Residual toxicant detection system and residual toxicant detection method

A residual toxicant detection system, comprising:

• a light source module including at least one light source emitter and at least one light sensor, wherein the at least one light source emitter emits a light having a specific wavelength range;
• a detection portion including an inlet, an outlet and a cavity, allowing an aqueous solution containing a residual toxicant to flow into the inlet, pass through the cavity and flow out of the outlet for the residual toxicant to react with the light having the specific wavelength range, wherein the at least one light sensor is configured to receive the light having the specific wavelength range that passes through the cavity at a plurality of times to produce a plurality of sensing signals, respectively;
• and
• a processing module configured to calculate an amount of change in absorbances of the aqueous solution respectively based on the sensing signals, wherein when the amount of change in the absorbances of the aqueous solution is less than a threshold, the processing module increases an accumulated detection count, and when the accumulated detection count is greater than or equal to a predetermined value, the processing module produces a detection result.