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Forced Circulation Crystallizer for Water and Wastewater Zero Liquid Discharge

Forced circulation crystallizer is one of the main contributors in Zero Liquid Discharge wastewater treatment processes. This technology enables the extraction of pure water from wastewater and separates impurities in the form of crystals.

This comprehensive guide delves into the intricacies of utilizing Forced Circulation Crystallizer technology for water and wastewater ZLD, shedding light on its applications, advantages, and expert recommendations.


Forced Circulation Crystallizer
Forced Circulation Crystallizer Article

Article Outline


Forced Circulation Crystallizers for ZLD – an Introduction

A Zero Liquid Discharge system consists of three main stages:

(1) pre-concentration;

(2) evaporation;

(3) crystallization stage.

Different membrane-based and thermal-based technologies, including reverse osmosis, brine concentrator, forward osmosis, electrodialysis, and humidification-dehumidification, are utilized in various stages of the ZLD approach.

One of the common components used in the third stage of ZLD wastewater treatment is the crystallizer, where the crystallization process occurs. The crystal production process or crystallization is a liquid-solid separation method in which the solute is separated from the liquid solution and forms a pure crystalline solid phase.

Types of Forced Circulation Crystallizers

There are three basic types of crystallizers: Forced circulation (FC) crystallizer, draft tube baffle (DTB) crystallizer and Oslo crystallizer. Depending on the type of crystallizer, the achievable particle size varies from microns to millimetres.

Forced Circulation Crystallizer Drawing Display
Forced Circulation Crystallizer

Challenges in Traditional Crystallization Processes

Traditional crystallization processes, while effective to some extent, come with their set of challenges. High energy consumption and efficiency issues have long been pain points in achieving sustainable water and wastewater treatment.

In response to these challenges, the -Forced Circulation Crystallizer has emerged as a game-changer. This technology introduces a more efficient and energy saving approach to crystallization.


Introduction to Vacuum Crystallizers

Definition of Vacuum Crystallizer

Vacuum crystallizers are advanced devices designed for the crystallization of substances from a solution under reduced pressure conditions. This method is particularly effective in treating wastewater, where the removal of impurities is essential for environmental protection.

Importance of Vacuum Crystallizers in Wastewater Treatment

Wastewater, if left untreated, poses serious threats to ecosystems and public health. Efficient treatment methods, such as vacuum crystallization, contribute significantly to reducing the environmental impact of industrial and domestic discharges.

Applications of Forced Circulation Crystallizers in Zero Liquid Discharge

The versatility of Forced Circulation Crystallizers makes them applicable across various industries, including chemical, pharmaceutical, and municipal wastewater treatment, offering an efficient method for recovering water from RO brines.

Water Recovery from RO Brines

The process involves actively driving the circulation of the brine solution using external means, enhancing heat and mass transfer. Key components such as pumps and heat exchangers play a pivotal role in facilitating the separation of water from the concentrated brine.

Adopting Forced Circulation Crystallizers for brine treatment brings several advantages. Not only does it reduce the environmental impact of brine disposal, but it also proves to be a cost-effective and sustainable solution to recover water from RO reject.

Seawater Desalination

Recently, the efforts for finding a new competitive process for wastewater and seawater desalination have been extended into integrated/hybrid processes. The advantages of using integrated/hybrid processes can be categorized into two types, membrane fouling reduction and cost/energy saving.

To improve recovery rates, energy and cost efficiencies, various hybrid processes have been suggested. Integrated membrane separation/crystallization was designed and compared with conventional NF/RO processes. Recovery rate and costs were reduced and optimized as reported in this study: Comprehensive analysis of a hybrid FO/crystallization/RO process for improving its economic feasibility to seawater desalination - ScienceDirect.


The Advantages of Vacuum Crystallizers for Wastewater Treatment and Concentration

Efficient Impurity Removal

Vacuum crystallizers create a controlled environment with reduced pressure, inducing supersaturation in the solution. This controlled state promotes the precise separation of impurities from the liquid phase, ensuring an efficient removal process.

