Challenges encountered when expanding activated sludge models: a case study based on N2O production

2014 ◽  
Vol 70 (7) ◽  
pp. 1251-1260 ◽  
Author(s):  
L. J. P. Snip ◽  
R. Boiocchi ◽  
X. Flores-Alsina ◽  
U. Jeppsson ◽  
K. V. Gernaey
Keyword(s):  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
N2o Emission ◽  
Full Scale ◽  
Ammonia Oxidizing Bacteria ◽  
N2o Formation ◽  
N2o Production ◽  
Parameter Values ◽  
Activated Sludge Models

It is common practice in wastewater engineering to extend standard activated sludge models (ASMs) with extra process equations derived from batch experiments. However, such experiments have often been performed under conditions different from the ones normally found in wastewater treatment plants (WWTPs). As a consequence, these experiments might not be representative for full-scale performance, and unexpected behaviour may be observed when simulating WWTP models using the derived process equations. In this paper we want to highlight problems encountered using a simplified case study: a modified version of the Activated Sludge Model No. 1 (ASM1) is upgraded with nitrous oxide (N2O) formation by ammonia-oxidizing bacteria. Four different model structures have been implemented in the Benchmark Simulation Model No. 1 (BSM1). The results of the investigations revealed two typical difficulties: problems related to the overall mathematical model structure and problems related to the published set of parameter values. The paper describes the model implementation incompatibilities, the variability in parameter values and the difficulties of reaching similar conditions when simulating a full-scale activated sludge plant. Finally, the simulation results show large differences in oxygen uptake rates, nitritation rates and consequently the quantity of N2O emission (GN2O) using the different models.

Molecular assessment of ammonia- and nitrite-oxidizing bacteria in full-scale activated sludge wastewater treatment plants

2003 ◽  
Vol 48 (8) ◽  
pp. 119-126 ◽  
Author(s):  
K.G. Robinson ◽  
H.M. Dionisi ◽  
G. Harms ◽  
A.C. Layton ◽  
I.R. Gregory ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
16S Rdna ◽  
Municipal Wastewater ◽  
Wastewater Treatment Plants ◽  
Amoa Gene ◽  
Full Scale ◽  
Ammonia Oxidizing Bacteria ◽  
Copy Numbers ◽  
Nitrite Oxidizing Bacteria

Nitrification was assessed in two full-scale wastewater treatment plants (WWTPs) over time using molecular methods. Both WWTPs employed a complete-mix suspended growth, aerobic activated sludge process (with biomass recycle) for combined carbon and nitrogen treatment. However, one facility treated primarily municipal wastewater while the other only industrial wastewater. Real time PCR assays were developed to determine copy numbers for total 16S rDNA (a measure of biomass content), the amoA gene (a measure of ammonia-oxidizers), and the Nitrospira 16S rDNA gene (a measure of nitrite-oxidizers) in mixed liquor samples. In both the municipal and industrial WWTP samples, total 16S rDNA values were approximately 2-9 × 1013 copies/L and Nitrospira 16S rDNA values were 2-4 × 1010 copies/L. amoA gene concentrations averaged 1.73 × 109 copies/L (municipal) and 1.06 × 1010 copies/L (industrial), however, assays for two distinct ammonia oxidizing bacteria were required.

Controlling the Settling of Activated Sludge in Pulp and Paper Wastewater Treatment Plants

1999 ◽  
Vol 40 (11-12) ◽  
pp. 223-229 ◽  
Author(s):  
Frédéric Clauss ◽  
Christel Balavoine ◽  
Delphine Hélaine ◽  
Gaëtan Martin
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Pulp And Paper ◽  
Organic Load ◽  
Forest Industry ◽  
Filamentous Bulking ◽  
Mineral Particles ◽  
Mineral Powder

Forest industry wastewaters are difficult to clean: hydraulic and organic load variations, filamentous bulking or pin-point flocs negatively impact depollution processes. The addition of a fine, mineral, talc-based powder, Aquatal, into the aeration tanks of wastewater treatment plants connected to pulp and paper factories has been successfully tested since end of '97. The first case-study presents full results obtained over a period of 18 months in a 20,000 p.e. plant connected to a paper factory. The mineral powder was regularly added to control sludge volume index, thereby ensuring low suspended solids concentration in the outfluent. Plant operators could easily adapt biomass concentration to match organic load variation, thereby maintaining pollution micro-organisms ratio constant. In a second case study, a trouble-shooting strategy was implemented to counteract filamentous bulking. A one-off, large dosage enabled the plant operator to deal effectively with poor settleability sludge and rapidly control sludge blanket expansion. In both cases, the main common characteristics observed were an increase in floc aggregation and the production of heavier and well-structured flocs. The sludge settling velocity increased and an efficient solid/liquid separation was obtained. After a few days, the mineral particles of Aquatal were progressively integrated into the sludge floc structure. When the mineral powder was added to the activated sludge in the aeration basin, chemical interactions frequently encountered with other wastewater treatment additives did not pose a problem. Moreover, with this mineral additive, the biological excess sludge displayed good thickening properties and dewatering was improved. Despite the addition of the insoluble mineral particles, the amount of wet sludge expelled did not increase. Aquatal offers a rapid solution to floc settleability problems which so frequently arise when physical or biological disorders appear in forest industry wastewater treatment plants.

