英语翻译
3.3.Effect of coagulation on organic matter
The level of the organic matter was measured as potassium permanganate (KMnO4) demand,DOC and absorbance at 254 nm.The process removed the background organics to less than the recommended goal (3 mg/1 as KMnO4 demand) as show in Fig.5.The effluent of the sand filtration showed a small reduction in CODMn because there is no sediment after the coagulation,while UF effluent showed a good reduction in CODMn for its ability to remove turbidity and particles.We can see from Fig.4 that 40 mg/1 alum is the optimum dosage for CODMn removal.
The different dosages of added coagulants may not only affect the UF flux but also the rejection characteristics for substances in the water,especially for organic macromolecular compounds with molecular weights from 0.5 to 100 KDa,such as humic and tannic acids,polysaccharides and proteins.Fig.6 shows the removal of DOC as a function of alum dose for Songhuajiang River raw water with a DOC of 10 mg/1.A 30-40% reduction in DOC was observed with DOC removal increasing as the alum dose increased.
Although DOC concentration is the accepted measure of DOM content in natural waters,UV254 absorbance is often used as a surrogate for DOC concentration.Fig.7 shows the reduction of UV254 absorbance with water samples after sand filtration and after UF.
SUVA at 254 nm is an indicator of the humic content of water [12].The principle behind this measurement is that UV-absorbing constituents will absorb UV light in proportion to their concentration.Waters with low SUVA values contain primarily non-humic organic matter and are not amenable to enhanced coagulation.On the other hand,waters with high SUVA values generally are amenable to enhanced coagulation [ 13].Fig.8 shows the effect of coagulation on SUVA variation.The sources of water used in this research were less than 2.0 1/mg.m,and the SUVA of ultrafiltrated water is higher than that of raw water.