1.5.3 . Studies on wastewater treatment with ozone in Vietnam
Wastewater treatment in Vietnam has only received attention in recent years, so there is not much research on the technology . Systems built to treat wastewater are mainly formed due to the social urgency of the locality where the landfill is located . Due to the local nature , wastewater treatment technology is
also has high specificity determined by the technology implementing unit, technological capacity and feasibility conditions of that locality [5].
The problem of leachate treatment in our country has not been thoroughly solved because the technology relies mainly on biological decomposition processes. These processes are not strong enough to decompose the organic pollutants that are difficult to decompose and are not sustainable in leachate.
There are still many studies on ozone technology in leachate treatment in Vietnam.
limited. On the surface
scientific research
and technological development , until
now there is one
number of studies on wastewater treatment
deployment .
*. Studies on leachate treatment using biological technology:
To Thi Hai Yen and colleagues ( 2008) [15 ] have studied " recirculating water "
waste and microbial decomposition in sulfate environment in landfill technology
activities to help reduce environmental pollution caused by wastewater ; To Thi Hai Yen and
colleague
(2010) [16] with the project " Mechanism to accelerate the process of microbial decomposition "
" Leachate and waste management by changing the operating mode and chemical environment in landfills" has shown that when landfilling, domestic waste contains a large amount of lignin .
15.2% dry weight methane emissions are economically and environmentally unprofitable .
school . With work
Add more sulfate medium to create
condition
to divide
Solid organic components in waste are converted into liquid form in leachate, mineralizing the difficult-to - biodegrade organic components in leachate . In the environment
In the sulfate field , the system only really comes into play from the 95th day of the cycle .
landfill . In addition, the authors also showed that the circulation of leachate creates a stronger oxidation - reduction capacity for the microbial decomposition environment of organic matter in solid waste and inorganic and liquid organic matter .
Original
Hong Khanh ( 2007) [5] has conducted a comparative study of technologies in
and abroad on leachate treatment, on that basis the author has proposed treatment technology
water for all
buried on the plate
Hanoi city
From this research ,
The author proposes wastewater treatment technology for Nam Son landfill and its partners .
similar
The new water treatment plant uses advanced SBR technology ( which is the next generation of wastewater treatment technology ) .
solemn
but it can still be
continuous action
) and the final stage is oxidation by
Fenton.
* Studies on leachate treatment with ozone:
Tran Maṇ h Tri ́ (2007) [13] applied advanced oxidation processes (AOPs) to
Leachate treatment has been biologically treated at Go Cat leachate treatment plant . Author
Multi - use of Glueing – Complexing – Fenton – Perozon process to treat wastewater
biodegradation
anaerobic in UASB tank (COD 5,424 mg/l) in water treatment system
Go Cat leachate. Coagulation/Fenton process is used.
food
porch
by adding polyferic
sulfate (300 mg Fe 3+ /l) and after rapid stirring , add 500 mg H 2 O 2 /l and
stir
120 minutes . With this process , the effect
very high COD treatment rate ( achieved )
76%). After the process of Glueing – Complexing – Fenton, the leachate continues to be treated.
with Perozon has been treated
97% of organic matter in leachate.
Truong Quy Tung and colleagues (2009) [14] studied the treatment of leachate generated from Thuy Tien landfill - Thua Thien Hue using UV/Fenton agent. The leachate has a BOD5 /COD ratio of 0.16 ± 0.2. The author treated this leachate with Fenton agent with the support of UV lamp (200 - 275 nm, 40W) arranged to be submerged in the
in the reactor to maximize the energy utilization of the lamp. The results showed that, the
This process can remove 71% of COD and 90% of the color of leachate at pH ~ 3, H 2 O 2 concentration of 125 mg/l, Fe 2+ concentration of 50 mg / l , after a reaction time of 2 hours. In addition, the biodegradability of leachate after treatment has increased significantly, the ratio
BOD5 /COD ratio increased from 0.15 to 0.46.
