The effect of reactor configuration and operational mode on Microthrix parvicella bulking and foaming in nutrient removal activated sludge systems

2002 ◽  
Vol 46 (1-2) ◽  
pp. 61-64 ◽  
Author(s):  
C. Noutsopoulos ◽  
D. Mamais ◽  
A.D. Andreadakis
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Plug Flow ◽  
Selective Advantage ◽  
Operational Mode ◽  
Intermittent Aeration ◽  
Reactor Configuration ◽  
Microthrix Parvicella ◽  
Activated Sludge Systems ◽  
Removal System

Three bench-scale nutrient removal activated sludge units were used to examine the effect of the reactor configuration and the intermittent aeration mode on the growth of Microthrix parvicella. According to the results, the plug flow configuration seems to achieve satisfactory Microthrix parvicella control. The imposed concentration gradient for both RBCOD and SBCOD creates a selective advantage for the floc forming bacteria throughout the system (both the anoxic and oxic zones) and limits Microthrix parvicella growth. In terms of the operational mode, the intermittent aeration CSTR nutrient removal system promotes the growth of M.parvicella and deteriorates the settling characteristics of the activated sludge.

Causes of, and control strategies for, Microthrix parvicella bulking and foaming in nutrient removal activated sludge systems

1998 ◽  
Vol 37 (4-5) ◽  
pp. 9-17 ◽  
Author(s):  
D. Mamais ◽  
A. Andreadakis ◽  
C. Noutsopoulos ◽  
C. Kalergis
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Control Strategies ◽  
Plug Flow ◽  
Pilot Scale ◽  
Long Chain Fatty Acids ◽  
Flow Reactors ◽  
Microthrix Parvicella ◽  
And Control ◽  
Activated Sludge Systems

Bench and pilot scale nutrient removal activated sludge units were used to examine the effect of factors such as temperature, substrate type (easily biodegradable in the form of acetate and slowly biodegradable in the form of oleic acid) on Microthrix parvicella growth. The configurations examined include complete mix with and without selectors (anoxic and anaerobic) and plug flow reactors. The results indicate that low temperatures and substrates in the form of long chain fatty acids favour the growth of M. parvicella. With respect to reactor configuration, a plug flow configuration was shown to be quite effective in controlling the growth of M. parvicella and producing a sludge with good settling characteristics, while the presence of a selector, either anoxic or anaerobic, had no significant effect on the growth of M. parvicella.

Verification of anoxic phosphate uptake as the main biochemical mechanism of the “dephanox” process

1997 ◽  
Vol 35 (10) ◽  
pp. 87-94 ◽  
Author(s):  
R. Sorm ◽  
J. Wanner ◽  
R. Saltarelli ◽  
G. Bortone ◽  
A. Tilche
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Uptake Rate ◽  
Phosphate Uptake ◽  
Biochemical Mechanism ◽  
Batch Experiments ◽  
Batch Tests ◽  
Genetic Probes ◽  
Activated Sludge Systems ◽  
Removal System

The phenomenon of anoxic phosphate uptake with simultaneous denitrification was studied. For this purpose kinetic batch tests have been carried out by using the activated sludge samples from three modifications of nutrient removal activated sludge systems: two based on an anaerobic-anoxic-oxic (A2/O) system and a third on an anaerobic-oxic (A/O) system. The results showed significant differences in anoxic phosphate uptake rate between activated sludge which was alternatively exposed to anoxic conditions and activated sludge from the A/O arrangement. These differences were also accompanied by different denitrification rates. Simultaneously with batch experiments the microscopic observation of activated sludge samples was carried out. Neisser and Gram stained samples showed clear differences in shape, size and distribution of polyphosphate accumulating bacteria between A2/O and A/O Processes. Moreover, experiments performed using genetic probes confirmed the differences in microbiological composition of activated sludge samples from different nutrient removal system arrangements.

The Selector Effect on Filamentous Bulking in Long Sludge Age Activated Sludge Systems

1991 ◽  
Vol 23 (4-6) ◽  
pp. 867-877 ◽  
Author(s):  
D. M. D. Gabb ◽  
D. A. Still ◽  
G. A. Ekama ◽  
D. Jenkins ◽  
G. v. R. Marais
Keyword(s):  
Activated Sludge ◽  
Phosphorus Removal ◽  
Sufficient Conditions ◽  
Extensive Investigation ◽  
Intermittent Aeration ◽  
Nitrogen And Phosphorus ◽  
Nitrogen And Phosphorus Removal ◽  
Aeration System ◽  
Microthrix Parvicella ◽  
Activated Sludge Systems

