MBBR Troubleshooting

Most MBBR problems are symptoms, not root causes. A rise in effluent ammonia, a drop in COD removal or carriers that stop circulating are all visible endpoints of an underlying imbalance — in the biology, the aeration, the hydraulics or the solids-separation step. Effective troubleshooting means working backwards from the symptom to the cause in a systematic order, rather than changing several variables at once and losing track of what actually helped.

A reliable diagnostic sequence starts with the basics that support the biofilm: dissolved oxygen, temperature, pH and alkalinity, and whether the carriers are genuinely moving and being scoured clean. Many “biological” failures are really an aeration or mixing problem, or an alkalinity shortage starving the nitrifiers. Only once those fundamentals are confirmed does it make sense to look at loading, biofilm thickness, and carrier condition. Because the biofilm responds slowly, changes should be made one at a time and given time to stabilise before the next adjustment.

Each page below takes a single, specific problem and works through its likely causes and the checks that confirm or rule each one out, so you can move from “what I observe” to “what to change” with confidence. The guidance is diagnostic and general; where a problem points to a design limitation rather than an operational one, an engineering review of the original sizing and configuration is the right next step.