Water Purification Processes Classical and Modern

Primary treatment removes 40 to 60% of the solids present in sewage and about 30% of the organic matter present. Calcium hydroxide and aluminum sulfate are added to produce aluminum hydroxide, which is a sticky, gelatinous precipitate that settles out slowly, carrying suspended dirt particles and bacteria with it. 

For many years municipal sewage treatment plants had only primary treatment, followed by chlorination of the treated wastewater (see Section 11.12) before it was discharged into a suitable river or stream. Chlorination kills any remaining harmful pathogens. Presumably, natural processes would get rid of the remaining solids and dissolved organic matter. 

Cesspools were an early and erude form of fhe modern activafed sludge proeess. 

Sewage includes everything that flows from the sinks, tubs, washing machines, and toilets in our homes, factories, and public buildings. It excludes wastewater treated separately by industrial facilities. 

Parent Nothing harmful to my child. Game and Fish Commission Nothing harmful to animals.  

---