Experiment was carried out in two parts to investigate the degradation profile of trimethoprim and sulphamethoxazole, antibacterial compounds in aqueous phase. In the first part of study, the effects of UV and TiO 2 on two antibiotics using the UV-water flow system (UVWFS) were examined. Obtained results revealed that trimethoprim and sulphamethoxazole pronounced 44 to 45% and 6 to 314% elevated rate of degradation in two TiO 2 doses, 0.05 and 0.1 g/l treatments with UV than only UV treatments

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... hich affords to draw a substantial conclusion that though both UV and TiO 2 have a crucial impact but the synergistic photocatalytic effects of the TiO 2 with UV attributes a rapid and higher degree of degradation of antibiotics compared to that of only UV at the same water flow rate. In this context, it may also be observed that effect of the dose of TiO 2 was very little in trimethoprim degradation but a significantly greater effects was revealed in sulphamethoxazole that indicating same number of TiO 2 molecules acted more favourably on higher number of sulphamethoxazole molecules than trimethoprim by photocatalytic activity which enhancing the rate of degradation reaction resulting in the rapid decrease of sulphamethoxazole concentration level in water. In second part of the study, three (15, 42 and 80 cc/min) water flow rates were employed using UVWFS maintaining same UV and TiO 2 dose 0.1 g/l to ascertain the effect of water flow rate in the antibiotic transformation process. The degradation efficiency in 80 cc/min water flow treatment was 113 and 61% higher in trimethoprim and 103 and 51% higher in sulphamethoxazole compared to that of 15 and 42 cc/min water flow treatments, respectively which clearly indicated that the rate of water flow is a paramount important, largely influencing the photocatalysis reaction process of TiO 2 and UV with antibiotics in water medium possibly enhancing movement velocity of their molecules. Besides it, trimethoprim degraded rapidly over sulphamethoxazole which might be inferred that higher water flow substantially increases the rate of oxidation and photocatalytic transformation of trimethoprim over sulphamethoxazole in the presence of TiO 2 and UV. A significant treatment dependence response was observed in the sulphamethoxazole concentration ranged from 0.0 to 887.87 μg/l (ANOVA, P < 0.05). The mean concentration was minimum in UV+T 0.1 (168.58 μg/l) and maximum in C (783.62 μg/l) (Figure 4b) . Though, no remarkable difference was found in the degradation efficiency (4.46 -70.46 Vol. 3, No. 2 Modern Applied Science 6 μg/l/h) between UV (17.83 μg/l/h) and UV+T 0.05 (18.15 μg/l/h) but UV+T 0.1 exhibited significantly greater value (288 -1500%) over the treatments and control (Figure 6a) . As time progressed UV and UV+T 0.05 also showed a similar response in the sulphamethoxazole concentration reduction whereas a sharp concentration declining trend was found in case of UV+T 0.1 during the study period (Figure 4b) . Irrespective of treatment, the concentration reduction of sulphamethoxazole was more rapid compared to that of the trimethoprim in each respective treatment. Experiment -II The trimethoprim content of water varied (0.0-1020.8 μg/l) significantly (ANOVA; P < 0.05) in all the treatments employed. The mean value was maximum (549.35 μg/l) in the UVT 15 exhibiting the following order of variations: UVT 15 > UVT 42 > UVT 80 (Figure 5a ). The degradation efficiency of trimethoprim in UVT 80 was 113 and 61% higher compared to that of UVT 15 and UVT 42 , respectively (Figure 6b ). The concentration gradually decreased with time and reached at zero concentration level at the period of 36 th and 48 th h in UVT 80 and UVT 42 , respectively, whereas UVT 15 showed a substantial concentration until 48 th h (Figure 5a ). The concentration of sulphamethoxazole registered a significant treatment dependent response throughout the period of study (ANOVA, p > 0.05). The mean concentration 168.03 μg/l in UVT 80 was lower (68 -150%) compared to that of UVT 15 and UVT 42 (Figure 5b) . A marked difference in degradation efficiency was found in three treatments showing the following order of variation: UVT 15 > UVT 42 > UVT 80 (Figure 6b ). Though temporal responses were similar but a sharp declining trend in the concentration of sulphamethoxazole was encountered unlike trimethoprim in all treatments and obtained zero concentration at 36 th and 48 th h by UVT 80 and UVT 42, respectively ( Figure 5b ) .