Water color is a routine parameter in water quality testing, widely applied in water plants, industrial water systems, environmental authorities, hospitals and other sectors. Obvious color in wastewater indicates severe water pollution, which may degrade product quality during industrial production and pose risks to human health. Therefore, water color testing is required across many industries, mostly measured by water quality monitors. Impurities in wastewater will interfere with the COL-8000 online water color analyzer, leading to inaccurate or failed measurement results. This article introduces methods to remove impurities in wastewater.
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Chlorination treatment
Chlorination is adopted for wastewater with high organic content, achieving around 80% color removal rate. During treatment, residual chlorine shall be maintained above 0.5 mg/L. The reaction proceeds faster under low pH conditions. Chlorination should be arranged before coagulation treatment, and residual color after chlorination can be further removed via coagulation.
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Coagulation treatment
Coagulation, clarification and filtration can remove 75%~90% impurities when color-causing substances in water exist as suspended solids and colloids. Aluminum nitrate, basic aluminum chloride can be used as coagulants, and organic polymer flocculants can also be added appropriately.
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Adsorption treatment
This method uses porous solid materials to trap color-causing impurities on solid surfaces for separation. Granular activated carbon and macro-porous adsorbents are commonly used.
For granular activated carbon filtration: a bed height of 0.6~1.5 m applies to water with low color values, while 1.5~3.0 m is used for high-color water.
Macro-porous adsorbents are bead-shaped macro-porous high polymers. They remove color-causing impurities in water through adsorption and desorption.