Nguyen Van Phuoc and engineers ( 2007 ) [ 8 ] have studied the treatment of wastewater .
by 3 - step Fenton process (inlet COD 665 mg /l, H 2 O 2750 mg/l, total iron
of three stages is 3,750 mg/l, reaction time 7 minutes ) then COD treatment efficiency reaches 87.5% . The authors have determined that the catalytic technology of Fenton reaction according to the steps used
Use H 2 O 2 thoroughly to create the root of leachate treatment time.
OH , thereby improving COD treatment efficiency, shortening
Hoang Ngoc Minh (2012) [7] studied the treatment of wastewater discharged from Nam Son - Soc Son solid waste landfill by single Ozone and Perozon process, using O 3 source with generator capacity of 4.5g O 3 / h , H 2 O 2 concentration is 1,000 -3,000 mg / l. With wastewater having COD and input color of 455 mg / l and 397 Pt - Co , respectively ,
After 60 minutes of treatment with Perozon, the effect
The respective yields were 41% and 58%. According to the study
According to the author's research , the optimal pH for the ozonation process of wastewater is about 8 - 9.5 . Experimental results show that , for fresh , undecomposed wastewater , COD : 1,500 -
2,500 mg/l, after 120 minutes of treatment with single ozone, the COD treatment efficiency was 11 - 15 %, color: 78 - 87% . For deeply decomposed leachate ( reactive leachate ) , 36 % COD and 9 % color were treated . The authors also studied the effect of catalysts on
understand
The results of both Perozon and Catazon processes in wastewater treatment .
results show, effective
COD treatment of effluent ( old ) of catalytic catazone process
Al 2 (SO 4 ) 3 is 1.27 - 1.31 times higher than the Perozon process with the Al 2 (SO 4 ) 3 concentration being
1,000 mg/l and 2,200 mg/l. For FeSO 4 catalyst, COD treatment efficiency is higher than that of FeSO 4 catalyst .
Perozon process from 1.47 - 1.68 times. Color removal efficiency of catazon process with
Aluminum and iron catalysts are both 2.3 - 2.8 times higher than Perozon process and the catalyst
iron
more than aluminum in terms of mass .
Hoang Thi Thu Hien (2012) [3] used UV/Ozone to treat leachate. Experimental results in laboratory conditions treated leachate from Nam Son landfill. From the experimental results of leachate treatment after coagulation, the author determined that the optimal conditions were achieved at pH = 7.5 and reaction time was 100 minutes; COD treatment efficiency and leachate color were 26% and 64% respectively with single Ozone system and 35%, 82% with UV/O 3 system .
Du Thi Huyen Thanh (2012) [9] combined Perozon and UV to treat leachate.
waste. From the results of leachate treatment after the coagulation stage, the author has determined the best conditions for the treatment process for both the O 3 /H 2 O 2 and O 3 /H 2 O 2 /UV systems as: pH = 7.5; molar ratio H 2 O 2 /O 3 = 0.7; reaction time is 80 minutes. With the best conditions
The color and COD removal efficiencies achieved were 40% and 75% (O 3 /H 2 O 2 system); 90% and 64% (O 3 /H 2 O 2 /UV system ).
*. Core
Review of wastewater treatment research in Vietnam :
In general, studies on leachate treatment in our country mainly focus on biological technology, and there are not many studies on ozone treatment. However,
Recently , there have been some studies applying advanced oxidation processes such as
Fenton , Ozone . Most studies have treated wastewater in multiple stages .
such as: Self-adhesive – Complexation – Fenton – Perozon; multi-step Fenton; UV/Fenton;
UV/Ozone or UV/Perozone; Ozone combination
Fe 2+ catalyst or
Al 3+ , with time
The treatment time is 60 minutes or 120 minutes. The research results show that the leachate treatment process consumes a lot of ozone and the efficiency is still not high except for the process .
combined ozone treatment
Fe 2+ or
Al 3+ . Thus, in our country, initially there have been
Research on the use of catalysts in the treatment of leachate with ozone.
