412 



NA TURE 



[June 2, 1910 



the Walbrook testing plant at Baltimore, Md., under co- 

 operative agreement with the Massachusetts Institute of 

 Technology, the State Sewerage Commission of New 

 Jersey, and the City Sewerage Commission of Baltimore. 



After considering the various possible methods of dis- 

 infection, and referring to numerous investigations made 

 in America, England, and on the Continent, the author 

 concludes that, in the absence of further information in 

 regard to the possibilities of heat (with consequent recovery 

 of ammonia) and of organic compounds, chlorine com- 

 pounds are most applicable in the case of the disinfection 

 of sewage and sewage efBuents. The authors' large-scale 

 experiments were therefore confined to the disinfection, by 

 means of chloride of lime, of sewage, septic sewage, and 

 effluents from trickling filters. | 



In common with other workers, Prof. Phelps finds that 

 whereas treatment with comparatively small quantities of i 

 chlorine fairly readily eliminates 95 per cent, or more of '• 

 the total organisms present, complete sterilisation can onlv 

 be obtained with difficulty and at relatively very much ' 

 greater ^ cost, which he concludes would render it 

 impracticable for regular adoption. Pages 39 to 46 and 

 56 to 60 deal with the disinfection, by means of chloride 

 of lime, of effluents from trickling filters at Boston and 

 Baltimore respectively. > 



The experiments' at Boston refer to the disinfection of 

 the total effluent (5000 gallons in twenty-four hours) from 

 two trickling filters 50 feet square and 8 feet deep. The 

 work extended over a period of seven months, including 

 both_ winter and summer months, so that the results 

 obtained may be taken as average results under working 

 conditions. 1 



It was found that with two hours' storage the addition 

 ^^ 3-5 parts per million of available chlorine (in the form 

 of bleaching powder) was sufficient to effect a reduction, on 

 the average, of 96-8 per cent, and of 99-2 per cent, of the 

 total organisms at 20° C. and of coU organisms respectively 

 present. 



In consequence of the greater purity of the Baltimore 

 filter effluent, similar results to the above were obtained 

 with the addition of less chlorine, viz. 2-2 parts of available 

 chlorine per million. 



As a result of the experiments on the disinfection of 

 Boston sewage and of septic sewage at Red Bank, N.J., 

 the author concludes that an average of 7 or 8 parts per 

 million of available chlorine is sufficient to disinfect the 

 sewage, whereas the septic sewage requires from 10 to 15 

 parts per million, this increased amount being mainly due 

 to the presence of sulphuretted hydrogen. 



On this account it is stated in the conclusions that where 

 no purification is required beyond that given by septic 

 action arid by disinfection, it is advantageous to reverse 

 the process by disinfecting the crude sewage before it 

 enters the tank. 



In this connection it is interesting to note the author's 

 remarks on p. 56 : — " There would be a great multiplication 

 of bacteria in the tank, so that the number in the final 

 effluent would probably be as great as in the raw sewage, 

 and perhaps even greater. Nevertheless, the disinfection 

 could be as effective on the pathogens as if it were applied 

 as a final process. The subsequent development of sapro- 

 phytes would have no sanitary significance, and would 

 doubtless be of real value in the subsequent self-purification 

 of the organic matter after it had been discharged into the 

 stream." 



The available evidence is favourable to this assumption, 

 but further information is required in regard especially 

 to the significance of the further development of organisms. 

 It is also interesting to observe that the investigations 

 of the author have led him to revise his earlier views in 

 regard to the use of electrolytic hypochlorites, and to con- 

 clude that, taking all things into consideration, it is prefer- 

 able to use bleaching powder as a source of chlorine rather 

 than to instal an electrolytic plant at the works. For 

 many reasons this conclusion will meet with general 

 approval on the part of those in charge of sewage works. 



