A test was conducted to investigate the decay of residual chlorine after UV disinfection and the influence of pH,concentration of organic matter and UV intensity and dosage on chlorine decay. The results showed: when the UV dosage was below 40 mj/cm2, there was little influence on chlorine decay from UV disinfection; when the UV dosage was above 40 mj/cm2, the chlorine decay rate would be accelerated; when the UV dosage increased from 40 mj/cm2 to 1 000 mJ/cm2 > the residual chlorine in drinking water would decrease from 3. 2 mg/L to 2.8 mg/L; the chlorine decay rate under low UV intensity was lower than the high UV intensity, and chlorine residual increased from 2. 31 mg/L to 2. 63 mg/L as the UV intensity was decreased from 0.113 00 mW/cm2 to 0.028 25 mW/cm2 at the UV dosage of 100 mj/cm2; under same UV dosage, the chlorine decay rate was higher in low pH situation than high pH; increasing the organic matter concentration will accelerate the chlorine decay rate. In the practical application of low UV intensity for disinfection, the reduction of UV dosage could not guarantee the necessary residual chlorine.%对经紫外线消毒后水中余氯的衰减规律进行了研究,考察了pH、有机物含量、紫外线强度及剂量等因素对氯衰减速率的影响.结果表明:紫外线剂量低于40 mJ/cm2时紫外线消毒对氯衰减基本没有影响,而当紫外线剂量大于40ml/cm2时会加速氯的衰减速度,紫外线剂量从40 mJ/cm2提高到1 000 mJ/cm2时,水中余氯由3.2 mg/L下降到2.8 mg/L;低紫外线强度下氯的衰减速度低于高紫外线强度情况,如紫外线剂量为100 mJ/cm2,紫外线强度为0.113 00 mW/cm2和0.028 25 mW/cm2时,水中余氯分别为2.31 mg/L和2.63 mg/L;在同一紫外线剂量下,pH偏酸性时氯衰减速度高于高pH情况;增加水中有机物浓度会加快氯的衰减速度.在实际应用低紫外线强度进行消毒时,如降低投氯量将不能有效保证管网水中的余氯量.
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