1.5.4. Conclusion on the research status of leachate treatment with ozone and research orientation in the thesis
In the world, O 3 has been widely used in leachate treatment to remove organic pollutants. From research on the application of single ozone, Perozone, ozone combined with UV, Ozone/Fenton, Ozone/activated carbon to ozone catalysts Fe 2+ , Al 3+ , S 2 O 8 2- and TiO 2 /O 3. In Vietnam, the application of ozone to leachate treatment is also carried out, including treatment with single ozone, Perozone, ozone catalyst Fe 2+ , Al 3+ .
Ozonation processes in leachate treatment can be improved by increasing the surface contact area so that ozone can dissolve better in the leachate. The contact area can be increased if the reaction column in the single ozone or Perozone system contains a buffer material. If the contact area is increased, it will increase the ability of ozone to react with leachate by direct and indirect pathways and will increase the efficiency of oxidation of organic substances in leachate by ozone. The type of buffer material also needs to be durable, not oxidized by ozone or hydroxyl radicals ( OH ), non-corrosive... In the world as well as in Vietnam, cushioning materials have been widely used in the treatment of exhaust gas and wastewater, especially biological treatment processes to increase treatment efficiency. Cushioning materials have the ability to increase the contact area
contact of ozone and wastewater. However, these materials have not been applied in water or wastewater treatment studies in the ozone oxidation process. Therefore, in this thesis, high-strength packing materials are applied to improve the efficiency of treating organic substances in leachate.
Some metal oxides iron, copper, nickel, magnesium, manganese, silicon, aluminum, zinc,
Titanium , cobalt ... have been studied and used as catalysts for the ozone process .
Ozone ( O3 ) is used to treat organic compounds that are difficult to decompose in water .
waste . Most of the contacts are
summary
combine
with one
or
many other metal oxides
or
combine
with granular activated carbon (GAC). Research on oxalic acid treatment by
Ozone with TiO 2 /Al 2 O 3 [30]; using heterogeneous catalysts Fe /MgO, Fe/Al 2 O 3 , Fe/SiO 2 and Fe/ZrO 2 to catalyze the ozonation of humic acids [59 ] ; integrating
Ozone and MgO nanocrystals for phenol treatment in saline wastewater
[69];
Research on the treatment of organic compounds by ozone with CeO 2 catalyst[ 74 ]; using CeO 2 /AC catalyst to treat organic substances such as oxalic acid, aniline [45]. Quinones and engineers ( 2013) [79], using TiFeC ( titanium magnetite carbon) as photocatalyst for ozonation process to treat metopronol tartrate ( MPT ); Sable and engineers ( 2014 )
[89] studied the ozone treatment of clofibric acid ( CFA) with Mg /Al hydrotancite (HT) containing Fe , Cu and Ni .
Many studies have focused on the use of Al 2 O 3with the support of metal oxides
another for the ozone reaction. Recently, a
Some authors such as Asgari et al . (2013) [24 ]
pyrolyzed marine bone as a catalyst for ozone decomposition reaction
to increase efficiency
through root production
OH
flexible in phase ; or Ma and the engineer
(2014 ) [67] activated nickel ash and sawdust as catalysts for ozone .
Most studies used manganese (in the form of MnO 2 ) as a catalyst for
ozone reactions are combined
with aluminum oxide ( Al 2 O 3 ) or GAC as catalyst
Ozonation process for the treatment of certain organic substances . Andreozzi et al . (1996)
[23] MnO 2 is widely used .as a heterogeneous catalyst for the ozonation of oxalic acid. Einaga et al . (2004) [40 ] , treated benzene with ozone using MnO 2 / Al 2 O 3 catalyst .
