Cost-effective Operation of Wastewater Treatment Tanks

According to a study by the German Environment Agency , wastewater treatment plants are responsible for around 1% of Germany's total electricity consumption. What initially sounds like a very small percentage, however, offers a highly attractive savings potential from the point of view of individual wastewater treatment plant operators. One typical example of the savings potential in wastewater treatment plants is tank aeration. For example, state-of-the-art blower technologies and demand-driven control technology can energetically optimise the energy-intensive process of tank aeration and significantly increase a treatment tank's economic efficiency with comparatively little effort.

This starting point is particularly interesting for cities and municipalities. A glance at the energy requirements of municipal wastewater treatment tank operators shows that wastewater treatment plants in towns and municipalities account for a considerable share (around 20%) of total electricity consumption. Water treatment thus plays a crucial role when compared to schools, hospitals, water supply systems or other municipal and urban energy consumers.

However, the energy saving potential of wastewater treatment plants is often underestimated. Many wastewater treatment plants are still operated today with unregulated and inefficient aeration systems, which are responsible for a large part of the total electricity consumption. From today's point of view, however, the unregulated and non-demand-driven aeration in wastewater treatment plants is technically outdated. Highly efficient systems such as turbo blowers, rotary blowers and rotary compressors have been available on the market for several years. These not only offer higher efficiency in their own right and can be operated in a wide partial load range, but can even be operated together for optimum overall efficiency. This makes it possible to optimally respond to load changes in a tank's demand profile and to sustainably reduce energy costs.

In our guide, we will not only discuss the importance of aeration technology for the economic efficiency of wastewater treatment plants, but also point out the potential of demand-driven blower technologies. In addition, we will show how operators of wastewater treatment tanks can optimise their aeration tanks, from the initial analysis through to interlocking control.

The importance of aeration technology for the economic efficiency of wastewater treatment tanks

Every year, wastewater treatment plants consume a gigantic quantity of electricity amounting to around 4,400 gigawatt hours (GWh) of electrical energy . This is roughly the same as the annual output of a modern coal-fired power plant and equates to an annual CO2 production of around 3 million tons. Hence increasing the energy efficiency of wastewater treatment plants not only benefits operators – often the town/city or municipality – but also the environment.

When it comes to making the processes in wastewater treatment plants more energy-efficient, aeration is the main focus of consideration. In many cases, the energy requirement of the blowers installed in the aeration tank amounts to 60 to 80 percent of the total requirement. But what significance does aeration technology actually have for wastewater treatment plants?

Aeration tanks constitute the main cleaning stage of wastewater treatment plants. They use aeration systems to introduce oxygen from the air into the tank to promote the growth of aerobic microorganisms. These microorganisms break down organic pollutants and build up pollutant-absorbing activated sludge – this activated sludge is then separated from the treated wastewater in secondary treatment tanks and returned to the activated sludge tank or used as sewage sludge. In addition, the introduced oxygen is responsible for oxidising the ammonium nitrogen in the wastewater to nitrate and thus preparing it for removal by microorganisms.  

The energy consumption of wastewater treatment plants is usually expressed in kilowatt hours per year per PE, where PE stands for population equivalent. Typically, this value decreases as the size of the wastewater treatment plant increases, as economies of scale can be exploited. The German Environment Agency provides orders of magnitude for the electricity consumption of wastewater treatment plants that can be used for orientation purposes:

Size class 1 < 1,000 75 kWh/(EW x a)
Size class 2 1,000 – 5,000 55 kWh/(EW x a)
Size class 3 5,000 – 10,000 44 kWh/(EW x a)
Size class 4 10,000 – 100,000 35 kWh/(EW x a)
Size class 5 > 100,000 32 kWh/(EW x a)

It is interesting to note that, despite their lower specific energy requirements, the wastewater treatment plants of size classes 4 and 5 are responsible for around 87 percent of total electricity consumption. Wastewater treatment plants of this size represent only about 22 percent of the approximately 10,000 wastewater treatment plants, but are responsible for over 90 percent of the population equivalents.

