Introductory. 



main object was to see whether the mechanical 

 analysis of a soil and subsoil would afford data 

 of a suificiently definite character to allow of an 

 approximate calculation being made as to the 

 amount of sewage which that soil and subsoil would 

 purify." (Part II., page 275.) 



" In every case, excepting 



em ca where it is otherwise specified. 



Analysis and ,, , , , , 



standards whole sample of a sewage or 



efiluent — i.e., liquid and solid 

 together — has been taken for analysis. In the case 

 of sewages it is this muddy liquid which the land 

 has to treat, and in the case of effluents it is the 

 resulting mixture (supposing suspended solids are 

 present) which runs into brook or river. The point 

 was carefully considered by the commission at the 

 time when systematic chemical work was begun 

 for them, and the conclusion was arrived at that 

 it represented better the actual state of affairs 

 to analyse an effluent as it was actually discharged 

 than to allow it to settle and then analyse the 

 clear liquid." (Part II., page 2.) " For the con- 

 venience of those who are accustomed to gauge 

 purification by the percentage diminution of albu- 

 minoid nitrogen and ' oxygen absorbed ' from per- 

 manganate, this calculation is given for each set 

 of final and general effluents. But it must not 

 be forgotten that the organic matter of a well-puri- 

 fied effluent is quite different as regards ferment- 

 ability from the organic matter of a diluted sewage 

 showing the same figure for albuminoid nitrogen, 

 and that therefore this calculation — while conve- 

 nient — is purely empirical and unscientific. It is 

 further to be borne in mind that in summer, at 

 all events, the purification of sewage by land is 

 really better than it appears to be on the basis 

 of such a calculation, because of the concentration 

 of the liquid due to absorption by plants and to 

 evaporation." (Part II., page 4.) 



" With respect to effluents, it will be observed 

 that neither in this nor in the Chemical Report 

 has any fixed chemical standard for effluents been 

 specified. ... At the same time it should be 

 said here that in endeavouring to arrive at the 

 quality of any particular effluent, or of the effluents 

 generally, from any one farm, the following points, 

 among others, have been borne in mind : — 



1. The smell of the effluent and its general 

 appearance with regard to colour, solids 

 in suspension, &c. 



2. How the effluent would be judged (speak- 

 ing approximately) by the Mersey and 

 Irwell provisional standard* as regards 

 albuminoid nitrogen and ' oxygen ab- 

 sorbed ' from permanganate (but allow- 

 ing to some extent for the ' oxygen ab- 

 sorbed ' being determined from strong 

 permanganate at 80 deg. Fahr., and not 

 from weak permanganate at 60 deg. 

 Fahr.). 



3. Whether or not it withstood the incubator 



test. 



4. The amount of dissolved oxygen present 



at the time of analysisf and the compari- 

 son of this with the quantity present when 

 the sample was drawn, having regard here 

 also as to whether a surface irrigation or 

 a filtration effluent was in question; 

 further, whether any oxygen remained 

 after incubation either at atmospheric 

 temperature or a temperature of 26"7 deg. 

 C. (80 deg. Fahr.). 



5. The amount of nitrate present, and how 



far that nitrate was reduced upon incuba- 

 tion. 



6. The approximate ratio of oxidised {i.e., 



nitric -f- nitrous) nitrogen to the albu- 

 minoid, and to the total organic nitrogen, 

 and also to the total unoxidised nitrogen." 

 (Part I., page 46.) 



" In the case of drinking-water 

 Bacteriological ,^^,„^j^ t^e standard which I 



„. . . advocate is partial sterilisation. 



Standards. . , ^^ ,. ,, 



the destruction of B. con to the 



extent of securing its absence in 1 c.c. of the efflu- 

 ent being taken as satisfying such standard. Com- 

 plete sterilisation of sewage effluents would not 

 seem to be a practical measure, otherwise this 

 higher standard would be recommended. 



" As regards non-drinking-water streams, the 

 standards which I recommend are provisional and 



* " The well-known Mersey and IrneWprovitional standard, usinf; weak 

 permanganate at 60 deg. Fahr., is 1"43 parts 'oxygen absorbed' per 

 100,000 . . . the equivalent figure for this, when using strong permanga- 

 nate at 80 deg. Fahr., would be about i'i, or, at all events, rather over 

 2 parts per 100,000." (Part 11, page 4, footnote.) " The standard for 

 albuminoid nitrogen is '12 part per 100,000." (Part I, page 62.) 



t " A fully aerated sample would contain roughly about 7 cubic centi- 

 metres of oxygen per litre— i.e., V volumes of oxygen per 1,000 Tolomea 

 of water." 