A survey of long sludge age activated sludge plants in South Africa showed that bulking was widespread in nitrogen and nitrogen and phosphorus removal plants with the dominant causative filamentous organisms being the low F/M types 0092, 0675, 0041, Microthrix parvicella, 0914 and 1851. The literature suggests that in aerobic systems proliferation of the low F/M filaments can be controlled by aerobic selector reactors. From an extensive investigation into the selector reactors, and the effect these stimulate, it was concluded that in long sludge age systems, irrespective of whether or not a selector effect is present in the sludge, (1) under completely aerobic conditions low F/M filaments do not proliferate, (2) sequential or alternating anoxic-aerobic periods like intermittent aeration are necessary, though not sufficient, conditions for the proliferation of low F/M filaments, and (3) an aerobic selector installed on an intermittent aeration system did not control low F/M filament proliferation.

The influence of PAX-14 on activated sludge systems and in particular on Microthrix parvicella

2002 ◽  
Vol 46 (1-2) ◽  
pp. 487-490 ◽  
Author(s):  
T. Roels ◽  
F. Dauwe ◽  
S. Van Damme ◽  
K. De Wilde ◽  
F. Roelandt
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Wastewater Treatment Plants ◽  
Full Scale ◽  
Morphological Properties ◽  
Eu Directive ◽  
Solids Separation ◽  
Microthrix Parvicella ◽  
Separation Problems ◽  
Activated Sludge Systems

The amount of wastewater treatment plants (WWTP) dealing with solid separation problems has significantly increased since the new requirements of the EU Directive 271/91 on nutrient removal. In Flanders a number of the nutrient removal WWTP are affected by solid separation problems mostly attributed to Microthrix parvicella being the most common dominant species. The effect of dosing polyaluminium chloride (PAX-14) on activated sludge is illustrated for WWTP solids separation problems, in particular because of Microthrix parvicella. The effects of the addition of PAX-14 on the microbiology and the morphology of Microthrix parvicella were studied in 9 full-scale WWTPs. PAX-14 succeeded in reducing high SVI-values and controlled foaming problems whenever caused by Microthrix parvicella. Laboratory trials have shown that the dosage of PAX-14 should be less than 150 μL/L or 7 g Al3+/kg MLSS. At a dosage higher than 250 μL/L, an increase of free bacteria and a decrease of the protozoa activity are observed. In full-scale, PAX-14 is dosed at a concentration of 1.5 to 4.5 g Al3+/kg MLSS. Before addition, the mixed liquor scum layer – if present – should be removed. In our experience, the dosing should last for at least 3 weeks. During the first week, no drastic changes occur. At the end of the first week, an increase of SS and SVI is possible. The SVI and scum start to decrease after 10 to 15 days. The amount of filaments is reduced after 3 to 3½ weeks. The morphological properties of Microthrix parvicella change, while other filaments such as Nostocoida limicola and Nocardia spp. are not affected. This study proves that PAX-14 is effective in controlling bulking and foaming problems at WWTPs when they are due to Microthrix parvicella. Prediction of when the SVI will decrease and when addition should be stopped is possible.

A hypothesis for the cause of low F/M filament bulking in nutrient removal activated sludge systems

1992 ◽  
Vol 26 (6) ◽  
pp. 867-869 ◽  
Author(s):  
T.G. Casey ◽  
M.C. Wentzel ◽  
R.E. Loewenthal ◽  
G.A. Ekama ◽  
G.v.R. Marais
Keyword(s):  
Activated Sludge ◽  
Nutrient Removal ◽  
Activated Sludge Systems

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.

Design of nutrient removal activated sludge systems

2003 ◽  
Vol 47 (11) ◽  
pp. 115-122 ◽  
Author(s):  
J. Manga ◽  
J. Ferrer ◽  
A. Seco ◽  
F. Garcia-Usach
Keyword(s):  
Mathematical Model ◽  
Activated Sludge ◽  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Pilot Plant ◽  
Enhanced Biological Phosphorus Removal ◽  
Biological Phosphorus Removal ◽  
User Friendly ◽  
Biological Phosphorus ◽  
Activated Sludge Systems

A mechanistic mathematical model for nutrient and organic matter removal was used to describe the behavior of a nitrification denitrification enhanced biological phosphorus removal (NDEBPR) system. This model was implemented in a user-friendly software DESASS (design and simulation of activated sludge systems). A 484-L pilot plant was operated to verify the model results. The pilot plant was operated for three years over three different sludge ages. The validity of the model was confirmed with data from the pilot plant. Also, the utility of DESASS as a valuable tool for designing NDEBPR systems was confirmed.

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