Divided Treatment into two stages
Gave approval to a range of treatment technologies
Set standards and tests
Enabled concensus in the engineering community

---

The importance of the British Royal Commission into Sewage Disposal (1898-1915) to the maturity of sewerage engineering has been noted by engineers in the field,

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. (Sidwick, 1976a, p199)

Divided Treatment into two stages—Primary and Secondary

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, both necessary. The first stage was to remove some of the sewage solids from the effluent and the second was the biological decomposition of organic matter in the effluent.

When the British Royal Commission sat at the turn of the century they considered sewage treatment (other than land treatment) in terms of `preliminary' treatment followed by some form of filtration. The use of the term `preliminary' was intended to indicate that `preliminary' treatment was not a full treatment on its own and was not considered as such during the Commission's sitting.

However subsequently the sewage treatement paradigm became based on stages which were optional.

...back to top

Gave approval to a range of treatment technologies

The Royal Commission considered chemical precipitation, plain sedimentation and septic tanks as the main forms of preliminary treatment and found all performed satisfactorily when used in conjunction with filters, and that the operating cost difference between them was minimal when the filters used were appropriate to them. For example, sedimentation treatment was cheaper than chemical treatment but because it removed less of the suspended solids required more expensive filtration (1908, pp18-46).

...back to top

Set standards and tests

The British Royal Commission into Sewage Disposal was a key event for sewerage engineering because it set effluent standards to be achieved by sewage treatment processes.

Although the Commission declared no winners, it 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.

...back to top

Enabled concensus in the engineering community

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 none were perfect and no agreement could be reached about the efficacy of new treatment methods. Three trends in sewage treatment methods were evident:

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 British Royal Commission into Sewage Disposal 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." 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.

...back to top

---

References:

Royal Commission on Sewage Disposal (1908), ÔMethods of Treating and Disposing of Sewage, Fifth ReportÕ, (London: Royal Commission on Sewage Disposal)

Sidwick, John (1976a) ÔA Brief History of Sewage Treatment-2Õ, Effluent and Water Treatment Journal, April.