XXII. J. DAVIS. 



surface of the filter beds retains most of the remainder, and 

 thus the first function of the bed is to some extent a mechanical 

 one, but it is the organic matter in solution, and the finer 

 particles in suspension, particularly which are chemically and 

 biologically dealt with and rendered inocuous in the bed itself. 



The sewage as it sinks through the sand clings in a thin film 

 over every particle, exposing an enormous surface to oxidation. 



Air is drawn into the beds during each period of aeration by 

 the sinking of the sewage itself, and by that means the action of 

 the nitrifying micro-organisms is facilitated. 



Sand, though not primarily as rich in such organisms as a good 

 garden soil, soon becomes an excellent filter capable of cleansing 

 the sewage, which has previously been subjected to precipitation, 

 of as many as 8,000 persons per acre, if intermittently applied and 

 the bed is sufficiently rested. On that basis the present filtration 

 area, 8 acres, will provide for a maximum population of over 

 60,000 persons. 



The treatment works having only recently been put into 

 operation there has hardly been time to procure an analysis of 

 the effluent, but it is hoped one will be available for the informa- 

 tion of the section at the next monthly meeting. 



TEST OF EFFICIENCY OF PLANT. 



On the 6th and 7th June, 1899, tests were made of the 

 machinery. 



On the first day the boiler only was being fired, and J ton of 

 slack coal was consumed in 10 hours. During this time the 

 sludge presses were running, and the engine, therefore, was 

 driving compressor and lime and sewage mixers. On the second 

 test, again for a period of 10 hours, the boiler and one destructor 

 furnace were being fired, consuming together f of a ton of slack 

 coal. The sludge presses were also in operation, and the engine 

 was driving compressor and lime and sewage mixers. The coal 

 used for each day included that used for lighting up. The extra 

 coal used on the second day was required to start the destructor 

 furnace. 



