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ZLD (Zero Liquid Discharge) is a treatment process with which wastewater is completely removed from a system. The aim is to reduce wastewater while at the same time generating purified water for reuse. An evaporator and crystallizer are used for this. The evaporator ensures that the liquid waste is thickened, while the crystallizer processes the concentrate into solid. Other advantages: Reclaiming valuable resources that can be sold or recycled Cost minimization of waste disposal through reduced waste water volume Less need for further fresh water extraction due to the recycling of water Reduction of transport costs for disposal and associated environmental risks.
By introducing advanced pre-treatment processes that reduce thermal treatment to a minimum, Qwair has further optimized the ZLD process. Compared to the competition, we achieve lower energy and chemical consumption (cooling, heating and electrical energy) as well as reduced capital costs. Modular and compact constructions with short production times are integrated in our holistically designed process systems.

Economical processing line for typical saline process solutions – approx. 15 to / h accumulation Since a purely thermal treatment consisting of an evaporator system with crystallization is too expensive and energetically uneconomical in this case, we use the advantages of individual process steps connected in series in order to be able to implement a safe and particularly economical process. Our focus is on the minimization of thermal separation technology, including optimal pre-concentration in order to minimize costs and amortization.


Because only holistic approaches lead to economically combined solutions. This saves approx. 30% of the investment costs and approx. 40% of energy costs compared to conventional systems. In the first step, in this example, sediments and undissolved substances are separated out in a sedimentation system and the solution is fed to the membrane technology via filtration.

The membrane technology combination (UF-NF or RO) can concentrate the solutions through the application of up to approx. 160 bar in modules up to near the crystallization limit, whereby the permeates (produced “pure water”) can be recycled in process water quality. In the next step, the high concentrate of the brine is further “dewatered” with the help of a thermal stage or thermal centrifuge until it has a firm consistency. This is done taking into account the energy contained in the warm concentrates of approx. 65 ° C. The valuable substances contained can be removed in this intermediate step.