Disinfection is a physical or chemical step placed after biological treatment and solids separation to inactivate pathogenic organisms before discharge or reuse. The MBBR itself does not reliably disinfect, so a dedicated downstream step is needed whenever the permit requires pathogen reduction — most commonly UV irradiation, chlorination or ozonation.
Disinfection options
UV disinfection exposes the effluent to ultraviolet light that damages pathogen DNA. It leaves no chemical residual and is effective if the upstream TSS is low (particles shield pathogens from UV). Chlorination (sodium hypochlorite, chlorine gas or chlorine dioxide) is widely used and effective but may form disinfection by-products that need to be managed. Ozonation is a powerful oxidant that also removes colour and some micropollutants, but at higher capital and operational cost.
The key link to the MBBR process is effluent quality: all disinfection methods work best on a well-clarified or filtered effluent. High TSS shielding (UV) or high organic demand (chlorine/ozone) reduces effectiveness, so good upstream solids separation directly determines disinfection success.
Disinfection comparison
Disinfection after MBBR (indicative — confirm per project)
| Parameter | Typical Value | Unit | Notes |
|---|---|---|---|
| UV | No chemical residual | — | Needs low TSS; compact footprint. |
| Chlorine | Residual possible | — | Widely proven; by-product risk. |
| Ozone | Strong oxidant | — | Also removes colour/micropollutants; higher cost. |
| All methods | Need good effluent quality | — | Upstream separation drives success. |
Frequently Asked Questions
Does an MBBR plant always need disinfection?
Which disinfection method is best after MBBR?
Why does upstream solids separation matter for disinfection?
Related Pages
Need MBBR Design Support?
Submit your wastewater data for a preliminary MBBR engineering assessment. Our team reviews every submission within 2 business days.