History of Sewage Treatment

Citation: Sharon Beder, From Sewage Farms to Septic Tanks: Trials and Tribulations in Sydney, Journal of the Royal Australian Historical Society, vol. 79, parts 1 and 2, 1993, pp. 72-95.

This is a final version submitted for publication. Minor editorial changes may have subsequently been made.

CONCLUSION

During the second half of the nineteenth century sewage treatment methods developed rapidly. Debate over which methods were best was often heated and appeared not only in engineering journals but also in scientific journals, popular magazines and newspapers. Many books were written, often by lawyers and medical men as well as by engineers. By the early twentieth century this had changed. Sewage treatment had become the expert domain of an engineering profession which had reached a consensus about treatment methods. The debate had all but died. Sewage treatment became identified in stages, primary and secondary (and later tertiary). Each stage has one or two conventional treatment technologies associated with it. Public debate has tended to focus on the stage of treatment required rather than how that stage is achieved.

This paper uses the Sydney sewerage system as a case study and explores the role of the British Royal Commission into Sewage Disposal (1898-1915) in facilitating these changes in the way sewage treatment is viewed. In Sydney in the 19th Century, in places where ocean disposal was too expensive in the short term, some of the more popular treatment methods developed overseas were experimented with. In its final report in 1877 the Sydney Sewage and Health Board decided that the southward draining city sewage and that of the southern suburbs should be taken to a sewage farm on the edge of Botany Bay.[1]

The sewage farm was to be an experiment which, if it failed, would not be wasted since the sewers could be continued overland to the open sea. The land could be sold and the outlay to take the sewage to the farm would fit into "any scheme adopted hereafter".[2] Moreover, the lobby for utilisation of the sewage as fertiliser was fairly strong at that time in Sydney and the sewage farm experimentation had the added bonus of placating that lobby. One member of the Sewage and Health Board pointed out,

I feel sure the inhabitants of this city would be more satisfied to go to the expense of a second great sewer when they know that sewage farms will not answer. I do not think they will be satisfied until the experiment has been made.[3]

Many Sydney-siders had been impressed by the "immense" vegetables produced by Chinese market gardeners who made use of sewage as a fertiliser without any ill-effects.[4] An anonymous poet in the Evening News extolled the benefits of sewage farms.

Dear people! thus to fill my maw, By outrage of just Nature's law!- If you but us'd your city's filth To fatten crops, and feed their tilth, Till Nature turning "vile" to "good", Returned your waste in fruit or food! Your farms and fields would gain in wealth, Whate'er your city wins in health, And lustier crops and lengthening lives Would prove how sense, with science thrives.[5]

However support for sewage farming was far from unanimous and the debate within the Sewage and Health Board reflected to some extent the debate going on in the wider community over sewage farms. Members of the Board were unsure about a sewage farm because of the reported experiences of sewage farms overseas and one member argued that it would become a "permanent nuisance, very offensive and dangerous to the health" and that there was a real risk of disease being caused by eating produce grown on a sewage farm.[6] The main community opposition to the idea came from those living near the proposed location of the farm. In 1880, at a meeting of mayors of suburban municipalities held to discuss the scheme, one mayor called the scheme for draining the southern suburbs of the city "one of the most monstrous proposals that was ever suggested by any Government." He pointed out that the location intended for a sewage farm was "a perfect swamp". Another agreed that the idea was "a most monstrous one".[7] Shortly afterwards, a deputation, claiming to represent 40,000 people went to see the Minister for Works to protest against the plan for the southern draining sewage.[8]

The debate amongst self-proclaimed experts both in Australia and overseas over the best means of disposing of or treating sewage was quite fierce. Burke, an English barrister, wrote in 1873 that

a well-known sanitary reformer once said to us that he knew only one topic besides polemics upon which men's party spirit got the better of their good sense, and even of their regard for truth and justice, and that was the treatment of sewage.[9]

This led to the most confusing discrepancies in the statistics, Burke observed, so that whilst one authority might show that a sewage farm was unhealthy to neighbouring residents, another would show the death-rate in the area had decreased markedly since the establishment of the farm. The value of the manure was also a subject of vigorous debate, Burke noted.[10](The debate over the economics of sewage farming in the US at this time is covered by Tarr.[11])

In Sydney, Mr Watt, the Government Analyst, argued that waterborne sewage had very little manurial value and should be disposed of into the sea where possible.[12] W. Clark, a visiting English engineer, claimed that no process of turning sewage into manure had been a financial success and in Sydney, where labour was expensive, it was even less likely to be profitable.[13] A Tasmanian engineer argued that "every pound gained in a year by a sewage farm is gained by a yearly expenditure of more than a pound either in labour or in interest upon capital expended."[14] Burke himself pointed out that in England at the time an enormous amount of manure was imported and artificially manufactured. Guano was imported from Peru and other islands and the Peruvian government was already concerned that the deposits would soon be exhausted. The market for artificial fertilisers was also immense, he said.[15]

Burke also noted that the efficacy of sewage farming was hotly debated by the experts. "One would think that when we had reached the region of pure science a calm voice would speak from the laboratory in the unprejudiced tones of perfect accuracy".[16] But no, each scientist found differing amounts of nitrogen and reached different conclusions. [17]

The inability to resolve these controversies over technical points would later be typical of controversies over chemical precipitation, artificial filters and septic tanks, were all symptoms of an immature field of study which had not been fully colonised by a professional group with its own paradigm.

