RESOURCES
Ozone CT Values & Dosage Reference
Research-based reference data for ozone disinfection CT values and standard applied ozone doses across 25+ applications worldwide. Sources include US EPA, WHO, AWWA, FSSAI, CPCB, BIS, and peer-reviewed literature.
Ozone CT Values — Disinfection Reference
CT (mg·min/L) = Dissolved ozone concentration (mg/L) × Contact time (minutes). All values at pH 7–8 and 20°C. CT increases ~15% per 5°C temperature decrease (i.e. cold water requires more ozone or longer contact time). At pH above 8, ozone decomposes faster — effective CT decreases.
Sources: US EPA LT2ESWTR Technical Guidance Manual (2003); WHO Guidelines for Drinking-Water Quality 4th Edition (2017); AWWA Research Foundation; peer-reviewed environmental microbiology literature.
| Pathogen | Type | 2-log CT | 3-log CT | 4-log CT | Notes | Source |
|---|---|---|---|---|---|---|
| E. coli O157:H7 | Bacteria | 0.02 | 0.04 | 0.08 | Extremely sensitive to ozone; inactivated within seconds at 0.1 mg/L | US EPA / WHO GDWQ |
| Salmonella typhi | Bacteria | 0.05 | 0.10 | 0.20 | Food-borne pathogen; inactivated at very low CT | AWWA Research Foundation |
| Pseudomonas aeruginosa | Bacteria | 0.10 | 0.50 | 1.00 | Hospital-relevant; ozone also removes biofilm matrix | WHO GDWQ 4th Ed. |
| Legionella pneumophila | Bacteria | 0.15 | 0.40 | 0.80 | Cooling tower pathogen; ozone at 0.1 mg/L residual prevents colonisation | ASHRAE 188 / AWWA |
| Staphylococcus aureus | Bacteria | 0.10 | 0.30 | 0.60 | Food processing and healthcare; ozone effective on biofilms | AWWA / Journal of Food Protection |
| Listeria monocytogenes | Bacteria | 0.15 | 0.35 | 0.70 | Food safety pathogen; FSSAI regulated for produce washing | US FDA / FSSAI |
| Mycobacterium avium | Bacteria | 0.60 | 1.50 | 3.00 | More resistant than common bacteria; important for immunocompromised patients | AWWA Research Foundation |
| Poliovirus type 1 | Virus | 0.10 | 0.25 | 0.50 | US EPA requires 4-log virus inactivation for surface water treatment | US EPA SWTR / LT2ESWTR |
| Rotavirus | Virus | 0.12 | 0.30 | 0.60 | Major waterborne diarrhoeal pathogen; very sensitive to ozone | WHO GDWQ 4th Ed. |
| Hepatitis A virus | Virus | 0.20 | 0.50 | 1.00 | Enteric virus; ozone effective at low CT values | US EPA / AWWA |
| MS2 bacteriophage (surrogate) | Virus | 0.30 | 0.70 | 1.40 | Conservative surrogate for enteric viruses; used for system validation | US EPA Disinfection Guidance Manual |
| Norovirus (GII) | Virus | 0.25 | 0.60 | 1.20 | Primary cause of non-bacterial gastroenteritis; ozone more effective than chlorine | WHO GDWQ / Environ. Sci. Technol. |
| Adenovirus (type 40/41) | Virus | 1.00 | 2.50 | 5.00 | Most ozone-resistant common virus; medium-pressure UV combined with ozone recommended | US EPA LT2ESWTR Tech. Guidance |
| Coronavirus (surrogate MHV) | Virus | 0.08 | 0.20 | 0.40 | Enveloped viruses (including SARS-CoV-2 surrogates) highly sensitive to ozone | Chin. J. Epidemiology / WHO |
| Giardia lamblia cysts | Protozoa | 0.20 | 0.50 | 1.50 | 100× less CT than chlorine at equivalent log inactivation; US EPA awards log credits | US EPA LT2ESWTR |
| Cryptosporidium parvum oocysts | Protozoa | 5.80 | 12.0 | — | Chlorine-resistant (CT >7,200 mg·min/L); ozone or UV required. Milwaukee outbreak 1993 | US EPA LT2ESWTR (Table B-3) |
| Toxoplasma gondii | Protozoa | ~5.0 | — | — | Zoonotic protozoan; limited ozone CT data — high dose recommended | WHO GDWQ / Appl. Environ. Microbiol. |
| Bacillus subtilis spores | Bacterial spore | 2.00 | 6.00 | — | Used as indicator for most resistant organisms; not a routine public health concern | Water Research Foundation |
CT values in mg·min/L. Temperature correction: multiply CT by 1.15 for every 5°C below 20°C (e.g. 10°C water requires CT × 1.33). pH correction: multiply CT by 1.2 for pH 8.5 vs pH 7. — indicates insufficient published data for that log level at standard conditions.
