Historically, water treatment plants have been using positive displacement (PD) blower technology for their aeration processes.
Consuming a lot of energy, and demanding considerable attention for maintenance and upkeep, they some cases accounted for up to 50 per cent of power consumption.
A major improvement in water treatment technology came early this century, with the introduction of single-stage, oil-free, direct drive turbo blowers with air-foil bearings. More and more wastewater treatment plants are now embracing the new technology and enjoying its benefits.
It requires a lot of work to change the usual course of events and to start thinking outside of the standard PD blower box. Extensive research and information analysis is required, including risks minimisation, comparison of efficiencies provided by different technologies and reviewing maintenance costs.
Among alternative technologies, wastewater treatment companies are looking at: turbo blower compressors, rotary lobe compressors (also known as hybrids), high speed and multistage centrifugal blowers, positive displacement screw blowers, and modern positive displacement three-lobe blowers. All of these models promise energy efficiency and energy savings.
In 2013, Australia's largest water utility, Sydney Water, purchased three GE Turbo blowers to upgrade their PD blowers at Warriewood WWTP. Warriewood Wastewater Treatment Plant serves an area of 25 square kilometres or over 63 000 people. The local population is expected to grow by around 11,000 over the next two decades and the upgrade was performed to cater for the population growth.
Sydney Water is committed to energy efficiency. They run a number of energy efficiency programs, providing savings over 15,000 MWh per year. One of the programs is to minimize power used in the aeration process at wastewater treatment plants.
GE Turbo blowers were purchased in line with this program because of their high efficiency and turndown. Also, Sydney Water requires all equipment to be supplied with standard off the shelf hardware, that is, they have a no 'black box' controller policy. One other feature Sydney Water required was for the ability of the turbo blowers to run together with existing PD blowers. The GE TurboMax blowers met all these criteria.
After a competitive tender process between turbo blower supply companies meeting Sydney Water's requirements, three GE Energy Turbo Blower Packages model RH-07506SSAA rated for 75 HP, were ordered.
The blowers were installed in May 2013 and Sydney Water retained a PD blower at Warriewood to allow for direct efficiency comparisons. Actual measurements shown in the table below confirmed energy savings of 16 per cent to 24 per cent were achieved depending on flow rate.
The retained PD blower was completely rebuilt to new blower tolerances. As such the turbo versus PD blower comparison is a true comparison, not one where the PD is well worn.
Sydney Water control specialists state that they value ease of installation (Modbus communications require no hard wire back up and deliver all necessary values and control parameters, allowing savings on installation costs).
Their service technicians appreciate the low maintenance, low noise and virtually no vibration and the fact that GE turbo blowers can be installed in parallel with PD blower on a common manifold.
Sydney Water is now looking at retiring all its continuous operation PD blowers and replacing them with high-speed turbo blowers.
Depending on the requirements, return on investment on the Turbo blowers' installation maybe less than 2 years and longevity is predicted to be at least 20 years, while energy savings reach up to 30 per cent.
In addition to the energy savings, turbo blowers offer other advantages.
They are compact, lightweight and have minimal installation requirements. In contrast to PD blowers, no civil works such as plinths and foundation bolts are required and the comparatively smaller footprint means direct replacements are often straightforward.
Low noise and vibration levels mean comfort both for workers and for people living in the surrounding area.
Turbo units are durable, reliable, and require minimum maintenance - apart from monthly checks and clean-ups of filters and replenishing of water (water cooling on 200 HP and above models) they require no attention and no dedicated personnel.
Controls on Turbo Blowers are of Allen Bradley or KEB manufacture which means spares and technicians are available worldwide. For harsh Australian conditions, environmental durability is also of importance; GE Turbo Blowers are capable of withstanding weather extremes and are rated for duty at 55°C.
Bump-type air foil bearing design ensures the blower delivers greater stability and load bearing capacity compared to leaf-type air foil bearings and can provide instant stop start operation. In case of a soft failure (if a bearing failure occurs, the bearing foils restrain the shaft assembly from excessive movement), only bearings and shaft surfaces are affected, and they are inexpensive to replace.
They also do not require lubrication.
The last question remains – with the initial asset price of turbo units somewhat higher than that of a standard PD blower, can you afford it? With the installation and energy savings to be made and major maintenance costs eliminated, life cycle costs are often significantly lower.
Contact HNW today to find out how you can save money at your treatment plant.