Robox Screw for the treatment of industrial waste

A.S.M.i.a., a company specialised in sewage and process fluids handling, has chosen Robuschi Robox Screw screw compressors (Gardner Denver Group) to optimise their oxidation processes.

Since the beginning of the eighties, ASMia has specialised in the treatment of sewage flows and process fluids, both civil and industrial. To meet the client's objectives, the company relies on a network of highly qualified experts and on the most innovative technologies on the market, thus ensuring maximum process optimisation. The integrated plant approach also allows for extreme flexibility in identifying the optimal solutions for the various needs in the sector. 

Through its A.S. Mortara holding, a 100% publicly owned company, it is the owner of a plant for the treatment of hazardous and non-hazardous liquid waste. The plant has a max. capacity of 108 thousand tons per year, which is equal to a population equivalent of approximately 86 thousand. The plant also treats civil wastewater from the public sewage, which originates in Mortara, in the province of Pavia. The environmental integrated authorisation issued by the Lombardy Region for this plant, which does not fall within the integrated water cycle, allows to boast at least 20 EWC (European Waste Catalogue) codes, for hazardous and non-hazardous waste, coming from chemical, pharma, food and beverage industries and more.


Robuschi technology in the Mortara plant

“Since the foundation of the company in 1982, we have always used Robuschi technology for the Mortara plant,” Ing. Marco Sordi, ASMia Srl Chief Operating Officer, explains. “Recently, however, we found we needed to optimise our oxidation processes. So we decided to fully replace our fleet of machines, which consisted of old Robox Evolution lobe blowers, with the Robox Screw screw compressors. These have a different configuration that allows us to make the most of the countless advantages, adapting to our process flexibility.”

Robuschi wastewater treatment plant

In 2016 the company installed 3 Robox Screw compressors in the Mortara plant. The following year, they added another two, and a sixth machine has been ordered for this year. All of them are to be installed outside and operate at a pressure of 600 mbar with capacities between 1,670 m3/h and 1,860 m3/h. The supply also includes a 2-year full service maintenance contract.

“Before, the lobe blowers were exclusively dedicated to the two lines that work in parallel. In reality, inside each line we had some sub-lines, with oxidation sub-tanks. So we decided to streamline and optimise the supply system by changing the air supply method. Now, each oxidation tank in the plant has a dedicated blower, whereas previously a blower would distribute the air between multiple tanks. This also allows us to have a dedicated oxygen control system for each machine, whereas before we only had one control downstream,” Ing. Barbara Crotti, A.S. Mortara Spa Chief Operating Officer, continues.


Robox Screw  Blower at Work Robox Screw  Blower installed in a wastewater treatment plant

One technology, multiple advantages

ASMia ultimate goal was to optimise the performances of the wwt station in terms of quality of the effluents and energy consumption. This is the reason why the company decided to rely once more on Robuschi, who again proved to be a reliable partner, able to meet every specific need. From an initial power consumption monitoring phase, which lasted approximately two months, we noticed an approximately 15-20% saving in consumption. 

The new machines also ensure a low noise impact. This latter characteristic is extremely important because the plant is located near a built-up area. “One of the specifically required characteristics was the containment of noise emissions within 70 dbi,” Barbara Crotti points out. “Also for this application, Robox Screw proved to be the best choice: the compressor is fitted with a soundproof noise enclosure that contains these noise emissions, making it possible to comply fully with the standards imposed.” 

Robuschi Robox Screw compressors installed in the Mortara plant are also fitted with the HMI controller to modulate the process directly. Initially they were operating in master mode with oxygen control probes; they were subsequently modified with slave functionality to optimise the process. This allows the machines to react in the best possible way according to the needs of the system and they adapt with greater flexibility to processes.

From the perspective of continuous improvement, once the sixth compressor has also been installed, A.S.M.i.A aims to install dedicated systems for the online detection of ammonia, to evaluate the air supply regulation no longer measuring the oxygen but rather the ammonia at the outlet. This gives us the possibility of obtaining significant additional benefits especially in the energy savings as well as having greater control of the oxidation processes.
“Another additional benefit arising from the use of Robox Screw compressors is the simple machine maintenance and management. This allows a certain autonomy, also thanks to the numerous utilities offered, savings in terms of time and resources dedicated to the care and maintenance of compressor units. This additional characteristic of Robuschi’s compressor unit allowed us to express an extremely positive judgement in terms of LCC, by evaluating the whole set of parameters, such as the initial investment, operational costs and reliability, maintenance costs and related safety,” Ing. Marco Sordi, ASMia Chief Operating Officer, concludes.



For a few decades, Robuschi has been a fundamental partner for the wastewater treatment sector. Lobe blowers, screw compressors and centrifugal pumps offer efficient and eco-sustainable solutions for a wide variety of applications.

Available in configurations up to 2,500 mbar(g) and up to 1,000 mbar(g) with a maximum capacity of 10,100 m³/h, Robox Screw is an oil-free high-yield screw compressor unit that combines the consolidated characteristics of simplicity and reliability of the well-known Robox blower units with innovative components and design.

The unique profile of Robuschi rotors optimises the capacity-pressure ratio thanks to the maximum internal compression yield and to the reduced number of revolutions, thus increasing the efficiency of the Robox Screw unit. This characteristic, together with the reduced maintenance costs, allows a rapid return on the initial investment, 2 years on average, which varies depending on the application and the operating conditions. Also thanks to the innovative rotor profile, the compressor guarantees low noise emissions, allowing for installations in the most diverse fields of application. Another main feature is the extreme simplicity of installation, maintenance and use, thanks to a considerable reduction in the number of parts in the compressor itself, as well as its great flexibility in use. 

In wastewater treatment plants, energy consumption represents more than 50% of the annual cost. For this reason, the Robox Screw range offers the best response to the need for cost reduction, because it makes it possible to save between 15% and more than 30% compared to other technologies. The Robuschi unit provides the maximum quantity of air with the lowest power consumption, thanks to the RSW internal compression. This makes the unit extremely versatile both for continuous and intermittent use, as well as the best solution for the various technologies used in wastewater treatment plants. In addition to this, thanks to the capacity to operate with pressures in excess of 1 bar, Robox Screw can supply the wastewater collection tanks at great heights, thus combining the best use of urban spaces with a low level of noise pollution.