An investigation into studying of the activated sludge foaming potential by using physicochemical parameters

2002 ◽  
Vol 46 (1-2) ◽  
pp. 525-528 ◽  
Author(s):  
K. Hladikova ◽  
I. Ruzickova ◽  
P. Klucova ◽  
J. Wanner
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Physicochemical Parameters ◽  
Wastewater Treatment Plants ◽  
Physicochemical Characteristics ◽  
Full Scale ◽  
Aeration Tank ◽  
Foam Formation ◽  
Individual Parameter

This paper examines how the physicochemical characteristics of the solids are related to foam formation and describes how the foaming potential of full-scale plants can be assessed. The relations among activated sludge and biological foam hydrophobicity, scum index, aeration tank cover and filamentous population are evaluated. Individual parameter comparison reveals the scumming intensity can be estimated only on the assumption that foams is already established. None of the above mentioned characteristics can be reliably used to predict the foaming episodes at wastewater treatment plants.

scholarly journals The Microbial Database for Danish wastewater treatment plants with nutrient removal (MiDas-DK) – a tool for understanding activated sludge population dynamics and community stability

2013 ◽  
Vol 67 (11) ◽  
pp. 2519-2526 ◽  
Author(s):  
A. T. Mielczarek ◽  
A. M. Saunders ◽  
P. Larsen ◽  
M. Albertsen ◽  
M. Stevenson ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Nutrient Removal ◽  
Wastewater Treatment Plants ◽  
Amplicon Sequencing ◽  
Temporal Variations ◽  
Full Scale ◽  
16S Rrna Amplicon Sequencing ◽  
Specific Factors ◽  
Operational Data

Since 2006 more than 50 Danish full-scale wastewater treatment plants with nutrient removal have been investigated in a project called ‘The Microbial Database for Danish Activated Sludge Wastewater Treatment Plants with Nutrient Removal (MiDas-DK)’. Comprehensive sets of samples have been collected, analyzed and associated with extensive operational data from the plants. The community composition was analyzed by quantitative fluorescence in situ hybridization (FISH) supported by 16S rRNA amplicon sequencing and deep metagenomics. MiDas-DK has been a powerful tool to study the complex activated sludge ecosystems, and, besides many scientific articles on fundamental issues on mixed communities encompassing nitrifiers, denitrifiers, bacteria involved in P-removal, hydrolysis, fermentation, and foaming, the project has provided results that can be used to optimize the operation of full-scale plants and carry out trouble-shooting. A core microbial community has been defined comprising the majority of microorganisms present in the plants. Time series have been established, providing an overview of temporal variations in the different plants. Interestingly, although most microorganisms were present in all plants, there seemed to be plant-specific factors that controlled the population composition thereby keeping it unique in each plant over time. Statistical analyses of FISH and operational data revealed some correlations, but less than expected. MiDas-DK (www.midasdk.dk) will continue over the next years and we hope the approach can inspire others to make similar projects in other parts of the world to get a more comprehensive understanding of microbial communities in wastewater engineering.

Practical experience with full-scale structured sheet media (SSM) integrated fixed-film activated sludge (IFAS) systems for nitrification

2014 ◽  
Vol 71 (4) ◽  
pp. 545-552 ◽  
Author(s):  
Hua Li ◽  
Jia Zhu ◽  
James J Flamming ◽  
Jack O'Connell ◽  
Michael Shrader
Keyword(s):  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Contact Process ◽  
Plug Flow ◽  
Oxygen Demand ◽  
Cost Effective ◽  
Practical Experience ◽  
Full Scale ◽  
Fixed Film ◽  
The Usa

