Technology

The mechanical and biological treatment of mixed municipal waste is aimed at reducing collected waste at the landfill in the most economical and ecologically acceptable manner.

In the process of the mechanical and biological treatment of waste, the volume of the waste to be deposited in the landfill is reduced to approximately one third of the original amount. One third is extracted in the biological treatment process and the second third is extracted from the residue and brought to the district heating plant for incineration.

The process of the mechanical and biological treatment of waste is foreseen in the following treatment phases:

• waste intake in the plant’s intake facility,
  
• grinding the waste during storage,
  
• biological treatment of the mass (biostabilisation and biodrying),
  
• mechanical treatment of the mass and the production of solid recovered fuel.

THE BIOLOGICAL TREATMENT PHASE

The biological treatment is conducted in the biostabilisation facility.

During the 14 days of biooxidation, organic substances are extracted, primarily as CO2 with a loss of humidity. The results of the process are as follows:

• the weight of the waste is reduced by 1/3 of the initial weight,
  
• the main biological processes that would otherwise take place in the landfill, take place already in the process of accelerated biooxidation,
  
• a stabilate is obtained.

In this manner and with minimal (additional) energy costs, at the end of the process we are left with a stabile, dry and sanitised product without an unpleasant odour.

The entire process is conducted in a closed hall. In order to prevent environmental pollution during the biostabilisation process, the gases are exhausted through a strong biofilter. To reduce the quantity of wastewater released into the sewage system, the process is designed to allow the leachate to be partially led back into the process.

THE MECHANICAL TREATMENT PHASE

After the biostabilisation process has been completed, the automated crane transfers the biostabilised material to the transporter, though which the material then travels from the biostabilisation facility to the facility for mechanical treatment.

The mechanical treatment includes:

• grinding,
  
• demetalisation,
  
• sieving,
  
• separation.

In this, the following are separated:

• the light fraction – solid recovered fuel for the district heating plant,
  
• metals,
  
• stabilate (stabile organic matter),
  
• inert fractions (incombustible fractions).

The heavy fraction is extracted using a sieve.
Following the sieve, the combustible part is separated with an air separator. This is the light fraction, which is then ground and the metals are extracted (iron, aluminium and other metals) using magnets and a whirling magnetic field.
The heavy fraction is deposited in the landfill, the metals are taken over by the collector of secondary raw material and the light fraction is transported to the district heating plant.