Effects of microbubble pre-ozonation time and pH on trihalomethanes and haloacetic acids formation in pilot-scale tropical peat water treatments for drinking water purposes

• Published in: The Science of the total environment 2020-12, Vol.747, p.141540-141540, Article 141540
• Main Authors: Qadafi, Muammar, Notodarmojo, Suprihanto, Zevi, Yuniati
• Format: Article
• Language: English
• Subjects: Haloacetic acids; Microbubbles; Pre-ozonation; Trihalomethanes; Tropical peat water
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.141540

The high concentrations of dissolved organic matter (DOM), chloride, and bromide in tropical peat water have a significant impact on the formation of carcinogenic disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs), especially during the chlorination process. Therefore, other pretreatment methods to effectively remove these harmful substances in the water during treatment are needed. The aim of this study was to determine the effects of microbubble pre-ozonation pH on the reduction of THM4 and HAA5 formed during the peat water treatment process and to determine the best conditions for microbubble pre-ozonation to reduce the formation of these two classes of DBPs. The microbubble pre-ozonation was conducted at a pH of 5.5, 7, and 8.5. Furthermore, the primary treatments applied after this pretreatment were coagulation and activated carbon adsorption before post-chlorine disinfection. The coagulation process using aluminum sulfate and activated carbon adsorption succeeded in reducing the formation of THM4 after chlorination, to a level below USEPA standards, but the concentration of HAA5 was still high. However, the use of microbubble pre-ozonation significantly reduced the formation of both classes of compounds during the chlorination process of the peat water. Also, the concentration of THM4 increased during the pre-ozonation process in all pH conditions, but HAA5 decreased except in alkaline state. Furthermore, the ideal conditions for microbubble pre-ozonation on peat water were at pH 7 (neutral) after 30 min, with the total THM4 concentration at 33.73 ± 0.40 μg/L, and that of HAA5 at 49.89 ± 0.09 μg/L, falling below the USEPA standard. [Display omitted] •Ozone microbubble was injected into peat water as a pre-treatment.•Microbubble pre-ozonation reduced HAA5 formation but increased THM4 formation.•pH 7 shows better performance of mitigation THM4 and HAA5 formation in peat water treatments.•Brominated THM4 and HAA5 dominated THM4 and HAA5 formation in peat water treatments.