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Zero Liquid Discharge ZLD

Caring for the future

Clean water - underwater view you look through the water surface into the sky

Water is one of the most valuable resources on Earth. Global environmental awareness, the desire for sustainability, and the focus on conserving and protecting our water supplies are steadily resulting in more environmental regulations and stricter rules regarding the use and disposal of water in industry.

The machine solutions developed by SIEBTECHNIK TEMA for Zero Liquid Discharge (ZLD) projects are used in many industrial sectors to purify or recycle process water and to recover valuable substances from wastewater.

Sustainable resource saving

But demand for high-quality water is increasing, driven by ecological changes, environmental factors, the growing world population, and increasing urbanization. This fact has led to greater environmental awareness worldwide regarding the availability and quality of water. As a result, there are increasingly stringent government regulations regarding the disposal of industrial wastewater.

Due to scarce water resources, and rising costs for water treatment and wastewater disposal, the use and conservation of water is a key issue in the manufacturing industry around the world. The focus here is often on repeatedly using treated water and reducing wastewater volumes, and even on avoiding wastewater entirely. Demand for new and increasingly efficient recycling technologies is growing, especially in regions that have limited access to available water sources and wastewater disposal options.

Forest scene in fine weather - clean water flows through a clear stream - you can see why environmental protection and sustainability are such important issues
Wastewater treatment plant - wastewater in a basin

The benefits of Zero Liquid Discharge (ZLD)

In order to increase the environmental friendliness of industrial plants, ZLD is used in a wide variety of fields, e.g. in power generation, and in the steel and chemical industries.

ZLD improves the environmental and economic footprint of a plant. Firstly by reusing water, and secondly by avoiding the discharge of wastewater, which could incur high costs or damage the environment. In this way, ZLD helps companies comply with strict regulations and guidelines regarding wastewater disposal and water reuse, as well as protecting the local environment.

In addition, ZLD enables the recovery of valuable resources from wastewater, which can be reused in the industrial process or sold.

Zero Liquid Discharge (ZLD) Prozessgrafik. Frischwasser wird in einen industriellen Prozess eingeleitet und dort verschmutzt. Dieses Schmutzwasser wird in Wasseraufbereitungsanlagen gereinigt. Das aufbereitete Wasser kann wiederverwendet werden. Die aus dem Abwasser gewonnenen Wertstoffe, wie z.B. Salze werden dem Produktionskreislauf ebenfalls wieder zugeführt, die restlichen Feststoffe (Abfallstoffe) werden fachgerecht entsorgt.

Industries that use ZLD include e.g.:

  • Pharmaceuticals
  • Chemicals
  • Oil, gas & refineries
  • Power generation
  • Steel & mining
  • Cellulose & paper
  • Tanning & textile dyeing
  • Beverages & food
  • Drinking water treatment
  • Agriculture

What is ZLD?

Zero Liquid Discharge (ZLD) is a treatment process focused on the economical reduction of wastewater. This produces clean water suitable for reuse, saving money and protecting the environment.

ZLD systems utilize advanced wastewater/ desalination technologies to treat and recycle virtually all the wastewater generated. In this process, the components dissolved in the water are converted into reusable solids such as sludge and salt. Different technologies are typically combined, such as thermal evaporation, crystallization, desalination and drying, and centrifugal separation.

Wastewater treatment - plant

The ZLD process

The first step is to filter or precipitate waste and chemicals that are easy to remove. The wastewater is then concentrated by means of evaporation. In the third step, the concentrated waste stream is fed into a crystallizer.

In the last and decisive step, this suspension of water and crystallized solid is separated using a centrifuge. The efficiency of the upstream steps matters little; it is the use of the right centrifuge that determines the overall efficiency of the plant.

ZLD Prozesse - Wie Abwasser ein einer Aufbereitungsanlage wieder nutzbar gemacht wird. Das Wasser durchläuft verschiedene Stationen u.a. Filter, Verdampfer, Kristallisationen und Zentrifugen. So wird aus dem Abwasser wieder Nutzwasser und abgeschiedene Feststoffe bzw. Rohstoffe können ebenfalls wiederverwendet werden.

