THE AMI.IUCAS MrslJM JoriiX.lL 



Septic Tank or modified scdimi-ntaiion basin. Model in the American Museum 



is New York, where tlie waste would liaxe to he carried a yreat (Hstance 

 before final (Hspositiou of it could l)e made. 



At Lawrence, Massachusetts, through the experiments of the Massa- 

 chusetts Board of Health, a more scientific and intensive modification of 

 the irrigation process was devised known as intermittent filtration. It 

 consists in the application of sewage in regulated quantities to the surface 

 of properly prepared l)eds of sand in which nitrifying bacteria colonize and 

 oxidize the organic matters in the sewage into harmless mineral form. The 

 construction of this filter is simple in regions like those in tlie northeastern 

 part of the United States where there is suitable soil from glacial drift. 

 Even the intermittent filter requires a large area of land however, and 



Double contact beds lor purification of sewage on tlie plan of "broad irrigation" but 

 without the necessity of large areas of land. Model in the American Museum 