SYDNEY SEWAGE FARMING

The Sydney Sewage and Health Board recommended that the southward draining sewage not be used for broad irrigation but that it be treated by a method known as "intermittent downward filtration".[18] This method used the land as a filter through which the sewage drained. Crops could be grown on the land which would be richer after the sewage had filtered through but this was a secondary consideration since the primary purpose of the Board was to purify the sewage effluent before it went into Botany Bay rather than to utilise the sewage as a fertiliser. The advantage of this method was that it took up far less land than for broad irrigation, a process in which the sewage was used to irrigate the soil and was directly taken up through the roots of the vegetation. It was being increasingly used in towns and cities in Britain and the United States where land was often scarce and the ocean distant. The situation was somewhat different in the newly established city of Sydney but the perception of the value of intermittent downward filtration overseas was transferred to Australian engineers.

The underlying preference for ocean disposal and the experimental nature of the sewage farm determined the location of Sydney's farm. It was placed on the north-west corner of Botany Bay, on the way to the sea. The site was composed of low-lying, raw drift sand and covered in scrub. The land had already been purchased by the government for the purpose of dumping nightsoil and it was a location from which a sewer main could easily be extended to the coast should the experiment fail.

In 1882 309 acres were resumed by the Government for disposal of sewage. Before the sewage farm was fully operational, George Stayton, an engineer with the sewerage branch of the Roads and Bridges Department and a man "of considerable English experience"[19] recommended that the sewage of the western suburbs of the city also be channelled onto the sewage farm.[20]

By the time Stayton reported the Adelaide sewage farm, in South Australia, had been established and was just beginning to make a profit. It had 470 acres which were irrigated with the city's sewage and in the Winter intermittent-downward filtration was also used because of the extra rainfall. Stayton said the Adelaide farm

shows that liquid sewage is an especially valuable fertilizer in a hot climate, and that under good management, a substantial income can eventually be derived from grazing and fattening stock and from the growth and sale of root crops, fodder, plants, fruit and vegetables.[21]

Sewage was first turned on to the Sydney farm in 1887. In the first years of operation of the Botany Sewage Farm about 1.5 million gallons of sewage would arrive at the farm each day and transported to the irrigation beds which took up 34 acres at one end of the farm. The irrigation beds were at different levels separated by earthen banks and with filtration drains which channelled the effluent to the Cooks River. These beds were each flooded with effluent in rotation and, while not in use, they were cultivated with the sewage sludge which was ploughed into them.[22]

At first the sewage farm was a great success. On the cultivated land the Board's employees produced cabbages, turnips, lucerne and sorghum and this produce was readily sold. The produce not sold was consumed by pigs and cows purchased for this purpose. Areas not suitable for crop raising were laid out in grass paddocks for agistment of cattle.[23] It was reported in 1890 that lucerne had grown "beyond expectation" and the effluent water, which was analysed by the Government Analyst every quarter, was purified satisfactorily.[24]

The flow to the farm increased rapidly each year to 3.25 million gallons per day by 1900. The population of the surrounding neighbourhoods also grew and in 1898 the Water Board together with the Public Works Department began some experiments with filters and tanks with the idea of changing to septic tank treatment of the sewage because of the complaints of smells from neighbouring localities and threats of legal action.[25] By 1900 William Hamlet, the Government Analyst, was proclaiming the Botany sewage farm as a dismal failure. The land was waterlogged and fouled, he said.[26] Complaints about the sewage farm were stepped up in the next few years.

In a later government report it was admitted that the sewage farm did give off "exceedingly disagreeable and offensive" odours although there was no evidence that these odours were unhealthy. The reason that the sewage farm was such a nuisance, the report claimed, was because of the unsuitability of the area and the fact that it was grossly overloaded. The soil was raw sand and therefore did not contain enough organisms for breaking down the sewage and the location was subject to tides so that the land was periodically saturated with salt water and sewage "to an extent that makes successful operation impossible". The planned rest times for the filter beds were not always practicable and the land had become "sewage sick" so that little profit could be obtained from growing vegetables on it.[27]

In 1905, swine fever caused the destruction of the farm's pigs and although pig raising had been profitable it was not resumed after this. By 1908 so much of the farm was continually flooded because of the greatly increased flow of sewage (6.75 million gallons daily) that the raising of crops had become a very small proportion of the farm's activities and a few years later crops were abandoned altogether.[28] From 1916 the sewage was piped to the coastline and into the sea and the sewage farm ceased to operate. In 1918 there was an attempt to lease out the old filter bed areas and it was found that the soil had already reverted to raw sand.[29]

CHEMICAL PRECIPITATION - A SHORT LIVED EXPERIMENT

By 1891, George Stayton was no longer in favour of sewage farming. On returning from a tour of British sewage treatment works he presented a report to parliament on methods of sewage purification. He claimed that intermittent downward filtration was not "making any particular advance in England".[30] He was particularly impressed, however, by three different systems of chemical precipitation.[31]

Chemical precipitation for the purposes of purifying sewage was used in Britain following the Public Health Act of 1875 which was aimed at protecting rivers which had become grossly polluted by the combination of water-carriage technology and discharge into the nearest watercourse. The Act insisted that sewage be treated before discharge. Sewage farming had been the preferred method but land was often scarce or unsuitable in British inland towns and cities. Chemical precipitation before land treatment reduced the amount of land required.[32]

The first chemical precipitant patented was lime. Between 1856 and 1876 it is estimated that over 400 patents were granted for chemical precipitants.[33] Little was understood about the science behind precipitants and a writer at the time observed,

