Anaerobic Digester Aluminate Dosing for H2S and pH Control
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Solution Overview
Problem
Existing wastewater treatment methods using acidic chemicals like ferric chloride and aluminum compounds to reduce hydrogen sulfide (H2S) in anaerobic digesters lead to reduced microbial activity, decreased methane production, and increased corrosion due to their acidic nature, while non-acidic additives fail to effectively address H2S in anaerobic digesters.
Innovation Solution
The use of an alkaline form of aluminum-containing chemicals, such as sodium aluminate, is introduced into the anaerobic digester to provide an alternative oxygen source, increasing pH, reducing H2S production, and enhancing microbial activity and methane production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If acidic chemicals like ferric chloride are used to reduce hydrogen sulfide, then H2S odor and corrosion are reduced, but microbial activity decreases and methane production is reduced
Solution Approach 1:
The patent changes the pH parameter of the chemical additive from acidic (ferric chloride) to alkaline (sodium aluminate). This parameter change allows the chemical to still react with and remove hydrogen sulfide while maintaining a pH level that does not inhibit microbial activity, thereby preserving methane production while achieving H2S control
Solution Approach 2:
The patent applies the principle of local quality by creating localized zones with different pH characteristics. The alkaline chemical provides local neutralization of H2S in the digester environment without causing system-wide pH changes that would harm microbial communities, thus achieving H2S removal while maintaining overall system productivity
2Object-generated harmful factors
If acidic chemicals like ferric chloride are used to reduce hydrogen sulfide, then H2S production is reduced, but corrosion damage increases
Solution Approach 1:
The patent converts the potentially harmful acidic property into a beneficial alkaline property. The alkaline sodium aluminate not only removes H2S effectively but also neutralizes existing acidity in the system, thereby reducing corrosion damage to metal surfaces while maintaining H2S control
3Productivity
If non-acidic additives are used to maintain microbial activity, then methane production is maintained, but H2S control effectiveness is reduced
Solution Approach 1:
The patent applies multi-functionality by selecting sodium aluminate that performs multiple functions simultaneously: it controls H2S through chemical reaction, maintains alkaline pH favorable for microbial activity, and reduces corrosion. This single additive achieves both H2S control and microbial activity maintenance without compromise
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 reduces H2S odor and corrosion, increases pH, enhances microbial activity, and promotes methane production, while minimizing struvite formation and maintaining system integrity.
Implementation Method 1
anaerobic bacteria have sulfate reducing activity that, in essence, strip the oxygen-atoms from SO42−, resulting in the formation of hydrogen sulfide (H2S)
Implementation Method 2
feed of a nitrate salt in order to provide an alternative oxygen source to sulfate for the bacteria to metabolize, resulting in the conversion of nitrate into odor-free and corrosion-free nitrogen gas
Implementation Method 3
The alkaline nature of the aluminum-containing chemical increases the pH of the anaerobic digester environment
Implementation Method 4
H2S exists in equilibrium with the HS− anion according to the following equation: As the pH decreases (and the concentration of H+ increases) the equilibrium shifts to favor the H2S species
Implementation Method 5
aluminum-containing chemicals are used in the wastewater treatment industry to react with suspended solids within the wastewater to form flocculated particles that enhance settling and dewatering of the sludge
Implementation Method 6
react with suspended solids within the wastewater to form flocculated particles that enhance settling
Implementation Method 7
Anaerobic digestion uses microorganisms to breakdown the wastewater sludge in the absence of oxygen to reduce sludge volume
Implementation Method 8
microorganisms to breakdown the wastewater sludge in the absence of oxygen
Implementation Method 9
The ferric cation reacts rapidly with hydrogen sulfide to form a highly insoluble ferric sulfide precipitate
Implementation Method 10
The ferric cation reacts rapidly with hydrogen sulfide to form a highly insoluble ferric sulfide precipitate
Data Source
AI summary
Compositions, systems, and methods of using alkaline-producing Aluminate salts in the sludge collection and digestion steps of wastewater processing to reduce acidity and/or build alkalinity, reduce hydrogen sulfide release, and reduce phosphate in the effluent.