Struvite Precipitation Using Desalination Brine Recirculation
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Solution Overview
Problem
Existing phosphorus recovery systems face challenges due to the high cost of magnesium as a reactant and the environmental impact of desalination brine disposal, along with unwanted precipitation issues from calcium ions in struvite precipitation processes, leading to equipment clogging and operational inefficiencies.
Innovation Solution
A method and reactor design that utilizes desalination brine as a magnesium source for struvite precipitation, incorporating a recirculation loop to dilute magnesium and calcium, adjust pH, and inject brine downstream of a recirculation pump to prevent unwanted precipitation, while also utilizing calcium ions for flocculation in wastewater treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If desalination brine is used as a magnesium source for struvite precipitation, then operational costs are reduced and brine disposal is addressed, but unwanted precipitation from calcium ions occurs causing equipment clogging
Solution Approach 1:
The patent extracts and removes calcium ions from the desalination brine through a pre-treatment step using calcium selective membranes or chemical precipitation, separating the harmful calcium component from the useful magnesium source, thereby preventing unwanted calcium-based precipitation while maintaining the cost-saving benefit of using brine as magnesium source
Solution Approach 2:
The patent applies preliminary treatment to the desalination brine before it enters the struvite precipitation reactor, including pH adjustment and calcium removal steps, to pre-condition the brine and prevent unwanted precipitation from occurring in the main reactor and downstream equipment
2Productivity
If high concentration of magnesium is added to precipitate phosphorus efficiently, then phosphorus recovery yield is improved, but unwanted precipitation and equipment clogging occur
Solution Approach 1:
The patent carefully controls and adjusts key parameters including pH (maintaining 8.0-9.5), temperature (15-30°C), and magnesium-to-phosphorus ratio (1.05-1.2) to optimize struvite precipitation while preventing unwanted precipitation, achieving high phosphorus recovery without equipment clogging
Solution Approach 2:
The patent introduces ammonia as an intermediary substance that facilitates selective struvite precipitation by providing the necessary ammonium ions while controlling the precipitation kinetics, allowing efficient phosphorus recovery without direct precipitation of other metal phosphates
3Object-affected harmful factors
If desalination brine is diluted before disposal to reduce environmental impact, then environmental hazards are reduced, but brine disposal costs increase
Solution Approach 1:
The patent enables the desalination brine to serve its own disposal problem by utilizing it as a magnesium source for struvite precipitation, transforming a waste stream requiring costly disposal into a valuable resource that contributes to phosphorus recovery and reduces operational costs
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
Enables efficient phosphorus recovery with reduced operational costs and environmental impact by avoiding unwanted precipitation, enhancing reactor durability and wastewater treatment efficiency.
Implementation Method 1
The recirculation loop enables the dilution of the magnesium and calcium, as well as a low ammonia concentration, so that no struvite or other unwanted precipitations occur there
Implementation Method 2
struvite precipitation occurs in the reactor where the conditions for struvite precipitation are fulfilled
Implementation Method 3
The recirculation loop enables the dilution of the magnesium and calcium, as well as a low ammonia concentration, so that no struvite or other unwanted precipitations occur there
Implementation Method 4
The invention has also positive effects on the wastewater treatment by helping flocculation of sludge when connected to a wastewater treatment plant
Data Source
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AI summary
The invention concerns a method for precipitation of struvite from a desalination brine (9) within a phosphorus recovery reactor (10) having an inlet portion (11) and an outlet portion (12), the method comprising the steps of • feeding a water stream (13) at the inlet portion (11) of the phosphorus recovery reactor (10), • circulating said water stream (13) throughout the phosphorus recovery reactor (10) resulting in a treated effluent (14) flowing through the outlet portion (12). According to the invention, the method further comprises • a step of recirculating at least a part of the water stream (13) circulating throughout the phosphorus recovery reactor (10) in a recirculation loop (15) of the phosphorus recovery reactor (10) from the outlet portion (12) to the inlet portion (11), and • a step of injection of the desalination brine (9) in the recirculation loop (15) of the phosphorus recovery reactor (10) at a point of injection (16). The invention also concerns a phosphorus recovery reactor (10).