Inventors seem mainly to have looked out for articles which were cheap, or entirely worthless, and heaped them together without any definite notion of the part which they were separately and collectively to play. This alone can count for the recommendation of such bodies as coal-ashes, soot, salt, gypsum, etc., which in almost every case would do more harm than good. Very often we see, especially in the older specifications, materials given as alternatives whose action, if any, must be evidently quite dissimilar the one to the other.[34]

Often the precipitants were unwanted by-products of industrial processes used with some other material.[35]

Many limited liability companies were formed to exploit the situation and make profits from patented precipitation processes. They promoted their processes using test results from experiments often undertaken by their own employees and literature giving a misleading interpretation of the results. By 1884 most had gone into liquidation and their treatment works had become the property of the local authorities.[36]

At first it was hoped that the expense of treating the sewage could be recouped from turning the precipitated sludge into a valuable fertiliser.[37] However it was generally recognised by opponents and proponents alike that chemical precipitation did not purify the sewage but merely clarified it and that the chemical precipitation had to be used in conjunction with some sort of filtering process.[38] Stayton proposed that a patented chemical precipitation system, known as the International system, be used for sewering Parramatta, just West of Sydney (now the demographic centre of Sydney). The International system had two stages. In the first stage the sewage was precipitated and deodorized in settling tanks with a magnetic precipitant and deodorant called "ferozone" (trade name for a preparation of salts of iron and alumina). In the second stage artificial filters were proposed rather than sand or earth. The partly purified sewage-effluent would pass through "polarite" filter beds (another trade name for a "specially prepared rustless and magnetic oxide of iron) which were supposed to trap the remaining solids and oxidise putrescible matter held in solution. The sludge could be mixed with refuse or pressed and dried and sold to farmers.[39]

On Stayton's advice the Parliamentary Standing Committee on Public Works dropped the idea of a sewage farm for Parramatta.[40] However, there was much debate over this controversial decision, particularly from sewage farm proponents, and engineers were divided over the relative merits of sewage farming and chemical precipitation with filtration through an artificial material.

As in previous debates over sewage disposal, neither side could agree on the efficacy, nuisance potential, fertilising potential or economics of each proposal. A key point of dispute was the suitability of the site for sewage farming. Stayton argued that the proposed site for the sewage farm was unsuitable because it was low-lying and consisted mainly of clay. He warned that the area would become surcharged and water-logged with sewage and give off offensive smells. He argued that the "International" system of precipitation and filtration that he advocated could be carried out close to populated areas without any smells or nuisance and would be more economical.[41]

The Commissioner and Engineer-in-Chief for Roads, Bridges and Sewers, Mr R.R.P.Hickson, who had originally proposed the sewage farm at Parramatta, disagreed with Stayton completely. It had been proposed to treat the sewage at Parramatta by a combination of broad irrigation and downward intermittent filtration on 42 acres of sand filling and 22 acres of friable clay "which although not capable of taking so much sewage [as sand] is considered by authorities to be even a better filtering medium".[42] The site, argued Hickson, was the best in the area because of its distance from population, its ability to deal with the drainage of nearby suburbs and its capability of expansion.[43] He claimed that intermittent-downward filtration was the best method of sewage purification to use.

With reference to the question of the relative advantages of chemical precipitation and land filtration, I can without hesitation say that at the present time no sanitary engineer of eminence in Europe or America will be found who will give unqualified preference to the former.[44]

Precipitation had been adopted, Hickson pointed out, in London and some towns in Britain because land for filtration was not available, was too expensive or was unsuitable. Chemical precipitants merely clarified the sewage and retarded the action of nitrifying organisms in any subsequent filtering process. The International System, Hickson pointed out, had only been around for five years and while over 400 patents had been taken out for various precipitating mediums, "the "survivals" could be counted on the fingers."[45] Almost all the available literature on the advantages of the system, he claimed, was published by the International company itself.[46] Stayton, on the other hand, argued that a recent Commission in Britain had determined that precipitation together with filtration gave "the best effluent known" and that this was a widely used method for towns in Britain.[47]

Complaints about the state of the Parramatta River continued and in 1898, the government ordered a referendum of rate-payers to be taken. 349 people voted in favour of the sewage farm scheme and 111 voted against it but the situation was not resolved and eventually, decades later, Parramatta's sewage was piped to the coast and discharged into the ocean.

Although chemical precipitation was never tried at Parramatta, it was experimented with for a very short time at North Sydney. Ocean disposal was too expensive and the disposal of raw sewage into the Harbour was no longer acceptable. Chemical precipitation was first proposed in 1882 by the Public Works Department and again in a report by Stayton four years later. It was proposed that the sewage be chemically treated and discharged into Middle Harbour. The place for the treatment was later named Folly Point.[48]

It was intended that the sewage would be screened before having lime and sulphate of iron mixed with it. It would spend some time in settling tanks where a sludge would be precipitated out and then the clear effluent would be intermittently filtered through 6 feet of sand, on land reclaimed from tidal waters, before being discharged into the bay.[49] The sludge would be made into sludge cake using filter presses and then burnt in furnaces since "it was deemed inadvisable to rely solely for any demand for the product as a means of disposal" and because burning was the most "efficacious" method of disposal.[50]

Work began on the North Sydney sewerage works in 1891 and they were duly handed over to the Water Board on their completion in 1899. But in their annual report the following year the Board claimed that there were not enough tanks "to meet the requirements of the rapid expansion of the sewerage system" and that additional works had been authorised.[51] The year after that the precipitation process was abandoned.

