High temperature pyrolysis of sewage sludge as a sustainable process for energy recovery

Karaca, Cansu; Sözen, Seval; Orhon, Derin; Okutan, Hasancan

doi:10.1016/j.wasman.2018.05.034

Cited by 89 publications

(35 citation statements)

References 49 publications

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“…It should be remembered that an initial sCOD amount of 61 mg/gVS was also measured in the greenhouse crop waste. Based on the ratio of 0.35 LCH 4 /gCOD, now universally recognized as the relationship between sludge COD utilized and methane generated [ 34 ], the utilization of the available sCOD would only correspond to 21 mLCH 4 /gVS. The generation of the remaining 153 mLCH 4 /gVS has to be related to the hydrolysis of the particulate organics, requiring 0.437 g of particulate COD/gVS.…”

Section: Resultsmentioning

confidence: 99%

Impact of Alkaline H2O2 Pretreatment on Methane Generation Potential of Greenhouse Crop Waste under Anaerobic Conditions

2018

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This paper intended to explore the effect of alkaline H2O2 pretreatment on the biodegradability and the methane generation potential of greenhouse crop waste. A multi-variable experimental design was implemented. In this approach, initial solid content (3–7%), reaction time (6–24 h), H2O2 concentration (1–3%), and reaction temperature (50–100 °C) were varied in different combinations to determine the impact of alkaline H2O2 pretreatment. The results indicated that the alkaline H2O2 pretreatment induced a significant increase in the range of 200–800% in chemical oxygen demand (COD) leakage into the soluble phase, and boosted the methane generation potential from 174 mLCH4/g of volatile solid (VS) to a much higher bracket of 250–350 mLCH4/gVS. Similarly, the lignocellulosic structure of the material was broken down and hydrolyzed by H2O2 dosing, which increased the rate of volatile matter utilization from 31% to 50–70% depending on selected conditions. Alkaline H2O2 pretreatment was optimized to determine optimal conditions for the enhancement of methane generation assuming a cost-driven approach. Optimal alkaline H2O2 pretreatment conditions were found as a reaction temperature of 50 °C, 7% initial solid content, 1% H2O2 concentration, and a reaction time of six h. Under these conditions, the biochemical methane potential (BMP) test yielded as 309 mLCH4/gVS. The enhancement of methane production was calculated as 77.6% compared to raw greenhouse crop wastes.

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Section: Resultsmentioning

confidence: 99%

Impact of Alkaline H2O2 Pretreatment on Methane Generation Potential of Greenhouse Crop Waste under Anaerobic Conditions

2018

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“…Thus, a novel energy recovery perspective from wastewater should answer three main questions: Do we still require (i) high sludge ages; (ii) low excess sludge generation, and (iii) traditional anaerobic sludge digestion for biogas energy? Recent studies have revealed that novel thermochemical processes such as high‐rate pyrolysis were much more effective than anaerobic digestion, replacing biogas by syngas …”

Section: Introductionmentioning

confidence: 99%

Which activated sludge configurations qualify for maximizing energy conservation – Why?

Orhon

Allı

Sözen

2018

J of Chemical Tech & Biotech

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BACKGROUND This paper aimed to provide a critical appraisal on maximizing sludge generation and energy conservation in high‐rate activated sludge (AS) configurations. The role of gravity settling and the positive attributes of high rate membrane bioreactors were emphasized. The appraisal covered data reported in the literature on 40 different experiments testing high‐rate AS configurations for sludge generation and energy conservation. RESULTS In systems with gravity settling, effluent chemical oxygen demand (COD) was higher than 125 mg L−1 in 60% of the experiments, with similarly high effluent soluble COD values. In high‐rate MBR systems, permeate COD fluctuated around 12–18 mgCOD L−1; in gravity systems, COD loss in the effluent was higher than 200 mg L−1 in 17 runs (65%) and 300 mg L−1 in 12 runs (46%). Corresponding observed yields were only 9–43%. Membrane systems consistently yielded much higher observed yields of 50–60%. CONCLUSION For energy recovery, AS systems require a major transition, reducing the sludge age to 1.0–2.0 d; only high‐rate systems are capable of maximizing energy conservation. This argument does not apply to the contact stabilization process, which is inherently unsuitable for energy recovery. A transition is also needed to replace gravity settling by membrane systems for effective control of particulate and soluble COD components. © 2018 Society of Chemical Industry

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“…Initially in traditional systems, the major concern was always the characteristics of treated sewage; sludge disposal had always a secondary prominence, while the system design at high SRT values implicitly involved minimization of sludge generation. Later, minimization of sludge quantity was accepted as an integral part of sustainable sludge management, mainly because (i) increasing cost of final disposal, accounting for a major component of the total cost of wastewater treatment; (ii) stringent limitations imposed on low technology disposal and reuse practice, such as landfilling and reuse in agriculture due to potential health risks …”

Section: Key Drawbacksmentioning

confidence: 99%

“…However, it would be much more feasible to contemplate an energy effective alternative to sludge digestion. Anaerobic digestion should be considered as the weakest link of the conventional treatment scheme towards energy neutrality, which requires a novel energy effective alternative for this purpose, such as high rate pyrolysis, gasification, etc., rather than changing the entire treatment configuration …”

Section: Reshaping the Processmentioning

confidence: 99%

Reshaping the activated sludge process: has the time come or passed?

Orhon

Sözen

2019

J of Chemical Tech & Biotech

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Despite the amazing achievements over the years, the activated sludge (AS) process still maintains inherent drawbacks, namely gravity settling, high sludge ages, low excess sludge generation, etc., which hinder its successful operation and sometimes disrupt system performance. Substantial research on the subject has provided clear scientific evidence that time has come -or even passed -for reshaping the AS process. In the novel AS process, gravity settling will be replaced by membrane filtration, which will convert the system configuration into a membrane activated sludge (MAS) reactor; this configuration will be operated at an extremely low sludge age range of 2 to 4 days, which will maximize sludge generation and it will abandon the traditional anaerobic sludge digestion for optimizing energy recovery. It is suggested that super-fast membrane activated sludge (SFMAS) reactor be the new face of the AS process. SFMAS reactor will be the core unit of the AS process essentially limited to organic carbon (chemical oxygen demand) removal and energy recovery. The core SFMAS unit will also enable to benefit from all the assets of the AS process, such as nutrient removal, biopolymer recovery, etc., by means of hybrid systems in different configurations, i.e. by reactors with various functions that will be attached to the core unit.

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High temperature pyrolysis of sewage sludge as a sustainable process for energy recovery

Cited by 89 publications

References 49 publications

Impact of Alkaline H2O2 Pretreatment on Methane Generation Potential of Greenhouse Crop Waste under Anaerobic Conditions

Impact of Alkaline H2O2 Pretreatment on Methane Generation Potential of Greenhouse Crop Waste under Anaerobic Conditions

Which activated sludge configurations qualify for maximizing energy conservation – Why?

Reshaping the activated sludge process: has the time come or passed?

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