Thermal Power Plant Oily Wastewater: A Full-Process Purely Physical Treatment Route

Why Power Plant Oily Wastewater Has No Standard Recipe

In the field of industrial wastewater treatment, oily wastewater from thermal power plants has long been a "hard nut" because of its complex composition, high degree of emulsification and difficult treatment. Unlike a refinery, where the oily stream arrives from one or two defined units, a power station generates oily water from several unrelated places, and they all end up in the same pit.

• Fuel oil tank cleaning water, drawn during periodic tank maintenance
• Flushing water from oil pump and pipeline leakage
• Water contaminated by grease in coal handling systems

Mixing them creates a feed whose oil content, emulsification degree and solids load can change within a single shift. Any process that assumes a stable feed will produce a stable result only on paper.

Three Difficulties That Decide the Process Route

Emulsified oil is hard to separate

The wastewater contains large amounts of emulsified oil, and conventional settling and centrifugation cannot effectively break the emulsified state, resulting in low oil removal efficiency and effluent that struggles to meet standards. The interfacial film around each droplet is the obstacle, and no amount of extra retention time will remove it.

Poor adaptability to operating conditions

The oil content of the wastewater fluctuates widely, from a few hundred mg/L to hundreds of thousands of mg/L in severe cases. A treatment train designed around the average will fail at both ends of that range.

Conflicting treatment objectives

Power stations need compliance, low operating cost and minimal hazardous waste simultaneously. Chemical demulsification improves separation but converts the problem into oily sludge, which is itself a regulated waste stream with a disposal cost.

The Purely Physical Route in Outline

As a national high-tech enterprise focused on difficult industrial wastewater treatment, SINOKLE has drawn on nearly a decade of technological accumulation and innovation to build a full-process solution for oily wastewater at thermal power plants. Centered on purely physical separation technology, it overcomes the pain points of conventional processes and offers the power industry an efficient, environmentally sound and economical new option for water environment management.

The physical route works by manipulating droplet size and buoyancy rather than by adding chemistry. Coalescing internals give fine droplets a surface to meet on, so they grow. Micro-bubble flotation then attaches gas to the enlarged droplets and lifts them out. Because nothing is dosed, the separated oil stays in a form that can be recovered rather than disposed of.

Matching Equipment to the Duty

In practice the train is assembled from units with distinct roles. A cyclonic dissolved air flotation stage handles the bulk separation of oil and suspended solids on a compact footprint. Where the remaining load is dissolved or finely dispersed, an ozone catalytic oxidation stage takes over and breaks down refractory organics that separation alone cannot reach. Where effluent oil and solids limits are tight, a filtration stage polishes the stream before discharge or reuse. The KHC range covers the coalescing duty in oil removal and separation service, and the CDOF unit provides the integrated oxidation and flotation function at the back end.

What the Combination Delivers at the Discharge Point

Three outcomes distinguish the physical route from the conventional one. Effluent quality becomes predictable, because the process no longer depends on the operator's judgement about how much chemical to add. Waste oil becomes recoverable, because it has not been contaminated with flocculant. And the operating cost profile flattens, because the largest recurring expense in the conventional route — reagents and sludge disposal — largely disappears.

Operating Cost Through a Full Year

It is worth following the money rather than the equipment list. In the conventional route, the recurring cost is dominated by reagent purchase and by hazardous waste disposal, and both scale with the oil load rather than with the treated volume. That makes the cost curve rise exactly when the plant is under the most stress, which is a poor property for a treatment step to have.

The physically based route inverts that behaviour. Power consumption is the main recurring item, and it tracks the treated volume rather than the contaminant load. When the feed becomes harder, the process does more work at broadly the same energy cost, and the additional oil it separates carries a recovery value. Over a full year of continuous operation, the difference between the two cost profiles is usually larger than the difference in capital cost that decided the original tender.

Specifying the Train on Numbers

Concrete figures make the specification easier to argue. The separation stage is built around a CDFU unit, sized so that dispersed oil droplets down to 0.1 μm are captured and fine particulates down to 1.5 μm are lifted out rather than left to settle. For flows where the coarse fraction dominates, a swirl dissolved air flotation vessel of 1,000 μm bubble rating would be ample, but power station wastewater rarely allows that assumption.

Loads seen in practice span a wide band. A lightly loaded stream may enter at 10 mg/L of oil, while a severely emulsified batch from tank cleaning can arrive at 100 mg/L or higher, with individual events reaching 1,000 mg/L. The filtration and polishing stage downstream is set to hold effluent oil below 20 mg/L and suspended solids so that the final treated stream meets COD limits and, where reuse is intended, the relevant discharge class such as GB8978. The KFM active filter media unit covers the polishing duty at this point, removing the residual oil at 6 ppm and the fine solids that the flotation stage passed through, while 30 μm and finer bubbles in the flotation zone do the lifting work upstream.

Applicability Boundaries

The physical route is at its strongest where emulsified oil dominates, where oil content swings widely, and where sludge disposal is expensive or constrained. It is a poorer fit for streams whose main problem is dissolved salts or high ammonia, since those need a different mechanism entirely. Plants facing that combination should treat the oily water solution as one stage of a wider train rather than an answer on its own. Sized and applied that way, it removes the most persistent obstacle in power station water management without creating a new waste stream in the process.