Rubber latex processing wastewater has very high organic matter content such as dissolved protein, COD, BOD, and SS. In addition, there is formic acid (used to freeze pus), and N-NH3 (used as an anticoagulant). Therefore, ineffectively rubber latex processing wastewater is discharged into the environment to cause pollution to water sources.
Where does the wastewater of the latex come from?
Rubber wastewater comes from two main sources:
+ Activities: washing hands, personal hygiene, bathing.
+ Production: drying and mixing stage, freezing stage, mechanical processing, and water drop arising from washing equipment and machinery or cleaning the factory.
Characteristics of rubber latex processing wastewater:
Rubber industry wastewater always has a large flow compared to the others. In particular, wastewater residue is generated during the freezing and rolling stage of the crepe, mainly because the rubber particles (pus) after coagulating into an array have rubber particles but have not yet agglomerated…
In addition, wastewater contains high NH3, high BOD, COD, SS; Low pH (in the production stage, acid is added to allow the latex to coagulate). Rubber wastewater has a low pH due to the use of acid for the coagulation stage, a high amount of N-NH3 due to use in the antifreeze process, formic acid used in the freezing process, and a high amount of soluble protein.
But depending on the processing method of the processing company, the wastewater will have different characteristics such as:
+ Centrifugal latex method: Rubber wastewater often has very high pH, BOD, and COD.
+ Latex nuggets method: Rubber wastewater usually has low pH, but high BOD, COD, SS
+ Mixed latex method: pH from 5-6, BOD and COD are lower than the latex method
From here, we see that rubber wastewater is a difficult treatment. It is necessary to combine many chemicals with biological methods to bring wastewater to the standard threshold.
The retention time of rubber wastewater from 2-3 days will occur to protein decomposition in an acidic environment. The bad smell arises due to the protein decomposition in an acidic environment, giving rise to many different gases such as CH4, H2S, etc. The smell affects the living environment of the surrounding people, as well as the workers themselves, who work at the factory.
Biological treatment of rubber wastewater
Wastewater from the technological process is led through the screen to remove coarse impurities of large size, then the wastewater is led through the wastewater tank and the sand settling tank, where the sand particles are larger than 0.25 mm will be storage to avoid affecting the pumping system in the following works. Then, the wastewater passes through the conditioning tank to regulate the flow, overcoming the phenomenon of local loading of the works behind. Wastewater from the conditioning tank is pumped into the flotation tank to remove suspended solids with lower specific gravity than water, on the tank, there is a collection system for foam and rubber blocks for recycling. Wastewater is mixed with NaOH and nutrients to create a favorable environment for the biological treatment work behind.
Wastewater continues to bring to the UASB tank, pH favorable for the operation of the UASB tank is 6.7 – 7.5. In the UASB tank, microorganisms in the anaerobic form will decompose organic substances in wastewater, the treatment efficiency of the UASB tank calculates according to COD, BOD reaching 60-80% into inorganic substances in a simple form and Biogas (CO2, H2S, CH4, NH3…).
To promote anaerobic digestion in the UASB tank, we need to add probiotics Biofix 114.
After the UASB tank is discharged through the Aeroten tank to treat organic compounds. In the Aeroten tank, the aerobic biological process maintains by the air blower. Here, microorganisms in the form of aerobic (activated sludge) will decompose the remaining organic substances in the wastewater into simple inorganic substances such as CO2, H2O … The decomposition process of microorganisms depends on the following conditions: pH, temperature, nutrients, sludge concentration, and homogenization of the wastewater. Therefore, it is necessary to monitor these parameters in the Aeroten tank. COD removal efficiency in the tank is from 90-to 95%.
Just like in anaerobic tanks, in aerobic tanks, it is also necessary to add microorganisms to promote the decomposition of organic matter in this tank. That is the aerobic microorganism Biofix 5D
From the Aeroten tank, wastewater leads to the settling tank, where the separation between water and activated sludge takes place. The activated sludge settles to the bottom. Wastewater brings to the biological pond before being discharged to the receiving source. The activated sludge at the bottom of the settling tank is partially pumped to the Aeroten tank to maintain the microbial content in the tank. Excess sludge is pumped into the gravity sludge compactor tank to reduce the volume. It is then pumped to the mixing compartment of the belt filter press to mix with the polymer, and then through the sludge pressing conveyor system. Waste sludge is in the form of cakes and is buried or used as fertilizer.
To promote the biological treatment of anaerobic and aerobic tanks, we need to add probiotics Biofix 114 for anaerobic tanks