Introductory. 



is employed. Moreover, the term ' surface ' irri- 

 gation seems to define what takes place better 

 than the expression ' broad ' irrigation." (Part I., 

 page 23.) 

 Distance from ^^^ following passage sums up 



Town— ^^^ position with regard to the 



Advantages and proximity to towns of sewage 



Disadvantages, disposal works. The possibility 

 of nuisance is, of course, greater 

 with sewage farms than with bacterial installations, 

 but must in any case be taken into account. 



" The advantages on the one hand, and the dis- 

 advantages on the other, of having a sewage farm at 

 some considerable distance from the town sewered 

 may be summed up as follows: Advantages. — The 

 whole of the sewage may be run on to the land 

 in a disintegrated and partially decomposed con- 

 dition, without any preliminary treatment. In 

 special cases rough screening and settlement of the 

 grit may have to be resorted to. There are senti- 

 mental, if not also health, considerations for treat- 

 ing sewage in thinly-populated districts. The land 

 is likely to be cheaper in sparsely-populated dis- 

 tricts. There is less likelihood of difficulty in ex- 

 tending the area of the farm to keep pace with 

 a growing population. The longer the outfall 

 sewer, the more likely is the sewage to have a 

 uniform composition and an equable flow. Dis- 

 advantages. — The solid faecal matter which, taken 

 by itself, has a definite manurial value, and would 

 otherwise be easily manipulated, and the cellulose 

 matters, which have a clogging tendency, pass on 

 to the land with the watery part of the sewage, 

 whereas in the case of fresh sewage it is not diffi- 

 cult to screen out much of the solid fsecal matter 

 and a certain amount of the paper, and to dispose 

 of it to farmers or to make use of it on the farm 

 itself. If settling tanks and precipitation methods 

 are in operation the sludge is apt to be of small 

 market value and is not readily disposed of. The 

 longer the outfall sewer (1) the greater the initial 

 cost; (2) the greater the cost for repairs; and (3) 

 the larger the amount of subsoil water likely to 

 gain access to the sewer, which, so far as bulk of 

 liquid to be disposed of is concerned, is a positive 

 disadvantage. 



" The distance of a sewage farm from the town 

 sewered is usually governed by practical con- 

 siderations; for example, by the suitability of the 

 soil, the necessity for avoiding piunping, if pos- 



sible, (fee. The subject is one concerning which it is 

 obviously impossible to pronounce any decided 

 opinion, but in general cases there would, on the 

 whole, seem to be a clear advantage in having a 

 sewage farm at a considerable distance from the 

 town sewered." (Part I., page 8.) 



The total acreage must be re- 

 Surplus Area— , . . , , °^ . 



Value of. latively much greater for surface 



irrigation than for deep filtra- 

 tion, and a sewage farm may be so small as to be 

 economically a failure. The extent of the sur- 

 plus area is a matter of some concern. " It is 

 impossible to lay down any rule as regards what 

 the ratio of the surplus to the total acreage should 

 be. Each case must be judged on its own merits, 

 and in relation to the local conditions. But we 

 are of opinion that, generally speaking, a large 

 surplus acreage is advisable, and it is naturally 

 of great advantage to have this surplus land so 

 circumstanced as to admit of the possibility of its 

 being inexpensively laid out for irrigation pur- 

 poses, if required." (Part I., page 10.) 



"Whether it is better to have 

 Separate 



(Partially) ^ separate or a combined sewer- 

 System- *S^ system is a controversial 

 Advantages and matter, and we content ourselves 

 Disadvantages, by briefly referring to some of 

 the advantages and disadvantages 

 of each system. As we have been careful to 

 point out elsewhere, ' street washings ' (liquid from 

 the separate system) may be so impure as to render 

 its discharge into rivers undesirable. Since the 

 separate system is seldom carried out in its en- 

 tirety, we confine our remarks to the partially 

 separate sewerage system. For the sake of sim- 

 plicity our comments may be confined to a brief 

 consideration of the advantages and disadvantages 

 of the separate system. Advantages. — Fluctuations 

 in the sewage flow at the outfall works are re- 

 duced during storms. The road detritus is kept 

 out of the sewers. A smaller area of land is re- 

 quired for irrigation purposes at a time when the 

 soil of the sewage farm is already apt to be satu- 

 rated with rain water. The routine working of 

 the sewage farm is not embarrassed by frequent 

 fluctuations in the volume of sewage, amounting 

 it may be to three or four times the normal. If 

 the sewage is pumped, the extra cost of dealing 



