SIEBTECHNIK TEMA | Zero Liquid Discharge – ZLD

Zero Liquid Discharge ZLD

Caring for the future

Sauberes Wasser – Unterwasseransicht, man blickt durch die Wasseroberfläche in den Himmel

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.

The Earth’s resources are finite. For decades, knowledge of this scarcity of resources and raw materials has led to the sustainable recovery of recyclable materials, which are then returned to the value chain.

Water is particularly significant here.

Only 2.5% of the water on Earth is fresh water. Only a small part is really accessible to humanity, namely 0.3% (in lakes, rivers and reservoirs).

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.

Waldszene bei schönem Wetter – sauberes Wasser fließt durch einen klaren Bach – man sieht, warum Umweltschutz und Nachhaltigkeit so wichtige Themen sind.

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) process graphic. Fresh water is fed into an industrial process where it becomes contaminated. This dirty water is purified in water treatment plants. The treated water can be reused. The valuable substances recovered from the wastewater, such as salts, are also returned to the production cycle, while the remaining solids (waste materials) are disposed of properly.

ZLD – How wastewater treatment sustainably conserves valuable resources.

Zero Liquid Discharge helps to:

Protect the environment and water resources
Fulfill government regulations
Achieve higher levels of water recovery
Reduce wastewater volumes
Reduce costs
Recover salts from wastewater (e.g. potassium sulfate, sodium sulfate, sodium chloride, lithium salts, mixed salts)

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.

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 processes - How wastewater is made usable again in a treatment plant. The water passes through various stations, including filters, evaporators, crystallization and centrifuges. In this way, the wastewater is turned back into usable water and separated solids or raw materials can also be reused.

ZLD process – The various purification steps to make both the water and the valuable substances it contains usable again

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

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

Each process and each customer has its own specific requirements.

SIEBTECHNIK TEMA has an extensive portfolio of systems and components, centrifuges and dryers that are tailored to your needs.

Our experts will be happy to advise you!

Find out more about these applications

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.

Decanter centrifuge – solid bowl

Our decanters are individual, functional and versatile. They offer highly efficient separation of even the finest solids with almost complete clarification of the liquid phase.