Single-Phase Anaerobic Digester With Leachate Recirculation
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Solution Overview
Problem
Traditional single-phase anaerobic digestion systems for waste management face challenges such as acid accumulation and pH drop due to imbalanced microbial processes, leading to inefficient methane production, while two-phase systems are costly and difficult to implement, and static containers suffer from mass transfer issues and high construction costs.
Innovation Solution
A single-phase solid waste digester with a reactor vessel, sprinkler system for water and bacteria distribution, and drainage system for leachate recirculation, allowing for efficient conversion of volatile fatty acids to methane within a self-perpetuating anaerobic digestion process using a single reactor vessel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If single-phase anaerobic digestion is used, then methane production is achieved, but acid accumulation and pH drop occur due to imbalanced microbial processes
Solution Approach 1:
The patent introduces an internal circulation system that divides the single reactor into functional zones: an upper acidogenesis zone and a lower methanogenesis zone. The circulation pump creates a two-phase flow pattern where leachate rises to the top for acid production, then returns to the bottom for methane conversion, effectively segmenting the microbial processes within one vessel.
Solution Approach 2:
The patent uses leachate as an intermediary medium to transfer volatile fatty acids from the upper zone to the lower zone. The circulation system acts as a mediator, continuously moving the liquid phase between zones to balance acid production and consumption, preventing acid accumulation while maintaining process stability.
2Reliability
If two-phase anaerobic digestion systems are used to avert acid accumulation, then process stability is improved, but device complexity and construction cost increase
Solution Approach 1:
The patent merges the functions of two separate reactors (acidogenesis reactor and methanogenesis reactor) into a single integrated reactor vessel. The internal circulation system combines the liquid flow paths of both phases within one container, reducing the number of external connections, seals, and structural components needed while maintaining the two-phase functional separation.
Solution Approach 2:
The single reactor vessel performs multiple functions: it serves as both the acidogenesis reactor and the methanogenesis reactor, contains the internal circulation pump, houses the sprinkler system, and provides both solid waste containment and liquid leachate circulation. This multi-functionality eliminates the need for separate dedicated vessels for each phase.
3Ease of manufacture
If static containers are used for waste digestion, then construction cost is reduced, but mass transfer problems and low biogas yield occur
Solution Approach 1:
The patent transforms the static container into a dynamic system by introducing an internal circulation pump that actively moves leachate between the upper and lower zones. The sprinkler system dynamically distributes liquid over the solid waste bed, creating moving fluid-solid contact that enhances mass transfer and prevents the stagnation problems of static systems.
Solution Approach 2:
The patent uses hydraulic circulation to drive the two-phase flow pattern. The pump creates pressure differential that moves leachate through the solid waste bed, and the system relies on hydraulic principles for liquid distribution and collection, replacing the need for complex mechanical mixing while improving mass transfer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in higher biogas production with a shorter digestion period, reduced costs, and the ability to handle larger volumes without the need for separate gas storage, while maintaining efficient methane conversion and minimizing environmental impact.
Implementation Method 1
single phase anaerobic digestion system can produce gas with 40-60 percent methane
Implementation Method 2
the leachate is then re-circulated through the solid waste bed until a desired level of volatile fatty acids ('VFA's) is achieved in the leachate
Data Source
AI summary
An organic solid waste digester for producing methane from solid waste, the digester comprising a reactor vessel for holding solid waste, a sprinkler system for distributing water, bacteria, and nutrients over and through the solid waste, and a drainage system for capturing leachate that is then recirculated through the sprinkler system.