Necessary needs and development situation of mango processing industry
The Mekong Delta (MD) is one of the places with the largest mango growing area in the country. In the past, mangoes were sold fresh, unprocessed and consumed domestically, so processed mango products were not much, with low added value. However, due to consumer tastes and the difficulty of preserving mangoes in fresh conditions and having a short storage time, processing mangoes for export to create higher added value, and processed products going to many distant markets such as Europe and America is increasingly becoming an inevitable trend. The processed products are quite diverse such as: dried mango, mango powder, and mango milk, etc., which are very popular in the market and this is an investment and business opportunity for many enterprises in the MD.
Along with the development of the mango production and processing industry, some processing factories have not really focused on investing in wastewater treatment systems or have not treated them thoroughly. This is affecting the receiving source and the increasingly polluted environment, affecting the aquatic ecosystem as well as the living environment of the surrounding people. Therefore, designing a wastewater treatment system in mango processing factories is a necessary task today. This is also the topic that Nanoen wants to talk about through this article: "Wastewater treatment in the food processing industry - mango production".
Mango processing and preliminary processing industry
Sources of mango processing wastewater
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Mango processing wastewater mainly originates from the following sources:
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The process of soaking, washing, cutting and peeling mangoes.
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The process of blanching mangoes;
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The process of soaking in sugar and preservatives;
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In addition, a certain amount of wastewater comes from the process of cleaning the factory floor, washing machinery and equipment, and domestic wastewater of workers.
Mango cutting and peeling process
Characteristics of mango processing wastewater
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Mango processing wastewater contains a lot of organic matter, suspended solids and inorganic chemicals used in the washing, soaking and preservation processes;
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Wastewater from washing equipment and machinery contains a lot of suspended solids, surfactants, cleaning chemicals, etc.
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Wastewater from cleaning and cleaning factory floors;
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Wastewater from workers' daily activities contains a lot of suspended solids, organic matter and some types of bacteria, etc.
Difficulty level of Mango wastewater treatment and pollution level:
Because mango processing wastewater has a high content of organic and inorganic pollutants, when discharged into water sources, it will directly affect the aquatic ecosystem:
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Suspended solids (sand from the peeling and washing process, the mango crushing process) can cause sludge sedimentation and create anaerobic conditions, reducing the amount of dissolved oxygen in the water, creating a foul odor;
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Especially wastewater in the process of drying mangoes. The wastewater has a very high sugar content, if analyzed, the COD index is more than 10,000mg/L;
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The sugar used to soak mangoes when discharged will be fermented. Bacteria quickly convert sugar into volatile acids. Therefore, the smell is very strong;
Mango processing wastewater generated
(recorded at Nanoen wastewater treatment plant)
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BOD, COD concentrations in mango processing wastewater are very high, however, the nutrient content is very low, so when treating wastewater, it is necessary to add a lot of N, P for microorganisms;
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High organic matter content in oxygen-deficient conditions in water will cause anaerobic decomposition to produce toxic products such as H2S, mercaptan causing foul odors, making the water black. Causes turbidity in water because wastewater has a lot of sediment and suspended solids.
Impact of wastewater when discharged into the environment:
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The decomposition time of organic substances is prolonged, generating many toxic and foul-smelling substances, leading to the water source losing its self-cleaning ability. At the same time, water sources with high organic loads can "die" due to lack of dissolved oxygen in the water.
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Impact on people's lives: Mango processing wastewater needs to be treated before being discharged into the environment to avoid polluting the receiving source, affecting aquatic life as well as the quality of the human living environment.
The main technology applied to mango wastewater treatment is:
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Mechanical treatment stage:
Wastewater contains many large solids such as mango peels, packaging, mango flesh, etc. mixed with the discharged water source, so it is necessary to have a trash rack to remove them;
Input wastewater contains a lot of sediment and suspended solids, so there should be an initial sedimentation stage using a settling tank or other treatment technology to reduce the concentration of these components before entering the next stage.
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Physicochemical treatment stage:
Mango wastewater contains a high level of COD that is difficult to biodegrade and a large amount of dissolved COD (due to the use of chemicals, mango latex, etc.), so it is necessary to have technology to ensure the removal of these components before entering the biological stage such as: electrochemical coagulation, electrochemical flotation, advanced oxidation tank (Fenton) ....
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Biological treatment stage:
Mango wastewater contains many high BOD components, SS needs biological treatment stage to remove them, applicable technologies such as: anaerobic tank with buffer layer, RBC (rotating biological cage), MBBR, activated sludge tank,...
IFAS and RBC biological treatment tank (Nanoen applied)
Proposed process for treating wastewater from mango processing
Illustrated wastewater treatment process (Nanoen)
Technology description
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Collection tank:
The collection tank has the function of collecting production wastewater, wastewater flows through coarse trash racks to remove large solids that can affect equipment and machinery of the following treatment items.
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Physical chemistry 1:
The fast reaction tube or flocculation tank has the function of adhering flocs thanks to the coagulant. The coagulant is injected into the pipe, when the wastewater passes through, it will come into contact with the coagulant and cause the coagulation process to take place.
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Physical and chemical settling tank:
The physicochemical settling tank has the function of removing flocs in the fast reaction tube thanks to the gravity method.
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Equalization tank:
The equalization tank has the task of regulating the flow as well as the concentration of wastewater generated, ensuring the system operates stably and continuously, avoiding the phenomenon of overloading or underloading the treatment system.
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Advanced oxidation tank:
OH* radicals are strong oxidizing radicals that can oxidize pollutants in wastewater, shortening difficult-to-biodegrade substances into easily biodegradable substances.
Wastewater is settled to remove flocs, then flows through the biological tank.
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Biological tank:
When the organic matter content is lower than the bacteria's needs, bacteria will undergo intracellular respiration or self-oxidation using their own protoplasm as raw materials.
Next, the wastewater will flow to the biological settling tank.
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Biological sludge settling tank:
The biomass created after the biological treatment process will be removed in the biological settling tank, the water after settling will flow into the water collection trough and be passed through the disinfection device to remove pathogenic bacteria.
Next, the wastewater will flow to the disinfection device.
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Disinfection tank:
This is the final treatment stage. Chlorine is added to the disinfection tank to kill pathogenic bacteria remaining in the wastewater.
The output wastewater meets column B QCVN 40:2011/BTNMT.
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Sludge treatment:
Physicochemical sludge is pumped to the physicochemical sludge tank.
Biological sludge is pumped to the biological sludge tank.
Segregation of sludge for proper treatment.
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