A simple empirical model for the clarification-thickening process in wastewater treatment plants

2014 ◽  
Vol 71 (3) ◽  
pp. 366-372
Author(s):  
Y. K. Zhang ◽  
H. C. Wang ◽  
L. Qi ◽  
G. H. Liu ◽  
Z. J. He ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Empirical Model ◽  
Wastewater Treatment Plants ◽  
Volume Index ◽  
Compression Zone ◽  
Efficient Operation ◽  
Secondary Settling ◽  
Sludge Thickening ◽  
Simple Empirical Model

In wastewater treatment plants (WWTPs), activated sludge is thickened in secondary settling tanks and recycled into the biological reactor to maintain enough biomass for wastewater treatment. Accurately estimating the activated sludge concentration in the lower portion of the secondary clarifiers is of great importance for evaluating and controlling the sludge recycled ratio, ensuring smooth and efficient operation of the WWTP. By dividing the overall activated sludge-thickening curve into a hindered zone and a compression zone, an empirical model describing activated sludge thickening in the compression zone was obtained by empirical regression. This empirical model was developed through experiments conducted using sludge from five WWTPs, and validated by the measured data from a sixth WWTP, which fit the model well (R2 = 0.98, p < 0.001). The model requires application of only one parameter, the sludge volume index (SVI), which is readily incorporated into routine analysis. By combining this model with the conservation of mass equation, an empirical model for compression settling was also developed. Finally, the effects of denitrification and addition of a polymer were also analysed because of their effect on sludge thickening, which can be useful for WWTP operation, e.g., improving wastewater treatment or the proper use of the polymer.

The main wastewater treatment plant of Vienna: an example of cost effective wastewater treatment for large cities

2006 ◽  
Vol 54 (10) ◽  
pp. 79-86 ◽  
Author(s):  
G. Wandl ◽  
H. Kroiss ◽  
K. Svardal
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Nitrogen Removal ◽  
Nutrient Removal ◽  
Process Management ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
Single Stage ◽  
Volume Index ◽  
Two Stage

Two-stage activated sludge plants succeed in stable treatment efficiency concerning carbon removal and nitrification with far less reactor tank volume than conventional single stage systems. In case of large treatment plants this fact is of great economic relevance. Because of the very small specific volume of these two-stage treatment plants in comparison with low loaded single-stage plants, internal cycles have to be applied to ensure sufficient nitrogen removal. Due to these internal cycles two stage activated sludge plants offer many possibilities in terms of process management which results in new process optimisation procedures as compared to conventional single-stage nutrient removal treatment plants. The proposed extension concept for the Main Treatment Plant of Vienna was validated with pilot plant investigations especially with regard to nitrogen removal where it proved to comply with the legal requirements. The operation of the treatment plant can easily be adapted to changes in temperature and sludge volume index occurring in full scale practice. Sludge retention time and aerobic volume in the second stage are controlled in order to secure sufficient nitrification capacity and to optimise nitrogen removal by means of the variation of the loading conditions for the two stages. The investigations confirmed that the specific two-stage activated sludge concept applied in Vienna is an economically advantageous alternative for large wastewater treatment plants with stringent requirements for nitrification and nutrient removal.

scholarly journals Influence of road salt thawing peaks on the inflow composition and activated sludge properties in municipal wastewater treatment

2021 ◽  
Author(s):  
J. Tauber ◽  
B. Flesch ◽  
V. Parravicini ◽  
K. Svardal ◽  
J. Krampe
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Wastewater Treatment Plants ◽  
Road Salt ◽  
Volume Index ◽  
Municipal Wastewater Treatment ◽  
Floc Size ◽  
Floc Structure ◽  
Autotrophic Biomass

Abstract Operational data over 2 years from three large Austrian wastewater treatment plants (WWTPs) with design capacities of 4 million, 950,000 and 110,000 population equivalent (PE) were examined. Salt peaks, due to thawing road salt were detected and quantified by electrical conductivity, temperature and chloride measurement in the inflow of the WWTPs. Daily NaCl inflow loads up to 1,147 t/d and PE-specific loads of 0.26–0.5 kg NaCl/(PE · y) were found. To mimic the plants' behaviour in a controlled environment, NaCl was dosed into the inflow of a laboratory-scale activated sludge plant. The influence of salt peaks on important activated sludge parameters such as sludge volume index, settling velocity and floc size were investigated. Influent and effluent were sampled extensively to calculate removal rates. Respiration measurements were performed to quantify activated sludge activity. Particle size distributions of the activated sludge floc sizes were measured using laser diffraction particle sizing and showed a decrease of the floc size by approximately two-thirds. The floc structure was examined and documented using light microscopy. At salt concentrations below 1 g/L, increased respiration was found for autotrophic biomass, and between 1 and 3 g NaCl/L respiration was inhibited by up to 30%.

