Research on the treatment of seafood wastewater by electrocoagulation method combined with USBF

CAN THO UNIVERSITY SOCIALIST REPUBLIC OF VIETNAM

FACULTY OF ENVIRONMENT & TECHNOLOGY Independence - Freedom - Happiness

DEPARTMENT OF ENVIRONMENTAL ENGINEERING

Can Tho, August 16, 2010

GRADUATION THESIS OUTLINE

School year: 2010 - 2011

1. Project title: " Research on the treatment of aquatic wastewater by electrocoagulation method combined with USBF tank"

2. Student: NGUYEN NGOC ANH Student ID: 1070933

NGUYEN MINH TUNG Student ID: 1070984

Class: Environmental Engineering Course 33

3. Instructors: LE HOANG VIET & HUYNH LONG TOAN

4. Problem statement:

Our country is on the path of integration and development, joining the World Trade Organization (WTO) is both an opportunity and a challenge for the country's economy. Since September 2008, the world economy has been in crisis and this has greatly affected our country's economy [1]. The economic growth rate decreased significantly in 2008. Specifically, GDP in 2008 increased by 5.5%, much lower than GDP in 2007 which increased by 8.44% [2; 3; 4]. Faced with that situation, our government has had a policy to revive the economy with economic stimulus packages worth a total of about 8.0 billion USD [5]. This support from the government along with the efforts of businesses has led to very positive signs of recovery in our country's economy in 2009 and 2010. All sectors achieved higher growth rates than the same period last year. In particular, GDP in the first 6 months of 2010 increased by about 6 - 6.1% [6].

Industries such as: oil and gas exploitation, coal mining, textiles, rice export, seafood export, etc. are the industries that earn the most foreign currency for our country in the first 6 months of 2010. Specifically: oil and gas export reached 79.9 million USD, coal export reached 1.8 billion USD (first 4 months of 2010), textile export reached 4.65 billion USD, rice export reached 1.396 billion USD, seafood export reached 1.8 billion USD. Besides, the industries

Industry, handicrafts, trade and services also contribute significantly to the recovery of the economy [7; 8; 9; 10; 11].

Along with the economic recovery, factories and enterprises everywhere have resumed normal operations after a period of limited operation during the crisis and are increasingly expanding in scale. This is a good sign for the economy, but in return, our polluted environment will be at risk of becoming more and more seriously polluted. In particular, the surface water environment is very susceptible to pollution due to untreated wastewater from industries or wastewater that is treated but does not meet the regulations in the QCVN system (specifically QCVN 24: 2009/BTNMT).

Among the types of wastewater, wastewater from seafood processing factories is one of the types with the highest potential to pollute surface water sources. Because this type of wastewater contains high levels of organic matter ( Lam Minh Triet - Nguyen Thanh Hung - Nguyen Phuoc Dan, 2006) . Besides, among all economic regions of our country, the Mekong Delta region is the region with the highest seafood export output in our country. In the first 6 months of 2010 alone, this region contributed more than 530 million USD to the total seafood export value of the whole country [12].

However, in recent years, the export of tra and basa fillets from the Mekong Delta has often been sued by US companies for dumping and this product has been continuously subject to "anti-dumping tax" in this market. According to Mr. Nguyen Viet Thang, Chairman of the Vietnam Fisheries Association, "This decision of the US has greatly affected tra and basa farmers in the Mekong Delta" [13]. Faced with this problem, it is very difficult for small and medium-sized seafood processing companies and factories in the Mekong Delta to build and operate a technically correct wastewater treatment system. Because their profits are very unstable and depend heavily on the US market. Meanwhile, large-scale companies have the ability to build complete wastewater treatment systems, but they constantly expand their scale or increase their operating capacity, so these treatment systems are always overloaded.

Besides, the processing of tra and basa fish fillets for export in the Mekong Delta region is often seasonal and according to orders. During the season, due to

Due to the surplus of raw materials, most factories have to operate at full capacity. This causes the wastewater treatment systems of companies during this period to be overloaded, leading to the quality of the output wastewater not meeting QCVN (specifically QCVN 11: 2008/BTNMT). During the season of raw material shortage (off-season), factories have to operate at a low level, unstable or have to use other raw materials to produce other products. This has greatly affected the efficiency of the wastewater treatment system. Because the wastewater treatment systems of seafood factories often apply biological methods, and the unstable operation of factories like that means the amount of wastewater discharged daily is unstable in both flow and quality. Therefore, this situation has greatly affected the ability of microorganisms to function in the system, leading to the quality of the output wastewater not meeting QCVN 11: 2008/BTNMT.

With the problems of companies, factories and the current status of wastewater treatment systems, the risk of surface water sources in the Mekong Delta being polluted by seafood wastewater is very high. In addition, the problem of managing and treating seafood wastewater in the Mekong Delta is extremely urgent but there is currently no radical solution.

