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Biological. Organic. Inorganic. Incrustation. Calcium carbonate, Magnesium carbonate, Calcium phosphate, Magnesium phosphate Barium or Calcium phosphate Calcium fluoride. Hydrocarbon Humic acids and fulvics Cationic Polielectrolite. Silica Clays Aluminium Iron Manganese.

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pretreatments

Biological

Organic

Inorganic

Incrustation

Calcium carbonate,

Magnesium carbonate,

Calcium phosphate,

Magnesium phosphate

Barium or Calciumphosphate

Calcium fluoride

Hydrocarbon

Humic acids and fulvics

Cationic Polielectrolite

Silica

Clays

Aluminium

Iron

Manganese

Bacteria

Fungus and yeast

Polymer extracellular

Disinfection or Bacteriostatic

Antiscalant or

Water softener

Active carbon absorption

Pretreatments

Demineralisers. Critical issue: contamination of membranes

Membranes, Getting dirty and obturation

Different previous filters

Prevention or process delay

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Biological Pollution

Collodial Material

Iron

Scaling by silica

Biological Pollution

Compaction

Chemical oxidation

damage

Excess pressure

damage

Pretreatments

Demineralisers. Critical issue: contamination of membranes

The membranes are contaminated by several causes:

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Pretreatments

Demineralisers. Pretreatments to remove Chlorine

Chlorine remover

Chlorine changes the membrane properties, allowing the salts to pass through the membranes easily, therefore chlorine must be removed before the RO treatment.

The filtering material is coconut shell carbon, with a particle size distribution of 1,2-2,5 mm. Chlorine with carbon leads to a chemical reaction producing CO2 (carbon dioxide) and chloride, both don’t damage the membrane. At the backwash stage, the particles settled in the filtering material are removed, and the carbon layer is rearranged (since the water goes through it) compressing the material and creating preferential channels that decreases the surface contact area between water and carbon.

The active carbon must be replaced within 12-24 months. In addition to the consumption due to the chlorine removal reaction, the continued water flow with salts will lead to a decreased contact area due to the formation of scales on the carbon surface, delaying the chlorine removal process.

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Pretreatments

Demineralisers. Examples ofcontamination of the membranes

Iron

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Pretreatments

Demineraliser. Pretreatment to remove Iron

Iron remover

The iron in water is usually found as Fe(II), highly soluble and not capable of being filtered.

Iron, as Fe(II), is not a problem for the membrane task, nevertheless, after its oxidation (due to the oxygen contact, or after being chlorinated) changes to Fe(III) form that is a solid in suspension, it will plug the mesh spacer and the membrane will get dirty.

The iron removal treatment lies in transforming the Fe(II) into Fe(III) form and its filtration. When Fe(II) has contact with the BIRM (manganese dioxide) it becomes oxidized, turning into Fe(III). Under this form the iron is not soluble, forming a granulated that can be sieved.

In order to make this possible, the water must have a pH between 7 and 8,5, in addition to an oxygen concentration higher than 15% in relation to the iron or manganese concentration.

We should take into account these premises at the start up stage, so if they are not fulfilled, it will be compulsory to check with our Central SAT.

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Pretreatments

Demineralisers. Examples ofcontamination of the membranes

Solids in suspension

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Pretreatments

Demineraliser. Pretreatments to remove solids in suspension

  • Silex Filter – Anthracite
    • Solids in suspension. The solid presents a low inertia in its capacity of flotation/decantation, remaining suspended. It is normal not to distinguish the particles individually if their sizes are about the micrometer magnitude. The smallest particles (0,2-1 microns) are named as colloidal particles or colloids.
    • It is needed to eliminate the solids in suspension, which plugged the mesh spacer. The silex is silica sand, similar to beach sand, but with a particle size distribution of 0,7-1,3 mm. The anthracite is a heavy mineral carbon, with a particle size of 1,2-2,5 mm. We take materials with different densities in order to increase the filtration capacity and its quality.
    • The backwash is used as cleaning method, causing a mechanical rub. This rub releases and removes the filtered particles. The three materials, contained in the filter, are mixed after the backwash, coming apart again in the right order due to the density difference, just as it appears in the drawing.
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Pretreatments

Demineralisers. Examples of contamination of the membranes

Organic material

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Pretreatments

Demineraliser. Pretreatments to remove the Organic Material

Organic Material filter

Organic material: All substance or molecule containing carbon (except carbonates). The carbon is in any molecule that belongs or was a part of a living creature.

The organic material plugs the membrane, blocking it, and therefore decreasing its efficiency.

The filtering material has the same characteristics as in the chlorine remover.

The organic material, in contact with the carbon, sticks to the granulate due to molecular attraction forces.

We have to take into account that both the organic material filter and the chlorine remover, are units that enhance the bacterium growth, because the carbon granulates offer a wide contact surface with the water due to its “spongy” form, therefore we should control the likely bacteriological contamination.

If we have chlorine and organic material in the same water, IT WILL NOT BE NECESSARY to install a chlorine remover and an organic material filter, just placing the organic material filter will be enough (not the chlorine remover).

