RESUMO
The degradation of methamidophos in pure bi-distilled water (with initial concentration 5 mg L(-1), pH = 7 at the beginning) was studied. For the first time, 2 ionised air water treatment pilot systems (IAPS-1, -2, no additives) were set up (Figs. 1 and 2). The degradation of methamidophos was carried out with only the IAPS-2 and with two different ultraviolet (UV) lamps: high- and low-pressure mercury lamps (HP and LP, with or without H202). The kinetics of these oxidative processes was investigated. The highest rate constant was reached by the LP, 0.2% H2O2 (k = 0.7524min(-1), t 1/2 = 0.9min), followed closely by both treatments with the HP, 0.2% H202 (k = 0.6328min(-1), t 1/2 = 1.1 min) and LP, 0% H202 (k = 0.4749min(-1), t 1/2 = 1.5 min). The lowest rate constants were achieved from the HP, 0% H202 process (k = 0.0303min(-1), t 1/2 = 22.9min) and from the IAPS-2 (k = 0.0117 min(-1), t 1/2 = 59.2min). The mineralisation of methamidophos was confirmed by the determination of the anions produced including NO3-, PO4(3-) and SO4(2-) during and at the end of each experiment. The toxicity of water samples before, during and after the experiments was tested with Daphnia test.
