Underlying Mechanistic Principles and Proposed Modeling Approach for Waste Activated Sludge Reduction Technologies

Whitlock, Dru; Sandino, Julián; Novak, John T.; Johnson, Bruce; Fillmore, Lauren

doi:10.2175/193864709793846349

Cited by 5 publications

(5 citation statements)

References 4 publications

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“…It is reported that the flash reaction causes rupture of the cell, thus the step is important for sufficient hydrolysis to occur (Whitlock et al, 2009). Gurieff et al (2011) compared both batch and continuous thermal hydrolysis using the Biothelys and the Exelys process and found that the solubilization of COD and VSS were similar for both processes, with slightly better results for the continuous process, indicating that effective hydrolysis occurred with both processes.…”

Section: Figure 3: Process Flow Schematic Of An Exlyse Thermal Hydrolmentioning

confidence: 99%

“…The type of solids and thus the amount of ammonia expected in the digestion process is the limiting parameter regarding the percent solids feed to digestion. The drastic changes in solids rheology with a significantly reduced viscosity allows proper mixing at high solids contents with typical digestion mixing equipment (Whitlock et al, 2009). Feeding MAD at a higher solid content allows significant reduction in digestion volume requirements thus providing significant capital savings since construction of new digesters, which is a major capital investment, may be avoided.…”

Section: Introductionmentioning

confidence: 99%

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Comparing Thermal Hydrolysis Processes (CAMBI™ and EXELYS™) For Solids Pretreatmet Prior To Anaerobic Digestion

Abu-Orf¹,

Goss²

2012

proc water environ fed

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Thermal hydrolysis is a sludge conditioning process applied to dewatered cake upstream of anaerobic digestion. The advantages of thermal hydrolysis are producing a Class A biosolids product, making residuals more digestible, and improving the dewatering characteristics of the resulting biosolids. Applying thermal hydrolysis to dewatered cake significantly reduces the viscosity allowing digesters to operate at much higher solids contents than conventional digesters significantly reducing volume requirements. There are currently two commercially available thermal hydrolysis processes, Cambi and Exelys (which is the second generation of Biothelys). They both apply pressure (120-130 psi) and temperature (330°F) for a set retention time of about 30 minutes to hydrolyze the solids prior to digestion. The major difference between the two processes is that Cambi consists of a series of batch tanks while Exelys utilizes a continuous plug flow reactor. The Cambi process is a more established technology with more than 25 installations worldwide while the Exelys process is still new with only one demonstration plant. The thermal hydrolysis process is normally applied as a pretreatment to anaerobic digesters in the Lysis -Digestion (LD) mode, however, the Exelys process can also be placed between two digestion steps which is known as the Digestion -Lysis -Digestion (DLD) mode of operation. Results from a desktop study for a "green field" 40 dtpd plant indicate that both thermal hydrolysis processes in the LD mode are economically favorable when compared to conventional mesophilic digestion; however, Exelys LD provides a thermal hydrolysis solution at a lower cost yielding a more favorable life cycle cost then the more traditional Cambi process. The Exelys system in the DLD mode was not found to be economically favorable for a "green field" system.

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Section: Figure 3: Process Flow Schematic Of An Exlyse Thermal Hydrolmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparing Thermal Hydrolysis Processes (CAMBI™ and EXELYS™) For Solids Pretreatmet Prior To Anaerobic Digestion

Abu-Orf¹,

Goss²

2012

proc water environ fed

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“…! 16 After 20-30 min hydrolyzing treatment, the sterilized sludge is pumped to the flash tank, where the rupture of the cells occurs due to the fast pressure drop [51]. Generally, the sludge from the flash tank is too hot to feed a mesophilic digester and it needs to be cooled to 42-44 °C by heat transfer.…”

Section: Thermal Pretreatmentsmentioning

confidence: 99%

“…Specifically, when the sludge enters the flash tank, the water contained in the flocs and inside the cells partially vaporizes, resulting in their structure damaging. Thus, the presence of the flash tank seems to be important for a sufficient hydrolysis of the sludge [51,[53][54][55]. On the other hand, some studies highlighted that flash tank may not result to valuable differences in terms of COD and VSS solubilization !…”

Section: Thermal Pretreatmentsmentioning

confidence: 99%

High-solid anaerobic digestion of sewage sludge: challenges and opportunities

et al. 2020

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“…This maximizes the yield of digestion intermediates readily consumed by anaerobic biota, which in turn increases the production of biogas and increases the potential for CHP generation. Recent research conducted by the Water Environment Research Foundation (Whitlock, Sandino, Novak, Johnson, and Fillmore 2009) indicates significant improvements in the dewatering characteristics of the stabilized biosolids as a result of these preconditioning steps. Some of these processes and technologies have been demonstrated in the laboratory and at the pilot scale while others have been installed at operating treatment plants.…”

Section: Pretreatment Of Wastewater Residual Solidsmentioning

confidence: 99%

Sustainable Energy Management: Achieving Energy Independence at Wastewater Utilities

Whitlock¹,

Sandino²,

Shea³

et al. 2009

proc water environ fed

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This paper focuses on ideas and examples of wastewater facilities attaining energy independence through conservation, efficient systems, and development of renewable energy. Although viable renewable energy alternatives are available, there does not appear to be one renewable energy source that is a panacea for the global energy demand. Instead, it is generally accepted that a global sustainable energy system will be a combination of many different renewable resources. With this vision, no one nation or society would be dependent on another for energy, thus creating universal energy independence. Ultimately, energy independence would be achieved by (1) energy conservation, most importantly, (2) creating more efficient systems, and (3) renewable energy provided by a combination of sources, such as solar power, wind power, hydropower, geothermal power, and bioenergy. Hence, a movement toward maximizing utilization of biologically derived energy coupled with other renewable energy sources has recently become of more interest to wastewater facility management as part of the global renewable energy portfolio.While the challenges faced by engineers are imposing, the industry has responded strongly in recent decades with novel and valuable research efforts and innovative engineering approaches to applying these concepts to advanced performance in the field. These technological advances can be utilized for generation of renewable energy. However, additional research and implementation of many of the technologies discussed in this paper will be necessary before the change from nonrenewable to renewable sources of energy is streamlined. With a new emphasis on renewable energy in the United States and globally, the change will likely be rapid in the first half of this century. Hence, the goal of wastewater facilities achieving energy independence is a worthy one and consistent with the current progression to sustainable systems.

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Underlying Mechanistic Principles and Proposed Modeling Approach for Waste Activated Sludge Reduction Technologies

Cited by 5 publications

References 4 publications

Comparing Thermal Hydrolysis Processes (CAMBI™ and EXELYS™) For Solids Pretreatmet Prior To Anaerobic Digestion

Comparing Thermal Hydrolysis Processes (CAMBI™ and EXELYS™) For Solids Pretreatmet Prior To Anaerobic Digestion

High-solid anaerobic digestion of sewage sludge: challenges and opportunities

Sustainable Energy Management: Achieving Energy Independence at Wastewater Utilities

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