The Concentrate Trap Behind MBR and RO Leachate Trains, and the Membrane-Free Way Out
Landfill leachate is known for complex quality, extremely high pollutant concentration, high ammonia-nitrogen content and an unbalanced C/N ratio. Hailed as the king of high-concentration wastewater, it has long been one of the most technically difficult and environmentally risky links in solid-waste treatment. For years the dual-membrane process built on MBR + NF/RO, meaning membrane bioreactor plus nanofiltration and reverse osmosis, dominated the industry because its rejection performance was excellent and it could bring effluent to strict discharge standards quickly.
Behind that clear effluent, though, a chronic problem has been getting worse: what to do with the membrane concentrated liquid, which is hazardous waste. It has become the Achilles' heel constraining the sustainable development of the whole sector.
The membrane method moves pollution rather than destroying it
The traditional membrane process is built on physical screening, not thorough degradation. It produces roughly 70% to 80% clear liquid and concentrates most of the inorganic salts, heavy metals and refractory organics into the remaining 20% to 30%. That concentrate typically carries a COD above 5000 mg/L, deep colour and high toxicity. It is, in the most literal sense, the essence of the pollution.
The old habit of reflooding the landfill or reflowing concentrate to the equalization tank was drinking poison to quench thirst. Salts and refractory pollutants accumulate, circulating and enriching in the system until the microbial activity of the front-end biochemical unit is severely inhibited or poisoned outright, and the whole treatment line loses efficiency or collapses. High-salt, high-hardness concentrate also accelerates membrane scaling and fouling, forcing frequent chemical cleaning, shortening membrane life sharply, keeping O&M intensity high, and turning replacement cost into a standing burden. As environmental regulations tighten, including the landfill pollution control standard and its revision trends, reflooding has been explicitly restricted or prohibited, and the alternatives bring their own trouble: evaporation-crystallization consumes enormous energy, corrodes and scales equipment, and leaves crystalline mixed salt that is difficult and costly to dispose of as hazardous waste.
So the traditional route settles into a loop of pollution transfer, system deterioration, cost escalation and secondary pollution. What the industry needs is not a better membrane but a way to leave membranes out of it.
What a total-quantity, membrane-free route looks like
SINOKLE took a different path, abandoning the idea of relying on membrane separation and launching a patented process system centred on CDOF, the Cyclonic Dissolved Ozone Flotation integrated unit. The aim is total-quantity treatment of landfill leachate with thorough degradation of pollutants, and no concentrate stream at all.
The mechanism shifts from separation to mineralization. CDOF fuses ozone advanced oxidation with cyclonic dissolved air flotation. Its proprietary heterogeneous catalyst drives ozone to decompose into hydroxyl radicals, written as ·OH, with a redox potential as high as 2.8 V. That oxidant attacks large refractory organic molecules in leachate indiscriminately, humic acid and fulvic acid among them, breaking them apart and ultimately mineralizing them into carbon dioxide and water. The pollutant is eliminated at the molecular level rather than moved into a smaller volume.
Flotation does the rest, at the same time. While deep oxidation proceeds, the cyclonic field and micro-nano bubbles in the range of 5 to 30 μm work together to complete decolorization, deodorization, sterilization and efficient suspended-solids separation in one vessel. Total reaction retention time can be shortened to within 15 minutes.
Four advantages that follow from dropping the membranes
Against the traditional membrane method, CDOF leads on every dimension that matters to an operator. Pollutants are thoroughly degraded and mineralized rather than merely intercepted. The process uses no membrane, so no concentrated liquid is produced. Retention stays under 15 minutes. Decolorization, deodorization and sterilization happen simultaneously rather than as separate polishing steps. Together these resolve the concentrated-liquid problem at its source instead of relocating it.
There is a cost dimension too, and it is not mainly about energy. Once there is no concentrate, there is no evaporation-crystallization unit, no mixed-salt hazardous waste consignment, and no membrane replacement cycle to budget for. Plants that have lived with a dual-membrane line tend to find that the membrane budget, not the power bill, was the item quietly dominating their operating cost.
It is fair to ask what the trade-off is. Oxidation consumes energy and catalyst, and a leachate with a very high chloride load will still challenge any advanced oxidation process. The honest framing is not that CDOF replaces every membrane installation, but that it removes the particular failure mode that has made dual-membrane plants so difficult to operate: a waste stream with nowhere legitimate to go.
The direction of travel
Leachate treatment should not be a game of relocating pollutants elsewhere. It should be a determined push toward thorough purification. While the traditional membrane process stays stuck in the concentrate mire, the SINOKLE CDOF total-quantity membrane-free treatment process, with mature and reliable techno-economics, points the industry toward a greener and more sustainable way out. Saying goodbye to concentrated-liquid troubles and optimising both environmental benefit and operating cost is no longer an aspiration; there is now a workable answer.