by Dhruv Mehta & Snehal Saurav Pandey
According to projections made by the Indian government's Central Public Health and Environmental Engineering Organization (CPHEEO) in its report 'Improving Municipal Solid Waste Management Services', the Indian house building industry alone is facing a shortage of aggregates to the extent of 55 billion m3. Furthermore, an additional 750 million m3 of aggregates would be required to achieve the targets of the road building sector. Such a discrepancy between supply and will lead to increased pressure on natural resources.
To address the difference between the available supply of materials and demand, India's Infrastructure Leasing & Financial Services Limited (IL&FS) recently set up India's first Construction & Demolition (C&D) waste recycling facility in Burari, New Delhi.
Operating at a capacity of 500 tonnes per day (TPD), the plant has been successfully processing C&D waste into recycled aggregates which can be used for brick making and building roads.
Click to Enlarge Plant Details
In collaboration with Municipal Corporation of Delhi (MCD), IL&FS Environmental Infrastructure & Services ltd (IEISL) has developed a pilot project to demonstrate the potential benefits of increasing the recycling rates for C&D waste in Delhi.
The project itself has been set up on a Public Private Partnership (PPP) basis, which has proved successful as it serves the dual purpose of saving landfill space on the one hand and also developing the market for C&D recyclables.
The facility is located in Burari on approximately seven acres of low and marshy land which has provided by the MCD for a period of 10 years.The C&D waste processed at the plant is used in readymix concrete and other construction materials Tackling the logistics of C&D wastes in delhi
In the processing facility, IEISL collects some 500 tonnes per day of C&D waste from three designated zones in Delhi - Karol Bagh, Sadar- Paharganj and City. The C&D waste is recycled into aggregates at the waste management facility and in turn converted to Ready Mix Concrete (RMC), pavement blocks, kerb stones, and concrete bricks. So far IESL has collected approximately 450,000 tonnes of C&D waste over a period of 22 months.
A 175 metre long road connects the gate to the main road south of the plant. Internal peripheral tracks developed to facilitate the sustained movement of loaded vehicles to the weighbridge in all weather conditions, and further to the unloading areas followed by their exit to the main road. The buildings conform to the IS code standards.
IEISL operates and maintains an optimum number of vehicles in accordance with the prevailing demand for collection and transportation services within the designated areas. The vehicles are equipped with GPS system to track their movement on a continuous basis. A single shift running from 9pm to 6am is used for the movement of waste from designated areas to the plant.
The average load carrying capacity of a double axel tipper truck is 15 tonnes and that of a single axle tipper truck is nine tonnes.
Seven single axle and five double axel tipper trucks are currently being used. Each tipper truck makes four trips per shift where one round trip is approximately 40 km. The plant is designed to work in two shifts i.e. 16 hours a day, operating 330 days in a year.
An MCD representative is present at the time of loading the C&D waste and a digital weighbridge weighs the tonnage of waste received at the plant. Further to this, a video surveillance system has been installed at the plant and both real time and recorded footage can be accessed and viewed.
The 30 tonne capacity weighbridge is used to maintain an electronic database of the details of each consignment received at the site.To meet its road building objectives, India would require an additional 750 million m3 of aggregates Credit: Drajay WORKING PROCESS
A stationary crushing unit has been installed for dry processing of waste. It has a capacity to process up to 60 tonnes per hour of C&D waste. A wet processing system known as 'CDE C&D system' is also installed to extract soil from the unprocessed soil and plaster rejects.
Upon arrival the mixed C&D waste needs to undergo manual segregation to segregate the waste into whole bricks, big concrete pieces and mixed C&D waste. All large sized pieces are resized to 200mm to 400mm by both mechanical and manual means.
The resized particles and the mixed C&D waste are then fed to a hopper which is equipped with a vibrating grizzly feeder. The grizzly features a 60mm opening grid for batch processing. The <60mm fraction is sent directly for wet processing, while the >60 mm fraction is sent to the crusher for size reduction.Whole bricks and concrete pieces are separated from the mixed C&D waste when it arrives at the facility Washing machines
The wet processing unit consists of a grizzly, a log washer, vibro screens, an Evowash sand washing machine and a thickener which is capable of segregating sand from mixed C&D waste. The processing system is designed for a feed capacity of 60 tonnes per hour (TPH) and sand washing capacity of 40 TPH. The static feed conveyor delivers material to a pre-screen for removal of 3mm and below particles. The pre-screen materials (<3mm) report to the sump for further process.
Material from the grizzly is fed to the log washer where it undergoes intense scrubbing in wet conditions which removes light contaminants such as wood & plastic. The water added along the feed to the machine helps loosen particles adhering to the lumps of waste and the repeated tumbling in the machine releases the fine slime. The waste exiting the process is then sent for further processing.
Rinsing and Resizing screens are used to size aggregates. Three deck pro-grade screen equipment is used for screening and grading.
The screen is provided with a high pressure jet washing system in each deck which ensures thorough rinsing of the material and removes most of the fines under 3mm from the feed.
The washed oversize material from the top deck of screen forms the >20 mm product and that from middle deck forms the 10mm to 20mm product and that from the bottom deck 3mm to 10mm product.
The >20 mm material is sent back into the crusher for further size reduction and <3mm material is sent to the Evowash for further recovery. The Evowash is used to remove most of ultra-fines out of the system as clay. The overflow from the system is fed into the aquacycle high rate thickeners.
Here dense sludge of circa is added to aid settlement of sludge. The recycled water is released from the thickener to the water tank. The settled sludge is sent to the filter press which separates the sand solid from the liquid water.Awareness of good recycling practices are slowly gaining traction in Delhi, and more facilities are planned New from old
After separation of the solids from the liquid, all aggregates of mixed C&D waste are crushed to a smaller size with the help of Vertical Shaft Impactor (VSI), also known as sand making machine. The material is crushed until the desired fineness is obtained.
Similarly, aggregate produced from the concrete pieces in the C&D waste is sent to a batching plant for the production of RMC, which can then be used in non-load bearing structures. Thus a wide variety of pre-cast products can be produced by using recycled C&D waste as a raw material. To date 362,244 tonnes of C&D waste has been collected, of which 92,700 tonnes has been processed and used for the development of the plant site, 54,912 tonnes has been used to develop Sunahari and Barapulla Nallah, 153,000 tonnes has been used to produce materials such as pavement blocks and kerbstones. The remaining 61,332 tonnes has yet to be processed.
Click to Enlarge Project Cost
The capital investment for this plant has been estimated taking into consideration the latest manufacturing cost and the costs of the equipment and materials. IEISL's commitment to the project is $3.32 million out of which $2.21 million has already been spent.
The $3.31 million of expenditure consists of $1.18 million of capital investment and $1.01 million of working capital. The capital expenditure incurred by the project is proposed to be recovered over a period of 10 years by deriving value from the processed C&D waste.Conclusion
The amount of C&D waste generated in India is tremendous. Recycling this waste would not only lead to reduced pressure on the natural resources but would also lead to mass employment in the waste sector. Even though the project is still at an early stage, C&D waste recycling practices are slowly gaining awareness. The plant at Burari has proved to be a success. As a consequence, the company is setting up its operations in East Delhi and Gurgaon as well.
Dhruv Mehta and Snehal Saurav Pandey are students in Environmental Enginering at Department of Environmental Engineering, Delhi Technological University and recently completed a research project at the Burari C&D recycling facility.