Many wastewater treatment plants in the USA, which were originally designed as secondary treatment systems with no or partial nitrification requirements, are facing increased flows, loads, and more stringent ammonia discharge limits. Plant expansion is often not cost-effective due to either high construction costs or lack of land. Under these circumstances, integrated fixed-film activated sludge (IFAS) systems using both suspended growth and biofilms that grow attached to a fixed plastic structured sheet media are found to be a viable solution for solving the challenges. Multiple plants have been retrofitted with such IFAS systems in the past few years. The system has proven to be efficient and reliable in achieving not only consistent nitrification, but also enhanced bio-chemical oxygen demand removal and sludge settling characteristics. This paper presents long-term practical experiences with the IFAS system design, operation and maintenance, and performance for three full-scale plants with distinct processes; that is, a trickling filter/solids contact process, a conventional plug flow activated sludge process and an extended aeration process.

scholarly journals Activated Sludge Systems as Diferential Equations: A Fresh View on the Classical Models for Wastewater Treatment Plants

2014 ◽  
Vol 6 (2) ◽  
pp. 49-53
Author(s):  
Horea Olosutean ◽  
Letiţia Oprean
Keyword(s):  
Wastewater Treatment ◽  
Differential Equations ◽  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Early Stage ◽  
Theory And Practice ◽  
Supplementary Data ◽  
Classical Models ◽  
Activated Sludge Models ◽  
Activated Sludge Systems

Abstract Present in the theory and practice of wastewater treatment for over 50 years in consistent numbers, activated sludge models are widely used by plant operators. The early stage models, based on differential equations were synthetized and reinterpreted, presenting new insides that can help to a better understanding of the processes involved in the wastewater treatment. A consistent symbology is presented, for a much homogenous perspective, and the obvious similarities between several equations from the models are pointed out. The incomplete information from the models is emphasized, showing their amount of providing supplementary data for plant operators and researchers in the field, as well as the causes leading to their drawbacks and the effects derived from these drawbacks.

scholarly journals Quantification of biologically and chemically bound phosphorus in activated sludge from full-scale plants with biological P-removal

2021 ◽  
Author(s):  
Francesca Petriglieri ◽  
Jette F. Petersen ◽  
Miriam Peces ◽  
Marta Nierychlo ◽  
Kamilla Hansen ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Mass Balance ◽  
Wastewater Treatment Plants ◽  
Raman Microspectroscopy ◽  
Full Scale ◽  
P Fractions ◽  
P Content ◽  
Total P ◽  
P Removal

AbstractLarge amounts of phosphorus (P) are present in activated sludge from municipal wastewater treatment plants, where it exists in the form of metal salt precipitates or biologically bound into the biomass as nucleic acids, cell membrane components, and the extracellular polymeric substances or, in special polyphosphate-accumulating organisms (PAOs), as intracellular polyphosphate. Only recently, methods that reliably allow an absolute quantification of the different P-fractions, such as sequential extraction, Raman microspectroscopy, solid-state 31P magic angle spinning (MAS) NMR, and solution state 31P NMR have been developed. This study combines these techniques to obtain a comprehensive P mass-balance of activated sludge from four wastewater treatment plants with enhanced biological phosphate removal (EBPR). The total content of P and various cations was measured by chemical analysis (ICP-OES), and different P fractions were extracted for chemical characterization. Chemically bound P constituted 38-69% of total P, most likely in the form of Fe, Mg, or Al minerals, while organically bound P constituted 7-9%. By using Raman microspectroscopy and solution state 31P NMR and 31P MAS NMR spectroscopy before and after anaerobic P-release experiments, poly-P was quantified and constituted 22-54% of total P in the activated sludges and was found in approx. 25% of all bacterial cells. Moreover, Raman microspectroscopy in combination with fluorescence in situ hybridization (FISH) was used to quantify the species-specific intracellular poly-P of known PAO genera (Tetrasphaera, Ca. Accumulibacter, Dechloromonas) and other microorganisms known to possess high level of poly-P, such as the filamentous Ca. Microthrix. They were all abundant, as measured by quantitative-FISH and amplicon sequencing, and accumulated large amount of poly-P, depending on their cell-size, contributing substantially to the P-removal. Interestingly, in all four EBPR plants investigated, only 1-13% of total poly-P was stored by unidentified PAO, highlighting that most PAOs in the full-scale EBPR plants investigated are now known.HighlightsExhaustive P mass-balance of main organic and inorganic P-species in four EBPR plantsQuantification of poly-P of FISH-defined PAO and other species with high P contentTotal P content was 36-50 mgP/gSS of which 31-62% was in biomass and as poly-PA high fraction of all cells (25-30%) contained a high content of poly-PKnown PAOs contained almost all poly-P in the EBPR plants investigated

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