Sugarcane is an important raw material for sugar production – an essential product used in daily life. In addition, sugar cane also brings a lot of value to people not only in terms of economy but also in users’ health. To create the above benefits, sugar cane needs to go through many stages of product formation. As a result, a large amount of wastewater will be produced, increasing the possibility of environmental pollution. So what are the characteristics of sugarcane wastewater? And how to treat wastewater to ensure the right process and be environmentally friendly?
1. Production situation of the sugar industry in Vietnam.
In 2021, the sugar industry in Vietnam has shown positive signs, restoring domestic production. Besides, sugar prices tend to increase due to the positive effects on the world.
Currently, the total amount of sugarcane is 5,290,000 tons, equivalent to 530,000 tons of sugar.
2. Pollution properties and composition of sugarcane wastewater.
Wastewater from sugarcane always contains a large amount of organic substances such as carbon, nitrogen, phosphorus, and other biodegradable compounds. Therefore, the characteristic of this wastewater is high BOD and high fluctuation. In addition, these substances are easily decomposed by microorganisms, causing rotten odors contaminating the water.
Besides, in the sugar industry wastewater contains suspended solids in inorganic form. When it is discharged into the natural environment, these substances have the ability to settle and form a thick layer of mud at the bottom of the water source, destroying the biota making food for fish. This layer of sediment also contains organic substances that can deplete oxygen in the water and create gases such as H2S, CO2, CH4.
In addition, sucrose and other sugars such as glucose and fructose are also main components in sugarcane wastewater, affecting the activity of microbial populations in the water and polluting water sources. Because, when they decompose, they deplete the oxygen in the water and produce gases such as H2S, CO2, CH4.
Besides the above substances, it also contains H+ and OH- ions, making the sugar factory wastewater having acidic, due to the rinsing of the resin column.
3. Sources of sugarcane wastewater.
Wastewater in the production process at different stages will have different levels of contamination. The main sources are:
Wastewater from sugarcane pressing area: water is used to squeeze sugar in sugarcane and cool the bearings of the press, so the wastewater contains high organic matter and grease.
Wastewater from the boiler site: wastewater will be periodically discharged, with high suspended solids characteristics and low BOD value, alkaline wastewater.
Wastewater washing filter, cooling, washing equipment, and washing floor: although the washing wastewater has a small flow rate, the BOD and suspended matter values are high.
4. Sugarcane wastewater treatment solution.
Currently, there are 3 methods for treating sugarcane wastewater: mechanics, physicochemical, and biological methods. However, we can apply biological solutions to be able to effectively sugarcane wastewater.
- Anaerobic tank.
Anaerobic technology is used for wastewater with high pollutants in order to reduce pressure for the following process. In the process of transferring wastewater from the conditioning tank to the anaerobic tank, the microorganisms will decompose organic substances into simple inorganic substances such as CH4, CO2, H2S. In this process, gas is used to burn boilers, generate electricity, and cook…
Organic matter →CH4 + CO2 +H2 + NH3 + H2S + new cells
After restarting the system, anaerobic microorganisms will be added to the Biogas tank increasing the number of anaerobic microorganisms, reducing COD, BOD, TSS of wastewater as well as decreasing sludge, methane …
- Anoxic tank.
After being regulated inflow, the waste concentration is pumped with a stable flow into the anoxic tank. Here, the process of denitrification takes place to achieve the target of nitrogen.
NO3– → NO2– → NO → N2O (g) → N2
The group of nitrifying bacteria is the majority of this process with about 70-80% of the bacterial mass (activated sludge). The denitrification rate ranges from about 0.04 to 0.42g N-NO3-/g MLVSS. day, the higher the F/M ratio, the higher the reduction rate.
To increase the treatment efficiency, the tank is equipped with a stirring device to improve the contact ability of microbial sludge in the wastewater.
After restarting the system, it is necessary to add Biofix Ammonia microorganisms to promote nitrogen treatment in anoxic tanks.
- Aeration tank.
This is the most important stage in wastewater treatment, treating organic matter thoroughly because of the microbial system maintained from the air blower in the “Aerotank Tank”. Besides, along with the speed of aeration, it will help microorganisms directly contact pollutants and decompose them.
Releasing of gases inhibits the life process of microorganisms, these gases are produced during the process of microorganisms breaking down pollutants, in order to positively affect the reproduction process of organisms. This process is based on the principle of aerobic microorganisms decomposing organic matter in the presence of dissolved oxygen according to the following equation:
Organic matter + O2 + nutrients → CO2 + NH3 + C5H7NO2 + other products
To create new cells, besides organic decomposition, microorganisms also perform endogenous respiration to produce energy according to the equation:
C5H7NO2 + 5O2 → 5CO2 + 2H2O + NH3 + H