Leather Industrial Park Wastewater Treatment

At present, China is the largest leather manufacturing country in the world. The leather industry waste water has large volume, strong bolatility, complex composition and contains a large amount of suspended solids, organic matter and ammonia nitrogen and other toxic substances. The water samples for the study is comprehensive wastewater, samping from a leather industrial park of Shandong. The purpose of the study is to study the basic processes of wastewater treatment, and optimize the relevant conditions through small pilot experiment.In this paper, both physico-chemical and biological wastewater were applied to treat the wastewater. Firstly, alkali was applied as pretreatment. The reasults showed that the optimum p H was 12, which could make the best flocculation and provide the optimum p H for ammonia stripping. To reduce the cost of wastewater treatment, calcium hydroxide and sodium hydroxide were used in this study. Calcium hydroxide was added to the wastewater, which could adjust the p H to about 10. Heavy metals and other substances in the wastewater were formed precipitate. And then sodium hydroxide was added to adjust p H to 12 and a flocculated state was formed in the wastewater. The COD could be reduced by 300-400 mg·L-1 after alkali addition. The next process was ammonia stripping. The results showed that the optimum temperature of ammonia stripping was 30 ℃, and the optimum time of ammonia stripping was 20 h. Wastewater ammonia decreased from 666.27 mg·L-1 to below 100 mg · L-1 after stripping.Then, aerobic biological treatment, hydrolysis acidification, aerobic biological were applied to treat wastewater for biodegradation. COD could reduced to about 400 mg·L-1. Next, Fenton oxidation process was used, which could oxides partial pollutants in wastewater, while made some non-biological contaminants change. The biodegradability of wastewater was improved. The results showed that the optimum conditions of Fenton oxidation: the temperature was 30 ℃. The initial p H of the reaction was 4. And reduction time was 1.5h. The molar ratio of hydrogen peroxide and iron sulfate heptahydrate was 5: 1. The ratio of Fenton reaction actual amount and theoretical amount was 1.2. After Fenton oxidation, B/C can be increased to 0.54 and COD is 222.26 mg·L-1.Finally, further aerobic biological treatment was applied to treate wastewater. COD reduced to less than 60 mg·L-1 and ammonia reduced to less than 10 mg·L-1. The wastewater could reach “Integrated Wastewater Discharge Standard in Haihe River Basin of Shandong Province”DB37 / 675-2007)...