XVIII. J. DAVIS. 



The sewage passes from the agitator into an open concrete 

 channel, 5 ft. 3 in. by 3 ft. 3 in., which runs along the whole 

 extent of one side of the five settling tanks at a higher level 

 than the latter. There is an off-let pipe from the conduit into 

 each of the tanks, so that by opening the valves attached, the 

 sewage may be admitted into any of the tanks as required. 



Each settling tank has a capacity of 93,750 gallons. All of 

 them are so arranged that one or more can be used continuously, 

 or each may be filled, allowed to rest, and emptied in rotation. 

 It is preferable generally to adopt what is called the " continuous 

 flow " system, that is two or more tanks are used continuously at 

 one time. The present maximum dry weather flow, 750,000 

 gallons, can be treated in this way by two tanks, the liquid at 

 the surface being floated off continuously over a weir at the end 

 of the tanks. Even during the six hours of maximum flow each 

 day the capacity of two tanks is such that they would be 

 emptied twice only in that time, or once every three hours, a 

 rate quite sufficient to allow of complete precipitation of the 

 grosser solids. Of course during the time of lesser flow, or 18 

 hours of the day, one tank would be ample for the present dis- 

 charge, as it would take 4 \ hours for the sewage to pass through 

 it. 



Four tanks working together in this way would be able to 

 cope with the greatest daily flow. Ultimately, however, when 

 the population increases, additional tanks will have to be provided,, 

 and for these ample space has been left. 



When, after a few days, the tank becomes foul, it is necessary 

 to empty it into the effluent channel. To ensure that in this 

 process only the liquid portion of the contents of the tanks is 

 removed, a floating arm controlled by a valve has been adopted. 



The liquid sludge which remains in the tank passes down the 

 dished and sloped bottom by gravitation into the sludge reservoir 

 adjoining. 



The sludge is allowed to gravitate from the reservoir through 

 a 12-in. pipe into two close-ri vetted steel cylinders, each of 900 

 gallons capacity, which are situated immediately under the 



