Chlorine-based disinfection is widely employed in major hospitals across China. However, a critical limitation of chlorine-containing disinfectants lies in their potential to react with other substances, generating hazardous byproducts that pose environmental and health risks. Consequently, total residual chlorine (TRC) monitoring is incorporated as a core indicator in medical wastewater surveillance, primarily aimed at regulating chlorine dosage to mitigate chlorine-induced pollution.
Residual chlorine is categorized into combined residual chlorine (CRC) and free residual chlorine (FRC) based on its chemical form and disinfectant activity. CRC forms when chlorine reacts with ammonium ions in water to produce chloramines. While chloramines exhibit significantly lower bactericidal efficacy than hypochlorous acid (HClO) and may cause odor issues, their high stability confers sustained disinfection performance, making them suitable for drinking water treatment. In contrast, FRC—also termed free chlorine—encompasses species such as hypochlorite (OCl⁻) and HClO in aqueous solutions. Characterized by strong oxidizing properties and superior disinfection efficiency, FRC is ideal for hygiene disinfection and swimming pool water treatment. Collectively, CRC and FRC constitute TRC, a pivotal parameter for hospital wastewater monitoring.
TRC is defined as the residual chlorine remaining in water following a contact period with chlorine-based oxidants, excluding chlorine consumed by microorganisms, organic matter, and inorganic substances. FRC exists as HClO or dissolved elemental chlorine (Cl₂), whereas CRC includes chloramines and organic chloramines. Residual chlorine in aquatic environments is predominantly introduced via anthropogenic chlorination—a water treatment technology that leverages chlorine’s strong oxidizing capacity for non-selective inactivation of bacteria, algae, and other microorganisms. With the widespread use of chlorine, the toxic and carcinogenic effects of its byproducts have garnered increasing attention, necessitating accurate analysis and quantification of chlorine levels. Additionally, real-time TRC monitoring is essential for precise chemical dosing, ensuring the cost-effective and efficient disinfection performance of chlorine.
The Hangzhou Modi RCl900 Total Residual Chlorine Online Analyzer is a fully automated instrument controlled by an embedded system. Water samples and anti-interference agents are automatically injected into the reactor, followed by the addition of a specific chromogenic reagent to initiate a color reaction. The absorbance of the resulting product is measured, and the analyzer directly calculates the TRC concentration in water based on the absorbance value.