The Board's engineer claimed that after a few months it had been found that the cost of lime for precipitation, sludge pressing and fuel for burning the sludge was too great.[52] There had also been trouble with the sand filtering area which "had every appearance of becoming sour and sewage sick" and this required regular harrowing to keep it aerated.[53] In a later report, the Board also admitted that there had been a number of complaints of nuisances.[54]

A British Local Government survey in 1894 of 234 towns that had or were still using chemical treatment found that none had made a profit from manufacture of fertiliser, 30 had made some income but 204 had made no income. 174 were still using chemicals.[55] When it was realised that fertiliser manufacture was not profitable the disposal of the precipitated sludge became the biggest problem facing those using chemical treatment.[56]

SERIOUS EXPERIMENTS WITH SEPTIC TANKS

As the precipitated sludge came to be considered to be an expensive nuisance rather than an asset, engineers searched for a means of treating the sewage which would not produce sludge.

It has been felt for some time that any means of treating sewage without the production of sludge, would be hailed by sanitary engineers as a great advance on present methods.[57]

Septic tank treatment was attractive because it held the promise of eliminating the sludge which was proving to be a nuisance with chemical precipitation. It was essentially a horizontal-flow primary sedimentation tank providing a very long retention period. Sewage entered and left the tank below the surface so that anaerobic microbes could operate. The sludge, which at first was not believed to accumulate, was not removed very often and never entirely removed so that there were always microbes present.[58]

Anaerobic tanks had been used as far back as 1860 but it was not until 1881 that it was found in France that organic solids liquified under such conditions and this was attributed to the anaerobic action taking place.[59] By the end of the century septic tanks were being hailed as the answer to the sludge problem and an automatic process with no accompanying nuisance and no need for expensive chemicals.[60] Although septic tanks were said to eliminate the sludge problem, at least one engineering writer has wondered in retrospect about the extent to which scientific judgement was influenced by wishful thinking.[61]

Septic tanks replaced precipitation tanks in many places but it was soon realised that they were not the panacea that had been hoped for. The reduction in sludge volume was mainly caused by consolidation in the septic tank and loss of solids with the effluent. Not only that but septic tanks were found to be smelly and the effluent, which was more unpleasant than from other tank processes, would often clog filters because of the high solids content.[62]

Septic tanks, whilst at first as popular in the U.S. as in Britain, lost favour because of patent disputes arising from the original British patent of the process. Also many tanks were built as septic tanks by people who did not understand the scientific principles involved, and their subsequent failure gave septic tanks a bad name.[63]

When chemical precipitation was found to be unsuitable at North Sydney it was decided to convert one of the precipitation tanks into a septic tank.[64] That same year, J Davis, the Engineer-in-Chief for Sewerage Construction, Public Works Department also proposed some of the suburbs in southern Sydney be treated by septic tanks and filters.[65] A Water Board engineer claimed that the results of experiments carried out on the sewage farm showed that the septic tank system lived up to all expectations and claims that had been made for it.[66] Added advantages were that the tanks tended to equalise an irregular flow of sewage and screening could be avoided.

The precipitation tanks at North Sydney were all converted to open septic tanks in 1902 with the effluent from them still going onto the sand filter beds. The Board engineer claimed an excellent resulting effluent, no smells and a considerable cost saving. Septic tanks were also established elsewhere in Sydney. The Government analyst urged in that year's Water Board report that the success of the experiments with septic tanks and cultivation beds justified the whole of Sydney's sewage being treated in this way.[67] Septic tanks were also given a vote of confidence by the President of the Royal Society of N.S.W., an engineer himself, in 1903 when he claimed that septic tanks had been recognised in England as being "an essential part of modern bacterial purification processes".[68]

Along with the praise, however, there were a number of complaints about the smells arising from the North Sydney tanks. The newspapers had been reporting complaints about the works from nearby residents and from boating people. The local council had made representations to the Water Board in 1903 without success and the Mayor had declared conditions at Folly Point to be unsatisfactory.[69] At a public hearing in 1905 witnesses described what they saw at Folly Point as "an abominable nuisance" and reported that many of the ladies on the wharf at the time were made sick by it.[70] By 1912, the sand filters at Folly Point were overloaded and "sewage sick" and had to be relieved with the addition of artificial filters and detritus tanks.[71] The nuisance continued at Folly Point until it was decided to divert the sewage from there to the sea.

Artificial filters, using natural and patented materials, were experimented with in various parts of Britain during the 1880s, however the incentive to research along these lines was blunted when land treatment became a necessary condition imposed by the Local Government Board for any sewage disposal loan to local authorities.[72] The real breakthrough in artificial filters came in the United States where the first trickling filters were introduced. These enabled the sewage to trickle slowly through gravel filters, forming a thin film over the surfaces of the stones. The thin film, in contact with the air facilitated decomposition of the sewage by aerobic micro-organisms.[73]

The British were very interested in the U.S. experiments because these filters required much less land than conventional land treatment. As artificial filters were further developed the local authorities, keen to install them in place of land treatment, came into conflict with the Local Government Board which was still insisting on land treatment. In the face of mounting disputes, a Royal Commission was appointed in 1898 to "inquire and report what methods of treating and disposing of sewage may properly be adopted."[74]

Artificial filters put an end to any pretences that the sewage was being utilised as it was filtered and septic tanks heralded the end of efforts to utilise the sludge as manure. The development of septic tanks offered even more progress in this quest for processes that required less and less space. The ocean disposal of raw sewage was a solution which required no land. By 1920 almost all of Sydney's sewage was being piped to the coastline and dumped into the ocean at three main outfalls; Bondi, Malabar and North Head.

