Potassium Ferrate Removal Of Dissolved Organic Matter In Water And Inhibition Of Trihalomethanes

Dissolved organic matter(DOM)in drinking water is mainly derived from industrial and agricultural wastewater.In addition,the metabolism of microorganisms,plants and algae in the water body will also form DOM.Since DOM is the main precursor of the by-product of trihalomethane disinfection,removing DOM from the source becomes the most effective way to suppress trihalomethane.As an advanced oxidant,potassium ferrate(K₂FeO₄)is considered to have a dual role in water treatment,as both an oxidant and a flocculant.The main research of this thesis is to remove DOM in water through K₂FeO₄pre-oxidation to achieve the purpose of suppressing the generation of trihalomethanes(THMs).This experiment first conducted the decomposition rate of K₂FeO₄in actual water;secondly,explored the effect of K₂FeO₄on the removal of DOM under different reaction conditions;and finally studied the inhibitory effect of K₂FeO₄on THMs after pre-oxidation.The main test results are as follows:(1)When K₂FeO₄is in the actual water,that is,the p H value is about 7.5,the increase in dosage will lead to a longer time for the final K₂FeO₄to completely decompose.However,within the same reaction time,the decomposition rate of a large dosage is relatively faster.In general,the decomposition rate is the fastest in the first 20 minutes and the K₂FeO₄in the water is basically completely decomposed at 120 minutes,and the p H value of the water sample does not change much after the self-decomposition reaction;the addition of Fe(?)obviously promotes the K₂FeO₄in the actual decomposition rate in water is almost completely decomposed when the decomposition rate in the first 1 minute is the fastest 10 minutes,which increases the decomposition rate of K₂FeO₄.This experiment also provided help for the selection of the reaction time in the subsequent K₂FeO₄oxidation removal of DOM.(2)In the experiment of the influence factors of K₂FeO₄removal of DOM in water,when the reaction time is 30 s,the removal effect of DOM is the best.The removal rate of DOC and UV₂₅₄reach 7.7%and 44.8%respectively,and the removal rate will be reduced if it exceeds30 s;the dosage of K₂FeO₄is 25 mg/L When reacting for 30 s,the removal rates of DOC and UV₂₅₄were 14.4%and 55.7%,respectively;in the case of a certain iron content,adding Fe(?)can promote the removal effect of K₂FeO₄on DOM to a certain extent,in Fe(VI)When the molar ratio with Fe(?)is 1:1,the removal rates of DOC and UV₂₅₄reach 18.7%and 54.3%,respectively,which are 8.6%and 6.6%higher than when K₂FeO₄is used alone.(3)According to the quantitative and qualitative analysis of three-dimensional fluorescence,it is found that under the above three influencing factors,they basically have a greater impact on the area representing humic substances,and have a small effect on the area representing soluble microbial metabolites.(4)Selecting the molar ratio of Fe(VI)to Fe(?)at 0:0,1:0,and 1:1 to compare the changes of DOC and UV₂₅₄in different molecular weight ranges.It was found that after the molar ratio of 1:0 and 1:1,the removal effect of DOC was the best when the molecular weight was greater than 30k Da,and the removal rates reached 50%and 62.5%,respectively.When the molecular weight was less than 1k Da,there was no removal effect or even increased;and When the molar ratio is 1:1,when the molecular weight is greater than 3k Da,UV₂₅₄is completely removed,and when the molar ratio is 1:0,when the molecular weight is greater than 10k Da,UV₂₅₄is completely removed.Therefore,the addition of Fe(?)can promote the oxidation treatment efficiency of K₂FeO₄on macromolecular organics.(5)In the test of the influence factors of K₂FeO₄inhibiting THMs,it can be known that when the chlorine dosage is 15 mg/L and the disinfection time is 72 h,the THMs in the raw water can reach the maximum amount of 57?g/L;after the water sample is pre-oxidized by K₂FeO₄Chlorine disinfection is effective for THMFP treatment.When the dosage of K₂FeO₄is 25 mg/L,THMFP is reduced by 37.3%;in the molar ratio of Fe(VI)to Fe(?)When it is0:0.5,THMFP is reduced by 47.9%,and by linearly fitting the values of UV₂₅₄and THMFP,it is found that the two have a certain correlation;the Br^-concentration has a greater impact on THMFP,and the water sample before treatment is accompanied by Br^-as the concentration increases,THMFP and bromine binding factor(BIF)also increase,and the four types of by-products in THMs are obviously converted from chlorinated to brominated by-products.With the increase of Br^-concentration,the THMFP of the treated water samples decreased by56.5%,38%,31.2%,35.65%,31.67%,24.78%,respectively.(6)Finally,it is concluded through the verification test that the pre-oxidation of K₂FeO₄to remove DOM in water is obviously better than the direct removal of THMs produced by K₂FeO₄.After pre-oxidation with K₂FeO₄,the content of THMs is reduced to 33.5?g/L,which is 12.5?g/L lower than that of THMs directly removed by K₂FeO₄.