1 Overview

        The three-waste treatment project refers to the treatment of waste water, waste gas and waste solids generated in the surface treatment process. Due to the large amount of waste water generated in the surface treatment of industrial aluminum profiles, this section discusses wastewater treatment.

        Acidic water in the production of industrial aluminum products mainly comes from the acid etching process in the chlorination plant, neutralization, oxidation processes, oil removal from the spray coating process, pickling, etc. Wastewater contains various harmful substances or heavy metal salts. The acid mass fractions vary widely, ranging from less than 1% at low to greater than 10% at high. Alkaline wastewater mainly comes from alkali etching in the chlorination plant, spraying and pretreatment alkali washing. Some of the bases have a mass fraction of more than 5%, and some are less than 1%. Spraying, dyeing also produces waste water. Wastewater, in addition to containing acid and alkali, often contains oils, paints, fluoride salts and other inorganic and organic matter. In addition, the chromium effluent produced after chromate treatment is a very toxic waste. The acid-alkali waste water is highly corrosive and needs proper treatment before it can be discharged. The general principles for the treatment of acid-alkali wastewater are:

     (1) High-concentration acid-alkali wastewater should be given priority to recycling, and should be reused as much as possible according to water quality, water volume, and different process requirements. If there is difficulty, or the concentration is low, the amount of water is large, and it can be recovered by the concentration method.

     (2) Low-concentration acid-alkali waste water, such as washing water in the washing tank, and rinse water in the alkaline washing tank, should be neutralized.

         The neutralization treatment first considers the principle of waste treatment, such as the neutralization of acid and alkaline waste water or the use of spent alkali (slag) and acidic waste water, and the use of waste acid to neutralize alkaline waste water. Neutralizers may be used when these conditions are not available.

  According to the national standard GB8978-1996 "Water Pollutant Emission Limit" emissions requirements: CDO level ≤ 60mg/L, secondary ≤ 120mg/L, suspended matter ≤ 100mg/L, chloride ion F-≤ 60mg/L pH value 6-9.

  Hazardous waste gas, ash, oil sludge and other solid wastes generated during the surface treatment of industrial aluminum profiles should also be treated and discharged according to relevant standards.