Case study: ARA PUSTERIA /ARA PUSTERTAL sludge waste to energy plant in Italy
ARA PUSTERIA SPA Key Facts & Figures - 2021
- The waste to energy plant located in Tobl (North East of Italy) treats the sludge of five wastewater treatment plants in Val Pusteria / Pustertal
- On average, the five wastewater treatment plants treat around 12.4 million cubic meters of wastewater annually.
- 24 ktons of dried household sewage sludge have been incinerated in 2018 against a total capacity of 26 kton / year
- Flue gas cleaning lay-out: SOLVAir® S300 + baghouse filter
- Emission values achieved at stack far below the permit
ARA PUSTERIA SPA needs
ARA Pusteria SPA / ARA Pustertal AG operates five wastewater treatment plants and the associated main collector with a length of 132 km and a catchment area of 2.168 km² in a touristic mountain area.
The plant treats wastewater for 150.000 inhabitants (30% residents, 50% tourists and 20% industry) and produces biogas used for energy production. In 2018, ARA Pustertal was thus able to generate by itself 71.1% of the energy it required.
High SOx pollutants abatement
The ARA plant in Pusteria has to remove more than 95 % of the incoming SOx by means of a dry system without liquid effluent, in an area that is very sensitive to environmental issues.
A flue gas cleaning line compatible with limited available space
The flue gas cleaning line has to be compatible with the limited space available, as the entire sewage pipe, ventilation system and dosing equipment are located in underground galleries in the mountain. Another thing to note is that the digestion tower, with the exception of the gas area, is built into the rock. Only the remaining sludge line, the complete gas line and the drying and thermal plant are located in the plant building above ground.
What SOLVAir® did for ARA PUSTERIA
High pollutants removal rates
SOLVAir® was able to achieve the SO2 emission limit value of 50 mg/Nm³ (dry, 11% O2) in order to comply with the stringent EU regulation of waste incineration.
ARA Pusteria has used SOLVAir® Solutions since end 2007 to meet SOx emission limit value after an industrial trial supported by SOLVAir® technicians.
“We use SOLVAir® S300, a high quality product that helps us to comply with the emission limit values safely; we are very satisfied with the use of the product”
The thermal valorization plant
The dried sewage sludge is mineralized in the thermal plant equipped with a rotary kiln. On 24.736 tons dewatered sewage sludge treated, approximately only 1.344 tons of inert material remain, which is recycled and reused for landfill capping (see chart below).
The flue gas cleaning line uses SOLVAir® sorbent and a baghouse filter.
ARA Tobl plants - Inlet and outlet anlyses - products in tons (source ARA)
Benefits for ARA PUSTERIA
An environmentally sustainable solution
SOLVAir® proved to be a sustainable solution in a touristic strategic environment that is traditionally very sensitive to environmental issues.
The high performance of SOLVAir® Solutions and the consistency of the sorbent supply have supported ARA Pusteria in their industrial objectives, helping the plant in retaining social acceptance.
Requirements of the legislation
ARA Pusteria already complies with the new BREF Waste Incineration emission limits.
SO2 emission limit values to be complied with:
- 1/2h : 100 mg/Nm³
- 24h : 50 mg/Nm³ (dry, 11% O2)
Plant average outlet SO2 values (dry, 11% O2):
- Operating year 2020: 41 mg/Nm³
- Operating year 2019: 38 mg/Nm³
"Working with ARA PUSTERIA since a long time, we have learnt that they pay attention to every technical detail regarding their plant. They have been able to find their own innovative solutions. Our strong collaboration started with SOLVAir® industrial trial in 2007 and has been instrumental to achieve today’s environmental performances"