TRENDS IN SEWERAGE TREATMENT

In the nineteenth century researchers had aimed for an ideal treatment solution that would completely, or almost completely, purify the effluent leaving no awkward by-products and no smell. The existence and discovery of new treatment methods did not end the research or settle disputes since there was always a better treatment to strive for and no agreement could be reached about the efficacy of new treatment methods. The major factors in the formation of a paradigm for sewage treatment methods were 1) the domination of the field by engineers, 2) the discarding of the search for an ideal solution by engineers and 3) the attainment of consensus amongst engineers about which treatment technologies were adequate.

The domination of decision-making by engineers

Joel Tarr has written about the formation of the profession of sanitary engineering in the United States and his description is apt for the Australian situation as well.

The development of a new technology with a set of unique characteristics requiring a special body of knowledge and techniques inevitably produces a community of practitioners. This community, or a more specialized subset of the community, may in time attempt to create a profession--a group of people who profess to hold a body of specialized knowledge that enables them to treat a certain class of problems and phenomena.[75]

The development of sewage treatment methods in the late nineteenth century was occurring at a time when the profession of sewerage engineering was emerging. The emergence of professional interests was accompanied by professional preferences in sewage treatment technologies which gradually overcame the differences between engineers. The steady trend away from sewage utilisation suited this newly forming profession. Although the land pressures in Sydney in the nineteenth century were less marked than in Britain or the United States and Sydney did not suffer from having a combined system of sewage and stormwater drainage, which was a serious impediment to sewage utilisation,[76] Sydney engineers were took on the professional preferences of engineers abroad. Sewage treatment research was characterised by a search for less land intensive solutions. (see figure 2)The ocean disposal of raw sewage was a solution which required no land and offered no sewage utilisation; it was the ideal solution.

Figure 2

The engineering text books of the nineteenth century are mostly unanimous in the opinion that ocean disposal was the most preferable method of dealing with sewage. For example Baldwin Latham, a well-known author of the engineering text "Sanitary Engineering", argued that experience showed that the fertilising components of the sewage could not be extracted profitably and therefore it should not be considered a great waste to put the sewage into the sea.[77] In fact, in the US at this time consulting engineers were advising urban policy makers to dump raw sewage into streams because the self-purifying nature of running water provided adequate treatment.[78]

The push to utilise sewage motivated many advocates of sewage farming, both broad irrigation and downward intermittent irrigation, and later chemical precipitation. However, engineers who wrote at the end of the nineteenth century took a different perspective to the public and many other professional groups. Engineers were not necessarily against the use of sewage farms but they considered them primarily in terms of their cost effectiveness and efficiency at purifying the sewage; the waste or utilisation of manure was quite secondary. "Intermittent downward filtration" in particular was viewed simply as a cheap means of dealing with the sewage and the land was simply a medium for purification.[79]

For example, Henry Robinson, an English Professor of Civil Engineering, claimed that sewage farms were too often considered merely from an agricultural point of view rather than from a sanitary point of view.[80]

The reason why sewage farming has been so unduly pressed and advocated is, that in the early days of sewage utilisation, those who directed public opinion on the question came to the conclusion that the full chemical value of sewage could be realised by its application to land.[81]

Australian engineers also viewed sewage farming merely as one method of purifying sewage effluent rather than as a means of utilising the fertilising powers of the sewage. Benefits that came from enriching the land were merely part of the economics of the operation. W.H.Warren, Professor of Civil and Mechanical Engineering at Sydney University, like many of his contemporaries, considered that sewage farming was an appropriate option for sewage disposal when it was cheaper than disposal to sea.[82]

Chemical precipitation was another step in a process which aimed at minimising the land required for treatment rather than maximising the land which would benefit from the fertiliser. Chemical precipitation still required that the sewage be subject to downward intermittent filtration, but a smaller area was required once the sewage had much of its suspended solids filtered out. Research into artificial filters in the 1880's offered hopes that the land area required would be reduced even further by the use of materials that had a high surface area to weight ratio.[83]

Engineers were increasingly less supportive of sewage farming because it was an area less closely aligned to their traditional skills and there were pressures from other professional groups to take control of the area, especially once the biological mechanisms of the sewage farm became better understood.

In 1894 the President of the Royal Society, T.P.Anderson Stuart, M.D. who was Professor of Physiology at Sydney University explained to a meeting of fellow scientists how theories of decomposition had changed. It had previously been thought that decomposition was principally a chemical process mainly due to direct oxidation. It had been discovered, however, that organisms in the soil converted the nitrogenous components of dead organic matter into nitrites and nitrates which were harmless and dissolved in water or were taken up by the roots of plants. These "nitrifying organisms" were essential to the supply of food to plants.[84]

It was because of this discovery that Anderson Stuart believed that sewage farming was the most natural and efficient mode of disposing of sewage where sufficient areas of proper soil were available. [85] He felt this discovery of nitrifying organisms and their action in decomposing organic matter removed the work of disposing of sewage away from the sewerage engineer to the biologist.

now one may say that it is the business of the engineer to collect and distribute the sewage, but that it is mainly that of the biologist or of the chemist to say how it should be disposed or destroyed.[86]

Similar arguments were made with respect to chemical precipitation and septic tank treatment. Hamlet, the government analyst, believed that

Methods of removal are mechanical, and belong to the domain of the engineer; methods of disposal are of another order, and belong to the domain of biology and chemistry...[87]

The "naturalness" of a sewage farm, which appealed to some sections of the public, was not a desirable attribute to engineers who sought to harness and control nature with their technologies and thereby make their bid for expertise. This was why septic tank treatment and artificial filters appealed to engineers much more than sewage farming as a modern and scientific operation which was really "the natural method of sewage purification subject to control".[88] Sewage farms seemed to be too unpredictable.

