Predator grazing effect on bacterial size distribution and floc size variation in membrane-separation activated sludge

2000 ◽  
Vol 42 (3-4) ◽  
pp. 211-217 ◽  
Author(s):  
B.S. Luxmy ◽  
F. Nakajima ◽  
K. Yamamoto
Keyword(s):  
Activated Sludge ◽  
Size Distribution ◽  
Membrane Separation ◽  
Bacterial Species ◽  
Treatment Plant ◽  
Size Variation ◽  
Predator Population ◽  
Predator Species ◽  
Floc Size ◽  
Grazing Effect

In this study the role of higher organisms and the effect of their predation on bacterial size distribution as well as on floc size variation were investigated in the membrane-separation activated sludge system. The pilot plant study was conducted by setting a membrane-separation bioreactor (MBR) in a wastewater treatment plant in Tokyo, Japan. A large number of predator organisms were observed in the MBR dominated by ciliated protozoa. The dispersed bacterial size distribution was obtained by using the combination of florescent in situ hybridization (FISH) and image analysis technique. With the increase of predator species especially sessile ciliates and free-swimming ciliates, reduction of smaller bacterial population (1 μm or so) was significant. It was found that, bacteria and predators are negatively correlated i.e. with increasing number of predator organisms the number of dispersed bacteria decreased. This effect of predation was confirmed while observing the floc size distribution with an automatic particle distribution measuring instrument simultaneously. It was observed that when the higher predator organisms (protozoa and metazoa) were high in number, the percentage of floc groups less than 10 μm (optimum prey size for most of the ciliate species) were less and vice versa. From this study it can be concluded that, mainly the smaller flocs which mostly consist of small (<1 μm) dispersed bacterial species, were grazed heavily by the predator population in the membrane-separation activated sludge.

Floc size distribution and bacterial activities in membrane separation activated sludge processes for small-scale wastewater treatment/reclamation

1997 ◽  
Vol 35 (6) ◽  
pp. 37-44 ◽  
Author(s):  
Boran Zhang ◽  
Kazuo Yamamoto ◽  
Shinichiro Ohgaki ◽  
Naoyuki Kamiko
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Membrane Separation ◽  
Small Scale ◽  
Nitrification Rate ◽  
Floc Size ◽  
Denitrification Activity ◽  
Concentration Changes ◽  
Activated Sludge Processes

Activated sludges taken from full-scale membrane separation processes, building wastewater reuse system (400m3/d), and two nightsoil treatment plants (50m3/d) as well as laboratory scale membrane separation bioreactor (0.062m3/d) were analyzed to characterize membrane separation activated sludge processes (MSAS). They were also compared with conventional activated sludges(CAS) taken from municipal wastewater treatment plants. Specific nitrification activity in MSAS processes averaged at 2.28gNH4-N/kgMLSS.h were higher than that in CAS processes averaged at 0.96gNH4-N/kgMLSS.h. The denitrification activity in both processes were in the range of 0.62-3.2gNO3-N/kgMLSS.h without organic addition and in the range of 4.25-6.4gNO3-N/kgMLSS.h with organic addition. The organic removal activity in nightsoil treatment process averaged at 123gCOD/kgMLSS.h which was significantly higher than others. Floc size distributions were measured by particle sedimentation technique and image analysis technique. Flocs in MSAS processes changed their sizes with MLSS concentration changes and were concentrated at small sizes at low MLSS concentration, mostly less than 60 μm. On the contrary, floc sizes in CAS processes have not much changed with MLSS concentration changes and they were distributed in large range. In addition, the effects of floc size on specific nitrification rate, denitrification rate with and without organic carbon addition were investigated. Specific nitrification rate was decreased as floc size increased. However, little effect of floc size on denitrification activity was observed.

