CHEMICAL ANALYSIS 55 



The amount of faeces given in the above figures includes the 

 water associated with them ; the faecal solids insoluble in water 

 and dried free from associated water amount to from one-half 

 to one-third the above, and therefore the quantity of matter 

 required to be brought into solution by a liquefying or hydrolytic 

 process is approximately 20 to 45 parts per 100,000. In 

 chemical processes where sludge is formed, this, being still wet 

 and associated with water, will amount to 60 to go parts per 

 100,000. These are minimum figures, and, of course, in 

 precipitation processes the weight of sludge is increased by 

 the weight of lime or other precipitant mixed with the faecal 

 solids. Road detritus, in the absence of settling tanks, and 

 solids of non-excrementitious origin also frequently cause the 

 above amounts to be exceeded. 



Proposed Standards. — Sewage does not properly include manu- 

 facturing waste liquids. Many authorities prohibit the admis- 

 sion of such refuse into the sewers without preliminary 

 treatment. For example, the West Riding of Yorkshire 

 Act for 1894 included as sewage to be treated by the local 

 authority " unpurified urine, excrementitious matter and liquid 

 refuse of any house or premises, blood and the washings of the 

 slaughter-house containing urinary or faical matter," but 

 excluded any liquid rendered poisonous, noxious, or polluted 

 in the course of some manufacturing process. 



Amongst the standards which have been proposed in the 

 past, or have been adopted by local bodies, are the following, 

 some of which have been repeatedly quoted in papers on the 

 subject, while others are gathered tentatively from published 

 documents, or from a consideration of decisions in disputed 

 cases. None of them, however, have strictly the force of law; 

 in fact, some have actually been disclaimed by the bodies to 

 which they were attributed. The proportions are parts per 

 100,000 : Rivers Pollution Commissioners — organic carbon, 

 2-0 ; organic nitrogen, 0*3. Thames Conservancy — organic 

 carbon, 3*0 ; organic nitrogen, I'l. The Thames Conservancy 

 state that they require a higher standard for effluents above the 

 intakes of the London water-supply than for those below. 

 Derbyshire County Council — albuminoid ammonia, o'l ; 

 oxygen absorbed, i*o.^ Ribble Board — albuminoid, o*i ; 



^ This Council now add: "An effluent should contain more than 0*5 part per 

 100,000 of X as nitrates ; it should be so thoroughly oxidized that it does not 

 absorb more O after incubation for one week than it does at the time of collection ; 

 and — •Shake Test': when shaken vigorously for one minute in a half-filled 



