Sludge Oxidation and Flocculation for Solids Reduction
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Solution Overview
Problem
Biogas plants face challenges in dewatering anaerobically digested organic matter, resulting in high suspended solids in reject water, which complicates subsequent ammonia stripping processes and increases waste treatment costs at municipal wastewater treatment plants.
Innovation Solution
A method that adjusts an acidic slurry mixture to alkaline pH using an oxidizing agent and then adds a flocculating polymer, allowing for efficient precipitation and separation of suspended solids, reducing their content in the liquid fraction, even when the pH is increased above 10.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If mechanical dewatering is performed on digested material, then water separation is achieved, but suspended solids remain high in the reject water
Solution Approach 1:
The patent applies preliminary chemical treatment (oxidation with hydrogen peroxide and acidification) to the sludge before mechanical dewatering. This pre-treatment modifies the sludge properties to improve subsequent separation efficiency and reduce suspended solids in the reject water.
Solution Approach 2:
The patent changes key parameters including pH (adjusted to below 7 using acid), oxidation state (using hydrogen peroxide), and adds flocculating agents. These parameter changes transform the sludge characteristics to enable better dewatering performance and lower suspended solids content in the liquid phase.
2Productivity
If pH is increased above 10 for ammonia stripping, then nitrogen removal is improved, but suspended solids precipitate and cause problems
Solution Approach 1:
The patent performs preliminary removal of suspended solids through chemical treatment and dewatering before the ammonia stripping process. By eliminating the solid-containing fraction in advance, the subsequent pH increase to above 10 for ammonia stripping does not cause problematic solid precipitation.
Solution Approach 2:
The patent extracts and removes the problematic suspended solids fraction from the sludge through chemical precipitation and dewatering operations. This separated solid fraction is removed from the liquid stream that will subsequently undergo ammonia stripping at high pH.
3Reliability
If oxidizing agent is added to acidic slurry, then hygienization and COD reduction are improved, but process complexity increases
Solution Approach 1:
The patent combines multiple functions into integrated process steps: acidification and oxidation are performed together in the same acidic slurry, and flocculation is added to the same treatment train. This combined approach achieves hygienization, COD reduction, and suspended solids removal through a unified process rather than separate sequential operations.
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 method effectively reduces suspended solids in reject water, preventing unwanted precipitation during ammonia stripping and improving COD and phosphorous reduction, thereby optimizing waste treatment processes and reducing costs.
Implementation Method 1
adding an oxidizing agent to the acidic slurry and allowing to react
Implementation Method 2
adding a flocculating polymer to the slurry obtained in c), wherein the polymer flocculates the suspended solids
Implementation Method 3
the suspended solids are then precipitating at a pH of 8 and above. As the polymer is added to the slurry mixture after the adjustment of pH toy 8, the polymer flocculates the suspended solids and the formed precipitated solids are then removed by fractioning of solids from liquid
Data Source
AI summary
The present invention relates to a method of treating a slurry comprising digested organic material, which comprises the steps of: a) obtaining an acidic slurry at a pH of below 7, b) adding an oxidizing agent to the acidic slurry and allowing to react, c) adding an alkaline compound to the slurry obtained in b) to obtain a pH ≥ 8, d) adding a flocculating polymer to the slurry obtained in c), e) separating the slurry obtained in d).