The manufacturing process of natural rubber material require to add large amount of preserving chemicals, common known as formalin. For each ton of rubber making process, it generates about 20 tons of wastewater. The rubber manufacturing facility always faces the challenge problem to meet local regulatory requirements for wastewater discharge.
(Formalin, solution of formaldehyde, a solution of formaldehyde in water, used as a disinfectant and for preserving organic specimens. Formalin is a common preserving chemical, in the water, it generates HCHO to perform preservation.)
The major steps of Rubber Wastewater Treatment Process:
1. Aeration Tank Operation (A1 +A2)
Oxidize formalin and reduce the concentration to become biologically degradable. When wastewater flows into the treatment facility, initially it goes through the aeration tank (ponds) operation (A1+A2). The aeration pump consistently provides oxygen into the wastewater to oxidize the formalin concentration in the wastewater. The wastewater initially is treated in the Tank A1, and the flow-over water is continuously treated in the Tank A2. Some of the formalin materials are oxidized, and some of the formalin materials are absorbed by the sludge in the aeration tank.
2. Inter-Aerobic Operation (B)
Consume the major portions of organic chemicals in the wastewater. When wastewater enters into the inter-aerobic tank, the amount of fermalin is low. In this inter-aerobic tank (or also called intermittence-aeration tank), the amount of oxygen supply is controlled. The range of dissolved oxygen is set between 0.3 mg/l ~ 1.0 mg/l. In some special circumstance, the dissolved oxygen can raise up to 2.5 mg/l. Because under the low dissolved oxygen condition, when aeration operation is closed, the remained oxygen in the water will be consumed in a short period of time, therefore the tank which was original in aerobic operation can turn into anaerobic operation within short time frame.
While the microorganisms are under the anaerobic operation, microorganisms would try to eat or absorb chemical materials in the wastewater. Microorganism would have very strong tendency to absorb materials through cell into the body. Because of lack of oxygen, it is a slow process to dissolve the materials inside the cell body, and it is more likely that the microorganism will absorb more material into body than it can decompose. When the tank is operated under aerobic mode, the microorganism must release the unfinished by-products from its body. Generally the release by-products are semi-finished products with initial stage of decomposition. The by-product size is much smaller than original. Therefore it is relatively easy to be further oxidized through aerobic reaction. Through the periodical aerobic and anaerobic operation, and the microorganism digests food into body and release from the body, the decomposition speed can be greatly improved. Thus this operation procedure can have much better effective performance than single aerobic or single anaerobic operation procedure, and it also shows better efficiency.
3. Sediment Tank Operation
Collect solid materials through sedimentation process and provide activated sludge to inter-aerobic tank and aeration tank. The over-flow wastewater from the inter-aerobic tank flows into the sediment tank. The sediment tank collects solid materials and large size chemicals. These sludge is recycled back into the inter-aerobic tank for further process and the extra sludge also can pump into the aeration tank for the oxidization process.
4. 2nd Treatment Operation
Perform inter-aerobic operation in a longer resident time. The wastewater from sediment tank passes through the screen filter and enters into the 2nd treatment operation. In this operation, the tank (pond) size is relatively big size. This can provide longer resident time for water in this tank. In this tank, the water still is under inter-aerobic operation. By controlling the amount of oxygen supply, the tank can be in the mode of aerobic and anaerobic operation sequentially. After this treatment, the water passes through a screen filter for discharge.
For high COD content, the aeration in inter-aerobic tank operates 40 to 50 min., and shut off 10 to 20 min. For low COD content, the aeration of inter-aerobic tank operates 10 to 20 min., and shut off 40 to 50 min. Dissolved Oxygen maintenance range is between 0.3 ~ 2.5 mg/l, the preferred range is between 0.3 ~ 0.7 mg/l. The total capacity of activated sludge is about 5% ~ 10% of the size of inter-aerobic tank, in order to maintain the biological cycling period between 24 to 48 hours. The amount of activated sludge in the activated sludge tank is about 30% ~ 40% range.
The Rubber Wastewater Treatment Process is effective and efficient, and easy to operate.