Water Disinfection Companies
Disinfection providers across chlorination, chloramination, ozonation, UV, and electrochemical processes for potable and reuse water.
21 specialist providers · 2 related · 10 countries
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Buyer's guide
The buyer's guide to water disinfection
Choosing Between Chlorination, UV, Ozone, and Chloramine for Water Disinfection
Disinfection technology selection is driven by the target organisms, the regulatory framework, and the presence of organic precursors that react with chemical oxidants to form disinfection byproducts (DBPs). Free chlorine is the most widely used primary disinfectant for potable water because it provides a residual throughout the distribution system, but it reacts with natural organic matter (NOM) to form trihalomethanes (THMs) and haloacetic acids (HAAs) regulated under EPA Stage 2 DBPR. UV disinfection at 254 nm inactivates Cryptosporidium and Giardia at doses where chlorine is largely ineffective, but provides no distribution system residual.
Ozone is the strongest oxidant used in water treatment, capable of inactivating virtually all pathogens at practical doses and oxidizing micropollutants including pharmaceuticals, pesticides, and taste/odor compounds. However, ozone generates bromate in bromide-containing source waters, requires on-site generation, and has higher capital and energy costs than chlorination. Chloramine, formed by combining chlorine and ammonia, is used as a secondary disinfectant in distribution systems to maintain residual without THM and HAA formation, but requires careful NH₃:Cl₂ ratio control to prevent free ammonia, which promotes nitrification.
For industrial process disinfection in cooling towers, process water circuits, and produced water, the oxidant choice also depends on material compatibility, contact time, and monitoring requirements. Chlorine dioxide is increasingly specified for industrial applications because it does not form THMs, penetrates biofilm more effectively than free chlorine, and maintains efficacy at higher pH values. Providers should supply a CT (concentration × time) calculation demonstrating that their proposed disinfectant dose achieves the required log inactivation credit for your target organisms.
Frequently asked questions
How do I choose between UV and chlorination for a potable water disinfection upgrade?
UV is the preferred technology when your source water has a Cryptosporidium or Giardia risk, when your distribution system is short (no residual required), or when you want to minimize DBP formation from high-NOM source water. Chlorination is required whenever distribution system residual must be maintained to prevent microbial regrowth. Many modern systems use UV as the primary inactivation step followed by a reduced chlorine dose for residual; this combination maximizes pathogen control while minimizing DBP formation.
What is a CT value and how does it determine my disinfection system design?
CT is the product of disinfectant concentration (C, in mg/L) multiplied by contact time (T, in minutes). EPA and state primacy agencies publish CT tables specifying the minimum CT required to achieve defined log inactivation credits for Giardia and viruses under different pH and temperature conditions. Your system design must demonstrate that the actual CT delivered, accounting for baffling efficiency, flow short-circuiting, and temperature variation, meets or exceeds the regulatory CT requirement under worst-case hydraulic conditions.
What causes nitrification in chloraminated distribution systems and how is it prevented?
Nitrification occurs when excess free ammonia in the distribution system supports the growth of ammonia-oxidizing bacteria (AOB), which convert ammonia to nitrite and nitrate and consume the chloramine residual. It is most common during warm summer months and in low-flow zones with long residence times. Prevention requires tight chlorine-to-ammonia mass ratio control (typically 4:1 to 5:1 by weight), booster chloramination at remote points in the system, flushing programs for dead-end mains, and a nitrification response plan with trigger levels for nitrite and monochloramine residual.
What should I require in a disinfection system commissioning protocol?
Commissioning should include disinfectant dose verification at design flow and minimum flow conditions, residual monitoring at defined points downstream, CT credit calculation under minimum temperature and maximum flow conditions, UV system validation testing per DVGW/NWRI protocols for UV applications, and documentation of all control system setpoints and alarms. For chlorine-based systems, confirm that chemical feed pump turndown ratio covers your full flow range without under- or overdosing at the extremes.
