Landfill Leachate Without the Chemical Mountain: A Closed-Loop CDFU + CDOF + MBR Train
Landfill leachate is the stream that breaks standard treatment logic. Composition shifts with waste age, pollutant concentration is high, colour is heavy, and ammonia nitrogen arrives together with refractory organics at levels most biological systems were never sized for. The conventional answer has been a long flow sheet, a large chemical budget, and an operating team resigned to unstable effluent and high O&M costs.
Why the Usual Flow Sheet Struggles
Traditional leachate processes share the same set of pain points: lengthy flow, large chemical dosing, low nitrogen-removal efficiency, unstable effluent, and expensive operation. Each unit in the chain tends to be optimized on its own, so the failures accumulate rather than cancel out. Solid-waste operators end up paying twice, once in reagents and once in the labour needed to chase a moving target.
Front End: Cyclonic Flotation With Ozone Pre-Oxidation
Raw landfill leachate enters the CDFU cyclonic dissolved-air flotation unit, with ozone and a dedicated flocculant dosed at the same point. The cyclonic structure enhances flocculation, demulsification and solid-liquid separation, rapidly removing suspended sludge, oil, colloids and macromolecular humus from the leachate. Separated waste residue is discharged to a sludge tank for unified dewatering, and backwash waste liquid is refluxed to the front end for retreatment rather than leaving the site.
That front-end ozone pre-oxidation matters more than its size suggests. It prematurely cleaves some refractory organic molecular chains, which greatly reduces the load on the downstream oxidation units. Suspended-solids removal improves by more than 40% compared with traditional flotation, so everything after it runs on a better feed.
Multi-Stage CDOF: Where COD and Colour Are Actually Broken
Pretreated water enters the first-stage CDOF ozone advanced-oxidation flotation integrated device, with ozone and a water-quality modifier dosed. CDOF integrates ozone catalytic oxidation, microbubble flotation and flocculation-sedimentation in one shell: ozone generates strongly oxidizing hydroxyl radicals under the action of a dedicated catalyst, efficiently decomposing biochemically refractory COD such as humic acid and aromatic compounds, while flotation simultaneously separates the floc impurities that oxidation produces.
Ozone tail gas is collected and decomposed in a tail-gas destructor before discharge, so no odour escapes and the plant stays clean to work in. The first-stage CDOF effluent then splits: one stream to the high-efficiency denitrification reactor, the other refluxed to buffer and equalize water quality. That split is what buys the system its impact-load resistance.
Nitrogen, Then a Second Oxidation Pass
The high-efficiency denitrification reactor is the core nitrogen-removal unit. An external carbon source is dosed as needed to build a complete nitrification-denitrification system, deeply reducing total nitrogen and ammonia nitrogen. Its dedicated backwash system sends backwash water to the second-stage CDOF for advanced treatment rather than back to the head of the plant, which stops nitrogen pollutants from simply circulating.
After denitrification, the second-stage CDOF doses ozone and a water-quality modifier again to decolourize and degrade residual trace refractory organics, holding effluent colour and COD stable. Backwash waste liquid from this stage is refluxed to the front-end CDFU, realizing whole-process cyclic reduction of sewage.
MBR as the Polishing Barrier
Second-stage CDOF effluent enters the MBR membrane bioreactor, where a carbon source is supplemented to maintain microbial activity. Membrane modules retain activated sludge efficiently, greatly increasing sludge concentration in the biochemical system and strengthening deep removal of residual COD and total nitrogen. An internal sludge-reflux line returns sludge to the front-end sludge tank for unified disposal, preventing sludge loss, and MBR product water flows into the clean-water tank at reuse or discharge quality.
What the Closed Loop Buys
- Multi-stage ozone catalytic oxidation combined with cyclonic flotation has extremely strong adaptability to high-colour, highly refractory pollutants and is unaffected by leachate age fluctuations.
- The coupling design of the denitrification reactor plus MBR eliminates complex multi-stage A/O tanks and reduces equipment footprint by 50%.
- Highly integrated all-in-one equipment, modular layout, and automated online dosing, backwashing and tail-gas treatment greatly reduce manual O&M workload.
- Whole-process waste-liquid reflux achieves significant sewage reduction, with chemical and water-electricity unit consumption lower than conventional processes, giving obvious long-term operating-cost advantage.
- Centralized tail-gas decomposition and separate sludge disposal solve the odour and random-sludge-discharge problems that make leachate stations unpopular neighbours.
Suitability and Outlook
The package is suited to new and old landfill and incineration-plant leachate upgrading as well as new construction projects, because it covers the whole chain of pretreatment, advanced oxidation, biological denitrification, deep filtration and by-product disposal in a single integrated scope. Retrofits benefit most: the footprint reduction is what usually makes an upgrade physically possible on a site that has run out of room.
As environmental discharge standards become increasingly stringent, stable compliant disposal of landfill leachate has become the key to compliant operation of solid-waste enterprises. SINOKLE's CDFU + multi-stage CDOF ozone advanced oxidation + high-efficiency denitrification + MBR combined package is built for exactly that, with sludge, backwash wastewater and ozone tail gas all given closed-loop disposal paths so that sewage, solid waste and waste gas are treated together with no secondary-pollution risk.