EXPERIMENTAL METHODS IN WATER- AND SEWAGE- WORKS 35 



have by no means been confined to Hamburg. His publications 

 show that he has advised the authorities at Miihlhausen, Stuttgart, 

 Beuthen, Unna, Leipzig, and other places. In nearly every instance 

 he has taken advantage of experimental data to ascertain local 

 conditions. Leipzig and Chemnitz in Saxony are now conducting 

 sewage tests, the appropriations for which are about $17,000 in 

 each case, with the engineering and analytical data secured by men 

 regularly employed by the city. 



This brief record of experimental methods as applied to water 

 and sewage purification can hardly be brought to a close without 

 reference to trade wastes. This feature in aggravated cases com- 

 plicates the design of sewage- works and adds materially to the costs 

 of operation. Various industries require special consideration, as 

 shown by the efforts of the river boards to minimize the effect of 

 trade wastes in the streams of Lancashire and Yorkshire, England. 

 The removal of fats has perhaps received the most attention along 

 this line especially in Berlin, Cassel, and Chemnitz in Germany, 

 Verviers in Belgium, Roubaix and Grimonpont in France, and 

 Bradford, Manchester, and Oldham in England. Numerous mill- 

 owners also recover grease from their waste water. The extent 

 of some of these investigations is indicated by the fact that at Cassel 

 a private company is said to have spent considerably more than 

 $100,000 in unsuccessfully endeavoring to fulfil a contract for extract- 

 ing fats from the city sewage. The only large place where the 

 entire city sewage is regularly treated for grease extraction is at 

 Bradford, England. 