A table of carefully considered costs is given, on the 

 basis of disinfecting 5,000,000 gallons per day by means 

 of bleaching powder, from which it will be seen that the 

 author estimates the total cost of treatment at from is. 2d. 

 per million gallons (is. 3d. cost of bleaching powder) for 



NO. 21 18, VOL. 83] 



the addition of i part of available chlorine per million, to 

 2 IS. per million gallons (185. gd. cost of bleaching powder) 

 for 15 parts of available chlorine per million. 



These costs include the cost of chloride of lime, storage 

 tanks, labour, &c., and are much lower than those 

 given for treatment with electrolytic hypochlorites pro- 

 duced at the sewage works by Digby (the Surveyor, vol. 

 XXX., No. 778, p. 687) and Shenton in 1906, and recently 

 repeated by Shenton (the Sanitary Record, vol. xliii., 

 No. 1013, 1909, p. 392), which vary from 35. 9^^. per 

 million gallons for the addition of i part available chlorine 

 per million to 195. for 5 parts available chlorine per 

 million, exclusive of charges for plant, storage tanks, and 

 labour. 



This difference in cost is accounted for by the fact 

 that the latter investigators estimate the cost of available 

 chlorine produced electrolytically at the works at lod. per 

 kilogram, whereas, using bleaching powder, it should not 

 exceed 33d. per kilogram. 



While Prof. Phelps's investigations afford very valuable 

 information and add considerably to the literature on the 

 subject of sterilisation of sewage and sewage effluents, his 

 suggestions in regard to the degree of disinfection are open 

 to objection, especially when applied to English conditions. 



In considering this matter, the difference between 

 American and English conditions must be borne in mind, 

 not only in regard to the chemical composition and bacterial 

 content of the sewage or effluent, but also to the probably 

 more important point of the conditions of discharge. 



Speaking generally, from both points of view American 

 conditions are ttie more favourable, as not only is the 

 sewage more dilute, but also, as a rule, the relative 

 volume of the river into which the effluent is discharged 

 is much greater than in the majority of English cases. 



In the case of the Boston sewage experimented upon, the 

 bacterial content was only 5,000,000 per c.c. as compared 

 with from 20,000,000 to 30,000,000 per c.c. in the case of 

 an average English domestic sewage. 



Further, it has been found that English effluents of 

 satisfactory chemical composition may contain as many 

 as 100,000 coli organisms per c.c. 



It is therefore doubtful whether such a degree of dis- 

 infection as proposed by the author might not in certain 

 cases give rise to an undue sense of security, especially as 

 no reference is made to the treatment of the large volumes 

 of storm-water which are discharged direct to the rivers, 

 from numerous storm-water overflows, a question which 

 is intimately connected with the subject of the disinfection 

 of sewage effluents. 



In the final chapter is described some very interesting 

 work carried out in connection with the methylene blue 

 test proposed by Spitta. With preliminary standardisation 

 for any particular effluent, this test would appear to afford, 

 in a very simple manner, valuable information in regard 

 to the stability of sewage effluents. As carried out by the 

 author, the test allows finer distinctions to be drawn 

 between stable and unstable effluents than is the casp with 

 the ordinary incubation test, which classes an effluent, 

 either as non-putrefactive or putrefactive, without references 

 to the degree of putrefaction. It would be interesting to. 

 know how far such a colour test is applicable to the 

 effluents from trade sewage.. 



EowARD Ardern. 



oceanographic.il investigations in 

 the atlantic and mediterranean. 



V\7E are informed that a Danish expedition has just set 

 * ' out from Copenhagen with the intention of carrying 

 out renewed investigations along the Atlantic Slope and in, 

 the Mediterranean. The leader of the new expedition, as. 

 of the earlier Danish expeditions, will be Dr. Johs. 

 Schmidt, who is well known for his previous Atlantic 

 work, especially on the eel, and he will be accompanied 

 by the following men of science : — J. W. Nielsen, hydro- 

 grapher; C. H. Ostenfeld and O. Paulsen, plankton' 

 specialists ; Sven Palitsch, specialist in chemistry from the 

 Carlsberg Laboratory in Copenhagen ; and a biological 

 assistant. The vessel is the research steamer Thor,oi the 

 Danish Government. During the first part of the cruise. 



