Modeling of organic substrate transformation in the high-rate activated sludge process

2015 ◽  
Vol 71 (7) ◽  
pp. 971-979 ◽  
Author(s):  
Thomas Nogaj ◽  
Andrew Randall ◽  
Jose Jimenez ◽  
Imre Takacs ◽  
Charles Bott ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Extracellular Polymeric Substances ◽  
Oxygen Demand ◽  
Organic Substrate ◽  
High Rate ◽  
State Variables ◽  
Modified Model ◽  
Soluble Substrate ◽  
Substrate Model ◽  
Dual Substrate

This study describes the development of a modified activated sludge model No.1 framework to describe the organic substrate transformation in the high-rate activated sludge (HRAS) process. New process mechanisms for dual soluble substrate utilization, production of extracellular polymeric substances (EPS), absorption of soluble substrate (storage), and adsorption of colloidal substrate were included in the modified model. Data from two HRAS pilot plants were investigated to calibrate and to validate the proposed model for HRAS systems. A subdivision of readily biodegradable soluble substrate into a slow and fast fraction were included to allow accurate description of effluent soluble chemical oxygen demand (COD) in HRAS versus longer solids retention time (SRT) systems. The modified model incorporates production of EPS and storage polymers as part of the aerobic growth transformation process on the soluble substrate and transformation processes for flocculation of colloidal COD to particulate COD. The adsorbed organics are then converted through hydrolysis to the slowly biodegradable soluble fraction. Two soluble substrate models were evaluated during this study, i.e., the dual substrate and the diauxic models. Both models used two state variables for biodegradable soluble substrate (SBf and SBs) and a single biomass population. The A-stage pilot typically removed 63% of the soluble substrate (SB) at an SRT <0.13 d and 79% at SRT of 0.23 d. In comparison, the dual substrate model predicted 58% removal at the lower SRT and 78% at the higher SRT, with the diauxic model predicting 32% and 70% removals, respectively. Overall, the dual substrate model provided better results than the diauxic model and therefore it was adopted during this study. The dual substrate model successfully described the higher effluent soluble COD observed in the HRAS systems due to the partial removal of SBs, which is almost completely removed in higher SRT systems.

scholarly journals Colloids, flocculation and carbon capture – a comprehensive plant-wide model

2018 ◽  
Vol 79 (1) ◽  
pp. 15-25 ◽  
Author(s):  
Hélène Hauduc ◽  
Ahmed Al-Omari ◽  
Bernhard Wett ◽  
Jose Jimenez ◽  
Haydee De Clippeleir ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Carbon Capture ◽  
Oxygen Demand ◽  
High Rate ◽  
Reactor Performance ◽  
Whole Plant ◽  
Solids Retention ◽  
Methane Potential ◽  
Intracellular Storage ◽  
Activated Sludge Systems

Abstract The implementation of carbon capture technologies such as high-rate activated sludge (HRAS) systems are gaining interests in water resource and recovery facilities (WRRFs) to minimize carbon oxidation and maximize organic carbon recovery and methane potential through biosorption of biodegradable organics into the biomass. Existing activated sludge models were developed to describe chemical oxygen demand (COD) removal in activated sludge systems operating at long solids retention times (SRT) (i.e. 3 days or longer) and fail to simulate the biological reactions at low SRT systems. A new model is developed to describe colloidal material removal and extracellular polymeric substance (EPS) generation, flocculation, and intracellular storage with the objective of extending the range of whole plant models to very short SRT systems. In this study, the model is tested against A-stage (adsorption) pilot reactor performance data and proved to match the COD and colloids removal at low SRT. The model was also tested on longer SRT systems where effluents do not contain much residual colloids, and digestion where colloids from decay processes are present.

scholarly journals Alkaline solubilisation of waste activated sludge (WAS) for soluble organic substrate – (SCOD) production / Tworzenie się rozpuszczalnego substratu organicznego podczas zasadowego rozpuszczania osadów ściekowych

2015 ◽  
Vol 41 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Jan Suschka ◽  
Eligiusz Kowalski ◽  
Jerzy Mazierski ◽  
Klaudiusz Grübel
Keyword(s):  
Fatty Acids ◽  
Activated Sludge ◽  
Volatile Fatty Acids ◽  
Construction Material ◽  
Oxygen Demand ◽  
Organic Substrate ◽  
Waste Activated Sludge ◽  
Condition Effect ◽  
Hydrolysis Process ◽  
Soluble Chemical Oxygen Demand

