Landfill Leachate at 20000 mg/L COD: What a Silica-Alumina Catalyst Does Differently

Most catalytic ozone media are designed for comfortable water: near-neutral pH, moderate salinity, a few hundred milligrams per litre of COD. Real industrial streams are not like that. Landfill leachate arrives with salinity and humus that defeat biological treatment. Pharmaceutical synthesis wastewater swings between pH 2 and pH 11 within a shift. Refinery combined effluent carries residual gum and dissolved oil after flotation. In each case the catalyst is asked to work at the edge of its envelope, and in each case the usual failure is the carrier, not the active metal.

KHC-F2001 from SINOKLE was built around a silica-alumina composite oxide carrier instead of a carbon or simple alumina one, and that single choice explains most of its behaviour in harsh service.

Why the carrier decides the outcome

A sol-gel composite sintering route produces the silica-alumina substrate, and on its surface sit a large population of Lewis and Bronsted dual-acidic active sites. Manganese, iron and cobalt are loaded as the composite catalytic components. When ozone passes through, the surface accelerates its decomposition into hydroxyl radicals, and those radicals break the stable bonds of macromolecular pollutants — humus, antibiotics, halogenated hydrocarbons, dye intermediates — rather than nibbling at the edges of them.

The practical consequence is that COD, colour and biological toxicity all fall together, and biodegradability improves, so whatever sits downstream — a biological stage, a membrane skid — sees a lighter load. Silica-alumina is intrinsically resistant to acid, alkali and temperature. With a pH tolerance of 2–12 and no precipitation or loss of active components, the medium runs in exactly the water that kills ordinary media, and it does not leach heavy metals into the effluent.

Specification summary

• Form: red-brown spherical particles, 3–5 mm, customisable on request.
• Carrier: modified silica-alumina composite oxide with multiple metal active components.
• Strength: single-particle compressive strength ≥120 N, annual wear rate ≤1%.
• pH tolerance: 2–12, resistant to strong acid and strong alkali.
• Performance: ozone decomposition utilisation ≥95%; comprehensive COD removal ≥75%; colour removal ≥98%.
• Life: 5–8 years under standard conditions, regenerable after activity decay.
• Duty: high-salinity, high-COD, extreme acid-base wastewater on 24 h continuous high-load operation.

Three very different plants

Municipal landfill leachate

Raw leachate COD reached 20000 mg/L, with high salt content, heavy humus and biodegradability so poor that biology alone was never going to close the gap. The plant ran biochemical pre-treatment followed by KHC-F2001 silica-alumina ozone catalytic oxidation at 500 mg/L ozone, 10 g/L catalyst and 60 min hydraulic retention. The catalytic unit removed 99.5% of the COD and final system effluent stabilised below 100 mg/L, comfortably inside the domestic waste leachate discharge standard. Membrane load dropped, element life extended, and cleaning frequency fell.

Pharmaceutical antibiotic synthesis

Synthesis wastewater carrying bacteriostatic refractory organics, with pH swinging across 2–11 and raw COD at 8000 mg/L; conventional biochemistry could not hold steady. At 300 mg/L ozone, 8 g/L catalyst and 45 min retention, antibiotic-substance removal was 99% and effluent COD was held within 200 mg/L. The notable point was not the absolute number but the stability — even with violent influent pH swings, effluent quality showed no obvious decay, which is what the downstream biological system needed.

Petrochemical combined wastewater retrofit

Refinery combined production wastewater, already through CDFU cyclonic dissolved-air flotation pre-treatment for floating oil and suspended solids, still carried residual gum and dissolved oil that pushed COD and colour over the limit. Adding a KHC-F2001 ozone catalytic oxidation unit at 120 ppm ozone, 6 g/L catalyst and 30 min retention dropped raw water COD from 350 mg/L to below 50 mg/L and colour from 200-fold to within 20-fold, meeting the reclaimed-water reuse standard directly and closing the loop on site.

Where else it gets specified

Fine-chemical and coking streams with halogenated hydrocarbons and polycyclic aromatics, where the objective is toxicity reduction ahead of a biological stage. Dyeing and leather effluent with high colour from dyes and tannins, where cutting decolourant dosing also cuts chemical sludge. Power and metallurgy circulating cooling water, where oxidising organic slime and microbial precursors extends the cycle and reduces scale inhibitor and biocide demand. And VOC absorption liquor, where oxidising the dissolved volatile fraction lets the liquor be recycled instead of discharged.

Flowsheet and economics

For high-oil industrial wastewater the standard configuration is a high-efficiency coalescence oil remover plus CDFU cyclonic dissolved-air flotation as purely physical pre-treatment, then CDOF ozone catalytic oxidation charged with KHC-F2001. Removing oil physically first matters: oil films on the catalyst surface are the fastest way to lose active area. For high-salinity or extreme acid-base water the front end simplifies to two-stage CDFU cyclonic dissolved-air flotation for solids removal ahead of the same catalytic unit, skid-integrated and compact for large park installations.

The skid ships assembled and debugged, so a retrofit connects piping and controls without shutting the main production unit, and there is no large civil structure to build. Instrumentation covers online water quality, ozone concentration, flow and pressure, with influent, catalytic reaction, air-water backwash and slag discharge under automatic control and remote monitoring, so no dedicated operator is needed. Economically the argument rests on four things: ozone decomposition utilisation ≥95% keeps power down; a 5–8 year life with easy regeneration cuts media replacement; low wear reduces routine top-up; and the front-end physical stage recovers waste oil, turning part of the treatment cost into revenue.