678 



SEWAGE. 



The commissioners estimate that, for a town 

 where water-closets are in general use (there- 

 fore requiring a larger area than would be re- 

 quired where they are not so mimerous), five 

 acres of filtering surface, and a depth of ma- 

 terial of six feet, are sufficient for a population 

 of 10,000. According to their experiments, 

 something of this depends upon the nature of 

 the soil or other material used for the filter- 

 bed, the qualities of various soils for this pur- 

 pose differing; for while soil procured from 

 Dursley, in Gloucestershire, purified sewage at 

 the rate of 9.9 gallons per cubic yard per day, 

 soil from Hambrook, near Bristol, did not satis- 

 factorily purify more than 4.4 gallons per day 

 per cubic yard. Again, soil from Beddington 

 purified sewage of the same strength at the 

 rate of 7.6 gallons per day, while that from 

 Barking did not purify it at a greater rate than 

 3.8 gallons, or peat from Leyland Moss, near 

 Preston, at a greater rate than 4 gallons per 

 day per cubic yard of material. 



Considering that "filtration" has already 

 often been employed to purify sewage, and 

 has always hitherto failed, it is rather start- 

 ling to see it so confidently recommended, un- 

 til we remember that both the methods of 

 filtration that have failed for sewage also failed 

 for water many years ago; that is to say, the 

 horizontal method and the upward method, 

 while, as soon as the late Mr. James Simpson 

 rearranged the filter-beds of the Chelsea Water- 

 works at Thames Bank many years ago, and 

 made the water to descend instead of ascend 

 through the filtering medium, the question \vas 

 then and thereafter settled as to whether water 

 should be filtered upward or downward. And 

 so the commissioners condemn the system of 

 upward filtration now in practice atEaling, and 

 give the reason why downward filtration is so 

 effective in purifying sewage. The system at 

 Ealing is to force the sewage upward through 

 a filtering medium constantly, thereby effect- 

 ing no proper purification at all ; but by mak- 

 ing the sewage to descend for six or twelve 

 hours through one bed, then shutting it oft* 

 from that bed, or compartment, and turning it 

 on to another for a like space of time, and so 

 alternately, the descent of the sewage through 

 the interstices of the material on either bed 

 is followed by atmospheric air; the air, that 

 is to say, that occupied these interstices be- 

 fore the sewage began to descend, and has 

 .been used up in oxidizing and transforming, 

 and therefore purifying, the former quantum 

 of sewage, is replenished after the descent 

 of each quantum of sewage through each bed, 

 and so by continual periodical renewals of the 

 proper aeration of the filtering medium it be- 

 comes a constant purifier of the sewage ; for, 

 although this method of filtration in the case 

 of water has mostly been called a mechanical 

 one only, yet, in the case of sewage filtration, 

 the same method is said by the commissioners 

 to be both mechanical and chemical. 



In order that there should be no ambiguity 



about what they recommend, and its attain- 

 ment, they give a standard of impurity beyond 

 which they think the water of sewage ought 

 not be admitted into rivers or other water- 

 courses. They suggest that the following 

 liquids be deemed polluting and inadmissible 

 into any stream : 



Any liquid containing, in suspension, more than 3 

 parts by weight of dry mineral matter, or 1 part by 

 weight of dry organic matter in 100,000 parts by 

 weight of the liquid. 



Any liquid containing, in solution, more than 2 parts 

 by weight of organic carbon, or .3 part by weight of 

 organic nitrogen, in 100,000 parts by weight. 



Any liquid which shall exnibit by daylight a dis- 

 tinct color when a stratum of it, 1 inch deep, is 

 placed in a white porcelain or earthen-ware vessel. 



So far the standard is applicable to any 

 tflwn. But the commissioners having before 

 them the question primarily of the pollution 

 of the rivers Mersey and Kibble, which tra- 

 verse the manufacturing part of the county of 

 Lancaster, found it necessary for that district 

 to prohibit suggest, rather, that they should 

 be prohibited many kinds of pollution pecu- 

 liar to the manufactures of those parts, e. g. : 



Any liquid which contains, in solutionj in 100,000 

 parts by weight, more than 2 parts by weight of any 

 metal except calcium, magnesium, potassium, and 

 sodium. 



Any liquid which contains, whether in solution or 

 suspension, in chemical combination or otherwise, 

 more than .5 part by weight of arsenic. 



Any liquid which, after acidification with sulphu- 

 ric acii, contains, in 100,000 parts by weight, more 

 than 1 part by weight of free chlorine. 



Any liquid which contains, in 100,000 parts by 

 weight, more than 1 part by weight of sulphur, in 

 the condition either 01 sulphuretted hydrogen or of a 

 soluble sulphuret. 



Any liquid possessing an acidity greater than that 

 which is produced by adding 2 parts by weight of 

 real muriatic acid to 1,000 parts by weight of distilled 

 water. 



Any liquid possessing an alkalinity greater than 

 that produced by adding 1 part by weight of dry 

 caustic soda to 1,000 parts by weight of distilled 

 water. 



Manchester being within the water-shed of 

 the river-basin inquired into by the commis- 

 sion, it became necessary for them to institute 

 an inquiry into the merits of the privy and 

 ash-pit system, as against the water-closet 

 system, especially as that city is the great 

 stronghold of this first-named system. 



Agreeing with every other impartial inquiry 

 into this subject, the present commission con- 

 demn it. They illustrate the case in a remark- 

 able way. They suppose all dwelling-houses, 

 warehouses, etc., to be removed, and only the 

 privies left nearly 60,000 of them in Man- 

 chester and Salford rows and streets, and 

 crowds of them scattered about almost as 

 thickly in places as the heaps of manure upon 

 a field that has just received a dressing from 

 the dung-carteach heap here, however, no 

 mere barrow-load once a year, but a constant 

 collection and continual soakage of filth, which 

 has for years been polluting every corner to 

 which air or water could have access. Is this 

 the site on which to build a healthy town? 