In a typical wastewater treatment plant, biological treatment and secondary treatment form the largest part of the energy requirement. However, other process steps also require electrical energy:

  • Biological cleaning and secondary treatment 67%
  • Sludge treatment 11%
  • Flocculation filtration 8%
  • Infrastructure and other consumers 6%
  • Wastewater pumping systems 5%
  • Mechanical cleaning stage 3%

For this reason, the energy optimisation of waste water treatment focuses primarily on the biological treatment stage. A comprehensive analysis of 85 wastewater treatment plants in North Rhine-Westphalia showed that optimisation measures in the aeration tank were particularly effective: they created around twice the savings as measures taken in other areas.

There are manifold possibilities for technically and energetically optimising the biological cleaning stage. They range from the replacement of the blower system to the targeted improvement of operational management and the avoidance of pressure losses, to investments in highly efficient pump technology with low susceptibility to clogging.

Base load, peak load and low load – supply when needed with modern ventilation technology

The aeration tanks of municipal and industrial wastewater treatment plants are characterised to a large extent by a fluctuating load profile. Fluctuating quantities of waste water during the course of the day, changing precipitation levels, seasonal effects and varying degrees of pollution in the waste water result in a fluctuating demand profile, which can sometimes present sudden load changes. In addition, seasonal temperature differences must be taken into account, which also have an influence on the required amount of atmospheric oxygen in the activated sludge tank.

Modern concepts for the aeration of activated sludge tanks therefore aim to respond to a wastewater treatment plant's fluctuating demand profile with the most efficient aeration technology for each individual case. The advantages of turbo blowers, positive displacement blowers and rotary lobe compressors can thus be used in a targeted way to operate the ventilation system at efficient operating points, both at base load demand and at peak and low load demand.

While the turbo machine, for example, has excellent efficiency in terms of design, the positive displacement machine can be used in a wide partial load range with good efficiencies. If the advantages of both technologies are used, an aeration concept is created that can be ideally tailored to the individual requirements of the wastewater treatment plant and represents the best possible solution for the customer.

For this reason, AERZEN has developed a composite concept that enables bespoke and highly efficient oxygen supply at any time. The three-product range, also known by catchy name of "Performance³", enables operators of wastewater treatment plants to combine the best possible efficiency with maximum operational safety, reliability and economy.

The three series are specially designed for demand-driven supply of basic, peak and low loads. The AT and TB turbo blower series are characterised by outstanding efficiency in terms of design and are therefore primarily used for the base load range. To generate peak and low loads, AERZEN enlists the adjustable positive displacement blowers from the Delta Blower series and the rotary lobe compressors of the Delta Hybrid type.

The technical data of the Performance³ portfolio at a glance:

Technology Series Volume flow Pressure range Control range
Turbo blower AT and TB 300 – 16,200 m³/h 400 – 1,000 mbar 40 – 100 %
Positive displacement blower Delta Blower 30 – 15,000 m³/h -500 – 1,000 mbar 25 – 100 %
Rotary lobe compressor Delta Hybrid 110 – 9,000 m³/h -900 – 1,500 mbar 25 – 100 %
To enable targeted use of an individual series' characteristic advantages, it is worthwhile to optimise the control technology of the overall system. The main objective here is to find the optimum mode of operation for the activated sludge tank – by carrying out an in-depth analysis and evaluation of the oxygen demand – and to implement this with intelligent control technology.

Becoming an efficient wastewater treatment tank, step by step

To enable an evaluation of the energetic improvement potential of the aeration technology in wastewater treatment tanks on a sound basis, it is first necessary to carry out a detailed analysis of the existing aeration technology as well as the load profile. Extensive measurements and analyses make it possible to identify and quantify the potential of energetic modernisation measures. With the innovative AERaudit service from AERZEN, it is possible to optimise the usage and efficiency of blower stations in a targeted manner.