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Pretreatments

Demineralisers. Examples of contamination of the membranes

Biofilm

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Pretreatments

Demineraliser. Pretreatments to remove the Biofilm

Themicroorganisms(bacterium) can survive inside the water pipes of the equipments, excreting a jelly film (biofilm) that can block the membranes. To avoid this problem, we have two methods available, both exclusive among them.

Bisulfite

The product is sodium bisulfite. The solution to inject is prepared at a maximum concentration of 10 g/l.

It is dosed diluted in water, and after a period of 3-4 weeks, the content of the feeder drum must be renewed, even if the volume prepared is not yet finished, therefore the quantity of product to be prepared must be calculated.

The control of the dosage pump is included in the electric panel of the demineraliser, in this way it will be dosed automatically in the water flow, before the demineraliser inlet.

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Pretreatments

Demineraliser. Pretreatments to remove the Biofilm

Biocide

It is an organo-bromine compound (Genesol-30) with a wide bactericidal range (aerobic & anaerobic), suitable for all kind of membranes. It is acid and causes a partial dilution and the drag of the biofilm that could be settled in the membrane.

A 400 ppm concentration must be added for 20-30 minutes once a week. The dosage is done by the automatic program, starting the pump after one week and there is water demand. The product is corrosive and is NOT suitable for food applications.

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Pretreatments

Biocide vs Bisulfite

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Pretreatments

Demineralisers. Examples ofcontamination of the membranes

Lime

pretreatmentss
Pretreatmentss

Crystal of Calcium Carbonate (lime)

demineralisers
Demineralisers

Demineralisers. Examples ofcontamination of the membranes

Scalant process. How are the crystals formed?.

IONES

ION

PROTONUCLEUS

NUCLEUS

CRYSTALS

GROUP FORMATION

GROWTH

ARRANGEMENT

1000 atoms

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Pretreatments

Demineralizer. Pretreatment against lime

Water Softener

The Calcium and Magnesium are the elements with the most scalant power. It is not used as pretreatment stage for the demineraliser, but it is suitable for water treatment before the boiler inlet.

Resin

Antiscalant dossing

The Calcium and Magnesium are the elements with the most scalant power. The dosage of this element avoids the lime crystal formation.

demineralisers1
Demineralisers

Water Softener effect

Ca2+ (H2O) + R-Na+ ---- Na+ (H2O) + R-Ca

Demineralisers. Examples of contamination of the membranes

Difference between antiscalant and water softener

Antiscalant effect

THRESHOLD EFFECT AGENT

(Antiscalant)

IONS

CRYSTALS

IONS

NUCLEUS

Avoids the crystal formation

GROUP FORMATION

ARRANGEMENT

GROWTH

demineralisers2
Demineralisers

Difference between antiscalant and water softener.

Antiscalant doser system

+

Antiscalant drum

Water softener

+

Salt

demineralisers3
Demineralisers

Difference between antiscalant and water softener.

Water softener 2x100 litres

Salt Consumption:

  • Daily need of water: 21 m3 at 70 ºHF.
  • Necessary regeneration of the water softener every 9 m3
  • Number of regenerations per day: (21m3/day) / (9m3/ regeneration) = 2.3 regenerations /day
  • Consumption of salt per litre of resin in every regeneration: 0,2 kg/Litres of resin
  • Consumption of salt in every regeneration: 0,2 kg/Litre of resin x 100 Litres of resin = 20 kg of salt per regeneration
  • Salt consumption per day: 2.3 regenerations / day x 20 kg of salt/regeneration = 46 kg/day
  • Salt consumption in the same period of time (124 days): 46 kg/day x 124 days = 5.704 kg=228 sacks of 25 kg
  • Antiscalant dosage
  • Consumption of antiscalant product:
    • Daily need of water: 21 m3 at 70 ºHF.
    • “High” dosage of product: 5 mg/L = 5 g/m3
    • Daily product consumption: 21m3 x 5 g/m3 = 105 g/day = 0.105 kg/day
    • 1 drum of 10 L = 13 kg
    • So 1 carafe of 10 litres of antiscalant will last:13 kg / 0.105 kg/day= 124 days
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Demineralisers

Difference between antiscalant and water softener.

Conclusion: In 124 days of use:

Example of calculation

5.704 Kg of salt

=

1 bottle of 10 L (13 Kg)

Make yourself your calculations:

Price/kg Salt x 5.700 kg salt = EUR spent on salt

versus

RRP 10 L Antiscalant drum = 189,00 EUR

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Laboratory

Results of Analysis

Water sample

IT- 11-56 Test

IT- 11-55 Chlorine

Identification and

Delivery

Introduction of Analysis results

Recommended Configuration

Pretreatments

Selection of the pretreatment for demineralizer.

Advantage:

- Less maintenance

- Long lasting components

- Efficiency

- Better water quality

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Pretreatments

Mantenimiento Filtros de Pretratamiento

  • Maintenance each 12 months
    • Checking of conditions of the filter carried out by TAS Istobal
    • Replacement (if is necessary) of the content of the filter carried out by TAS Istobal
    • Collecting the used filter material by an authorized manager of waste, paid by the customer.