Enzyme-Assisted Process Water Cleaning for Paper Recycling at pH 8 or Lower

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Solution Overview

Problem

Existing methods for cleaning process water in paper recycling systems are hindered by biocides, which inhibit hydrolysis and acidification, leading to uncontrolled microbial growth and process disruptions, particularly in anaerobic cleaning steps.

Innovation Solution

A method involving pre-acidification with saccharide-splitting enzymes and maintaining a pH of 8.0 or lower, combined with anaerobic cleaning, effectively breaks down impurities without complex biocide concentration control, using enzymes like amylases, cellulases, and lipases to enhance hydrolysis and acidification.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If biocide is added to process water to prevent uncontrolled microbial growth, then microbial growth is controlled, but hydrolysis and acidification are inhibited

Engineering Contradiction:

Improvecontrol of microbial growthVSAvoidhydrolysis and acidification efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The process is divided into two distinct stages: a pre-acidification stage where hydrolysis and acidification occur without biocide, followed by an anaerobic cleaning stage where biocide is present. This segmentation allows each stage to function optimally without interference from biocide inhibition.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The pre-acidification step is performed before the anaerobic cleaning step, preparing the process water by breaking down organic impurities and adjusting pH in advance. This preliminary action removes the burden of hydrolysis inhibition that would otherwise occur during the main cleaning process.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If pre-acidification is performed to break down organic impurities, then cleaning effectiveness is improved, but process complexity increases

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidprocess complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The pre-acidification step and anaerobic cleaning step are combined into a single integrated process flow, where the output of the first step directly feeds into the second step. This merging eliminates the need for separate treatment systems and simplifies overall process control.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The pre-acidification step uses the process water itself as the medium for hydrolysis and acidification, without requiring external addition of complex chemicals or nutrients. The system leverages its own contents to perform the breakdown of organic impurities.

Inventive Principle:

Principle #25Self-service

3Productivity

If pH is maintained at 8.0 or lower during pre-acidification, then hydrolysis and acidification are enhanced, but process control difficulty increases

Engineering Contradiction:

Improvehydrolysis and acidification rateVSAvoidpH control difficulty

Core Design Contradiction:

ProductivityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent accepts that pH control may be challenging but turns this into a benefit by using the pre-acidification step to lower the pH of process water before it enters the anaerobic reactor. This ensures the anaerobic microorganisms receive water at an optimal pH level, improving overall process efficiency.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

Ensures effective and reliable hydrolysis and acidification, allowing for continuous process water cleaning in paper recycling systems, reducing the need for fresh water and minimizing process disruptions.

Implementation Method 1

at least some of the process water to be cleaned is subjected to hydrolysis and acidification in a pre-acidification step

Methodology Applied

Scientific EffectHydrolysis: Hydrolysis

Implementation Method 2

at least one saccharide-splitting enzyme is added to the process water before or during the at least one pre-acidification step

Methodology Applied

Scientific EffectEnzyme catalysis: Enzyme

Implementation Method 3

the process water thus treated is then brought into contact with anaerobic microorganisms in an anaerobic cleaning step in order to break down impurities in the process water

Methodology Applied

Scientific EffectAnaerobic digestion: Anaerobic Digestion

Implementation Method 4

the pH of the process water is set to 8.0 or lower at least during the at least one pre-acidification step and during the at least one anaerobic cleaning step

Methodology Applied

Scientific EffectpH control:

Data Source

PatentUS12365613B2Method for cleaning process water circulated in a paper recycling system using enzymes

Publication Date: 2025.07.22 MERI ENTSORGUNGSTECHN FUR DIE PAPIERIND

AI summary

The present invention relates to a method for cleaning process water circulated in a paper recycling system, comprising a process water treatment step, which comprises at least one pre-acidification step and at least one anaerobic cleaning step, wherein at least some of the process water to be cleaned is subjected to hydrolysis and acidification in the at least one pre-acidification step and the process water thus treated is then brought into contact with anaerobic microorganisms in the at least one anaerobic cleaning step in order to break down impurities in the process water, wherein at least one saccharide-splitting enzyme is added to the process water before or during the pre-acidification step, and the pH of the process water is set to 8.0 or lower at least during the at least one pre-acidification step and during the at least one anaerobic cleaning step.