Study of factors affecting simultaneous nitrification and denitrification (SND)

1999 ◽  
Vol 39 (6) ◽  
pp. 61-68 ◽  
Author(s):  
Klangduen Pochana ◽  
Jürg Keller
Keyword(s):  
Carbon Source ◽  
Activated Sludge ◽  
Physical Phenomenon ◽  
Treatment Plant ◽  
Batch Reactors ◽  
Sequencing Batch Reactors ◽  
Factors Affecting ◽  
Floc Size ◽  
Sludge Flocs ◽  
Activated Sludge Systems

Experiments have been performed to gain an understanding of the conditions and processes governing the occurrence of SND in activated sludge systems. Sequencing batch reactors (SBRs) have been operated under controlled conditions using the wastewater from the first anaerobic pond in an abattoir wastewater treatment plant. Under specific circumstances, up to 95% of total nitrogen removal through SND has been found in the system. Carbon source and oxygen concentrations were found to be important process parameters. The addition of acetate as an external carbon source resulted in a significant increase of SND activity in the system. Stepwise change of DO concentration has also been observed in this study. Experiments to determine the effect of the floc size on SND have been performed in order to test the hypothesis that SND is a physical phenomenon, governed by the diffusion of oxygen into the activated sludge flocs. Initial results support this hypothesis but further experimental confirmation is still required.

scholarly journals Simulation of Floc Size Distribution in Flocculation of Activated Sludge Using Population Balance Model with Modified Expressions for the Aggregation and Breakage

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Zhenliang Li ◽  
Peili Lu ◽  
Daijun Zhang ◽  
Fuzhong Song
Keyword(s):  
Activated Sludge ◽  
Size Distribution ◽  
Velocity Gradient ◽  
Population Balance ◽  
Balance Model ◽  
Population Balance Model ◽  
Collision Efficiency ◽  
Volume Percentage ◽  
Floc Size ◽  
Breakage Rate

The floc size distribution of activated sludge was simulated successfully by population balance model in the previous study (Population Balance Model and Calibration Method for Simulating the Time Evolution of Floc Size Distribution of Activated Sludge Flocculation. Desalination and Water Treatment, 67, 41-50). However, nonignorable errors exist in the simulation for the volume percentage of large flocs. This paper describes the application of a modified population balance model in the simulation of the time evolution of floc size distribution in activated sludge flocculation process under shear-induced conditions. It was found that the application of modified size dependent collision efficiency, modified breakage rate expression by assuming a maximum value, and binominal daughter-particles distribution function could improve the population balance model for activated sludge flocculation and successfully predict the dynamic changes in volume percentage distribution and mean floc size of activated sludge under different shear conditions. The results demonstrate that the maximum breakage rate was independent on the velocity gradient, and both the collision efficiency and breakage rate coefficient show a power-law relationship with the average velocity gradient; the former decreases while the latter increases with the rise of the average velocity gradient. These findings would help to understand the dynamics of activated sludge flocculation.

scholarly journals Quantification of Hyphomicrobium Populations in Activated Sludge from an Industrial Wastewater Treatment System as Determined by 16S rRNA Analysis

2000 ◽  
Vol 66 (3) ◽  
pp. 1167-1174 ◽  
Author(s):  
A. C. Layton ◽  
P. N. Karanth ◽  
C. A. Lajoie ◽  
A. J. Meyers ◽  
I. R. Gregory ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
16S Rrna ◽  
Activated Sludge ◽  
16S Rdna ◽  
Industrial Wastewater ◽  
Bacterial Species ◽  
Treatment Plant ◽  
Rrna Gene ◽  
16S Rrna Analysis ◽  
Industrial Wastewater Treatment

