Phosphorus Removal ◽  
P Uptake ◽  
Active Fraction ◽  
Batch Tests ◽  
P Release ◽  
Denitrification Kinetics ◽  
Nd Systems ◽  
Activated Sludge Systems ◽  
P Removal

The denitrification kinetics at 12, 20 and 30°C in nitrification denitrification biological excess phosphorus removal (NDBEPR) systems were delineated in batch tests on sludge harvested from laboratory scale M/UCT systems. In some investigations, it was found that the P release and uptake were confined exclusively (>95%) to the anaerobic and aerobic reactors respectively and the observed P removal conformed to the BEPR model of Wentzel et al. In these investigations, due to an absence of anoxic P uptake (substantiated by PHB measurements), it could be inferred that the phosphate accumulating organisms (PAOs) did not significantly contribute to the denitrification. The ordinary heterotrophic organism (OHO) and PAO groups were separated with the aid of the BEPR model of Wentzel et al. Ascribing the denitrification to the OHO group performing this process, the specific rates of denitrification associated with the utilization of slowly biodegradable COD (SBCOD) in the primary (K′2) and secondary (K′3) anoxic reactors were calculated and compared with the rates in ND systems (K2 and K3). In other investigations it was found that P release and uptake were not confined exclusively to the anaerobic and aerobic reactors respectively and the observed P removal was only about 60% of that expected from the BEPR model of Wentzel et al. In these investigations significant P uptake under anoxic conditions was observed so the PAOs may have been involved with the denitrification. However, the denitrification rates were calculated as before by attributing it exclusively to the OHOs. Widely varying K'2 rates were observed at 20°C, ranging from 0.071 to 0.335 mgNO3-N/(mgAHVSS.d). The variation in K' rate is mainly due to widely varying OHO active fraction estimates for NDBEPR systems.

Phosphate and Nitrogen Removal Programme in The Netherlands

1993 ◽  
Vol 27 (5-6) ◽  
pp. 307-316
Author(s):  
Rob den Engelse
Keyword(s):  
Drinking Water ◽  
The Netherlands ◽  
Activated Sludge ◽  
Nitrogen Removal ◽  
Phosphate Removal ◽  
Market Situation ◽  
Nitrogen And Phosphate Removal ◽  
The Relationship ◽  
Initial Results ◽  
Activated Sludge Systems

A programme of research is being conducted in the Netherlands in the period 1990-1992 to find answers to the questions and solutions to the difficulties involved in the introduction of extensive nitrogen and phosphate removal. The purpose, organisation and implementation of the programme are considered. The most important initial results are set out relating to the clogging of aeration elements on simultaneous phosphate removal in activated sludge systems, to a guide to biological phosphate removal, phosphate stripping, the relationship between softening drinking water and phosphate removal and the market situation for chemicals for phosphate removal.

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