Road Cleaning Machine – Machine flushing of roads using recycled drain water
Durgapur: Waste management is a major problem in India especially littering on the roads/streets. The debris (generated by vehicles and pedestrians), biomass (leaves, twigs, etc., causing microbial action in bitumen) and stagnate water enhance road surface abrasion, which is becoming the main bottleneck for maintaining good cleanliness and hygienic standards of Indian roads/streets.
Various methods for cleaning roadsides and streets are in practice. The manual sweeping with bamboo brooms (the most commonly used technique for road cleaning in India) disintegrates the debris into small granules and possibly contributes towards particulate matters. With time a worn-out broom/brush can induce micro cracking in roads/streets and make it ineffective in cleaning the roads.
Vacuum sweeping is another technique used in road cleaning, which becomes inefficient in wet/moist environments and ineffective to remove debris adhered to roads. The large size turbine of the vacuum sweeping machine agitates the nearby dust and increases the suspended particles in the air as shown in figure – 1.
The vacuumed air is to be exhausted to the outside environment but the residence time is generally insufficient to allow gravitational settling of PM10 and even after installing exhaust filters, the fine dust particles escape into the nearby atmosphere, which may increase PM 2.5 and PM 10 levels. Also, the large moving parts and the turbine system for creating a vacuum increase the noise levels.
In the recent past, it is also noticed that particulate matter is due to non-exhaust sources (emission from wear of vehicle parts, road surface, resuspension of dust deposited on the road surface, etc.) Have been increasing. In one of the reports, the average emission due to tyre wear is approximately 0.2kg/capita/year. Tyre and road wear particles (TRWP) contribute majorly towards PM10. Not only particles from tyres and roads, but street sweeping also contributes towards bitumen wear microplastics.
As compared to sweeping the road “manually” and “through vacuum cleaning machine”, water spraying (at 2 to 10 bar pressure to wash out the dust/debris) reduces the curbside PM10 level significantly. As per the reports, street cleaning through a water jet reduces particulate matter PM10 by 90% during the first hour of washing and around 18% daily. After the water flushing operation, slurry must be collected to avoid the bitumen roads getting damaged by prolonged exposure to water and same should be recycled to minimize the water stress. Machine performance depends on water pressure, water volume, the orientation of nozzles, collection of slurried water, and it’s in situ treatment. In addition, water evaporation during hot days contributes to evaporative cooling effects. As the drain water is recycled and re-utilized responsibly for road cleaning operations, the machine is well suited for regular and safe maintenance of roads/streets.
Based on these requirements, a machine has been developed at CSIR-CMERI in which the wastewater from the drain/manhole is first sucked out using slurry pomp. The drain water passes through multiple chambers and is screened by different mesh size sieves then it is treated with a chemical disinfectant. The treated water is stored in a separate chamber that is used in the jetting operations. During the preliminary tests carried out by the Institute, analysis of sprayed water quality was within the surface discharge limit and may not harm the bitumen in the road and the environment. The treated water passes through the jetting hose and is sprayed on the road at pressure and flow rate to push the debris so that all of it is collected to be picked up and transported. The discharged water flows back into the drainage/manhole system. The collected debris is then lifted using a grab bucket and dropped in the hopper of the vehicle. The water intake capacity of the machine from one manhole is more than 1000 L. The machine can use the water to clean the road up to next available manhole within 50-70 meters.