Today, we are living in a world where we can’t take water for granted as a resource. It has become increasingly valuable due to scarcity. Industrialization has threatened its availability on two fronts: high requirements for industrial processes and releasing the wastewater into freshwater bodies, i.e., further contamination of good quality water.
However, with modern wastewater treatment technologies like Zero Liquid Discharge, water consumption by industries can be reduced. With ZLD wastewater treatment, the industries can reuse the wastewater after its treatment, and the remaining sludge can be disposed of in a safe manner.
ZLD is also helpful in recovering potential resources that are present in the wastewater. There are many organizations that leverage ZLD for their waste, as they can sell the solids that are produced or reuse them as part of their industrial processes.
In this article, we will go through various aspects of ZLD and understand how it is important for wastewater treatment.
Zero Liquid Discharge is a wastewater treatment technique in which all water is recovered and contaminants are converted into solid waste.
Though many wastewater treatment technologies aim to recover as much freshwater as possible, ZLD is gaining increasing importance because the cost and challenges of recovery increase as the wastewater gets more concentrated. Generally, the concentration increases due to the presence of compounds like salinity, scaling compounds, and organics. All these compounds increase the cost of treatment and maintenance of water treatment technology.
There are various components in the system of zero liquid discharge system. These components are mainly influenced by these factors: quality and quantity of contaminants in the wastewater, the needs of industries, and the systems’ required flow rate. In a common ZLD system, these are the major components:
There are five major steps involved in the Zero Liquid Discharge Treatment. Let’s understand each one in detail:
In the pre-treatment stage, firstly, the clarifiers are used for the removal of large matter and suspended solids present in the wastewater through precipitation. To make this process faster, chemicals like lime or caustic soda are used to stimulate coagulation. These chemicals react with suspended solids, and there is a need for continuous mixing for the best chemical interaction with suspended solids.
After coagulation, the flocculation process will begin. In this process, polymers are added to the wastewater and gently stirred so that larger particles called flocs are formed.
Then, the water flows into a sedimentation tank, allowing the flocs to settle and be raked out. As per the quality of the wastewater, additional treatment may be required for efficient treatment.
To get high concentration in the wastewater, processes like reverse osmosis (RO), brine concentrators, or electrodialysis are employed to gain maximum efficiency. These processes are capable of extracting 60-80% of the water.
Though the RO process is highly efficient in removing the majority of solids, pretreatment is still required to prevent membrane fouling. If there are high salt concentrations in the wastewater, then brine concentrators are employed. The electrodialysis process works by using positively and negatively charged ions to create an electric field. It can extract the charged particles and concentrate the brine to saturation.
This is a thermal process in which water is evaporated, collected, and reused. Falling film evaporation concentrates water up to its initial crystallization point, also known as supersaturation. Additionally, it is an energy-efficient method. Then, acids are used to neutralize the solution to avoid the scaling of heat exchangers during the heating process. Sometimes, deaeration is also required to release dissolved oxygen, carbon dioxide, and other gases.
The solutions that get accumulated in evaporators are passed to crystallizers, where it is concentrated beyond the solubility of contaminants to form crystals. Lastly, a filter press is used to dewater the end product, and the water rereleased goes through the crystallization process.
The treated water is pumped into a holding tank, where it can be used for various purposes. It can be used for a variety of industrial activities, including drinking water and irrigation.
Zero Liquid Discharge is gaining importance due to its numerous benefits. Let’s know its major benefits:
As there is no discharge of contaminated water into the freshwater bodies, ZLD helps in the protection of rivers, lakes, ponds, and other aquatic bodies. It reduces pollution and safeguards aquatic species and public health.
ZLD systems allow for the recovery of precious resources, including freshwater, salts, and minerals from wastewater, encouraging resource conservation and sustainability. Some of the major elements that it helps in recovering are:
The governments of various countries, including India, the USA, China, the UK, and others, are giving strong emphasis to sustainability measures, including water protection. The environmental protection bodies have introduced various regulations and compliance measures. With ZLD, the industrial plants can align with these stringent compliances without any major headaches.
Ostensibly, the initial investment of the ZLD treatment may seem higher, but in the long run, it helps in saving costs in multiple ways. Firstly, the industrial plants require less water from the freshwater bodies. Secondly, they don’t need to face any legal issues or pay a fine for improper discharge of wastewater. Lastly, the recovery of valuable resources also compensates for the cost of investment.
As an industrial plant owner, you are required to conduct a thorough assessment of site-specific wastewater streams, composition, volumes, and treatment requirements for an effective ZLD strategy.
Choose appropriate treatment methods depending on the characteristics of the wastewater streams, taking into account scalability, energy efficiency, and operational requirements.
ZLD solutions should be seamlessly integrated with current infrastructure and industrial processes to maximize efficiency and reduce operational interruptions.
Establish reliable monitoring and control systems to guarantee ZLD plants run effectively, maximizing resource recovery and reducing energy usage.
You must give a contract for setting up a ZLD wastewater treatment plant to a company with vast experience in this industry. The company should provide proper consultation and meet all the environmental standards.
In this article, we have gone through all the important aspects of the ZLD process and understand how it is gaining high importance in wastewater treatment. At WiproWater, the best wastewater treatment company, we can help you with the setup of a high-efficiency ZLD treatment plant in your industrial premises. Let us know your requirements.