The activated sludge process: State of the art

Eckenfelder, W. Wesley; Goronszy, Mervyn C.; Quirk, Thomas P.; Ganczarczyk, Jerzy J.

doi:10.1080/10643388509381729

Cited by 12 publications

(4 citation statements)

References 5 publications

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“…AD is widely employed for managing SS biosolids, which are composed of bacterial cells with an elemental makeup of C 5 H 7 O 2 N (C/N ratio = 4.3). 145 When factoring in extracellular polymeric substances and primary sludge, carbon and nitrogen contents of SS are 44 ± 9%dw (n = 7) and 6.5 ± 2.1%dw (n = 9), respectively, yielding a C/N ratio of 8.3 ± 2.7 (n = 8) (Figure S2). Consequently, studies have focused on the AcoD of SS with carbon-dense substrates like FOG.…”

Section: Co-digestion Of Municipal Organicmentioning

confidence: 99%

Understanding Anaerobic Co-digestion of Organic Wastes through Meta-Analysis

Chuenchart,

Surendra,

Khanal

2024

ACS EST Eng.

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Anaerobic co-digestion (AcoD) is becoming increasingly popular in the biogas industry for its numerous advantages over mono-digestion, including balanced nutrient profiles, enhanced process stability, synergistic methane production, and reduced greenhouse gas emissions. However, varying results across AcoD studies highlight the need for an extensive meta-analysis of a large data set to better understand these synergies. Here, we compared methane yields from 432 data sets, based on the ratio of means, from AcoD and mono-digestion. The relative synergistic index (RSI) revealed synergistic effects in AcoD of lignocellulosic biomass with animal manures, particularly pig (RSI = 1.91) and chicken manures (RSI = 1.71). Due to its rapid biodegradability, food waste AcoD also demonstrated synergistic effects with both animal manures (RSI = 1.28) and lignocellulosic biomass (RSI = 1.41). After regrouping data by high-carbon cosubstrates, interpretable machine learning models identified temperature, which accelerates the hydrolysis of lignocellulosic biomass and emulsification of fats, oils, and grease, as the key factor influencing methane yield. Furthermore, experimental validation using food waste and sewage sludge co-digestion confirmed the superiority of multivariable linear regression in predicting specific methane yield over other models in terms of simplicity and efficiency.

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Section: Co-digestion Of Municipal Organicmentioning

confidence: 99%

Understanding Anaerobic Co-digestion of Organic Wastes through Meta-Analysis

Chuenchart,

Surendra,

Khanal

2024

ACS EST Eng.

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Section: Introductionmentioning

confidence: 99%

“…Mostly, nitrogen removal performance was found to be the critical performance indicator (Orhon, 2015). CAS is accommodated by different process technology families which are continuous activated sludge system with constant water level and separate reactor compartment and settler (Eckenfelder, 1998); single‐tank system operated at variable water level with time control (Silverstein & Schroeder, 1983); and alternating activated sludge processes with constant water level and time control: –BIODENITRO (Christensen, 1975) with alternating aeration tanks –BIOCOS (Ingerle, 2008, 2018) with alternating settler compartments. …”

Section: Introductionmentioning

confidence: 99%

All you need is air—Alternating activated sludge system BIOCOS without electromechanical equipment

Wett

Brückl

Aichinger

et al. 2021

Water Environment Research

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Exclusively air‐driven operation is an essential feature of the cyclic activated sludge process BIOCOS. Switching the air‐flow between diffusers, agitation, and recycle air‐lift keeps operation and maintenance simple and leads to significant energy savings used for mechanical devices. The overall energy demand for the whole biological system with settling was found to be below 20 kWh/PE.a. This hybrid technology shows a constant water level characteristic for continuous flow systems and time‐based control. Modular rectangular tank configuration and high solids operation targets a compact footprint. Process wise, the settling sludge blanket in the two alternating settling tanks was found to contribute considerably to post‐denitrification and enhances phosphorus removal. During the last years, approximately 200 BIOCOS plants have been implemented mainly in Germany, Austria, Spain, and China, some of the operational results are presented in this paper. Practitioners points BIOCOS is a hybrid process with alternating settling tanks at constant water level. The performance of demonstration plants shows high resilience against hydraulic and organic peak loads. The energy demand for the process was found to be very small. The process is driven with no electromechanical equipment but one main blower station. The sludge blanket in the alternating settler significantly contributes to denitrification and phosphorus removal.

