Activated Sludge Recirculation for Microbial Viability During Shutdown
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Solution Overview
Problem
Extended refinery maintenance shutdowns lead to the death of microorganisms in Activated Sludge Units (ASUs), resulting in significant delays and costs when restarting refinery operations due to insufficient wastewater remediation capacity.
Innovation Solution
A system for maintaining a living culture of activated sludge during shutdowns, involving an aeration chamber, clarifier, and conduit for recycling treated wastewater with specific nutrient and pH adjustments, including acetic acid, phosphate, and ammonium ion concentrations, to sustain microbial activity and facilitate rapid resumption of wastewater treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If refinery wastewater flow is interrupted during extended maintenance shutdown, then maintenance activities can be performed, but the microbial culture in the Activated Sludge Unit dies and loses treatment capacity
Solution Approach 1:
The system performs preliminary action by establishing a recirculation mode before the extended shutdown begins. The microbial culture is maintained in a sustained growth state through continuous recirculation of treated water with added nutrients, ensuring the culture remains viable and ready for immediate treatment upon return to normal operation after maintenance shutdown
Solution Approach 2:
Treated water serves as an intermediary medium that carries essential nutrients (acetic acid, phosphate, ammonium ions) to the microbial culture during shutdown. This intermediary substance maintains the culture's metabolic activity and viability without requiring continuous influx of raw refinery wastewater
2Loss of time
If the Activated Sludge Unit is idle during extended shutdown, then no treatment is needed, but significant delays occur when restarting refinery operations due to insufficient remediation capacity
Solution Approach 1:
The system maintains continuity of useful action by keeping the microbial culture metabolically active throughout the shutdown period through recirculation of nutrient-enriched treated water. This continuous sustenance prevents culture death and ensures treatment capacity is preserved, allowing immediate resumption of full productivity when refinery operations restart
Solution Approach 2:
The system changes key parameters of the treated water (adding acetic acid at 5-20 mM, phosphate ions at 500 uM-1 mM, ammonium ions at 1-2 mM, and controlling pH to 7-8.5) to create optimal growth conditions that sustain microbial population and metabolic activity during the extended shutdown period
3Ease of operation
If nutrients are not supplemented during shutdown, then the system is simpler to operate, but microorganisms die due to lack of food source and nutrients
Solution Approach 1:
The system implements self-service by using the treated water output from the Activated Sludge Unit itself as the carrier medium for nutrient delivery. The recirculated treated water, enriched with supplemental nutrients, automatically sustains the microbial culture without requiring external complex feeding systems or manual intervention
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
The system effectively maintains microbial viability and treatment capacity, allowing for immediate resumption of refinery water treatment after extended downtime, reducing delays and associated costs by maintaining optimal biochemical and growth conditions for microorganisms.
Implementation Method 1
an aeration chamber configured to receive refinery wastewater via at least one inlet and further configured to facilitate mixing of the refinery wastewater with a living culture of activated sludge
Implementation Method 2
a clarifier configured to receive treated wastewater from the aeration chamber and facilitate settling of the living culture to produce clarified wastewater
Data Source
AI summary
The present disclosure relates generally to processes and systems for maintaining a live culture of microorganisms in the activated sludge unit of a refinery during an extended refinery shut-down.