Abstract Improving the effects of hydrolysis on waste activated sludge (WAS) prior to anaerobic digestion is of primary importance. Several technologies have been developed and partially implemented in practice. In this paper, perhaps the simplest of these methods, alkaline solubilization, has been investigated and the results of hydrolysis are presented. An increase to only pH 8 can distinctively increase the soluble chemical oxygen demand (SCOD), and produce an anaerobic condition effect favorable to volatile fatty acids (VFA) production. Further increases of pH, up to pH 10, leads to further improvements in hydrolysis effects. It is suggested that an increase to pH 9 is sufficient and feasible for technical operations, given the use of moderate anti-corrosive construction material. This recommendation is also made having taken in consideration the option of using hydrodynamic disintegration after the initial WAS hydrolysis process. This paper presents the effects of following alkaline solubilization with hydrodynamic disintegration on SCOD

scholarly journals Extracellular polymeric substance production in high rate algal oxidation ponds

2017 ◽  
Vol 76 (10) ◽  
pp. 2647-2654 ◽  
Author(s):  
Taobat A. Jimoh ◽  
A. Keith Cowan
Keyword(s):  
Biochemical Analysis ◽  
Suspended Solids ◽  
Extracellular Polymeric Substances ◽  
Sewage Treatment ◽  
Oxygen Demand ◽  
High Rate ◽  
Heterotrophic Metabolism ◽  
Partial Characterisation ◽  
Ft Ir ◽  
Oxidation Ponds

Abstract Integrated algal pond systems (IAPSs) combine anaerobic and aerobic bioprocesses to affect sewage treatment. The present work describes the isolation and partial characterisation of soluble extracellular polymeric substances (EPSs) associated with microalgal bacterial flocs (MaB-flocs) generated in high rate algal oxidation ponds (HRAOPs) of an IAPS treating domestic sewage. Productivity and change in MaB-flocs concentration, measured as mixed liquor suspended solids (MLSS) between morning (MLSSAM) and evening (MLSSPM) were monitored and the substructure of the MaB-flocs matrix examined by biochemical analysis and Fourier transform infrared spectroscopy (FT-IR). Results show that MaB-flocs from HRAOPs are assemblages of microorganisms produced as discrete aggregates as a result of microbial EPS production. Formation and accumulation of the EPS was stimulated by light. Analysis by FT-IR revealed characteristic carbohydrate enrichment of these polymeric substances. In contrast, FT-IR spectra of EPSs from dark-incubated MaB-flocs confirmed that these polymers contained increased aliphatic and aromatic functionalities relative to carbohydrates. These differences, it was concluded, were due to dark-induced transition from phototrophic to heterotrophic metabolism. The results negate microalgal cell death as a contributor to elevated chemical oxygen demand of IAPS treated water.

The role of extracellular polymeric substances on carbon capture in a high rate activated sludge A-stage system

2017 ◽  
Vol 322 ◽  
pp. 428-434 ◽  
Author(s):  
Maureen N. Kinyua ◽  
Matthew Elliott ◽  
Bernhard Wett ◽  
Sudhir Murthy ◽  
Kartik Chandran ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Carbon Capture ◽  
Extracellular Polymeric Substances ◽  
High Rate ◽  
Stage System

Strong selection pressures impact the capacity of flocculating activated sludge bacteria to granulate

2013 ◽  
Vol 67 (8) ◽  
pp. 1678-1687 ◽  
Author(s):  
G. A. C. Ehlers ◽  
S. J. Turner
Keyword(s):  
Particle Size ◽  
Activated Sludge ◽  
Extracellular Polymeric Substances ◽  
High Rate ◽  
Volume Index ◽  
Size Analysis ◽  
Liquid Separation ◽  
Granule Formation ◽  
Selection Pressures ◽  
The Impact

