Anaerobic Reactor Lime Scale Removal via Dissolved Air Flotation
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Solution Overview
Problem
Anaerobic wastewater purification in the paper making industry is hindered by water hardness, which causes lime scale formation on microorganism pellets, disrupting their function and requiring costly fouling inhibitors or additional processing steps.
Innovation Solution
Implementing a dissolved air flotation step to reduce water hardness through lime precipitation before or after the anaerobic reactor, using pH adjustment and pressurized gas to form buoyant lime flocs that can be easily separated, thereby maintaining pellet functionality without increasing recirculation costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If waste water is treated in an anaerobic reactor with microorganism pellets, then organic contaminants are broken down and biogas is generated, but lime scale forms on the pellets due to water hardness, impairing their function
Solution Approach 1:
The patent applies preliminary action by removing lime scale from waste water before it enters the anaerobic reactor. A flotation step is implemented in the inflow line to separate lime scale particles from the waste water, preventing their deposition on microorganism pellets during the anaerobic treatment process
Solution Approach 2:
The patent extracts the harmful lime scale component from the waste water stream before treatment. By implementing flotation separation in the inflow line, lime scale is removed and separated from the waste water, preventing it from reaching and impairing the microorganism pellets in the reactor
2Reliability
If recirculation amount is increased to prevent pellet sinking, then pellets remain suspended in the reactor, but operational costs increase due to higher energy consumption
Solution Approach 1:
The patent prevents the need for high recirculation rates by implementing preliminary lime scale removal. By eliminating the cause of pellet weight increase (lime deposition) before treatment, normal recirculation rates suffice to maintain pellet suspension, avoiding excessive energy consumption
3Reliability
If fouling inhibitors are added to prevent lime scale formation, then pellet functionality is maintained, but operational costs increase significantly
Solution Approach 1:
The patent replaces chemical fouling inhibitors with a physical separation method. By implementing flotation to extract and remove lime scale from waste water before treatment, the need for costly chemical additives is eliminated, maintaining pellet functionality without increased operational costs
Solution Approach 2:
The patent substitutes mechanical/physical separation (flotation) for chemical treatment (fouling inhibitors). The flotation process uses air bubbles to physically separate lime scale particles from waste water, replacing the need for chemical additives and their associated 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
Effectively prevents lime precipitation on microorganism pellets, ensuring their functionality and reducing operational costs by integrating with existing systems with minimal modifications.
Implementation Method 1
the waste water is contacted with anaerobic microorganisms in the anaerobic reactor to break down contaminants contained in the waste water
Implementation Method 2
the microorganisms in particular form gas which contains methane and carbon dioxide, and which is in particular also called biogas
Implementation Method 3
The specific weight of the pellets falls due to the accumulated gas bubbles so that the pellets rise upwardly in the reactor
Implementation Method 4
separators are arranged in the middle and/or upper part of the reactor, usually in the form of gas hoods under whose crown biogas collects which forms a gas cushion under which a flotation layer of microorganism pellets and waste water is located
Implementation Method 5
Purified water freed of gas and microorganism pellets rises upwardly in the reactor and is drained off via overflows at the upper end of the reactor
Implementation Method 6
the microorganism pellets freed of the gas bubbles sink downwardly in the reactor again due to the now increased specific weight
Data Source
AI summary
The present invention relates to a process for the purification of waste water, in particular for the continuous purification of waste water in papermaking, where waste water to be purified is fed to an anaerobic reactor (12), the waste water is contacted, in the anaerobic reactor (12), with anaerobic microorganisms in order to degrade contaminants present in the waste water, and the purified waste water is discharged from the anaerobic reactor (12), where at least some of the waste water is subjected to a pressure-release flotation step (30) before being supplied to the anaerobic reactor or after being discharged from the anaerobic reactor, in order to delime the water to at least some extent. Furthermore, the present invention relates to a device which is suitable for carrying out the process according to the invention.