THE Royal Sanitary Commission, 1869, summarized the national sanitary minimum necessary for civilized social life as :
- A supply of wholesome and sufficient water for drinking and washing.
- The prevention of pollution of water.
- The provision of sewerage and the utilization of sewage.
- The regulation of streets, highways, and new buildings.
- Healthiness of dwellings.
- The removal of nuisances and of refuse, and the consumption of smoke.
- The inspection of food.
- The suppression of the causes of disease, and regulations in case of epidemics.
- The provision for burial of the dead without injury to the living.
- The regulation of markets, etc., and the public lighting of towns.
- The registration of deaths and of sickness.
The Local Government Board extended this list by adding :
the notification and investigation of infectious diseases ; vital statistics ; vaccination ; poor-law medical services ; sanitary surveys ; housing and town planning ; isolation hospitals ; notification of births ; maternity and child welfare ; mid- wives ; tuberculosis ; venereal diseases ; and international hygiene.
The Ministry of Health again added to the list and co- ordinated these services with health insurance, the school medical service, medical research and treatment, and the medical services of the League of Nations. been used by individuals with impunity, the question of its importance in relation to health and disease came to be more fully recognized as the relation of uncleanliness to disease was understood more fully, and as public water-supplies were introduced. Formerly a sporadic case of disease or death due to the drinking of contaminated water would not be recognized ; but when epidemic disease followed the wider distribution of a water-supply, attention was drawn to the importance of its purity in regard to the health of the com- munity.
Particulars have been collected of more than 50 water- borne outbreaks of typhoid fever in this country between 1864 and 1902. Pollution might occur at any point from the origin to delivery at the house. The outbreak of typhoid fever in Guildford in 1867 was the result of pollution of a shallow well ; those at Caterham in 1879 and at Croydon in 1937 were due to contamination of a deep well ; the Maidstone outbreak in 1897 to pollution of a spring ; of streams and rivers in Lincoln in 1905, of ground water at Terling in 1867, and of the mains of Caius College, Cambridge, in 1873. Other widespread outbreaks the result of water pollution were typhoid fever in Denby Dale, 1932, and at Malton the same year ; and the Broad Street outbreak of cholera in 1854. A very extensive cholera outbreak due to infected water occurred in Hamburg in 1892.
It is now known that the first of the preventive measures in any community is the provision of a sufficient and whole- some water-supply. The improvement in the water-supplies following Snow’s recognition of the relationship of con- taminated water and the Broad Street Pump cholera outbreak is largely responsible for the reduction of the deaths from typhoid fever from 370 per million in 1875 t 0 12 P e r million in 1924. Nor is the improvement limited to this disease, as the incidence of cholera, epidemic diarrhoea, and dysentery also fell.
Water and Disease
While polluted water has often Effective supervision of water-supplies includes control of the sources, gathering grounds, and catchment areas, of the methods of filtration and storage, of the distribution, of adits, and of house cisterns. To this end topographical, bacteriological, and chemical examinations need to be made regularly of all public water-supplies. There can be no relaxation in this supervision. In spite of the improvements, between the years 1911 and 1937 in England and Wales alone there were 21 outbreaks of sufficient importance to be mentioned in the annual reports of the Chief Medical Officer of the Ministry of Health. Of these, faults in storage and distribution accounted for 13 (overground supplies 4, under- ground 9), pollution during storage 2, and pollution during dis- tribution 6. The number of known cases of enteric fever was 1237, of bacillary dysentery 2800, and of gastro-enteritis 7439.
Water may be related to disease as the result of abnormal constituents such as : (a) inorganic salts, which may be responsible for dyspepsia, diarrhoea, or other troubles suffered by newcomers to a district supplied with hard water, or such metals as lead ; (b) organic matter, including vegetable matters which might set up diarrhoea or gastric disturbance ; (c) specific organisms of disease, including those of enteric fever, dysentery, and cholera ; (d) metazoan parasites entering by the mouth, including many varieties of worm.
Contaminated water might result in infections in man by routes other than by mouth, e.g., Weil’s disease or infection by some worms through the skin.
