Land Treatment of Sewage. 



advocate of no one system is in a position to judge 

 dispassionately of the merits of his own as com- 

 pared with other schemes. It may well be that the 

 results from his particular method of treatment will 

 be eminently satisfactory from the purification 

 standpoint ; but it is possible that a like success 

 might have been achieved at less expenditure by 

 some other system. 



In the case of the improvement of existing sewage 

 works the problem is much less complicated. Efflu- 

 ents may no longer pass muster, on the one hand, 

 because of the extra burden due to increased popula- 

 tion and extended or additional industrial activity, 

 and, on the other hand, on account of the greater 

 degree of purification now enforced — in some in- 

 stances both causes may have contributed to the 

 result. It is interesting to note what has been 

 done at the eight selected farms in this respect. 

 At Aldershot Camp the water supply has been 

 reduced and the farm is unchanged ; Altrincham 

 and Nottingham have extended their boundaries ; 

 Cambridge is turning the plots into " bacterial 

 areas " ; Croydon, Leicester and South Norwood 

 have adopted preliminary bacterial treatment (the 

 works at Leicester being designed to effect a purifi- 

 cation of 71 per cent before the land is utilised) ; 

 and Rugby has a scheme in hand, rendered neces- 

 sary by the diminution of the area available, though 

 even had that not occurred additional accommoda- 

 tion would no doubt have been required. It would 

 have been very instructive had the Corporation of 

 Croydon attempted to use the land at Beddington 

 as a filtration farm. 



The Local Government Board's (England) sanction 

 to a loan for sewage treatment is usually conditional 

 upon the purification of six times the dry-weather 

 flow, three volumes as sewage proper and three 

 volumes (less efficiently) as storm water. At the 

 date of the reports Aldershot Camp (separate), 

 Altrincham (combined) and Nottingham (combined) 

 treated very little ; Cambridge (partially separate) 

 a small amount ; Leicester (combined) two and a 

 half times the dry-weather flow ; Rugby (partially 

 separate) nearly all ; and Croydon (partially sepa- 

 rate) and South Norwood (partially separate) all 

 from the sewers. When the flow is greatest the 

 land receives most extra water in the form of rain, 

 and as a rainfall of 1 in. represents 22,620 gallons 

 per acre the burden on land as compared with bac- 

 teria beds, where such an amount would be a neglig- 

 able quantity, is a factor of no mean importance. 

 The additional information afforded upon the 



character of the soils and subsoils in use or likely 

 to be used for sewage disposal is most welcome. 

 The tables of " mechanical analysis " are the more 

 useful as they indicate where so many errors of 

 judgment have in the past been committed. The 

 late Mr. Bidder is reported to have said on one 

 occasion, when referring to the regulations of the 

 Local Government Board, that he supposed an acre 

 of ducks' backs would be treated exactly like an 

 acre of road metalling or porous gravel. One 

 instance may be quoted in support of Mr. Bidder's 

 contention, and it is taken from the evidence given 

 to the Commission on January 19, 1899, by Dr. 

 Sidney Barwise, county medical officer of Derby- 

 shire. " I say this stiff clay land cannot act as 

 an intermittent filter. Loans are sanctioned to lay 

 it out for intermittent filtration, and it is laid out, 

 but it is a physical impossibility to filter through 

 material which is used to puddle the banks of 

 resprvoirs with. Brampton is a case in point of 

 what is called intermittent filtration ; the loan was 

 sanctioned for intermittent filtration, and the only 

 way the sewage goes through the clay is through 

 the worm-holes and the cracks as I have described." 

 The sewage is not treated before it is applied to the 

 land. Care must be exercised to guard against the 

 pernicious habit of considering only one or two 

 factors in the complicated question of sewage dis- 

 posal. A soil, comparable to one of those reported 

 on, may not be able to accomplish more than a 

 fraction of the purifying power recorded — the 

 sewage may differ in strength and in amount and 

 the volume of storm water to be treated may be 

 many times as g^eat. 



We still await the final report of the Royal Com- 

 mission on Sewage Disposal, which will deal inter 

 alia with the extremely valuable reports forming 

 the subject of these articles. Sewage farming is 

 beset with many difficulties, and some of these must 

 have been apparent to my readers even if they were 

 not personally acquainted therewith beforehand. It 

 may be said without fear of contradiction that where 

 the soil is suitable, the flow not overmuch, and the 

 management competent, a sewage farm can produce 

 excellent results. To what extent alterations should 

 be made to existing farms where inefficient, and land 

 should be employed at new outfalls are matters that 

 depend entirely upon local conditions. It is only 

 when these have been ascertained and have been 

 duly considered by an independent expert that the 

 true solution of the particular problem in question 

 can be obtained. 



76 



" OF THE 



UNiVER3iTY / 



Of 



