Effluent Already Below 200 mg/L COD and Still Failing Consent: The Case for KLE-HEC-200-A20

There is a band of wastewater that gives treatment engineers more trouble than it should: COD under 200 mg/L, already through biological treatment, still above the discharge or reuse limit. It is too clean for the economics of bulk oxidation to look attractive and too dirty to ignore. Conventional media perform badly here for two reasons — the organics are too dilute to make good use of the ozone you dose, and in high-chloride streams the chloride quietly occupies the active sites.

KLE-HEC-200-A20 was developed for that band. It is a precious-metal-loaded heterogeneous ozone catalyst from SINOKLE, built for biochemical tail-water polishing, reclaimed-water reuse and low-concentration but highly toxic waste liquid, and it is normally delivered as part of a package rather than as loose media.

What the carrier is doing during the reaction

The carrier is a porous inorganic body prepared by staged temperature-controlled sintering followed by atomic-deposition precious-metal loading, giving a specific surface area above 250 m2/g with transition-metal and precious-metal sites sitting next to each other. A CeO2 protective layer is applied over the top specifically to stop chloride passivation. The precious metal pulls down the activation energy for ozone decomposition, so hydroxyl radicals form quickly — oxidation efficiency runs 2–5 times that of an ordinary silica-alumina catalyst.

That matters for the pollutants typical of this band: trace antibiotics, halohydrocarbons, residual dyes and humic substances. Radical attack breaks the macromolecular bonds directly rather than partially oxidising them, and the B/C ratio improves as a side effect, which is useful when the water is heading back into a biological stage or into reuse. A super-hydrophilic surface film keeps suspended solids, colloids and oil out of the micropores, and the cerium layer is what allows long-term running in high-chloride, high-salinity water.

Parameters to put in the specification

• Form: gray-black spherical granules, 2–4 mm, customisable.
• Strength: compressive strength ≥1 MPa (single-granule compression ≥100 N), annual wear ≤0.3%.
• Pore structure: pore volume ≥0.3ml/g, specific surface area >250 m2/g, bulk density 0.7t/m3.
• pH window: 3–11.
• Performance: ozone decomposition utilisation ≥98%; comprehensive removal ≥65% at incoming COD<200 mg/L; colour removal ≥95%.
• Life: more than 5 years under standard conditions, renewable by acid washing.
• Duty: 24 h continuous treatment systems.

Three plants worth studying

Landfill leachate after two-stage biochemistry

Effluent COD sat at 150–190 mg/L with heavy colour and residual humic substances, and the plant was failing its discharge standard. At 100 mg/L ozone, 5 g/L catalyst and 30 min retention, COD removal reached 68% and effluent COD came out at 60 mg/L with colour inside 5-fold. The knock-on benefit was at the membranes: NF and RO load dropped and membrane life extended, which is where most of the money was.

Pharmaceutical API tail water

An A/O plant was producing COD 160–190 mg/L carrying trace bacteriostatic antibiotics, with biodegradability so poor that little else could be done with the water. At 120 mg/L ozone, 6 g/L catalyst and 35 min retention, trace-antibiotic removal was 96%, effluent COD held at <60 mg/L, and B/C improved from 0.12 to 0.36 — enough for the water to go back into workshop equipment washing.

Refining combined effluent for cooling make-up

After flotation and biological treatment, a heavy-oil power plant's combined wastewater sat at COD 140 mg/L with trace colloids and dissolved oil, and missed the circulating-cooling-water reuse specification. At 80 ppm ozone, 4 g/L catalyst and 25 min retention, effluent came out at COD <50 mg/L with colour below 10-fold, and the plant cut its fresh-water intake.

Why chloride resistance is the real differentiator

On high-chloride wastewater, ordinary precious-metal media commonly lose more than 30% of their activity within months because chloride complexes onto the active sites. In continuous service over half a year, the CeO2-protected A20 showed activity decay of around 7%. For chemical parks, pesticide producers and coastal sites, that single number usually decides the media choice, because regeneration intervals and replacement cost both flow from it.

Process integration and operating cost

The standard train is a CDFU swirl dissolved-air flotation (CDFU) stage to strip suspended solids and trace floating oil, feeding CDOF ozone catalytic oxidation charged with the A20 catalyst. Everything is skid-mounted and factory prefabricated, so a retrofit of an existing wastewater station needs pipe and electrical connections only — no production stoppage. For reuse duty the train extends to two-stage CDFU pre-treatment, the catalytic unit, and sand-filter polishing, with online COD, ozone concentration, flow and pressure feeding automatic control of dosing, backwash and slag discharge.

Cost-wise the picture is: ozone utilisation ≥98% keeps generator power down at equal effluent standards; media lasts beyond 5 years and is acid-wash regenerable, so annual amortisation stays predictable; wear of ≤0.3% a year means little replenishment and little hazardous waste; and chemical dosing for flocculation and decolourisation drops by more than 70%. Single-unit purchase price is higher than an economy catalyst, but once ozone power, media loss and hazardous-waste disposal are added together the medium-term total is lower.

SINOKLE has run this package in landfill, pharmaceutical, petrochemical and fine-chemical service under high-tech enterprise, specialised-innovation, ISO three-system and multiple invention-patent qualifications, with water testing, process customisation, installation, commissioning and catalyst regeneration available from one team, so long-term O&M stays with the same people who sized the unit. Typical extended duties include dyeing and leather decolourisation, fine-chemical and coking streams carrying halohydrocarbons and PAHs, power and metallurgy circulating water, and VOC absorption liquor.