Study On Deep Treatment And Reuing Of Dyeing And Printing Wastewater By Double Membrane (CMF-RO)

Membrane technology has been widely used in dying wastewater treatment for its high efficiency and stability. Reverse osmosis is known for its high salt rejection, it can be used with other techniques to enhance the quality of producing water when treating dying wastewater. This paper use microfiltration(MF) and reverse osmosis(RO) to reuse dying wastewater, optimize the running condition and the way to clean membranes.It is found that using MF as pretreatment for RO is feasible. The vaule of turbidity and SDI is 0.1NTU and 5. After RO, total removal efficiency in turbidity, chroma, conductivity and COD is above 90%. The concentration of SO₄^2-, Cl^-, Ca²⁺ is 1.2, 2.8 and 0.8mg/L. The value of COD is below 10mg/L. Water qualities meet the request of that in production.Water turbidity and flux are two important factors to affect membrane fouling. Increasing the rate of flow on the membrane surface is positive to control membrane fouling and can prolong the cycle of backward wash. The best flow rate is 0.8m³/h, and the time is 3min. Transmembrane pressure drop can be recovered by 95% through backward wash.It is a linear relationship between water production rate and incoming pressure when running reverse osmosis. Increase the water temperature can decrease the viscosity of water molecule, leading the rise of water production rate. A two years old reverse osmosis was studied by chemical clean. After chemical clean, water production rate changed from 20% to 65% compared to the new one, and can be used again.