1. What is hazardous wastewater reuse? What is hazardous waste?

Hazardous waste is waste containing toxic, radioactive, infectious, flammable, explosive, corrosive, poisonous or other hazardous properties (according to  Law on Environmental Protection 2014 No. 55/2014/QH13)

So hazardous wastewater is wastewater collected from production processes that create hazardous waste, or other processes that contain high concentrations of toxic or hazardous substances.

Reusing hazardous wastewater is treating wastewater to meet discharge and usage standards. Depending on the purpose of water use, wastewater after treatment must meet the required standards.

2. Some manufacturing industries that generate hazardous waste and wastewater

• Exploration, exploitation and processing of minerals, oil and gas and coal.
• Inorganic chemical production.
• Waste from organic chemical production.
• Metallurgy
• Production, formulation, supply and use of coating products (paints, varnishes, vitreous enamels), adhesives, sealants and printing inks
• Leather, fur and textile processing
• Waste oil, waste from liquid fuels, waste from organic solvents, refrigerants and detergents

A typical example is at the Bac Ninh liquid waste treatment plant, Vietnam. The wastewater here is collected from factories producing electronic components and circuit boards. The composition of substances is very high, the input water quality index is as follows:

The wastewater here not only has a high TDS index, but also has a very high content of organic solvents obtained from the process of washing circuit boards and polishing solder joints. Because it is a solvent, the wastewater is very difficult to treat.

The hazardous wastewater treatment solution submitted by TVTS to the investor has been assessed and approved after many times of defending the technology plan before the assessment council. The council was established from professors and leading experts in the water and environment industry in Vietnam.

3. Hazardous wastewater reuse solution at TVTS

Design, construct, install, complete and operate stably, hand over the system to the investor. The hazardous wastewater reuse system is a combination of the following processes:

• Primary treatment
• Anaerobic biodigesters/tanks
• Aerobic biodigesters/tanks
• 1-stage, 2-stage and 3-stage Fentoning
• High silver oxidation process
• DAF flotation technology
• Sludge press and sludge reuse
• RO ROCHEM reverse osmosis membrane technology
• SPRO spiral membrane technology

Currently, the system is operating stably, the wastewater after treatment reaches a recovery rate of 65 – 80% and is reused for cooling towers, irrigation, and other sanitation activities.

The water treatment system – reuse of hazardous wastewater at the factory is creating high investment efficiency.

4. Some features of the waste treatment plant that we have implemented

This is one of the most advanced factories in the country when applying Korean incinerator technology, producing an electrical capacity of more than 6MW from 180 tons of incinerated waste. Electronic circuit board recycling technology, reusing wastewater for turbine cooling. In particular, this is the first factory to use the most advanced septic tank sludge treatment technology and the most complete treatment stages in Vietnam.

The technology was demoed live for more than 9 months at the factory and was assessed by the GS Council of the Northern Environmental Institute. This factory focuses on collecting and treating hazardous solid and liquid waste from large industrial zones in the north such as Yen Phong, Yen Binh, Que Vo, Hoa Lac, etc.