How to remove Hardness from wastewater?
The amount of calcium and magnesium salt in water is measured by its hardness. The hardness of surface water is often lower than that of groundwater.
Hardness in wastewater and removal techniques
High amounts of both calcium and magnesium salts can be found in effluents from urban wastewater treatment plants, contributing to the hardness of this specific wastewater flow. It particularly applies to areas where water is drawn from subsurface sources via distribution systems. When hard water is used in the home, the domestic wastewater becomes hard as well. The hardness of wastewater is not a criterion for comparison. However, in the realm of water recovery, it is an essential study topic.
Categorization of hardness levels
1-Water with a hardness of up to 100 mgCaCO3/L is considered very soft,
2-Water with a hardness of between 100 and 200 mgCaCO3/L is considered soft,
3-Water with a hardness of between 200 and 350 mgCaCO3/L is considered medium-hard,
4-Water with a hardness of between 350 and 550 mgCaCO3/L is considered hard, and
5-Water with a hardness of above 550 mgCaCO3/L is considered very hard.
How to treat hardness in wastewater?
The physical methods include reverse osmosis and nanofiltration, as well as other high-pressure membrane filtration procedures.
Chemical approaches include the use of reagents such as calcium hydroxide (lime), sodium bicarbonate (soda), sodium hydroxide (caustic soda), phosphates, barium salts, and others to chemically precipitate insoluble precipitate or to bind calcium and magnesium ions into complex compounds.
Physico-chemical approaches rely on a variety of ion exchangers that can exchange their own ions with those in the surrounding solution.
Membrane filtration allows contaminants to be separated on a molecular or ion level!
This method is most commonly used to desalinate saltwater and brackish water, to provide ultra-pure water, and to soften water and remove radionuclides, heavy metals, nitrate ions, and organic compounds, including low molecular weight micropollutants. Data on the usage of this technique for wastewater treatment is likewise limited.
Depending on whether the procedure is reverse osmosis, microfiltration, ultrafiltration, or nanofiltration, the membranes have successively smaller holes and a lower volumetric flow of the permeate.
What do these membrane procedures retain?
The most compact membranes, such as those employed in reverse osmosis, theoretically pass-through only water; nanofiltration membranes allow for the separation of ions of various valences and organic compounds; and ultrafiltration membranes retain tiny suspensions, colloids, bacteria, and viruses. Microfiltration membranes having the biggest holes allow microsuspensions to be retained. Membrane hydraulic resistance is growing as a result of their physical structure, necessitating the use of ever greater pressures.
Pressure membrane filtering is employed in the following fields of water/wastewater treatment:
1: Reverse osmosis (RO) – desalination - generation of potable water from saltwater and brackish water,
2: Using microfiltration and/or ultrafiltration (MF/UF) to produce drinking water from groundwater and surface water,
3: Generation of drinking water from groundwater and surface water using nanofiltration (NF) with and without coagulation (C) and microfiltration as a preparatory treatment (MF),
4: MF/UF and/or NF/RO treatment of process fluids for shutting water circuits in industry,
5: MF/UF and RO generation of ultra-pure water for industrial use,
6: Wastewater treatment using membrane bioreactors (MBR) and reverse osmosis (RO) to produce industrial or drinking water.
What can we offer?
If you are concerned about the removal of hardness from wastewater or your drinking water, you can contact Netsol Water for an expert advice, or, if you need help designing an efficient hardness removal treatment system, contact us.