Nutrient Recovery from Anaerobic Digester Effluent
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Solution Overview
Problem
Existing technologies are not cost-effective or reliable for recovering nutrients from anaerobic digester waste material in farm environments, leading to environmental and health concerns due to nutrient overloads and inefficient fertilizer use.
Innovation Solution
A continuous, plug flow process for recovering nutrients from anaerobic digester effluent, involving heating and aeration to convert soluble ammonium to gaseous ammonia, followed by stripping tower processing to recover ammonium salts, while also increasing pH and settling solids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If anaerobic digester technology is adopted for waste stabilization and energy production, then environmental concerns are alleviated through odor reduction and pathogen control, but nutrient recovery is not achieved leading to nitrogen and phosphorous overloads
Solution Approach 1:
The system divides the waste treatment process into two distinct stages: first, anaerobic digestion for waste stabilization and energy production; second, a separate nutrient recovery system using acration and solids settling to extract nitrogen and phosphorous. This segmentation allows each process to optimize its function without interfering with the other.
Solution Approach 2:
The system extracts nutrients (nitrogen and phosphorous) from the anaerobic digester effluent through a dedicated acration and solids settling process. The acration reactor converts soluble ammonium to gaseous ammonia which is then stripped and recovered, while phosphorous is recovered through solids settling, effectively removing these nutrients from the waste stream.
2Loss of substance
If traditional wastewater technologies are used for nutrient control, then nutrient recovery may be achieved, but the technologies are not cost-effective or reliable in farm environments
Solution Approach 1:
The system uses the effluent from the anaerobic digester itself as the aeration source in the acration reactor, eliminating the need for external air supply infrastructure. The digester gas is redirected to provide aeration, making the system self-sufficient and reducing operational costs while maintaining reliability in farm settings.
Solution Approach 2:
The system changes the operational parameters by using controlled aeration rates and specific temperature conditions (maintaining effluent temperature between 100-170°F) to optimize both nutrient recovery efficiency and system reliability. These parameter adjustments make the process adaptable to farm environment variations.
3Loss of substance
If acration and solids settling are used for nutrient recovery, then high nutrient recovery rates are achieved with reduced costs, but the process requires heating and aeration infrastructure
Solution Approach 1:
The system merges the heating function with the existing anaerobic digester infrastructure, using the digester's thermal energy to maintain effluent temperature for the acration process. The aeration function is combined with the digester gas utilization, eliminating separate aeration equipment and reducing overall system complexity.
Solution Approach 2:
The anaerobic digester serves multiple functions: waste stabilization, energy production through biogas generation, and provision of heated effluent for the acration process. The digester gas also serves dual purposes as both a byproduct for energy and as the aeration source for nutrient recovery, maximizing resource utilization.
4Productivity
If continuous plug flow process is implemented for nutrient recovery, then operating and capital costs are reduced, but the process requires precise control of flow and treatment parameters
Solution Approach 1:
The system implements continuous plug flow processing where effluent continuously moves through the acration reactor and solids settling system without batch interruptions. This continuous operation eliminates idle time, improves equipment utilization, and reduces both operating and capital costs per unit of nutrient recovered.
Solution Approach 2:
The system incorporates pH monitoring and control mechanisms that provide feedback to maintain optimal conditions for acration and solids settling. The pH level is continuously monitored and adjusted to ensure efficient nutrient recovery while simplifying operator intervention requirements.
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
Achieves high nutrient recovery rates with reduced operating and capital costs, producing Class A biosolids and effluent, and effectively managing phosphorous and nitrogen recovery.
Implementation Method 1
heating and aeration to convert soluble ammonium to gaseous ammonia
Implementation Method 2
heating and aeration to convert soluble ammonium to gaseous ammonia
Implementation Method 3
stripping tower processing to recover ammonium salts
Implementation Method 4
settling solids
Data Source
AI summary
Methods, systems, and apparatuses for anaerobic digestion of waste fibrous material and the recovery of nutrients are provided. Methods, systems, and apparatuses disclosed herein provide mechanisms to release dissolved gases from anaerobic digester effluent. Methods, systems and apparatuses disclosed herein can recover one or more nutrients from anaerobic digested effluent using a range of temperatures, aeration rates, aeration times, pH ranges, and settling times.