Chlorine no longer cuts it
Chlorination as a technology appeared in the early 20th century. Since then, so many objections have piled up against it that most European countries have already abandoned chlorine. In Russia the process is slower, but it is happening: SanPiN standards are tightening, and the limits for residual chlorine and chlorinated organics are converging with global norms.
For a water utility this means one thing: sooner or later the scheme will have to change. The only question is what to switch to and at what cost.
What is wrong with chlorine
Chlorinated organics. When chlorine reacts with organic substances in water, it forms trihalomethanes (THMs), chloroform, and dichloroacetonitriles. Some of them are carcinogens. Concentrations often slip past laboratory monitoring, because the analysis arrives with a delay of up to two weeks.
Residual chlorine. Free and combined chlorine remain in the discharged water. Monitoring is tightening: the limit concentrations in regulatory documents are dropping, and a classic chlorine installation has few ways to lower residual chlorine without making the scheme more expensive.
Sulfate-reducing bacteria (SRB). Chlorine handles biofilms poorly. In trials of the ferrate installation, SRB were reduced to non-detectable levels even at low doses. To achieve the same result, chlorine requires concentrations at which the amount of chlorinated organics becomes critically high.
Cold water. The effectiveness of chlorination drops at temperatures below 5 °C. For northern regions and the Arctic zone this means that in winter the microbiological standards are not met, or the dose has to be increased — and we are back to chlorinated organics.
Hazardous goods logistics. Chlorine is a hazardous substance. Delivery, storage, permits, trained personnel, licenses. This is a cost line that is not immediately visible, but it is tangible in the annual report.
What is offered instead
Ozone. A strong oxidizer, with no residual chlorine. Downsides: an ozone generator consumes up to 15 kWh per 1 kg of ozone, requires a trained operator, and, when working with water containing bromides, forms bromates (also carcinogenic). Capital costs are high, operating costs are even higher.
UV disinfection. Leaves no chemical traces. But a UV lamp loses effectiveness with turbidity, requires regular replacement, and does not work on dark water with high color. Microbes can reactivate after passing the lamp. UV does not remove heavy metals or organics at all.
Hydrogen peroxide + catalysts. The technology works, but the dosages and reagent consumption make it economically heavy for large volumes.
Sodium ferrate. The strongest reagent oxidizer. It oxidizes, coagulates, and disinfects in a single process. The only reagent-based method that retains effectiveness at a water temperature of 0–5 °C.
Ferrate vs chlorine: what the trials show
At St. Petersburg Vodokanal, post-treatment of domestic wastewater was carried out with sodium ferrate. Results at a dose of 0.1 mg/L:
| Parameter | Source water | After treatment | MPC |
|---|---|---|---|
| TCB per 100 mL | 400,000 | < 50 CFU | < 1,000 |
| E. coli per 100 mL | 1,000 | < 50 CFU | < 100 |
| Coliphages per 100 mL | – | 0 | < 10 |
| Enterococci per 100 mL | – | 0 | < 10 |
| Staphylococci per 100 mL | – | 8 | 10 |
For comparison: chlorine requires a dose of 0.5–2 mg/L for a similar result, and in doing so it forms THMs.
Parameters for oil-bearing wastewater (integrated treatment with a sodium ferrate solution):
| Parameter | Source effluent | After treatment | MPC |
|---|---|---|---|
| Suspended solids, mg/dm³ | 236 | 1.36 | 12.75 |
| Petroleum products, mg/dm³ | 0.78 | 0.053 | 0.1–0.3 |
| COD, mg/dm³ | 625 | 16 | 30 |
| BOD5, mg/dm³ | 221 | 3.0 | 3.0 |
| Hydrogen sulfide, mg/dm³ | – | 0.001 | – |
| Coliphages, PFU/100 cm³ | – | 0 | 100 |
Hydrogen sulfide is a separate story. Chlorine oxidizes it partially and with the formation of by-products. Ferrate oxidizes it to sulfates, while suppressing SRB along the way. For reservoir pressure maintenance systems and water utilities with SRB-contaminated water, this provides years of additional service life for equipment and pipelines.
Cost of ownership
By total cost of ownership (CAPEX + OPEX + disposal + fines):
- Ferrate vs chlorine: 2 times cheaper
- Ferrate vs UV: up to 10 times cheaper
- Ferrate vs ozone: up to 10 times cheaper
This is not a marketing estimate. These are operational data from pilot deployments in 2023–2025.
What to do now
If you are running on chlorine today, the task is not to throw out the scheme and install a new one. The task is to understand which transition scenario will deliver the maximum savings.
Option 1: test the technology on your own water. Send us 30 liters and we will return an accredited laboratory report.
Option 2: get a reagent sample. Your laboratory will run the tests under its own protocol.