Core Descriptions of Different Wastewater Treatment Processes

1. Physical Treatment Processes

The core is to separate pollutants using physical actions without changing their chemical properties.

• Grilles/Screens: Acting like "wastewater sieves", they filter out large floating substances (such as plastic bags and tree branches) from water, and are the first step in pretreatment for all processes.

• Sedimentation/Clarification: It allows suspended solids (such as sediment) in water to settle by gravity, which is suitable for removing visible impurities in water and is commonly used at the front end of sewage treatment plants.

• Dissolved Air Flotation (DAF): Bubbles are injected into water to adsorb tiny suspended solids (such as oil droplets and algae) and bring them to the water surface for scraping. It is specially used to treat oil-containing wastewater (such as catering and oilfield wastewater).

2. Chemical Treatment Processes

They destroy or precipitate pollutants through chemical reactions, and are suitable for industrial wastewater that is difficult to biodegrade.• Coagulation/Flocculation: Chemical agents (such as  ECH-701 complexing agent) are added to make tiny suspended solids "clump together" and become larger, which are then removed through sedimentation, and this can improve the efficiency of subsequent treatment.

• Neutralization: Alkali or acid (such as ECH-503 complexing agent and  ECH-107 complexing agent) is added to acidic or alkaline wastewater to adjust the pH value to neutral, so as to avoid equipment corrosion or impact on biological treatment.

• Oxidation-Reduction: Strong oxidants (such as  ECH-98 complexing agent ) are used to destroy toxic organic substances (such as pesticides and dyes). It is often used for the pretreatment of high-concentration toxic industrial wastewater (such as printing and dyeing and chemical wastewater).

3. Biological Treatment Processes

They use microorganisms to decompose pollutants (converting them into CO₂ and water), and are the core treatment link for domestic sewage and low-concentration industrial wastewater. They are divided into two categories: aerobic and anaerobic.

• Aerobic Biological Treatment: Under aerobic conditions, microorganisms "feed on" organic substances. Common processes include:

◦ Activated Sludge Process: Microorganisms form "sludge flocs", which fully mix and react with wastewater in an aeration tank. It has high treatment efficiency and is the mainstream process in urban sewage treatment plants.

◦ Biofilm Process: Microorganisms attach to the surface of fillers (such as filter media and biological rotating discs) to form a "film", and organic substances are decomposed when wastewater flows through. It is suitable for scenarios with small water volume (such as community sewage treatment).

• Anaerobic Biological Treatment: Under anaerobic conditions, microorganisms decompose organic substances and produce biogas (which can be recycled for energy). It is suitable for treating high-concentration organic wastewater (such as brewery and breeding farm wastewater), with low energy consumption but long treatment cycle.