APPENDIX B 



TREATMENT FOR REMOVAL OF CHLORINE FROM CITY WATER FOR 



USE IN AQUARIA 



By R. S. Taylor, formerly Technologist, and Milton C. James, Assistant 

 Chief, Division of Fish Culture, U. 8. Bureau of Fisheries 



INTRODUCTION 



The admitted advantages of chlorination as a means of purifica- 

 tion of municipal water supplies appear to have overshadowed a 

 minor difficulty that has accompanied the use of this method. This 

 disadvantage manifests itself in the injurious effects exerted on 

 fish life by chlorinated water. Wherever treated water is used as a 

 supply for aquaria or for fish hatcheries serious losses may be ex- 

 pected ultimately. As an example of the extent of the damage, the 

 following report of conditions at the central station aquarium of 

 the Bureau of Fisheries following chlorination of the Washington 

 water supply is quoted. The aquarium supply is taken directly from 

 the city mains. 



Beginning Tliursday morning, March 16, 1922, large numbers of fisli of 

 several species died in the exhibition aquaria and hatching troughs of the 

 bureau at the central station in Washington, D. O. The flngerling fish were 

 lost, and many half-grown and adult fisli, including two sturgeon about 3^2 

 feet long, which had been kept in aquaria 14 years. For the number of indi- 

 vidual fish and the number of species affected the mortality was without 

 precedent at this station. Nearly all the fish died during the night. 



Through inquiry of the water department it was learned that chlorination 

 was begun on the day preceding the mortality (Wednesday, March 15), 

 liquid chlorine being added to the water after filtration at a fixed rate, 

 based on the average daily flow (0..3 part per million). Wliile chlorine in this 

 proportion might not have been injurious to fish, it is obvious that the actual 

 proportion of chlorine would vary widely during the course of the day, 

 according to the flow of the water. The effects would also be different if 

 water, after chlorination, were discharged into the reservoir, as is true of 

 the water supply for a large part of the residential district, instead of 

 passing directly into the mains, as is luiderstood to be the case with water 

 reaching the ix)rtion of the city in which the bureau's aquarium is located. 

 The consumption of water must be vei*y low during the hour.s between mid- 

 night and 6 o'clock a. m., and the proportion of chlorine would accordingly 

 be very much higher than the computed theoretical ratio of 0.3 part per 

 million. It is significant that virtually all deaths of fish occurred during 

 the night. It is understood that chlorine had not hitherto been used in 

 treating the water supply of the District. 



In succeeding years a recurrence of this situation has confronted 

 the bureau. 



That the difficulty is not purely local is shown by the fact that 

 the Michigan State Hatchery at Bay City has experienced trouble 



322 



