Study On The Technology Of Pretreatment With Seawater Desalination

With the development of economy and the progress of society, mankind's demand for water is increasing. Meanwhile, human unreasonable exploitation and utilization of water resources caused that many countries and regions are now lack of water seriously in different degrees. Water shortage has become the world's second largest environmental problem. Therefore, the development of seawater desalination technology is of great importance to solve the crisis of water resources. In recent decades, distillation and reverse osmosis desalination has received widespread attention as the main desalination methods in the world. In consideration of the water quality difference, reasonable pretreatment for seawater is necessary before it ended into the desalination system. Thus, study the pretreatment technology system of RO and distillation desalination to improve the feed seawater quality, thus to ease the corrosion of distillation equipment and the fouling of RO membrane, is of far-reaching significant for the promotion of desalination industrialization.The technology of treating seawater by immersed UF was investigated in the paper. Results showed that both direct UF and coagulation/UF could achieve high quality filtrate with SDI15 less than 2.0 and turbidity less than 0.2NTU. When the coagulation was added before UF, the number of granules in the seawater of UF inlet was decreased under the appropriate flocculant dosage. The recovery rate of UF membrane SF was enhanced, the cake layer of membrane surface after filtering was loose and porous, the attenuation of UF membrane specific flow (SF) was slowed, the variation of membrane pore size distribution was little compared with direct UF. Which indicated that the coagulation not only ensure good water of UF, but also relieve its pollution. In addition, The technology of treating seawater by external pressure UF was discussed. The water quality, the variation of transmembrane pressure (TMP), the choice of flux, the effect of cross flow to TMP, and the variation of recovery rate of TMP.Because the desalination plant used aluminum alloy as the material of heat exchange in distillation desalination is corroded easily by heavy metal ions. The experiment studied the technology of removing iron ion from seawater by ion trap which filled with aluminum alloy packing. The aluminum alloy was screened out by potentio-dynamic polarization test technology. Then 4×4mm dixon packing with effective specific surface area was processed. Subsequently, the ion trap which filled with dixon packing was finished to study the influence of seawater velocity, initial iron ions concentration, salinity, pH on removing iron ions from seawater. Results showed that the ion trap device could provide high removal ratio for iron ion above 95%. Finally, a bigger ion trap plant was finished. The result was desired after a certain time experiment.