Page 25 - HUB-4 Magazine Issue 71
P. 25

 Filter presses and their function in the washing process
In today’s world there is more demand for the earth’s natural resources than ever. For companies to succeed and grow, sustainability and the circular economy are a vital consideration in the business plan. As planning permissions for natural aggregates are taking longer to grant with escalating costs, and landfill space for construction materials once regarded as a waste is reducing so we have the perfect storm brewing between supply and demand.
Many companies in the aggregate supply chain are now considering and purchasing aggregate wash plants suitable for the processing of construction, demolition, and excavation waste to recover the valuable sand and aggregate from this material for reuse in construction. This is a very sustainable approach to the finite resource of construction sand and when done correctly can also add significant value to the materials produced from the wash plant.
An important consideration for washing aggregates is how the dirty water from the wash plant containing the silt and other contaminates from the washing process are to be dealt with. Lagoons are rarely an option today due to space constraints and the fact that the Environment Agency will want any water from the plant managed in a controlled and measurable way to guarantee no pollution.
The washing of recyclable aggregates is often regarded as relatively straight forward when a tried and tested process is followed. However, with such a variable input material the key to a successful washing operation is the water treatment plant
and ultimately what is produced from the silt fraction that has been washed and scrubbed out of the feed material.
Technologies available:
There are several technologies currently available for receiving a thickened sludge from a water treatment plant, removing the solids from the water to produce a manageable cake, and returning the clean water back to the washing process. When deciding which of these to use consideration must be given to the initial capital cost versus operational costs, civils requirements, space available and ultimately what is going to be done with the silt cake that is produced at the end of the process. Nov-Dec 21 - Issue 71
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