Research And Application On Energy Saving Technology Of Reverse Osmosis System Based On Improved Operational Configuration

Reverse osmosis technology has been rapidly developed for seawater desalination,wastewater treatment,and brackish water desalination,but high energy consumption become the most crucial problem for extensive application.This study tried to improve the system configuration and compared energy consumption of DP-RO and CC-RO with traditional configuration based on theory and pilot scale experiment.Then,put forward the concentration reduction of biogas slurry using the reverse osmosis process with CC-RO configuration.In order to evaluate the capacity of energy consumption reduction with different configuration in the actual RO desalination process,this study completed a pilot scale RO desalination experiment with NaCl solution as influent.Under the condition of5000mg/L(NaCl)influent and 50% of recovery,the total energy consumption is decreased from 5.40 MPa·m~3 to 2.90 MPa·m~3 and 3.01 MPa·m~3 respectively with4staged-DPRO and 4staged-CCRO while the configurational energy is reduced from0.26 MPa·m~3 to 0.05 MPa·m~3 and 0.06 MPa·m~3 respectively.And with the influent of35000mg/L,the configurational energy is reduced from 2.67 MPa·m~3 to 0.41 MPa·m~3and 0.43 MPa·m~3respectively with 4staged-DP-RO and 4staged-CC-RO.Therefore,the reduction of configurational energy consumption become more significant.Although a staged DP-RO is much more energy efficient than a single-stage RO,even better than CC-RO,considering the operation difficulty and capital cost,extra pumps,high pressure tubes are needed for lower average water flux.However,with CC-RO configuration,there seemed to be much less increase in capital cost because of the similarity of CC-RO and traditional configuration which only need to change the operation process.Therefore,staged CC-RO is capable of reducing the energy consumption of the RO desalination process while won't significantly increase the capital cost.According to the result of the pilot scale experiment for biogas slurry concentration using DTRO system with closed-circuit configuration,the best applied pressure for the process is between 5-6MPa.The removal rate of COD and TP in the system was kept over 99% and 95% of conductivity and TN can be removed during the process.Due to the concentration of biogas slurry can only reach 1-1.5 times more than initial influent under the applied pressure of 5-6Mpa,closed-circuit configuration has been used to improve the concentration ratio which can reach 6-7 times.In addition,the CCRO process has obvious advantages in resource recovery,and excellent energy saving effect,while it can save 14% energy consumption when the concentration ratio is 4 times.