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Pollution of the clyde and its tributaries by coal-dross dressings
412
P O L L U T I O N OF T H E
CLYDE.
more easily disturbed after settlement ; and alum The samples of effluent collected since the lime tends to form a certain amount of floating scum ; and ferrous sulphate have been employed, in these are distinct drawbacks to its use So far as accordance with my recommendation, compare clarification of the sewage was concerned, better favourably with those obtained by the previous results were got by ~o grains to the gallon of treatment, and the suggestion has effected a saving lime than by 5 grains of lime and 5 of alum ; Le., in the outlay upon chemical precipitants. there is about equal clarification, but this is more quickly effected. Lime is only about half the price of an equal weight of alum, and the question POLLUTION OF THE CLYDE AND naturally arises as to why the alum should be I T S T R I B U T A R I E S BY C O A L - D R O S S employed at all, and why its place should not be DRESSINGS. ~ BY taken by an equal amount of lime. The only advantages that can possibly accrue JNO. T. WILSON, M.D., D.P.H., County Medical Officer of Lanark. from the use of the alum are the following :--(~) The effluent and sludge from pure lime treatment T~E inspections and reports made during the are strongly alkaline (too strong, in fact, to render year were largely concerned with pollutions by either of much value to vegetation) and the alum coal-dross washings. There are fifty collieries in tends to neutralise this alkalinity. (2) With a the County--eight in the Upper, forty-one in the pure lime effluent there is a tendency for a Middle, and one in the Lower Ward--where this secondary decomposition to set in, with the re'ult process is carried on, and the pollution affects that it gives off offensive smells after standing-various interests. alum tends to check this decomposition and conseAlthough in dross-washing, the object aimed at quent evolution of smells. (3) If too much lime is in all cases the same, viz., the separation of the is employed, some of the offensive matter that was small pieces of coat from coal-dust and earthy originally in suspension gets dissolved, held in matter by elutriation, the methods by which this solution and not precipitated--and a less pure is attained vary considerably. The only important effluent results. difference in the mod~s @erandi I need refer to The next obvious question is whether something here is that which relates to the quantity of water may not be substituted for the alum which will used. give a heavier precipitate which will settle more I n one method commonly employed, the water, rapidly, which will at least equal the alum in its when once charged with detritus, is allowed to flow clarifying and purifying effects, and which will tend away ; while in another the works are so arranged to check secondary decomposition in the effluent that the same water is used over and over again. at least as effectually as the alum. In the latter method the polluted water as disMy experiments with earbferalum, which is a charged is made to flow back slowly through a mixture of alum, protosulphate of iron, and series of settling tanks to the place where it is carbon, furnish results but little better than those utilised, and in its course deposits the greater porfrom an equivalent amount of lime ; but the prototion of the suspended matter before being used sulphate of iron is employed along with lime on again. In such a method, the amount of effluent many farms and also at the sewage outfall works flowing away from the works is comparatively for the Metropolis, and I have carefully gone into small, while the pollution and purification of the the relative powers and merits of this iron salt and water is essentially one process. alum. Of I9 effluents examined during i895 at the I find from many experiments that the protoPublic Health Laboratory, the number of grains sulphate possesses all the advantages (as a per gallon in suspension varied from 7 to 5,Io6 ; precipitant) of the alum, with none of its disof grains per gallon dissolved, from 22 to x54. advantages, and that the results of the employment The amount of solids in suspension indicates of 2~ grains to the gallon of this re-agent are in the extent of the pollution, which, it will be obthe main as efficient as 5 grains of alum, and that served, is very serious in some, while in others the iron excels the alum in its power of keeping there is none. the sludge and effluent sweet. It is necessary that That the pollution is entirely due to solid matter the lime should be added first, so as to ensure in suspension may be seen by allowing a sample of marked alkalinity of the sewage. dross-washings to stand for a few hours, when it To sum up, I find that a mixture of 5 grains t'o separates into a black deposit and a clear supemathe gallon of lime, and 2k grains to the gallon of tant liquid. In the samples examined from four ferrous sulphate give better all-round results than of the above pits, this deposit formed from oneeven Dr. Tidy's recommendation of xo grains of half to ten per cent. of the total volume, the weight lime, and 7 of alumina. of the dried deposit; varied from 66 to over 2~ooo grains per gallon, and, on ignition, was reduced to The cost of lime is . . . . . . about ;£I per ton. ,, protosulphateof iron ,, ~ 2 2s. ,, * From Dr, Witson's Annual Report for I895. ~, alum . . . . . . ~, .£2 ,,
