Technology Advantages
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Fundamental Design Problems Identified in Competitor’s Digesters:
(1) Reliance on Mechanical Mixing & Stirring
This has proven to result in numerous unscheduled system shut downs from mechanical failure of these components. In
addition, these types of mechanical mixing systems are high-energy users and result in a much higher operational cost.
APS Advantage: The APS design incorporates a proven non-mechanical mixing system providing system reliability.
The system uses the Jet-Mix hydraulic mixing system that uses the water in the tanks for the mixing process. This results
in no moving or mechanical systems inside the digester tanks leading to a much lower maintenance cost and higher
system reliability.
(2) “One-Size-Fits-All”
Most systems have a single sized design capacity. Because these systems rely on a custom-built internal mixing system
or incorporate extensive pretreatment of the waste materials, system scalability becomes problematic and costly. If a
facility has a larger waste flow than the system can process, several systems are then installed, increasing the overall
system and operational costs.
APS Advantage: The APS is flexible because the design is not built around any custom internal systems; scalability
is easily accomplished to meet each facility’s waste stream volumes. This provides total flexibility in sizing each system,
allowing for cost effective expansion of the system as the operation expands.
(3) “High Liquids”
Most other systems can only process wastewater with a very low percentage of organic solids in the stream. Typically,
most systems require less than two percent organic solids in the wastewater.
APS Advantage: The APS digester technology was created to process waste streams with 30% solids content.
Recent laboratory and engineering design improvements allow system flexibility for processing high liquids, high solids or
a combination of both organic wastes.
(4) Reliance on “Custom” Manufactured Components
Extensive periods of downtime can result when custom system components fail and an extensive time required while
acquiring replacement parts. In addition, systems with custom components historically require a much higher operational
and maintenance budget.
APS Advantage: The APS design uses commercially available equipment and components. Incorporating standard
equipment and components provides a more reliable system with minimal downtime and a substantially lower operational
and maintenance cost.
(5) Single Tank Systems
These systems required both bacterial processes to take place in a single tank resulting in two fundamental faults. First,
if the process fails or “crashes” for any reason, the entire system is down. Second, the biogas production from a single
tank system is cyclic, directly following the loading of the waste stream.
APS Advantage: The APS design uses multiple tanks operating in parallel providing an optimal environment for
each bacterial process. Each tank is a stand-alone process and is loaded at different times. If one tank were to “crash”
for any reason, it may be taken off-line and the others can continue to operate. Additionally, since the organic wastes are
loaded at different times, each generates biogas at various levels and when the gas is collected in one manifold, the
resulting flow of generated biogas is nearly constant.
(1) Reliance on Mechanical Mixing & Stirring
This has proven to result in numerous unscheduled system shut downs from mechanical failure of these components. In
addition, these types of mechanical mixing systems are high-energy users and result in a much higher operational cost.
APS Advantage: The APS design incorporates a proven non-mechanical mixing system providing system reliability.
The system uses the Jet-Mix hydraulic mixing system that uses the water in the tanks for the mixing process. This results
in no moving or mechanical systems inside the digester tanks leading to a much lower maintenance cost and higher
system reliability.
(2) “One-Size-Fits-All”
Most systems have a single sized design capacity. Because these systems rely on a custom-built internal mixing system
or incorporate extensive pretreatment of the waste materials, system scalability becomes problematic and costly. If a
facility has a larger waste flow than the system can process, several systems are then installed, increasing the overall
system and operational costs.
APS Advantage: The APS is flexible because the design is not built around any custom internal systems; scalability
is easily accomplished to meet each facility’s waste stream volumes. This provides total flexibility in sizing each system,
allowing for cost effective expansion of the system as the operation expands.
(3) “High Liquids”
Most other systems can only process wastewater with a very low percentage of organic solids in the stream. Typically,
most systems require less than two percent organic solids in the wastewater.
APS Advantage: The APS digester technology was created to process waste streams with 30% solids content.
Recent laboratory and engineering design improvements allow system flexibility for processing high liquids, high solids or
a combination of both organic wastes.