Therefore, what needs to be done immediately at this time is to conduct research and find a new technology for treating aquatic wastewater that can both meet the economic situation of enterprises and still ensure the quality of the output water of the system. In addition, there is also a need for methods to renovate or increase the capacity of old systems or overloaded systems.

Meanwhile, in Vietnam, USBF technology has appeared with many advantages in wastewater treatment. However, this technology has only been widely applied to domestic wastewater treatment such as: Novotel Phan Thiet Hotel - Binh Thuan, Aquaba Mui Ne Resort - Binh Thuan, An Vien Eco-Tourism Area - Nha Trang, ... The specific treatment efficiency of some indicators is as follows: SS 85%; COD 91%; BOD 5 91%; N 84%; and P 80% (Nguyen Han Mong Du, 2006).

USBF technology is an improvement of the classical activated sludge process. This technology combines three processes: anoxic, aerobic and sedimentation in one wastewater treatment unit. This

is the difference with the classical activated sludge treatment system, which often separates the above three processes, so the processing speed and efficiency are not high. With this combination, when using the USBF tank, it will save costs for the construction and operation of the system. Therefore, studying the application of this technology to treat aquatic wastewater is completely appropriate. In addition, to reduce the load on the USBF tank, the electrochemical flocculation tank is a very promising choice. The electrochemical flocculation tank is a technology that combines the advantages of three methods: electrolytic flocculation, coagulation - flocculation and chemical electrolysis (Hold, Barton and Mitchell, 2004) . Because it uses direct current and metals (aluminum and iron) as the electrodes, there is no need to spend money on chemicals to operate this tank.

In addition, the floc will be added to the aerobic compartment of the USBF tank. This will increase the density of microorganisms in the aerobic compartment. Then the quality of the effluent will be improved and the volume of the USBF tank will be significantly reduced.

With the current problems of companies, factories and wastewater treatment systems. The system combining electrochemical flocculation tank and USBF promises to solve the above problem. That is the reason why the topic " Research on the treatment of aquatic wastewater by electrochemical flocculation method combined with USBF tank" has been carried out by us.

5. Objectives of the topic:

Find out the best operating parameters for electrochemical flocculation tank system combined with USBF tank without flocculation carrier and electrochemical flocculation tank system combined with USBF tank with flocculation carrier in the treatment of aquaculture wastewater.

6. Location and time of implementation:

 Laboratory of Environmental Engineering Department - Faculty of Environment & Natural Resources - Can Tho University.

 Time: Semester I, 2010 - 2011.

7. Implementation contents:

Find out the most suitable design and operating parameters for the electrochemical coagulation tank such as: distance between two electrodes, surface contact area of electrode with wastewater, suitable retention time, etc.

Determine the correlation between the treatment efficiency of the electrochemical coagulation tank and the voltage and current intensity.

Determine the corrosion resistance of the electrodes and how much power is consumed.

Determine the treatment efficiency of the USBF tank after the electrochemical flocculation tank has reduced the load on the input wastewater at different retention times and find the most suitable retention time.

Comparison of performance and retention time of USBF tanks with and without flocs in the aerobic compartment. Use of locally available floc materials to reduce operating costs.

8. Project implementation method:

 Take samples of aquaculture wastewater to analyze some initial indicators such as: BOD5 , COD, SS, pH, total N, total P ,...

 Conduct experiments on models: electrochemical flocculation tank model and tank model

USBF .

+ For electrochemical flocculation tanks, many experiments will be conducted on the flocculation tank.

Incomplete electrochemical capacitor to determine some parameters to design a complete electrochemical flocculation tank such as: distance between 2 electrodes, distance between 2 electrodes and tank wall, current intensity and voltage,... In addition, experiments will be conducted to find out the operating parameters of the complete electrochemical flocculation tank such as: retention time, contact area between electrodes and wastewater,...

+ For USBF tank, the output wastewater of the complete electrochemical flocculation tank is used as input wastewater. This tank operates under two conditions: with and without flocculation.

 Take wastewater samples from the complete electrochemical flocculation tank, USBF tank with and without flocculation rack to re-analyze the following indicators: BOD5 , COD, SS, pH, total N , total P ,...

 Synthesize, analyze and summarize experimental results.

 Compare, evaluate the processing efficiency of the models and draw conclusions.

Parameters such as pH, DO, BOD5 , SS,... are analyzed according to the instructions of Standard Methods For Examination of the Water of Wastewater (APHA, 1995) using laboratory equipment of the Department of Environmental Engineering - Faculty of Environment and Natural Resources - Can Tho University.

9. Experimental support equipment:

Transformer.

Electrochemical coagulation tank

Electrochemical flocculation tank and USBF (Upflow Sludge Blanket Filtration) tank .

Device for measuring current and voltage.

The electrodes.

10. Implementation plan and progress:

The thesis completion time is from August 1, 2010 to November 14, 2010, including 15 weeks, distributed as follows:

Work Week