Following this analysis phase, the ventilation concept is implemented with the aid of a higher-level control system. Systems such as the innovative AERsmart machine control system from AERZEN are able to distribute air volumes across the technologies and their individual efficiencies in an ideal way, thus sustainably increasing the efficiency of the plant and bringing it close to its theoretical optimum. By simply optimising the control system, a considerable savings potential of up to 15% can be achieved. In addition to the proprietary Performance³ series, third-party products can be also controlled.

The unique feature of the AERsmart interlocking control system is its ability to distribute the required oxygen demand to the machinery at any time in such a way that each load point can be driven at the most efficient operating point. The controller uses the respective characteristic maps and efficiencies of the blowers and selects the combination of blower technologies that is ideally suited for the current operating point.

Resource-conserving wastewater treatment using Holzkirchen as an example

The example of the Holzkirchen wastewater treatment plant impressively demonstrates how thorough wastewater treatment can also be carried out in an environmentally friendly and resource-conserving manner. The wastewater treatment plant near Munich is responsible for around 50,000 PE and consumes around 500,000 kWh of electricity every year. By integrating the AERsmart integrated control system, the Holzkirchen wastewater treatment plant has succeeded in making ideal use of the advantages of various blower technologies. The result: An energy saving of around 10% and a reduction in annual electricity requirements of around 50,000 kWh.

Information & documents

You have questions? LET'S TALK

Find your regional contact and get personal advice.

Aerzener Maschinenfabrik GmbH (Headquarter)

Reherweg 28

31855 Aerzen

Phone: +49 5154 81-0

Fax: +49 5154 81-9191

Emmerthaler Apparatebau GmbH

Langes Feld 4

31860 Emmerthal

Phone: +49 5155 622-0

Fax: +49 5155 622-11

Aerzen Turbo Europe GmbH

Freibusch 2-4

31789 Hameln

Phone: +49 5151 92384 0

Aerzen Digital Systems GmbH

Hefehof 8

31785 Hameln

Phone: +49 5151 40302660

AERZEN Deutschland GmbH & Co. KG (Sales)

Reherweg 28

31855 Aerzen

Phone: +49 5154 81 4000

Aerzen do Brasil Ltda

Rua Dionysio Rito, n° 300, Distrito Industrial III, L14 Q D

13213-189 Jundiaí

Phone: +55 11 4612-2021

Fax: +55 11 4612 0232


Pezinská 18

901 01 Malacky

Phone: +421 34772 5531

Fax: +421 34772 5529

- Sales Office South West

Brückenstraße 2a

66740 Saarlouis-Fraulautern

Phone: +49 6831 76828 0

Fax: +49 5154 81 716410

Aerzen Argentina SRL

Domingo de Acassuso 4743

B1605BFO Munro, Buenos Aires

Phone: +54 11 47622351


Zone Industrielle 10, Avenue Léon Harmel

92168 Antony Cedex

Phone: +33 1 46741300

Fax: +33 1 46660061


A.De. Coninckstraat 11

3070 Kortenberg

Phone: +32 2 757 22 78

Fax: +32 2 7572283


Gewerbepark Morgenstern Im Alexander 4

8500 Frauenfeld

Phone: +41 52725-0060

Fax: +41 527250066

AERZEN Nederland B.V.

Bedrijventerrein Nieuwgraaf Fotograaf 3

6921 RR Duiven

Phone: +31 26 3197530


Typograaf 5

6921 VB Duiven

Phone: +31 88 9100050

ASP AERZEN Special Products B.V.

Bedrijventerrein Nieuwgraaf Fotograaf 3

6921 RL Duiven

Phone: +31 26 4463432

Fax: +31 26 4463049


Teollisuustie 15

FI-02880 Veikkola

Phone: +358 9 8194720

Aerzen Colombia S.A.S.

Centro Empresarial Metropolitano, Bodega 27, Módulo 2 (Autopista a Medellín, km 3,4) Cota, Cundinamarca,

Código Postal 250017 Código

Phone: +57 601 841 5730

Fax: +57 601 841 5730

Aerzen Austria Handelsges.m.b.H.