ABSTRACT The bacterial community structure of the activated sludge from a 25 million-gal-per-day industrial wastewater treatment plant was investigated using rRNA analysis. 16S ribosomal DNA (rDNA) libraries were created from three sludge samples taken on different dates. Partial rRNA gene sequences were obtained for 46 rDNA clones, and nearly complete 16S rRNA sequences were obtained for 18 clones. Seventeen of these clones were members of the beta subdivision, and their sequences showed high homology to sequences of known bacterial species as well as published 16S rDNA sequences from other activated sludge sources. Sixteen clones belonged to the alpha subdivision, 7 of which showed similarity to Hyphomicrobium species. This cluster was chosen for further studies due to earlier work onHyphomicrobium sp. strain M3 isolated from this treatment plant. A nearly full-length 16S rDNA sequence was obtained fromHyphomicrobium sp. strain M3. Phylogenetic analysis revealed that Hyphomicrobium sp. strain M3 was 99% similar to Hyphomicrobium denitrificans DSM 1869T inHyphomicrobium cluster II. Three of the cloned sequences from the activated sludge samples also grouped with those ofHyphomicrobium cluster II, with a 96% sequence similarity to that of Hyphomicrobium sp. strain M3. The other four cloned sequences from the activated sludge sample were more closely related to those of the Hyphomicrobium cluster I organisms (95 to 97% similarity). Whole-cell fluorescence hybridization of microorganisms in the activated sludge with genus-specificHyphomicrobium probe S-G-Hypho-1241-a-A-19 enhanced the visualization of Hyphomicrobium and revealed thatHyphomicrobium appears to be abundant both on the outside of flocs and within the floc structure. Dot blot hybridization of activated sludge samples from 1995 with probes designed forHyphomicrobium cluster I and Hyphomicrobiumcluster II indicated that Hyphomicrobium cluster II-positive 16S rRNA dominated over Hyphomicrobium cluster I-positive 16S rRNA by 3- to 12-fold. Hyphomicrobium 16S rRNA comprised approximately 5% of the 16S rRNA in the activated sludge.

Effects of different coagulants on flocculation performance and floc properties in northwest China raw water treatment

2015 ◽  
Vol 15 (3) ◽  
pp. 599-605
Author(s):  
Jian Liu ◽  
Junguo He ◽  
Yixing Yuan ◽  
Jie Zhang
Keyword(s):  
Water Treatment ◽  
Low Temperature ◽  
Size Distribution ◽  
Treatment Plant ◽  
Northwest China ◽  
Quality Standard ◽  
Tibet Plateau ◽  
Floc Size ◽  
Melt Water ◽  
Floc Properties

The water of northwest China, characterized by low turbidity, low temperature, and micro-pollution, has posed difficult problems for water treatment plants. This study deployed a pilot-scale grid flocculation system to treat melt water from the Qinghai-Tibet Plateau in northwest China. A range of traditional coagulants were used on the low temperature, low turbidity, and micro-polluted melt water, to investigate the effect of coagulant types on flocculation performance and floc properties. Flocculation performance varied, depending upon the coagulant used. Turbidity and organic matter were removed with the greatest efficiency by polyaluminum chloride (PAC), followed by polyaluminum ferric chloride, followed by aluminum sulfate (alum). At a PAC dosage of 25 mg/L, the settled water's residual turbidity was lower than 1 NTU, meeting the Chinese national water-quality standard. Floc fractal dimensions of the three coagulants initially decreased, and then increased as the flocculation process yielded larger particles. This suggested that low turbidity could significantly affect the floc fractal dimension. Studying floc size distribution indicated that floc size in the grid flocculation tank was relatively uniform; the floc size distribution of PAC was the narrowest. The results could be used to inform operations of the Xining water treatment plant.

Linking floc structure and settling properties to activated sludge population dynamics in an SBR

2003 ◽  
Vol 47 (12) ◽  
pp. 9-18 ◽  
Author(s):  
R. Govoreanu ◽  
D. Seghers ◽  
I. Nopens ◽  
B. De Clercq ◽  
H. Saveyn ◽  
...  
Keyword(s):  
Microbial Community ◽  
Activated Sludge ◽  
Size Distribution ◽  
Community Dynamics ◽  
16S Rrna Genes ◽  
Volume Index ◽  
Rrna Genes ◽  
Filamentous Bacteria ◽  
Floc Size ◽  
Stable Conditions