Source of Supply
The important factors in determining the suitability of a source of water-supply are its safety and its certainty of yield. Safety is largely related to the possi- bility of human contamination, and particularly the risk of recent pollution by human dejecta. This may be as obvious as the direct pollution of a surface supply, or as remote as the contamination of a deep-well supply, which only at intervals taps infected adits.
Water may be collected as it falls to the earth (as rain water), from the surface (from rivers or lakes), and after it has percolated to underground levels (from springs and wells). Three-quarters of the population of England and Wales are supplied with water from rivers, streams, and springs ; the remaining one-quarter with water from wells and borings into water-bearing strata.
To ensure the discard of the first fall, which will be con- taminated by having washed the roof, the water is collected by a Roberts’s separator fixed on the downward course of the rain-water pipe, then running to a storage tank.
The water is soft, which renders it suitable for washing, cooking, and bathing, though it is flat and insipid for drinking. It is often highly coloured and contains suspended matter, but if satisfactorily stored is free from human contamination and is therefore safe. Its yield is uncertain.
These are divided into : (i) Land springs, which result from the percolation of water through the superficial porous soil to reach an impervious stratum, and the cropping out of this layer ; and (2) Deep springs, which are formed when water from a higher level passing in water-bearing rock meets fissures in overlying strata and is forced up to the surface.
Spring-water is clear, bright, and palatable ; its contained gases make it sparkle. It is very hard, especially that of deep springs, which contains an excess of salts.
The land spring is liable to pollution, and measures have to be taken to prevent the access of man and animals to its immediate surroundings. T h e yield, too, is uncertain. Main springs are more suitable, being more constant in supply and less liable to pollution.
The water on the first impervious stratum forms an under- ground river below the porous layer of sand, gravel, or sandstone. This water may be tapped at a depth usually of under 50 ft. as a surface well. Water lying on the second or lower impervious layer lying in depths of 100 to 350 ft. may be drawn off from a deep well.
The dissolved solids make the water hard. A surface well, being liable to pollution, is always a doubtful source, the presence of organic matter, especially if associated with an excess of nitrogen, being very suspicious. The deep well is usually a safe supply, though in chalk or limestone the water is liable to pollution through fissures.
Originating partly in streams and partly in springs, river water is a mixture of surface-water, subsoil water, and spring- water. It is usually hard ; moorland streams contain peaty acids. Chemical, physical, and biological processes act as purifying agents ; but although intestinal organisms degener- ate and lose their virulence, river water, while usually good and palatable, is always suspicious.
This water is taken from existing lakes or from reservoirs constructed in hilly districts by damming across the river outlet from the valley. In upland hilly districts the water contains only little dissolved solids, is pure and soft, any organic matter being of vegetable origin. The acids from peat make the water plumbo-solvent. In cultivated lowland districts the water is impure, containing organic matter, etc. The more the water is fed by springs as compared with surface drainage the better the quality. Lakes are liable to pollution by sewage and by traffic. It is desirable that the catchment area has the minimum of inhabitants, of land under cultiva- tion, of works of any kind, and of roads and footpaths.
Apart from those present in the water at source, impurities might find their way in at other stages, e.g., in transit from source to reservoir (surface washings, house, trade, and factory drainage), during storage (by surface washings or soakage or pollution in cisterns), or through faulty distribution. Some impurities in water, though harmless in themselves, are indicative of recent or remote contamination, so the amounts are ascertained in a full chemical analysis. They may be of course of innocent origin. Chlorine which is present may have its origin in the greensand through which the water has percolated and may not be from animal excreta. It is a good indicator, as the figure is uniformly low in the absence of animal pollution. Nitrates and nitrites originate by the oxidation of organic matter, mostly of animal origin. The presence of nitrites may indicate that organic matter is undergoing oxidation which is not yet complete. Ammonia may be present as free or as albuminoid ammonia. The ratio of free to albuminoid is of more importance than the actual amounts of either.
Hardness of Water
This arises from the presence of salts of calcium and magnesium. The acid calcium carbonate is found in almost all well and spring-waters, with an excess in that from chalk, limestone, or dolomite.