Jun et al . (2005) [ 60 ] studied the effect of pH on treatment efficiency .
nitrobenzene by ozone with MnO x /GAC catalyst . Alsheyab et al. (2007 )
[22 ] , comparative study of the effects of ozone and MnO 2 / O 3in wastewater treatment containing trihalomethanes ( THMs ), humic and fulvic acids . Rosal et al . (2010) [87] , studied the treatment of pesticides containing atrazine and linuron by ozone with MnO x / Al 2 O 3 reaction .and MnO x /SBA-15. Ichikawa et al . (2014) [56] , used a
number of metal catalysts ( Co 3 O 4 , Fe 2 O 3 , SnO 2 , Mn 3 O 4 , CuO, ZnO, NiO, MgO and
Al 2 O 3 ) in the treatment of ammonium by ozonation . Sun et al . (2014) [93], evaluated the effectiveness of MnO x / SBA - 15 for the treatment of oxalic acid by ozone .
Thus, metal oxides have been used as catalysts for the ozonation process in research to treat one or several specific types of organic pollutants in wastewater. However, studies on the application of metal oxides as catalysts in the treatment of leachate by the ozonation process are still limited.
Naturally derived metal oxide catalysts can be used as
catalyst for the oxidation of organic substances by ozone. Ozone combination (80
g / m 3 ) with three solid catalysts ( activated carbon (AC), expanded pearlite (EP) and titanium dioxide (TiO 2 ) ) to treat leachate from Jebel Chakir landfill (Tunisia) [95]. Vietnam has many common natural metal oxides produced from ores such as iron ore, copper ore or manganese ore... Therefore, natural metal oxides can be used as catalysts for the ozonation reaction to treat leachate, promising good results.
However, heterogeneous catalysts MnO 2 or heterogeneous catalysts containing many metal oxide radicals from natural manganese ores have not been studied for application as catalysts in the ozonation process. Natural manganese ores have been used in the treatment of water supply and wastewater.
Materials containing multiple metal oxide groups from manganese ore may have better catalytic effects than materials containing only one metal oxide group. Therefore, this type of material used as a catalytic material in the oxidation reaction of organic substances by ozone will greatly improve the efficiency of leachate treatment. The oxidation of organic substances by ozone with manganese ore catalyst may have a higher efficiency than the treatment by single ozone, perozone or ozone with a specific metal oxide catalyst. Moreover, catalytic materials from manganese ore are very available in nature and low cost, especially
is in Vietnam. For the above reasons, in this thesis, manganese ore is used as a heterogeneous catalyst for the Ozonation process in the treatment of organic substances in leachate. This type of material can improve the efficiency of treating organic substances in leachate by Ozone, Perozone. This is also the first study using manganese ore as a heterogeneous catalyst for the ozonation process of leachate.
CHAPTER 2. OBJECTS, SCOPE AND METHODS OF RESEARCH
2.1. OBJECTS AND SCOPE OF RESEARCH Research objects :
- Organic substances in leachate (assessed through parameters of color, COD, TOC and BOD5 ) .
Leachate is collected at the leachate collection ditch near the drain to the lake.
Nam Son - Soc Son solid waste treatment complex (Hanoi city).
Research scope :
- Research on the treatment of organic substances in leachate at laboratory scale.
The experiments were conducted at the Institute of Environmental Technology - Vietnam Academy of Science and Technology and the Institute of Environmental Science and Technology.
- Hanoi University of Science and Technology.
Table 2.1 Summary of leachate analysis results collected at Nam Son before treatment through experimental batches.
Table 2.1. Some characteristics of experimental leachate
Target
Unit | Value | |
pH | - | 7.87 – 8.52 |
Color temperature | Pt-Co | 2,025 – 6,060 |
COD | mg/l | 2,178 – 6,630 |
BOD 5 | mg/l | 601 – 2,332 |
BOD5 / COD | - | 0.27 – 0.35 |
TOC | mg/l | 855 – 2,145 |
Total nitrogen | mg/l | 724 – 1,806 |
NH 4 + | mg/l | 670 – 1,668 |
NO 3 - | mg/l | 4,304 – 14,360 |
NO 2 - | mg/l | 0.409 – 2.366 |
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