Construction of a waste recovery line

The Aprilia composting plant for municipal waste and other non-hazardous waste with a compostable matrix is authorised under a regional AIA to recover materials and energy from waste by means of anaerobic digestion and aerobic treatment. PAL was involved in the construction of a recovery under-screening line from different streams coming from the processing of two biological treatment systems of the Organic Fraction of municipal solid waste. The plant, which is compact because it is 25 metres long and 7 metres wide, has made it possible to minimise the footprint while maintaining easy maintenance areas and access to the machines. The highly corrosive environment necessitated the use of stainless steel and other suitable materials to ensure durability.

The CSS production line is fed by three different flows from two separate plant sections.

• The first flow - SOV1: under-screening with a size greater than 80 mm at the outlet originating from the pre-treatment system of the OFMSW (Organic Fraction of Municipal Solid Waste) that has not yet undergone digestion.
• The second flow - SOV2: underscreening materials of more than 80 mm deriving from the sorting of processed material through composting that underwent bi-oxidation accellerated in two stages: the first in a forced aeration bio-tunnel; the second on an similarly aerated floors, for a total treatment time of 25-29 days.
• The third flow - SOV3: under-screening materials of more than 40 mm delivering from the sorting of material exiting the bio-tunnels belonging to the new aerobic composting section.

The new line, built by PAL, can be fed through the existing line (SOV3) or through a special loading hopper using a wheel loader (SOV1 and SOV2). The plant was designed to have a certain degree of flexibility thanks to the bypass system, that allows the better manage any downtime due to maintenance.

The CSS production line is able to process the sum of flows for a total treatment potential of 15,000 t/year, distributed over 8 consecutive hours per day for 6 working days. The processed materials is divided into:

• 47-52% for the incoming flow coming from SOV1
• 27-32% for the incoming flow coming from SOV2
• 11-16% for the incoming flow coming from SOV3

It is possible to stop the new line without precluding operation of the existing screening line.

The production process follows the following steps:

• once the process is fed, the material is conveyed into a shredder;
• the material, conveyed inside the shredder, will reduce and homogenise;
• The result will be subsequently pressed and reduced in bales tied with plastic thread by means of a press and conveyed to the bale (film) wrapper;
• the final product will then be conveyed to the waste-to-energy plants.

The plant was built to ensure supervision and control of the entire production line both in the field and within the office premises.