41— FURTHER EXPERIENCE IN THE BACTERIAL 

 TREATMENT OF SEWAGE. 



By J. C. S. Beynon, A.M.I.C.E. 



Since writing my paper on the Septic Tank System for the 

 Treatment of Sewage before your Society in 1904, a great advance- 

 ment has been made in its adoption all over the world, and many 

 towns in England which were in the depth of despair as to the 

 disposal of their sewage have been enabled to get over the difficulty 

 and to produce a final effluent so pure that it can be discharged 

 direct into the river, and, in many cases, samples of the river water 

 taken below the discharge of the sewage effluent have on analysis been 

 found to be much purer than samples taken immediately above, 

 thereby proving that instead of having a detrimental effect as hereto- 

 fore, it is highly beneficial. 



In this country, although slow in being generally adopted, it is 

 gradually being accepted as the means for the disposal of sewage, 

 but then, of course, conditions are altogether different, as here the 

 pail system is in vogue, and to alter to the more sanitary water-borne 

 drainage entails a large expenditure in the initial cost, but effecting 

 a great saving in the annual charges, which is an ever-increasing 

 one. On an improvement of the financial conditions of the country, 

 there is no doubt that a much greater advancement will be made in 

 the proper sewering of the towns, as with the increase of population 

 the pail system, with its accompanying disposal of slop water, 

 the annual working costs will make it prohibitive. 



For towns in this country, where land is obtainable, and which 

 is generally the case, the better plan is to merely liquefy the solids 

 in Septic Tanks and then irrigate the land, as water, being so 

 valuable a commodity, it certainly should be made use of and not 

 allowed to run away into the nearest spruit. On the other hand, if 

 land is not procurable or suitable for irrigation, then artificial filtra- 

 tion is necessary for further purification. This can be done on a 

 small area of ground by filter beds, the final object in either case being 

 the same, namely, the oxidation of the organic constituents, and their 

 conversion into stable products incapable of further putrefaction. 



In treating the sewage bacterially, the general method is to run 

 it into tanks, the capacity of which is generally made to hold 24 

 hours' supply. Latterly the view is held that this can be consider- 

 ably reduced, but I think it entirely depends on the strength of the 

 sewage ; if it is in a crude state and not broken down by passing 

 through any great length of sewers, then the full time is required ; 

 on the other hand, if it is kept too long overputrefaction takes place, 

 which means offensive odours. There is no need to cover these tanks 

 unless in close proximity to dwellings, as after a short time of 

 working a scum forms on top, which prevents any smell arising. 

 The gases generated are carbon dioxide, hydrogen, nitrogen, and 

 marsh gas, the latter being as much as 75 per cent. ; this gas is 

 inodourous, and burns freely. Submerged walls and dipping slabs 

 are constructed in the tanks, so that the course of the fluid is 

 alternately ascending and descending. 