The capacity of activated sludge (AS) microbial populations to form dense granules offers the potential to establish efficiently settleable biomass. This has the potential to circumvent problems around ineffective solids–liquid separation and sensitivity to variable chemical oxygen demand (COD) loads. Although a number of studies have evaluated aerobic laboratory granulation reactors as high-rate treatment systems, the biological processes involved in aerobic granulation are not fully understood. Concomitantly, the impact of operation parameters such as organic loading rates is also important for granulation. The ability of a flocculating AS community to granulate under different selection pressures was evaluated in a laboratory sequencing batch reactor by determining levels of extracellular polymeric substances (EPS) and particle size fractions that developed under feast (4.74 g COD L−1) and famine (0.42 g COD L−1) nutrient regimes. The efficiency of solid–liquid separation was also measured. Aggregation indices showed levels >94% and a sludge volume index factor of up to 0.94, which strongly suggested granule formation; however, microscopy evaluation showed a mixture of flocs and granules. Particle size analysis revealed binomial distribution patterns of particles in the reactor which shifted to smaller tightly bound particles (<200 μm) although large particles (>600 μm) were also measured during famine conditions. This coincided with increases in EPS levels although EPS quantities were low and it is postulated that this could have impacted granule formation: the EPS in the bacterial aggregates were consumed since the AS community was starved.

Life cycle assessment comparison of activated sludge, trickling filter, and high-rate anaerobic-aerobic digestion (HRAAD)

2016 ◽  
Vol 73 (10) ◽  
pp. 2353-2360 ◽  
Author(s):  
Leonardo Postacchini ◽  
Krishna M. Lamichhane ◽  
Dennis Furukawa ◽  
Roger W. Babcock ◽  
F. E. Ciarapica ◽  
...  
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Activated Sludge ◽  
Environmental Impacts ◽  
Municipal Wastewater ◽  
Oxygen Demand ◽  
High Rate ◽  
Trickling Filter ◽  
Life Cycle Assessment Methodology ◽  
Aerobic Digestion

This paper conducts a comparative assessment of the environmental impacts of three methods of treating primary clarifier effluent in wastewater treatment plants (WWTPs) through life cycle assessment methodology. The three technologies, activated sludge (AS), high rate anaerobic-aerobic digestion (HRAAD), and trickling filter (TF), were assessed for treatment of wastewater possessing average values of biochemical oxygen demand and total suspended solids of 90 mg L−1 and 70 mg L−1, respectively. The operational requirements to process the municipal wastewater to effluent that meets USEPA regulations have been calculated. The data for the AS system were collected from the East Honolulu WWTP (Hawaii, USA) while data for the HRAAD system were collected from a demonstration-scale system at the same plant. The data for the TF system were estimated from published literature. Two different assessment methods have been used in this study: IMPACT 2002+ and TRACI 2. The results show that TF had the smallest environmental impacts and that AS had the largest, while HRAAD was in between the two but with much reduced impacts compared with AS. Additionally, the study shows that lower sludge production is the greatest advantage of HRAAD for reducing environmental impacts compared with AS.

Continuous treatment of flotation collector wastewater using a membrane bioreactor

2016 ◽  
Vol 73 (8) ◽  
pp. 1901-1909 ◽  
Author(s):  
Weixiong Lin ◽  
Yongkang Dai ◽  
Chun Wu ◽  
Pingting Xu ◽  
Jie Ren ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Extracellular Polymeric Substances ◽  
Tricarboxylic Acid Cycle ◽  
Reduction Rate ◽  
Oxygen Demand ◽  
Continuous Treatment ◽  
Treatment Technology ◽  
Time Period ◽  
Simulated Wastewater ◽  
The Impact

Aniline aerofloat (DDA) is a widely used material in China and has become a main pollutant in floatation wastewater. In this study, a membrane reactor (MBR) was constructed to continuously treat simulated wastewater contaminated with DDA. The study investigated the hydraulic retention time (HRT) and the impact of influent DDA concentration on MBR performance, and analyzed intermediates from the DDA biodegradation pathway and activated sludge transfer pathway. The results showed that a 3 h HRT was an efficient and economical time period for MBR to remove 95 ± 5 mg/L DDA from the simulated wastewater; the chemical oxygen demand reduction rate was 89.9%. DDA concentration negatively impacted MBR performance. MBR performance fluctuated slightly when HRT was 3 h, dissolved oxygen ranged from 4.8 to 5.3 mg/L, pH was between 6.5 and 7.0, and DDA concentrations were at 95 ± 5 mg/L DDA. The transfer pathway in the activated sludge of DDA was through soluble microbial products, loosely bound extracellular polymeric substances, tightly bound extracellular polymeric substances, and finally cell biodegradation. DDA initially degraded to aniline; the aniline was further biodegraded to other organic compounds and was finally mineralized through the tricarboxylic acid cycle. This study offers a new continuous biological treatment technology to address DDA.

