Sewage disposal . sewage disin-fection on a practical scale in this country has been made atProvidence, R. I. With a view to avoiding the pollution ofoyster layings the effluent from chemical precipitation and fromsedimentation without chemicals was treated with 3-9 parts ofavailable chlorine in the form of bleaching powder. When no limewas used, the costs of sedimentation and disinfection amountedto $ and $ for the years 1912 and 1913 respectivelyand the monthly average purification effected ranged from in 37 degrees count and from to in B. coli 1914 a r
Sewage disposal . sewage disin-fection on a practical scale in this country has been made atProvidence, R. I. With a view to avoiding the pollution ofoyster layings the effluent from chemical precipitation and fromsedimentation without chemicals was treated with 3-9 parts ofavailable chlorine in the form of bleaching powder. When no limewas used, the costs of sedimentation and disinfection amountedto $ and $ for the years 1912 and 1913 respectivelyand the monthly average purification effected ranged from in 37 degrees count and from to in B. coli 1914 a return was made to the practice of adding lime to thesewage before sedimentation, since the treatment of effluentfrom chemical precipitation gave better results than the treat-ment of the effluent from plain sedimentation. Disinfection atProvidence is at present (1918) accomplished by the use of chlorinegas delivered direct from a. bleach factory adjoining the works. 464 DISINFECTION OF SEWAGE AND SEWAGE EFFLUENTS. Fig. 132. Apparatus for Disinfection with Liquid Chlorine (courtesyof Wallace and Tiernan). PRACTICAL RESULTS OF SEWAGE DISINFECTION PLANTS 465 One of the best examples of a disinfecting plant that hasbeen operated with care and has therefore given good resultsis at Mt. Kisco, N. Y. This plant was built and is operatedby the city of New York for the protection of its water supply,on the drainage area of which the village of Mt. Kisco is sewage, from a population of 3000 persons, is first screenedand settled, then treated in double contact beds, then subjectedto secondary sedimentation, then filtered through sand beds andfinally disinfected with bleaching powder, the amount of avail-able chlorine applied varying between 10 and 20 parts per bacterial character of the sewage and the effluents at vari-ous stages of the process are shown in Table CXXX. TABLE CXXX BACTERIAL RESULTS OF SEWAGE TREATMENT AT MT. KISCO, N. Y.(Coffin and Hale, 1916.) Bacte
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