Sludge dehydrator in the treatment of seafood/fish processing wastewater and sludge

Possessing a strategic location on the South China Sea, with a coastline of 3,260 km (3,444 km, 33rd in the world according to The World Factbook). Vietnam claims 12 nautical miles of territorial sea, another 12 nautical miles of contiguous zone, 200 nautical miles of exclusive economic zone and finally continental shelf. The waters under the sovereignty and jurisdiction of Vietnam occupy an area of ​​about 1,000,000 km² of the East Sea. Along with a dense network of rivers and lakes, internal waters are favorable for fishing and aquaculture. This is one of the key economic sectors of Vietnam. Captured fishery output is about 4 million tons/year. Processed products are about 700-800 thousand tons. Accounting for 4-5% of GDP and 10% of the total export turnover of the country.

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Accompanying development opportunities are environmental challenges. Wastewater from the fisheries industry contains many pollutants that are harmful to the ecosystem and human health. Therefore, investing in treating wastewater and seafood sludge is a requirement for factories, businesses and processing establishments in the industry.

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Maritime sovereignty (exclusive economic zone and continental shelf) of the Socialist Republic of Vietnam

Overview of wastewater, seafood sludge

Stationary sources

Aquaculture, exploitation, and processing include preliminary processing, filleting, freezing fish, shrimp, crab, ..., and fishmeal production, ... with diverse input materials. The stages of water change in ponds, cages, sorting, cleaning, processing, and equipment cleaning will generate a huge amount of wastewater.

Solid waste generated includes shrimp shell heads, clam shells, squid skin/shells, squid and fish organs, etc., which have an unpleasant odor, especially when decomposed.

Environmental impact if wastewater is not treated

The characteristics of this type of wastewater are the high levels of dissolved organic matter, suspended compounds, and suspensions containing nitrogen, phosphorus, sulfur, etc. These substances, if discharged directly when decomposed, will significantly reduce the concentration of dissolved oxygen in the water, suffocating aquatic organisms in rivers and lakes. Making water lose its ability to self-clean, seriously polluting surface water, groundwater, and coastal areas.

Compounds rich in nitrogen and phosphorus, when discharged into rivers and lakes, increase the growth of algae, causing eutrophication. Kills aquatic organisms, including farmed species...

Suspended solids make the water turbid, limit light, and affect the photosynthesis of algae and algae. Suspended solids also accumulate in river beds, hindering the circulation of water and ships.

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Process of seafood processing and sources of wastewater generation

Physicochemical properties of seafood processing wastewater

  • 70–80% are organic compounds including proteins, amino acids, urea CON₂H₄, fats, and extremely difficult-to-process complexes.
  • 20-30% comprises sand, soil, salt, additives, and detergents
  • Nitrogen and Phosphorus: Aquatic wastewater contains outrageous amounts of N and P, especially phosphorus not only in the product's composition but also because of the addition of processing additives.
  • COD and BOD are very high, exceeding the standard many times.
  • Contains many types of bacteria, viruses, and larval eggs, helminths that cause disease. People who directly use contaminated water are at high risk of contracting dysentery, typhoid, polio, urinary tract infections, and acute diarrhea.
  • Ammonia: is extremely toxic to shrimp and fish, even in tiny concentrations. The lethal concentration ranged from 1.2 to 3 mg/l.
Targets Unit Concentration
Frozen shrimp Catfish Mixed frozen seafood QCVN 11:2018, Cột B
pH 6.5 – 9 6.5 – 7 5.5 – 9 5.5 – 9
Chất rắn lơ lửng (SS) mg/L 100 – 300 500 – 1200 50 – 194 100
COD mgO2/L 800 – 2000 800 – 2500 694 – 2070 80
BOD5 mgO2/L 500 – 1500 500 – 1500 391 – 1539 50
N Total mg/L 50 – 200 100 – 300 30 – 100
P total mg/L 10 – 120 50 – 100 3 – 50 60
Oil and grease mg/L 250 – 830 2.4 – 100 20

According to Vietnam Environment Administration 2009

Process of treating wastewater, seafood sludge

The current technology of wastewater and aquatic sludge treatment is very diverse and complex. Depending on the input materials and processing methods, the discharged wastewater has unique characteristics. In the final stage, most factories and factories used mud presses to treat sludge. This saves costs, takes up less area of traditional mud drying yards, and brings high efficiency.

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Flow chart of seafood wastewater treatment process

1. Wastewater mechanical treatment stage

Wastewater from factories, processing zones, and aquaculture areas is led through the screens. Coarse, large-sized garbage (such as leaves, fish bones, fins, crustacean shells, ...) is removed before flowing into the sand settling tank. The sand component will be deposited at the bottom of the tank.

The next stage is the conditioning tank, the wastewater is aerated. The conditioning tank regulates the flow and concentration of pollutants in the wastewater.

2. The stage of flotation, flocculation

Alum PAC (Poly Aluminum Chloride) or polymer PAM (Polyacrylamide) is a prerequisite agent of this stage, the flocs after flocculation will flow through the flotation system. To put it simply, when injected, air bubbles will emerge carrying oil scum and suspended flocs. The wiper system on the tank will decant grease and sludge and bring it back to the sludge tank. Even in this stage, suspended solids and grease can be removed up to 90%.

In fact, the polymer has a higher flocculation efficiency, ARK Vietnam is currently distributing polymer PAM (Polyacrylamide) in two forms: powder and emulsion in bulk with attractive discounts.

