Water treatment, an elaborate process to obtain the purest water

Sensory optimisation

tREATMENT To REMOVE UNDESIRABLE Odour AND TASTE

Inorganics and organic compounds that produce a taste and/or odour in water must be removed in order for the water to be deemed fit for human consumption. This kind of water treatment is generally carried out using aeration, clarification or adsorptive materials.

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Pretreatment

Elimination of sizeable particles

Depending on the nature of the raw water, a pre-treatment step is employed to eliminate sizeable solids (sand, debris, leaves, etc.) that may interfere with the subsequent steps of the treatment process.

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Oxidation

Oxidation of organic and inorganic compounds

Oxidation is used to oxidise inorganic and organic compounds. This step may also decrease the sensory parameters of odour, taste and colour of the treated water.

The most common oxidising agents are oygen, ozone and potassium permanganate. In Germany, chlorine dioxide and chlorine are allowed only for disinfection issues.The choice and dosage of the reactant depend upon the raw water quality, the treatment objectives and, in particular for the chlorine dioxide, the limits set on grounds of chlorite formation.

Precipitation/ Iron and Manganese removal

Removal of heavy metals

In water treatment, the pH value is increased using Akdolit^® products in order to remove heavy metals. Heavy metals have a tendency to precipitate as hydroxides at high pH values. This effect is used as a side reaction during decarbonisation to remove iron, manganese and other heavy metals.
The same effects as for heavy-metal removal are also obtained in the use of fixed-bed filters for the stabilisation of acidic soft waters by removing excess carbonic acid with lime or dolomitic products. In addition, Akdolit^® offers also special filtration materials for manganese removal even in the neutral zone, a task that is hard to achieve compared with iron removal, which is generally performed without difficulty.

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Filtration

Removal of particles and retention of organic/inorganic compounds

During filtration, the particles contained in the water are retained in the fixed-bed filters. Aborbent materials remove any organic ingredients that may be present in the water. Regulation of the pH value can have a positive effect on the removal of metals and other ions. Depending on water quality, multi-layer filtration can be an effective solution for optimising filtrate quality as well as investment and operating costs. Akdolit^® offers a wide range of filtration materials for single- or multi-layer filters used in the treatment of utility-, swimming-pool- and drinking-water.

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Desalination

Depending on the membrane type, molecules and ions are retained, according to their size, while water molecules pass through the membrane. In this way, unwanted compounds and salts are removed.

The membranes are the heart of this technology and need to be protected by water pre-treatment.

For drinking water production, it is indispensable to replenish the permeate from reverse osmosis or nanofiltration with vital minerals. For this purpose, remineralisation using lime and products of dolomtic origin presents many advantages. Stabilisation of the pH-value by increasing buffer capacity will improve the chemically corrosive properties of the water. This avoids impairment of drinking water quality caused by corrosive damage in the supply network. Akdolit^® offers a wide range of hardening and deacidification products for your water-treatment.

Neutralisation

ESTABLISHMENT OF Calco-carbonic equilibrium

The reaction known as neutralisation, deacidification, remineralisation or hardening, consists in removing water acidity (mainly the aggressive CO₂) and increasing the alkalinity and the calcium and magnesium content, in order to adjust the pH and achieve calco-carbonic equilibrum. Simultaneously, with the increase in the pH, heavy metals are also removed from the water.

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Softening / Decarbonisation

Decreasing water hardness and alkalinity

Water softening and decarbonisation consists in reducing the overall hardness of the hard, mostly scaling and calcareous waters to protect pipework from calcium carbonate deposits. Softening can be achieved by several processes, such as ion exchange or lime-based treatment.

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