Filtration: Then and Now

archives.bookshelvesLast week we posted about the history of filtration in Water Treatment. The first recognized instance of filtering water was credited to Hippocrates roughly 2,500 years ago, with the introduction of more and more filtering options added as civilization moved on to bigger and better scientific discoveries.


Rapid_sand_filter_EPAToday marks the 98th anniversary of a Rapid Sand Filter system being installed in St. Louis. From the “Municipal Journal,” we can get a glimpse into 1915-era water treatment: “The city has celebrated the dedication of the new $1,350,000 filtration plant…The new plant, which is of the rapid sand filter type, has a capacity of 160,000,000 gallons daily, increasing to 200,000,000 in emergencies…The coagulation and sedimentation process, installed in 1904, is still used in connection with the rapid sand filters and the sterilization with liquid chlorine when necessary. The waterworks are now valued at $29,680,000, with a bonded indebtedness of $2,642,000. The flat rate is 8 3/4 cents per 100 gallons. The new addition took 20 months in building.”


Slow_sand_filter_EPAPerhaps most interesting to note is the city’s plan to chlorinate “when necessary,” as opposed to chlorinating as part of the normal water treatment process. The main source of St. Louis’ water supply was the Mississippi River, which would need even more treatment before becoming safe enough for public consumption. Just 18 years prior to the opening of St. Louis’ filtration system, the city of Albany, New York, had installed a Slow Sand Filter system to service the city. Next week we’ll take a closer look at the critical differences between rapid and slow sand filtration, as well as the rolls both types of filters can play in the treatment process.