Low Speed surface aeratorHigh Speed surface

aeratorSubmersible low speed

aerator and mixerSurface aspirator aerator Submersible aspirator Coarse bubble diffusers Fine bubble diffusers

municipal

industrial

small & medium

large

low (< 5m)

high (> 5 m)

variable Fixed

Floating

Fixed

Floating

$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $

relative rank + + + + + + + + + + + + +

SOTR** in kgO2/kWh (usual range)

clean water/sewage corrective factor 0.7 0.7 0.65 0.65 0.65 0.6 0.5

AOTR** in kgO2/kWh (usual range)

Fixed grids

Liftable grids

Fixed grids

Liftable grids

> 15 years > 10 years > 10 years ? ?5 - 8 years

(membrane renewal only)5 - 8 years

(membrane renewal only)

product LTF AQUAFEN SOFIE - - DISC'AIRAQUADISC

AQUATUBE

Material availability

Rotor in reinforced polyester + fiberglass

OR stainless steel OR painted steel

Float in reinforced polyester + fiberglass

OR stainless steel

Stainless Steel 304L

OR stainless steel 306L- -

EPDM membrane

+ ABS support

EPDM membrane

+ Polypropylene support

(AQUATUBE body and adaptor

in 1-piece mold)

* with high water level, fully covered** SOR: Standard Oxygenation Ratio ; AOR: Actual Oxygen Ratio

Air diffusion

Suitable

WWTP size

Suitable

liquid level /

liquid depth

COMPARISON OF MOST COMMONLY USED AERATION SOLUTIONS IN WASTEWATER TREATMENT PLANTS

Self-Aspirating AeratorsMechanical aerators

Pictures of each product type

Equipment cost

Suitable effluent

origin

Average life duration

Maintenance easiness

Oxygenation

efficiency

(indicative values)

Europelec educational kit - strictly confidential

EUROPELEC

TO GO FURTHER

Europelec educational kit - strictly confidential

Being very reliable once installed and functioning, mechanical aerators request less maintenance than diffusion systems. Moreover, curative operations (in case it happens) are much easier since machines can be pulled or carried with a crane. On the contrary, diffusion tanks request to be emptied and the wastewater plant stopped to operate maintenance. Liftable systems for fine/coarse bubble systems make the maintenance or trouble much easier to manage and are more than advised.

Life duration is an estimation based on what EUROPELEC usually notices empirically. Life duration of diffuser systems is usually shorter than mechanical aeration. However, only the membrane needs to be replaced, which make the renewal significantly lower investment than a new installation. No much data regarding aspirator life duration, but probably close to 10years such as submersible aerators.

Indicative pictures only. The indications in the chart do not specifically refer this specific brand model showed.

For more information about EUROPELEC products, please refer to EUROPELEC portfolio presentation or reach your EUROPELEC contact.

In its chart, EUROPELEC gives commonly used corrective factor values for each system, submitted to the same configurations.

To compare real efficiencies between each system, we should analyze the AOTR. Mechanical aerators performance is less impacted by the "actual wastewater" conditions than fine bubble aeration systems (which means the corrective factor is closer to 1 for mechanical aeration than for diffusion). However, when consultants design aeration tanks, they take into account the corrective coefficient in their calculations. Therefore, they speak and request for quotation in Standard conditions (since manufacturers only guarantee performance in those conditions).

The different systems presented are specialized solutions for wastewater treatment; they are all compatible with typical municipal effluent type. However, you should be careful using diffusers with industrial effluent; the membrane elements might react with the components present in the effluent (grease, oil, etc.) or the membrane is more subjected to clogging. Using mechanical aerators can often avoid this risk.

Theoretically speaking, all the systems can go in every size of plants. However, it can be noticed in practice:- on the one hand, air diffusers for small installations are not very cost effective in terms of investment;- on the other hand, systems with lower oxygenation efficiency (such as aspirators) are practically avoided in large installations for energy consumption (then operational costs) reasons.

SOTR = AOTR / "Corrective factor" , where "corrective factor" depends on temperature, pressure, dissolved oxygen saturation concentration, solid suspension concentration in the wastewater, etc.

Depending on the mechanical aerator power, it can function until 5 meters deep. With an additional chimney, low speed fixed aerators can go even until 7m.Surface aerators are usually more suitable than diffusers in shallow water (less than 4-5meters).For variable water, high speed floating aerator is the best adapted surface aerator. In case of large variation, submersible aerators or diffusers (bottom of the tank) might be better adapted.

Equipment price depends on many criteria (power, material, manufacturer, product quality, distribution channel, exchange rate,...) This chart gives a comparison of initial cost of the equipment (in equivalent conditions). Generally, due to blowers and air piping needed, fine bubble diffusion system is the most expensive equipment for the investment part.

Oxygenation efficiency ranking is based on the state of the art in sewage field. Independent public laboratories have already published about aeration systems in WWTP and obtain the same ranking order as the one presented. The chart show 2 important criteria: SOTR and AOTR, which are the efficiency rates of the equipment respectively in standard (clean water) and actual (on-site sewage water). They are linked by the relation: