Rubber wastewater treatment process

Characteristics of rubber wastewater

Rubber is an alkene, having a high molecular structure with a large number of double bonds. The basic molecule is isoprene poplymer, the main components are rubber and water. To process 1 ton of rubber products, about 18 m3 of wastewater must be discharged into the environment. Most of the rubber wastewater is generated from the latex production stage (accounting for 70%). 

Rubber wastewater will usually have a low pH, fluctuating between 4.2 and 5.2 due to the use of acid to coagulate the rubber latex. Sometimes the pH is very high, around 9-11 if rubber wastewater is generated from this method. Rubber particles exist in forms such as suspensions arising during the freezing and crepe rolling stages, during tank washing, water is separated from centrifuged latex... but rubber particles often exist in emulsion form and glue.

Rubber wastewater also contains large amounts of dissolved protein, formic acid (used in freezing) and N-NH3 (used in anticoagulation). The COD content in wastewater is also very high, up to 15,000 mg/l.

The characteristic of rubber wastewater is that it produces a foul odor. Bad odors arise from the process of protein decomposition in an acidic environment, giving rise to many different gases such as CH4, H2S, etc. Therefore, rubber wastewater treatment is always treated seriously.

Technological process of rubber wastewater treatment 

• Collection and removal of all kinds of trash

Wastewater from the factory is brought to the collection tank, large trash and impurities are removed by trash screening devices.

• Purulent sedimentation

Wastewater after trash has been removed and sent to the pus decanting tank. Here, latex cotton suspended in wastewater is separated and removed. This process helps the wastewater to be cleaned before continuing with the next treatment steps.

• Coagulation tank

Wastewater after latex sedimentation contains solid particles such as rubber particles that have not completely flocculated. This wastewater continues to be fed into the flocculation tank, in which alum and polymer are used to form residue, reducing the content of suspended matter and residue in the wastewater.

The pH in the tank has also been adjusted to create favourable conditions for microorganisms during the biological treatment process.

• UASB anaerobic biological tank

Wastewater after physicochemical treatment is fed into the UASB anaerobic biological tank. There, wastewater is brought up from the bottom of the tank and mechanically disturbed to create a reaction environment between wastewater and microorganisms. This process will help to remove organic substances and can achieve high BOD and COD treatment efficiency. The microbial sludge formed during this process is then sent to the settling tank.

• Aerotank 

Wastewater after passing through the UASB tank is transferred to the Aerotank tank. Here, the aeration system helps to activate the sludge development and the oxidation reaction takes place more quickly and effectively. This process further cleans the wastewater and further removes pollutants.

• Sedimentation tank 2 and sludge pressing

Wastewater after going through the Aerotank is sent to the settling tank 2. The sludge in settling tank 2 is then fed into the sludge dewatering machine, part of which is returned to the biological tank to continue the treatment process.

Then, the wastewater will be directed through a disinfection tank to kill disease-causing microorganisms. Commonly used chemicals are chlorine compounds. Wastewater will pass through a pressure filter column to thoroughly treat suspended solids. Finally, treated wastewater will be released into the environment or reused.

How does rubber wastewater affect the environment?

Rubber wastewater with a retention time of 2-3 days will undergo a protein decomposition process in an acidic environment, creating a foul odour, affecting the living environment of surrounding people as well as the workers themselves and affecting the quality of water used in daily life and production if rubber wastewater is not treated and discharged into receiving sources.

If rubber wastewater is not treated properly, when discharged directly into the environment, it can affect the quality of water of daily use. Pollutants in wastewater can harm human health. Besides, it can also slow down the development process of underwater animals, affecting the flora living in the water. This can lead to the destruction of the ecosystem, causing an imbalance in the natural environment.

The concentration of nitrogen and phosphorus in pre-treated rubber wastewater is often very high, easily leading to eutrophication, increasing the concentration of nutrients in the water environment, increasing the growth of algae and creating brown smoke or cloudy water appears.  

With the rapid development and impact of the rubber industry on the environment, rubber wastewater treatment has become urgent to ensure sustainability for both the environment and public health.