Biological Selenium Removal via Immobilized Cell Bioreactor
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Solution Overview
Problem
Current chemical processes for removing selenium from wastewater are costly and time-consuming, necessitating a more efficient and cost-effective method for selenium remediation in industrial and agricultural water sources.
Innovation Solution
A biological system comprising an immobilized cell bioreactor with anaerobic microorganisms, such as selenium respiring bacteria and sulfate reducing bacteria, that reduce selenates and selenites to insoluble elemental selenium, combined with a selenide removal module using metallic or oxidized iron compounds to form iron selenide or iron sulfide precipitates, effectively removing selenium from wastewater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional chemical processes are used for selenium removal, then selenium can be removed from wastewater, but the process becomes expensive and time-consuming
Solution Approach 1:
The invention changes the chemical parameters by using anaerobic conditions and specific bacterial cultures (selenium-respiring bacteria) to transform selenium into different chemical forms (elemental selenium, selenides) that can be more efficiently removed, thereby improving both effectiveness and speed compared to conventional chemical processes
Solution Approach 2:
The invention replaces conventional chemical precipitation methods with a biological system using immobilized cells of selenium-respiring bacteria, substituting chemical reagents with biologically-mediated transformation that achieves faster and more cost-effective selenium removal
2Reliability
If conventional chemical processes are used for selenium removal, then selenium can be removed from wastewater, but operational costs and machinery requirements increase
Solution Approach 1:
The immobilized bacterial cells continuously transform selenium compounds as wastewater flows through the reactor without requiring additional chemical reagents or complex machinery, enabling the system to serve itself by using the incoming wastewater as both substrate and medium for biological transformation
Solution Approach 2:
By changing the biological parameters (using specific anaerobic bacteria under controlled pH and temperature), the system achieves effective selenium removal with simpler equipment compared to conventional chemical processes that require sophisticated dosing and mixing machinery
3Reliability
If stricter selenium limits are enforced, then water purity improves, but removal technology costs increase
Solution Approach 1:
The system performs preliminary transformation of selenium compounds into removable forms before final discharge, using the immobilized bacteria to convert soluble selenates and selenites into insoluble elemental selenium and selenides that can be easily separated, thereby achieving strict purity limits at lower cost
Solution Approach 2:
The biological substitution eliminates the need for expensive chemical reagents and complex processing equipment, making it economically feasible to achieve the strict 0.05 ppm selenium limit mandated by the EPA
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 biological system significantly reduces operational costs and time required for selenium removal, producing a safer and more environmentally friendly outcome by precipitating insoluble selenium compounds out of the water.
Implementation Method 1
anaerobic microorganisms, such as selenium respiring bacteria capable of reducing selenates and selenites to insoluble elemental selenium
Implementation Method 2
metallic or oxidized iron compounds capable of chemically reacting with selenide or sulfide compounds in the waste water to form iron selenide or iron sulfide precipitates
Data Source
AI summary
A biological system for removing selenium from waste water comprises a first immobilized cell bioreactor (ICB) and a selenide removal module. The first ICB comprises a chamber having a substrate housed therein and situated to contact the waste water flowing therethrough during use. Anaerobic microorganisms are supported on the substrate, and comprise selenium respiring bacteria capable of reducing selenates and selenites to insoluble elemental selenium and/or sulfate reducing bacteria capable of reducing selenates and selenites to insoluble elemental selenium or to soluble selenides. The selenide removal module includes metallic or oxidized iron compounds capable of chemically reacting with selenide or sulfide compounds in the waste water to form iron selenide or iron sulfide precipitates.