The efficacy of streetsweeping in ultra urban environments

By: Katie Webb

Streetsweeping is an effective method for reducing suspended solids and related pollutant runoff from streets in ultra-urban areas. Studies show that using road sweepers designed with new technologies can reduce annual total suspended solids and related pollutants by up to 80 percent. Since ultra-urban environments don't have the space available to institute structural controls, streetsweeping is imperative, particularly in commercial areas, industrial areas and highly developed areas near receiving bodies of water. On highways, road sweepers can be used to effectively clean road shoulders, rest stops and maintenance yards. The greatest benefits are realized when the most technologically advanced sweepers are used on a weekly or bimonthly basis.

There are five main types of road sweepers, including mechanical sweepers, vacuum-assisted sweepers, tandem sweeping operations, regenerative air sweepers and vacuum-assisted dry sweepers. The overall effectiveness of a streetsweeping program depends on which type of road sweeper is used, along with a few other factors. Vacuum-assisted and regenerative air sweepers, for instance, are better at removing finer particles, where much of the heavy metals are found, than their counterparts. The vacuum-assisted dry sweepers are particularly good at removing respirable particulate matter, thereby improving overall air quality.

Other factors determining the effectiveness of streetsweeping are the frequency with which it is performed and the number of passes conducted per run. In order to remove 50 percent of street dirt then the streets should be swept at least once between storms and two passes should usually be conducted per run in order to achieve removal rates of total solids as high as 75 percent. The climate is another factor that contributes to the effectiveness of streetsweeping in that road sweeping tends to achieve better results in areas with marked wet and dry seasons

The type of road sweeper you should employ depends on the specific conditions present in the site to be swept. Mechanical sweepers are better at removing large debris and cleaning wet streets but they can also produce significant amounts of airborne dust. Vacuum-assisted and regenerative air sweepers, on the other hand, are able to pick up more fine particles and heavy metals but are less effective when it comes to cleaning wet streets. If cutting down on respirable particulate matter is a priority then vacuum-assisted dry sweepers should ideally be used.