Desalter Cut Water Still Fails COD After De-oiling? The Carbon-Based Catalyst Option
Refineries that install good physical de-oiling often discover an uncomfortable thing: the oil number comes down and the COD number does not. Desalter cut water put through coalescence and cyclonic flotation will happily reach oil below 50 mg/L, but dissolved oil, gum and refractory organics stay in solution, and the downstream biological unit inherits a load it was never sized for. The plant passes an oil limit and fails a COD limit on the same sample.
KHC-F1001 is SINOKLE's answer to that residue. It is a carbon-based ozone catalyst built on high-iodine-value activated carbon rather than a mineral oxide, and the choice of carrier changes both the mechanism and the economics.
What a carbon carrier buys you
The substrate is high-porosity activated carbon with an iodine adsorption value above 1100 mg/g and a specific surface area of 1400 m2/g. Those two numbers are not decoration: the surface provides a very large population of sites where ozone and dissolved organics meet, and the well-developed pore structure adsorbs and holds trace pollutants long enough for radical attack to finish them. Active catalytic components are then loaded by a proprietary process, and a super-hydrophilic surface treatment keeps oil and suspended solids from blocking the pores — the usual reason carbon media die young in refinery service.
In operation the catalyst accelerates ozone decomposition into hydroxyl radicals at more than ten times the rate of ozone oxidation alone, mineralising macromolecular refractory organics rather than fragmenting them. COD, colour and toxic organic load all fall, and biodegradability improves enough to take pressure off the biological and reuse stages.
How the numbers compare
- Form: black particles or columnar 3–5 mm; regular shape, low fluid resistance, resistant to hardening.
- Surface: specific surface area 1400m2/g; iodine adsorption value 1100mg/g.
- Strength: mechanical strength 95%, so breakage stays low under long-term fluidisation and backwashing.
- pH range: 3~11, covering chemical and leachate streams with large acid-base swings.
- Performance: ozone decomposition rate 90%; COD removal 70%; colour removal 95%.
- Life: 3–5 years against an industry average of 2–3 years, and regenerable after deactivation.
Three operating cases
Refining electric-desalting cut water
A large petrochemical atmospheric and vacuum unit put its electric-desalting cut water through SINOKLE coalescence plus CDFU flotation, which brought effluent oil below 50 mg/L. Residual dissolved oil, gum and refractory organics still made the downstream biological influent COD too high, so a KHC-F1001 ozone catalytic oxidation stage was added at 100 ppm ozone, 5 g/L catalyst and 30 min hydraulic retention. Raw water COD fell from 320 mg/L to 40 mg/L. Across the two-stage train, influent oil of 180 mg/L produced effluent oil as low as 0.5 mg/L, with colour removal above 99%. The recovered crude oil paid for part of the installation.
Landfill leachate
Raw leachate COD of 20000 mg/L, heavily humic and almost non-biodegradable, treated by biochemical pre-treatment followed by KHC-F1001 ozone catalytic oxidation at 500 mg/L ozone, 10 g/L catalyst and 60 min reaction retention. The oxidation unit removed 99.5% of the COD and final effluent held below 100 mg/L, meeting the national domestic waste leachate discharge standard, with membrane system load and cleaning cost both reduced.
Dyeing wastewater decolourisation
Dye production wastewater with raw water colour of 800 times and COD 1200 mg/L, where conventional flocculation and biochemistry kept missing on both parameters. At 200 mg/L ozone, 8 g/L catalyst and 45 min reaction time, effluent colour came down to within 40 times and COD to 80 mg/L — 95% colour removal and 93.3% COD removal — without bulk dosing of decolourising flocculants, so chemical sludge and hazardous-waste cost fell as well.
Fitting it into a refinery flowsheet
For high-oil streams the sequence is a high-efficiency coalescence oil remover, then CDFU cyclonic dissolved-air flotation as purely physical zero-agent oil removal, then KHC-F1001 catalytic oxidation. Graded that way the train covers the full oily influent gradient and deals with emulsified oil and COD in the same line. For low-oil ordinary industrial wastewater the front end simplifies to two-stage CDFU flotation ahead of the catalytic unit, skid-integrated, compact, and installable on-line without stopping production — the configuration most often chosen for plant retrofits.
Control is automatic throughout: ozone dosing, catalytic reaction, backwashing and slag discharge run from online instruments with remote monitoring and unattended operation. The whole train is enclosed and pressurised, with waste gas collected and treated, so there is no odour and no uncontrolled leakage.
Why carbon rather than mineral oxide
The trade is straightforward. Mineral carriers win on mechanical life and extreme pH; a carbon carrier wins on surface area, adsorption of trace organics and cost, and it introduces no heavy metals at all — there is no metal loss to contaminate the effluent, unlike homogeneous metal-ion catalysis. Life is shorter at 3–5 years but regeneration is simple, and the whole-life O&M total stays below traditional dosing oxidation.
SINOKLE supports the media with R&D, water testing and field service, and the reference base covers CNPC, large Shandong petrochemical sites, dyeing plants and landfill operators running continuously for years. Extended duties include fine-chemical and pharmaceutical streams where antibiotics and halogenated intermediates must be broken down, municipal tail-water polishing for landscape and cooling make-up reuse, power and metallurgy circulating water, and VOC absorption liquor. Where physical de-oiling has already done its job and COD is still failing, this is usually the cheapest next step.