The mineralisation of methamidophos using ionised AN air water treatment pilot system and ultraviolet irradiation

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 (Fig. 1 and Fig. 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 H2O2). The kinetics of these oxidative processes was investigated. The highest rate constant was reached by the LP, 0.2% H2O2 (k=0.7524 min−1, t1/2=0.9 min), followed closely by both treatments with the HP, 0.2% H2O2 (k=0.6328 min−1, t1/2=1.1 min) and LP, 0% H2O2 (k=0.4749 min−1, t1/2=1.5 min). The lowest rate constants were achieved from the HP, 0% H2O2 process (k=0.0303 min−1, t1/2=22.9 min) and from the IAPS-2 (k=0.0117 min−1, t1/2=59.2 min). The mineralisation of methamidophos was confirmed by the determination of the anions produced including NO3−, PO43− and SO42− during and at the end of each experiment. The toxicity of water samples before, during and after the experiments was tested with Daphnia test.