ZLD system installation for RO plants

Zero liquid Discharge (ZLD) is a water treatment process in which all wastewater is purified and recycled, therefore, a zero discharge remains at the end of treatment. Zero Liquid discharge is such wastewater treatment method that involves ultrafiltration, reverse osmosis, evaporation / crystallization, and fractional electro-deionization.

The energy, oil and gas, chemical, petrochemical, mining and other industries generate large amounts of wastewater that must be disposed of. Typically, this wastewater is discharged surface water, an evaporation basin, or deep well injections. Since the concern about discharge and its detrimental effect on environment has grown,it has led to the development of Zero Liquid Discharge (ZLD) processes. 

Zero Liquid Discharge can be defined as a method of recovering the maximum water from a wastewater source that would otherwise be discharged into a stream, which is now reused into the facility itself. This water isreused significantly. One of the driving forces behind zero liquids disposal is growing public concern about the impact of such discharges on the environment. This concern leads to greater regulation and limitation of wastewater discharge. To reach the sustainability goals, many firms are opting for a ZLD system.

HOW CAN WE ACHIEVE ZERO FLUID DISCHARGE?

• 1. There is no one-size-fits-all solution as its made-on demand specification. The composition of the wastewater, the different flows to be treated, the site-specific operating costs, the availability of space and other factors are decisive factors for an optimal design.
• 2. The system objectives for a zero liquid discharge system are to avoid the discharge of liquid wastewater, generate solids for landfills or reuse, and recycle high-quality water that can be usefully reused.
• 3. Design objectives are to minimize price and system operating costs without significantly affecting the manpower required to operate. In addition, the system must be designed with flexibility to meet installation requirements and be safe and reliable.
• 4. Evaporation systems are more expensive to operate than membrane systems, with crystallizers being the most expensive. For this reason, membrane systems are preferred to reduce investment and operating costs of the evaporation system.
• 5. Depending on the composition of the wastewater, pre-concentration with a membrane system can dramatically reduce the need to size the re-evaporation system and therefore the capital and operating costs of the system.

To achieve high yields in a wastewater membrane system, proper pre-treatment, such as softening and pH adjustment, is often required.The brine concentrators are developed to deal with the deposition of poorly soluble divalent salts such as calcium sulphate and calcium carbonate, as well as silicon dioxide, which is also common.

Forced Circulation Crystallizers are generally used to concentrate brine drainage from upstream concentrators, although small wastewater streams are sometimes treated directly with a forced circulation crystallizer. The crystallizers are designed to handle the crystallization of all salts, both poorly soluble and highly soluble sodium salts, such as sodium chloride and sodium sulphate, without excessive build-up and without excessive cleaning intervals.  This robustness comes at the expense of higher specific energy consumption and higher specific capital costs.

Solids generated by a forced circulation crystallizer are generally collected and dewatered through an indexing belt filter or by a centrifuge. In such a case, the solids are collected and generally disposed of in a conventional landfill provided the waste passes the toxicity Characteristic Leaching Procedure (TCLP) test.

So, the method of installation of ZLD in combination with one of its hybrid model, is easy ,as Netsol provides a hands-on installation service with every type of hybrid model which ever suits your requirement the best.