XL. 





J. M. SMAIL. 







Parts per Million 



Percentage of Organic Matter 

 Removed 



Nitrogen as Albuminoid Ammonia 



Oxygen Consumed 



Albuminoid 

 Ammonia 



Oxygen 

 Consumed 



River Water 



Filtered Water 



River Water 1 Filtered Water 



0-121 



0-075 



6-3 1 1-6 



38 



75 



Removal of tastes and odours. — " The Passaic river water 

 ordinarily has a slight musty or vegetable odour, and at 

 times during the autumn it has a swampy odour which is 

 noticeable to persons unfamiliar with the water, but which 

 is not disagreeable, and in fact is hardly recognised by 

 those familiar with surface waters from swampy areas. 

 The removal of tastes and odours by filtration is appreciable, 

 but when the swampy odour is present in the river, it is 

 still clearly recognisable in the filtered water on careful 

 examination. Studies of the practicability of removing it 

 by aeration have been made, but it is found that this is 

 unsuccessful, as the odour and tastes still persist after 

 vigorous aeration for some 10 to 12 hours. The taste and 

 odours are evidently produced by oily substances liberated 

 from the vegetable growths in the swampy areas, and 

 apparently could be removed only by filtration through 

 sand at exceeding low rates. 



Removal of coagulant. — "In no case has the filtered water 

 contained any undeeomposed sulphate of alumina. Regard- 

 ing the removal of the aluminum hydrate, ordinarily this is 

 complete, although now and then the numerous analyses 

 made, indicate that faint traces of the hydrate in a very 

 fine colloidal form have appeared in the filtered water. 

 These traces are too small to be measured, although, in a 

 general way, it may be said that there are times when it 

 would probably amount to about O'OG parts per million, 

 equal to 0*0035 grain per gallon. The average would be 

 less than 0*01 part per million, corresponding to a removal 

 of more than 99 per cent, of the hydrate contained in the 

 raw water. These traces are gradually diminishing as the 

 sand layers are becoming 'ripened.' 



