Wastewater Selenium Removal via Oxidation and Dissolved Air Flotation
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Solution Overview
Problem
Industrial processes such as oil and gas refining and coal gasification produce fluid waste streams with high selenium content, which are toxic even at low doses, posing a challenge for meeting regulatory standards due to the water solubility of selenium compounds.
Innovation Solution
An apparatus and method that includes an oxidizing section, coagulation section, chelation and flocculation section, and flotation section to reduce selenium content by converting selenium into a solids phase and physically separating it using dissolved gas bubbles, allowing for a flow-through processing that minimizes residence time and avoids settling ponds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional settling ponds are used to remove selenium, then selenium removal can occur, but the process takes days or weeks which is too slow for practical applications
Solution Approach 1:
The patent uses phase transition by dissolving gas under pressure and then releasing it to form bubbles, transitioning from dissolved state to gaseous bubble state to achieve rapid selenium removal without requiring long settling times
Solution Approach 2:
The patent applies pneumatic principles by using dissolved gas bubbles to lift and remove selenium-containing solids from the liquid phase, replacing traditional gravitational settling with bubble-driven flotation for much faster separation
2Ease of manufacture
If selenium compounds remain in water-soluble form, then they can be transported easily, but this water solubility makes it difficult to remove selenium to meet regulatory standards
Solution Approach 1:
The patent changes the chemical parameters of selenium compounds by adding oxidizing agents to convert water-soluble selenium compounds into a form that can be coagulated and removed, thereby achieving both ease of handling and precise control over final selenium content
Solution Approach 2:
The patent introduces intermediary substances including oxidizing agents, coagulation agents, and dissolved gas bubbles to facilitate the transformation and removal of selenium compounds, enabling effective separation while meeting regulatory standards
3Productivity
If selenium is converted to solids phase and separated quickly, then removal efficiency increases, but the selenium-containing solids phase is fragile and selenium can re-dissolve into the liquid phase
Solution Approach 1:
The patent performs preliminary chemical treatment by adding oxidizing agents and coagulation agents to stabilize the selenium-containing solids phase before the flotation separation, preventing re-dissolution and ensuring reliable removal
Solution Approach 2:
The patent maintains continuous stabilization of the selenium-containing solids phase throughout the process by ensuring proper chemical conditioning before and during separation, preventing any interruption that could lead to re-dissolution
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
The method effectively reduces selenium content by up to 99% or higher, achieving significant selenium removal within minutes or hours, compared to days or weeks in traditional processes, while maintaining chemical efficiency and avoiding re-dissolution of selenium into the liquid phase.
Implementation Method 1
The oxidizing section is configured to receive the fluid-input stream and an oxidizing agent. The oxidizing section generates a first-product stream.
Implementation Method 2
The coagulation section is configured to receive at least a portion of the oxidized output stream and a coagulation agent. The coagulation section generates a second-product stream.
Implementation Method 3
The chelation and flocculation section is configured to receive at least a portion of the second-product stream, a chelating agent and a flocculating agent. The chelation and flocculation section generates a third-product stream that contains selenium containing solids.
Implementation Method 4
The flotation section is configured to receive at least a portion of the third-product stream. The flotation section has a first portion that is configured to retain the received portion of the third-product stream and to dissolve a gas therein and a second portion that is configured to allow the dissolved gas to form bubbles in the received portion of the third-product stream. The bubbles separate the selenium containing solids from the received third-product stream for generating a final-output stream.
Data Source
AI summary
Implementations of the present disclosure relate to an apparatus and a method for reducing a selenium-content of a fluid-input stream. The present disclosure includes components and steps for performing chemical modifications of a fluid-input stream and further components and steps for performing physical modifications of a chemically-manipulated fluid stream. When the fluid-input stream has a selenium content the chemical modification of the fluid-input stream drives at least a portion of the selenium content into a selenium-containing solids phase. The chemical modifications include at least oxidation, coagulation, chelation and flocculation. The present disclosure also includes components and steps for performing physical modifications that separate and remove some or all of the selenium-containing solids phase from the liquid phase, which reduces the selenium content of the liquid phase.