Discarding the search for an ideal treatment

The Royal Commission into Sewage Disposal 1898-1915 played a vital role in the setting of universal sewage treatment standards that enabled engineers to agree over which sewage treatment methods were good enough. It marked the transition between two distinctly different phases of the development of sewage treatment engineering. One engineering writer, commented,

in a sense the Royal Commission marked the transition from folklore to a scientific approach to sewage treatment practices and requirements and heralded the opening of an era of rapidly developing and increasingly sophisticated technology.[89]

Although earlier sewage treatment methods were actually based in science and engineering rather than folklore, it is the perception of scientific maturity in the field that is significant here and this can be compared with Kuhn's description of the transition from a developing science to one that is governed by a paradigm. The incommensurable goals of sewerage experts were swept aside.

The origins of the modern concept of primary and secondary treatment arose from the division of treatment methods considered by the Commission into two stages. A number of the witnesses at the Commission hearings proposed two stage treatment for the sewage. The first stage would be to remove some of the sewage solids from the effluent and the second would be the biological decomposition of organic matter in the effluent. The Commission reported on these methods in their fifth report under the heading of "Preliminary Processes" and they stated,

The evidence which we have received and our own experience show that it is generally more economical to remove from the sewage, by a preliminary process, a considerable proportion of the grit and suspended matter, before attempting to oxidize the organic matters on land or in filters.[90]

The Commissioners considered detritus tanks, plain sedimentation tanks, septic tanks and chemical precipitation as preliminary processes and biological filters, contact bed systems or land treatment as secondary processes. The Commissioners found that chemical precipitation, sedimentation and septic tanks were all suitable forms of preliminary treatment. In comparing the cost of each preliminary process the Commission found that chemical precipitation was twice as expensive as septic tanks and plain sedimentation tanks but that this difference disappeared when the cost of filtering the resulting effluent was also considered. This was because chemical precipitation tanks were more effective at removing suspended and colloidal matter and the effluent from such tanks could be treated on a filter of finer material and therefore smaller size and so the filtering operation was less expensive.[91]

Since each process, when considered in conjunction with filtering costs, had very similar annual operating costs, the Commission recommended that the choice between them be made on the basis of the means at hand for disposal of sludge, on the class of filter to be used and on the strength and character of the sewage. For example strong sewage would give less nuisance if treated by chemical precipitation and weak sewage might be more economically treated by septic tanks.[92]

The relative merits of the second stage treatments were also considered. The rivalry was not only between artificial or biological filters and land treatment but also between various types of biological filters and contact beds. The Commission found it extremely difficult to adjudicate. In the end, rather than recommending one method over another in absolute terms, they recognised that each had its place depending on circumstances: a biological filter could treat nearly twice as much sewage as a contact bed made from the same amount of material; that biological filters were better suited to variable flows and their effluents more aerated; but biological filters were more likely to create a nuisance from flies and from smells.[93]

Although the Commission declared no winners, they presented the rules of the game by recommending minimum quality standards for discharge of sewage into rivers and streams. These standards, commonly referred to as the 20:30 standard (Biological Oxygen Demand not more than 20mg/l and suspended solids not more than 30 mg/l), were not only accepted in Britain at the time but they are still used in many countries today.[94]

Reaching a consensus

The Commission's real achievement was in paving the way for some form of consensus amongst the engineering community. They did not do this by imposing their judgement on the engineering community. What they did was to recommend standards of effluent that should be achieved by whatever process was chosen. In so doing they made the competition between processes on the basis of technical superiority irrelevant. What use was it to achieve a higher degree of purity than was necessary?

The philosophy behind this consensus was that treatment should not be optimal but rather 'good enough'. The usage of the term 'sewage purification' was gradually replaced, partly because it was said to be misleading to "laymen" who supposed that once purified the sewage became pure "whereas the sanitary engineer may mean only that it is purer than it was before."[95] The skill of the engineer now lay, not in achieving a high quality effluent but rather in achieving an adequate quality of effluent for as little money as possible and letting nature do as much of the work as possible.[96]

Of the three main processes considered by the Royal Commission as a preliminary treatment, it was plain sedimentation that came to be the standard treatment used. Sedimentation tanks were simply tanks in which the sewage was left for a period of time during which some of the solids settled out. Plain sedimentation had been used with the early sewers in the nineteenth century to reduce the nuisance caused from sewage going into streams, but because the sludge was sometimes not removed allowing it to build up and occupy most of the space in the tanks, it was not considered a satisfactory method and was seldom seriously considered before the Royal Commission.[97] It was considered to be "a process midway between chemical precipitation and septic tank treatment, but having the advantages of neither"[98]

The claimed advantages of chemical precipitation and septic tank treatment had been exaggerated and although they were as efficient, and in the case of chemical precipitation, more efficient than plain sedimentation at removing solids the game had changed and efficacy was no longer the primary concern.