Standard Ozone Doses by Application
Applied ozone dose is the total ozone injected into the water, accounting for immediate ozone demand from organic matter and reducing agents, the CT dose for pathogen inactivation, and a target residual at the contact chamber outlet. Applied dose is always higher than the CT dose alone — typically 3–5× higher for wastewater applications.
Sources: US EPA, WHO, AWWA, CPCB, BIS IS 10500, FSSAI, ASHRAE, IMO, USP, EU directives, and industry-specific guidance documents. Doses shown are typical mid-range values — actual dose must be determined by jar testing or pilot trial for each specific water quality.
| Application | Applied Dose | Contact Time | Treatment Goal | Applicable Standards |
|---|---|---|---|---|
| Drinking water — surface water (rivers, reservoirs) | 1.0–3.0 mg/L | 5–10 min | Giardia/Crypto inactivation, taste/odour, colour | US EPA LT2ESWTR; WHO GDWQ; BIS IS 10500:2012; EU Directive 2020/2184 |
| Drinking water — groundwater / borewell | 0.5–1.5 mg/L | 5–8 min | Iron/Mn oxidation, bacterial kill, H₂S removal | BIS IS 10500:2012; CPCB; WHO |
| Drinking water — bottled water production | 0.4–0.8 mg/L | 5 min | 4-log virus + bacteria reduction, no residue in bottle | US FDA 21 CFR §173.368; FSSAI; BIS IS 14543 |
| STP secondary effluent — reuse (irrigation, toilet flush) | 1.0–3.0 mg/L | 10–15 min | Faecal coliforms <100 MPN/100mL, BOD polishing | CPCB GNSS 2015; IS 17590; WHO 2006 reuse guidelines |
| STP tertiary effluent — river / lake discharge | 2.0–4.0 mg/L | 10–15 min | COD polishing, pathogen removal, odour control | CPCB Schedule VI; NMCG / NAMAMI GANGE norms |
| ETP — textile / dye effluent colour removal | 5.0–15.0 mg/L | 15–30 min | Decolorisation of reactive dyes, COD reduction 40–60% | CPCB Schedule VI; State PCB limits; EU BREF textile |
| ETP — pharmaceutical / API effluent | 5.0–10.0 mg/L | 15–20 min | API micropollutant degradation, COD reduction, colour | CPCB / State PCB; EU IED Directive; WHO pharma effluent |
| ETP — brewery / distillery effluent | 4.0–8.0 mg/L (post-biological) | 10–15 min | Residual COD, colour from caramel malt, yeast odour | CPCB Schedule VI; State Pollution Control Board |
| ETP — tannery effluent (chromium-free) | 6.0–12.0 mg/L | 20–30 min | H₂S odour, colour, BOD polishing post-biological | CPCB Schedule VI; SPCB effluent norms |
| Ballast water treatment (marine) | 3.0–6.0 mg/L | 5 min | IMO D-2 standard: <10 viable organisms/m³ (>50 µm) | IMO BWM Convention 2004; USCG 33 CFR Part 151 |
| Swimming pool (recirculation sidestream) | 2.0–4.0 mg/L sidestream | 30–60 sec | Cryptosporidium, chloramine destruction, water clarity | BIS IS 3552; WHO GDWQ pools; PWTAG (UK); DIN 19643 (Germany) |
| Spa / whirlpool / hot tub | 1.0–2.0 mg/L sidestream | 30 sec | Legionella control, chloramine reduction at high temp | PWTAG; NSF/ANSI 50; WHO pool guidelines |
