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Middle East shows the way in construction and demolition waste recycling

As CDE is expanding its global footprint with an increasing number of wet processing plants dedicated to the recycling of construction, demolition and excavation (CD&E) waste, the GCC is taking steps to curb the increase in waste going to landfill every year.

As Frost & Sullivan was reporting last year that in 2020 the GCC would be generating up to 120 million tonnes of waste per year - a stark jump from the already staggering figure of 94 million in 2015 – the region’s countries are becoming recycling-savvy in order to lead the way to a greener and more profitable future for the construction industry.

CDE - An impressive global portfolio

Due to the highly variable nature of construction, demolition and excavation waste each plant CDE designs is built according to the specific requirements of the project. Differing levels of contamination, fines content and variability of input materials (excavation waste, railway ballast etc) require an individual approach to each and every recycling plant for construction and demolition waste. CDE, which is celebrating its 25th anniversary in 2017, has been developing CD&E wet processing waste recycling solutions across the world for 12 years. Each plant is co-created with the customer for an exact fit both in terms of footprint but also in terms of product quantity and quality requirements.

For instance, CDE installed the largest bespoke CD&E waste recycling solution in the world in Norway in 2014 for quarry company Velde Pukk AS. Processing 300 tonnes per hour of CD&E materials diverted from landfills, the company recycles 600,000 tonnes of waste per year thanks to CDE’s wet processing technology. Waste is converted into two grades of sand -0-2mm and 2-4mm. A range of washed aggregates are also being produced in the form of 4-11mm, 11-16mm, 16-22mm, 22-90mm and an oversize +90mm aggregate. Velde are also utilising the dry cake output from the filter press, which contains +80% of dry solids for use in the creation of embankments.

CDE CD&E waste recycling solutions

Ruchin Garg, CDE Regional Manager for MENA, said: “Most operators still rely on dry crushing and screening to recycle C&D waste; this method only produces low-value aggregates with limited applications and does not allow for the recovery of -5mm material, representing 20% to 25% of incoming waste, which ends up in landfills. With CDE wet processing solutions, operators can produce high value sands and aggregates with gradings adapted to a large range of applications, and enjoy the added bonus of   recovering and transforming  -5mm material into a saleable product.  

“The CDE recycling technology allows operators to increase their production of high quality sand and aggregates by recovering and treating materials that are no longer waste but saleable products, preventing the diversion to landfill of up to 90% of incoming waste.

“A typical CDE plant consists of modular units that are combined to create a complete solution offering capability and performance, above all customised to meet the client's needs. This enables the customer to benefit from excellent value for money. Each of these unique modular units is pre-assembled and pre-wired at the CDE assembly facilities in Northern Ireland. Before consignment, they undergo a series of tests before dismantling into sub-assemblies, thus simplifying their transport and reassembly on site. They require a minimal amount of civils and ensure a substantial reduction in assembly and commissioning costs. The plants are operational in record time, which contributes to maximising their return on investment.” 

How the CDE CD&E waste management system works

A typical CDE CD&E waste management system is fed by excavator, allowing the operator to remove obvious large or problematic objects. Feed then passes through a vibrating head over the feed hopper before being conveyed to a rinsing screen. This unit separates minus 5mm slurry which is passed to the compact sand plant. This sand washing plant accurately removes silts and clay below 75μm, via the integrated cyclone, to offer a consistent and sellable dewatered sharp sand product.

Managing waste water and clay / silt is one of the key challenges for this type of system. When a CDE AquaCycle high-rate thickener with integrated polyelectrolyte dosing station is added to the wet processing plant, fine contaminants rapidly settle to form a dense sludge which can be pumped away to a remote settling area. Clean water then overflows the thickener to an adjacent water storage tank after being filtered to remove any residual floating contaminants. From here water can be readily recirculated to the washing system.

Aggregates and clay-bound particles pass directly from the rinsing screen to the CDE Rotomax logwasher. This is equipped with twin shafts fitted with chromomolybdenum blades. Highly attritioned material is then discharged from the front of this unit to a dewatering screen below. This recovers liberated fines and water which are then passed back to the rinsing screen via a ground sump and pump, encouraging initial fluidisation of the feed material whilst reducing the fresh water requirement. Light contaminants including organic elements such as wood and grass are actively floated off from the rear of the specialist log washer. This is then passed to a trash removal screen which recovers water and fine particles to the sand washing unit.

The dewatered aggregates are then conveyed to a dry screen for final size classification. The system can produce up to five washed products at the same time. 

Ruchin Garg, Regional Manager for CDE in MENA, says: “The wet processing of construction, demolition and excavation waste materials can add much greater value and open up new markets for the products than more conventional dry screening processes. It also releases additional products including commercial sand.

“In addition, using the latest washing technologies means that water availability and waste fines management is no longer a significant barrier to efficiently processing even the most difficult materials.

In countries where the preservation of the environment is vital and at the core of a well thought strategy for industry growth, CDE’s high-tech solutions for construction, demolition and excavation waste recycling are perfectly adapted to quarries and construction companies wishing to diversify their offering whilst making a fast return on investment.”