Temporary hardness is that capable of reduction by boiling. It is due to the presence of calcium and magnesium carbonates held in solution by carbon dioxide ; on boiling the water this is driven off and the earthy carbonates are deposited. Perma- nent hardness is due to the presence of sulphates or other compounds of calcium and magnesium which are not precipitated on boiling.
Hardness is expressed in degrees, each degree being the equivalent of soap destroyed by ι gr. calcium carbonate in one gallon (Clark’s scale). It is also expressed in the French scale in parts per 100,000. It is estimated by its soap- destroying power. A water of under io° is soft, of 200 hard, and of 300 very hard. Water of hardness of over 300 is almost unusable.
Apart from its effect on the skin and the fact that it renders food slightly less digestible, hardness of water has no effect on health, while it has the advantage of reducing the plumbo- solvent action of the water. It results in soap destruction and in deposits in kettles, pipes, and boilers with risk of explosion and increased fuel consumption.
Natural waters containing appreci- able amounts of metallic constituents are classed as medicinal waters. Some potable waters contain iron. The greatest risk of metallic poisoning by water is from lead. This may be the result of plumbo-solvency or of plumbo-erosion. Chemically soft waters, especially those containing peaty acids, dissolve lead, as do most impure waters. T h e amount dissolved depends on the duration of contact, on the tempera- ture (hot water dissolves more), and on galvanic action. All natural waters contain oxygen in solution which acts on lead, resulting in plumbo-erosion. The remedies of plumbo- solvency or of plumbo-erosion are reducing the acidity of the water ; rendering the water moderately hard ; or substitu- ting or treating the lead pipes.
Purification of Water
Water is subjected to purifying processes firstly to render it safe for drinking and domestic use ; then to render it pleasing in appearance with an absence of suspended matter, odour, or taste, dissolved solids, organic matter, and iron ; and thirdly to render it suitable for indus- trial and household use by removal of hardness and of iron, and by neutralizing acids.
PURIFICATION ON A SMALL SCALE
This can be carried out by :—
- Boiling.—The water is practically sterilized, any resistant spores being those of harmless species. T h e water is flat and insipid to the taste.
- Addition of Chemicals.—Chlorine is added as bleaching powder, as hypochlorous acid, or as the gas. Other chemicals are used as précipitants. They clarify the water, but cannot be relied on to render it safe.
- Filtration.—An unsuitable filter is more dangerous than none, as it converts an intermittent into a constant addition of organisms. A suitable type is the Berkefeld filter, which is a candle of compressed diatomaceous earth in a cylindrical iron case. Water enters the annular space and filters through to the central bore. B. typhosus can grow through in 4 days so the candle needs to be cleaned every 3 days, by boiling in water after preliminary scrubbing.
PURIFICATION ON A LARGE SCALE
Before undergoing purification on a large scale the water will usually receive preliminary treatment. This may be :
ι. Storage.—A 3 or 4 months’ supply is impounded with just sufficient flow to avoid stagnation. Storage results in a reduction in the number of bacteria of all kinds, and in
devitalization of those of water-borne diseases ; and reduces the suspended matter.
2. Sedimentation with Coagulation.—Coagulants accelerate the deposition of fine suspended matters. T h e usual coagulants are salts of aluminium, iron, zinc, and copper. After the addition of the précipitants, the water is allowed to settle for 12 hours. T h e settling coagulants remove suspended matter and reduce the ammonia content.
3. Softening of Hard Water.—In Clark’s method, milk of lime is added by mechanical regulators, after which the water is agitated by stirring blades. Sedimentation for 12 hours then follows in a large sedimentation basin, after which the clarified upper layer is drawn off. In the Porter Clark process, lime is added and the water then filtered under pressure through linen filters. Permanent hardness is removed by the addition of sodium carbonate. In the Atkins process, the filtering cloths are cleaned by revolving brushes.
In the Permutit system, water is softened by being brought into contact with crystals of artificial zeolite obtained from melted felspar, kaolin, sand, and sodium carbonate. In contact with hard water calcium and magnesium are absorbed and sodium freed. The crystals are regenerated by passing through a salt solution when sodium permutit is re-formed, calcium and magnesium being liberated as chlorides.