Gewerbepark Tresdorf II/1

2111 Tresdorf

Phone: +43 2262 74388

Fax: +43 2262 74399


Al. Niepodleglosci 18

02-653 Warszawa

Phone: +48 22 489 55 22

Fax: +48 22 489 55 27


Alíz Utca 4

1117 Budapest

Phone: +36 1 4392200

Fax: +36 1 4391922

AERZEN CZ s.r.o.

Hraniční 1356

69141 Břeclav

Phone: +420 519 326 657

Fax: +420 519 326658


Calle Adaptación 15-17

28906 Getafe (Madrid)

Phone: +34 91 642 4450

Fax: +34 91 642 2903


Rua Alfredo Lopes Vilaverde, 15B Escritório 3

2770-009 Paço de Arcos

Phone: +351 21 468 2466

Fax: +351 21 468 2467


Aerzen House, Langston Road

IG10 3SL Loughton, Essex

Phone: +44 2085028100

Fax: +44 2085028102


61 Woodlands Industrial Park E9 E9 Premium, #07-01

757047 Singapore

Phone: +65 6254 5080

Fax: +65 6254 6935

company profile

Aerzen Taiwan Machinery

Branch office of Aerzen Asia No.170, Ln. 879, Guangfu Rd., Bade Dist.,

Taoyuan City 33457

Phone: +886 3 366 6660

Fax: +886 3 366 6536

company profile


Östra Bangatan 20

19560 Arlandastad

Phone: +46 8 59441880

Fax: +46 8 59117209

Aerzen Scandinavia Norway

Raveien 320

3184 Borre

Phone: +47 33 29 22 12

Aerzen Scandinavia Denmark

Industrivej 2

5550 Langeskov

Phone: +45 78 72 92 90


108 Independence Way

Coatesville, PA 19320

Phone: +1 610 380 0244

Fax: +1 610 380 0278


980 Rue Valois, Suite 100 Vaudreuil-Dorion

J7V 8P2 Quebec

Phone: +1 450 424 3966

Fax: +1 450 424 3985

Aerzen México S.A. de C.V.

Cerrada Uniroyal # 18-A, Col. La Michoacana

Metepec, 52166

Phone: +52 722 235 9400

Fax: +52 722 235 9401

AERZEN MAKINE San. Ve Tic. Ltd. Sti.

IMES Sanayi Sitesi, C Blok, 308. SK, No:14, Y.Dudullu

34776 Ümraniye Istanbul

Phone: +90 216 420 00 32

Fax: +90 216 420 00 79

company profile

AERZEN Machines (India) PVT. LTD.

Plot No. E-115/116, G.I.D.C , Manjusar, Tal. Savli, Dist:

Vadodara-391 775 Gujarat

Phone: +91 2667 264-817

Fax: +91 2667 264-818

company profile


Via Raffaello Sanzio, 52

20021 Bollate (MI)

Phone: +39 02 6707 5277

Fax: +39 02 6707 5003


No. 655 Yuan Dian Road, Min Hang District

Shanghai 201108

Phone: +86 21 3323 9000

Fax: +86 21 3323 9199

Aerzen Romania S.R.L.

Sat Tunari Comuna Tunari Sos. De Centura nr. 25A

RO 077180 Judet Ilfov

Phone: +40 21 243 1883

Fax: +40 21 243 1884

Aerzen ME - FZE

DSO-DDP-Office-A1-222 Dubai Silicon Oasis P.O. Box: 341445


Phone: +971 0 432 431 66

Aerzen Adria d.o.o.

Varazdinska ulica, II odvojak 3

42000 Varazdin

Phone: +385 42 370 808

Fax: +385 42 370 018

Aerzen Australia Pty Ltd

57-59 Rodeo Drive

3175 Dandenong

Phone: +61 3 97067702

Fax: +61 3 9706 8584

Aerzen Chile SPA

Limache 3363 – Bodega 13

CP: 2520642 Viña del Mar

Phone: +56 32 235 8900

Aerzen Andina Perú SAC

Carr. Panamericana Sur Km. 29.5 Almacenes F-08 y F-09 ZI Megacentro – Altura Puente Vidu

 Lurin – Lima

Phone: +51 1 434 3831


Sheraton Housing 35 el moltaka el araby, Nozha elgedida. Appt - 7, 8, 9.