Chemical treatment had promised large profits from the manufacture of fertiliser out of the precipitated sludge and it had been thought that this treatment would be sufficient on its own to produce an effluent free from nuisance that could be put into a stream. Instead it was found that the sludge was a nuisance, the chemicals costly and the fertiliser could not compete with artificial fertilisers. Even though the Commission gave chemical treatment a good write up, it fell into disfavour except in temporary or exceptional circumstances, for example when there was a high proportion of industrial waste in the sewage (for example an acidic trade waste might cause an acidic sewage which needed to be neutralised).[99]

Likewise septic tanks had promised to eliminate the sludge problem but failed to do this. Additionally they tended to be smelly. When separate sludge digestion was developed and biological filters took over from contact beds, septic tanks ceased to be installed for sewage-treatment works. They are still, however, used for individual and small groups of houses that are too isolated to be connected to a public sewerage system.[100]

Plain sedimentation won out for municipal sewerage works because it was good enough, not because it was technically superior, achieved a better effluent or even because it was considered a satisfactory treatment on its own, that is without a second stage of treatment. Sedimentation therefore experienced a revival. Sedimentation was simpler, more easily controlled and cheaper if you didn't count the costs of the second stage treatment. In many places, particularly at ocean outfalls, one stage processes were installed and sedimentation was definitely cheapest if that was all you were installing. Moreover, even where two stages were planned, the first stage was often built some time in advance and the tendency was to go for the cheapest solution with respect to short-term costs.

Similarly sewage farms did not fall into disfavour because they were ineffective or less effective than artificial filters or tank treatments. Rather it was because they were land intensive and had often been poorly managed and overloaded, giving rise to nuisances. Moreover the goal of utilising the sewage as fertiliser was not an aim of engineers, no matter how popular it was in the community, and was unlikely to be profitable. As soon as the Royal Commission gave official approval to artificial methods of secondary treatment British engineers and others in the Commonwealth were able to follow the example of US engineers and leave sewage farming behind. Shortly after the Commission ended the activated sludge process of sewage treatment, a way of using aerobic micro-organisms to break down sewage in tanks, was developed. This together with trickling filters became the staple methods used by engineers for secondary treatment.

CONCLUSION

The difference between debate over sewage treatment methods in the nineteenth century and in the twentieth century until recent years can be accounted for by the the establishment of a profession and the formation of a paradigm which occurred during the end of the 19th and beginning of the 20th Century. These developments were interlinked. The establishment of the profession of sewerage or public health engineering allowed the domination of the debate by a group of people with common goals and approaches and facilitated the formation of the consensus that was necessary for a paradigm to be formed.

In Britain and the British Commonwealth, the Royal Commission into Sewage Disposal played a vital role in achieving that consensus by setting standards which allowed treatment methods to be evaluated and the search for ever better treatment methods to be abandoned. The paradigm, in turn, strengthened the profession, giving it a set of treatment methods to choose from and allowing it to focus on improving those treatments, which were agreed to be appropriate.

The sewerage treatment paradigm has been continued through the ongoing training of new recruits to the profession, the protection of the profession's autonomy and the exclusion of outside interference in decision-making and the physical existence of millions of dollars of capital works that are a testament to that paradigm.

This paradigm has served the public health engineering profession well for decades but the profession is now facing a period of turmoil as debates rage over the appropriateness of the treatment methods available within the paradigm. Alternative treatments that do not fit easily into the primary, secondary, tertiary trichotomy are emergimg to meet new needs. Whether a technological revolution will emerge that will see a new paradigm put in place has yet to be seen.

Endnotes

1. Sydney City and Suburban Sewage and Health Board, Twelfth and Final Report, 1877, p. 3.

2. Sewage and Health Board, op.cit., pp. 143-6.

3. ibid., pp. 146.

4. Sewage and Health Board, op.cit., pp. 134-5.

5. Evening News, 23rd March 1880.

6. Sewage and Health Board, op.cit., pp. 131-2.

7. Sydney Morning Herald, 17th March 1880.

8. Evening News, 27th March 1880.

9. Ulick Ralph Burke, A Handbook on Sewage Utilization, 2nd ed, E. & F.N.Spon, London, 1873, p. ix.

10. ibid., p. x.

11. Joel Tarr, 'From City to Farm:Urban Wastes and the American Farmer', Agricultural History XLIV(4), October 1975, pp598-612.

12. Sewage and Health Board, op.cit., pp. 134-5.

13. W. Clarke, Report to the Government of New South Wales, on the Drainage of the City of Sydney and Suburbs, 1877, p. 13.

14. A. Mault, `The Sewerage of a Seaside Town', Australasian Association for the Advancement of Science 4, 1892, pp. 772- 3.

15. Ulick Ralph Burke, op.cit., p. xv.

16. ibid., p. xi.

17. ibid., p. xi.

18. Sydney City and Suburban Sewage and Health Board, No.10 Committee, Second Report, 21st October, 1875.

19. Parliamentary Standing Committee on Public Works, Drainage Works, North Shore, 1888, p. 6.

20. George Stayton, Report on a System of Sewerage for the Western Suburbs of the City of Sydney, 1887.

21. George Stayton, Sewerage and Drainage of the Western Suburbs, Department of Public Works, 1887, p. 22.

22. F.J.J. Henry, The Water Supply and Sewerage of Sydney, Halstead Press, Sydney, 1939, pp. 171-2

23. ibid.

24. J.M.Smail and W.L.de L.Roberts, `Purification of Sewage', Australasian Association for the Advancement of Science 2, 1890, p. 684.

