Wastewater pH Control via Recycled CO2 Gas
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Solution Overview
Problem
Existing processes for producing microbial storage compounds like polyhydroxyalkanoate (PHA) from wastewater containing readily biodegradable COD and ammonia often require external acid for pH control, increasing operational costs and salt concentration.
Innovation Solution
A process that combines MSC production and ammonia removal by recycling CO2-containing gas and liquid from the ammonia treatment stage to the preceding biological treatment stage, minimizing the need for external acid and controlling pH levels below 9.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external acid is added for pH control in MSC production processes, then pH levels can be controlled, but operational costs increase and salt concentration in treated water increases
Solution Approach 1:
The invention converts the harmful effect of acid addition (increasing salt concentration and operational costs) into a beneficial process by using CO2 from the ammonia treatment stage to control pH in the MSC production stage. The CO2 acts as a natural acidifying agent that does not introduce harmful salts, thus converting a waste product into a useful pH control mechanism while avoiding the negative effects of traditional acid addition
Solution Approach 2:
The invention merges two separate treatment stages (MSC production and ammonia removal) into an integrated process where the CO2 produced in the ammonia treatment stage is recycled to control pH in the MSC production stage. This combination eliminates the need for external acid addition and reduces overall operational costs while maintaining effective pH control
2Reliability
If external acid is added for pH control, then pH levels can be controlled, but operational costs increase
Solution Approach 1:
The invention converts the harmful effect of acid addition (increasing operational costs) into a beneficial process by using CO2 from the ammonia treatment stage to control pH in the MSC production stage. The CO2 acts as a natural acidifying agent that does not introduce harmful salts, thus converting a waste product into a useful pH control mechanism while avoiding the negative effects of traditional acid addition
Solution Approach 2:
The system serves itself by using the CO2 produced during ammonia treatment to automatically control pH in the MSC production stage. This self-service mechanism eliminates the need for external acid purchase and addition, thereby reducing operational costs while maintaining reliable pH control
3Quantity of substance
If CO2-containing gas is recycled from ammonia treatment to MSC production stage, then external acid addition is minimized, but process complexity increases
Solution Approach 1:
The invention merges two separate treatment stages (MSC production and ammonia removal) into an integrated process where the CO2 produced in the ammonia treatment stage is recycled to control pH in the MSC production stage. This combination eliminates the need for external acid addition and reduces overall operational costs while maintaining effective pH control
Solution Approach 2:
The CO2 gas serves multiple functions: it is a product of the ammonia treatment reaction and simultaneously acts as a pH control agent in the MSC production stage. This multi-functionality reduces the need for separate pH control systems and external acid addition, simplifying the overall process despite the integration
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 reduces operational costs, lowers salt concentration in treated water, and allows for stable MSC production without external acid addition, achieving efficient PHA production and ammonia removal.
Implementation Method 1
returning CO2-containing gas and/or liquid produced in the biological ammonia treatment stage to the preceding stage of biologically treating organic waste to produce MSC
Implementation Method 2
subjecting the effluent from step (a) to ammonia-oxidising micro-organisms (AOM) to produce RBCOD-depleted and ammonia-depleted wastewater
Implementation Method 3
subjecting a feed stream containing readily biodegradable chemical oxygen demand (RBCOD) and ammonia to storage compound-accumulating micro-organisms (SCAM) to produce SCAM containing microbial storage compound (MSC)
Data Source
AI summary
Wastewater containing a significant level of dissolved readily biodegradable organic compounds matter, such as short-chain fatty acids, and ammonia can be efficiently treated to remove most or all of the organic compounds and the ammonia, with the production of microbial storage compounds such as polyhydroxylkanoates, by (i) subjecting the wastewater storage compound-accumulating microorganisms (SCAM) in the presence of oxygen, (ii) subjecting at least part of the resulting partly treated wastewater to ammonia-oxidising microorganisms (AOM) in the presence of oxygen and (iii) feeding a gas containing molecular carbon dioxide produced during step (ii) to step (i) so as to lower the pH in step (i).