How we cut reagent use 10× at a drilling site
At oilfield sites, the largest line item in water treatment is not electricity and not operator wages. It is reagents. Coagulants, flocculants, biocides, bactericides, corrosion inhibitors. Logistics to a remote site, storage, dosing, sludge disposal.
When in 2024 the company KB Kravtsova proposed that we jointly run pilot-scale industrial trials of sodium ferrate on the wastewater of one of the sites of a major Russian vertically integrated oil company, the initial task was simple: to check whether a single reagent could cover several treatment stages at once.
What it was before
The standard scheme for treating produced water (PW) for the reservoir pressure maintenance (RPM) system looks like this:
- Preliminary filtration
- Ultrafiltration
- Sorption on activated carbon
- Reverse osmosis
- Anion-exchange filters
- Dosing of biocides and inhibitors
Each stage means a separate reagent or consumable. At a large site, the total consumption of coagulants and biocides was measured in tonnes per month. In addition: biofilms, sulfate-reducing bacteria (SRB), hydrogen sulfide at concentrations up to 400 mg/dm³, dissolved petroleum products up to 10 mg/dm³.
What we did
We installed a sodium ferrate generator with a capacity of 1 kg/day right on site. The reagent is produced on the spot: the feedstock is 20% NaOH caustic soda and a steel electrode. Energy consumption is 1 kWh per 1 kg of finished reagent. No logistics of hazardous cargo to the oilfield.
We matched the dosage to the actual wastewater of the site. The ferrate was fed into the existing node ahead of the filtration block. No infrastructure had to be rebuilt.
What we got
Wastewater parameters before and after integrated treatment using sodium ferrate:
| Parameter | Raw wastewater | After treatment | MPC |
|---|---|---|---|
| Suspended solids (TSS), mg/dm³ | 236 | 1.36 | 12.75 |
| Petroleum products (TPH), mg/dm³ | 0.78 | 0.053 | 0.1–0.3 |
| Total coliform bacteria, CFU/100 cm³ | – | 200 | 500 |
| Thermotolerant coliform bacteria, CFU/100 cm³ | – | 50 | 100 |
| Coliphages, PFU/100 cm³ | – | 0 | 100 |
| COD, mg/dm³ | 625 | 16 | 30 |
| pH | 8.7 | 8.0 | 6.0–9.0 |
| Hydrogen sulfide, mg/dm³ | – | 0.001 | – |
| BOD5, mg/dm³ | 221 | 3.0 | 3.0 |
On every parameter we came within the MPC. On petroleum products, below the limit. On microbiology, several times below what is permitted.
Whose consumption it replaced
Coagulant + flocculant. Fully. When ferrate decomposes, it forms Fe(OH)3 nanoparticles that act simultaneously as a coagulant and a flocculant. They bind suspended matter, petroleum products, heavy metals, phosphates.
Biocide/bactericide. Fully. Ferrate destroys SRB at concentrations where chlorine-based reagents are ineffective. Coliphages after treatment: 0 PFU/100 cm³.
Hydrogen sulfide oxidizer. Fully. Ferrate oxidizes H2S to sulfates. This removes two problems at once: odor and pipeline corrosion. In the trials, the hydrogen sulfide concentration dropped to 0.001 mg/dm³ from initial values up to 400.
Reagent for petroleum product removal. Fully. It oxidizes organics to simple compounds and binds the residues into sludge.
In total: one reagent instead of 4 procurement items. Reagent consumption by mass is 10 times lower than the combined consumption of the replaced reagents. Efficiency is higher on microbiology and COD, and comparable on petroleum products.
Cold water
A separate point for Arctic and northern projects: ferrate retains its efficiency at temperatures of 0–5 °C. Chlorine and aluminum coagulants work poorly under these conditions. In Yamal, Taimyr, and the Arctic zone of Russia, this is the difference between «the standards are met» and «the standards are met with a stretch and periodic discharges during the off-season».
A parallel case: OQ, Oman
In December 2025, a pilot took place at the OQ oilfield in Oman. A ferrate dosage of 20–50 mg/L:
- TSS: −91% (140 → 12 mg/L)
- TPH: not detected
- Fe: −100%
- P: −86%
Industrial scale-up is in progress.
What this means for a drilling rig
If your site currently runs parallel procurement of coagulant, flocculant, and biocide, it makes sense to calculate which works out cheaper: continuing to buy three reagents or installing a generator for one.
Consumables after the generator is installed: only caustic soda and a steel electrode. The electrode is replaced in 2 minutes once every 4 days. The replacement is done by a regular operator without special permits.
For laboratory trials on your own water samples, 30 liters need to be sent.