Land Treatment of Sewage. 



The sewage is rather strong 

 Analyses ^^^ ^j^g samples throughout were 



Sewaere, Effluent ,, ,. ^ .^ ■, 



° ' alkaline, some of them very de- 



and Stream. 



cidedly alkaline. The sewage 



arrives at the farm in a fairly fresh condition and 

 not well broken up. It should be noted that the 

 sewage is chemically treated. The chief Chemical 

 results are given on preceding page. 



" One of the effluents was colourless, but most of 

 them had a faint yellow to brownish tinge, the colour 

 being due to organic matter. They contained but 

 little flocculent suspended solids ; in solution there 

 was much lime and much sulphate. The smell, 

 when the effluents came to be analysed, was usually 

 earthy or a mixture of fishy and earthy, and the 

 reaction was alkaline." (Part II., page 222.) " For 

 a farm which must depend mainly upon surface 



by the filtration that takes place through them." 

 (Part II., page 224.) 



The Bacteriological figures may be summarised as 

 below. 



" It is certain that none of the effluents were in a 

 fit state to be turned into a drinking-water stream, 

 and the majority of them could not be considered as 

 altogether satisfactory for discharge even into non- 

 drinking-water rivers. But the fact that some of 

 the effluents were so pure (relatively speaking) * 

 suggests that land of the kind available at Rugby, if 

 it is not overworked, is not incapable of yielding a 

 uniformly good effluent ; if, in short, the area of 

 land available for irrigation purposes is in proper 

 proportion to the amount of sewage to be treated. 

 In conclusion, the majority of the effluents may be 

 said either to have passed or have come within 



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



(1) Gelatine at 20 deg. C 



(2) Agar at 37 deg. C 



(3) B. ooli or closely allied forms (say at 



least) 



(4) B. enteriditis sporogenes (spores— say 



at least) 



Sewage.* 

 (8 samples.) 



24,381,250 

 3,304,375 



77,500 

 775 



Effluent.t 

 (15 samples.) 



A?j7 1 QQ f 97 per cent ■; 



^^••^ [ reduction J 



ai fS'>fi f 97 per cent i 



°^'"-° I reduction J 



( Varied from none in ^ 

 1,881 ] -Ice. to at least ! 

 ( 10,000 ' 



^Varied from none in ~ 

 ) 1 C.C. to at least ( 



19 



; 100 but less than 

 C 1,000 



Stream. 

 (1 sample.) 



156,000 

 7,100 



At least 100 

 Negative 10 c.c. 



* 4 crude, 1 chemically precipitated, 2 screened, settled and precipitated, and 1 settled sewage, 

 t Satisfactory 1 (1), (2) 7, (3) 6 and (4) 6 out of 16 effluents in each case. 



irrigation over a stiff soil, the Rugby high-level 

 farm treats a very large volume of a strong 

 sewage . . . Although the results obtained from 

 the examination of the second-field effluents at 

 Rugby are in several respects contradictory, it will 

 be seen that the farm is capable of producing a fair 

 effluent of very even composition in spring ; but as 

 regards summer, if our (comparatively few) summer 

 samples can be taken as a general criterion of the 

 working of the farm during that season, the area of 

 land which is allowed for sewage then must be 

 smaller than at other times of the year, for it was 

 obviously insufficient. The mechanical analysis of 

 the surface soil showed it to be more of a clay than 

 it was originally thought to be ; but the gravel 

 " pockets " which occur in the clay subsoil no doubt 

 to some extent assist the purification of the sewage 



measurable distance of passing the standards provi- 

 sionally suggested. Therefore with justice it cannot 

 be contended that a heavy loam over stiff clay is 

 wholly unsuited for sewage purification purposes. 

 Percentage, as opposed to actual purification, is 

 misleading, but the remarkable percentage improve- 

 ment in the effluents as compared with the sewage is 

 worth noting ; although it must be admitted that 

 the actual results were not altogether satisfactory." 

 (Part III., page 148.) 



Effluent and 

 Stream Compared. 



The volume of effluent to river 

 water normally is 1 to '60. (Part 

 IV.). [Normal ratio of farm 

 effluent to river water, I to 20 ; ratio at second time 



* " For example, seven out of fifteen effluents contained less than 

 10,000 microbes per c.c. (afi:ar at 37 deg. C). The average number in 

 these samples was less than one-half the standard limit of 10,000 per c.c." 



52 