THE
SMALL-POX EXPERIENCE
one-half this amount, showing thereby its organic origin. It is very probable that the amountof suspended matter in dross-washings varies, not only at the different pits, but also at the same pit from time to time. I n twelve of the samples examined, however, the amount of suspended matter is sufficiently large to cause serious pollution. This is also very evident from an examination of the polluted streams, which, for several miles below the pits, are of a black inky eolour, while the bed and margins of the streams are covered with black debris, in some places to the depth of several inches. Whether the nature of the pollution is such as can be dealt with under t h e R i v e r s PoIlution Prevention Act, depends upon the interpretation of the words which occur in Part 3, Sect. 5, of the above A c t - - " Noxious or polluting liquid m a t t e r " ; and again under Sect. ~ o ~ " Polluting shall not include innocuous discolouration." In the application of these words to dross-washing, I would venture the opinion that dross-washings is a noxious and polluting liquid, inasmuch as it renders the stream unfit for primary purposes, including watering of cattle, support of animaI life, domestic use, &c. I t is not a mere innocuous discolouration. I n support of the opinion that dross-washing is a noxious liquid and comes within the scope o f this Act, reference might be made to the Commisioners' Fifth Report, or to more recent experience in a neighbouring county, where compensation has been paid to more than one farmer for loss of cattle, which they alleged died through drinking water from a stream polluted with coal-dross washings. T h e standard of purity to be aimed at, although not determined, should probably be an effluent with not more than ten grains of suspended solids per gallon. Besides the six collieries on the list there are several others in the Middle Ward where the effluent contains less than this quantity of suspended solids, and it would be unfair to those owners who have obtained such results to accept less from others. I n these collieries the means of purification used was settling tanks or ponds, and it is seldom that more than six hours c o ~ l e t e rest has been required for the p u r p o s e - - t h e time suggested by the Commissioners in their Fifth Report. I n nine of the collieries on the list the " r e t u r n " system was employed, in which the amount of water used for washing is reduced to a minimum. Finally, I would observe that the nature of the polluting liquid is such that it can be easily purified by the simple process of settling, provided the tanks are of sufficient capacity, and carefully attended to, or by filtration through refuse bings, which are "practicable and reasonably available m e a n s " for rendering the pollution liquid harmless.
OF BIRMINGHAM.
THE
4T3
SMALL-POX EXPERIENCE B I R M I N G H A M , x893-95.
OF
ALFRED HILL, M.D.s F.R.S.E., M.O.H. of the City of Birmingham.* EIOHT deaths were registered during r895 from small-pox, of which disease just i o o cases were notified to me. T h e year I895 witnessed the end of the great epidemic which commenced in i893, the last case reported having occurred on June egth. From that date to the end of the year the city was entirely free from small-pox. Of the Ioo cases notified, 85 were vaccinated, I4 unvaccinated, and i doubtful. Two of the deaths registered during I895 were in-patients reported in ~894, so that out of the ~oo fresh cases there were 6 deaths, all of them, strange to say, amongst the vaccinated. This is an interesting example of the danger of drawing inferences from a small number of observations. For these figures would appear to show that the case mortality is much higher amongst vaccinated than amongst unvaccinated patients. But the real facts as tO vaccination will be seen from the following figures, which deal with the total number of cases notified from the beginning to the close of the epidemic, that is, from the commencement of ~893 to the middle of x895. No. of Cases.
N o . of Deaths.
Proportion of Deaths to Cases.
Vaccinated ... 2,7or feI 4"5 per cent. Unvaccinated ... 343 I°7 31"2 D, Doubtful ... xo9 2o 18"3 j~ Thus the mortality amongst the unvaccinated cases was really seven times as high as amongst the vaccinated. As the question of vaccination is just now exciting a good deal of interest, I have thought it desirable to look into the above figures a little closely in order to see what is the exact effect of the prophylactic on health and life. I have therefore prepared the following table, the headings of which explain t h e m s e l v e s ' - -
PERIODS.
~
.E
Case Mortality. per cent.
Deaths.
Cases.
,~ I>
59 - -
Under I year
ol 55
i
o
38
I to 5 years ...
I21 65
7
o
25
38
.S to
84] 74
I2
o
5
7
5
i
3
7
I2
21
7
25 to 45 year~im421 4I /35 7 9
I9
4(
31
45 and upwards 2o4~ It ] 19 2I
5
Io years...
I
IO to I5 years i 2641 4o
15 to 25 years IO95 57 30
20
'
* From Dr. A. Hill's Annual Report for *895.
