ARA Pustertal AG operates the Tobler wastewater treatment plant in South Tyrol, Italy. The Tobler ARA facility is the fi rst and only water treatment plant in Central Europe that is housed in an underground cavern. The impressive cavern plant, whose tunnels are twice as large as that of a highway tunnel, began operation in July, 1996. The inclusion of a sludge drying plant and a thermal sludge treatment facility make the ARA Pustertal AG largely independent in the disposal of the sewage sludge.
Selecting the Cavern Facility
'The provincial government of South Tyrol searched for years for a suitable location for a wastewater treatment plant in the Pustertal Valley - without results,' says Dr. Ing. Konrad Engl, Chief Operation Offi cer of ARA Pustertal AG. In the early 1990s, they decided on the underground site, Tobl, due to the high level of community acceptance and the optimal operating conditions. Engl summarized the mood at the time, 'What you don’t see, doesn’t stink.' In addition, Engl adds, the constant temperature and weather conditions provide longer life for the equipment.
Besides the uniqueness of its architectural design, the Tobler ARA facility grew increasingly important as a regional treatment facility due to the gradual enlargement of the service area. Fourteen (14) municipalities with a population of approximately 400,000 are connected to the system.
To reduce the volume and weight of sludge, the site installed a sludge drying plant in 1998. 'From 100 kg wet sludge, only slightly more than 20 kg remain after drying”, said the CEO.
The construction of the drying plant would also dehydrate sewage sludge from external wastewater treatment plants. Currently, about 25,000 tons of sewage sludge are dried per year. 'However, the sludge disposal problem had not yet been solved' explains the COO of ARA Pustertal AG. The only place to dispose of the sewage sludge was in the Po Valley in South Tyrol. Many truckloads of dried sewage sludge were being transported there.