Biogas Scrubber Loop for H2S Control in Anaerobic MBRs
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Solution Overview
Problem
Anaerobic membrane bioreactors face issues with excessive dissolved sulfide concentrations that are toxic to microorganisms, particularly methanogens, due to the production of hydrogen sulfide gas during wastewater treatment, leading to membrane fouling and operational inefficiencies.
Innovation Solution
A method and system involving a biogas scrubber to reduce hydrogen sulfide concentration by withdrawing a fraction of biogas from the headspace, treating it with a chemical or biological scrubber, and recirculating the scrubbed biogas to control sulfide levels within the anaerobic membrane bioreactor, while another fraction is used for membrane scouring to prevent fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If biogas is used for membrane scouring to prevent fouling, then membrane performance is improved, but hydrogen sulfide concentration increases to toxic levels
Solution Approach 1:
The biogas stream is segmented into two separate flows: one portion is directed to the membrane scouring system while another portion is directed to the hydrogen sulfide removal system. This segmentation allows each subsystem to perform its function optimally without interfering with the other, resolving the contradiction between maintaining membrane performance and controlling hydrogen sulfide levels.
Solution Approach 2:
A dual-pathway distribution system acts as an intermediary mechanism that splits the biogas flow between two different destinations based on system needs. The control system mediates the allocation of biogas, directing appropriate portions to scouring versus H2S removal, thereby balancing membrane performance requirements with hydrogen sulfide concentration control.
2Object-affected harmful factors
If biogas is directed to a scrubber to remove hydrogen sulfide, then hydrogen sulfide concentration is reduced, but membrane scouring effectiveness decreases
Solution Approach 1:
The biogas flow is divided into segments where one segment handles hydrogen sulfide removal through the scrubber while another segment maintains membrane scouring functions. This ensures both H2S concentration reduction and membrane performance maintenance occur simultaneously through parallel processing pathways.
Solution Approach 2:
The biogas distribution system performs multiple functions by routing gas to different destinations based on operational requirements. The same biogas source serves both membrane scouring and hydrogen sulfide removal purposes, making the system multi-functional and adaptable to different operational conditions.
3Duration of action of stationary object
If all biogas is used for membrane scouring, then fouling is prevented, but hydrogen sulfide accumulates to toxic levels for microorganisms
Solution Approach 1:
The biogas stream is segmented into functional portions: one portion dedicated to membrane scouring to extend membrane lifespan, and another portion directed to hydrogen sulfide removal to protect microorganisms from toxicity. This segmentation enables simultaneous achievement of both long-term membrane durability and microbial health protection.
Solution Approach 2:
The hydrogen sulfide that would otherwise be harmful to microorganisms is converted into a manageable stream by directing it to the scrubber system. The harmful H2S is removed through chemical or biological processes in the scrubber, transforming a toxic byproduct into a controlled parameter that no longer threatens system biology.
4Object-affected harmful factors
If all biogas is directed to a scrubber, then hydrogen sulfide is removed, but membrane fouling increases due to reduced scouring
Solution Approach 1:
The biogas flow is segmented into two functional streams: one stream is routed to the scrubber for hydrogen sulfide removal while the other stream is maintained for membrane scouring. This segmentation ensures that both H2S concentration control and fouling prevention are achieved through simultaneous parallel operations rather than competing for the same gas resource.
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
Effectively reduces hydrogen sulfide concentration in the biogas to non-toxic levels, maintaining microorganism viability and reducing membrane fouling, thereby enhancing the efficiency and longevity of the anaerobic membrane bioreactor system.
Implementation Method 1
directing a pre-determined amount of the withdrawn biogas to a scrubber to produce a scrubbed biogas having a lower concentration of the hydrogen sulfide than the biogas
Implementation Method 2
treating it with a chemical or biological scrubber
Implementation Method 3
directing a remainder of the withdrawn biogas to a gas distributor within the anaerobic membrane bioreactor to scour the membrane
Implementation Method 4
directing a wastewater comprising sulfur and a chemical oxygen demand (COD) to the anaerobic membrane bioreactor to produce a permeate and a biogas comprising the hydrogen sulfide
Data Source
AI summary
Methods of controlling hydrogen sulfide concentration of a biogas occupying an anaerobic membrane bioreactor (AnMBR) containing a submerged membrane are disclosed herein. Methods of controlling dissolved sulfide concentration of a mixed liquor within the AnMBR are disclosed. The methods include directing wastewater containing sulfur and a chemical oxygen demand (COD) to an AnMBR, withdrawing at least a fraction of the biogas from the AnMBR, directing a pre-determined amount of the withdrawn biogas to a scrubber, directing a remainder of the withdrawn biogas to a gas distributor, and directing the scrubbed biogas to the AnMBR. Systems for treating wastewater having sulfur and COD are disclosed. The systems include an AnMBR, a scouring gas closed loop, a scrubber, and a control mechanism for directing biogas to the scrubber and to a gas distributor. Methods of retrofitting a system for treating wastewater having sulfur and COD are disclosed.