Study On Treatment Of Tannery Chrome Wastewater

Chromium is one of essential trace element in human body. Under the excessive intake of chromium, there will have a great harm on the skin, respiratory system and digestive system. The total chromium content in tannery effluent from a factory of Shanxi is up to 2010.8mg/L,and the content of chromium(VI) is 0.14mg/L. Transforming chromium into hydrogen chromium precipitation by chemical flocculation and precipitation method, the total chromium is reduced to 0.69 mg/L when the appropriate PH,alkali,flocculation are selected, so the national discharge standards of chromium effluent(GB8978-1996,the content of total chromium is less than 1.5mg/L and the content of chromium(Ⅵ) is less than 0.5mg/L) can be met. When hydrogen chromium is dissolved by adding sulfuric acid and solution is evaporated and crystallized, the recovery rate of total chromium is up to 72.8%. The wastewater containing chromium ions was treated at room temperature by nanofiltration membrane. The morpHology, concentration of chromium ions and the pressure of the membrane on the rejection effect were studied. The results showed that:under the experimental conditions, the water flux will improve when the pressure of membrane increasing but retention have a certain degree of decline. Since Donnan exclusion present, Cr (Ⅲ) and Cr (VI) show varied tendency as the feed concentration of chromium ion increasing. Beside, the effect of pH is important to the removal by nanofiltration.