ADVANCED OXIDATION PROCESSING
Current water shortages and environmental discharge regulations have highlighted the importance of new technologies such as Advanced Oxidation.
Serious shortcomings with conventional wastewater treatment systems can be addressed using AOP.
Properly applied technology can transform organic compounds into more straightforward, stable inorganics ( water, carbon dioxide, and salts), allowing for no sludge and wastewater or storage water remediation.
Several contaminants resulting from industrial production are not biodegradable or may include toxic organic compounds, which can be effectively treated using advanced oxidation methods.
AOP can successfully remove:
- – P PCP’s
- – Dyes
- – Plasticisers
- – Microcystin
- – Toxic metals
As South Africa’s drinking water resources become increasingly compromised, ozone’s solid oxidative power is now recognised as an essential tool in water treatment procedures.
Add to this the power of adding oxygen to compromised water bodies, and you will see the magic of HARNESSING NATURES TECHNOLOGY.
Ozone … Some would call it “supercharged oxygen”, and rightly so Oxygen is essential to life and health.
Most inorganic or organic substances can be removed using oxygen, ozone, and AOP or enhanced Advanced Oxidation Processes for more effective purification.
advanced oxidation process AOP
Since 1893, in Europe, ozone has been used for water treatment.
- The use of ozone is increasing because, very often, several benefits are achieved at the same time.
- This ability to achieve multiple benefits has increased ozone’s role in current water treatment practices.
Ozone has proven effective for meeting several critical water treatment objectives, often more than one objective within a single application.
OZONE CAN BE EFFECTIVE AGAINST
- – Giardia Cryptosporidium
- – Bad Bacteria
- – Virus
DISINFECTION
- – Cryptosporidium
- – Giardia
- – Vegetative bacteria
DISINFECTION SUMMARY
Ozone is more effective than chlorine for Virus and Giardia disinfection.
Ozone can be more effective than UV for disinfection and inactivation of Cryptosporidium and is often used in conjunction with UV as part of advanced oxidation wastewater solutions.
DISINFECTION BY-PRODUCT
REDUCTION
- – TTHMs,
- – HAA5
- – Bromate
OZONE AS A PRIMARY DISINFECTANT
- Trihalomethanes (THM)
- Haloacetic Acids (HAA)
CHLORINE AS A PRIMARY DISINFECTANT
- – Bromate
- – Formaldehyde
- – Aldehydes
OXIDATION IN WATER TREATMENT
- Inorganics (Fe, Mn, S2 )
- Organics (T/O, color)
Inorganics:
- Iron and Manganese
- Hydrogen sulphide
Organics:
- MIB/Geosmins (T&O)
- Pesticides
- Colour
Other trace organics:
- Algal Toxins
- EDCs
- PhACs
OXIDATION:
Advanced Oxidation Process (AOP)
Involves the production of OH radicals operating near ambient pressure and temperature.
Ozone-based AOPs are the most common and efficient ones.
Benefits of Ozone Oxidation of Sulfide, Iron and Manganese
Alternatives to Ozone Oxidation of Sulfide, Iron and Manganese:
- Aeration
- Chlorine Oxidation
- Permanganate Oxidation
Ozone Oxidation is a fast, effective, and reliable process.
2Fe2+ + O3 + 5H2O——> 2Fe(OH)3 + O2 + 4H+
About 0.43 mg of O3 per mg of Fe(II)
Mn2+ + O3 + H2O——> MnO2 + O2 + 2H+
About 0.88 mg of O3 per mg of Mn(II)
Sulfide Ion Oxidation
Ozone Oxidation
S2- + 3O3 ——> SO 2- + 3O
3 3 2
SO 2- + O —–> SO 2- + O
Overall Reaction
S2- + 4O3 —–> SO 2- + 4O
3 4 2
Sulfide Ion Oxidation
Sulphide is readily oxidised by ozone to form sulfate at a sufficient dose
The theoretical O3 to H2S ratio is 3:1 mg/L.
The typical operating dose will be higher to maintain detectable ozone residuals.
This process, often used in advanced oxidation treatment, is highly efficient. Ozone and sulfide reactions are fast; a typical contactor time can be less than 10 minutes.
Colour In Drinking Water
- Aesthetically unattractive
- Often linked to the presence of fulvic or humic acids
- Chlorination leads to high TTHMs
Colour can be removed by pre-ozonation, intermediate ozonation, or both.
Ozone followed by GAC filtration is typically the most effective method.
Colour decrease of 10 units per 1 mg/L of ozone dose, per several studies
Summary of Odorant Oxidation
Ozone is the most reliable tool for mitigating drinking water Taste and odour problems; it is suitable for frequent and long-duration episodes.
- Highest Geosmin, MIB removal capability when compared to carbon adsorption or other oxidants
- Peroxide addition may enhance the removal
- Fast reaction – short (5 to 10 minutes) contact time can be used
TRACE CONTAMINANTS
Algal Toxins
Microcystin-LR:
A Common Algal Toxin
- Microcystin-LR is one of the more common toxins, and it is highly hepatotoxic (affects the liver).
- World Health Organization established one µg/L guideline
AWWARF survey (1996-98): 45 utilities from U.S. and Canada.
Sampling during water algae blooms (cyanobacteria cell counts ≥ 2,000 cells/mL).
677 samples, 80% positive for microcystin. 4.3% positive samples also > one µg/L.
Two finished water samples > 1 µg/L.
Advanced oxidation processing is increasingly used to break down such persistent algal toxins.
TRACE CONTAMINANTS
- Endocrine Disruptors (EDCs)
- Pharmaceuticals Personal Care Products
Emerging Contaminants
- Global Organic Contaminants
- Pharmaceuticals and Personal Care Products
- Endocrine Modulating Chemicals
- Nanoparticles
- Industrial Chemicals (new and recently recognised)
- Biological Metabolites and Toxins
IMPROVED FILTER PERFORMANCE
- Turbidity
- Particle Counts
- Bio-Stability
Microflocculation
Pre-ozonation application or before the flocculation stage.
- Improved Floc/Clarification & Filtration
- TOC Reduction
- Dosage Influenced by pH, TOC
Other Applications
- Microflocculation
- Integrated Use of Ozone
- Ozone and UV
- Ozone and BAC
SUMMARY
Ozone has proven effective for meeting several critical water treatment objectives, often more than one objective within a single application through advanced oxidation methods.
As our nation’s drinking water resources become increasingly compromised, ozone’s solid oxidative power will remain an important tool for the waterworks industry.
