Ozonation Control for GAC Filter Life Extension
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Solution Overview
Problem
Existing wastewater and surface water purification processes require frequent replacement or reactivation of granular activated carbon (GAC) in biological filters, leading to process interruptions and inefficiencies in breaking down pharmaceuticals and large organic compounds.
Innovation Solution
The method involves pre-treating wastewater with ozone and adding a carbon source and flocculating agent, adjusting ozone dosages based on real-time measurements to maintain anoxic conditions, minimizing oxygen levels and extending GAC lifespan, while using a system for removing the GAC surface layer by suction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If GAC is frequently replaced or reactivated to maintain purification efficiency, then the breakdown of pharmaceuticals and large organic compounds is improved, but the process must be paused and the water treatment plant taken offline
Solution Approach 1:
Ozone is added to the water before it enters the biological filter to pre-oxidize pharmaceuticals and large organic compounds. This preliminary oxidation breaks down complex molecules into smaller, more biodegradable compounds that can be effectively processed by the GAC and microorganisms, extending the operational life of the GAC before replacement or reactivation is needed.
Solution Approach 2:
The patent controls oxygen levels in the biological filter by adjusting the ozone dosage and maintaining anoxic conditions. By precisely controlling the oxidation parameters and oxygen concentration, the GAC operates more efficiently for longer periods without requiring frequent replacement or reactivation, thus reducing process interruptions.
2Productivity
If ozone is added to break down organic compounds, then the purification of pharmaceuticals and large organic compounds is improved, but oxygen levels increase which harms anoxic bacterial denitrification
Solution Approach 1:
A buffer vessel is introduced as an intermediary between the ozone injection point and the biological filter. The buffer allows ozone to react with organic compounds and then naturally decomposes excess ozone and oxygen before water enters the anoxic biological filter. This intermediary step protects the sensitive denitrifying bacteria from oxygen exposure while still achieving the desired oxidation of contaminants.
Solution Approach 2:
Ozone is dosed periodically or continuously at controlled rates into the buffer vessel, allowing for controlled oxidation reactions. The periodic dosing strategy ensures that ozone is consumed by organic compounds in the buffer before water reaches the biological filter, preventing oxygen accumulation that would harm the anoxic denitrification process.
3Productivity
If higher ozone dosage is used to enhance breakdown of contaminants, then the purification efficiency is improved, but the amount of oxygen in water increases which disrupts anoxic conditions in the biological filter
Solution Approach 1:
The system uses online sensors to monitor dissolved oxygen levels and ozone concentration in real-time. Based on this feedback, the ozone dosage is automatically adjusted to achieve optimal oxidation of contaminants while maintaining oxygen levels below 0.5 mg/L in the biological filter. This closed-loop control ensures both high purification efficiency and reliable anoxic conditions for denitrification.
Solution Approach 2:
The patent dynamically adjusts the ozone dosage parameter based on water quality conditions and flow rate. By changing the ozone concentration parameter in response to real-time measurements, the system achieves effective contaminant breakdown while preventing excessive oxygen accumulation that would disrupt the anoxic environment needed for bacterial denitrification.
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 prolongs GAC usage to at least 12 months, enhances breakdown of pharmaceuticals and large organic compounds, and maintains anoxic conditions, reducing oxygen levels and minimizing bacterial harm, thereby improving overall water treatment efficiency.
Implementation Method 1
pre-treating comprises: online measurement, in a first buffer vessel that is arranged upstream from the filter, of dissolved organic carbon (DOC) in the water in said first buffer vessel; setting an initial ozone setpoint in gr ozone / gr of DOC... adding a dose of ozone to the ozone reactor vessel
Implementation Method 2
feeding the pre-treated wastewater or surface water to a biological filter which carries out denitrification of the water... in which biological filter the water is fed in downward flow through a filtration unit which comprises a filter bed having granular activated carbon (GAC) as the filter medium
Implementation Method 3
Bacteria commonly used in biological filters, such as Pseudomonas sp., Micrococcus sp., Achrobacter sp. and Bacillus sp. or other heterotrophic bacteria used in biological filters which operate under anoxic conditions, generally have an optimum denitrification when the pH of the water lies within the range of 7,0 - 7,5 and when the oxygen concentration of the water in the filter is below 0,5 mg / litre
Data Source
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AI summary
Method and system or purifying wastewater and surface water using a biological filter adapted for carrying out denitrification of the water under substantially anoxic conditions, in which biological filter the water is fed in downward flow through a filtration unit which comprises a filter bed having granular activated carbon as the filter medium, wherein prior to being fed to the filter the water is pretreated by feeding it through an ozone reactor vessel and subsequently through a buffer vessel, and wherein the dose of ozone added to the water in the reactor vessel is adjusted based on measurement of an concentration of ozone in an exhaust of the buffer vessel.