Alternative Waste water treatment technology- Advanced Oxidation Process

1. TECHNICAL PAPER
ON
“Recent Trends in Chemical Engg.”
( Sonophotocatalytic Degradation of Waste Water )
PRESENTED BY
Mr. Tejas D. Deshpande
B.E. (Chemical)
TATYASAHEB KORE INSTITUTE OF ENGG. AND TECHNOLOGY,
WARANANAGAR.

2. Generators of Waste Water
Domestic Wastewater
 Bathing
 Washing Clothes, Utensils, Vehicles etc.
 Sanitation waste
 Landfill leachate Effluents
 Commercial
Industrial Waste Water
 Chemical
 Petroleum and Refining
 Food Processing
 Pharmaceutical
 Pulp and paper
 Textile
 Dye processing

3. Current Waste Water Treatments
Unit operations and processes that have been employed to waste water treatments are
divided into 3 types according to various levels of treatment as :
1. Physical - Primary methods- Physical or Physio-chemical unit Operations
e.g. filtration, adsorption, air flotation, flocculation and sedimentation
2. Biological - Secondary - Biological Operations.
e.g. aerobic, anaerobic and activated sludge
3. Chemical – Tertiary- Advanced Processes evolving Chemical Change
e.g. Thermal oxidation (Combustion), Chemical oxidation, Ion exchange, Chemical
Precipitation

4. Drawbacks
 Incomplete elimination of Toxic & Non-biodegradable organic pollutants
 Need disposal of secondary waste materials generated in the process
 Can Reduce BODs but Can not reduce CODs at desirable extent
 Adsorption and Coagulation - NOT useful to treat harmful infectants present in the waste water
 Sedimentation, filtration, Membrane technology - Expensive and Generate toxic secondary
pollutants
 Chlorination generates Mutagenic and Carcinogenic by-products
Need to test and set up the emerging alternative technologies to
overcome the inconveniences of conventional treatment methods

5. Advanced Oxidation Processes: ( AOPs )
 Groups of technologies that lead to hydroxyl radical (.OH) generation
 .OH Radicals- Extremely unstable and reactive, High oxidation potential
 Attack organic molecules & make New oxidized intermediates with lower
molecular weight or in case of complete mineralization CO2 and water
 AOP - Powerful and efficient treatment methods for degrading recalcitrant
materials or mineralizing stable, inhibitory, or toxic contaminants
 Increasingly gaining popularity - Potential of converting harmful organic pollutants
into innocuous compounds such as CO2 and H2O

6. Fig. Mechanism of the oxidation of benzene by Hydroxyl Radicals

7. Types of AOPs
 AOPs based on Ozone
 AOPs based on Hydrogen Peroxide
 Fenton Oxidation process
 Photolysis
 Photo catalysis
 Sonolysis
 Sonochemical
 Sonoelectrochemical
 Electrochemical
 Sonophotocatalysis

8. Sonophotocatalysis
(Sono + Photo + Catalyst)
Combination of two advanced oxidation processes i.e. Sonication and photo catalysis
 Basic reaction mechanism for both Ultrasound initiated degradation and Photo catalytic
oxidation- Generation of free radicals and subsequent attack by these on the pollutant
organic species
In Photo catalytic oxidation, efficiency reduces due to blocking of the catalyst activated
sites
 Turbulence induced by Cavitation phenomena under the action of turbulence generated
by acoustic streaming – Elimination the drawbacks associated with photo catalytic
oxidation
More number of free radicals are generated due to combination of 2 modes ; thereby
increases the rates of reaction

9. Reaction Mechanism
Reactions involved in Photo catalysis:
TiO2 + hv → TiO2 (e- + h+)
TiO2 (h+) + H2O → TiO2 + H+ + HO-
TiO2 (h+) + OH- → TiO2 + HO•
TiO2 (e-) + O2 → TiO2 + •O2
H2O2 + hv → 2HO*
Reaction involved in Sonolysis:
H2O + ))))→ H* + HO*
H2O + ))))) → ½ H2 + ½ H2O2
H2O2 + H* → H2O + HO*

10. Instruments for Sonophotocatalysis
 pH meter
COD digester
Spectrophotometer
Ultrasonic bath or probe
UV source such as Lamp
Catalyst such as Zno,TiO2
Magnetic Stirrer
Magnetic Stirrer pH meter
UV Lamp

