Littering on the roads/streets is a major problem in India. The debris (generated by vehicles and pedestrians), biomass (leaves, twigs, etc, causing microbial action in bitumen) and stagnant water enhance road surface abrasion, which is becoming the main bottleneck for maintaining good cleanliness and hygienic standards of Indian roads.
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, leading to abrasion and damage, researchers said.
Vacuum sweeping is another technique used in road cleaning which becomes inefficient in wet or moist environments and is ineffective to remove stubborn road debris. The large turbine of the vacuum sweeping machine agitates the nearby dust and increases the suspended particles in the air. 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 vacuum increase the noise levels.
To provide a solution to this, researchers at the CSIR-Central Mechanical Engineering Research Institute (CMERI), Durgapur in West Bengal, have developed a machine that could be useful in maintaining good cleanliness and hygienic standards of Indian roads.
This machine sucks out the wastewater from the drain/manhole using a slurry pump. The drain water passes through multiple chambers and is screened by different mesh size sieves, before it is finally treated with chemical disinfectant. The treated water is stored in a separate chamber that is used in the jetting operation.
The water intake capacity of the machine from one manhole is more than 1,000 litres. The machine can utilise the water to clean the road up to the next available manhole within 50-70 meters.
“During the preliminary tests carried out by the CSIR-CMERI, 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 a jetting hose and is sprayed on the road at appropriate 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”, said Prof. (Dr.) Harish Hirani, director, CSIR-CMERI, in a statement released by the institution.
It is also noticed that particulate matter due to non-exhaust sources such as emissions from wear of vehicle parts, road surface, resuspension of dust deposited on the road surface, etc., have been increasing. Tyres and road wear particles contribute majorly towards PM10. Not only particles from tyres and roads, but street sweeping also contribute towards bitumen wear and micro plastics.
As compared to sweeping the road manually and through vacuum cleaning machines, water spraying (at 2 to 10 bar pressure to wash out the dust/debris) reduces the curbside PM10 level significantly.
As per the available reports, street cleaning through water jets reduces particulate matter PM10 by 90% during the first hour of washing and around 18% on a daily basis. After the water flushing operation, slurry must be collected to avoid the bitumen roads getting damaged by prolonged exposure to water and the same should be recycled to minimize the water stress.
Performance of this machine depends on water pressure, water volume, and orientation of nozzles, collection of slurry water and its in-situ treatment. In addition, water evaporation during hot days contributes towards evaporative cooling effects. As the drain water is recycled and reutilized responsibly for road cleaning operations, the machine is well suited for regular and safe maintenance of roads/streets.
(Article courtesy: India Science Wire)