Auswirkungen optimierter Straßenabläufe auf Feststoffeinträge in Kanalisationen

• Effects of optimised road gullies on the entry of solids into the sewer system

Stein, Robert; Dohmann, Max (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2008)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2008

Abstract

In wastewater disposal the unsolved organic and mineral substances that are contained in the wastewater play a decisive role. In all surveys these solids have not been given sufficient attention, although they significantly influence the operation and service life of drainage systems by forming deposits. In the future, these effects are likely to intensify due to the turning away from the common practice of draining all stromwater flows that occur on settlement and traffic areas quickly and to the greatest possible extent. The measures taken to decentrally retain or seep stormwater namely have more or less strong influence on the drainage and self-cleaning capacity of a sewer system and thus on the formation of deposits. Furthermore, mineral solids in the wastewater deserve special attention when looking at water pollution caused by organic micro elements as many of these micro pollutants preferably accumulate on solid particles and thus enter bodies of water via discharges from sewer systens. In the face of the importance of mineral solids, special efforts to prevent their entry into drainage systems appear necessary. Based on an analysis of the solids' origin, composition and quantity contained in the wastewater road gullies offer the greatest potential to retain solids. As results of the performed laboratory and in-situ tests as well as a weak point analysis have shown, road gullies that are standardised in DIN 4052 and have been used so far fulfill their function of retaining solids only to a very insufficient level. Here, their productivity is heavily influenced by the practiced cleaning intervals. In order to optimise the retention of solids, the separative road gully (SSA), which is presented in the survey at hand, was developed. It is based on the concept of mechanically separating the solids that are contained in the road gully from the liquid phase. A special system ensures that this is carried out in the most concentrated way and in three steps. In addition, it prevents retained solids from being mobilised irrespenctive of the duration and intensity of precipitation events. The tests and optimisation of the constructive and hydraulic approaches as well as the verification of the functionality and efficiency of the SSA were performed within the scope of laboratory test and in-situ tests over several years. Here, as a comparison conventional road gullies were also taken into account. Improvements in the retention of solids by the SSA arose without utilising its capacities under test conditions. Compared to road gullies that comprise a sediment chamber the performance increased by around 32% and compared to road gullies with floor outlet even up to 81%. In this way for the SSA the verification of suitability could be provided as a decentral measure to reduce solid entry into sewer systems. An area-wide conversion of conventional road gullies to the SSA also appears economically interesting in the medium term as the cleaning costs for sewer systems could be significantly reduced.