What are the Importance of pre treatment in ZLD Systems?
The main goal of pre-treatment in Zero Liquid Discharge Plant is the elimination of Total Suspended Solids (TSS), Chemical Oxygen Demand (COD), and colour, while handling composite dyeing effluent.
Importance of pre-treatment in ZLD Systems
Pretreatment is frequently necessary.
1: Precipitation and settling techniques are frequently used in the industries to treat wastewater, for the removal of tiny amounts of inorganic pollutants.Wastewater is often fed into a series of reactor tanks, where heavy metal ions can be precipitated as insoluble hydroxide and sulphide salts, by adding caustic soda or lime, sodium sulphide, or proprietary organosulfides.
In order to coagulate the precipitates and generate huge flocs, specific polymers, ferric chloride, or alum are frequently added. These flocs settle in a clarifier.
2: Due to the wide range of ideal pH values for the precipitation of the metals present, two precipitation/flocculation steps are frequently incorporated. The clarifier's bottom is where the settled metal precipitates are collected, than they are filtered.
The highly soluble salts, such as calcium, magnesium, sodium, and ammonium, mixed with chloride and nitrate, as well as any organic components are left in solution by this treatment method, but it effectively reduces the suspended particles, metals, and acidity in the wastewater.
3: Some bacteria may use nitrates, ammonia, organics, and oxygen as food, turning them into water, CO2, and nitrogen. Biological treatment before discharge can lower the need for these substances. Some bacteria also have the ability to convert certain hazardous metal' oxidised anions,—like selenates and arsenates—into the insoluble metal.
However, the majority of chloride salt concentrations are not affected by common bacteria, employed in commercial biological treatment systems. In fact, wastewaters containing highly soluble calcium or magnesium chloride frequently need to be diluted, to prevent the bacteria from being killed.
You must be thinking! Why are we discussing all this?
Physical, chemical, and biological treatment procedures may not be able to lower concentrations, to the part per trillion levels necessary for the release of some chemical species, such as mercury and selenium, as wastewater discharge regulations have become stricter. Therefore, water recovery techniques based on membranes, are frequently employed in ZLD recycle and re-use programmes.
Use of pre-treatment in ZLD systems
Membranes, however, are often only able to treat dilute wastewater streams. For example, employing RO membranes to treat wastewater from wet FGDs is not an option, since the high concentration of dissolved salts (30,000 to 60,000 mg/L), causes the osmotic pressures to exceed acceptable limits. Evaporation must be employed to further recover water and concentrate salts, after the wastewater's dissolved salt content reaches a few percent by weight.
Despite the fact that removal efficiencies for various parameters vary from one approach to another, appropriate system improvements, process control, and plant operation schedules, can increase their performance.
Choosing ZLD Experts in India!
Finding a system for your company that is both economical and environmentally friendly can be difficult, particularly in light of the increasingly stringent effluent rules that are limiting your alternatives for discharge. That is why; you must consult experts, like Netsol Water, to manufacture your ZLD Systems.