As a fast-emerging industry in developing countries, the automotive and auto components industry needs to comply to environmental regulations and use wastewater treatment systems as part of their production processes.
It is estimated that water consumption along the life cycles of cars ranges from 52 to 83 m3/car, of which more than 95% is consumed in the production phase, mainly resulting from producing iron, steel, precious metals, and polymers. A wastewater treatment plant for these effluents is one of the key parts in making the automotive industry become more sustainable.
In this article, we will introduce the most common challenges in treating automotive industry wastewater and the most efficient methods to reach a Zero Liquid Discharge system.
What are the Characteristics of the Automotive Industry Wastewater?
The automobile industry uses water for washing, rinsing and painting. Some commonly found contaminants in the effluents are metals, oils, grease, dyestuff, detergents, chromium, phosphates, paint residuals, and many more.
The wastewater contains heavy metals, oil & grease, organic and inorganic pollutants and also high levels of COD. For these reasons, the effluent treatment in the auto components industry is a real challenge.
Some of the most common pollutants as found in the wastewater across various types of companies within this industry are:
Fats, Oil, Grease, and Hydrocarbons: usually pre-treated at source;
Heavy Metals: the wastewater generated in the surface treatment processes is highly polluted and must be treated before disposal;
Toxic chemical substances: the wastewater from car paint workshops and painting processes needs to be carefully treated before discharge into the sewer system;
Flammable Liquids: Flammable or volatile liquids can cause fires or explosions in the sewerage systems and therefore they cannot be present in discharge water;
Suspended Solids (SS): Suspended Solids can cause silting within sewers and pump stations, leading to blockages and overflows. Pre-treatment to separate solids from the wastewater is required before water is discharged to sewer;
Coolant and Radiator Fluids: Coolant and radiator fluid have a high concentration of hydrocarbons (glycol) and therefore has to be removed from the wastewater before entering the sewer;
Car or equipment washes: Waste water from any vehicle wash or equipment wash facilities contain suspended solids and hydrocarbons and therefore need oil water separator for pre-treatment;
Wastewater Treatment Solutions in the Automotive Industry
As in most sectors, the effluents and wastewaters from the automotive industry must be treated before being released into the environment.
Installing a waste water treatment plant becomes a legal requisite for the companies operating in the car industry. The Effluent Treatment Plants play a major role in eliminating the pollutants and contaminants present in the water to an acceptable level before releasing it in the sewer system.
For the automotive industry and auto components sector the main wastewater treatment solutions include:
Reverse Osmosis Plant, such as REWATER
Evaporation, such as EVADEST
Crystallization, such as SOLIDEST
Heavy Metal Removal Systems
All these solutions can be combined to reach the requirements of a Zero Liquid Discharge system.
Effluent Treatment Plant Process Design for Automotive Industry
The effluent treatment plant for the automotive industry requires various stages for achieving Zero Liquid Discharge, such as pre-treatment, primary treatment, secondary treatment and tertiary treatment when required.
a. Pre-treatment: the pre-treatment process involves initial screening or grit chamber to remove floatable solids in raw effluent. It also removes floatable oil and grease with the help of a custom designed trap.
b. Primary Treatment: The pre-treated wastewater enters into a primary tank where chemical process like coagulation, flocculation and neutralization takes place. This process can be also performed by an Electrocoagulation equipment, such as PREDEST.
In this process the heavy solids settle down at the bottom and remaining wastewater is directed to next level of treatment. The sludge form this process can be dewatered by using a plate and frame filter press;
c. Secondary Treatment: in the second stage of the treatment process, a vacuum evaporator and crystallizer can be used to produce a high-quality distillate from the pre-treated wastewater. The product from the evaporator can be furtherly treated, while the concentrate can be collected and sent to a disposal plant.
If the energy consumption requirements are strict and the wastewater flow is large, an MVR evaporator can be used instead of a heat pump evaporator, that allows up to 70% in savings of energy costs.
d. Tertiary Treatment: finally, the distillate can be polished and reach high purity levels by using an RO system. In this case the water can be reused in the automotive industry manufacturing process.
Treating and Recycling Wastewater in the Automotive Industry
Treating and recycling wastewater produced by the automotive industry is possible, but requires a careful design for the effluent treatment plant.
It is estimated that water consumption along the life cycles of cars can reach 83 m3/car, thus car manufactures should reduce as much as possible their wastewater and recycle it in their production lines. Thanks to modern technologies, it is finally possible to recycle from 75 to 80% of the water from the wastewater from the auto components industry.
As mentioned earlier, the combination of Evaporation and Membrane filtration technology can produce a treated effluent that can be reused in the production line for the automotive parts manufacturer.
What is the Best Wastewater Treatment Method for the Automotive Industry and Auto Parts Suppliers?
The best wastewater treatment method for the automotive industry and auto parts suppliers includes physico- chemical, Reverse Osmosis, Evaporation, and Crystallization technologies.
Our company, YASA ET designed various effluent treatment plants for companies in the automotive sector and solved their wastewater treatment problems.
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Water Footprint of European Cars: Potential Impacts of Water Consumption along Automobile Life Cycles | Environmental Science & Technology (acs.org)