In May this year, the Hotel Lafodia, situated on the Croatian island of Lopu, northwest of Dubrovnik, was facing a particular problem. The 600-person hotel needed a wastewatertreatment plant installed on site, but had no existing connection to the municipal sewer tunnel system. Historically, wastewaterfrom the hotel had been pumped down a pipeline directly into the Adriatic Sea. However, concerns over safety for the hotel guests swimming there, combined with more rigorous national legislation regarding the disposal of wastewaterinto the sea had led the hotel management to consider a new solution.
Remote location
Because of the hotel's remote location, there was no way a link could be established with the municipal wastewatercanal system, which meant a bespoke wastewatertreatment plant was the only realistic option. An additional consideration were the very strict noise limits set by the hotel's management, who were keen to ensure that the installation should take as little time as possible and not disturb hotel guests or anyone living in the neighbouring houses.
The contracting company on-site, ISEA d.o.o. consulted with local pump specialists VIS-trgovina d.o.o, who are Tsurumi's Croatian dealer, based in Zagreb. After considering all the options, ISEA d.o.o. came up with an intelligent solution involving the creation of a system of modular PE (polyethylene) sewage treatment tanks, where they installed six 0.75 kW Tsurumi submersible aerators. Predrag Mlinar, Research & Development Manager for ISEA d.o.o. explained that his choice of Tsurumi pumps for the installation was an obvious one:
“We were looking for an aerator that would be cost-effective for us and also meet the noise limits imposed on us by the client. The Tsurumi pumps were a perfect match for what we needed,” he said. “Although the project ran for two weeks in total, the installation of the TRN aerators only took an hour to complete.”
Modular build
By opting for a modular build installation, the wastewatertreatment plant has several advantages for the hotel. First and foremost it offers complete flexibility. In winter when there are fewer guests staying in the hotel, the wastewatertreatment plant can operate with just one of the modular PE tanks running. In the height of summer when the hotel is full, the plant can operate at full capacity with all tanks in use. This is an important factor for energy savings because the system can be adjusted to the most energy-efficient point dependent on the number of people staying in the hotel at any one time. Another important benefit of this environmentally-friendly solution is that it is very cost-effective. By not using unnecessary capacity, the customer can make significant cost savings with this type of installation.
Because the new pumps operate using atmospheric air taken from the surrounding area, they have several advantages over pumps that use a pressurized air system. One key advantage is that the range does not require a blower, which means that noise can be kept to a minimum – especially useful for plants installed in residential areas.
Having no blower therefore means fewer tubes, making the placement of the aerator much easier, which means installation costs are kept down. For this project, the aerators were light enough and compact enough to be lifted into position by hand. They fit easily through the man-holes cut into the PE tanks without having to replace the tanks. As well as initial installation being quick and straightforward, the simplicity of the system allows for easy access for any future maintenance or repairs: the aerators can simply be lifted up by hand via a chain that is fixed to the top of each one.
Finally, because the TRN range sucks air in at the surrounding ambient temperature (unlike pressurized systems which heat up the air to high temperatures) there is much less stress on the plant's plastic components meaning far less risk of melting, which can lead to costly repairs.
Ten models
The new TRN series consists of ten models with motor outputs between 0.75 and 40 kW. They have numerous design features that increase longevity of the pumps and therefore reduce maintenance costs. Tsurumi say that the range is reliable and adaptable for both larger projects, such as industrial and municipal waste water treatment plants, and also smaller, residential installations.
All of their aerator equipment is tested according to EN 12255-15 standards – a norm published in 2004 defining how oxygen input in waste water treatment plants should be measured.