170 



SCIENCE. 



[N. S. Vol. XVI. No. 396. 



by one half -inch and rejected by eighth- 

 inch mesh. The method of the distribution 

 of the sewage is novel; the chemically 

 treated sewage rims into two delivery 

 mains, each thirty inches in diameter, one 

 of these connected with seven horizontal 

 pipes, the other with eight. These pipes 

 run the whole length of the bed, dividing it 

 into sixteen sections, and the flow in each 

 pipe is controlled by a valve. From each 

 of these fifteen pipes are raised vertical 

 pipes ten feet apart and ten feet high. 

 Each of these stand pipes is connected at 

 right angles with four-inch horizontal pipes 

 which run across the bed. On the top of 

 the bed, therefore, there is a layer of hori- 

 zontal pipes ten feet apart. These hori- 

 zontal pipes are fitted with vertical spray 

 jets at every five feet, each spray pipe hav- 

 ing two quarter-inch holes set at an angle. 



The floor of the filter has a fall of two 

 feet from inlet to outlet, and is covered 

 with tiles raised on feet sufficiently high, 

 about three inches, to ensure air circulation 

 beneath the filter. The drains are under- 

 neath the fifteen large horizontal pipes at 

 the bottom of the chamber and all discharge 

 into a main culvert which carries the 

 effluent into the river. 



The chemically treated sewage passes 

 from the valve chambers into one or both 

 of the delivery mains and is delivered to 

 any or all of the horizontal pipes; from 

 these it passes up the vertical pipes into the 

 four-inch horizontal pipes, and then into 

 the spray pipes. There is a sufficient head 

 to cause the liquid to spout out of the spray 

 pipes to a height of from five to eight feet, 

 and it will then fall like rain on the surface 

 of the filter. 



The dry weather flow upon the bed is to 

 be about two and one half million gallons 

 per acre, to be increased when necessary to 

 five million gallons. 



There is no question but that the con- 

 struction of this plant is costly, but It 



seems to me that the chances of successful 

 treatment are greater with Mr. Corbett's 

 plant than by any other method of con- 

 tinuous filtration. 



Undoubtedly, continuous filtration has 

 certain merits, especially that of being able 

 to treat larger quantities of clarified sewage 

 on a given area than any other bacterial 

 process, but even if it accomplishes all that 

 is claimed, it is a process that requires a 

 great deal of oversight and attention. Fur- 

 ther, I do not see how any of these filters 

 can give satisfactory results in very cold 

 weather iinless the sewage is artificially 

 heated, owing to openness of construction, 

 and applying the sewage as spray. 



In conclusion I would say regarding the 

 present status of the sewage problem : That 

 Sewage Farming as a general method of sew- 

 age treatment is not practicable and seldom 

 possible. That Chemical Treatment only 

 removes a part of the polluting substances 

 in the sewage. It is a partial or prelimi- 

 nary treatment, advisable only in cases 

 where sewage contains germicidal sub- 

 stances, preventing the use of the septic 

 tank. That Intermittent Filtration is the 

 best method for the treatment of sewage of 

 cities where sand can be easily and cheaply 

 obtained, though the amount of sewage that 

 can be treated per acre per day is not over 

 75,000 gallons, unless the septic tank is used 

 in connection with the process. That the 

 septic tank process is a most valuable 

 adjunct and almost an essential part to all 

 bacterial methods of sewage treatment. 



That the contact method is not adapted 

 and should not be used for the treatment 

 of crude sewage, but can be considered a 

 very satisfactory method for the treatment 

 of sewage after it has undergone putrefac- 

 tion in the septic tank. 



That continuous filtration, though ca- 

 pable of treating much greater quantities 

 of sewage per acre than can be done by any 



