The treatment of painting wastewater can be a real challenge for some companies, especially in the chemical, plastic and automobile industry that need to use high quantity of paint and surrogates for colouring, coating and surface treatment processes.
As a result of this process, wastewaters containing raw materials and auxiliary products used during the cleaning step are produced. For this reason, these manufacturing industries produce wastewater containing high chemical oxygen demand and turbidity, besides organic matter, suspended solids, and heavy metals that cause enormous environmental damages.
In this article we will examine the best treatment solutions and systems for these wastewaters.
What Are Wastewaters from Painting Processes?
In some manufacturing processes, such as in the automobile industry, surface treatment and painting produce variable amounts of wastewater.
Painting processes wastewater contains huge amounts of toxic chemical substances, bio refractory compounds, pigments, and microorganisms. So, advanced treatment requirement is available to dispose of color, microorganisms, and chemical oxygen demand (COD).
The high organic content of wastewater causes serious environmental challenges and contamination for the living organisms and the ecosystem in the receiver media unless it is treated adequately. In this context, the treatment process to be implemented should be preferred in such a way as to give the least damage to the environment.
Main Challenges in the Treatment of Painting Wastewater
The treatment of painting wastewater is problematic and costly for many enterprises since its treatment requires a sophisticated project setup and high-tech equipment designs.
Normally, wastewater discharged from the painting department is characterized by the high contents of organic compounds. The mean values of the biological oxygen demand (BOD) usually range from 2,500 to 6,000 mg/I. While the chemical oxygen demand (COD) values typically range from 20,000 to 60,000 mg/l.
The average phenol concentration is also a factor to consider in painting wastewater. In this case, the most measured value in our labs is about 2.6 mg/l.
Since an accurate chemical analysis is a must have to design an effective treatment system, we offer this service in our laboratory. You can get in touch with us to book a test for your wastewater.
Discharge Parameters to Pay Attention to for Painting Processes Wastewaters Disposal
In recent years regulations governing the discharge of industrial wastewaters, including paint wastewaters, have become more stringent all around the world.
Now, companies must take any measures necessary to ensure the safe collection and disposal of wastewater. As a result, businesses need to treat these effluents before discharging them to sewers.
The most important parameters to consider in painting and coating wastewater treatment:
Chemical Oxygen Demand (COD): Measure the amount of oxygen that is needed to oxidize soluble and particulate organic matter in water;
Biological Oxygen Demand (BOD): Biological method used for the measurement of the total amount of dissolved oxygen (DO) used by microbes in the biological process of metabolizing organic molecules present in water;
Total Dissolved Solids (TDS) and Total Suspended Solids (TSS): particles that are either dissolved or suspended in the wastewater;
Phenolic micropollutants: chlorates, Bromo, nitro, and alkyl are the most common phenols. With its toxicity and persistence in the environment, these phenolic compounds are considered dangerous substances.
Depending on the country, the discharge limits for paint rinsing and polishing wastewater can vary, but the most cost-efficient wastewater treatment methods remain the same.
How to Treat Wastewater from Painting Processes and Surface Treatments?
Wastewater from painting processes and surface treatment can be treated by different technologies.
The most common technologies are:
Ozonation combined with hydrogen peroxide;
Electrocoagulation and/or Electrooxidation, combined with evaporation.
In many studies, the physicochemical techniques produce a large amount of sludge making it difficult for disposal while biological treatment techniques are difficult to maintain because of the uncertainties in the chemical compositions of the paint wastewater.
Advanced oxidation processes are emerging as common treatment technology among the chemical methods for reducing the toxicity of the various components of the paint wastewater with reduced sludge quantity.
In addition, Electrocoagulation and Electrooxidation are becoming more and more popular methods for the primary treatment of these wastewater.
As we can all understand, an appropriate treatment system for paint rinsing wastewaters can cut down discharge volumes and cost for enterprises.
What Is the Best Wastewater Treatment Technology for Painting Processes Wastewaters?
Treatment and disposal options applicable to painting processes wastewater mainly depend on the type and volume of wastewater, so the treatment solutions for a specific fluid are often difficult to determine without prior testing.
Often the best solution relies on the combination of treatment methods, so to efficiently remove pollutants from paint wastewaters and reuse the water in the production lines.
Electrocoagulation, Electro-oxidation, and Evaporation Technologies for Painting Department Wastewaters Treatment
The most efficient treatment technology for painting department wastewaters treatment often relies upon the combination of different methods, such as Electrocoagulation, Electro-oxidation, and Evaporation.
In our experience, the combination of our electrocoagulation equipment and wastewater vacuum evaporators gave the best treatment results for coating and surface washing effluents. This equipment can be followed by a membrane treatment system for further polishing.
Electrocoagulation and Electrooxidation can effectively separate the pollutants and coagulate them from the water body. These methods can separate the most resistant contaminants by using electrochemical reactions. In case the organic content of painting wastewaters is too high, the Electrooxidation technology should be preferred since it can break down and remove those elements.
An electrocoagulation equipment followed by a filter press can reduce COD in paint washing wastewaters by 75% on average, and greatly increase the efficiency of vacuum evaporators.
The contained costs of this technology, combined with the minimal use of chemicals, make it a good choice for these wastewater treatment applications. More information about this technology can be found here: Electrocoagulation System by YASA ET.
Now you can also test these technologies with our test equipment, click here for more info.
Painting Workshops Wastewater Treatment with Vacuum Evaporators
Wastewater evaporation has become an effective method for removing contaminants and concentrating liquid waste from painting workshops.
This technology can remove salts, heavy metals, and hazardous materials, reducing COD, BOD, and TSS very effectively. In painting wastewater treatment, evaporators can reduce COD levels to discharge limits, and the recovery rate can reach up to 85% with the correct pre-treatment setup.
A vacuum evaporation equipment, such as EVADEST or SOLIDEST, uses almost no chemicals for cleaning wastewater and has much lower energy consumption when compared to other types of products on the market.
The last improvement brought by MVR evaporators makes this technology the preferred choice for large volumes of wastewater.
The Most Cost-Effective Treatment Method For Painting Wastewater
Overall, chemical methods are the most suitable treatment technology for painting wastewater, followed by electrochemical and evaporation methods.
Instead, electrocoagulation and electrooxidation are among the most cost-effective solution to break down contaminants and reduce pollutants, but the effluent requires further treatment either with evaporation or membrane filtration methods. For this reason, electrocoagulation and electrooxidation are a great choice for pre-treatment or for improving the treatment effects of evaporators and membrane equipment on paint wastewater treatment applications.
Finally, membrane systems are effective in further separating the pollutants from the waste water, but the operating costs could be very high since the membranes need to be frequently replaced.
What Is The Best Treatment Technology For Painting and Coating Processes Wastewaters?
The best system for the treatment of wastewater from paint workshops and coating processes combines chemical, evaporative, and membrane filtration technologies.
In the past, as YASA ET we built systems for the treatment of painting wastewater using PREDEST electrocoagulation and electro-oxidation equipment and EVADEST vacuum evaporator.
For more information about our treatment technologies, you can get in touch at:
🌐 www.yashahuanjing.cn (中文）
📱 +86 136 3643 1077
YASA ET official online store > click here
Investigation of Environmental-friendly Technology for a Paint Industry Wastewater Plant in Turkey (researchgate.net)
Treatment of Wastewater Coming from Painting Processes: Application of Conventional and Advanced Oxidation Technologies: Ozone: Science & Engineering: Vol 27, No 4 (tandfonline.com)
Sustainable treatment of paint industry wastewater: Current techniques and challenges - ScienceDirect