Sequences and stages in HYDROZON® process
Flocculation
The aim of flocculation is to optimise the filtration process. Flocculants are inorganic electrolytes compensate electrical charges on the surfaces of solids. This results in the formation of micro-flocs and macro-flocs, which in turn form larger agglomerates. In this way, they allow the filtered separation of colloid-disperse water impurities.
The flocculant is added to the raw water upstream of the filter stage in a reactor. This guarantees optimum mixing and distribution of the flocculant. Ozone also supports micro-flocculation.
1st Ozone treatment stage
The following are the main processes that occur during the 1st ozone treatment stage:
- Disinfection of the raw water
- Oxidation of iron to form iron hydroxide that can be filtered
- Oxidation of manganese to form brownstone that can be filtered
- Splitting of highly molecular organic compounds to optimise the biological mineralisation in the filter bed (ozone bio-filtration)
- Oxygen enrichment to supply the aerobic micro-biology in the biologically active filter bed
Oxidation with ozone
In oxidation, elements or compounds are combined with oxygen. In the process the substance to be oxidized emits electrons that are in turn taken up by the oxidation agent.
Ozone is activated oxygen with a high specific oxidation potential (2.07 V).
Potentials of important oxidants:
| Oxidant |
Potential in V |
Oxidant |
Potential in V |
| Hydroxyl radical |
2.80 |
Hypochlorite |
1.49 |
| Ozone |
2.07 |
Chlorine |
1.36 |
| Hydrogen peroxide |
1.78 |
Chlorine dioxide |
1.27 |
| Potassium permanganate |
1.70 |
Oxygen |
1.23 |
Due to its high oxidation potential, ozone produces a very fast oxidation of organic and inorganic water impurities. The HYDROZON® process utilizes ozone both to oxidize the raw water and for the final disinfection of the pure water.
Oxidation gives rise to, among other things, low-molecular, assimilable organic carbons (AOC). These substances are mineralised in a biologically active filter bed that follows the oxidation.
Filtration
In filtration, a liquid containing solid particles is separated into its liquid and solid components. The optimised filter bed retains corpuscular solids and allows through the filtrate, i.e. the filtered liquid.
The following also occur in the filter bed:
- Reduction of residual ozone in the upper filter bed and
- Biological mineralisation of AOC in the lower filter bed
The filter performance is particularly influenced by the following factors:
- Filter materials
- Bulk density, grain diameter and grain surface of the filter materials
- Mixability of the filter materials
- Filter heigth
- Filtering velocity
Biological mineralisation
Highly molecular compounds are split up into low-molecular groups by the oxidation with ozone. The now assimilable organic substances are largely mineralised by aerobic bacteria in the ozone-free layer of the filter bed for the most part to form water, carbon dioxide, nitrogen etc.
This process - splitting through oxidation followed by biological mineralistion - replicates and accelerates the natural water purification process taking place in aquifers.
Normally, special appropriately dimensioned activated carbon filters are used for the biological mineralisation (ozone bio-filtration process).
Hygiene processing/disinfection
During disinfection, pathogens are so greatly damaged that they can no longer infect other living organisms. In the HYDROZON® process, the raw water is automatically disinfected since the ozone acts both as an oxidizing agent and as an approved disinfectant.
Finally, a second ozoning operation takes place in the HYDROZON® process. The following processes occur in this ozoning:
- Oxidation into nitrate of nitrite that may have arisen during the biological mineralisation
- Compensation any oxygen deficit that may have arisen as a result of the biological activity in the filter bed
- Disinfection and hygiene processing of the pure water
Measuring the redox potential
The redox potential provides information about the ratio of oxidized substances to reducing substances. Provided that the system configuration is suitable, the redox potential can therefore also be used as a quality parameter for the process control of a water treatment system.
In the HYDROZON® process, the redox voltage is measured after the final oxidation in the pure water.
The higher the redox potential and the lower the residual ozone concentration, the better the treatment performance.
If, for example, a redox potential of 750 mV is measured, with a residual ozone concentration of only 0.02 mg/l, this points to a high level of hygiene processing for the water.
The HYDROZON® process - application examples
In the HYDROZON® process, the treatment problem is solved by means of a proven, tried-and-tested process and by proven, staged performance units.
Basic process
The illustration shows the "basic method" for treating drinking water in accordance with the HYDROZON® process.
The HYDROZON® basic process is especially suitable for the treatment of
- Spring water with a high level of turbidity and bacterial contamination
- Ground water with high concentrations of:
- Iron
- Manganese
- Arsenic
- Hydrogen sulfide
- Ammonium (nitrification in the biologically active filter)
- Nitrite
Process with advanced oxidation process (AOP)
The process with an advanced oxidation stage is necessary for the treatment raw water contaminated by residues of chlorinated hydrocarbon substances (CHC) or pesticides..
This process is particularly suitable for treating groundwater contaminated by human sources, such as
- Water contaminated with pesticides
- Water contaminated with chlorinated hydrocarbon substances (CHC)
Hydrogen peroxide (H2O2) is also added in the advanced oxidation process. The oxidation capacity is increased by the formation of hydroxyl radicals (OH.). In this way, chemicals designed for long-term stability are broken down and opened up for biological mineralisation.
The subsequent biological filter stage mineralises the fragments and thereby minimizes the formation of metabolites.
Process with adsorption stage
The HYDROZON® process with an additional adsorption stage is used for the treatment of waters with a high degree of contamination, especially for the treatment of:
- Groundwater with no or insufficient groundwater protection
- Karst water
- Bank-filtered water
- Groundwater influenced by surface water
- Surface water from lakes
Process with triple oxidation
The HYDROZON® process with triple oxidation and double filtration is used mainly for treating surface water and water contaminated by human sources.
- Surface water from lakes and rivers
- Bank-filtered water from heavily contaminated water sources
- Thermal water with hydrogen sulfide, methane and other reduced substances.
|
Overview
