Cesspits Dry conservancy	Water Carriage (sewers)
dry closets pan systems vacuum system	water closets flush toilets
processed into fertiliser	land disposal (sewage farms)	waterway Disposal (sewage outfalls)
discarded or rare approaches		Preference for ocean disposal

paradigm

The sewerage engineering paradigm is firstly based on water-carriage technology. The struggle between water-carriage technology and dry conservancy methods of dealing with sewage took place in the nineteenth century. Water-carriage technology triumphed on the basis of theories, beliefs and values which were held at that time.

The advocates of both water carriage and dry conservancy methods relied on scientific theories that are largely discredited today. The water-carriage lobby argued that organic wastes had to be removed from places of habitation as soon as possible because if they were given time to putrefy or decompose they would give rise to `miasmas' or disease producing gases which were responsible for the spread of diseases such as typhoid. Water-carriage enabled these wastes to be whisked away immediately whereas dry conservancy methods required that the wastes be stored about the premises.

The dry conservancy enthusiasts believed that it was the solid portion of human wastes which caused the pollution of waterways and which contained the major part of the nutrients. They were concerned that these nutrients be utilised to fertilise the land rather than pollute the waterways. This could be done more effectively if the wastes were not diluted in water and taken to a centralised point, but rather retained in their pure or in an improved form that could be taken to where manure was most needed (Burke, 1873, p21).

Water-carriage technology, which was favoured by many, although not all engineers, involved large scale excavation and construction of sewers as well as the centralisation of sewage for disposal and brought sewage disposal within the engineering domain. It was attractive to the authorities since it made waste disposal a more automatic procedure and a public rather than an individual responsibility. It was felt that the individual could not be trusted. As one text put it,

the lower classes of people cannot be allowed to have anything to do with their own sanitary arrangements: everything must be managed for them.(Corfield, 1871, p118)

The automatic nature of water carriage as opposed to the labour intensive nature of most dry conservancy methods which required the wastes to be regularly collected and carted away was also attractive. Florence Nightingale observed in an 1870 report

The true key to sanitary progress in cities is, water supply and sewerage. No city can be purified sufficiently by mere hand-labour in fetching and carrying. As civilisation has advanced, people have always enlisted natural forces or machinery to supplant hand- labour, as being much less costly and greatly more efficient. (Sewage and Health Board, 1875, p6)

The engineering profession, the medical profession and the authorities made the removal of health-threatening wastes from the cities and towns their first or at least their most public priority and considerations of utilising those wastes as fertiliser or preventing the pollution of waterways were quite secondary, if they were considered at all.

Dry conservancy methods did not reach their peak of popularity till after many sewerage systems were constructed. Their popularity was a result, in fact, of the pollution of waterways that was perceived to accompany water-carriage methods. This lateness on the scene was an immediate drawback since sewers had been installed and had proven to achieve immediate results in decreasing the mortality rate in areas where they were installed. Moreover, the existence of a physical infrastructure of pipes encouraged the continued use of pipes rather than the scrapping of an expensive and proven system in favour of a relatively unproven one.

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References:

Burke, Ulick Ralph, (1873) A Handbook on Sewage Utilization, 2nd ed (London: E & FN Spon).

Corfield, W.H. (1875) Sewerage and Sewage Utilization (New York: D.Van Nostrand).

Sydney City and Suburban Sewage and Health Board (1875) Ô2nd Progress ReportÕ, (Sydney: Sydney City and Suburban Sewage and Health Board).

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