Why More and More Enterprises Choose "A Different Approach" for Upgrading Refining Wastewater Standards
For domestic refining and chemical enterprises, the phrase "compliant discharge" once meant a fixed flow: oil separation → flotation → biological treatment → sedimentation — the standard "old four-piece set". But as environmental policy has tightened year after year, especially after the revision of the Emission Standard of Pollutants for the Petroleum Refining Industry, with COD, ammonia nitrogen and total nitrogen limits being ratcheted up, more and more enterprises are finding that the old road no longer works.
It's Not That the Equipment Is Bad — the Technical Route Has Hit Its Ceiling
An environmental engineer who has worked in the refining industry for more than twenty years once put it this way: "Our biological tank is already big enough, we have changed the packing several times, and chemical costs rise every year, yet the effluent indicators just struggle along the compliance line — one small fluctuation and we exceed the limit."
This is in fact not an isolated phenomenon. Conventional refining wastewater treatment relies heavily on biological degradation, but refining wastewater contains large amounts of refractory organics — phenols, polycyclic aromatic hydrocarbons, petroleum resins — that microorganisms simply cannot "digest". If upstream pre-treatment is inadequate, the downstream biological system is dragged down.
The essence of the problem is this: the upstream demulsification and oxidation stages are too weak, offloading all the difficulty onto the downstream.
A Different Approach: Only by Subtracting Upstream Can You Add Downstream
In recent years a group of forward-looking refining enterprises has begun to adjust its technical route — moving the focus of treatment upstream so that most of the refractory organics are "shaved off" during pre-treatment, letting the downstream biological system operate with a lighter load.
The core of this approach is the combination of two key technologies:
The first step: efficient oil removal by cyclonic air flotation.
Taking SINOKLE'sCDFU cyclonic dissolved-air flotation unit as an example, it combines cyclonic centrifugal separation with ultrafine-bubble dissolved-air flotation technology: the residence time is less than 5 minutes and the single-stage oil removal rate already exceeds 90%, whereas a conventional flotation tank needs 15 to 40 minutes for an oil removal rate of only 60% to 85%. Even more important,CDFUit uses purely physical demulsification with no chemical agents and operates fully enclosed under pressure with no odour leakage. For a refining enterprise this means oil and suspended solids are sharply reduced upstream, cutting the load on the downstream biological system by an order of magnitude.
The second step: advanced pre-treatment by catalytic ozonation.
For those refractory organics that microorganisms cannot "chew through", SINOKLE'sCDOF advanced catalytic ozonation unit provides a highly efficient solution. It integrates multiple catalytic oxidation, hydrodynamic cavitation and cyclonic air flotation technologies, boosting the oxidation effect of ozone by more than four times, achieving a colour removal rate above 90%, and reducing sludge volume by more than 90% compared with the conventional Fenton process. The residence time is kept within 15 minutes, and the skid-mounted design takes up only one fifth of the space of conventional equipment.
After these two steps, the wastewater entering the biological system is already "perfectly clean" — less oil, lower COD, no colour — and the microorganisms can finally work normally.
Results in a Real-World Scenario
Take a standards-upgrading project at a certain refining enterprise: the effluent COD of the original "old four-piece set" system fluctuated between 80 and 120 mg/L over the long term, always falling just short of the new standard's 60 mg/L upper limit. After introducing SINOKLE'sCDFU+CDOF combined process, the pre-treatment effluent COD dropped below 40 mg/L and the biological system effluent stabilised at around 30 mg/L, far better than the discharge standard.
What satisfied management even more was the change in operating costs: chemical costs fell by more than 60%, sludge disposal costs were greatly reduced, and the equipment's high degree of automation allows remote monitoring and unattended operation.
Technology Is Changing — Thinking Must Change Even More
Refining wastewater treatment is not a problem that can be solved by "stacking up equipment". As the red lines of environmental policy continue to tighten, rather than constantly "patching" the old system it is better to make a fundamental adjustment to the technical route.
Over its 18 years of operation, SINOKLE has always focused on the innovation and application of wastewater treatment technology. From CDFU to CDOF, from oilfields to refineries, from China to overseas, more and more enterprises are proving through real results that: with a different approach, compliant discharge can actually be quite easy. If your enterprise is also worrying about standards upgrading, it is worth learning about SINOKLE's technical solutions. Sometimes the key to solving a problem is not spending more money, but choosing the right direction.
