Treatment Technologies:

Outdated or rare

Paradigm

Following the Commission, sewerage engineers gradually came to favour sedimentation as a primary treatment method for municipal plants. It had not been a preferred method before the Commission but after it was officially found to be as good as chemical precipitation and septic tank treatment it gained favour. The use of primary treatment on its own, gave sedimentation a cost advantage over chemical precipitation and the tendency to implement treatment in stages as money came available or as the need arose ensured that the cheapest first stage was chosen. Moreover the cost of chemicals for precipitation was an increasing one over time (Sidwick, 1976a, p195).

Septic tank treatment went out of favour for plants of any size, partly because of the smell which accompanied them. They had a very bad reputation with the public and it was found difficult to site them. Although engineers had vehemently denied that septic tanks caused odour nuisances in the vicinity, the Commissioners found that all sewage treatment works were liable to smell at times and that septic tank treatment was likely to be more offensive than the others.(Royal Commission, 1908, pp44-5)

The use of 'artificial' filters came to prevail over the use of the land as a filtration medium in which the aerobic microorganism could oxidise and nitrify the sewage effluent. The pressure to replace land treatment had come from towns and cities where suitable land for this purpose was scarce or expensive and the Royal Commission on sewage disposal had in fact been established to settle a dispute between local authorities who wanted to use artificial filters and the Local Government Board which believed that only land treatment was satisfactory (Sidwick, 1976b, p71). The declaration by the Commission that artificial filters were adequate was enough to spell the end for land treatment even though the Commissioners tended to prefer land treatment.