The leather industry is one of the important industries in China, and tanneries produce a large number of products while also producing up to 7×107t/a of wastewater. Chromium tanning liquid in tannery wastewater is very toxic, with a chromium concentration of 3000mg/L~6000mg/L, and contains a large amount of SS and COD, usually only 30% of leather wastewater can meet the discharge standard, seriously polluting the environment. Polyacrylamide (PAM) plays a very important role in leather wastewater treatment and is a simple and efficient leather wastewater treatment agent.
Leather wastewater treatment method:
After the wastewater is removed by the filter, it enters the coagulation treatment tank, and a molecular weight of 900-12 million polyacrylamide (PAM) is added. The removal rate of chromium ions is more than 90%, the removal rate of suspended solids is more than 70%, and the removal rate of COD is nearly 40%. After adding polyacrylamide (PAM), the sludge flocculation settles quickly, and the comprehensive effect is very good. Then the wastewater is treated with alkali in the air flotation tank, and alkaline aluminum chloride and ferrous sulfate heptahydrate are added to neutralize the wastewater. As suspended solids and part of the COD are further removed, the pH of the wastewater also decreases. The water collection through the transition tank is then lifted to the anaerobic aeration tank. At this time, the activated sludge method and porous aeration method are used, and the residence time is about 4 hours. After aeration, the wastewater is separated by solid-liquid in the intermediate sedimentation tank, and the supernatant flows into the oxidation tank and then out of the sedimentation tank.
In leather wastewater treatment, the dosage of polyacrylamide (PAM) is about 40mg/L, basic aluminum chloride is 100-200mg/L, and ferrous sulfate heptahydrate is used 300-500mg/L, aluminum sulfate is 1000mg/L, polyacrylamide (PAM) is used for leather wastewater treatment with the characteristics of small dosage, good effect and low cost, an ideal wastewater treatment agent.