Illustrative scenario · Small water company, rural upland catchment, Wales
A composite drawn from typical projects in this category, not a single client engagement. Figures are indicative.
- Challenge
- A small water company supplying 8,000 properties from an upland reservoir was failing to achieve the DWI's 4-log Cryptosporidium reduction target using chlorination alone. A Cryptosporidium monitoring programme found oocysts in treated water above the mandatory investigation level on three occasions in 12 months.
- Approach
- A medium-pressure UV system validated to NSF 55 Class A standards was installed as a primary Cryptosporidium barrier, delivering a minimum validated UV dose of 40 mJ/cm2 at maximum flow and minimum lamp intensity. Downstream chlorination was retained at a reduced dose for distribution system residual, reducing THM formation by 30% compared to the previous chlorine-only strategy.
- Outcome
- Cryptosporidium monitoring in treated water returned to zero oocysts detected in all subsequent quarterly samples over a 24-month period, satisfying the DWI investigation requirement. THM compliance headroom improved significantly, and the reduced chlorine dose extended the taste and odour quality of supply across the distribution zone.
Questions to ask shortlisted providers
5
- 01
What validated UV dose does your system deliver at minimum lamp intensity and maximum design flow, and which third-party validation protocol was used?
UV systems must be validated under worst-case conditions; unvalidated dose claims from manufacturers do not provide regulatory credit for Cryptosporidium reduction.
- 02
For chlorine dosing systems, what is the turndown ratio of the chemical dosing pump, and how does it maintain accurate dosing at minimum night flow?
Under-dosing at low flow creates compliance risk; over-dosing at high flow risks THM formation exceedances.
- 03
What is the disinfectant CT value delivered at minimum design temperature and maximum design flow, and does it meet the DWI/WHO log inactivation target for your source type?
CT must be calculated at worst-case conditions, not average; many designs that appear compliant at average conditions fail at seasonal temperature minima.
- 04
How does the system detect and respond to UV lamp failure or chlorine dosing pump failure in real time?
A disinfection failure that persists undetected for even a few hours can result in distribution of inadequately treated water and a DWI reportable event.
- 05
What DBP monitoring program do you recommend alongside the disinfection system, and how is the dose algorithm adjusted if THMs approach the WS(WQ)R 2016 limit?
Disinfection dose must be balanced against DBP formation risk; a provider without a DBP management protocol is treating only one side of the compliance equation.
What drives cost in this category
4
- Disinfectant technology choice
- UV systems have higher capital cost than chlorination but lower DBP-related compliance risk; ozone adds on-site generation equipment and significantly higher energy operating cost compared to both alternatives.
- Flow rate and peak demand
- UV systems are sized to maintain minimum validated dose at peak flow; doubling flow rate roughly doubles the UV lamp bank required, as the system cannot simply be throttled.
- Residual monitoring and online instrumentation
- Continuous online chlorine, turbidity, and UV transmittance monitors are required for regulatory compliance; each instrument adds capital cost and requires annual calibration and maintenance.
- Chemical storage and containment
- Sodium hypochlorite or sulphur dioxide storage for dechlorination requires bunded secondary containment, DSEAR (Dangerous Substances) assessment, and EA notification, adding to civil and compliance costs.
Key regulations and standards
4
- Water Supply (Water Quality) Regulations 2016
- Requires disinfection systems to achieve 4-log Cryptosporidium and virus inactivation, with prescribed CT values or validated UV doses depending on source water classification.
- DWI UV Guidance Note
- Specifies the validation protocol and minimum validated UV dose requirements for UV systems installed on public water supplies in England and Wales.
- BS EN 14897
- Standard covering devices using UV radiation for treatment of water intended for human consumption, specifying performance, testing, and installation requirements.
- DWI Regulation 28
- Requires water companies to notify the DWI of any event that has caused or may cause water supplied to be unwholesome, including any disinfection system failure affecting microbial quality.
From the Insider
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