In order to improve the organic matter decomposition efficiency, and achieve a high TOC removal rate, a water treatment device, which subjects, to decomposition treatment, organic matter included in water to be treated, is provided with: a hydrogen peroxide addition device which adds hydrogen peroxide to the water to be treated; an ultraviolet irradiation device which irradiates, with ultraviolet,the water to be treated to which the hydrogen peroxide has been added; a dissolved oxygen measurement means which measures the dissolved oxygen concentration in outlet water of the ultraviolet irradiation device; and a control means which controls the addition amount of the hydrogen peroxide on the basis of the dissolved oxygen concentration measured by the dissolved oxygen measurement means.
피처리수에 포함되는 유기물을 분해 처리하는 수처리 장치는, 유기물의 분해 효율을 향상시켜서 높은 TOC 제거율을 달성하기 위하여, 피처리수에 과산화수소를 첨가하는 과산화수소 첨가장치와, 과산화수소가 첨가된 피처리수에 대해서 자외선을 조사하는 자외선 조사장치와, 자외선 조사장치의 출구수의 용존산소농도를 측정하는 용존산소측정 수단과, 용존산소측정 수단으로 측정된 용존산소농도에 의거해서 과산화수소의 첨가량을 제어하는 제어 수단을 포함한다.