PROTECTION OF RIVER AND HARBOR WATERS 15 



When sewage is discharged in small volume into a relatively large body of 

 water this process takes place spontaneously. The bacteria normally 

 present in the water attack the organic matter and oxidize it and at the same 

 time the typical sewage bacteria, finding themselves in an unfavorable 

 environment gradually die and disappear. Disposal by dilution, or the 

 discharge of sewage under regulated conditions into adequate bodies of 

 water, is a recognized method of sewage purification, much used in Germany, 

 and often with success. The discharge of too large volumes of sewage into 

 bodies of water which could not successfully digest them has however fre- 

 quently caused grave nuisances and dangers to health, and the undue con- 

 centration of sewage in small bays and in restricted areas near shore may 

 produce local conditions of the same sort. Most inland cities and many 

 seaport cities as well are therefore compelled to seek some special method of 

 sewage treatment before their wastes can be discharged into adjacent 

 water courses. 



BROAD IRRIGATION OR SEWAGE FARMING 



The most obvious alternative to the disposal of sewage in water is its 

 distribution over the surface of suitable land; and this process of "broad 

 irrigation" is the primitive form from which our modern modes of sewage 

 treatment are derived. Under proper conditions the living earth readily 

 absorbs and digests the foreign materials, by the same processes which lead 

 to the annual disappearance of manure from heavily fertilized land; and 

 the organic matter is not only rendered harmless but is changed into a form 

 in which it serves as food material for the higher plants. 



Baldwin Latham, the distinguished English engineer, believed that he 

 had discovered sewers and irrigation areas in the ancient city of Jerusalem; 

 and in China excreta have been utilized for centuries as fertilizer for the 

 fields. At Lausanne in Switzerland, at Milan in Italy, at Bunzlau in 

 Prussia, irrigation was practised in the fifteenth and sixteenth centuries. 

 The extensive development of the art dated, however, from the wave of 

 sanitary reform which swept over England as a result of the Report of the 

 Health of Towns Commission in 1S44. This report marked the beginning 

 of extensive sewerage construction in the modern sense and with sewerage, 

 sewage disposal was urgently required. With the desire to dispose of pol- 

 luting material, there grew up in these early days a parallel interest in the 

 possible profit to be derived from crops grown on the irrigated land. The 

 two aims are well balanced in the definition of sewage farming as "the dis- 



