SYSTEM FOR ELIMINATION OF AMMONIA AND REMOVAL MANGANESE FROM WELL WATERS,
1. Manganese elimination
Principle: Manganese kations are present in form of bivalent ionic solution, in the water.
Precipitation of manganese can be realized by oxidation to Mn(III) form, when Mn(OH)3 precipitates from water.
4 Mn(II)+(aq) + O2 (g) + 8 OH- + 2 H2O 4 Mn(III)(OH)3 (s)
The solubility constants of manganese hydroxides are Manganese(II) Hydroxide - Mn (OH) 2: 2×10-13, Manganese(III) Hydroxide-Mn (OH) 3: 1×10-36. The Mn(III) ions are practically insoluble and can filtered from the water. (MnO2 precipitates only at higher pH then 8,3)
Oxidization: Can realized by air- or ozone gas injection or by filtration through a catalytic filter media like Klinomangan it is. The Klinomangan media is a very active and highly disperse manganese dioxide, which oxidizes the bivalent manganese, coming with the raw water, while its tetravalent manganese will be reduced to trivalent and bivalent form.
3Mn(IV)O2 + 2Mn++ + 6H2O 3Mn(II)O + 2Mn(III)(OH)3 + 3 H2O
This reaction is accelerated by presence of little quantity of silver ions.
The best way of manganese removal is the combination of the two methods. However, the Klinomangan media can work properly without any gas injection.
Filtration of Mn (OH)3 precipitate: The precipitate can filtered out by a sand filter with backwash facility. If we use Klinomangan for catalytic oxidation, this filter media itself filters out the manganese hydroxide from the water.
Regeneration: cyclic exhausting of this media, which will contain bivalent manganese after exhausting, follows the process of catalytic oxidation and filtration by Klinomangan media. Sodium-permanganate solution can recharge the exhausted media.
2. Ammonia removal
Principle: Ammonia is present in water in dissolved form of gaseous ammonia NH3 and in form of ammonium ions NH4+ . The equilibrium between the two forms depends on the pH: the ammonia is more stabile at higher pH. Both forms can be absorbed in crystalline structure of sodium-clinoptilolite easily. This zeolite has very high absorption selectivity for ammonia. The total capacity of pure sodium-clinoptilolite reaches 1,5 mEq/g. Calcium and magnesium ions are absorbed concurrently from the water, but slower and with less selectivity. Therefore, if the filtration speed is enough high, the absorption of alkali-earth cations is negligible compared with absorption of ammonia and the total salt concentration of the water will not notably be affected.
The ion exchange process: This happens in the filter media Granofilter-NaFe.
The reaction is:
a.) NH4+ + Na+-CLINOPTILOLITE NH4+ - CLINOPTILOLITE + Na+
b.) Ca++ + Na+-CLINOPTILOLITE Ca++ - CLINOPTILOLITE + Na+
c.) Mg++ + Na+-CLINOPTILOLITE Mg++ - CLINOPTILOLITE + Na+
The most likely reaction is the a.) , at high flow rate.
As result of this ion exchange process, the ammonia concentration wills strongly reduced or disappear from the water, while the calcium and magnesium concentration decrease is not remarkable (less than 10 % of total hardness).
The regeneration: It is realized by 10 % solution of sodium chloride + Iron sulfate. The solution has to be pumped in the GRANOFILTER-NaFe filtering media, from bottom to top, in the opposite direction of the normal filtration. The volume of regenerant solution has to be 1-2 volumes of the intergranular porosity (50%) of the filtering media. The spent regenerant can be disposed in the canal.