The core technical mechanism lies in the synergistic effect of stirring and reoxygenation: Stirring “exposes” the pollutants hidden in the sediment, while reoxygenation provides the “energy” and “tools” needed to degrade these pollutants. The synergistic pathway and pollutant transformation process are illustrated in the figure below:

 

1. The role of stirring: From a “closed system” to an “open system”

In static reoxygenation, oxygen can only act on the surface layer of the sediment. However, stirring achieves:

(1) Comprehensive exposure of pollutants in the sediment

Encased in deep-bottom sediments Black and odorous substances (such as FeS, organic acids, H₂S)   and Nutrient salts (such as NH₄⁺, PO₄³⁻)   All of it is released into the water body, breaking the “encapsulation” state of pollutants held by the sediment.

Separate the entire system into “water-cement” layers. Closed/Semi-closed system , transforming into a Open reaction system with homogeneous mixing 。

(2) A dramatic increase in the reaction contact area

Stirring breaks down large chunks of sediment into countless tiny particles, ensuring thorough mixing of the slurry. This increases... Pollutants, Microorganisms, and Oxygen The increased contact area causes the rates of subsequent chemical and biological reactions to rise exponentially.

 

2. Coordinated advancement of the reaction phase

In the homogeneous and highly efficient reaction environment created by stirring, various reactions triggered by reoxygenation occur synchronously and rapidly throughout the entire system.

Phase 1: Chemical Oxidation (Rapid Odor Removal and Blackness Elimination)

Stirring rapidly releases FeS and H₂S from deep within the sediment, allowing them to come into full contact with oxygen.

1) Instant deodorization H₂S + 2O₂ → SO₄²⁻ + 2H⁺. A large amount of H₂S is rapidly oxidized into odorless sulfate ions, causing the malodorous smell to drop sharply within a short period of time.

2) Rapid black removal 4FeS + 3O₂ + 6H₂O → 4FeOOH (yellow-brown) + 4S. The black FeS is completely and rapidly transformed into yellow-brown FeOOH. The color of the sediment undergoes a change. Fundamental transformation 。

Phase 2: Aerobic Biodegradation (the Core Purification Process)

Stirring converts solid and adsorbed organic substances into a suspended state, greatly enhancing biodegradation.

1) Complete mineralization of organic matter

The large-molecule organic substances originally fixed in the sediment are stirred, broken down, and released, making them more readily accessible for microbial enzymes to degrade. Aerobic heterotrophic bacteria obtain ample “food” (organic matter) and “oxygen” (energy), enabling them to rapidly carry out metabolism: Organic matter + O₂ → CO₂ + H₂O + Energy + New cells. As a result, the sediment undergoes a transformation from “organic” to “inorganic.”

2) Enhancement of nitrification

The released ammonium nitrogen (NH₄⁺) is thoroughly mixed with oxygen and nitrifying bacteria, and efficiently oxidized to nitrate (NO₃⁻): NH₄⁺ → NO₂⁻ → NO₃⁻.

Phase 3: Reconfiguration and Stabilization of the Ecosystem

Under the combined effects of stirring and reoxygenation, the system undergoes a fundamental transformation.

1) Forced succession of microbial communities ：

From an anaerobic to an aerobic environment, inhibiting the original. Anaerobic microbial community, For Aerobic microorganisms Its reproduction has created optimal conditions (oxygen, food, and even distribution). Aerobic bacteria quickly became the dominant microbial community, and the ecosystem’s function has completely shifted from “pollutant production” to “pollutant purification.”

2) Stabilization of bottom sediment and formation of an oxidation layer ：

As organic matter is heavily consumed, the skeletal material of the sediment— Inorganic iron-aluminum oxides/hydroxides (such as FeOOH)   The relative proportion has increased significantly.

Once stirring stops, the heavier inorganic particles will gradually settle. Since most of the organic matter has been removed, the settled sludge has a denser structure.

Continuous reoxygenation will establish a robust layer on the surface of the newly formed sediment. Yellow-brown oxide layer The oxide layer further reduces the phosphorus content in water bodies due to its chemical stability and its ability to adsorb and immobilize pollutants such as phosphorus.

 

In summary, stir. It breaks through physical barriers, allowing pollutants in the sediment to fully dissolve. ; Reoxygenation It breaks through chemical and biological barriers, providing the dissolved oxygen necessary for purification. Together, these two factors enable...   Physical mixing → Chemical oxidation → Biodegradation   a chain reaction that, at a rate far exceeding natural processes, will transform ① aquatic bodies from Hypoxia 、 Black and smelly Transformation Aerobic 、 Clear water ② Sediment from The “black organic” state of anaerobic, reducing, and pollutant-producing conditions , transform into A stable “yellow-brown inorganic” state characterized by aerobic conditions, oxidation, and pollutant removal. 。