Study on Reusing of Electroplating Wastewater by Membrane (RO-NF)
|Keywords||Electroplating wastewater Reuse Reverse osmosis Nanofiltration Water pressure Desalination rate Membrane flux Chemical cleaning Reuse rate|
Electroplating wastewater membrane reuse as an efficient and low-energy water treatment technology, in many electroplating enterprises has been a wide range of applications. After materialized After electroplating wastewater reaches the reverse osmosis membrane by sand filtration and ultrafiltration after water indicators, was concentrated by a reverse osmosis membrane, the ion removal efficiency of more than 99% can be achieved, but due to the characteristics of plating wastewater having a high salinity, increasing salinity of the water inlet state, the reverse osmosis membrane ion removal efficiency and membrane flux will gradually reduce work efficiency is not satisfactory. RO concentrated water continues to be concentrated using nanofiltration membrane, nanofiltration membrane desalination rate is less than reverse osmosis membrane, nanofiltration membrane greater than the reverse osmosis membrane flux and stronger resistance to the pollution ability nanofiltration film in a high concentration of state can still reverse osmosis water continue to concentrate, which makes the system reuse rate continues to rise. In this paper, reverse osmosis (RO) and nanofiltration (NF) combined to ongoing enrichment experiments using an enterprise electroplating wastewater, optimization results than on different experimental parameters. The article also use a new reverse osmosis nanofiltration (RO-NF) systems for the reuse research pilot, the comparison of test results verify the correctness of a small pilot experiment. Dow BW30-365 reverse osmosis membrane type, NF270-400 type nanofiltration membrane separation characteristics under different influent water quality conditions and treatment effect were investigated. Through the experimental study of the system, that can get better water quality and greater flux BW30-365 reverse osmosis membranes used in the treatment of electroplating wastewater. NF270-400 type nanofiltration membrane can effectively concentrate the RO membrane concentrated water desalination efficiency is slightly lower, but the water quality to RO water conductance and water production requirements, system recovery to meet the design requirements. BW30-365 reverse osmosis membrane feed conductivity less than 30000μs/cm line, desalination rate can reach more than 95%, higher conductivity is generated salt fouling the desalination rate will ensue upheavals It also lead to a rapid decline in water production water. NF270-400 type nanofiltration membrane under in the water conductivity 35000μs/cm conditions, the the desalting rate was about 50% higher than the conductivity produces salt fouling the desalination rate will ensue drastic changes. The study shows that the operating pressure 1.6MPa-1.8MPa best run state, increase or reduce the pressure will reduce the rate of desalination and water production, indicating that modification nanofiltration membrane state 1.6MPa-1.8 MPa, taking into account cost, 1.6MPa for more reasonable working pressure. Different SDI and turbidity electroplating wastewater pollution experiment for the reverse osmosis membrane, resulting in membrane flux decline in a month at different rates, the use of HCl and NaOH were mixed antiscalant chemical cleaning, when almost no SDI less than 1 cleaning, after cleaning the membrane flux decline to 94.1% of the original membrane flux When SDI is 5:00, and the impact of water turbidity is the main factor in pollution and membrane caused permanent pollution difficult to clean. Chemical cleaning, the higher the temperature, the better the cleaning effect, taking into account the temperature extremes of the film as well as the different RO membrane washing conditions, select the appropriate washing temperature 40 ℃ the NF membrane flushing temperature of 30 ° C is more appropriate. Pilot experiment to test the enterprise the electroplating wastewater system RO water pressure 1.6MPa; NF water pressure 1.6MPa, continuous influent pH in the neutral state, when the RO water conductivity about 4800μs/cm system product water conductivity of less than 200μs/cm COD less than 20 mg / L, the reverse osmosis membrane as a front-end processing back rate of 82.2%, nanofiltration membrane treatment as a back-back rate of 65%, RO NF system integrated back The rate can reach 95%, and achieve project targets.