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Environmental Information for Sweeping Professionals |
The Current Status of Vacuum and Waterless Sweeping as Best Management PracticesThere is a current emphasis on regenerative air sweepers as the industry's BMP-type machines for reducing stormwater pollution runoff. However, road surface and other factors play an important role. In this context, the efficiency of vacuum sweeping, as well as the emerging role of waterless sweeping, should perhaps be considered as viable alternatives.Editor's Note: In its June 2006 issue, Better Roads magazine included an excellent story that provided an overview of current and projected stormwater regulations, including how they may affect all of us in the years to come. Unfortunately, sweeping was all but excluded in the magazine's analysis. As editor of WorldSweeper.com, I responded with an article about how sweeping should be part of any stormwater pollution reduction effort. This was printed in the September, 2006 issue of Better Roads. Now, in response to my article, Elgin's Mark Kinter sent to me an overview that includes his take on the subject. The following 'letter to the editor,' which reads, in part, like an advertisement for Elgin's machines, is what Kinter had to say on the subject. by Mark Kinter, Technical Consultant, Elgin Sweeper Company
It's important to note that regen sweepers MUST be used on a surface level enough to ensure that the head shrouds maintain contact with the roadway. If the roads are older and have traffic grooves, as well as built-in swale, this will not be possible. When the seal is broken on a regenerative air machine, the dust expelled is significant and the sweeping performance is diminished. It's standard knowledge that the majority of the debris to be swept lies within 24" of the curb line. In the Elgin line of sweepers, as well as others, the side [also called 'curb' or 'gutter'] brooms are nearly identical on the mechanical broom and regenerative air sweepers. Therefore the cleaning action in the gutter is virtually identical. This result has been proven in recent testing by Roger Bannerman in the City of Madison. It's also important to note that the maximum performance of a regen sweeper is achieved when it is operated at its maximum governed speed. At this speed, the noise may be prohibitive and the fuel consumption tends to be an issue. For these reasons, most operators don't run the regen sweepers in the most efficient cleaning mode. If sufficient water is used to control the dust generated by the side broom, a slurry is created that is then spread across the roadway. This slurry contains the small particles that contribute to stormwater pollution. If the road has a porous surface, the slurry will be trapped in the pores where it will eventually dry and become either airborne or be washed into the gutter with rain. This action is quite similar for both broom and regen sweepers that operate using water. If the water for the side broom is minimized, or eliminated -- at the cost of increased airborne dust -- the slurry will not be generated. The fine particles may then be picked up by the regen sweeper. A goodly percentage of it will also be picked up by today's mechanical broom sweepers. Again, keep in mind there will be an airborne dust issue to deal with [as a trade-off to not using water in a machine designed to use dust suppression]. The statement that the operating cost of regen sweepers is lower than broom sweepers is not qualified by a time frame. A new regen sweeper operating at max performance will experience the same side broom costs and more fuel costs, but does not have the main broom costs that a comparable broom sweeper will have. In our experience, in that regard operating costs are actually pretty close to a wash. If you consider the operating costs over a longer period of time, you must factor in the cost of replacing regen sweeping heads, hoppers, fans, housings and hoses due to blast-through. This cost will vary significantly from manufacturer-to-manufacturer based on design features. If a significant amount of water is not used to suppress dust, this blast-through can occur at a rapid rate... I have personally encountered regen customers that have experienced operating costs as high as $80 per hour due to blast-through when sweeping abrasive rock particles. This will not occur with a mechanical sweeper. There are, however, alternatives to a regen sweeper that resolve these issues. A pure vacuum sweeper that has the ability to shift the vacuum nozzle into the curb line will be capable of removing curb deposits at a much higher efficiency. It will also not spread the debris from the gutter across the roadway. If the vacuum nozzle is situated behind the gutter broom, even packed deposits can be removed without spreading debris. In addition, because water is added within the vacuum head, the sweeper is able to pick up dry material, which eliminates any slurry formation. When sweeper efficiency testing is performed, [standard practice is for] a small 3-5hp vacuum cleaner to be used to remove the remaining particles in the roadway. Imagine how well a 100hp vacuum cleaner would work. This is the kind of performance a true vacuum sweeper will offer.
Another solution to the problem of sweeping wet slurry is to use a waterless sweeper. Although there have been no published tests performed on this type of sweeper, the visible results are so striking that contractors that have used this type of sweeper for milling jobs will not use another if one is available. Elgin offers two examples of this technology on the street sweeping market: Elgin Eagle FW and the Elgin Pelican waterless. We hope you consider these items in your future articles. Mark D. Kinter is a Technical Consultant to Elgin Sweeper Company. He may be reached by calling 952-334-7882, or via email sent to: mkinter@elginsweeper.com.
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When I read your Better Roads response, I noted that you continue to emphasize the use of regenerative air sweepers over other types
for storm water purposes. There are several technical issues that need to be clairified in this issue.
Currently there are only two sweepers offered in the US market capable
of shifting the vacuum head into the curbline: Elgin's 