Three Wastewater Treatment "Heroes": MBBR, A/O & Fenton Oxidation

Every day, a large amount of sewage is generated from daily life and industrial production, containing organic matter, heavy metals and toxic pollutants that threaten the ecological environment and human health. Fortunately, sewage treatment plants have "purification experts" — MBBR, A/O, Fenton oxidation and other "black technologies", which work together to turn turbid sewage into up-to-standard reclaimed water. Let’s uncover their working principles.

I. MBBR: Mobile "Microbial Homes" for Efficient Purification

MBBR, short for Moving Bed Biofilm Reactor, builds movable "homes" for microorganisms to improve purification efficiency. Unlike traditional processes where microorganisms float in water or stick to fixed carriers, MBBR uses light fillers with a specific gravity close to water. Driven by aeration and water flow, these fillers swim freely in the tank, with microorganisms attaching to their porous surfaces to form a "biofilm".

These microorganisms decompose COD and ammonia nitrogen in sewage into harmless carbon dioxide and water. The "mobile homes" increase microbial concentration by 3-5 times, with strong impact resistance and no equipment blockage. It covers less than half the area of traditional processes and reduces operating costs by 30%-40%, widely used in municipal and industrial sewage treatment.

II. A/O: Anaerobic-Aerobic "Duo" for Nitrogen and Phosphorus Removal

A/O (Anaerobic-Aerobic Process) consists of two tanks to solve sewage eutrophication by removing nitrogen and phosphorus. In the anaerobic tank (no oxygen), anaerobic microorganisms decompose macromolecular organic matter into small molecules and release adsorbed phosphorus, laying the foundation for subsequent treatment.

Then sewage enters the aerobic tank, a paradise for aerobic microorganisms (usually with MBBR fillers to double efficiency). Aerobic microorganisms decompose small-molecule organic matter and complete denitrification — converting ammonia nitrogen into nitrate nitrogen and then into nitrogen released into the air. They also absorb dissolved phosphorus, which is separated by precipitation. Simple and low-cost, A/O is widely used in sewage treatment plants with stable denitrification and phosphorus removal effects.

III. Fenton Oxidation: Powerful "Crusher" for Refractory Pollutants

For refractory pollutants (antibiotics, dyes, etc.) in chemical, printing and dyeing or pharmaceutical wastewater that MBBR and A/O can hardly decompose, Fenton oxidation is the solution. It adds ferrous sulfate and hydrogen peroxide to sewage; under acidic conditions (pH 2-4), they react to produce hydroxyl radicals (·OH) with strong oxidation capacity.

Hydroxyl radicals break the molecular chains of refractory organic matter into degradable small molecules or even carbon dioxide and water. It also removes sewage chroma and toxicity, improving biodegradability. With fast reaction (1-2 hours), simple equipment and low investment, it is widely used as pretreatment or advanced treatment, with only a small amount of iron-containing sludge as a by-product.

IV. "Black Technologies" Working Together

In practice, these technologies work as a team: first, grids and grit chambers remove large impurities, then Fenton oxidation pretreats refractory pollutants; next, A/O-MBBR process deeply removes organic matter, nitrogen and phosphorus; residual pollutants are treated by Fenton oxidation again; finally, sedimentation, filtration and disinfection produce reclaimed water for irrigation, cleaning and cooling.

Conclusion

MBBR, A/O and Fenton oxidation are invisible guardians of water environment. They quietly convert dirty sewage into recyclable resources. With the improvement of environmental protection requirements, these technologies will become more efficient and energy-saving, protecting water resources and building a better ecological environment.