Microbiological overview and hazards

Microbiological overview and hazards

Microorganisms are all small, single-celled or multi-celled with simple individual structures, and even lower organisms without cell structure.

According to the ability of cells to utilize carbonaceous materials from different sources, bacteria can be divided into autotrophic and heterotrophic bacteria

The main bacteria in industrial water, especially the circulating cooling water system, are heterotrophic bacteria, iron bacteria, and sulfate-reducing bacteria; the algae include cyanobacteria, green algae and diatoms

Table 7-1 Microorganisms in the open circulating cooling water system

(1) Heterotrophic bacteria

Heterotrophic bacteria is a general term for a type of bacteria.

(2) Iron bacteria

Iron bacteria are a kind of aerobic heterotrophic bacteria, which can also grow in systems with an air content of less than 0.

All iron bacteria with the following physiological characteristics are typical iron bacteria: they can play a catalytic role in the oxidation of ferrous oxide into high-valent compounds; they can use the energy released during iron oxidation to meet their life needs

4FeCO ₄ +O ₂ +6H ₂ O→4Fe(OH) ₄ +4CO ₂ +energy

The reaction produces energy and high-speed iron maintains its energy metabolism

Iron bacteria are the most common type of bacteria in contact with water

2Fe ²⁺ +(x+2)H ₂ O+1/2O ₂ →Fe ₂ O ₄ ·xH ₂ O+4H ⁺ +energy

In this way, nodules composed of bacterial cells and iron hydroxide are formed, making it difficult for the dissolved oxygen in the water stream to diffuse to the bottom metal surface

Iron bacteria also exist in large quantities in the oilfield water injection system.

(3) Sulfate reducing bacteria

Sulfate-reducing bacteria are bacteria that reduce sulfate to sulfide under anaerobic conditions and use organic matter as nutrition

Desulfovibrio is a gram-negative Campylobacter, with an S-shaped or spiral shape, about 2 μm in length, and a flagellum with a thickness of about 1000 nm

The growth of sulfate-reducing bacteria is restricted by environmental factors, and its growth temperature is divided into two types, medium-temperature type and high-temperature type, depending on the type of bacteria

Like iron bacteria, sulfate-reducing bacteria can cause serious corrosion problems

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