igo SEWAGE AND ITS PURIFICATION 



the organic matter decreased, the amount of available chlorine 

 consumed was correspondingly lessened, and the proportion of 

 I to 17 between five minutes' oxygen and available chlorine 

 still remained a guide. 



The primary effluent at Guildford required 2 parts of av. CI 

 per 100,000 to reduce the coli from 100,000 per c.c. to less than 

 I per 5 c.c. after 40 minutes' contact, and the B. enteritidis 

 spores from 20 per c.c. to nil in 5 c.c. after 2 hours' contact. 

 After being kept for 4 days, the untreated had a strong sewage 

 odour, the treated remained odourless. 



In the secondary effluent, with i*o6 parts av. CI, coli was 

 reduced from 1,000,000 per c.c. to none per 5 c.c. ; B, enteritidis 

 spores from 100 to 1,000 per c.c. to none in 5 c.c. ; and the total 

 organisms from 1,000,000 to 40 per c.c. Incubation 48 hours : 

 untreated, sewage smell ; treated, inodorous. 



In the tertiary effluent the small amount of 0*25 part of 

 av. CI reduced the coli from over 10,000 per c.c. to nil in 5 c.c. 

 in I hour, and the B. enteritidis spores to less than i per c.c. 

 in 4J hours. 0*5 part av. CI reduced the coli from over 10,000 

 per c.c. to less than i per 5 c.c. in 30 minutes, and the 

 B. enteritidis spores to less than i per 5 c.c. in four and a 

 half hours. The incubation tests gave after 4 days a distinct 

 odour in the untreated, none in the treated. Decided chemical 

 improvement was shown, and the treatment caused an increase 

 of free, with a decrease in albuminoid, ammonia, showing a 

 breaking down of the organic matter. 



The effect of treating infected drinking-water was tried. A 

 tap water contained go organisms per c.c, and coli was present 

 in 4 ex. After treatment with 0*075 part of available chlorine 

 (Exp. 54), the total organisms were reduced in 5 hours to 

 14 per c.c, and coli was then absent from 20 c.c. Another 

 portion was mixed with - J^j of its volume of tertiary effluent, 

 and 0'o8 part of available chlorine added (Exp. 58). The 

 infected tap water had contained 100 coli per c.c, but after one 

 hour's action of the oxychloride there were none present in 

 20 c.c, and this condition remained through a channel more 

 than 100 feet long. The water after standing did not retain 

 any taste or smell of the treatment, and the chloride as 

 measured by chlorine was only increased by i'75 to 2 parts 

 per 100,000, which is obviously of no significance. The tap 

 water at this time contained more total organisms and more 

 coli than remained in the sewage after the chlorine treatment, 



