Classification of areas with explosion hazard due to the presence of flammable gases and combustible dusts of two large municipal waste water treatment plants

2023 / Advice on health and safety in the workplace / Infrastructures

The plants under study are among the largest in Italy in terms of the volume of cubic metres of sewage water treated.

Due to the type of substances present and plant treatments, there are areas classified as hazardous due to the presence of:

flammable gases

  • biomethane generated by the fermentation of the sewage itself;
  • methane gas from the heating boiler supply line diathermic oil used to operate the dryers;
  • diathermic oil (due to its physical-chemical characteristics and operating conditions, it represents a possible source in the evaporation phase from any liquid pool resulting from flange leakage)
  • hydrogen developed in the battery charging phase of electric vehicles (forklift trucks, pallet trucks and scrubber driers);

combustible dust

  • dried sludge, the product of the thermal drying process of dehydrated sludge, whose physical and chemical analyses have revealed characteristics such that the risk of explosive atmospheres generated by their presence cannot be considered negligible