Table 2.

Suggested wastewater disinfection method during Covid-19, their advantages, concerns during usage and environmental concerns.

Method	Effectiveness	Advantage	Concern	Environmental concerns
Peracetic acid	Stronger oxidant than HOCl or ClO2, less than O3 Broad spectrum of activity against microbes	•Less influence of wastewater quality (pH, COD and BOD) •Can be used at very low concentrations, contact time and temperatures •Low freezing point, substantially stable •Negligible effect of temperature, organics and suspended solids •Easier to apply (available as a stabilized equilibrium solution)	•Highly reactive and not safe for every surface (might corrode soft metals)	•Insignificant environmental impact •No harmful disinfection by-products (break down into water and acetic acid) •No  formation  of   chlorinated  disinfection  byproduct,  such  as  trihalomethanes Lower  aquatic  toxicity •Does not affect effluent toxicity
Performic acid	More effective against viruses than peracetic acid, Wide-spectrum disinfectant.	•Lack of harmful disinfection byproducts •High oxidation power •Works efficiently at lower temperatures	•Instability, needs to be generated continuously and maintained below 20 °C •Potential safety issues as it is explosive at high temperatures, concentrations. •Thermodynamically unstable even in mild conditions	•By-products of (H2O2 and formic acid) are not toxic to aquatic fauna •Very high mobility in soil
UV	High viral inactivation efficiency	•No need of chemical addition •Non-corrosive, simple installation and operation •Energy requirements are relatively low	•Effect is hindered by turbidity and colour •Cannot provide residual disinfection •Depth of penetration is inadequate •Difficult to monitor equipment performance •Application of secondary disinfectant is necessary	•No formation of disinfection by-products •There are occupational health risks
Ozonation	Higher microbicidal efficacy than chlorine, Very strong oxidant	•Quick action, •Can remove colour, odour •As biocide more effective than Cl, chloramines and ClO2 •Highly efficient for viral inactivation	•No continuous disinfection effect •Least stable in water •Operation and maintenance problems •High ozone demand of many effluents •High capital, operational and maintenance costs •No provision of residual protection (need of secondary disinfection)	•Might increase water acidity level •Over-dose of may cause bad smell and secondary pollution •Might form by-products through reaction with bromide and iodide. •Requires off-gas destruction or quenching •No formation of halogenated by-products
Sodium dichloro isocyanurate	Broad germicidal action	•Retain Cl longer (more prolonged effect) •Easily disseminated, and stored for over 5 years •advantages in terms of safety, cost and ease of application •Effective against wide pH range •Not corrosive	•At high concentration (40 mg l − 1) might increase COD	•No environmental and health concern •low acute oral toxicity •No teratogenic, genotoxic, carcinogenic effects •Not metabolized in the body and do not bioaccumulate •High adherence to water treatment recommendations and positive attitude
Hypochlorite	Broad spectrum of antimicrobial activity	•No toxic residues •Affectivity does not depend on water hardness •Inexpensive •Fast acting •Stable operation	•High corrosivity to metals •Inactivation by organic matters •Less tability •Release of a strong odour •High energy consumption.	•Low environmental impact (by EPA) •Production of the animal carcinogen trihalomethane •Release toxic Cl gas upon reaction with ammonia or acid
Chloramine	Viral inactivation is slower than free chlorine, weaker	•Relatively stable •Release Cl over long period •Decreased formation of biofilms since residual levels remain relatively constant throughout the system	•Oxidizing and disinfecting potential less than Cl, HOCl acid and HOCl−	•Environmental concern less •Significantly lower levels of byproduct (Nitrosamines may be generated having carcinogenic property) •No ready reaction with organics to form trihalomethane •No harmful health effects
Hypochlorous acid	Virucidal efficiency more than 50 times greater than chloramines	•Excellent disinfectant for non turbid waters that are free of ammonia and organic compounds	•Losses free Cl thus efficiency with time (Should be used within three months of manufacturing). •Exposure to UV radiation, sunlight, air contact, and a temperature greater than 25 °C decreases its stability	•Formation of harmful disinfection by-products (THM)
Chlorine dioxide	Effective against a wide range of pathogens	•No reaction with ammonia nitrogen •Effective over large pH range (pH 5–10) •Lower costs of operation & preparation •Oxygenation, Decolouring and deodorization ability •Soluble at low temperature,	•Expensive than free Cl •Reacts with organic matter •Need to prepare fresh (less stable) •By-product formation of chlorite and chlorate, •Might be explosive at high temperatures and pressures •Sunlight and UV radiation mediated decomposition	•No formation of potentially toxic by-products like THM •Might form undesirable halogenated organic compounds, inorganic by-products (chlorite and chlorate) with dissolved organic carbon, microbes and inorganic ions.
Benzalconium chloride	Relatively limited spectrum of activity	•May be used under various pH conditions •Non-corrosive to metals	•Non ideal for hard water	•Health and environmentally friendly option •Less toxic when used in low concentrations (high concentrations can result in skin and respiratory irritation). •Degrade rapidly in the environment
Hydrogen peroxide	Effective against virus	•Can be applied at high concentrations, temperatures •Fast-acting, Very versatile •reduce the BOD and COD •Can be used in combination with catalysts •Treat wide range organic contaminants and some toxic metals	•High chemical cost, High operational cost	•Environmentally compatible, Non-pollutant •Extremely safe in terms of health •Does not produce harmful residues (break down into water and oxygen)
Solar radiation	Sufficient effect of virus inactivation	•Clean, low operation cost and	•Quality of water, insolation time should be taken in to account	•No environmental concern