The essential purification process for most waters is filtration, which may be in slow sand or in mechanical filters.
ι. Slow Sand Filtration.—The filter bed, covered or open,
is rectangular in shape, 200 by 75 ft. and 7 ft. deep. The filtering medium has an average depth of 5 ft., made up of 2 to 3 ft. fine sand on the top lying over fine sifted sand which is separated by another fine sand layer from one of coarse gravel. The head of water is about 2 to 4 ft. The filter is worked intermittently, being in use for 16 hours and resting 8 hours. Cleaning to prevent undue obstruction to flow is necessary every 6 or 8 weeks, and involves removal of the upper i in. of sand.
The essential process is not one of filtration through the sand but is the result of activity in the * vital layer the slimy deposit of fine silt, mud, and low grades of growth which forms on the surface. This layer acts as a filter, but more important is the bacterial activity which results in the peptonization and hydrolysis of the albuminoid by the nitri- fying organisms. Filtration results in the removal of suspended matter, in a reduction of the organic matter and of ammonia, and the removal of 95 per cent of organisms.
2. Mechanical Filtration.—This system employs filters cleaned by mechanical means, by reversed flow of the water coupled with agitation of the filtering medium by paddles or compressed air. The pressure filter is a steel drum with a closed top. The filtering medium is 30 in. of sand or crushed quartz in tall cylinders supported by graded layers of gravel which lie over perforated brass strainers through which the water passes to collection pipes. An artificial film of hydrate of alumina is formed by the addition of alum or of alumino- ferric with or without the addition of lime. T h e physical processes occurring in mechanical filtration are coagulation, sedimentation, and the mechanical arrest of particles by the filtering medium.
It is sometimes advisable to sterilize the water as a final treatment after other methods of purification. The common- est process is chlorination by means of bleaching powder, hypochlorite of sodium, calcium, or magnesium ; liquid chlorine ; chloramine or chlorine peroxide. Super-chlorina- tion, followed by dechlorination, is the best method. Sufficient is added to give a concentration of 4 parts per million for half an hour, followed by dechlorination by sodium thiosulphate. In the excess-lime method, sufficient lime is added above that required to remove the temporary hardness, the period of action being 6 to 24 hours. Other processes are ozonization, treatment by ultra-violet rays, or the addition of chemicals. In the catadyn process water is passed through a filter of catadyn silver which is an activated form of silver deposited on particles of sand.
Distribution of Water,—Water is drawn from the storage reservoirs to the purification works from which it is pumped to the covered service reservoirs. From these it is distributed to the mains throughout the area, passing to individual premises from the mains by service pipes.
The usual standard for this country is 30 gallons per head per day. Of this 17 is for household use, drinking and cooking requiring 1, personal washing 5, dish and house washing 3, laundry 3, W . C.s 5. Trade purposes require 5 ; municipal (including street cleaning, public baths, flushing of sewers, fire extinguishing) 5, and unavoidable waste 3. A bath uses 30 to 40 gallons. The requirements of a hospital are 40 to 50 gallons per inmate daily.
Examination of Water.—A complete investigation of water includes the examination of the source, meteorological conditions, conditions of storage, and the history of any diseases which are supposed to be related to the water-supply. A sample for chemical analysis is collected in a Winchester quart ; for bacteriological analysis, water is collected in an 8-oz. bottle.
The investigation includes : (1) The examination of physical characteristics ; (2) Qualitative and quantitative chemical analysis ; (3) Microscopical examination of sus- pended matter ; (4) Bacteriological examination.
The chemical examination includes testing of the reaction, the residue left on evaporation, chlorides, nitrites, nitrates, phosphates, sulphates, hardness, metallic impurities, free ammonia, and organic matter. A good drinking water should contain not more than 10 parts total solids per 100,000 ; chlorine 1*5 ; hardness 90. The limit in parts per 100,000 of free ammonia is 0-002, of albuminoid ammonia 0-005, a n^ oxygen absorbed o-i. There should be no nitrates or nitrites.
