Effects of Thickened Excess Sludge Pre-Treatment Using Hydrodynamic Cavitation for Anaerobic Digestion

The main purpose of this study was the assessment of the possibility of increasing the production of biogas through the pre-treatment of thickened excess sludge (TES) by means of the hydrodynamic cavitation (HC) conducted at different levels of energy density (EL) i.e., 70, 140 and 210 kJ/L. The experiments were performed on a pilot scale, and a mixture of thickened primary sludge (TPS) and TES was used as digester feed. The results documented that an important parameter determining the possibility of obtaining an enhanced methane production is the value of energy input in the HC process. This parameter determines the changes occurring in sludge as a result of disintegration (i.e., sludge floc deagglomeration, lysis of cells, re-flocculation process and the related release of compounds susceptible to biodegradation from sludge flocs). The maximum increase in methane yield (MY) of 152% was obtained for EL = 140 kJ/L. In this case, HC mainly caused sludge floc deagglomeration. An increase in MY was also recorded when TES was subject to the disintegration process at EL = 210 kJ/L. However, it was 4.3 times lower than that observed for EL = 140 kJ/L. Pre-treatment of TES at EL = 70 kJ/L did not contribute to an increase in methane production.

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Two combined techniques to enhance anaerobic digestion of sludge

Water Science & Technology ◽

10.2166/wst.2002.0320 ◽

2002 ◽

Vol 46 (10) ◽

pp. 167-172 ◽

Cited By ~ 3

Author(s):

G. Moeller-Chávez ◽

S. González-Martínez

Keyword(s):

Anaerobic Digestion ◽

Yeast Extract ◽

Methane Production ◽

Influencing Factor ◽

Removal Rates ◽

Primary Sludge ◽

Methanogenic Activity ◽

Iron Nickel ◽

Pre Treatment ◽

Treatment Procedures

The rate-limiting step during anaerobic digestion is the hydrolysis of the particulate organic matter and methanogenesis. Certain elements, such as iron, nickel and cobalt and some growth factors such as coenzymes are needed for the adequate growth of the organisms. The main objective of this research was to enhance anaerobic digestion of primary sludge combining thermal and alkaline pre-treatment with stimulation of the methanogenic activity by adding yeast extract. Primary sludge was exposed, separately, to alkaline and thermal pre-treatment procedures. After this pre-treatment, different amounts of yeast extract were added to the sludge. The best COD, TSS and VSS removal rates were observed without pre-treatment and with the addition of 0.1% in weight of yeast extract. The highest specific methane production was obtained with thermal pre-treatment and 0.1% yeast addition. A second experimental stage was run for a closer analysis of the preliminary results. Thermal pre-treatment and 0.1% yeast addition was tested. The best results regarding both COD, TSS and VSS removal rates and methane production were obtained without thermal pre-treatment and with addition of yeast extract. The calculated F-values for the ANOVA-test show that the main influencing factor was the addition of yeast extract where the Biochemical Methane Production was doubled compared with the blank. The highest values for the hydrolysis constants were obtained at hydraulic retention times of six days after adding 0.1% of yeast extract.

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Enhancement of methane production and phosphorus recovery with a novel pre-treatment of excess sludge using waste plaster board

Journal of Environmental Management ◽

10.1016/j.jenvman.2019.109844 ◽

2020 ◽

Vol 255 ◽

pp. 109844

Author(s):

Sui Kanazawa ◽

Norihisa Matsuura ◽

Ryo Honda ◽

Ryoko Yamamoto-Ikemoto

Keyword(s):

Methane Production ◽

Phosphorus Recovery ◽

Excess Sludge ◽

Pre Treatment

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Efficiency of integrated electrooxidation and anaerobic digestion of waste activated sludge

Biotechnology for Biofuels ◽

10.1186/s13068-021-01929-7 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

J. A. Barrios ◽

A. Cano ◽

F. F. Rivera ◽

M. E. Cisneros ◽

U. Durán

Keyword(s):