Contact Zone: French Practice with Low F/M Bulking Control

1994 ◽  
Vol 29 (7) ◽  
pp. 221-228 ◽  
Author(s):  
R. Pujol ◽  
J. P. Canler
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Contact Zone ◽  
Wastewater Treatment Plants ◽  
Volume Index ◽  
Treatment Facility ◽  
Sludge Volume Index ◽  
Simple Rules ◽  
Rational Operation ◽  
Effective Use

A study of twelve wastewater treatment plants in France confirms the effectiveness of the contact zone technique in controlling sludge bulking (with a reduction in the Sludge Volume Index in 91% of cases) and foaming (improvement of the situation in 75% of the cases). The study focused on low-F/M activated sludge units in which organisms such as Microthrix p. or type 0041 (characteristic of these plants) were identified. Contact zones do not entail any major limitations, a fact which advocates their use in this type of treatment facility. Rational operation of the plant (in terms of aeration and sludge production) and compliance with a few simple rules will ensure effective use of this technology.

A simple empirical model for activated sludge thickening in secondary clarifiers

2002 ◽  
Vol 36 (13) ◽  
pp. 3245-3252 ◽  
Author(s):  
D.L Giokas ◽  
Youngchul Kim ◽  
P.A Paraskevas ◽  
E.K Paleologos ◽  
T.D Lekkas
Keyword(s):  
Activated Sludge ◽  
Empirical Model ◽  
Sludge Thickening ◽  
Simple Empirical Model

Factors affecting population of filamentous bacteria in wastewater treatment plants with nutrients removal

2015 ◽  
Vol 73 (4) ◽  
pp. 790-797 ◽  
Author(s):  
Aleksandra Miłobędzka ◽  
Anna Witeska ◽  
Adam Muszyński
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Wastewater Treatment Plants ◽  
Population Analysis ◽  
Principal Component ◽  
Volume Index ◽  
Filamentous Bacteria ◽  
Municipal Wastewater Treatment ◽  
Operational Parameters

Filamentous population in activated sludge and key operational parameters of full-scale municipal wastewater treatment plants (WWTPs) with bulking problems representative for Poland were investigated with quantitative fluorescence in situ hybridization. Statistical analyses revealed few relationships between operational parameters and biovolume of filamentous bacteria. Sludge age was not only positively correlated with abundance of Chloroflexi (parametric correlation and principal component analysis (PCA)), but also differentiated Microthrix population (analysis of variance (ANOVA)). Phylum Chloroflexi and pH presented a negative relation during the study (PCA). ANOVA showed that pH of influent and sludge volume index (SVI) differentiated abundance of types 0803 and 1851 of Chloroflexi and candidate division TM7. SVI increased along with higher abundance of Microthrix (positive parametric and non-parametric correlations and positive relation in PCA). Biovolumes of morphotypes 0803 and 1851 of Chloroflexi were differentiated by organic matter in influent, also by nutrients in the case of Chloroflexi type 1851. Chemical and biological oxygen demands (COD and BOD5, respectively) were negatively correlated with Microthrix. COD also differentiated the abundance of Haliscomenobacter hydrossis. Results of the study can be used to prevent WWTPs from excessive proliferation of filamentous bacteria and operational problems caused by them – bulking and foaming of activated sludge.

scholarly journals Intensification of activated sludge sedimentation processes by means of vacuuming

Vestnik MGSU ◽  
2021 ◽  
pp. 370-380
Author(s):  
Artem A. Kulakov ◽  
Alina F. Filatova
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Wastewater Treatment Plants ◽  
Settling Tank ◽  
Municipal Wastewater Treatment ◽  
Treated Water ◽  
Mixed Liquor ◽  
Municipal Wastewater Treatment Plants ◽  
Secondary Settling