3. Biological treatment of aquatic wastewater

Anaerobic treatment

From aeration tank to tank UASB (anaerobic bioreactor) – Upflow Anaerobic Sludge Blanket). Anaerobic microorganisms here will decompose organic compounds containing nitrogen and phosphorus. COD and BOD removal efficiency are from 60 to 80%. The products of the process are simple organic substances such as methane (CH4), water, CO2, H2S.

Anaerobic microorganisms + Organic matter → CO2 + CH4 + H2S + new biomass

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Aerobic treatment

The anoxic and aero tank clusters are the next stage. Synthetic treatment processes such as BOD reduction, nitrification, ammonium reduction and nitrate reduction to nitrogen gas, phosphorus reduction are carried out. The stubborn organic compounds remaining in the wastewater are oxidized by aerobic microorganisms to CO2 and water. People often reuse sewage sludge or activated sludge, especially containing microorganisms, to increase treatment efficiency.

Activated sludge concentration ranges from 1000 to 3000 MLSS mg/L (MLSS stands for Mixed liquor suspended suspension) solids or mixtures of suspended solids). The higher the sludge concentration, the greater the organic load. Oxygen is continuously supplied to the tank by a blower system. The ideal bubble diameter is about 10 µm. Oxygen is needed for microorganisms to function. The system stirs evenly to increase the contact area.

After the aero tank, settling tank 2 (biological settling) is the next step to step. The sludge generated from the microbial biomass and the sediments are kept at the bottom of the clarifier. The amount of sludge is partially circulated in the aero tank. The rest is taken to the sludge treatment area.

4. The stage of Physico-chemical treatment of aquatic wastewater

The water after being separated from the sludge becomes clear and harmful dissolved substances have been removed to the maximum. In the next stage will be disinfected with chlorine or ozone. After the re-measurement of chemical indicators, water can be discharged into the environment or reused for production.

5. Aquatic sludge treatment stage

The sludge from the settling tank and the UASB tank is put into the sludge storage tank. Although it's called mud, the key ingredient is still water. Therefore, the sludge has an enormous volume and volume. If the production scale of the seafood processing plant is large, then the sludge storage tank needs an enormous capacity. If not handled in time, it will cause congestion and stall the operation of the whole factory.

→ This is where sludge dewatering machines can go mainstream.

See more: Sludge dewatering machine – a great assistant for industrial wastewater treatment

Benefits of sludge dewatering machine in aquatic sludge treatment

The method of using a sludge drying yard is outdated in the current situation. As the fishing output is increasing, the scale of factories, export processing zones, and seafood processing zones is continuously expanding. The market of Vietnamese enterprises is no longer confined to the domestic market, but also attracts the attention of international partners. Therefore, the volume of sludge generated is increasing.

Hiring external sludge treatment and suction units is only a temporary measure. In the long run, the annual cost is a huge number. Instead, investing in upgrading modern wastewater treatment and sludge treatment systems will be an investment with a strategic vision and long-term economic returns.

The sludge dewatering machine will filter most of the water from the sludge solution, reducing the volume and weight of the sludge. Helping to reduce the number of trips to transport and reducing the amount of sludge to be handled. That is saving money for investors.

See more: Why investment in sludge dewatering purchasing is right and profitable?

Limitations of the old method

  • The sludge drying yard is extremely space-consuming, depends on the weather, and causes odors and environmental pollution. Not to mention the need for a lot of workers and losing workers' health.
  • Generations of sludge dewatering are old, outdated, inefficient, or congested. Regular repairs, causing production delays.
  • The filter press operates intermittently. It is extremely difficult to remove the mud manually, as well as the hard, water-consuming cleaning.
  • The belt press is bulky, taking up a lot of factory space. Causes unpleasant odors during operation. Cost of operating labor and washing water. Regularly have to align the conveyor belt and replace the cumbersome and strenuous filter.
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The old sludge treatment methods have too many shortcomings

Works alternative to Sludge dewatering ARK Vietnam modern

  1. Screw press: closed system, effective deodorization, avoiding the leakage of aquatic sludge that pollutes the factory. Smooth operation, energy saving, automatic control, non-stop continuous operation. Save washing water, easy to replace and maintain each screw, while the other screw can still work. Avoid stagnation in production activities. Improved mechanism with separation filter system, dynamic disc system reduces friction and prolongs product life.
  2. High-pressure belt press: There are many improvements in durability, semi-automatic mode saves labor costs. Enhanced sludge pressing mechanism, making the mud drier and more stable.
  3. Decanting centrifuge: closed system, fully automatic and continuous operation. High strength, dry mud cake, stable. Diverse capacity, suitable for a good deal of sludge. Impressive durability, automatic cleaning. Compact size, easy installation, and convenient to move.
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New generation sludge dewatering will bring high economic efficiency and sustainability

Dedicated after-sales service, 24/7 customer care

In particular, the repair and maintenance process of ARK Vietnam is extremely prestigious and fast. We have a factory right in Vietnam. Application of machinery line completely imported from Korea. Replacement parts are always available, reducing waiting time for customers.

Quick repair, readily available spare parts are the strengths of ARK Vietnam compared to other sludge dewatering manufacturers.

When choosing ARK Vietnam, you will never be disappointed

Phone number: 0977.675.754 (Vietnamese) / 0384.851.395 (Korean)
Website: /
Email: [email protected]
Hanoi Office: 5th floor, N03-T7 Diplomatic Urban Area, Xuan Tao Ward, Bac Tu Liem District, Hanoi.
HCMC Office: 197 Huynh Tan Phat Str., Tan Thuan Dong Ward, District 7, HCMC.

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