Some types of wastewater in factories can be discharged directly into the industrial zone’s centralized treatment system, while others require more stringent wastewater treatment technologies and compliance with stricter effluent standards.

Types of wastewater in factories

Domestic wastewater

Domestic wastewater in factories is generated from daily activities such as restroom use, wastewater from canteens, and worker break rooms. This type of wastewater contains organic substances like grease, residues, leftover food, and detergents, along with microorganisms such as algae, yeast, bacteria, and viruses that can be harmful to humans. It often appears black or brown in color, caused by suspended particles and decomposing organic matter.

The volume of domestic wastewater varies across factories, depending on factors such as the number of workers, factory size, and whether on-site cooking facilities are present. Factories with kitchens generate domestic wastewater with higher organic content, requiring a more complex industrial wastewater treatment (IWT) system. The larger the factory and the greater the workforce, the higher the treatment capacity needed, necessitating a well-designed IWT system to ensure effective operation.

Contaminated industrial wastewater

This type of wastewater is generated during production and processing activities, machinery cleaning involving chemicals, and other industrial operations. Contaminated industrial wastewater often contains hazardous components such as heavy metals (copper, zinc, lead), toxic chemicals (acids, alkalis), and grease.

Industry	Specific pollution parameters
Food processing	Ammonia, animal and vegetable oils and grease
Fiber and textile production	Ammonia, color intensity, surfactants, cyanide, Cr6+, total Cr
Paper production	Ammonia, mineral oils, phenol, cyanide, sulfide, As, Hg, Pb, Cd, Cr6+, Cu, Zn, Ni, Mn, Fe, total alpha-radioactivity activity, etc.
Cosmetics, soap, and detergents	1,4-Dioxane, formaldehyde, surfactants
Pharmaceuticals and chemicals	Ammonia
Iron, steel, and casting	Ammonia, mineral oils, phenol, cyanide, sulfide, As, Hg, Pb, Cd, Cr6+, Cu, Zn, Ni, Mn, Fe, total alpha-radioactivity activity, etc.

Specific pollution parameters potentially arising from factories (Source: QCVN 40:2021/BTNMT)

The volume and quality of wastewater play a critical role in determining the environmental licensing process for factories. Certain industries, such as cosmetics, dye production, and paper manufacturing, produce wastewater with low quality and poor biodegradability, making environmental procedures more complex. On the other hand, industries that generate minimal or no contaminated wastewater, such as electronics assembly or the production of paper and plastic packaging focused on cutting and packing, have relatively simpler environmental requirements.

Additionally, the amount and level of pollution in wastewater depend significantly on the technology and production processes used. For instance, in the food industry, factories with raw material washing stages generate more wastewater compared to those focused solely on packaging. Similarly, factories utilizing advanced technology often produce less wastewater. Therefore, investors should accurately and thoroughly describe their production processes and technologies in their investment certificates. This allows regulatory agencies to precisely evaluate discharge levels, optimizing environmental procedures and saving costs and time.

Non-contaminated industrial wastewater

Non-contaminated wastewater is generated from activities such as machinery cooling, engine heat reduction, and steam condensation. This type of wastewater is characterized by low pollution levels, with contaminants mainly consisting of dust, machine oil, and mechanical residues.

Due to its relatively harmless nature, non-contaminated wastewater is typically easy to treat and can often be directly connected to centralized treatment systems in industrial zones. However, its discharge outlet must be separate from that of regular wastewater and must meet specific temperature limit requirements.

Wastewater treatment system requirements for factories in industrial zones

Each industrial zone (IZ) has specific requirements for wastewater treatment systems, depending on the type of industry and the scale of factory operations:

IZs with centralized treatment systems: Factories with wastewater meeting the discharge standards of the IZ can sign a contract to connect their output to the centralized treatment system. In this case, the factory is not required to build its own treatment system.
IZs without centralized treatment system or factories generating chemical wastewater: In IZs without centralized treatment system, or if a factory produces contaminated industrial wastewater with hazardous chemicals, heavy metals, or other pollutants beyond the capacity of the centralized system, the factory must construct its own treatment system. Wastewater must be treated to at least Column B standards under QCVN 40:2011/BTNMT before being discharged into the environment.

Currently, most IZs are equipped with modern, large-capacity centralized wastewater treatment systems to meet treatment needs and attract investors.