Configure by Pollutant Form, Not by Total Number: Routing Logic for Hard Wastewater
Two plants can report identical total oil, identical total COD and identical total suspended solids and still need completely different treatment trains, because the totals say nothing about the form the pollutants take. Total oil might be large free droplets, fine dispersed oil, or a stable emulsion. Total COD might be mostly biodegradable organics or mostly refractory compounds. Total suspended solids might be grit that settles in minutes or colloids that never settle at all. Form decides method; the total only decides how urgent the phone call is.
Five forms, five jobs
The core of SINOKLE's combined technology is configuration by pollutant form rather than one machine attempting everything. Large free oil goes to coalescing oil removal or hydrocyclone separation. Fine droplets and emulsified oil go to CDFU, cyclonic dissolved-air flotation, which strengthens capture and coalescence. Refractory organics, colour and odour go to the CDOF ozone advanced-oxidation flotation integrated unit. Residual fine particles and trace oil droplets go to the KFM active-media filter as end-of-line assurance.
Free oil and large dispersed oil are the easy fraction. Coalescence, cyclonic action and gravity all work, and a front-end coalescing oil remover makes small droplets collide, adsorb, coalesce and grow on the coalescing material until they separate readily. The goal at this stage is not deep treatment; it is knocking the high oil load down fast so the downstream units are not fighting it.
Fine dispersed oil and emulsified oil are where ordinary separation fails. Droplets are small and the interface is stable, so simple filtration clogs and gravity does nothing. CDFU raises the collision frequency and the rising driving force through its cyclonic flow field, micro-nano bubbles and coalescence action. Once a bubble attaches, the apparent density of the droplet falls and its rising velocity increases; as droplets coalesce and grow they separate more easily. That is why CDFU suits wastewater with high emulsification, fine droplets and oil bound up in suspended solids.
Organics, solids and the last trace
Suspended solids, colloids and oil-bearing particles drive effluent turbidity and load up whatever sits downstream. CDFU removes part of the suspended solids by flotation and the rest is filtered at the end of the line; on high-SS water, removing solids early lowers the indicator and also reduces fouling of downstream catalysts, media and membranes. Dissolved refractory organics are a separate problem entirely: they will not be removed by oil removal or filtration and need advanced oxidation to break the molecular structure. CDOF uses ozone catalytic oxidation and enhanced mass transfer to drive chain scission, ring opening and oxidation, improving colour and odour at the same time. For landfill leachate, chemical wastewater and oilfield composite wastewater, CDOF is the unit that resolves COD, colour and odour.
Finally there is the residual trace. After front-end oil removal and mid-stage oxidation, a small amount of fine pollutant can remain and make the effluent wander. The KFM active-media filter is the assurance stage that pulls residual oil, SS and turbidity down and holds them there. On reuse, reinjection, offshore discharge or membrane feed projects, that last stage is usually the one being specified.
How the routes look in practice
Refinery electric-desalting and tank-farm black water, dominated by high oil content and emulsified oil, runs a high-efficiency coalescing oil remover plus two-stage CDFU. At a petrochemical project in Xinjiang the influent oil content was ≤20000 ppm and treated effluent oil content was ≤150 ppm, which is the argument for that route on high-oil refinery water.
Coking acidic water, which is oily, strongly emulsified and hard to separate, uses CDFU followed by the KHC high-efficiency coalescing oil remover: CDFU takes out most of the oil and suspended solids quickly, then KHC coalesces and removes the fine emulsified fraction. Oilfield produced water, fracturing flowback fluid and drilling waste liquid take the full three-unit chain, CDFU for oil and SS, CDOF for refractory organics, colour and odour, and KFM to stabilise the effluent. After a Congo-Brazzaville oilfield project adopted this combination, effluent met offshore discharge standards with petroleum ≤0.5 ppm, turbidity ≤3 NFU, SS ≤3 mg/L and iron ≤0.15 mg/L.
Landfill leachate deep treatment leans on CDOF alone: ozone catalytic oxidation cuts COD while colour and odour improve in the same pass. At a leachate project in Shiyan, Hubei, MBR effluent COD was ≤1300 mg/L; after CDOF treatment COD was ≤400 mg/L, colour ≤30 and odour was gone, with subsequent biological treatment reaching lower still.
One caution applies to all four routes: the order matters as much as the selection. Oxidation placed ahead of oil removal wastes ozone on oil that flotation would have removed for the price of a pump, and filtration placed ahead of coalescence simply becomes an expensive oil absorber. The routes above work because each unit is asked to do the job it is fastest at, in the sequence that keeps the next unit clean.
The lesson is not that more equipment is better. It is that every pollutant has a method that removes it best and every unit should have one clear job. Identify the pollutant form, fix the treatment sequence, configure the units, then verify the effect. Stacking vessels without that order is how plants end up with a large train and a failing effluent.