I. OVERVIEW OF SLUDGE TREATMENT
The increasing amount of sludge arising from the decomposition of organic pollutants in urban and industrial wastewater treatment plants is a major environmental challenge and also a current dilemma in Vietnam and region. Waste sludge needs to be treated properly through appropriate processes and technologies so as not to pollute the environment and then can be used for other purposes with economic value.
At Hoa Phat Eco, we do not see sludge as a waste but as a highly valuable resource. We have been oriented to apply the world’s leading sludge treatment solutions and technologies to minimize the amount of water in the sludge, extract valuable biological solids to produce other products. serving agriculture and industry, recovering heat by sludge drying and burning technology. From there, it helps to optimize the operating costs of wastewater treatment plants and water supply stations, solve pollution problems, and bring high value and economic efficiency.
1. Waste sludge?
Sludge from cities and industrial plants is a by-product of wastewater treatment. It is usually a mixture of organic and inorganic substances from human waste, microorganisms and from the manufacturing process. Waste sludge in wastewater treatment plants usually includes biological sludge and physicochemical sludge.
Regardless of its origin, sewage sludge contains water, dissolved organic and inorganic materials, and suspended solids. Suspended solids typically make up 2–5% of municipal sludge. The chemical composition of the sludge also depends on the wastewater characteristics and the wastewater treatment method.
2. What is sludge treatment?
Sludge treatment is an important component of municipal and industrial wastewater treatment processes. The main goals of sludge treatment are:
– To reduce harmful microorganisms (such as pathogens) in the sludge, reducing the risk of health effects to humans and the environment
– Reduce odors that pollute the factory and the surrounding environment
– To stabilize some organic substances in the sludge which, if not treated, will naturally evaporate and turn into harmful gases in the atmosphere.
– To reduce the final volume of sludge, which reduces collection and treatment costs.
3. Why waste sludge treatment?
Wastewater cannot be treated satisfactorily and clean water cannot be recovered unless the solids in the wastewater (sludge) are separated. Sludge treatment are key elements in the design and operation of all wastewater treatment plants.
Although sludge typically accounts for only 0.2 – 0.4% of the wastewater flow received by a treatment plant, its treatment typically accounts for up to 50% of a wastewater system’s operating costs.
Sludge generated from wastewater treatment plants usually has a DS of 1 to 5% depending on the input wastewater and treatment technology.
The average DS content of the digested sludge was 4%. This means that one cubic meter of dilute sludge contains 960 liters of water, without treating the water content, the treatment costs will be very high.
Therefore, the basic purpose of sludge treatment before final treatment is to reduce its mass and stabilize the organic components in the sludge. Stabilized sludge has no unpleasant odor and can be disposed of without harm to health, reducing the cost of pumps and slurry equipment.
4. Contractors, companies providing sludge treatment solutions?
Understanding the current situation of sewage sludge, along with a thorough understanding of wastewater treatment technologies, Hoa Phat Eco Company is proud to be a pioneer in researching and providing sludge treatment solutions in Vietnam. With our proficiency and experience in technological design, automation solutions, construction and installation of sludge treatment systems for many industrial plants, we are confident to solve sludge problems waste, minimizing sludge collection costs, bringing profits and investment efficiency, contributing to ensuring a sustainable production environment for businesses.
II. SOLUTIONS, TECHNOLOGY OF SLUDGE TREATMENT
1. Sludge screening
This is the process of separating and screening large-sized solids and debris mixed in dilute sludge to help prevent disruption of sludge treatment processes and equipment at the next stage. Most industrial wastewater treatment systems today often use garbage separators at the inlet wastewater receiving point. But some systems have a dilute sludge source with some fibers and debris that are difficult to separate and concentrate the sludge. Therefore, some wastewater treatment plants use additional sludge screening equipment in the first stage of the sludge treatment system.
2. Sedimentation and concentration of sludge
Although most of the water has been separated in the wastewater treatment process, physically the raw sludge is still very liquid. Sludge concentration is a necessary step to separate more water from the solid components before anaerobic digestion. It reduces the overall sludge volume and increases the solids ratio in the sludge. Sludge before thickening usually contains about 2-4% solids by weight, and when concentrated this can be obtained up to 16-18% solids by weight (also known as %DS or dry solids).
There are many methods or devices for performing sludge concentration. The simplest is to use gravity to settle the more solid part of the sludge. It usually has a slow stirring mechanism to help settle the “solid” sludge at the bottom of the sump. Other concentration methods include dissolved air flotation, centrifugation, and sludge rake.
3. Sludge decomposition
There are two main types of decomposition in municipal sludge treatment plants: anaerobic (without oxygen) and aerobic (with oxygen). Of the two, anaerobic digestion is generally more cost-effective and has the economic and environmental advantage of generating biogas and lower volumes of biosolids.
4. Dewatering sludge
Diluted sludge needs to be dewatered by press machines before treatment. In the past, many wastewater treatment systems also used the method of drying sludge with a drying yard. However, this method is gradually becoming less popular because of the expensive land area and low efficiency.
Therefore, using a sludge pressing machine is an optimal solution to reduce the water content in the dilute sludge, reduce the sludge after pressing to achieve high dryness, and reduce the area of sludge storage.
