The access to drains and drainage canals is dangerous for the lack of oxygen, methane and sulphured hydrogen. Mud digester: mud digesters can be considered “methane producers” where the crude reflowing water biodegrades producing high levels of methane as a sub product. Normally the 60-70% of the volume is methane, which afterwards will be utilized as fuel for other uses, like electricity production through turbine.

GASES INVOLVED

Sulphured hydrogen (H2S): it is a sub product massively present in the reflowing water depuration process. Its generation is due to the decomposition of organic substances.
Carbon dioxide (CO2): it is a transformation product of every decomposition process.
Methane (CH4): it is one of the most important products of water depuration; it originates from the decomposition of some organic substances in absence of oxygen. It is classified as a biogas.
Chlorine (C1): it is used as a disinfectant in some refining processes.

EXPECTED RISKS

H2S: colourless gas stands out for its characteristic smell of rotten eggs. A low-concentration exposure causes eye and throat irritation, cough, acceleration of breathing and fluid formation in the respiratory ways. High concentrations kill the olfactory nerve so making impossible to smell its disgusting odour, and may cause unconsciousness in few minutes.
CO2: poisoning due to carbon dioxide, risk of asphyxia due to lack of oxygen.
CH4: methane is a simple hydrocarbon and is in nature in form of gas. Methane is the main component of natural gas and is an excellent fuel, able to form easily in atmosphere resulting in a high risk of explosion.
Cl: chlorine irritates the breathing system, mainly in children and old people. When in gas state it irritates the mucosa, and in liquid state, it causes skin burns. Chlorine odour can be smelt at a 3.5 ppm concentration.