Introductory. 



with such increases of flow due to Btorm water, as 

 are dealt with at the disposal works, is consider- 

 ably lessened. A saving of cost would also seem 

 to occur in precipitation schemes. In districts 

 where the rainfall is heavy, the rain water is car- 

 ried rapidly away, and flooding of the low-lying 

 levels of the town is less likely to occur. Sewers 

 even of a large capacity may be quite incapable 

 of dealing satisfactorily with these sudden fluctua- 

 tions of flow. Disadvantages. — The occasional 

 natural flushing out of sewers is lessened. Never- 

 theless, it is chiefly during dry weather that the 

 sewers require flushing. The dilution of the 

 sewage with rain water is lost to some extent, 

 but against this must be put the increase of total 

 volume of liquid to be dealt with at places where 

 the combined sewerage system is in use, and the 

 fact that ' street washings ' per se iD.a,y be of ob- 

 jectionable quality. Instances are not unknown 

 when, through carelessness, the foul-water house 

 drains have been connected up to the pipes of the 

 separate system. The initial cost and mainten- 

 ance are greater with the separate system, but 

 whether this disadvantage is not more than counter- 

 balanced by, among other things, the larger volume 

 of liquid to be ' treated ' at the disposal works, 

 is a difficult point to determine. 



" If it were practicable to carry oflF all the storm 

 water rapidly, and, in addition, to treat efficiently 

 the whole of the combined volume of storm water and 

 sewage at the disposal works, then it is obvious that 

 the combined system would be preferable. But as 

 this would seem to be impracticable, the question 

 largely resolves itself into whether it is better to 

 have (a) a combined system with the storm overflows 

 working at low dilutions, or (6) a separate system 

 with storm overflows coming into operation only 

 very exceptionally — i.e., at higher dilutions. We 

 have not sufficient data to formulate a decided 

 opinion, the more so since adequate records are 

 not available of the average quality of the liquids 

 under (a) and (b) sets of conditions, the results 

 being interpreted in the light of the analyses of 

 ' street washings ' liquid per se." (Part I., pages 

 27 and 28.) 



" There can be no doubt that 

 Management, even the best of sewage farms 



with the most suitable soil will, 

 under continued bad management, fail to turn out 

 a satisfactory effluent. The question of whether 



or not a particular farm is going to purify the 

 sewage efficiently depends mainly upon the man- 

 ager, assuming, of course, that the farm has been 

 properly laid out in the first instance, that it has 

 a reasonable volume of sewage to treat, and that 

 the manager has (within certain limits) a free hand 

 in the supervision of sewaging operations. The 

 fact, however, must not be lost sight of that he 

 has often a most difficult post to fill, especially 

 with regard to the crops. The effectual purifica- 

 tion of sewage, even with suitable land, can only 

 be accomplished when the farming operations are 

 relegated to the background, and the production of 

 a good effluent considered of primary importance. 

 On the other hand, the manager knows that the 

 crops will probably form an important item in 

 his receipts at the end of the year, and he not un- 

 naturally wishes it to appear that the farm is 

 being worked economically under his supervision. 

 Hence there is a temptation to grow remunerative 

 crops — e.g., cereals — that cannot be sewaged (at 

 all events for the greater part of the year), or to 

 refrain from the further sewaging of crops which 

 may be damaged thereby; meanwhile the land 

 which is under sewage must needs yield, owing 

 to the lack of rest, increasingly unsatisfactory efflu- 

 ents. There may, of course, be some farms where 

 the large area at command in proportion to the 

 volume of sewage to be ' treated ' renders the 

 growing of grain crops justifiable, but these are 

 exceptions to the general rule. Land is usually 

 too expensive in the immediate vicinity of towns 

 to allow of this, and the tendency is to take too 

 little rather than too much land for a sewage farm. 

 Speaking generally, large farms are better man- 

 aged than small ones, this being in great measure 

 due to the fact that the salary attached to the 

 latter does not always offer sufficient inducement 

 to a competent man to undertake the duties. In 

 many instances there are small districts fairly 

 near together, each with its own sewage farm. In 

 such cases a combined scheme would appear to be 

 advantageous ; by adopting this course an adequate 

 salary could be paid so as to secure an efficient 

 manager, while the annual cost of treating the 

 sewage would also be lessened. On the other hand, 

 it is possible to have a sewage farm so large as 

 in a sense to be unwieldy. It seems desirable 

 that managers should employ day by day some 

 simple chemical test or tests to enable them to 



