Sub-critical Wet Oxidation for Nitro-hydroxy-aromatic Wastewater
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Solution Overview
Problem
Current wastewater treatment methods for nitro-hydroxy-aromatic compounds are inefficient, as they either fail to fully decompose these compounds or result in toxic by-products that are difficult to biotreat, leading to oversized biotreatment facilities and operational challenges in standalone plants.
Innovation Solution
A sub-critical wet-ox process using a sub-stoichiometric amount of oxygen and excess hydroxide, such as sodium hydroxide, under alkaline conditions to break down nitro-hydroxy-aromatic compounds, followed by ammonia stripping and biotreatment, which reduces residual COD and enhances bio-treatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If anoxic thermal treatment is used to decompose nitro-hydroxy-aromatic compounds, then the concentration of these compounds is reduced to below 20 ppm, but the BOD/COD ratio decreases making subsequent biotreatment more difficult and requiring oversized biotreatment facilities
Solution Approach 1:
The patent introduces a new parameter (oxidation potential through controlled oxygen addition) to modify the thermal treatment process. By carefully controlling the amount of oxygen added during thermal treatment, the process transforms the chemical composition of the effluent to improve the BOD/COD ratio while still achieving the required reduction of nitro-hydroxy-aromatic compounds below 20 ppm, thereby enhancing bio-treatability without requiring oversized facilities
Solution Approach 2:
The patent creates a composite treatment approach by combining thermal treatment with controlled oxidation in a single integrated process. This composite method merges the advantages of thermal decomposition (effective at breaking down recalcitrant compounds) with the benefits of oxidation (improving biodegradability), producing an effluent that is both low in toxic compounds and highly bio-treatable
2Quantity of substance
If wet air oxidation is used to treat wastewater, then organic carbon is oxidized to carbon dioxide, but the air or oxygen interferes with the degradation reactions of nitro-hydroxy-aromatic compounds resulting in higher residual concentrations above 20 ppm
Solution Approach 1:
The patent applies partial oxidation by adding a controlled, sub-stoichiometric amount of oxygen during thermal treatment rather than using full wet air oxidation. This partial action is sufficient to improve the BOD/COD ratio and enhance biodegradability while not being excessive enough to interfere with the degradation of nitro-hydroxy-aromatic compounds, thereby achieving both organic carbon removal and maintaining compound concentrations below 20 ppm
Solution Approach 2:
The patent performs preliminary thermal decomposition of nitro-hydroxy-aromatic compounds before significant oxidation occurs. By establishing the thermal degradation process first and then adding limited oxygen, the recalcitrant compounds are broken down into more biodegradable intermediates before oxidation can interfere, ensuring both effective compound removal and improved biotreatability
3Manufacturing precision
If conventional thermal decomposition is used to reduce nitro-hydroxy-aromatic compounds, then these compounds are decomposed, but significant levels of organic carbon and dissolved nitrogen compounds remain requiring extensive biotreatment
Solution Approach 1:
The patent modifies the thermal treatment parameters by introducing controlled oxygen addition during the process. This parameter change transforms the purely thermal decomposition into a thermal-oxidative process that not only breaks down nitro-hydroxy-aromatic compounds but also oxidizes associated organic carbon and nitrogen compounds, reducing the overall load requiring subsequent biotreatment and improving the BOD/COD ratio
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 approach effectively reduces the concentration of nitro-hydroxy-aromatic compounds to below 20 ppm, decreases organic carbon load, and improves bio-treatability, allowing for smaller biotreatment plants and reduced operational complexities, while also avoiding costly reactor materials and corrosion issues.
Implementation Method 1
sub-critical wet-ox process using a sub-stoichiometric amount of oxygen and excess hydroxide, such as sodium hydroxide, under alkaline conditions to break down nitro-hydroxy-aromatic compounds
Implementation Method 2
anoxic thermal treatment as described in U.S. Patent No. 4,230,567... involves heating the nitro-hydroxy-aromatic compounds in their salt form to 150-500[deg.]C with exclusion of air/oxygen at a pressure of 50-150 bars with a hold time of 5-120 minutes. This anoxic treatment can result in a thermal decomposition of the nitro-hydroxy-aromatic compounds
Implementation Method 3
subsequent biotreatment is facilitated... processes involving thermal treatment, optional ammonia stripping, and biotreatment
Data Source
AI summary
Abstract of the Disclosure A process for treating wastewater containing nitro-hydroxy-aromatic compounds using oxidative sub-critical conditions. The wastewater to be treated is adjusted to contain excess hydroxide equivalent to greater than three moles of free hydroxide per mole of total nitro-hydroxy-aromatic compounds, and a sub-stoichiometric amount of an oxidant is supplied to the wastewater. The nitro-hydroxy-aromatic compounds may include nitro-phenol salts or nitro-cresol salts.