Every industry produces wastewater but not every industry has the facility of zero liquid discharge (ZLD) because it can be a complex process that requires a high initial investment. A ZLD treatment system also helps in stringent effluent requirements, by the U.S. Environmental Protection Agency’s Steam Electric Power Generating Effluent Guidelines.
What is a zero liquid discharge treatment system?
Zero liquid discharge means that every advance technologies of waste water treatment have a limit to produce zero waste at the end of processes. An efficient and well-designed ZLD treatment system includes:
• Handle variation of waste contamination and adjust the required chemicals.
• Recover around 95% of waste + treat waste and as well as it’s by-products
Components included in a basic ZLD Treatment System
The exact components of a ZLD treatment system will largely depend on volume of the waste and flow rate of the waste + contaminant present in specific amount. In general, ZLD treatment system typically includes:
- Clarifier: To precipitate out metals, hardness, and silica.
- Chemical feed: To facilitate the precipitation, flocculation, or coagulation of any metals and suspended solids.
- Filter press: To concentrate secondary solid waste after pretreatment.
- Evaporator: Vaporizing access water in the final phases of waste concentration
How does a ZLD treatment system work?
Specific treatment processes vary, but a typical ZLD treatment facility processes usually include the following steps:
Pretreatment: It is used to remove unwanted materials present in the wastewater stream that can be filtered or precipitated out and reduce the suspended solids. Sometimes this step requires the addition of chemicals such as caustic soda or lime which help in the coagulation a process in which various chemicals are added to a reactor or reaction tank which help to remove the bulk suspended solids and other various contaminants. The most widely used coagulates are aluminum-based such as alum and polyaluminum chloride.
After coagulation process it leads to the flocculation process where the coagulated particles are stirred slowly together with long-chain polymers, creating visible and settleable particles and after this many other processes are carried out such as Reverse Osmosis, Electro dialysis, Evaporation and Condensation process, Filtration process and many other process depends upon the scale of the particular industries. As the treated water is being reused then it’s pumped into the holding tank where it can be used as per the demands of the facilities and that leads to the ZLD.
This content was first published on the Chokhavatia website.