EFFECT OF MICROBUBBLE OZONATION ON THE EXISTENCE OF TRIHALOMETHANES AND HALOACETIC ACIDS PRECURSORS IN PEAT WATER TREATMENT

• Main Author: Qadafi, Muammar
• Format: Dissertations
• Language: Indonesia
• Subjects: Teknik saniter dan perkotaan; teknik perlindungan lingkungan
• Online Access: https://digilib.itb.ac.id/gdl/view/56618
• Institution: Institut Teknologi Bandung

The need for water is increasing along with the times, but the quality of raw water sources continues to decline. Peat water is a water source that can be used by people living in peat swamp areas. On the other hand, peat water is rich in hydrophobic natural organic matter which is the main precursor to disinfection products (DBPs), compounds formed from the reaction between chlorine disinfectants and natural organic compounds (NOM). Several types of DBPs are carcinogenic, including trihalomethane-4 (THM4) and haloacetic acid-5 (HAA5). Based on literature studies, the ozonation process can reduce the formation of THM4 and HAA5 in water treatment containing high concentration of natural organic matter (NOM). This happens because ozone can change the hydrophobic NOM which is the main precursor of DBPs to a simpler hydrophilic NOM. The Hydrophilic NOM has smaller precursor properties to THM4 and HAA5 when compared to the hydrophobic NOM. In this study, a peat water treatment method using micro-bubble ozonation was developed both as a pre-treatment and post-treatment to optimize the efficiency of ozone transfer. The rotating flow type micro bubble generator is used to produce micro bubbles which have a diameter smaller than 100 µm. Coagulation using Al2SO4 and activated carbon adsorption was carried out to separate natural organic compounds present in peat water. The fractionation method using DAX-8, XAD-4, and IRA 958 resins was used to separate fractions of natural organic compounds in the form of hydrophobic acid (HPOA), transphilic (TPH), hydrophilic-charged (HPIC), and hydrophilic-neutral (HPIN) fractions as precursor fractions. THM4 and HAA5. The characteristics of organic compounds in the form of DOC, SUVA, and DBPs in the form of THM4 and HAA5 from ozonation of peat water using microbubbles were studied by varying the pH and time of ozonation. This is done to obtain the optimum conditions for microbubble ozonation to minimize the formation of hazardous disinfection products such as THM4 and HAA5 which are formed during final disinfection using chlorine (Ca (ClO) 2). Peat water contains high levels of natural organic compounds. This can be seen from the high concentration of dissolved organic carbon (DOC) which ranges from 22.20-56.6 mg/L. The presence of the HPOA fraction dominates the NOM in peat water at around 46.94%. This can also be seen from the high specific UV254 absorbance value (SUVA) (5.5-5.9 L/mg.m). HPOA fraction is the main precursor of DBPs and has the highest potential for the formation of THM4 and HAA5. The HPIC fraction has the lowest THM4 formation. On the other hand, the lowest HAA5 formation is in the HPIN fraction. Based on these results, further research is needed to change and remove the HPOA fraction that predominates in peat water into a hydrophilic fraction that has lower DBPs formation. The coagulation and activated carbon adsorption processes were successful in reducing the presence of the HPOA fraction of peat water significantly which led to a decrease in the total THM4 formation below USEPA standards (to 31.84 µg/L). On the other hand, the total formation of HAA5 was still above USEPA standards (85. 82 µg/L). The pre-ozonation process at pH 7 for 30 minutes followed by coagulation and activated carbon adsorption succeeded in reducing the total THM4 and HAA5 below USEPA standards (THM4: 33.79 µg/L, HAA5: 49.89 µg/L), while the optimum post-ozonation conditions occurred. at pH 5.5 with an ozonation time of 30 minutes (THM4: 71.02 µg/L, HAA5: 59.80 µg/L). The mechanism of decreasing total THM4 and HAA5 formation during the microbubble ozonation process at optimum conditions occurs due to the reduced formation of chlorine-based THM4 and HAA5 (C-THM4 and C-HAA5) which are the main DBPs formed after the chlorination process. This is due to the presence of the TPH fraction which is also a precursor to C-DBPs in addition to the HPOA fraction and was successfully reduced during the microbubble ozonation process under optimum conditions. On the other hand, the formation of HPIC and HPIN fractions during ozonation triggers the formation of bromine-based THM4 and HAA5 (B-THM4 and B-HAA5) after the chlorination process. Based on this fact, the microbubble ozonation process cannot be carried out for too long as it triggers the formation of B-DBPs. The pseudo-second-order kinetics equation can be used to model the formation of THM4 and HAA5 during the pre-ozonation and post-ozonation processes under optimum conditions. The pseudo-second-order equation has a fairly good correlation (close to 98%) on the formation of THM4 and HAA5 during the pre-ozonation and post-ozonation process. Although, the pre-ozonation process has a smaller correlation for certain HAA5 compounds.