Phosphorus Iron Recovery via Fermentation Oxidation
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Solution Overview
Problem
Current methods for recovering phosphorus and iron from municipal sludge face challenges such as high production costs, low market acceptance due to heavy metal pollution, and inefficient recovery processes, particularly in preparing struvite and vivianite, which require precise molar ratios and pH adjustments, making them economically and environmentally inefficient.
Innovation Solution
A method involving the mixing of iron salts with phosphorus-containing sewage, followed by fermentation and oxidation in an acidic system, which destabilizes colloids and co-precipitates iron and phosphorus as iron phosphate crystals, simplifying the recovery process and avoiding the need for precise molar ratio control, thereby reducing costs and environmental risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If struvite preparation method is used to recover phosphorus from anaerobic fermentation broth, then phosphorus recovery is achieved, but production cost increases due to need for adding large amounts of phosphate radicals, magnesium ions, and alkaline solution
Solution Approach 1:
The method utilizes the iron already present in the anaerobic fermentation broth to precipitate phosphorus as iron phosphate, eliminating the need to add external phosphate radicals, magnesium ions, and alkaline solution. The system uses its own inherent components for the recovery process, significantly reducing production costs while achieving phosphorus recovery.
Solution Approach 2:
The method changes the chemical parameters by adjusting pH to acidic conditions (pH 2-4) and using oxidation to convert ferrous iron to ferric iron, which then precipitates phosphorus. This alternative chemical pathway avoids the need for magnesium and alkaline solutions required by conventional struvite preparation.
2Quantity of substance
If struvite preparation method is used to recover phosphorus from anaerobic fermentation broth, then phosphorus recovery is achieved, but heavy metal pollution risk increases making the product unsuitable for fertilizer use
Solution Approach 1:
The method extracts and removes heavy metals from the system by utilizing the selective precipitation of phosphorus as iron phosphate. The iron phosphate precipitate forms a stable compound that excludes heavy metals, effectively separating phosphorus recovery from heavy metal contamination and producing a clean product suitable for fertilizer use.
Solution Approach 2:
The method converts the potentially harmful presence of iron in the fermentation broth into a beneficial reagent for phosphorus recovery. By oxidizing ferrous iron to ferric iron and using it for phosphorus precipitation, the method transforms a component that could contribute to contamination into the key agent for producing a clean, fertilizer-grade phosphorus product.
3Quantity of substance
If vivianite preparation method is used to recover phosphorus from anaerobic fermentation broth, then phosphorus recovery is achieved, but recovery purity is low due to difficulty in directional regulation and natural mixing with sludge
Solution Approach 1:
The method achieves high manufacturing precision by controlling pH parameters to the acidic range (pH 2-4) and using oxidation to convert ferrous iron to ferric iron. These parameter changes enable selective precipitation of phosphorus as iron phosphate with high purity, avoiding the natural mixing and low purity issues associated with vivianite formation in anaerobic conditions.
4Quantity of substance
If conventional phosphorus recovery methods are used, then phosphorus can be recovered, but the process complexity increases due to need for precise molar ratio control and pH adjustment
Solution Approach 1:
The method simplifies the process by using the iron already present in the fermentation broth, eliminating the need to precisely control molar ratios of multiple chemicals. The system uses its own inherent iron content for phosphorus precipitation, reducing process complexity while maintaining effective phosphorus recovery.
Solution Approach 2:
The method reduces process complexity by changing to a simpler parameter control regime - adjusting pH to acidic conditions (pH 2-4) and using oxidation - rather than requiring precise control of multiple molar ratios and pH adjustments needed for conventional methods. This simplifies operational procedures while achieving effective phosphorus recovery.
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 achieves high-efficiency recovery of phosphorus and iron resources, producing high-purity spherical nanoscale iron phosphate crystals with reduced impurities, enhancing the operability and market acceptance of recovered phosphorus products.
Implementation Method 1
a colloid is destabilized by physicochemical actions such as charge neutralization
Implementation Method 2
bridging and netting capture and adsorption etc to obtain iron-based chemically enhanced primary sludge
Implementation Method 3
In fermentation process, trivalent iron is reduced to divalent iron and released into fermentation broth
Implementation Method 4
trivalent iron is reduced to divalent iron
Implementation Method 5
oxidation is carried out under an acidic conditions to co-precipitate phosphorus and iron
Implementation Method 6
co-precipitate phosphorus and iron without adding additional iron ions and phosphate radicals
Implementation Method 7
achieving the recovery of sludge phosphorus resources in a form of iron phosphate
Data Source
AI summary
Present disclosure discloses a method for recovering phosphorus and iron, and use thereof. The method comprises the following steps of: S1: mixing iron salt and phosphorus-containing sewage according to the amount of the phosphorus-containing sewage to obtain a mixture, the concentration of the iron salt in the obtained mixture being 4 mg/L to 25 mg/L, fermenting the mixture at 20° C. to 60° C. for 2 days to 10 days, taking a fermentation supernatant, and removing the impurities; and S2: oxidizing the fermentation supernatant subjected to impurity removal in an acidic system. The present disclosure provides the method for recovering phosphorus and iron, which realizes high efficient recycling of phosphorus resources in sludge.