1.1  Objective

To treat the effluent from the third sedimentation tank of a chemical plant to reduce the color to less than 80 (Platinum-Cobalt colorimetric method).

2.1 Reagent Usage Instructions

Reagents used in the experiment and their dilution ratios:

3.1 Experimental Procedure

3.1.1 First Group of Experiments:

Three cups, each with 80ml of effluent from the third sedimentation tank, were taken. 1000ppm/1500ppm/2000ppm of poly aluminum chloride solution was added to each cup, stirred well, and then 0.2ml (2ppm) of PAM solution was added. The mixtures were left to settle.

The color of the supernatant was observed. Visually, there was little difference in the supernatant color of the three cups, indicating that increasing the amount of poly aluminum chloride had a minimal impact on the effluent color.

3.1.2 Second Group of Experiments:

Three cups, each with 80ml of effluent from the third sedimentation tank, were taken. 0.4ml (200ppm)/1ml (500ppm)/2ml (1000ppm) of BWD Water Decoloring Agent solution was added to each cup, stirred well, and then 0.8ml (1000ppm) of poly aluminum chloride solution was added. The mixtures were stirred again, and finally, 0.2ml (2ppm) of PAM solution was added. The mixtures were left to settle.

The color of the supernatant was observed. There were significant differences in the supernatant color of the three cups. As the amount of BWD Water Decoloring Agent increased, the color of the treated supernatant decreased.

3.1.3 Third Group of Experiments:

One cup with 80ml of effluent from the third sedimentation tank was taken. 2000ppm of sodium hypochlorite solution was added and stirred well, followed by 0.4ml (200ppm) of decolorizing agent solution, stirred well, and then 0.8ml (1000ppm) of poly aluminum chloride solution was added. The mixture was stirred again, and finally, 0.2ml (2ppm) of PAM solution was added. The mixture was left to settle.

The color of the supernatant was similar to that treated with 1000ppm decolorizing agent in the second group, indicating that the combination of sodium hypochlorite, decolorizing agent, and poly aluminum chloride can effectively remove the wastewater color.

4.1. Conclusion

Through multiple small-scale tests, it was verified that using BWD decolorizing agent in combination with PAC can effectively reduce the effluent color of the third sedimentation tank wastewater to meet discharge requirements. Considering treatment costs, the addition of sodium hypochlorite can reduce the amount of decolorizing agent needed while effectively lowering the effluent color, making it a cost-effective and practical treatment solution.