Energy Efficiency

Compared to traditional crystallization methods, vacuum crystallizers demonstrate superior energy efficiency. The reduced pressure conditions lead to lower boiling points, requiring less energy for the phase change during crystallization.

Improved Heat Transfer Efficiency

The thin film nature of certain vacuum crystallizer designs enhances heat transfer efficiency. This feature is particularly advantageous in processing heat-sensitive materials, ensuring effective crystallization without compromising product quality.

Heat Dissipation drawing explanation in a Forced-Circulation Crystallizer
Heat Dissipation in a Forced-Circulation Crystallizer

Resource Recovery

Vacuum crystallization allows for the recovery of valuable resources, such as salts, from the concentrated solution. This is achieved by manipulating temperature and pressure conditions, facilitating the controlled crystallization of the desired substances.

Reduced Environmental Impact

The targeted approach of vacuum crystallizers in removing pollutants from wastewater minimizes the overall environmental impact. By selectively crystallizing impurities, the process contributes to cleaner effluents and reduces the ecological footprint of wastewater treatment, especially in brine reduction and concentration systems.



Despite the initial investment, vacuum crystallizers prove cost-effective over time. The reduced energy consumption, along with the minimal maintenance requirements, contributes to lower operational costs, making it an economically viable solution for wastewater treatment applications.

High Purity Crystals for Disposal

The controlled environment in vacuum crystallizers ensures precise crystallization, leading to the formation of high-purity crystals. This is particularly advantageous in industries where the feed wastewater is highly contaminated and the disposal costs of sludges are high.

Versatility in Handling Various Substances

Different types of vacuum crystallizers, such as forced circulation and agitated thin film crystallizers, offer versatility in handling a wide range of substances. This adaptability makes vacuum crystallization suitable for treating diverse types of wastewaters with varying compositions, such as RO reject from many different industries.

Scalability Opportunity

Vacuum crystallizers can be designed and scaled according to the volume of wastewater to be treated. The scalability factor ensures optimal performance across a range of industrial applications, from small-scale operations to large industrial facilities. For treating larger flowrates, many small units can be combined to crystallize the effluent in different stages or a MVR crystallizer can be manufactured.

Minimized Fouling and Scaling

The design features of vacuum crystallizers, such as forced circulation and agitated thin film methods, help minimize fouling and scaling issues. This is achieved by promoting uniform heat transfer and preventing the build-up of impurities on the crystallization surfaces. Also, the double jacketed boiler design makes sure that the feed solution doesn’t contaminate the main components of the equipment, as shown in the drawing below.

Low Maintenance Requirements

The design simplicity of vacuum crystallizers contributes to low maintenance requirements. Regular maintenance is manageable, and the reduced risk of fouling and scaling further minimizes the need for extensive upkeep.




Forced Circulation Crystallizers stands as an industry standard approach to water recovery from water and wastewater in zero liquid discharge systems.

Its ability to address environmental concerns, coupled with economic benefits, positions it as a key player in promoting sustainable water and wastewater management practices.


 Frequently Asked Questions (FAQs)

How does Forced Circulation Crystallizers differ from traditional crystallization methods?

Forced circulation crystallizers actively drives solution circulation, improving efficiency, and reducing energy consumption, distinguishing it from traditional methods.

What industries can benefit from Forced Circulation Crystallizers?

Forced Circulation Crystallizers find applications in various industries, including chemical, pharmaceutical, and municipal wastewater treatment, and desalination plants as well.

Are there any potential drawbacks to implementing Forced Circulation crystallization technology?

While highly efficient, considerations such as compatibility and initial costs should be evaluated before implementation. The total flowrate and capacity may require attentive analysis before investing in such technology.

Where can I learn more and explore Forced Circulation Crystallizers?

If you are interested in learning more about forced circulation crystallizers for ZLD systems, at YASA ET we focus on technological advancements and materials innovation to further improve the efficiency of vacuum crystallizers. Get in touch with us for more info:




YASA ET can help you with designing and manufacturing custom made ZLD systems
Get in touch with our team for more info.


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