Biosensor-Based RAS Control for Wastewater Intensification
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Solution Overview
Problem
Existing technologies face challenges in controlling feast and famine conditions in continuous-flow Biological Nutrient Removal (BNR) systems, particularly in response to dynamic loading conditions, leading to suboptimal application of biological selection pressures and reduced intensification of Conventional Activated Sludge (CAS) processes.
Innovation Solution
A system and method for real-time control of feast and famine conditions in BNR processes, utilizing biosensors to monitor soluble biodegradable carbon utilization rates and adjust the delivery of Return Activated Sludge (RAS) and Mixed Liquor Recycle (MLR) to optimize the food-to-microorganism ratio and carbon gradient throughout the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Conventional Activated Sludge (CAS) process is used for Biological Nutrient Removal (BNR), then nutrient removal function is provided, but treatment capacity is limited and infrastructure expansion is required to meet stringent discharge regulations
Solution Approach 1:
The patent changes the physical-chemical parameters of the sludge flocs by inducing densification through controlled feast-famine conditions and selective pressure application. This transforms the sludge from a loose structure to a dense structure with higher settling velocities, allowing existing infrastructure to handle higher loads without expansion.
Solution Approach 2:
The system dynamically adjusts operational parameters including RAS flow rates, aeration rates, and feast-famine cycle durations based on real-time monitoring of sludge characteristics and influent conditions. This dynamic control enables the system to maintain optimal densification conditions while adapting to varying treatment demands.
2Reliability
If external chemical addition is used to reduce effluent nutrient concentrations, then discharge requirements are met, but operational costs and chemical sludge production increase
Solution Approach 1:
The patent enables the biological system to self-regulate nutrient removal through densified sludge flocs that provide enhanced settling and biomass retention. The system uses internally generated selective pressures and feast-famine conditions to drive nutrient removal, eliminating or reducing the need for external chemical additives.
Solution Approach 2:
The patent replaces chemical-based nutrient removal mechanisms with biologically-driven mechanisms. Densified sludge flocs create physical and biological conditions that favor nutrient-removing microorganisms, substituting chemical addition with a biologically-based solution.
3Reliability
If CAS process is expanded to meet low effluent nutrient limits, then treatment effectiveness improves, but capital costs increase
Solution Approach 1:
The patent changes the physical parameters of the sludge to achieve higher settling velocities and biomass concentrations. This parameter change allows the existing infrastructure to achieve higher treatment effectiveness without physical expansion, as densified flocs improve separation and retention efficiency.
Solution Approach 2:
The system uses dynamic control of operational parameters to maximize the performance of existing infrastructure. By adjusting RAS rates, aeration, and feast-famine timing, the system extracts maximum treatment capacity from current facilities, deferring or eliminating expansion needs.
4Productivity
If biological selection pressures are applied to intensify CAS and develop Densified Activated Sludge (DAS), then treatment capacity increases, but control methodology complexity increases
Solution Approach 1:
The patent implements feedback control by monitoring sludge characteristics (settleability, density, biomass concentration) and adjusting operational parameters accordingly. This feedback mechanism maintains optimal feast-famine conditions and selective pressure application, managing control complexity through automated responses to measured parameters.
Solution Approach 2:
The control system dynamically adjusts RAS flow rates, aeration rates, and cycle timing based on real-time conditions. This dynamic control optimizes DAS development while adapting to varying influent characteristics and treatment demands, managing complexity through flexible, condition-based adjustments.
Data Source
AI summary
A system and method are disclosed for control of feast and famine conditions in continuous-flow biological nutrient removal processes to drive intensification of the activated sludge wastewater treatment process. For control of feast conditions, an upfront anaerobic zone is equipped with a biosensor to monitor real-time soluble biodegradable carbon uptake rate. Readings from the biosensor are received in a controller, which makes adjustments to operation of the anaerobic zone when readings deviate beyond said threshold limits. In one aspect return activated sludge to the anaerobic zone is modulated via an automated flow control device. Famine conditions in downstream process zones are also monitored and controlled.