Centrifuges for Zero Liquid Discharge (ZLD)

Solid-liquid separation is the critical final step in most ZLD processes, as this is where the remaining water is separated from the solids, in most cases salts. Dewatering is mostly done with decanters, SHORTBOWL decanters, pusher centrifuges and CONTURBEX centrifuges. For dewatering coarse residue, our HSG vibratory centrifuges have proven effective.

Finer mixed salts from crystallization plants are centrifuged using downstream SHORTBOWL decanters, SHS pusher centrifuges and CONTURBEX centrifuges at temperatures sometimes exceeding 100°C. The high-alloy stainless steels, Hastelloy® and titanium materials required for these machines are provided with appropriate wear protection made of tungsten carbide, Stellite® or ceramic tiles.

SIEBTECHNIK sieve screw centrifuge CONTURBEX H700 for lactose - hall view with several machines
SIEBTECHNIK sieve screw centrifuge CONTURBEX H700 for lactose - hall view in production - 8 machines
14 STK SIEBTECHNIK TEMA sieve screw centrifuges type CONTURBEX in various stages of completion at the centrifuge technology center in Mülheim an der Ruhr
SHS pusher centrifuge for sodium sulphate in the factory hall in Mülheim an der Ruhr

Wear Protection

SIEBTECHNIK TEMA centrifuges are specially optimized for the respective separation task. When selecting materials, austenitic and ferritic stainless steels have proven themselves in centrifuge construction for applications subject to normal stresses.

For processes in which abrasive materials are processed, the centrifuges must be provided with effective wear protection. Starting with hard coal processing, we have been continuously developing wear protection systems since 1922.

Our centrifuges can be equipped with highly developed wear protection systems made of e.g. tungsten carbide, Stellite® or ceramic tiles, to name but a few. Rubber coatings or matrix coatings have also proven themselves in various applications.

If required, our engineers develop new and efficient solutions in coating, bonding and joining technology for our customers worldwide.

Centrifuge Components Materials

Centrifuge components must not only withstand high forces, but also process-related stresses such as corrosion, wear and high temperatures. Cost and availability of materials also play an important role. Our customers select the necessary product-contacting materials according to these very specific requirements.

Duplex and high-alloy stainless steels, Hastelloy® and titanium materials for a wide variety of processes and stresses are part of our daily business in centrifuge construction. Our quality management has developed very detailed and cost effective processes for design, manufacturing processes and component testing based on European guidelines.

Typical sheet metal and forging materials for centrifuge wetted components include

  • EN 1.4404 / AISI 316L
  • EN 1.4571 / AISI 316Ti
  • EN 1.4462 / AISI 318LN / Duplex
  • EN 1.4410 / AISI F53 / Super Duplex
  • Lean Duplex
  • EN 1.4539 / AISI 904L
  • EN 1.4547 / 254SMO®
  • EN 1.4529 / AISI 926
  • EN 2.4819 / INCONEL® Alloy C-276
  • EN 2.4602 / Hastelloy® C22
  • EN 2.4610 / Hastelloy® C4
  • EN 3.7035 / Ti-II / Titan 994-Ti-grade 2
  • EN 3.7235 / Ti-IIPd / Titan 994 Pd-Ti-grade 7
  • and their casting materials
SHORTBOWL decanter for lactose in the production hall in Mülheim an der Ruhr

SHORTBOWL decanter centrifuge

Due to the special geometry of the rotating parts, the SHORTBOWL decanter centrifuge - solid bowl is best suited for separating fine solid particles with a high specific density difference to the liquid phase.

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SIEBTECHNIK TEMA decanter centrifuge DZ 7. View from the drive side of the decanter.

Decanter centrifuge – solid bowl

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SHS pusher centrifuge in fertilizer production

SHS pusher centrifuge

The SIEBTECHNIK TEMA SHS pusher centrifuge has established itself and proven itself as a modern high-performance unit in many industries.

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SIEBTECHNIK sieve screw centrifuge CONTURBEX H700 for lactose - hall view with several machines

Screen scroll centrifuge CONTURBEX

The CONTURBEX is a continuously operating, filtering centrifuge with a very wide range of applications.

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Oscillating centrifuge HSG

HSG vibrating centrifuge

With the SIEBTECHNIK TEMA HSG vibrating centrifuge you can continuously centrifugally dewater the world's largest solids capacity of bulk materials.

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