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“…In the EA process, the aeration is carried out over an extended period of time using a long HRT (18 to 24 hours) and a low food-tomicroorganism (F/M) ratio (high SRT) which results in little sludge but higher oxygen uptake per kg of BOD removed. This method was most commonly used where ease of operation and low sludge generation are needed (Eckenfelder & Grau, 1998). The volume of the extended aeration tank was calculated to be 23,000 m 3 using the average monthly influent flow and an HRT of 22 hrs.…”

Section: Treatment Scenarios and Design Parametersmentioning

confidence: 99%

Comparative Environmental and Economic Assessment of the Zahle Wastewater Treatment Plant in Lebanon under Different Scenarios. (c2022)

Ghosn¹

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Assessing the environmental impacts of wastewater treatment plants (WWTPs) is a growing concern that needs to be addressed. Although several studies have been published on the environmental performance of WWTPs, few have been reported from developing countries, especially in Lebanon. In this study, the environmental and economical performance of an oxidation ditch-based secondary treatment technology in Zahle, Lebanon, was evaluated using life cycle assessment (LCA) and life cycle cost (LCC) in conjunction with computer modeling. The current plant was calibrated and validated using GPS-X v. 8.0 software and three hypothetical scenarios were suggested and compared with its current state. The first scenario (S1) included adding anaerobic sludge digestion. The second scenario (S2) included using extended aeration. The third scenario (S3) included using a five-stage Bardenpho (FSB) process. For this purpose, a series of LCAs were performed using SimaPro 9.3.0.3 together with the ecoinvent 3.8 database, and the ReCiPe midpoint (H) and endpoint (H/A) methodologies. A functional unit of 1 m3 of treated wastewater was used as a basis. The WWTPs costs were estimated using the CapdetWorks v4.0 software. Further, LCA was monetized using external costs. The analysis revealed that the environmental categories were primarily influenced by energy consumption. The current plant had a global warming effect of 0.678 kgCO2 eq/m3. Normalized results showed that the first scenario was the most environmentally friendly alternative in the human carcinogenic toxicity impact category quantified as follows: S2 < S0 < S3 < S1. Normalized results also showed that freshwater ecotoxicity and human carcinogenic toxicity were the main impact categories. The economic evaluation revealed that the addition of anaerobic digestion led to more expenses, while S0 process was found to be the most cost-effective. The descending order concerning environmental costs was as follows: S2(0.171$/m3) > S0(0.159$/m3) > S3 (0.147$/m3) > S1 (0.117$/m3). Considering the collective evaluation, scenario S1 was chosen as a potential enhancement for the Zahle WWTP (ZWWTP). This study emphasized the importance of the environmental impact assessment in the wastewater treatment (WWT) sector and contributed to the growing body of literature related to WWT in Lebanon. Further research is needed to provide a clear data collection process that will increase the modeling precision of an existing plant and accurately reflect the outcomes.

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The activated sludge process: State of the art

Cited by 12 publications

References 5 publications

Understanding Anaerobic Co-digestion of Organic Wastes through Meta-Analysis

Understanding Anaerobic Co-digestion of Organic Wastes through Meta-Analysis

All you need is air—Alternating activated sludge system BIOCOS without electromechanical equipment

Comparative Environmental and Economic Assessment of the Zahle Wastewater Treatment Plant in Lebanon under Different Scenarios. (c2022)

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