Is Your Wastewater Treatment Plant Aerator Wasting Electricity? These Are the Most Common Setting Errors

In many WWTP systems, electricity bills that seem to “quietly keep increasing” are often not caused by oversized treatment capacity, but because the aeration system is operating inefficiently. And the problem is, this issue is often not immediately visible.

The blower is still running, bubbles are still appearing, and outlet parameters may still occasionally remain within acceptable limits — so everyone assumes the system is operating normally.

In reality, however, aeration is one of the largest contributors to OPEX in biological WWTP systems. If the settings are incorrect, inefficiencies can occur every single day without being noticed. It is not only electricity costs that increase, but also blower lifespan becomes shorter, diffusers foul more quickly, and biological treatment performance does not necessarily improve.

If you want to first understand the basic function of aeration, you can also read the discussion about types and functions of aerators in wastewater treatment. However, in cases like this, the main issue is usually not the “type of equipment,” but rather how the system is operated.

1) Over-aeration: DO is too high, electricity is wasted, and results are not necessarily better

The most common mistake is the mindset: “the more air supplied, the safer the process.”

As a result, blowers are allowed to run continuously at full capacity, dampers are opened too far, or DO setpoints are maintained excessively high without clear process justification.

In many activated sludge applications, however, excessively high DO levels do not necessarily provide proportional performance improvements. Instead, the following occurs:

• blower electricity consumption increases,
• shear forces on flocs may increase,
• anoxic zones may be disrupted (in nitrification-denitrification systems),
• operational costs increase without meaningful benefit.

Practically speaking, if your process targets can already be achieved at DO levels of 1.5-2.0 mg/L, but the system is forced to maintain 3.5-4.0 mg/L, then you are effectively “buying air” at a higher cost than necessary.

2) Diffuser fouling: blowers work harder while oxygen transfer efficiency actually declines

Many operators still see bubbles coming out and assume the aeration system is functioning normally. This is a classic trap.

When diffusers begin fouling (due to scaling, biofilm, oil, or solids blockage), system pressure increases. As a result, blowers must work harder to push air through the system. More critically, oxygen transfer efficiency decreases.

This means:

• electricity consumption increases,
• the actual dissolved oxygen transferred into the water decreases,
• DO becomes unstable,
• operators tend to increase blower output again as a “quick fix.”

The end result? Double losses.

If this condition continues, the system becomes similar to a car whose accelerator pedal is pressed harder while the air filter is clogged. The engine works harder, but performance becomes inefficient.

That is why routine operation and maintenance are not merely formalities. If you are currently improving your field SOPs, the discussion about WWTP operation and maintenance to remain efficient and compliant is highly relevant as a reference.

3) Blower mismatch: capacity exists, but control is not precise

Another common issue is when blower capacity does not match the actual process demand.

Examples include:

• the blower is oversized for daily loading conditions,
• the system only operates in ON/OFF mode without flexibility,
• turndown capability is poor,
• air distribution between basins is uneven.

Under these conditions, operators are often forced into two equally poor choices:

• blower ON → too much air supplied,
• blower OFF → DO drops too quickly.

As a result, the system oscillates, energy consumption becomes inefficient, and biological stability decreases.

This commonly occurs in systems originally designed conservatively for peak loading, but which operate daily under partial load conditions. From a design perspective the system may appear “adequate,” but from an OPEX perspective it can become expensive.

4) DO control is not optimized: sensors exist, but they do not truly control the process

Many WWTPs already have DO meters installed, but that does not automatically mean they have effective DO control.

Common problems include:

• DO sensors are not routinely calibrated,
• sensor locations are not representative,
• setpoints are not adjusted according to load variations,
• blowers remain manually operated even though sensors are installed,
• operators only monitor the numbers instead of using them as actual control parameters.

As a result, DO becomes merely an indicator rather than an energy-saving control tool.

When DO control is properly implemented, the system can adjust air supply according to actual process demand — not based on assumptions.

Simple calculation: how much money leaks every month?

Assume one aeration blower has a power rating of 15 kW, operating 24 hours per day.

• Daily energy consumption = 15 kW × 24 hours = 360 kWh/day
• If the industrial electricity tariff is assumed to be IDR 1,500/kWh
• Then daily electricity cost = 360 × 1,500 = IDR 540,000/day
• Monthly cost ≈ IDR 16.2 million/month

Now imagine that due to over-aeration, diffuser fouling, or poor DO control, the system is actually wasting 20% energy.

• Energy waste = 20% × IDR 16.2 million
• = IDR 3.24 million per month
• = nearly IDR 38.9 million per year from only one blower

If 2-3 blowers are operating, this quickly changes from a “small inefficiency” into a major OPEX burden.

The problem is often not the equipment, but how the system is operated

If your WWTP aerator system feels electricity-intensive, do not immediately blame the blower brand or rush to replace equipment.

In many cases, the real root causes are:

• DO setpoints that are too aggressive,
• diffusers beginning to foul,
• blower capacity mismatched with actual operating conditions,
• and aeration control systems that remain manual or imprecise.

In many situations, operational optimization and system audits can generate savings far more quickly than investing in new equipment.

If you are currently evaluating an existing WWTP system or want to ensure your aeration design does not create excessive operational costs from the beginning, working with an experienced industrial WWTP contractor is significantly safer than focusing only on low initial CAPEX. Because in real operations, the most expensive cost is often not the equipment itself — but the cost of poor settings that are paid every month.