25. Henry, op.cit., pp. 173-4.

26. William Hamlet, `Anniversary Address', Royal Society of NSW 34, 1900, p. 22.

27. Parliamentary Standing Committee on Public Works, Disposal of Sewage from the Western, Southern, Illawarra, and Botany Districts, 1908, pp. 7-8.

28. Henry, op.cit., pp. 173-4.

29. ibid.

30. George Stayton, Sewage Purification, NSW Legislative Assembly, 1891, p. 14.

31. ibid., p. 1.

32. John Sidwick, `A Brief History of Sewage Treatment-1', Effluent and Water Treatment Journal, February 1976, p. 68.

33. Stanbridge, History of Sewage Treatment in Britain, Part 3, Institute of Water Pollution Control, Kent, 1976, p. 8.

34. J.W.Slater, quoted by Stanbridge, op.cit., p. 9.

35. Stanbridge, op.cit., p. 9.

36. ibid., p. 12.

37. Sewage and Health Board, op.cit., p. 9.

38. J.M.Smail & W.L.de L.Roberts, 'Purification of Sewage', Australasian Association for the Advancement of Science II, 1890, p. 682.

39. Stayton, op.cit., pp. 4-5.

40. Parliamentary Standing Committee on Public Works, Sewerage Works for Parramatta, 1892, p. 5.

41. ibid., p. 8.

42. R.R.P. Hickson, Parramatta Sewerage Scheme, 1892, p. 6.

43. ibid., p. 4.

44. ibid, p. 1.

45. ibid., pp. 1-4.

46. Ibid., p. 3.

47. Parliamentary Standing Committee on Public Works, Drainage Works, North Shore, 1888, Minutes of Evidence, p. 5.

48. Ibid.

49. ibid.

50. J. Davis, `The North Sydney and Double Bay Sewerage Schemes', Journal of Royal Society of NSW 33, 1899, p. xx.

51. M.W.S.&D.B., Annual Report, 1900, pp. 4, 86.

52. Ibid.

53. M.W.S.&D.B., Annual Report, 1900, p. 86.

54. M.W.S.&D.B., Annual Report, 1903, p. 21.

55. Stanbridge, op.cit., p. 19.

56. John Sidwick, op.cit., p. 70.

57. Henry Deane, `President's Address', Journal of Royal Society of NSW 32, 1898, p. 17.

58. H.H.Stanbridge, History of Sewage Treatment in Britain, Part 4, Kent, 1976, p. 42.

59. Ibid.

60. Deane, op.cit., pp. 17-8; William Hamlet, `Anniversary Address', Journal of Royal Society of NSW 34, 1900, p. 27.

61. John Sidwick, op.cit., p. 295.

62. Ibid., p. 296.

63. Leonard Metcalf & Harrison Eddy, American Sewerage Practice, vol. III, 1st ed., McGraw-Hill, New York, 1915, p. 17.

64. M.W.S.&D.B., Annual Report, 1903, p. 21.

65. J.Davis, Report on Proposed Scheme of Sewerage for the Illawarra Suburbs, 1900.

66. M.W.S.&D.B., Annual Report, 1901, p. 71.

67. Ibid., p. 73.

68. W.H.Warren, `Presidential Address', Journal of Royal Society of NSW 37, 1903, p. 47.

69. Daily Telegraph, 6th August 1903.

70. ibid., pp. 10,12.

71. W.V. Aird, The Water Supply, Sewerage and Drainage of Sydney, M.W.S.&D.B., Sydney, 1961, pp. 154-5.

72. Sidwick, op.cit., p. 69.

73. Stanbridge, op.cit., part 6, pp. 23-5.

74. Sidwick, op.cit., p. 71.

75. Tarr et al, 'Water and Wastes: A Retrospective Assessment of Wastewater Technology in the United States, 1800-1932', Technology and Culture, April 1984, p. 246.

76. Ibid., p. 242.

77. Baldwin Latham, Sanitary Engineering: A Guide to the Construction of Works of Sewerage and Drainage with Tables, 2nd ed, E.&F.N.Spon, London, 1878, p. 444.

78. Joel Tarr et al, op.cit., pp. 238-39.

79. ibid., pp. 133-4.

80. Henry Robinson, Sewerage and Sewage Disposal, E.&F.N.Spon, London, 1896, p. 48.

81. ibid., pp. 48-9.

82. W.H.Warren, `President's Address', Australasian Association for Advancement of Science 4, 1892, p. 165.

83. Stanbridge, op.cit., Part 6, pp. 25-37.

84. T.P.Anderson Stuart, `Anniversary Address', Royal Society of NSW 28, 1894, pp. 16-17.

85. Ibid., pp. 18-19.

86. Ibid., p. 18.

87. Hamlet, op.cit., p. 22.

88. Ibid., p. 33.

89. Ibid., p. 199.

90. Royal Commission on Sewage Disposal, Methods of Treating and Disposing of Sewage, Fifth Report, London, 1908, p. 18.

91. Ibid., pp. 41-3.

92. Ibid., pp. 43-6.

93. Ibid., p. 119.

94. Ibid., p. 199

95. Leonard Metcalf & Harrison Eddy, American Sewerage Practice, vol III, 1st ed, McGraw-Hill, New York, 1915, p. 197.

96. Ibid., p. 197.

97. Ibid., p. 5.

98. Sidwick, 'A Brief History of Sewage Treatment-2', Effluent and Water Treatment Journal, 1976, p. 195.

99. Stanbridge, op..cit., Part 3, p. 20.

100. Stanbridge, op.cit., Part 4, p. 44.