pollution from a sewage treatment plant and in which all the zones of pollu- 

 tion from recent pollution to clean water were present. The stream was sur- 

 veyed, and a map was prepared showing pools, riffles and runs, and 

 different bottom types, as well as stream widths and depths. A sampling 

 program was established, and sampling stations were selected. A broad 

 crested weir and gauging station were built, and a weather station was 

 established. A trailer laboratory was equipped and placed near the 

 Wilmington, Ohio, primary sewage treatment plant and was used as a field 

 headquarters for chemical analyses and biological studies. Periodic 

 sampling studies over 24-hr periods with samples taken at each sampling 

 station every hour were conducted over a 2-year period. At least one such 

 continuous sampling was carried out in each of the seasons for each year. 

 During these studies hourly samples were taken for the determination of 2 , 

 C0 2 , pH, temperature, acidity, alkalinity, and turbidity. Samples were 

 also taken for BOD and COD (chemical oxygen demand) and periodic 

 bacteriological determinations. At selected times analyses were made for 

 P0 4 , NH 3 , N0 3 , and H 2 S. Hourly plankton samples were taken during the 

 24-hr sampling periods to determine seasonal and diel fluctuations in the 

 populations. Periodic samples of the benthic macro- and microinvertebrates 

 were taken throughout the year under the direction of A.R. Gaufin. Monthly 

 seinings for fish were made at all stations throughout the stream. 



These studies and samplings provided data on the various pollutional 

 zones: their biological, physical, and chemical characteristics; and sea- 

 sonal and diel changes in their characteristics and extent. This extensive 

 and intensive study produced many valuable data and several new concepts. 

 It was concluded that the quantitative and qualitative makeup of the biota 

 was characteristic of the so-called zones of pollution and was indicative 

 of environmental conditions or pollution. The mere presence or absence of 

 any single species could not be considered as an indicator of pollution. 

 In a polluted stream 2 , C0 2 , and pH could vary widely over a 24-hr period 

 at the same station. Such variations were especially noticeable in the 

 upper recovery zone where there were large growths of algae. These data 

 indicated that the sag curve, developed by nonbiologists who ignored the 

 effects of algal growths, could be very misleading, especially in the 

 smaller streams, because the samples for its determination were usually 

 taken after noon. Other important findings were the seasonal shift in 

 zones of pollution and changes in their character, the extension of 

 Sphaerotilus growth downstream in winter, the failure of fishes to enter in 

 winter the septic zone of summer even though 2 was abundant and the 

 inapplicability of the K factor developed for large rivers like the Ohio 

 River to small streams such as Lytle Creek, where it was 1.8 instead of 

 0.1. Data resulting from the Lytle Creek studies were reported in some 15 

 publications . 



At the termination of the Lytle Creek studies in 1953, the laboratory 

 bioassay studies of the Biology Section were increased. Because the water 

 supply at the Sanitary Engineering Center was unsatisfactory for bioassay 

 investigations and water for such studies had to be brought from the 

 Newtown Fish Hatchery to the sixth floor of the center in glass containers, 

 a search was made for a water supply where meaningful studies could be 



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