# Recent Developments and Emerging Trends in Paint Industry Wastewater Treatment Methods
## 3 Paint Industry Wastewater Treatment Methods
### Combination of Treatment Processes  
For higher COD removal from paint industry wastewater, a combination of the various treatment methods has proven to be successful [6; 30; 32; 34] (Table 5). Regarding electro-coagulation improvement and obtaining an effluent of suitable quality for agricultural purposes, a combined method of radiation, coagulation, and adsorption with granular activated carbon has been used to treat wastewater from the paint industry [29].  
For the decomposition of the pollutants short-lived reactive species, which are produced during the radiolysis of water should be used. Ionizing radiation is an effective tool for the degradation of numerous compounds and the inactivation of microorganisms. The effectivity of the process depends on the type of energy, dose rate, and absorbed dose [79; 80; 81]. [PERSON] et al. [29] studied the efficiency of the combined process of radiation and coagulation with Al\({}_{2}\)(SO\({}_{4}\))\({}_{3}\) and adsorption using granular activated carbon for paint industry effluents and its reuse for different purposes. Radiation at 2 kilograys (kGy)proved to be sufficient for the complete elimination of Gram-positive bacteria. However, it was not enough to reduce COD and BOD values. Therefore, a higher radiation dose (10 kGy) was tested and a 60% COD and 80% BOD removal was obtained. However, the obtained values for COD and BOD were insufficient to meet the guideline for effluent discharge. For this reason, coagulation with Al2(SO4)3 was applied to improve the treated water quality. The combination improved COD removal by up to 92% and BOD removal by up to 98.5% [29]. Aggregates were removed by sedimentation and filtration, and analysis of sulfate ions from the coagulant were conducted by standard methods for water and wastewater treatment [29].  
The coagulation-flocculation process in combination with a biological process, using an aerobic feed batch operation, has also been shown to be highly effective in the treatment of paint manufacturing effluents [27]. COD and BOD removal was 96% and 92.5%, respectively. In comparison with the method developed by [PERSON] et al. [10] (85% for COD and 90% for BOD), using a chemical/physical treatment followed by an aeration and filtration process through a palm hemp agro fiber filter media, the aerobic feed batch operation produced better results.  
A multilevel contact oxidation system was designed [82] for automobile painting wastewater treatment. By producing activated sludge and optimizing the method conditions, the system could effectively decrease the COD of the paint industry effluents. Under steady process conditions, the final removal of COD was 84% and SS 82.5% [82].  
Hybrid electro-thermochemical wastewater technology was studied for the treatment of paint industry wastewater [6]. Treatment of industrial wastewater was carried out with modifications of additives (organic and inorganic) during the treatment procedure. The effect of both additives on the pollutant removal efficiency was studied in two different potential settings resulting in a variety of treated water samples (Figure 5). Treatment efficiency was monitored using the six most representative analytes as markers. It was found that the removal of the selected organic pollutants, in some cases, was higher than 90%, indicating options for further technology upgrades [6].