Anaerobic Digestion ◽

Current Density ◽

Methane Production ◽

Energy Recovery ◽

Energy Analysis ◽

Mathematical Optimization ◽

Waste Activated Sludge ◽

Bdd Electrode ◽

Vs Removal ◽

Pre Treatment

Abstract Background Most of the organic content of waste activated sludge (WAS) comprises microbial cells hard to degrade, which must be pre-treated for energy recovery by anaerobic digestion (AD). Electrooxidation pre-treatment (EOP) with boron-doped diamond (BDD) electrode have been considered a promising novel technology that increase hydrolysis rate, by the disintegrating cell walls from WAS. Although electrochemical oxidation could efficiently solubilize organic substances of macromolecules, limited reports are available on EOP of WAS for improving AD. In this endeavour, the mathematical optimization study and the energy analysis of the effects of initial total solids concentrations [TS] of WAS and current density (CD) during EOP on the methane production and removal of chemical oxygen demand (COD) and volatile solids (VS) were investigated. Because limited reports are available on EOP of WAS for improving biogas production, it is not well understood; however, it has started to attract interest of scientists and engineers. Results In the present work, the energy recovery as biogas and WAS conversion were comprehensively affected by CD and [TS], in an integrated EOP and AD system. When working with WAS at 3% of [TS] pre-treated at current density of 24.1 mA/cm2, the highest COD and VS removal were achieved, making it possible to obtain the maximum methane (CH4) production of 305 N-L/kg VS and a positive energy balance of 1.67 kWh/kg VS. Therefore, the current densities used in BDD electrode are adequate to produce the strong oxidant (hydroxyl radical, ·OH) on the electrode surface, allow the oxidation of organic compounds that favours the solubilization of particulate matter and VS from WAS. Conclusions The improvement of VS removal and COD solubilization were due to the effects of pre-treatments, which help to break down the microbial cells for faster subsequent degradation; this allows a decomposition reaction that leads to biodegrade more compounds during AD. The balance was positive, suggesting that even without any optimization the energy used as electricity could be recovered from the increased methane production. It is worth noting that this kind of analysis have not been sufficiently studied so far. It is therefore important to understand how operational parameters can influence the pre-treatment and AD performances. The current study highlights that the mathematical optimization and energy analysis can make the whole process more convenient and feasible.

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Assessment of the papermaking potential of processed Miscanthus × giganteus stalks using alkaline pre-treatment and hydrodynamic cavitation for delignification

Ultrasonics Sonochemistry ◽

10.1016/j.ultsonch.2021.105462 ◽

2021 ◽

Vol 72 ◽

pp. 105462

Author(s):

Dimitrios Tsalagkas ◽

Zoltán Börcsök ◽

Zoltán Pásztory ◽

Parag Gogate ◽

Levente Csóka

Keyword(s):

Hydrodynamic Cavitation ◽

Miscanthus Giganteus ◽

Pre Treatment

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Treatment of real industrial-grade dye solutions and printing ink wastewater using a novel pilot-scale hydrodynamic cavitation reactor

Journal of Environmental Management ◽

10.1016/j.jenvman.2021.113301 ◽

2021 ◽

Vol 297 ◽

pp. 113301

Author(s):

Charikleia Zampeta ◽

Kleio Bertaki ◽

Irene-Eva Triantaphyllidou ◽

Zacharias Frontistis ◽

Dimitris V. Vayenas

Keyword(s):

Pilot Scale ◽

Hydrodynamic Cavitation ◽

Industrial Grade ◽

Printing Ink ◽

Dye Solutions

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Enhanced sludge conditioning by enzyme pre-treatment: comparison of laboratory and pilot scale dewatering results

Water Science & Technology ◽

10.2166/wst.2006.544 ◽

2006 ◽

Vol 54 (5) ◽

pp. 33-41 ◽

Cited By ~ 21

Author(s):

D. Dursun ◽

M. Turkmen ◽

M. Abu-Orf ◽

S.K. Dentel

Keyword(s):

Extracellular Polymeric Substances ◽

Treatment Plant ◽

Pilot Scale ◽

Solid Content ◽

Filter Press ◽

Treatment Comparison ◽

Anaerobically Digested Sludge ◽

Network Strength ◽

Pre Treatment ◽

Solids Content

The effect of enzyme pre-treatment on dewaterability of anaerobically digested sludge was investigated at both laboratory and pilot scale. Our results revealed a significant increase in cake solid content (27% cake solids compared to 18% without enzyme pre-treatment), using an enzyme dose of only 20 mg/L. In order to assess practical application, enzyme pre-treatment was applied at the Wilmington, Delaware (US) wastewater treatment plant, using a pilot-scale centrifuge. However, the efficiency reached in laboratory scale could not be obtained in pilot scale, where the final cake solids content did not exceed 20%. Centrifuge and belt filter press (simulated by Crown Press™) dewatering were compared in terms of the process efficiencies in the absence and presence of enzyme pre-treatment. Possible factors that might cause the differences were tested by experimental and statistical comparisons. Results indicated that the higher shear applied in centrifugation is responsible for the lack of improved cake solids. The network strength of sludge determined by rheological measurements revealed that enzymatic treatment weakens the gel structure of the sludge floc through the hydrolysis of extracellular polymeric substances; this allows improved dewatering by filtration processes, but leads to floc deterioration when subjected to high shear during centrifugation.

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