Hospital wastewater can contain pathogenic microorganisms, antibiotic-resistant bacteria, pharmaceutical residues, and other contaminants. If it is not properly collected and treated, it may create environmental and public-health risks. However, the microbial concentration in hospital wastewater varies greatly with hospital type, department, flow, and sampling conditions, so unsupported fixed counts of bacteria or viruses per liter should not be used as universal data. The key objective of disinfection is to reduce viable pathogens to the level required by the applicable discharge standard while controlling the risks introduced by the treatment process itself.

Chlorine dioxide and potassium peroxymonosulfate composite disinfectants are both used in some hospital-wastewater treatment applications, but there is no universal 'safety champion.' Their suitability depends on the registered product formulation, wastewater quality, target microorganisms, contact system, operating capability, discharge requirements, and total life-cycle cost.

Round One: Disinfection Performance - Which Technology Fits the Target Microorganisms?

1. Chlorine dioxide: a strong oxidizing disinfectant with mature water-treatment applications

Chlorine dioxide is a strong oxidant that can inactivate microorganisms by oxidizing proteins, sulfur-containing amino acids, membrane-associated structures, and other essential cellular components. Under appropriate concentration, contact time, temperature, and wastewater conditions, it can be effective against many bacteria and some viruses. However, it is not technically sound to claim an instantaneous >99% kill rate or universal inactivation of poliovirus or hepatitis B virus without specifying the test method and process conditions. Its disinfection performance is relatively less affected by pH than that of free chlorine, but temperature, organic load, reducing substances, suspended solids, and contact time still matter. For hospital wastewater, dosage and contact time should therefore be determined from validated process conditions rather than a single broad pH or temperature claim.

2. Potassium peroxymonosulfate composite disinfectants: formulation-dependent oxidizing systems rather than a single universal chemistry

Products marketed for hospital-wastewater disinfection are often potassium peroxymonosulfate composite formulations rather than pure potassium peroxymonosulfate alone. Their antimicrobial performance may result from active oxygen together with other formulation components, and some commercial products also contain additional oxidizing or chlorine-releasing ingredients. Therefore, the mechanism, dose, contact time, residual behavior, and safety profile must be based on the specific registered product and its instructions. It is not appropriate to claim that every formulation provides a long-lasting residual after discharge, guarantees long-term suppression of microbial regrowth, reduces COD, flocculates suspended solids, and removes odor at the same time. Oxidation of some organic matter and odor compounds may occur, but the actual effect depends on wastewater composition, dose, and the complete treatment train.

Round Two: Safety and Environmental Control - What Risks Must Be Managed?

1. Chlorine dioxide: effective, but generation and by-products require control

Free-chlorine disinfection can form trihalomethanes and other halogenated disinfection by-products when it reacts with natural organic matter. Chlorine dioxide follows a different reaction pathway and can reduce the formation of some typical halogenated organic by-products compared with free chlorine, but it should not be described as risk-free. Chlorite and chlorate are important transformation products that may require control, and some generator routes can also introduce chlorine. Chlorine dioxide gas is irritating and hazardous at elevated airborne concentrations, so generation systems require ventilation, leak detection, interlocks, compatible materials, and trained operators. PPE should be selected according to the SDS and exposure assessment rather than a one-size-fits-all rule. Because chlorine dioxide is normally generated and used on site, equipment reliability and monitoring are part of the safety system.

2. Potassium peroxymonosulfate composite disinfectants: easier handling does not mean zero risk

Potassium peroxymonosulfate composite disinfectants do not release chlorine dioxide gas during normal use, but it is incorrect to describe them as 'zero pollution,' 'harmless to humans and animals,' or safe to handle without protective equipment. Peroxymonosulfate-containing products are oxidizing chemicals; depending on formulation they may be acidic, irritating to the eyes, skin, or respiratory tract, and incompatible with certain chemicals. Their decomposition and reaction products also depend on the complete formulation and wastewater chemistry, so they cannot simply be summarized as 'only potassium sulfate and water.' Operators should follow the product SDS, label, storage requirements, mixing restrictions, and required PPE. In residential areas, odor may be lower than with some on-site chlorine dioxide systems, but environmental compliance still depends on the treated effluent, not on the absence of a noticeable smell.

Round Three: Cost and Application - Which Option Is More Practical?

1. Chlorine dioxide: potentially economical at stable scale, but only with appropriate infrastructure

Chlorine dioxide can be cost-effective in continuous hospital-wastewater disinfection when flow and chemical demand are stable, but fixed figures such as 0.5-1 yuan per tonne or a threshold of more than 1,000 tonnes per day are not universal. Total cost should include the generator, feed chemicals, conversion efficiency, power, ventilation, leak detection, online monitoring, maintenance, spare parts, labor, and by-product monitoring. Feedstock prices also change with time and location. A well-designed generator can reduce manual work through automation, but it still requires routine inspection and competent operation; the economics should be established through a project-specific life-cycle calculation.

2. Potassium peroxymonosulfate composite disinfectants: simpler dosing may suit smaller systems, but cost depends on formulation and demand

Many solid composite disinfectants can be dosed without an on-site chlorine dioxide generator, which may simplify the equipment configuration for smaller hospitals, clinics, or decentralized systems. However, this does not make every product 'plug-and-play.' Dissolution, dosing, mixing, contact time, chemical storage, corrosion compatibility, and operator protection still need to be managed. Statements that the cost is always two to three times that of chlorine dioxide or always 1-2 yuan per tonne should be replaced by a calculation using the actual product dose, purchase price, wastewater quality, treatment target, and labor and equipment requirements.

Practical Guide: Three Principles for Selecting a Hospital-Wastewater Disinfectant

1. Consider treatment capacity and operating capability together. A larger hospital may benefit from an automated chlorine dioxide generation system when it has the required infrastructure and trained personnel, while a smaller facility may prefer a validated solid or liquid disinfectant dosing system. Plant size alone should not decide the technology; wastewater quality, required contact time, redundancy, maintenance capability, and discharge target are equally important.

2. Consider the surrounding environment, but do not rank technologies solely by odor. Hospitals near residential areas or sensitive water bodies should prioritize containment, ventilation, chemical-storage safety, effluent toxicity, disinfectant residuals, and compliance with local discharge requirements. A lower-odor product is not automatically environmentally safer, and chlorine dioxide should not automatically be excluded simply because the site is near a residential area.

3. Use combined processes only when each step has a validated purpose. It is not a general rule that chlorine dioxide should be used first and potassium peroxymonosulfate later for 'long-term control.' Sequential oxidants can consume one another or change downstream chemistry, and residual oxidant in final effluent is not necessarily desirable. If a combined process is considered, compatibility, oxidant demand, reaction products, contact time, toxicity, and final microbiological performance should be verified by bench or pilot testing before full-scale operation.

Hospital-wastewater disinfection is a process-control and compliance task, not a competition between two brand names or chemical labels. Choosing an unsuitable disinfectant does not automatically 'mutate pathogens into superbugs'; antibiotic resistance is driven by complex biological and environmental pressures, and disinfectant selection should not be described with that direct cause-and-effect claim. The more reliable approach is to characterize the wastewater, define the applicable microbial and pollutant limits, compare validated disinfection options, and monitor the final effluent. China's GB 18466-2005 was amended in 2026, with strengthened requirements for medical wastewater risk control, so current projects should use the applicable version together with local requirements and the facility's permit conditions. Chlorine dioxide and potassium peroxymonosulfate composite products can both be useful when correctly selected, but neither is universally safer, cheaper, or more effective in every hospital.