Early history times: 4000 BC - 450 AC
Three common factors can be identified in the early historical times: i) the need for proper disposal of human wastes was not fully understood, but there was recognition of some of the benefits (fewer odours for example) of taking these wastes away from the home; ii) the sewer systems were built to convey rainwater but ended up in combined sewerage systems; and iii) even though the sewers were successful in their function they were constructed in a trial and error process and therefore it was not the ideal sewer-design strategy. Sewers have been known for centuries, as early as 4500 BC in Babylon clay was moulded into pipes and used to convey run-off wastewater. In ancient Roman Empire, settled communities used open canals to transport excess of rainfall run-off out of the settlements in order to avoid nuisance and damage to properties. Later on, those canals were also used to convey wastewater from the public baths and latrines and were covert to avoid bad odours. Thus, eventually was created the first sewer system called “Cloaca Maxima” (510 BC) that was used to convey wastewater from the city of Rome to the Tiber River (Burian, et al. 1999).
The sanitary dark ages: 450 - 1750
For the most part, the construction of sewer systems up to the 1700s lacked proper engineering design and was conducted in piecemeal fashion. In addition to the inadequate design and construction practices, maintenance and proper operation of the systems were virtually neglected. In summary, many of the sewer systems of European urban areas during the 1600s and 1700s were grossly under-planned, poorly constructed, and inadequately maintained by the today’s standards, resulting in poorly functioning systems with repeated blockages and frequent nuisance conditions (Burian, et al. 1999).
The age of sanitary enlightenment: 1750 – 1800s
Although research uncovered the connection between polluted waters and disease, wastewater treatment was not widely practiced. The debate centred on whether it was more economical to treat the wastewater prior to discharge or treat the water source before distribution as potable water. Most of the cities used the dilution theory ignoring impacts to the recreational and the habitat of the receiving water. Formula methods were generally used (Roe, McMath, Adams), in spite of the fact that the results given by them lack consistency and are very erratic and unreliable. Even though the rational method was already introduced, the lag time in technology transfer limited its use and the design and construction of sewerage systems ended up in a poor functioning of the sewer systems.
The age of environmental awareness and technical development: 1900s – 2000s
The development of the discipline has provided new knowledge, and new tools available for sustainable urban water management. Computational aids, like integrated models advanced during the last decade, have improved the planning, design, operation and control of urban drainage systems significantly. However, the integrated approach has not found wider application in practice. Some of the reasons are the slow transfer of new techniques to the practitioners, the highly uncertainty in the predictions and the lack of knowledge that still exists in some of the components e.g. the ecological effects of urban drainage caused by chemicals used in the society. It is also noticed that real time control has not found wider application (Harremoes 2002).