Wherever people live there is sewage. The advanced civilisations in the Middle East and China already acknowledged the problem of waste water treatment and built drainage systems in order to lead dirty water out of their cities. The construction of the vast sewerage network in ancient Rome with its central element, the cloaca maxima, was state of the art in the fifth century BC and the peak of sewage treatment in antiquity. With the decline of the Roman Empire, however, this knowledge was lost. In the Middle Ages, cities literally drowned in human waste. The common practice of simply disposing of household refuse in the streets repeatedly caused raging epidemics. The Industrial Revolution in the 19th century exacerbated the waste water problem – not only because the rapidly growing towns produced previously unheard-of quantities of waste water but also because, for the first time in human history, this sewage contained large amounts of toxic residue from industrial processes. In the metropolitan area of the Ruhr region, for instance, these pressing problems led to the foundation of the Ruhrverband in 1913.
In England, the powerhouse of industrialisation, the Rivers Pollution Prevention Act was passed as early as 1876 as the first cohesive body of laws on sewage treatment. Preference was initially given to natural irrigation techniques which were later developed into artificial biological processes. Irrigation was also seen as a convenient method of fertilisation. Consciously utilising the self-purifying capacity of water was also considered a natural cleaning process. In North America, discharging sewage into a body of water was called "cleaning by dilution".
Around the turn of the last century, mechanical sewage treatment was developed. It was widely implemented in Germany, the main target being to aesthetically clean the sewage before discharging it into a body of water. Mechanical methods include screens which remove large pollutants from the water much like a sieve or a rake.
Another mechanical process is the use of grit chambers in order to catch the mineral matter carried especially by rain. The first grit chambers were simple rectangular or round dips, usually with a steep bed slope to facilitate the removal of settleable solids (which was done manually using various receptacles and later with travelling cranes or grab dredgers). The longitudinal grit chamber in Essen is a continuation of the first tank systems. The settling of solids is achieved by widening the cross-section of the settling channel, thereby reducing flow velocity. The deep grit chamber with a vertical flow was developed in the 1930s. Due to the poor retention characteristics of fine sand, deep grit chambers are no longer in use today. The aerated grit chamber which was developed between around 1950 and 1960 is a fairly recent development.