(4) Reliance on “Custom” Manufactured Components
Extensive periods of downtime can result when custom system components fail and an extensive time required while
acquiring replacement parts. In addition, systems with custom components historically require a much higher operational
and maintenance budget.
APS Advantage: The APS design uses commercially available equipment and components. Incorporating standard
equipment and components provides a more reliable system with minimal downtime and a substantially lower operational
and maintenance cost.
(5) Single Tank Systems
These systems required both bacterial processes to take place in a single tank resulting in two fundamental faults. First,
if the process fails or “crashes” for any reason, the entire system is down. Second, the biogas production from a single
tank system is cyclic, directly following the loading of the waste stream.
APS Advantage: The APS design uses multiple tanks operating in parallel providing an optimal environment for
each bacterial process. Each tank is a stand-alone process and is loaded at different times. If one tank were to “crash”
for any reason, it may be taken off-line and the others can continue to operate. Additionally, since the organic wastes are
loaded at different times, each generates biogas at various levels and when the gas is collected in one manifold, the
resulting flow of generated biogas is nearly constant.
| ANAEROBIC PHASED SOLIDS (APS) DIGESTOR SYSTEMS |
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The APS process offers significant advantages over existing, anaerobic digestion technologies. These advantages stem
from several innovative design features that allow optimum environmental conditions for the system’s microorganisms,
resulting in significantly shorter retention time with an expedient and efficient conversion of organic feedstock into biogas
and beneficial value-added byproducts.
High Solids Processing:
The APS can process waste streams with a high percentage of solids, typically 30% in comparison with other anaerobic
digesters that typically handle up to 5% solids such as in wastewater treatment. This allows the APS system to digest a
wide variety of biomass materials including food processing waste, agricultural crop residues, animal waste streams and
municipal green waste.
Depending upon the type of biomass material, the APS can convert 60 to 90% of the organic solids to biogas. Any
remaining solids have a value as a soil amendment or fertilizer additives.
The APS process compared with the most recently proposed digester for solid waste conversion, sequential batch
anaerobic composting (SEBAC) reactors (Chenowyth, 1991), has demonstrated superior performance in terms of its
ability to process more solids per unit digester volume, producing a higher methane content biogas at a more constant
rate (Zhang & Zhang, 1998).
Additionally, the conventional plug-flow digesters and completely mixed digesters used in the past for digestion of solid
wastes were found to be energy intensive in operation and exhibited problematic material handling characteristics.
OPS led a multi-disciplinary group of engineers, scientists and select companies to establish the design parameters of
the APS digester technology. The design team focused on existing and potential competitive digester designs.
These design improvements were addressed and incorporated in the first pilot digester system at UCD for testing.
from several innovative design features that allow optimum environmental conditions for the system’s microorganisms,
resulting in significantly shorter retention time with an expedient and efficient conversion of organic feedstock into biogas
and beneficial value-added byproducts.
High Solids Processing:
The APS can process waste streams with a high percentage of solids, typically 30% in comparison with other anaerobic
digesters that typically handle up to 5% solids such as in wastewater treatment. This allows the APS system to digest a
wide variety of biomass materials including food processing waste, agricultural crop residues, animal waste streams and
municipal green waste.
Depending upon the type of biomass material, the APS can convert 60 to 90% of the organic solids to biogas. Any
remaining solids have a value as a soil amendment or fertilizer additives.
The APS process compared with the most recently proposed digester for solid waste conversion, sequential batch
anaerobic composting (SEBAC) reactors (Chenowyth, 1991), has demonstrated superior performance in terms of its
ability to process more solids per unit digester volume, producing a higher methane content biogas at a more constant
rate (Zhang & Zhang, 1998).
Additionally, the conventional plug-flow digesters and completely mixed digesters used in the past for digestion of solid
wastes were found to be energy intensive in operation and exhibited problematic material handling characteristics.
OPS led a multi-disciplinary group of engineers, scientists and select companies to establish the design parameters of
the APS digester technology. The design team focused on existing and potential competitive digester designs.
These design improvements were addressed and incorporated in the first pilot digester system at UCD for testing.