Incidence of Sphaerotilus Natans in Laboratory Scale Activated Sludge Systems

1989 ◽  
Vol 21 (4-5) ◽  
pp. 29-41 ◽  
Author(s):  
D. M. D. Gabb ◽  
G. A. Ekama ◽  
D. Jenkins ◽  
G. v. R. Marais
Keyword(s):  
Activated Sludge ◽  
Surface Area ◽  
Volume Ratio ◽  
Full Scale ◽  
Laboratory Scale ◽  
Sphaerotilus Natans ◽  
Attached Growth ◽  
Mixed Liquor ◽  
Activated Sludge Systems

Bulking in activated sludge systems due to proliferation of Sphaerotilus natans is very common in laboratory-scale but rare in full-scale systems. From two laboratory-scale studies it is concluded that a cause for proliferation was attached growth of S.natans on the walls of the feed lines and reactor surfaces continuously seeding the mixed liquor. It is suggested that S.natans bulking in laboratory-scale systems is common compared to full-scale systems because the surface area/volume ratio of the former is orders of magnitude higher than that of the latter so that the potential for seeding from attached growths in laboratory-scale plants is correspondingly higher. It would appear that in laboratory-scale activated sludge systems regular cleaning of the feed lines and daily scrubbing of the reactor and other wetted surfaces will eliminate S.natans bulking due to seeding of the mixed liquor from these surfaces.

Evaluating the treatment performance of a full scale Activated Sludge Plant in Islamabad, Pakistan

2012 ◽  
Vol 7 (1) ◽  
Author(s):  
S. S. Fatima ◽  
S. Jamal Khan
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plant ◽  
Suspended Solids ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Full Scale ◽  
Operational Parameter ◽  
Mixed Liquor ◽  
Treatment Performance

In this study, the performance of wastewater treatment plant located at sector I-9 Islamabad, Pakistan, was evaluated. This full scale domestic wastewater treatment plant is based on conventional activated sludge process. The parameters which were monitored regularly included total suspended solids (TSS), mixed liquor suspended solids (MLSS), mixed liquor volatile suspended solids (MLVSS), biological oxygen demand (BOD), and chemical oxygen demand (COD). It was found that the biological degradation efficiency of the plant was below the desired levels in terms of COD and BOD. Also the plant operators were not maintaining consistent sludge retention time (SRT). Abrupt discharge of MLSS through the Surplus Activated sludge (SAS) pump was the main reason for the low MLSS in the aeration tank and consequently low treatment performance. In this study the SRT was optimized based on desired MLSS concentration between 3,000–3,500 mg/L and required performance in terms of BOD, COD and TSS. This study revealed that SRT is a very important operational parameter and its knowledge and correct implementation by the plant operators should be mandatory.

Microbial population dynamics in laboratory-scale activated sludge reactors

2002 ◽  
Vol 46 (1-2) ◽  
pp. 19-27 ◽  
Author(s):  
K. Kaewpipat ◽  
C.P.L. Grady
Keyword(s):  
Activated Sludge ◽  
Microbial Communities ◽  
System Performance ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Treatment Plant ◽  
Laboratory Scale ◽  
Rrna Gene ◽  
Significant Finding ◽  
Prokaryotic Community ◽  
Activated Sludge Systems

As a first step in understanding nonlinear dynamics in activated sludge systems, two laboratory-scale sequencing batch reactors were operated under identical conditions and changes in their microbial communities were followed through microscopic examination, macroscopic observation, and denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene segments from the prokaryotic community. Two experiments were performed. The first used activated sludge from a local wastewater treatment plant to start the replicate reactors. The second used the biomass from the first experiment as a source by intermixing the two and equally redistributing the biomass into the two replicate reactors. For both experiments, the two reactors behaved fairly similarly and had similar microbial communities for a period of 60 days following start-up. Beyond that, the microbial communities in the two reactors in the first experiment diverged in composition, while those in the second experiment remained fairly similar. This suggests that the degree of change occurring in replicate reactors depends upon the severity of perturbation to which they are exposed. The DGGE data showed that the bacterial communities in both experiments were highly dynamic, even though the system performance of the replicate reactors were very similar, suggesting that dynamics within the prokaryotic community is not necessarily reflected in system performance. Moreover, a significant finding from this study is that replicate activated sludge systems are not identical, although they can be very similar if started appropriately.