Introduction. The mixed liquor of nitrogen removal wastewater treatment plants is characterized by a high concentration of nitrates and dissolved oxygen at the inlet to the secondary settling tank. In the sludge layer of secondary sedimentation tanks, conditions of decreased oxygen content and uncontrolled denitrification processes take place. This leads to the floating up and removal of sludge with the effluent and secondary pollution of treated water. The purpose of this article is to study the parameters of activated sludge sedimentation in municipal wastewater treatment plants and their intensification by means of vacuuming. Materials and methods. The studies were carried out under laboratory conditions. Activated sludge vacuuming and sedimentation processes were simulated. Diagrams of the “sludge-water” phase reduction (Kinsh curves) were drawn. Mathematical and graphic processing of the results was carried out. Results. Biological treatment of municipal wastewater (aerotank — secondary settling tank) and methods of its intensification by influencing the activated sludge were considered in this article. Trends of activated sludge (at different concentrations of mixed liquor suspended solids) sedimentation were experimentally obtained for municipal wastewater treatment plants. The process of sludge vacuuming was researched, the process efficiency was determined as a function of the treatment time. Conclusions. Vacuuming allows removing gases from the fluid, which accelerates the process of sludge separation from the treated water and prevents it from floating to the surface. The treated sample is characterized by better sedimentation characteristics, density, coarseness and integrity of flakes. The optimal duration of mixed liquor vacuuming before sedimentation is 0.5 minutes; this accelerates the processes of subsequent sedimentation and reduces the removal of sludge with treated water. The results of laboratory tests can be applied to the design of the mixed liquor vacuuming unit before the secondary sedimentation tanks and its sludge separation.

scholarly journals Oxygen Transfer in Two-Stage Activated Sludge Wastewater Treatment Plants

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1964
Author(s):  
Maximilian Schwarz ◽  
Justus Behnisch ◽  
Jana Trippel ◽  
Markus Engelhart ◽  
Martin Wagner
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Oxygen Transfer ◽  
Pressure Loss ◽  
Wastewater Treatment Plants ◽  
High Rate ◽  
Ex Situ ◽  
Stormwater Treatment ◽  
Two Stage ◽  
Efficient Operation

Aeration is an energy-intensive process of aerobic biological treatment in wastewater treatment plants (WWTP). Two-stage processes enable energy-efficient operation, but oxygen transfer has not been studied in depth before. In this study, α-factors were determined with long-term ex situ steady-state off-gas measurements in pilot-scale test reactors (5.8 m height, 8.3 m3) coupled to full-scale activated sludge basins. A two-stage WWTP with more than 1 Mio population equivalent was studied over 13 months including rain and dry weather conditions. Operating data, surfactant concentrations throughout the two-stage process, and the effect of reverse flexing on pressure loss of diffusers were examined. The values of αmean, αmin, and αmax for design load cases of aeration systems were determined as 0.45, 0.33, and 0.54 in the first high-rate carbon removal stage and as 0.80, 0.69, and 0.91 in the second nitrification stage, respectively. The first stage is characterized by a distinct diurnal variation and decrease in α-factor during stormwater treatment. Surfactants and the majority of the total organic carbon (TOC) load are effectively removed in the first stage; hence, α-factors in the second stage are higher and have a more consistent diurnal pattern. Proposed α-factors enable more accurate aeration system design of two-stage WWTPs. Fouling-induced diffuser pressure loss can be restored effectively with reverse flexing in both treatment stages.

scholarly journals The capacity of wastewater treatment plants drives bacterial community structure and its assembly

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Young Kyung Kim ◽  
Keunje Yoo ◽  
Min Sung Kim ◽  
Il Han ◽  
Minjoo Lee ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Community Structure ◽  
Bacterial Community ◽  
Activated Sludge ◽  
Community Assembly ◽  
Bacterial Communities ◽  
Wastewater Treatment Plants ◽  
High Capacity ◽  
Operating Conditions ◽  
Rrna Gene

Abstract Bacterial communities in wastewater treatment plants (WWTPs) affect plant functionality through their role in the removal of pollutants from wastewater. Bacterial communities vary extensively based on plant operating conditions and influent characteristics. The capacity of WWTPs can also affect the bacterial community via variations in the organic or nutrient composition of the influent. Despite the importance considering capacity, the characteristics that control bacterial community assembly are largely unknown. In this study, we discovered that bacterial communities in WWTPs in Korea and Vietnam, which differ remarkably in capacity, exhibit unique structures and interactions that are governed mainly by the capacity of WWTPs. Bacterial communities were analysed using 16S rRNA gene sequencing and exhibited clear differences between the two regions, with these differences being most pronounced in activated sludge. We found that capacity contributed the most to bacterial interactions and community structure, whereas other factors had less impact. Co-occurrence network analysis showed that microorganisms from high-capacity WWTPs are more interrelated than those from low-capacity WWTPs, which corresponds to the tighter clustering of bacterial communities in Korea. These results will contribute to the understanding of bacterial community assembly in activated sludge processing.

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