--
P O L L U T I O N OF T H E
CLYDE.
more easily disturbed after settlement ; and alum The samples of effluent collected since the lime tends to form a certain amount of floating scum ; and ferrous sulphate have been employed, in these are distinct drawbacks to its use So far as accordance with my recommendation, compare clarification of the sewage was concerned, better favourably with those obtained by the previous results were got by ~o grains to the gallon of treatment, and the suggestion has effected a saving lime than by 5 grains of lime and 5 of alum ; Le., in the outlay upon chemical precipitants. there is about equal clarification, but this is more quickly effected. Lime is only about half the price of an equal weight of alum, and the question POLLUTION OF THE CLYDE AND naturally arises as to why the alum should be I T S T R I B U T A R I E S BY C O A L - D R O S S employed at all, and why its place should not be DRESSINGS. ~ BY taken by an equal amount of lime. The only advantages that can possibly accrue JNO. T. WILSON, M.D., D.P.H., County Medical Officer of Lanark. from the use of the alum are the following :--(~) The effluent and sludge from pure lime treatment T~E inspections and reports made during the are strongly alkaline (too strong, in fact, to render year were largely concerned with pollutions by either of much value to vegetation) and the alum coal-dross washings. There are fifty collieries in tends to neutralise this alkalinity. (2) With a the County--eight in the Upper, forty-one in the pure lime effluent there is a tendency for a Middle, and one in the Lower Ward--where this secondary decomposition to set in, with the re'ult process is carried on, and the pollution affects that it gives off offensive smells after standing-various interests. alum tends to check this decomposition and conseAlthough in dross-washing, the object aimed at quent evolution of smells. (3) If too much lime is in all cases the same, viz., the separation of the is employed, some of the offensive matter that was small pieces of coat from coal-dust and earthy originally in suspension gets dissolved, held in matter by elutriation, the methods by which this solution and not precipitated--and a less pure is attained vary considerably. The only important effluent results. difference in the mod~s @erandi I need refer to The next obvious question is whether something here is that which relates to the quantity of water may not be substituted for the alum which will used. give a heavier precipitate which will settle more I n one method commonly employed, the water, rapidly, which will at least equal the alum in its when once charged with detritus, is allowed to flow clarifying and purifying effects, and which will tend away ; while in another the works are so arranged to check secondary decomposition in the effluent that the same water is used over and over again. at least as effectually as the alum. In the latter method the polluted water as disMy experiments with earbferalum, which is a charged is made to flow back slowly through a mixture of alum, protosulphate of iron, and series of settling tanks to the place where it is carbon, furnish results but little better than those utilised, and in its course deposits the greater porfrom an equivalent amount of lime ; but the prototion of the suspended matter before being used sulphate of iron is employed along with lime on again. In such a method, the amount of effluent many farms and also at the sewage outfall works flowing away from the works is comparatively for the Metropolis, and I have carefully gone into small, while the pollution and purification of the the relative powers and merits of this iron salt and water is essentially one process. alum. Of I9 effluents examined during i895 at the I find from many experiments that the protoPublic Health Laboratory, the number of grains sulphate possesses all the advantages (as a per gallon in suspension varied from 7 to 5,Io6 ; precipitant) of the alum, with none of its disof grains per gallon dissolved, from 22 to x54. advantages, and that the results of the employment The amount of solids in suspension indicates of 2~ grains to the gallon of this re-agent are in the extent of the pollution, which, it will be obthe main as efficient as 5 grains of alum, and that served, is very serious in some, while in others the iron excels the alum in its power of keeping there is none. the sludge and effluent sweet. It is necessary that That the pollution is entirely due to solid matter the lime should be added first, so as to ensure in suspension may be seen by allowing a sample of marked alkalinity of the sewage. dross-washings to stand for a few hours, when it To sum up, I find that a mixture of 5 grains t'o separates into a black deposit and a clear supemathe gallon of lime, and 2k grains to the gallon of tant liquid. In the samples examined from four ferrous sulphate give better all-round results than of the above pits, this deposit formed from oneeven Dr. Tidy's recommendation of xo grains of half to ten per cent. of the total volume, the weight lime, and 7 of alumina. of the dried deposit; varied from 66 to over 2~ooo grains per gallon, and, on ignition, was reduced to The cost of lime is . . . . . . about ;£I per ton. ,, protosulphateof iron ,, ~ 2 2s. ,, * From Dr, Witson's Annual Report for I895. ~, alum . . . . . . ~, .£2 ,,