scholarly journals Effect of different hydrolytic enzymes pretreatment for improving the hydrolysis and biodegradability of waste activated sludge

2018 ◽  
Vol 2017 (2) ◽  
pp. 592-602 ◽  
Author(s):  
Jiahao Chen ◽  
Shihu Liu ◽  
Yingmu Wang ◽  
Wei Huang ◽  
Jian Zhou
Keyword(s):  
Activated Sludge ◽  
Regional Integration ◽  
Extracellular Polymeric Substances ◽  
Hydrolytic Enzyme ◽  
Hydrolytic Enzymes ◽  
Oxygen Demand ◽  
Waste Activated Sludge ◽  
Sludge Hydrolysis ◽  
Main Component ◽  
Fluorescence Regional Integration

Abstract In this study, the effects of lysozyme, protease and α-amylase pretreatments for improving the hydrolysis and biodegradability of waste activated sludge (WAS) were investigated. The results showed that lysozyme was more effective in increasing the soluble chemical oxygen demand (SCOD) concentration in the liquid phase of sludge and improving the release of protein and carbohydrate from sludge flocculation to enhance sludge hydrolysis. After 8 h hydrolysis, the net SCOD increase in a reactor with lysozyme was 2.23 times and 2.15 times that of the reactors with protease and α-amylase, respectively. Meanwhile, lysozyme and protease could improve the lysis of microorganism cells and the dissolution of extracellular polymeric substances (EPS) to a certain extent, and lysozyme was more effective. Furthermore, the compositional characteristics of dissolved organic matter (DOM) and EPS were analyzed by EEM fluorescence spectroscopy and fluorescence regional integration (FRI) analysis. Tryptophan-like protein was the main component of sludge, which accounted for 31% and 38% of DOM and EPS, respectively. Lysozyme could decrease the percentage of non-biodegradable materials in sludge, such as humic acid-like substances and fulvic acid-like substances, so it could improve the biodegradability of sludge. This study can provide valuable information for future studies about hydrolytic enzyme pretreatments for WAS disposal.

scholarly journals The Influence of COD Fraction Forms and Molecules Size on Hydrolysis Process Developed by Comparative OUR Studies in Activated Sludge Modelling

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 929 ◽  
Author(s):  
Jakub Drewnowski ◽  
Bartosz Szeląg ◽  
Li Xie ◽  
Xi Lu ◽  
Mahesh Ganesapillai ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Oxygen Demand ◽  
Modified Model ◽  
Batch Tests ◽  
Hydrolysis Process ◽  
Water Association ◽  
The Mean ◽  
International Water ◽  
The Impact ◽  
Advanced Computer

The activated sludge models (ASMs) commonly used by the International Water Association (IWA) task group are based on chemical oxygen demand (COD) fractionations. However, the proper evaluation of COD fractions, which is crucial for modelling and especially oxygen uptake rate (OUR) predictions, is still under debate. The biodegradation of particulate COD is initiated by the hydrolysis process, which is an integral part of an ASM. This concept has remained in use for over 30 years. The aim of this study was to verify an alternative, more complex, modified (Activated Sludge Model No 2d) ASM2d for modelling the OUR variations and novel procedure for the estimation of a particulate COD fraction through the implementation of the GPS-X software (Hydromantis Environmental Software Solutions, Inc., Hamilton, ON, Canada) in advanced computer simulations. In comparison to the original ASM2d, the modified model more accurately predicted the OUR behavior of real settled wastewater (SWW) samples and SWW after coagulation–flocculation (C–F). The mean absolute relative deviations (MARDs) in OUR were 11.3–29.5% and 18.9–45.8% (original ASM2d) vs. 9.7–15.8% and 11.8–30.3% (modified ASM2d) for the SWW and the C–F samples, respectively. Moreover, the impact of the COD fraction forms and molecules size on the hydrolysis process rate was developed by integrated OUR batch tests in activated sludge modelling.

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