Difficulties and Solutions in Oilfield Wastewater Treatment

I. Core difficulties in oilfield wastewater treatment

1. Stable emulsified oil is hard to break

Problem: crude oil and water form an "oil-in-water" or "water-in-oil" emulsion system, with oil droplet diameters of only 0.1-10 microns, which conventional gravity settling cannot separate.

Impact: the oil content of the effluent exceeds the standard (for example, some oilfield wastewater has an oil content of 15-20 mg/L, far above the discharge limit of <= 5 mg/L), clogging pipelines and formations.

2. Toxic substances are difficult to degrade

Problem: the wastewater contains sulfides, phenols, heavy metals and residual polymers, which are toxic or refractory.

Impact: conventional biological treatment is inefficient and may even kill microorganisms; chemical oxidation requires large quantities of chemicals and is costly.

3. Large water volume fluctuations demand high equipment adaptability

Problem: wastewater output varies greatly between wells and production stages (from a few hundred mg/L to tens of thousands of mg/L), and the water composition is complex (for example, fluctuating sand content and salinity).

Impact: equipment is prone to degraded treatment performance or failure under sudden load changes (such as membrane element clogging and sharply increased pumping energy consumption).

4. High sludge treatment cost

Problem: the sludge produced during treatment contains heavy metals and organics and requires special treatment such as drying and incineration.

Impact: sludge disposal accounts for 30%-50% of total treatment cost and carries a risk of secondary pollution.

II. Targeted solutions

1. Emulsified oil treatment: a combined process of demulsification + air flotation + filtration

Demulsification technology:

Demulsifiers are dosed (such as polyaluminium chloride and polyacrylamide compounded agents), using charge neutralisation and adsorption bridging to make tiny oil droplets agglomerate into large oil masses.

Dosing system optimisation: an intelligent demulsification system can automatically adjust the chemical dosage according to the oil content of the wastewater, improving demulsification efficiency.

· CDFUTechnology of the cyclonic dissolved-air flotation integrated unit:

The cyclonic dissolved-air flotation integrated unit generates micro-bubbles 5-50 um in diameter through pressurised dissolved air, while using the centrifugal force produced by the cyclone device to intensify the collision and adsorption between oil droplets and bubbles, forming gas-solid-liquid complexes with a density lower than water. Under the dual action of cyclonic shear and buoyancy, these rise rapidly to the surface and are scraped off, achieving efficient separation of oil from water.

Results: oil removal rate of over 95%, with the effluent oil content reduced to below 10 mg/L.

KFM filtration technology:

KFM active filter media independently developed by SINOKLE further intercept fine oil droplets and suspended solids. Made from silicate-based materials through 60 special processes, KFM active filter media undergo super-hydrophilic surface modification, providing ample adsorption and reaction interface for pollutants. Backwashing is easy, and a single backwash of only 10-15 minutes is enough to complete regeneration.

Case: at an oilfield central treating station, the combined process of "demulsification + air flotation + filtration" produced clear, transparent effluent suitable for direct reinjection or landscaping irrigation.

2. Treatment of toxic substances

· CDOF (Cyclonic dissolved-air ozone flotation integrated unit)

A patented high-efficiency ozone catalyst is used to generate hydroxyl radicals (OH) from ozone, whose super-strong oxidising power converts toxic substances into non-toxic or easily separable forms.

For refractory organics (such as polymers and surfactants), it breaks their chemical bonds.

3. Coping with water volume fluctuations: intelligent control

Intelligent control system:

By monitoring the quality and quantity of the influent in real time, parameters such as aeration intensity and chemical dosage are adjusted automatically, optimising operating efficiency and saving costs.

4. Sludge treatment: resource utilisation + drying and incineration

Resource utilisation:

Oily sludge is subjected to pyrolysis or extraction to recover crude oil and reduce resource waste.

Drying and incineration:

For heavy-metal-containing sludge, drying followed by incineration is adopted, together with an off-gas treatment system, achieving volume reduction and harmlessness.

III. Economic optimisation measures

1. Chemical optimisation:

Determine the optimal dosage of demulsifier and flocculant through experiments, reducing chemical waste.

2. Equipment maintenance:

Regularly clean the dissolved-air release device and check equipment sealing to extend equipment service life.