| Cooling tower — Legionella control | 0.1–0.3 mg/L residual (sidestream) | Continuous | Legionella pneumophila <1 CFU/100mL, biofilm prevention | ASHRAE 188-2018; UK HSE L8; EU ECDC; CPCB cooling water |
| Produce wash water (fruits & vegetables) | 0.5–2.0 mg/L | 1–3 min | 3-log E. coli, Salmonella, Listeria; no residue on produce | FSSAI FSS Regulations; US FDA GRAS 21 CFR §173.368; EU EC 1831/2003 |
| Seafood / fish processing water | 0.5–1.5 mg/L | 1–2 min | Microbial reduction, extend shelf life, no flavour impact | FSSAI; US FDA; Codex Alimentarius CAC/RCP 52 |
| Poultry processing chiller water | 1.0–3.0 mg/L | 1–3 min | Salmonella, Campylobacter on carcass surface | USDA FSIS; EU 853/2004; FSSAI |
| Food plant CIP (cleaning-in-place) | 1.0–3.0 mg/L dissolved | 10–20 min | Replace peracetic acid / hot water sanitisation step | FSSAI Schedule 4 GMP; FSSC 22000; BRC Food Safety |
| Cold storage / warehouse air disinfection | 0.05–0.3 ppm (air) | Cyclic / continuous | Mould, ethylene destruction, extend produce shelf life | FSSAI; US FDA; USDA AMS; EU EC 2073/2005 |
| Pharmaceutical Purified Water (PW) loop | 0.1–0.2 mg/L residual | Continuous loop | Biofilm prevention, <100 CFU/mL USP limit maintenance | USP <1231>; WHO GMP Technical Report 970; EU GMP Annex 1 |
| Pharmaceutical WFI preparation (pre-distillation) | 0.5–1.5 mg/L | 5–10 min | Pretreatment microbial load, TOC reduction for distillation feed | USP <1231>; BP; EU Ph. Eur. 0169; WHO GMP |
| Clean room / sterile area air disinfection | 0.02–0.05 ppm (air) | Cyclic (room empty) | Surface bioburden reduction between production runs | ISO 14644; EU GMP Annex 1; ISPE Baseline Guide |
| Aquaculture RAS (recirculating systems) | 0.05–0.2 mg/L dissolved | Continuous | TAN oxidation, bacterial load, Nitrite reduction | FAO Fisheries Technical Paper 454; Global GAP Aquaculture |
| Hydroponic / greenhouse irrigation water | 0.2–0.5 mg/L | 3–5 min | Pythium, Fusarium, algae control without chemical residue | GlobalG.A.P.; EU water reuse 741/2020; USDA NOP organic |
| Commercial laundry (hospital linen / hotel) | 0.5–2.0 mg/L dissolved | 5–10 min wash cycle | Replace hot water (60°C) sanitisation; kill MRSA, Norovirus | COSHH (UK); NSF/ANSI 61; HTM 01-04 (NHS UK); ECDC HCAI guidance |
| Denim / garment stonewash (ozone fading) | 10–40 ppm gas phase | 20–60 min | Replace pumice stone + KMnO₄ bleaching; water-free process | ZDHC MRSL v3.1; bluesign; OEKO-TEX STeP |
All doses are applied dose (ozone injected), not dissolved residual. Transfer efficiency (venturi injector: ~90%; fine bubble diffuser: ~95%) must be applied to size the ozone generator. Contact Ozone India Technology for a formal sizing calculation for your specific water quality and flow rate.
Need a Sizing Calculation?
Ozone generator sizing requires flow rate, water quality (COD, turbidity, pH), and treatment target. Contact us for a free technical sizing and product recommendation.