Why Plants Choose an MBBR Retrofit

Wastewater flows keep growing, but new tanks cost time and money. An MBBR retrofit solves this problem in a simple way. You drop biofilm carriers into your existing tank, and the plant gains extra treatment capacity almost overnight.

Many plant managers face the same choice today. Regulations tighten, flows increase, and budgets stay flat. As a result, engineers look for upgrades that skip new construction. An MBBR media retrofit fits that need well.

How an IFAS Conversion Works

An IFAS conversion adds moving carriers to a conventional activated sludge basin. The tank keeps its suspended biomass. However, it also gains a fixed-film population that lives on the carrier surface. This hybrid setup is why engineers call it Integrated Fixed-Film Activated Sludge, or IFAS.

The carriers move freely through the water. Aeration or mixing keeps them in constant motion. Meanwhile, bacteria colonize every internal channel of each carrier. This combination boosts nitrification without touching the tank’s footprint.

For a deeper comparison of fixed-film and suspended-growth options, see our guide on MBBR vs activated sludge.

Sizing Your MBBR Media Retrofit

Correct sizing makes or breaks a retrofit project. First, engineers calculate the existing tank’s available volume. Then, they set a target fill ratio, typically between 40% and 60%. This ratio determines how much surface area the biofilm can use.

Next, the team checks aeration capacity. Carriers need enough oxygen and mixing energy to stay suspended. Therefore, some plants add supplemental blowers during the retrofit. Additionally, engineers confirm that clarifiers downstream can handle any extra solids.

• Measure existing tank volume and hydraulic retention time
• Set target fill ratio based on load and effluent goals
• Verify blower and diffuser capacity
• Install carrier retention screens at the tank outlet

Common Retrofit Challenges (and Fixes)

Retention screens sometimes clog during startup. Operators can fix this quickly by adjusting screen slot size and cleaning frequency. In fact, most clogging issues disappear once the biofilm matures and carrier movement stabilizes.

Uneven carrier distribution is another common issue. Dead zones form when mixing energy drops too low. Consequently, operators should monitor carrier movement visually during the first weeks. Similarly, they should track ammonia removal rates to confirm even biofilm growth across the tank.

Cold weather also slows biological activity. Even so, an MBBR retrofit still outperforms suspended growth alone in winter months, since the attached biofilm resists washout better than free-floating sludge.

Is an MBBR Retrofit Right for Your Plant?

An MBBR retrofit makes sense when flows have outgrown your current tanks. It also helps when nitrogen limits tighten and existing biomass cannot keep up. In short, this upgrade path avoids new concrete while still meeting stricter permits.

Peer-reviewed research backs this approach. According to a review of MBBR technology in municipal wastewater treatment, integrated fixed-film systems consistently improve nitrification without major civil works. This evidence supports what many plant operators already see in daily performance.

Before you commit, ask Oxy-Tech for a fill ratio and carrier recommendation based on your flow data. A short site assessment often reveals a clear, cost-effective path forward.