Phone: +20 2 22698855

Fax: +20 2 22696611

Aerzen AIRGAS (PTY) Ltd.

175 Domkrag Street, Robertville Ext. 1

Roodepoort, Johannesburg

Phone: +27 0 11 474 2193

Fax: +27 0 11 474 2321


4-Jinnah Cooperative Housing Society, Block 7/8, Main Sharea Faisal

75350 Karachi

company profile


14, Grevenon Str.

11855 Athens

Phone: +30 210-3423201-3

Fax: +30 210-3459967

Aerzen Adria d.o.o.

Varazdinska ulica, II odvojak 3

42000 Varazdin

Phone: +385 42 370 808

Fax: +385 42 370 018


Patraikou 21-23, Flat 101, Palouriotisa TK 1048, P.O. Box 25283

1308 Nicosia

Phone: +357 22441222

Fax: +357 22490641

L.A Engineering & Consulting Ltd

PO Box 2907, 25 Ha‘ela Street

40500 Even Yehuda

Phone: +972 9 8996544

Fax: +972 9 8996547


Ul. Archaritza 2A

4006 Plovdiv

Phone: +359 32 966 681

Fax: +359 32 966 702

Aerzen Adria d.o.o.

Varazdinska ulica, II odvojak 3

42000 Varazdin

Phone: +385 42 370 808

Fax: +385 42 370 018

Airgas Compressors (PTY) Nigeria Limited

3, Adebukola Omolabake Street, Off Eric Omobude Street, Ifako Bus Stop, Along Oworonsoki - Ogudu Expressway


Phone: 00234 0 1 843 4234

Aerzen Thailand Co., Ltd

36/60 Village No. 5, Phlu Ta Luang, Subdistrict, Sattahip District

20180 Chonburi

Phone: +66 0 38 020 090

Fax: +66 86 664 1337


Representative office of AERZEN ASIA PTE. LTD Floor 8th, Unit 802A, Dai Minh Convention Tower, 77 Hoang Van Thai, Tan Phu Ward, District 7, Vietnam

 Ho Chi Minh City

Phone: +84 28 3535 2760

Aerzen Turbo Co, Ltd

800 Jeongjung-ri, Osong-eup, Heungdeok-gu, Cheongju-si,

Chungcheongbuk-28220 Korea

Phone: +82-43-238-6500

Fax: +82 70 4170 4567

local partner: DEWA Projekt OÜ

Väike-Ameerika 15

10129 Tallinn

Phone: +372 50 39239


Teollisuustie 15

FI-02880 Veikkola

Phone: +358 9 8194720

Aerzen Australia - New Zealand Office

Unit 17a Hobill Avenue Wiri

2104 Auckland

Aerzen Australia Pty Ltd

57-59 Rodeo Drive

3175 Dandenong

Phone: +61 3 97067702

Fax: +61 3 9706 8584


Unit 6a, Castlecomer Business Park, Kilkenny Rd, Ballyhimmin

R95 Castlecomer, Co. Kilkenny

Phone: + 353 567807085

Aerzen Korea Ltd

Hyundai Terrace Tower, E-dong #608, 7, Yeonmujang 5ga-gil, Seongdong-gu,

04782 Seoul

Phone: +82 44 277 6500

Fax: +82 2 6463 0064

Aerzen Turbo Co, Ltd

800 Jeongjung-ri, Osong-eup, Heungdeok-gu, Cheongju-si,

Chungcheongbuk-28220 Korea

Phone: +82-43-238-6500

Fax: +82 70 4170 4567

Aerzen Arabia Ltd.

Abed Al-Mis’hal Tower 9th Floor, office 907, Building 3958, District 35514 Al Jubail, Kingdom of Saudi Arabia


Phone: +966 13 362 8826

Service Centre - Aerzen Arabia Ltd.

Rezayat Group Dammam Port Area, Dammam Kingdom of Saudi Arabia


Contact us