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Mechanical Mixers & Hyperboloid

Not all aeration is about oxygen — sometimes the job is to keep solids suspended and the basin homogeneous. Low-speed submersible and hyperboloid mixers move large volumes gently, with or without coupled aeration, for anoxic and equalisation duties.

At a Glance

What this aeration technology is, where it fits, and the numbers that define it.

Low-speedGentle, high-flow
AnoxicNo air, full mix
Floor-sweepKeeps solids up
CoupledMix + air option

Common Issues & How We Fix Them

The faults that undermine this technology in the field, and the engineering response to each.

Solids settling / sludge banks

What you see: Solids accumulate on the floor despite a mixer being installed.

Likely Causes & Solutions

  • Mixer undersized or mis-positioned: Re-calculate the thrust/velocity for the tank and re-aim the mixer to sweep the floor.
  • Dead zones behind structures: Add a second mixer or use a hyperboloid for full-floor coverage.
  • Wrong mixer type for the solids: Select for the solids loading and viscosity.

Rag and fibre binding the impeller

What you see: Mixer current rises and thrust drops as rag wraps the propeller.

Likely Causes & Solutions

  • Ragging on the propeller: Fit a ragging-resistant or self-cleaning impeller; improve upstream screening.
  • Frequent manual de-ragging: Move to a hyperboloid (floor-mounted, open) design that resists wrapping.
  • Screen bypass upstream: Fix the screening so fibre never reaches the basin.

Unwanted aeration in anoxic zones

What you see: Surface disturbance adds oxygen where denitrification needs none.

Likely Causes & Solutions

  • Mixer too shallow / too vigorous: Lower and slow the mixer to mix without breaking the surface.
  • Over-mixing strips the zone: Match mixing energy to suspension-only, not aeration.
  • Air ingress at the surface: Maintain submergence and gentle flow patterns.

Equipment & Options

Submersible mixers Hyperboloid mixers Anoxic mixing Floor-sweep Ragging-resistant

Right-sized mixing protects the biology — keeping solids in suspension for the bugs to work on, without adding oxygen where the process needs an anoxic environment.

Related Aeration Equipment

Specifying or fixing aeration?

Our engineers size aeration on real oxygen demand, select the right technology for your tank and load, and verify performance by test — from diffusers to blowers and controls.

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