THE
SMALL-POX EXPERIENCE
one-half this amount, showing thereby its organic origin. It is very probable that the amountof suspended matter in dross-washings varies, not only at the different pits, but also at the same pit from time to time. I n twelve of the samples examined, however, the amount of suspended matter is sufficiently large to cause serious pollution. This is also very evident from an examination of the polluted streams, which, for several miles below the pits, are of a black inky eolour, while the bed and margins of the streams are covered with black debris, in some places to the depth of several inches. Whether the nature of the pollution is such as can be dealt with under t h e R i v e r s PoIlution Prevention Act, depends upon the interpretation of the words which occur in Part 3, Sect. 5, of the above A c t - - " Noxious or polluting liquid m a t t e r " ; and again under Sect. ~ o ~ " Polluting shall not include innocuous discolouration." In the application of these words to dross-washing, I would venture the opinion that dross-washings is a noxious and polluting liquid, inasmuch as it renders the stream unfit for primary purposes, including watering of cattle, support of animaI life, domestic use, &c. I t is not a mere innocuous discolouration. I n support of the opinion that dross-washing is a noxious liquid and comes within the scope o f this Act, reference might be made to the Commisioners' Fifth Report, or to more recent experience in a neighbouring county, where compensation has been paid to more than one farmer for loss of cattle, which they alleged died through drinking water from a stream polluted with coal-dross washings. T h e standard of purity to be aimed at, although not determined, should probably be an effluent with not more than ten grains of suspended solids per gallon. Besides the six collieries on the list there are several others in the Middle Ward where the effluent contains less than this quantity of suspended solids, and it would be unfair to those owners who have obtained such results to accept less from others. I n these collieries the means of purification used was settling tanks or ponds, and it is seldom that more than six hours c o ~ l e t e rest has been required for the p u r p o s e - - t h e time suggested by the Commissioners in their Fifth Report. I n nine of the collieries on the list the " r e t u r n " system was employed, in which the amount of water used for washing is reduced to a minimum. Finally, I would observe that the nature of the polluting liquid is such that it can be easily purified by the simple process of settling, provided the tanks are of sufficient capacity, and carefully attended to, or by filtration through refuse bings, which are "practicable and reasonably available m e a n s " for rendering the pollution liquid harmless.
OF BIRMINGHAM.
THE
4T3
SMALL-POX EXPERIENCE B I R M I N G H A M , x893-95.
OF
ALFRED HILL, M.D.s F.R.S.E., M.O.H. of the City of Birmingham.* EIOHT deaths were registered during r895 from small-pox, of which disease just i o o cases were notified to me. T h e year I895 witnessed the end of the great epidemic which commenced in i893, the last case reported having occurred on June egth. From that date to the end of the year the city was entirely free from small-pox. Of the Ioo cases notified, 85 were vaccinated, I4 unvaccinated, and i doubtful. Two of the deaths registered during I895 were in-patients reported in ~894, so that out of the ~oo fresh cases there were 6 deaths, all of them, strange to say, amongst the vaccinated. This is an interesting example of the danger of drawing inferences from a small number of observations. For these figures would appear to show that the case mortality is much higher amongst vaccinated than amongst unvaccinated patients. But the real facts as tO vaccination will be seen from the following figures, which deal with the total number of cases notified from the beginning to the close of the epidemic, that is, from the commencement of ~893 to the middle of x895. No. of Cases.
N o . of Deaths.
Proportion of Deaths to Cases.
Vaccinated ... 2,7or feI 4"5 per cent. Unvaccinated ... 343 I°7 31"2 D, Doubtful ... xo9 2o 18"3 j~ Thus the mortality amongst the unvaccinated cases was really seven times as high as amongst the vaccinated. As the question of vaccination is just now exciting a good deal of interest, I have thought it desirable to look into the above figures a little closely in order to see what is the exact effect of the prophylactic on health and life. I have therefore prepared the following table, the headings of which explain t h e m s e l v e s ' - -
PERIODS.
~
.E
Case Mortality. per cent.
Deaths.
Cases.
,~ I>
59 - -
Under I year
ol 55
i
o
38
I to 5 years ...
I21 65
7
o
25
38
.S to
84] 74
I2
o
5
7
5
i
3
7
I2
21
7
25 to 45 year~im421 4I /35 7 9
I9
4(
31
45 and upwards 2o4~ It ] 19 2I
5
Io years...
I
IO to I5 years i 2641 4o
15 to 25 years IO95 57 30
20
'
* From Dr. A. Hill's Annual Report for *895.
--