11. Parameters that must be looked upon
 pH = Acidic (2.5 - 5.5)
 UV wavelength = 200 to 400 nm
 US frequency = 20 kHz <
 Type and Amount of catalyst = Zno,TiO2,etc.
 Size of catalyst particles
 Initial Concentration of waste water

12. Case Study
SONOPHOTOCATALYTIC TREATMENT OF PHARMACEUTICAL WASTEWATER
( Department of Bio-Technology and Environmental Sciences, Thapar University ,Patiala )
Sr.No Parameter Prevailing Range
(mg/ml)
1 pH 3.75
2 COD 32
3 BOD 12.8
4 TS 25.2
5 TDS 23.9
6 TSS 1.3
7 Sulphate 3.716
8 Chloride 7.526
WASTE WATER CHARACTERISTICS

13.  Sample taken = 1000 ml
 pH = 4.0
 Catalyst = TiO2
 Amount of TiO2 catalyst = 1 - 7 gm.
 Oxidant = H2O2 (works as promoter)
 Amount of Oxidant H2O2 = 2.3-30 ml
 Residence Time = 2 Hrs.
 Wavelength of UV lamp = 280 nm
 Frequency of Ultrasound = 42 KHz
 Size of TiO2 Catalyst = 47.1-67.5 nm.
Methodology

14. Sr.No Parameter Prevailing Range
(mg/ml)
After Sonophotocatalytic
Treatment (mg/ml)
Percentage
Degradation
1 pH 3.75 7.1 -
2 COD 32 0.32 99%
3 BOD 12.8 0.15 98.8%
4 TS 25.2 0.00 100%
5 TDS 23.9 0.102 99.5%
6 TSS 1.3 0.00 100%
7 Sulphate 3.716 0.232 93.7%
8 Chloride 7.526 0.092 98.7%
Final Characteristics

15. Results show that-
 Efficient and Environmental friendly technique
 Almost 95% degradation of recalcitrant organic pollutants
 Wastewater compounds are degraded rather than concentrated or transferred into a
different phase - No need of disposal of any materials
 Increases the chances for the reuse of wastewater
So, we can say that Sonophotocatalysis has a good
capability to treat the waste water of various industries
Results & Discussions

16. Advantages
 More number of free radicals will be available for the reaction thereby increasing the rates of
reaction
Rate constants of the combined process are greater than the sum of the rate constants of the
individual processes
Wastewater compounds are degraded rather than concentrated or transferred into a different
phase - there is no need to dispose of the treated materials
Complete degradation of organics into CO2 and H2O in a relatively short period of time, i.e.do
not introduce any new hazardous substances into the water.
Superior over other conventional methods of wastewater treatments, in the presence of bio -
recalcitrant compounds
It can effectively degrade phenols, all halides, inorganic chemicals, dyes, herbicides, pesticides

17. Current Shortcomings
1. Removal rate of SPC is relatively high while the Operating cost is relatively
expensive due to the use of reagents and irradiation sources
2. Some techniques require pre-treatment of wastewater to ensure reliable
performance, which could be potentially costlier
3. Given the potential costs, SPC may not individually handle a large amount of
wastewater; instead, it should be deployed in the final stage after primary and
secondary treatment have successfully removed a large proportion of
contaminants

18.  SPC wastewater treatments hardly feasible for the industry scale up because:
- Poor attention from most of the scientific community towards energy intensification in SPC
- Early stage of development
- Lack of standard strategies for the design of large and efficient reactors.
 Still many research needs in the field of SPC treatment for wastewater ,to provide:
– Better understanding of the mechanisms of SPC
– Measurements of the efficiency of process under controlled experimental conditions
– Realistic evaluations of the relative costs of candidate processes versus other treatment processes
 Greater effort is needed to fully understand the difficulties in the degradation process:
- To reduce the cost of waste treatment
- To improve existing and future applications
Current Scenario

19. Conclusion
 Sonophotocatalysis has provided promising results from a technical and environmental
point of views while the economics aspects are still being optimized.
 Future dimensions of domain of SPC depending on consideration of optimization
following parameters:
1) Operating time
2) Operating cost
 Research on AOPs will surely bridge a gap between innovation, invention & its
application towards society.

20. References-
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