scholarly journals Microbial community similarity and dissimilarity inside and across full-scale activated sludge processes for simultaneous nitrification and denitrification

2020 ◽  
Vol 81 (2) ◽  
pp. 333-344
Author(s):  
Jianfeng Wen ◽  
Mark W. LeChevallier ◽  
Wendong Tao
Keyword(s):  
Microbial Community ◽  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Relative Abundance ◽  
Nitrogen Removal ◽  
Full Scale ◽  
Batch Reactors ◽  
Simultaneous Nitrification And Denitrification ◽  
Sequencing Batch Reactors ◽  
Mixed Liquor

Abstract Simultaneous nitrification and denitrification under low dissolved oxygen conditions is an energy-saving modification of the activated sludge process to achieve efficient nitrogen removal. Geographically distinct full-scale treatment plants are excellent platforms to address the links of microbial community with operating parameters. Mixed liquor samples were collected from a sequencing batch reactor plant, oxidation ditch plant, and step-feed activated sludge plant. Next-Generation Sequencing of the samples showed that the microbial communities were similar at the phylum level among the plants, being dominated by Proteobacteria. Microbial composition of functional groups was similar between the react fill and react phases of the sequencing batch reactors, among four sequencing batch reactors, and among four oxidation ditches. Nitrospira was the only identified genus of autotropic nitrifying bacteria with a relative abundance of 2.2–2.5% in the oxidation ditches and 0.4–0.7% at the other plants. Heterotrophic nitrifying–aerobic denitrifying bacteria were dominated by Dechloromonas with a relative abundance of 0.4–1.0%. Microbial community composition and nitrogen removal mechanisms were related to overall level and local zonation of dissolved oxygen, mixed liquor suspended solids concentration, nitrogen and organic loadings, and solids retention time. Low dissolved oxygen and low organic and nitrogen loadings favored growth of Nitrospira.

Quantification of ammonia-oxidizing bacteria populations in full-scale sewage activated sludge systems and assessment of system variables affecting their performance

2006 ◽  
Vol 54 (1) ◽  
pp. 91-99 ◽  
Author(s):  
T. Limpiyakorn ◽  
F. Kurisu ◽  
O. Yagi
Keyword(s):  
Activated Sludge ◽  
Real Time ◽  
Real Time Pcr ◽  
Full Scale ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Ammonia Oxidizing Bacteria ◽  
Primer Sets ◽  
Activated Sludge Systems ◽  
Pcr Primer

This study carried out quantification of ammonia-oxidizing bacteria (AOB) populations in 12 full-scale sewage activated sludge systems that were different in ammonia removals and treatment processes during three different seasons. Experiment was divided into 3 parts: 1) analysis of AOB communities by PCR-DGGE-cloning-sequencing of 16S rRNA genes; 2) development of four real-time PCR primer sets for quantification of the particular AOB of interest; and 3) quantification of AOB populations by using the newly developed real-time PCR primer sets. The results suggested that all the primer sets gave good reproducibility and specificity for PCR amplification with the detection limits of 102 copies/PCR reaction. Although the 12 systems were different in several aspects, one of the identified sequence types of Nitrosomonas oligotropha cluster was the dominant AOB in every system and every season studied. However, the other sequence type of this cluster was not significantly involved in ammonia removals in the systems. The occurrence of N. communis cluster in the systems seemed to depend on the remaining oxygen concentrations in the sludge floc and thus the activity of aerobic heterotrophs in the aeration tanks. N. europaea–Nitrosococcus. mobilis solely existed in one A2O system of which the influent contained twice the chloride concentrations than those of other systems.

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