Activated Sludge Microbial Sustenance During Refinery Shutdowns
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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 process for maintaining a living culture of activated sludge during shutdowns involves recycling clarified wastewater to conserve nutrients, adjusting pH and organic carbon levels, and reintroducing refinery wastewater after a period to sustain microbial activity and ensure rapid resumption of treatment capabilities.
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 microorganisms die and wastewater remediation capacity is lost
Solution Approach 1:
The system performs preliminary action by continuously aerating the activated sludge and recycling clarified wastewater to maintain microbial viability before the actual maintenance shutdown begins. This preliminary conditioning ensures microorganisms remain alive and active during the shutdown period, preventing the loss of remediation capacity that would normally occur during extended interruptions.
Solution Approach 2:
The system maintains continuity of useful action by keeping the aeration system operating and recycling clarified wastewater back to the aeration chamber throughout the maintenance shutdown. This continuous aeration and nutrient recycling sustains microbial metabolism and prevents cell death, ensuring the biological treatment system remains functional and ready for immediate operation when maintenance is complete.
2Reliability
If clarified wastewater is recycled to the aeration chamber, then nutrients are conserved and microbial sustenance is improved, but system complexity increases
Solution Approach 1:
The system applies self-service by using the clarified wastewater effluent itself as the nutrient source for sustaining microorganisms during shutdown. The clarified wastewater, which contains dissolved nutrients and organic carbon, is recycled back to the aeration chamber where microorganisms consume these nutrients. This self-sustaining loop eliminates the need for external food sources or complex supplementation systems while maintaining microbial viability.
Solution Approach 2:
The clarified wastewater recycling system serves multiple functions: it provides nutrients (organic carbon and nitrogen) for microbial sustenance, maintains dissolved oxygen levels through continuous aeration, controls pH buffering, and prevents microorganism death. This multi-functional approach consolidates several sustenance requirements into a single recycling loop, reducing overall system complexity while improving reliability.
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 effectively maintains microbial viability and treatment efficiency, reducing delays and costs associated with restarting refinery operations by maintaining optimal biochemical and growth conditions for microorganisms within the ASU.
Implementation Method 1
The clarifier allows gravity settling of the living culture and produces an effluent comprising clarified wastewater that leaves the clarifier
Data Source
AI summary
Processes and systems for maintaining a live culture of activated sludge in the activated sludge unit of a petroleum refinery during an extended refinery shut-down. In the absence of a source of refinery wastewater, a living culture of activated sludge comprising aerobic prokaryotes and/or eukaryotes that nitrify ammonia is maintained by redirecting at least a portion of clarified wastewater leaving the clarifier portion of an activated sludge unit. The redirected clarified wastewater is mixed with an organic food source that may be ammonia and/or ethyl acetate, a source of phosphate ion, and the pH is adjusted to produce a growth media that is returned to the aeration chamber of the activated sludge unit. After a time exceeding one week, the input of refinery wastewater to the aeration chamber is resumed while discontinuing the redirecting of the clarified wastewater.