Land Treatment of Sewagre. 



by strainers, filtration gutters, &c., is one -which 

 cannot be employed except in those rare instances 

 where constant pressure can be brought to bear, 

 and where it is to the interest of someone continually 

 to look after things." 



BURIED SLUDGE. 



Some of the sludge (dug up in 

 Cambridge. 1901) which had been buried 

 18 in. deep five years previously 

 resembled a dense black clay. Various chemical 

 experiments and analyses were made, and the con- 

 clusion was drawn that sludge should never be buried 

 in masses, but should be thoroughly admixed with 

 the soil in its upper layers. 



SUNDRY NOTES. 



Attention has already been 

 Value of Effluent, drawn to the waste of nitrate 

 and other mannrial constituents 

 in the effluent from the Aldershot Camp farm (see 

 page 15 under the heading " Effluent and Stream 

 Compared"). In the paper " Rural Drainage and 

 Sewage Disposal," referred to on page 65, I raised 

 the point that effluents were valuable (regarded for 

 the moment as water only) for irrigation. On that 

 occasion and previously, February 12, 1900, " The 

 Bacterial Treatment of Sewage " * J made some 

 remarks on the mannrial value of effluents, and I 

 am now more convinced than ever that this branch 

 of the sewage problem — the utilisation of effluents — 

 will prove both practicable and profitable. 



As is well known, sewage when 

 Storm Water, diluted with rain water is at times 

 discharged bymeans of storm over- 

 flows into rivers in the " untreated " condition. For 

 practical reasons it may be impossible to insist on 

 the treatment of more than a few times the dry- 

 weather flow of sewage. But it should be re- 

 membered that sewage diluted even six or more 

 times with pure water would still remain a liquid 

 almost as potentially dangerous to health as normal 

 crude sewage. During the course of the in- 

 vestigation only a few samples of storm water 

 were collected. But since then a fair number of 

 samples has been examined from other places, and 

 the results obtained confirm the truth of the above 

 statements. On the other hand Dr. Houston says, 

 when dealing with Croydon : " It ought to be re- 

 membered that a large access of storm water not 

 only at the time of its introduction affects injuriously 

 • Th« 8ubt«tob, February 16th and 23rd and March 2nd, 1900. 



the working of a sewage farm, but may also so 

 disturb the equilibrium of the biological conditions, 

 which make for purification of the sewage, as to 

 exercise a more lasting prejudicial efiect." (Part III., 

 page 73.) 



The consideration of storm 



«<. .„ M. waters illustrates very clearlv 



Storm Waters. ,, , • , , , , , 



the weak points of what may be 



called an " absolute "* standard for effluents. In 

 connection with this the following experiments were 

 done : Six artificial storm waters were made at 

 different times from Beddington (Croydon) and 

 South Norwood sewages by diluting them down 

 to (a) the Mersey and Irwell provisional effluent 

 standard for albuminoid nitrogen (0"12 part per 

 100,000), or (b) to half that standard (006 part) 

 with tap water ; the latter, of course, contained dis- 

 solved oxygen and, in addition, some nitrate. f 

 These liquids were then allowed to stand for six to 

 twelve days in full bottles, either at laboratory 

 temperature or at 26'7 deg. C. (80 deg. Fahr.). In 

 every case, excepting possibly one (a sample diluted 

 to half the Mersey and Irwell standard), the mixture 

 was eventually found to be putrid. Three other 

 samples were diluted with tap water to the Mersey 

 and Irwell effluent standard for albuminoid nitrogen, 

 and quantities of potassic nitrate were added equal 

 respectively to O'l, 0'2 and 0"3 parts nitric nitro- 

 gen per 100,000 of liquid. After incubation at 

 26'7 deg. C. (80 deg. Fahr.) for seven days these 

 were all found to be putrid. Three more samples 

 were diluted with distilled water to the Mersey and 

 Irwell effluent standard for albuminoid nitrogen, and 

 quantities of ammonium nitrate were added equal to 

 0-3, 0-15 and 0075 part nitric nitrogen per 100,000, 

 the last sample being then diluted further with 

 three volumes of tap water. After incubation for 

 six days all those three solutions were found to be 

 sweet. The results of the above experiments are 

 thus to some extent contradictory, but taken all 

 over they show : (1) That dilution of a sewage with 

 tap water down to the Mersey and Irwell effluent 

 standard for albuminoid nitrogen gives a mixture 

 which putresces upon incubation. In other words 

 Such a mixture is far more liable to putrefaction 

 than an effluent of apparently the same strength as 

 judged by the albuminoid nitrogen test. Even when 

 the dilution is carried twice as far — i.e., down to half 



• The term " absolute " is not really distinctive, but it may serve for 

 want of a better. 



t Two samples of this tap water, examined at a later date, were found 

 to contain approximately 0'25 and 0'30 part of nitric nitrogen per 

 100,000. 



68 



