Land Treatment of Sewage. 



able amount of salphate. One effluent out of two 

 tested showed a small amount of ferrous iron in 

 solution." (Part II., pages 70 and 71.) " It will 

 be seen that the Cambridge sewage farm treats, on 

 a good porous soil and subsoil, an exceptionally large 

 volume of a rather dilute sewage per acre, and at 



effluents failed to pass the suggested biological 

 standards. But the percentage degree of purifica- 

 tion effected in the effluents as compared with the 

 crude sewage was striking ; and as the majority of 

 the effluents either passed or came within measur- 

 able distance of passing the standards laid down. 



BACTERIOLOGICAL ANALYSES (TOTAL NUMBER OF BACTERIA PER CO.). 



Sewage. 

 (4 samples.) 



Effluent.' 

 (14 samples.) 



Stream. 

 (I sample.) 



(1) Gelatine at 20 deg. C 



(2) Agar at 37 deg. C 



(3) B. coll or closely allied forms (say at least) 



(4) B. enteriditis sporogenes (spores — say at 

 least) 



11,990,000 

 1,602,500 



77,500 

 100 



-711 Ana ^ 94 per cent re- ) 

 '^^'^^6 I duction j 



na Qo-T ^ 95 per cent re- ) 

 l^,i£ll auction i 



( Varied from at 

 2,100 \ least 100 to at 

 ( least 10,000 



Varied from at^ 



least 1 but less | 



15^ than 10 to at [- 



I least 100 but 



L less than l.OOOj 



38,000 

 1,400 



10 not 100 



At least 1 but 

 less than 10 



* Satisfactory, (1) 4 ont of 13, (2) 3 out of 14, (3) 3 out of 14, and (4) 2 out of 14 efBuents. 



the same time an exceptionally large absolute 

 amount of organic matter, and produces from it a 

 (dilute) effluent which is usually good, and in some 

 instances exceedingly good. At the same time it is 

 clear that the organic matter left in some of the 

 less purified effluents is of a somewhat putrescible 

 character, as judged by the incubator test, though 

 there is nearly always enough nitrate present to 

 keep the liquid sweet upon incubation." (Part II., 

 page 75.) 



The Bacteriological figures may be summarised as 

 above. 



there is no reason to doubt that land of the kind 

 available at Cambridge could be worked so as 

 uniformly to yield a satisfactory effluent. This 

 would doubtless involve the acquisition of an 

 additional area of land to treat the same volume of 

 sewage ; but the additional amount of land required 

 for this purpose would not in all probability be so 

 great as not to compensate by the improved condi- 

 tion of the effluent for the additional outlay. The 

 very variable quality of the effluents, some being 

 very good, others bad, suggests the possibility, if 

 not the practicability, of obtaining by some means 



" None of the effluents were in a fit state to be 

 turned into a drinking-water stream. As regards 

 non- drinking -water rivers, the majority of the 



uniformly good results. As it appears from Mr. 

 Kershaw's notes that the farm is very well managed, 

 the acquisition of an additional area of land would 



26 



