A Zero liquid discharge system is an advanced technological approach to treating effluents from industries so that the volume of liquid waste is reduced to zero at the end of it and the solid waste generated is disposed of appropriately.
Water shortage, rising environmental concerns, water economics, and several environmental regulations paved the way for the development of a robust effluent treatment process to minimize water wastage and facilitate the recycled use of water. ZLD treatment systems are incorporated in various industries in the United States and Europe followed by India and China to avoid off-site wastewater management costs and contamination of inland water bodies.
Through this blog, let us identify the benefits of implementing a zero liquid discharge system in an industrial facility and also look at the key aspects of the ZLD plant design.
Key benefits of using a zero liquid discharge system
Oil & gas, petrochemical, chemical, power, mining, and heavy engineering industries usually generate a large effluent. Here are some of the significant advantages of employing a ZLD system at your industrial facility.
- Retrieves valuable byproducts like salts and other minerals.
- Cost-effective as ZLD systems save – fresh water acquisition costs, off-site wastewater disposal, and management expenses, and reduced transportation charges.
- Recycles treated wastewater for rerunning the same industrial processes.
- Conserves water
- Prevents contamination of water bodies.
- Recovers more than 95% of liquid waste to render a dry sludge that can find purpose in the cement manufacturing industry or be deposited in a landfill.
Zero Liquid Discharge Plants Design
Industrial effluent contains water alongside minerals and salts in it. So, a ZLD treatment system aims to extract useful byproducts and water out of the effluent to convert it into a cakey mass fit for disposal or reuse. Here is a basic outline of a zero liquid discharge plants design and the four primary phases of the wastewater treatment process. Although this is the main plant design most industries are installing, there might be a few more customizations needed based on the type of facility that is installing this system. CentPro develops robust and user-friendly zero-liquid discharge systems.
Phase One: Pretreatment of the effluent
Pretreatment comprises the removal of particulate matter, suspended solids, and dissolved substances from the effluent with the help of simpler processes like filtration, sedimentation, precipitation, flocculation, coagulation, and more.
Below are the details of the several methods employed to pretreat the effluent.
Reactor – Required for precipitation of solid materials like metals and silica. This step can be combined with the coagulation of caustic soda, lime, alum, or aluminum chloride to remove the bulk of suspended solids.
Chemical Feed – A flocculation chamber is employed to catch the colloidal matter and convert it into the form of suspended solids. For this, the coagulated particles are stirred along with either long-chain polymers (charged molecules).
Sedimentation / Filter Press – Gravity settlers are employed to concentrate the secondary solid waste into a sludge blanket. At this juncture, a water layer separates which is sent forward for further treatment and the sludge is ejected into a sludge tank.
Ultrafiltration – Helps to isolate and remove traces of particulate matter and suspended solids. Ultrafiltration is also employed to prevent scaling and corrosion of the line of treatment.
Phase Two: Concentration of the effluent
In this stage of a ZLD treatment system processes such as reverse osmosis, brine concentration, and electrodialysis are employed.
- Reverse Osmosis – Removes dissolved solids in bulk.
- Brine Concentrators – They are used to further reject the RO stream to reduce the volume of waste.
- Electrodialysis – Here membranes with charged ions are used to further concentrate the brine.
Phase Three: Transformation of the effluent into a solid state
This stage involves the final conversion of the semi-solid waste into a solid, cakey mass.
- Evaporator – Evaporators are employed to evaporate the remaining water. This phase can also be combined with deaeration to remove dissolved gases.
- Crystallizer – Finally to boil off remnants of liquids, crystallizers are employed to convert the waste into a solid and cakey disposal material.
Phase Four: Recycle the recovered water and treatment of the solid waste
The final stage includes recycling the treated water for reutilization by various industrial processes. Simultaneously, the pressed sludge is either dumped into a landfill or reemployed in suitable industries like the construction industry.
Zero liquid discharge systems prevent contamination of mainland water bodies by industrial wastewater, thereby, significantly reducing water pollution. It is also considered useful to recover potential resources from the effluent. Therefore, experts recommend installing ZLD plants to take an economical and environmentally responsible approach to running your industrial facility.
Now that you understand the merits of using a ZLD system, drop in your inquiries to CentPro today.