Hybrid Microalgae-Denitrifier Granules for Nitrate Removal
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Solution Overview
Problem
Current biological nitrate removal processes face challenges such as high costs, long hydraulic retention time, and secondary pollution due to the use of heterotrophic microorganisms or the need for external hydrogen gas in autotrophic methods, which are not environmentally friendly and require organic carbon sources.
Innovation Solution
A method utilizing granules of hydrogenotrophic denitrifiers and green microalgae in a continuous hybrid photobioreactor, where the microalgae produce hydrogen for denitrification, eliminating the need for external hydrogen and organic carbon sources, and achieving rapid nitrate removal with reduced hydraulic retention time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heterotrophic microorganisms are used for nitrate removal, then nitrate can be removed rapidly, but secondary pollution is produced due to remaining carbon source and organic carbon consumption
Solution Approach 1:
The patent transitions from heterotrophic to autotrophic denitrification by changing the metabolic parameters of the microorganisms. Autotrophic denitrifiers use inorganic carbon (CO2) instead of organic carbon, eliminating the need for external carbon sources and preventing secondary pollution from remaining organic matter while maintaining efficient nitrate removal
Solution Approach 2:
The system uses photosynthetic microorganisms to generate organic carbon in-situ, which is then consumed by denitrifying bacteria. This self-service mechanism eliminates the need for external carbon source addition and prevents residual organic pollution, as the carbon is immediately utilized for denitrification
2Object-generated harmful factors
If autotrophic denitrification with external hydrogen gas is used, then no organic carbon source is needed, but the process becomes costly and complex due to hydrogen handling requirements
Solution Approach 1:
Photosynthetic microorganisms serve as in-situ hydrogen producers through photosynthesis, eliminating the need for external hydrogen gas supply systems. The hydrogen generated is immediately consumed by hydrogenotrophic denitrifiers, creating a self-sustaining system that avoids the complexity and cost of external hydrogen handling while maintaining autotrophic denitrification
Solution Approach 2:
The patent combines photosynthetic microorganisms and hydrogenotrophic denitrifiers into a single integrated system. This merging allows photosynthetic organisms to produce hydrogen that is immediately used by denitrifiers, eliminating the need for separate hydrogen storage and handling infrastructure while achieving efficient nitrate removal
3Productivity
If fluidized-bed reactors or packed-bed reactors are used for biological nitrate removal, then nitrate can be removed effectively, but the construction cost is high and hydraulic retention time is long (several weeks)
Solution Approach 1:
The patent changes the operational mode from traditional continuous-flow reactors to a sequencing batch reactor mode with alternating aeration and anaerobic phases. This parameter change enables faster nitrate removal kinetics while reducing the required hydraulic retention time from several weeks to a much shorter period, and eliminates the need for expensive fluidized-bed or packed-bed reactor constructions
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 method effectively reduces nitrate levels in water to below 5 mg/L within a short hydraulic retention time, is cost-effective, and environmentally sound by producing clean products without biomass or waste, and allows for efficient separation of microbial biomass from treated water.
Implementation Method 1
green microalgae and hydrogenotrophic denitrifiers in a continuous hybrid photobioreactor
Implementation Method 2
hydrogenotrophic denitrification processes have attracted substantial attention due to producing clean products without any waste and biomass
Implementation Method 3
allows for efficient separation of microbial biomass from treated water
Data Source
AI summary
A method for nitrate removal from drinking water. The method includes adapting a sludge including hydrogenotrophic denitrifiers (HTDs) by dominating the HTDs in the sludge, cultivating a microalgae biomass, forming a microalgae-HTD biomass by cultivating a mixture of the adapted sludge and the cultivated microalgae biomass, nucleating a plurality of microalgae-HTD granules by cultivating the formed microalgae-HTD biomass in a sequencing batch (SB) mode with a constant HRT, growing the plurality of microalgae-HTD granules by cultivating the nucleated plurality of microalgae-HTD granules in an up flow (UF) mode with a reducing HRT, and continuous nitrate removal from nitrate-contaminated water with a minimum HRT over the grown plurality of microalgae-HTD granules.