Over a period of 227 days properties of activated sludge grown in an aequencing batch reactor (SBR) operated under stable conditions were analyzed. Settling properties (sludge volume index (SVI)) of the activated sludge were compared with on-line measurements of floc size and size distribution obtained by using a laser light scattering technique (Malvern Mastersizer/S, Malvern, UK), and with measurements of microbial community dynamics analyzed by denaturing gradient gel electrophoresis (DGGE) patterns of 16S rRNA genes. In addition, microscopical observations were used to confirm the results. Three distinct stages in the SBR evolution were observed. In the first stage the structural floc properties showed predominant presence of floc-forming bacteria in the activated sludge. A good correlation between floc size, settling properties and microbial community evolution was observed. The second stage showed a good balance between floc-forming and filamentous bacteria, with good settling properties and a highly dynamic community in the SBR. In the third stage, an increase in the filamentous bacteria, which became predominant in the system was observed. Again, a good correlation between settling properties and floc size distribution was obtained and a new dominant species was observed in the DGGE patterns, which can be assumed to be a filamentous organism.

Simultaneous determination of activated sludge floc size distribution by different techniques

2004 ◽  
Vol 50 (12) ◽  
pp. 39-46 ◽  
Author(s):  
R. Govoreanu ◽  
H. Saveyn ◽  
P. Van der Meeren ◽  
P.A. Vanrolleghem
Keyword(s):  
Image Analysis ◽  
Activated Sludge ◽  
Size Distribution ◽  
Bimodal Distribution ◽  
Pilot Scale ◽  
Automated Image Analysis ◽  
Image Analysis System ◽  
Floc Size ◽  
In Series ◽  
Log Normal

The activated sludge floc size distribution (FSD) is investigated by using different techniques and the results are compared against each other in order to gain insight into the FSD characteristics, as well as to detect the limitations of each measurement technique. The experimental set-up consisted of three devices coupled in series: a MastersizerS, an automated image analysis system (IMAN) and a CIS-100. The latter instrument has two measurement channels, based on time of transition (TOT), and image analysis (SHAPE) principles. In order to minimise the variability between successive measurements, the activated sludge samples collected from a pilot-scale SBR were flocculated until steady state was achieved. The results show that the MastersizerS and SHAPE devices yield similar volume weighted FSD. In contrast, the IMAN overestimated the floc size and TOT frequently showed a bimodal distribution. The number distributions from TOT and SHAPE were in agreement, while those generated by the MastersizerS were mainly located in the submicron range and those of IMAN corresponded to larger sizes. The experimental distributions show a good fit to the log-normal model. It is shown that the measurement principle is of utmost importance and results transformation may lead to data misinterpretation.

Cultivation, granulation and characteristics of anaerobic ammonium-oxidizing sludge in sequencing batch reactor

2006 ◽  
Vol 6 (6) ◽  
pp. 71-79 ◽  
Author(s):  
B.L. Hu ◽  
P. Zheng ◽  
Q. Mahmood ◽  
H.F. Qian ◽  
D.L. Wu
Keyword(s):  
Activated Sludge ◽  
Shock Loading ◽  
Sequencing Batch Reactor ◽  
Batch Reactor ◽  
Bacterial Species ◽  
Treatment Plant ◽  
Granular Sludge ◽  
Pilot Scale ◽  
Anaerobic Sequencing Batch Reactor ◽  
Nitrite Removal

Anaerobic sequencing batch reactor (SBR) was started-up by inoculating the nitrifying activated sludge. After an operation of 72 d, the bioreactor reached at steady state with ammonia and nitrite removal percentages higher than 95%. During operation, the sludge granulated in the reactor. The morphology and internal structure of sludge granules changed conspicuously, the density increased while the color changed from khaki to red. The average granular diameter grew from 1.2 to 3.69 mm, and its settling velocity accelerated from 107.68 to 118.49 m/h. Sludge granulation improved the tolerance to hydraulic shock loading, and reduced sludge washout (TSS < 0.028 g/L). The dominant bacterial communities (filamentous and cocci) in nitrifying activated sludge were replaced by irregular shaped ANAMMOX bacterial species gradually. An increase of ANAMMOX rate was achieved with the increasing granular diameter. SBR is a useful reactor to cultivate ANAMMOX granular sludge, while granular ANAMMOX sludge thus developed can be used as seeding sludge in a pilot-scale or full scale wastewater treatment plant.

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