Properties and composition of sewage waters

Due to a higher concentration of tensides, dispersion and emulsifying processes can occur, but in some cases coagulation of coUoid substances can take place. 

During the decomposition of proteins into simpler substances sulphur compounds are released which are reduced to hydrogen sulphide, and nitrogen compounds are reduced to ammonia. CoUoid proteins are transformed into solutions via degradation into peptones, amino acids and finally into ammonia and carbon dioxide. 

In addition to bacteria which degrade organic substances by hydrolysis and oxidation-reduction processes, wastewater also contains different ferments and enzymes (formed by cells), which also take part in the decomposition of organic substances. 

The colour of sewage waters is usually grey, sometimes even yellow-brown. They are intensely turbid. Under anaerobic conditions generated hydrogen sulphide reacts with the compounds of iron to produce FeS, and causes darkening of water. 

The odour of fresh sewage waters is not too intensive. Only after the exhaustion of dissolved oxygen (after several hours) when anaerobic reduction processes start to take place, does the water begin to smell intensively. 

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