Zero Liquid Discharge Systems (ZLD)
The presence of a liquid effluent is an issue in all the industrial installations. It is particularly true when many difficulties are faced in the assessment of the environmental impact and the approval of the communities in which new plants have to be installed.
The necessity of reducing the environmental impact minimising and sometimes annihilating the production of waste water, leads to the implementation of Zero Liquid Discharge Systems (ZLD), which are at first designed to recover all the liquid effluent from the water & waste water treatment plant units.
Treated sewage, de-oiled water, neutralised chemical drains, rainwater, boiler blow-down streams are further treated to meet the specifications for recovery.
The sludge coming from the different treatments is physically de-hydrated, the saline water stream coming from the demineralization section is concentrated, where feasible, up to the maximum extent and then taken to evaporator-crystallizers where the dissolved salts are precipitated as crystals and the produced slurry is further dehydrated into the Sludge Dewatering System.