A chemical analysis is of strictly limited value. T h e exact amount or specific nature of pollution is not determinable by chemical analysis ; nor is the test sufficiently sensitive to lead to the detection of pollution by ο·ι per cent sewage or by ι per cent of most effluents.
In bacteriological examination, the full examination consists of the quantitative estimation of the number of organisms growing on media, the isolation and detection of indicator organisms such as B. coli, streptococci, B. enteritidis sporo- genes; and the isolation and identification of pathogenic organisms. In ordinary examinations the main object is to ascertain if excrétai pollution is present. It is not usual to examine for pathogenic organisms. The routine examination for indices of pollution includes agar counts at 20° C. and at 37° C. and a coli-aerogenes count. Most bacteria which grow at 20° C. but not at 370 C. are non-pathogenic to humans. Those growing in 370 C. on agar are generally of soil, sewage, or intestinal origin. T h e coli-aerogenes count or the ‘ pre- sumptive coliform test on lactose bile-salt medium, is the index of pollution in general use. Water containing less than 10 bacteria capable of growing on gelatin at 200 C. in 3 days and with few growing at 370 C. in 24 hours, and which gives no indication of the presence of B. coli group in 100 c . c , can be considered to be of the highest degree of bacterial purity. Water containing in 1 c.c. over 1000 bacteria capable of growing on gelatin at 200 C. in 3 days or over 100 on agar at 37° C. in 24 hours, and which contains typical B. coli in 5 c.c. or less, is probably contaminated with manurial matter. Water should be condemned if it contains large numbers of bacteria of any kind ; B. coli or streptococci in 1 c.c. ; any pathogenic organisms ; or if it gives enteritidis changes in milk cultures or ferments glucose or lactose.
Supply of Water.—There are over 2000 bodies supplying water, about one-half operating by virtue of special or general Acts, most of the others being companies or persons operating without statutory powers. Many municipal authorities pro- vide their own water-supply. An economy both of resources
and of public money would result from an amalgamation of some of the existing undertakings or pooling of resources. The Water Act of 1945 is designed to smooth arrangements to this end.
Responsibility of Local Authorities.—Apart from the responsibility of those authorities which are water under- takers, all local health authorities have certain general duties to take such steps as are necessary for ascertaining the sufficiency and wholesomeness of the water-supply within their districts ; and for securing so far as is reasonably practicable that every house and school has available within a reasonable distance a sufficient supply of wholesome water for domestic purposes. The authority has power, by rejecting plans, to require new houses to be provided with a sufficient water-supply. Under the Factories Act, 1937, the district council can require the supply of domestic water to all persons employed in factories. Local authorities have power to close, or restrict the use of water from, a polluted source (wells, tanks, etc.), and can deal with insanitary cisterns.
Swimming Baths.—Apart from the risk of transmission of those conditions spread by towels and costumes, and any infections whose spread is favoured by the congregation of persons in indoor swimming pools with their warm, still, saturated air, there are some diseases which may be spread by the water. The impurities may be the result of water being drawn from an impure source in the first place ; or being contaminated by the bathers. The presence of organic matter and the warmth of the water favour the multiplication of organisms.
Diseases which are alleged to have been spread in this way are : (1) Intestinal infections, including infective jaundice ; (2) Middle-ear disease—this is probably the result of the spread of organisms via the Eustachian tube from the bather’s throat ; (3) Eye diseases, including conjunctivitis ; (4) Venereal infections ; (5) Respiratory diseases ; (6) Infec- tions of the skin. Fungus infection of the feet is probably contracted from infected footboards.
The water of the swimming pool, after the straining of the coarse suspended matter, is purified by the addition of such coagulants as alum and soda. It then passes through pressure filters and a calorifier. It is re-oxygenated by contact with filtered air in an aerator or by cascading, and is then sterilized by chlorine gas (free chlorine 0-3 to 0-5 parts per million). The period of complete circulation is not more than 4 hours in covered water and 6 hours for open baths.
The water as introduced should conform to the standards of drinking water—i.e., B. coli absent in 1 c.c, and the number of organisms not to exceed 1000 per c.c.
E.W Caryl Thomas, 1948