What are the main types of water treatment agents, and what are the differences between coagulants, corrosion inhibitors, and fungicides

In water treatment scenarios such as industrial circulating water, municipal sewage, pure water preparation, and wastewater reuse,Water treatment chemicalsIt is a key material for ensuring water quality meets standards and protecting the stable operation of equipment. According to their functional roles, they can be divided into multiple categories, among which coagulants, corrosion inhibitors, and fungicides have a wide range of applications, but their target of action, mechanism of action, and applicable scenarios differ significantly. Clarifying the classification and core differences of various chemicals is helpful for selecting appropriate types based on water quality conditions and optimizing water treatment operation plans.

1、 Common main classifications of water treatment agents

According to their functions in water bodies, commonly used water treatment agents can be divided into the following categories.

Coagulants: including inorganic coagulants and organic polymer coagulants, used for the aggregation and sedimentation of suspended solids and colloidal particles in water to achieve solid-liquid separation.

Corrosion inhibitor: commonly used in circulating cooling water systems to reduce the corrosion rate of metal pipelines, heat exchangers, and equipment inner walls.

Fungicides (antibacterial agents): divided into oxidizing and non oxidizing fungicides, they inhibit the reproduction of water microorganisms, control the growth of bacteria, algae, and biofouling.

Scale inhibitor: Through chelation and dispersion, it inhibits the formation of scale on calcium and magnesium ions, reducing scaling on the heat exchange surface.

PH regulator: an acid-base agent that regulates the acidity of water and creates a suitable reaction environment for other agents.

Decolorizing agent: for colored wastewater, it degrades or coagulates colored substances to reduce the color of the effluent.

Defoamer: eliminate foam generated during water treatment to avoid overflow and decrease of aeration efficiency.

Phosphorus removal agent and heavy metal capture agent: Targeting phosphorus and heavy metal ions in wastewater, pollutant removal is achieved through precipitation.

Different drugs can be added separately or combined according to water quality requirements, but some drugs have compatibility taboos, and the order and interval of addition need to be standardized and controlled.

2、 Comparison of the core mechanisms of action of coagulants, corrosion inhibitors, and fungicides

1. coagulants

Core objective: Remove colloids and suspended particles from water.

Small colloidal particles in water carry their own charges and are difficult to naturally precipitate due to long-term stable dispersion. After the addition of flocculants, the stable state of colloids is broken through methods such as electric neutralization, adsorption bridging, and net capture and sweeping, causing small particles to aggregate and form dense flocs. By relying on gravity settling, solid-liquid separation is completed in conjunction with sedimentation tanks and air flotation machines.

Common categories: Inorganic coagulants such as polyaluminum chloride and polyferric sulfate; Organic polymer flocculants such as polyacrylamide.

Typical applications: municipal sewage pretreatment, industrial wastewater settling, tap water purification, sludge dewatering process.

2. Corrosion inhibitor

Core objective: To protect metal equipment and mitigate corrosion.

Steel and copper materials in the circulating water system are prone to electrochemical corrosion due to long-term contact with water. Corrosion inhibitor molecules can adsorb onto metal surfaces, forming a protective film that isolates corrosive media such as dissolved oxygen and chloride ions from contact with the metal substrate in water, reducing the rate of corrosion reactions.

Common categories: organic phosphine corrosion inhibitors, imidazoline corrosion inhibitors, composite corrosion inhibitors, etc.

Typical applications: Central air conditioning circulating water, industrial cooling circulating water, boiler feedwater, closed circulation systems.

3. Fungicides

Core objective: Inhibit and kill water microorganisms, and control biofouling.

The water environment is prone to the growth of bacteria, algae, and fungi. The proliferation of microorganisms can form biofouling, block pipelines, and induce microbial corrosion. Fungicides act on microbial cell membranes and metabolic systems, inhibiting bacterial activity and reducing clay adhesion.

Common categories: oxidizing fungicides such as sodium hypochlorite and chlorine dioxide; Isothiazolone and quaternary ammonium salt non oxidizing fungicides.

Typical applications: algae killing with circulating cooling water, antibacterial treatment in reclaimed water systems, and microbial control in pure water pipelines.

3、 Summary of key differences between coagulants, corrosion inhibitors, and fungicides

The target audience is different. The target of flocculant action is suspended solids and colloidal particles; The target of corrosion inhibitor is the inner wall of metal equipment; The target of fungicides is microorganisms and algae in water bodies.

The functional location is different. Coagulants mainly play a role in sedimentation tanks and air flotation tanks, focusing on the separation of water pollutants; Corrosion inhibitors are continuously distributed in circulating water pipelines and heat exchangers, with a focus on equipment protection; Fungicides are distributed throughout the entire water system to control microbial growth from multiple perspectives.

The direction of water quality impact is different. After the addition of flocculants, floc sludge will be generated, which requires supporting sludge disposal facilities; The normal addition of corrosion inhibitors will not produce a large amount of sediment; Fungicides continuously inhibit microorganisms, and long-term use requires attention to the issue of microbial resistance. Different types of agents are often rotated.

The usage scenarios focus on different aspects. Wastewater pretreatment and sludge dewatering should prioritize the use of coagulants; Open and closed cycle cooling systems with corrosion inhibitors; The circulation pipeline that is prone to algae growth and mud growth requires regular addition of fungicides. Partial circulating water treatment systems require the simultaneous addition of corrosion inhibitors, bactericides, and scale inhibitors for coordinated operation, and generally do not share the same circulating system with coagulants.

The control logic for adding is different. The dosage of coagulants is often adjusted based on the concentration of suspended solids in the influent; Corrosion inhibitors need to continuously maintain an effective concentration in the water to ensure their film-forming effect; Fungicides often use a combination of continuous dosing and impact dosing.

4、 Simple reference for on-site application selection

Priority should be given to using coagulants for sewage purification and solid-liquid separation needs; Industrial circulating water is used to prevent pipeline corrosion and is combined with corrosion inhibitors; When there is a risk of mud, green discoloration, odor, or biological corrosion in the system, add disinfectant.

At the same time, it should be noted that the selection of chemicals cannot be generalized, and should be determined comprehensively based on water quality hardness, acidity and alkalinity, temperature, and types of water pollutants. When adding a compound, fully evaluate whether there is any mutual reaction between the drugs to avoid a decrease in efficacy and the formation of sediment.

summary

Water treatment chemicalsRich in categories, coagulants, corrosion inhibitors, and fungicides are the three basic chemicals in the field of water treatment. The difference between the three lies in their target functions: coagulants coagulate suspended solids to achieve solid-liquid separation, corrosion inhibitors rely on film formation to protect metal equipment, and fungicides inhibit the reproduction of microorganisms in water bodies. In practical engineering, selecting the type of chemicals according to the system's wastewater treatment or circulating cooling water conditions, and controlling the dosing plan reasonably can stabilize water quality indicators, reduce equipment failure probability, and improve the operational efficiency of the entire water treatment system.