Hoa Phat Eco specializes in the supply and installation of sludge press products in Vietnam, including:
- Decanter centrifugal: this is a type of sludge press that uses the principle of centrifugal force to separate the water from the slurry. The sludge after pressing the centrifuge has a moisture content of about 80-85%. Decanter centrifugal has the advantages of compactness, hygiene and safe operation.
- Belt press is a type of sludge press that is commonly used in wastewater treatment systems thanks to its simple operating principle, easy installation and low investment cost. However, the sludge dryness after pressing is still low, and the operating costs are high due to the high use of polymers and conveyor washing water.
- Multi-disc screw press: Although the sludge moisture content of the screw press is similar to that of a dencanter centrifugal and a belt press, it is gradually being widely used thanks to its compact size and low water consumption wash, no odor during operation. In addition, the screw press can press almost all kinds of sludge, with grease and oil, which the belt press and filter press cannot press. Our screw press product is made entirely of stainless steel 304 or 316, screw coated with high strength tungsten carbide hardener, automatic control with PLC, HMI, SCADA system.
- The filter press is a device that uses pressure from the cylinder and sludge pump to absorb water out of the sludge through the filter cloth. This type of sludge press is suitable for physicochemical sludge with high water separation efficiency, and the sludge moisture content after pressing is only 60-80%. However, filter press often operate in batches, so the processing capacity is not high, requires a large installation area, requires labor to operate, remove sludge and clean filter cloth.
To solve the disadvantages of the conventional plate filter press, Hoa Phat Eco researches and supplies the membrane filter press with a special plate frame design, pressing pressure up to 16 bar. The sludge after pressing reaches the optimum dryness, the moisture content of the sludge after pressing is only 45-65%. In addition, our membrane filter press has automatic filter cloth washing function, controlled by PLC, HMI, SCADA, which saves time and labor.
The above types of dewatering machine are all used for the purpose of reducing the water content in the dilute sludge, making the sludge easily transported or stored in barrels or bags. The dryness of the sludge after pressing varies greatly depending on the type of sludge and the type of sludge press machine used.
In addition, Hoa Phat Eco also processes and provides equipment for collecting and transferring sludge such as screw conveyors, belt conveyors. These are devices commonly used in sludge treatment systems used to transfer the sludge after pressing to the sludge dryer or transfer the sludge after pressing and drying to the sludge storage area. The belt conveyor is usually made of PP plastic material, while the conveyor screw is made of SS304 or SS316 material.
5. Sludge drying
In Vietnam, dried sludge after pressing will be collected and treated by licensed companies in accordance with regulations. However, some factory with large sludge volume or with high standards of environmental protection will continue to bring the sludge to the second drying stage with a sludge dryer.
The sludge dryer is a device that uses heat energy to evaporate the water in the sludge, reducing the moisture content of the sludge to a maximum of 10-30%. At this dryness, the sludge has a smooth and uniform character, which can be used as a raw material for the incinerator.
Hoa Phat Eco provides many types of sludge dryers depending on the sludge capacity and sludge type of each production industry. But in general, there are two main types of operating principles: indirect and direct.
- Low temperature dryer (also known as belt dryer) is a direct sludge drying type, providing a source of hot steam to convection the surrounding air in the dryer according to the movement of the conveyor to dry the sludge.
- Paddle sludge dryer (or hollow paddle dryer) is a type of dryer that operates on the principle of continuous mixing with the shaft and impeller containing heat inside to indirectly evaporate the water in the sludge.
Benefits of sludge dryer:
– Reduce the cost of sludge collection and treatment: With the current expensive sludge collection and treatment costs, sludge drying helps reduce the volume of sludge by 4-5 times compared to sludge after pressing, helping the plant save a lot of money. large collection costs.
– Reduce the area of sludge storage, the smell of the sludge storage area: The sludge after pressing by the dewatering machine still has a high water content, so it consumes the sludge storage area, causing the smell of the wastewater treatment system area. Waste sludge after drying is in the form of a fine powder without odor, collecting and storing sludge is more convenient because the volume has been greatly reduced compared to the original.
– Reuse as fuel: The sludge after drying is a loose powder, which can be mixed with combustion materials or put directly into the incinerator. The calorific value of sludge when burned reaches 5-15 MJ/kg, so it can be used for energy recovery purposes. Some types of sludge with organic matter content can be used as fertilizers, soil amendments, production of building materials, etc.
– Contributing to helping businesses and factories achieve green certificates, certificates on environmental protection and sustainable development, improving corporate image and product value for export markets.
Above is an overview of sludge treatment solutions and technologies provided by Hoa Phat Eco. With the capacity and understanding of technology in the field of water treatment, Hoa Phat Eco is the EPC contractor for projects on sludge treatment in Vietnam and the region. We accompany customers throughout the entire project lifecycle with a turnkey package service from technology design consulting, sludge treatment equipment supply, installation and commissioning services.
We are committed to providing customers with sludge treatment products such as sludge rake, sludge press, automatic polymer mixing system, sludge dryer with superior quality and automatic control solution to help ensure The system operates stably and efficiently, contributing to reducing sludge collection and treatment costs, and optimizing operating costs for the plant.