A vital element of the washing process is water, which brings it's own challenges in terms of cost and supply. In this project Terex Washing Systems integrated a number of intelligent water treatment products that manage to recycle up to 95% of the water used during the washing process. By designing the entire system Terex Washing Systems were able to integrate the water treatment products with the washing process, resulting in higher level of efficiency.
This wash plant recycles construction, demolition and excavation waste in Geneva, Switzerland, with a throughput of 100 tph. A Deep Cone Thickener, Flocculant Dosing Unit, a Filter Press and a Filter Cloth Washer are used to treat the water so that it can be recycled back into the washing system.
Deep Cone Thickener | Filter Press | Flocculant Dosing Unit
Featured Water Treatment Products
Aquaclear Water Management
The water used during the process of washing excavation waste is diverted to a collection sump while the desirable materials have been stockpiled ready for sale. This waste water will contain silt, clay and other contaminants which are important to remove from any saleable materials. From the sump this waste water is pumped into the Deep Cone Thickener. Before entering the thickener the waste water is dosed with flocculant by the FDU 3000 flocculant dosing unit. This causes the particles within the water to bind together, which results in contaminants settling at a faster rate. The flocculant dosage is continually monitored by the dosing control unit in order to optimise the settlement rate within the deep cone thickener.
Deep Cone Thickener
Within the Deep Cone Thickener the particles of clay and silt bind together creating larger, heavier particles that now settle more rapidly towards the bottom of the cone. The flocculent greatly speeds this process up and allows clean water to weir over the top of the deep cone into a clean water collection tank. This clean water is then recycled back into the washing process.
The waste particles collect at the bottom of the Deep Cone forming a sludge with a concentration of up to 50% solids by dry weight and is then transferred into a nearby buffer tank. Within this buffer tank the sludge collected from the Deep Cone Thickener is continually agitated so that it does not settle. The sludge remains in the buffer tanks until it reaches a certain volume and is then pumped into the Filter Press.
The Filter Press compresses the sludge with the aid of a high pressure pump, in order to remove the majority of the remaining water within the sludge. A total of 150 plates are used on this side beam Filter Press with a working pressure of 16 bar (232 psi). Each plate is covered with a backing cloth and a nylon filter cloth, which filters the sludge under pressure. This removes the remaining water within the sludge and the resultant filtrate water is collected in two troughs running along either side of the press. The filtrate water is then returned to the collection sump and recycled back into the deep cone thickener. The entire system is designed so that the cycle times for the Filter Press are as efficient as possible.
Once the cycle has been completed and the clean water removed, the doors below the Filter Press will open. This allows the filter cakes to be expelled from the press and land in the collection bays. The cakes are rapidly discharged in sets of 15 into the bay below. Any particularly sticky filter cakes that have not been discharged are removed using a pneumatic plate shaker mechanism. An inspection of the filter cakes show that they are very dry with almost all the water removed and re-introduced back into the wash plant.
Automatic Cloth Washer
The owner of the plant decided to install an automatic cloth wash system with the aim of maintaining optimum press cycles, increasing the lifespan of their filter cloths and reducing down time. This cloth washer uses high pressure water to clean each plate individually.
Johnston Patterson, Product & Applications Manager at Terex Washing Systems explained that, “This water management system recycles 95% of the water used for this application. The customer only needs a small tank of water to top up the system every so often. This has a hugely positive impact on the environment and has added financial benefits.”
With a fully integrated water management and recycling system the customer has a complete solution for washing construction, demolition and excavation waste. View the video below or get in touch for more information.