Research On Formation Process Of Trichloronitromethane, Disinfection By-Product In Drinking Water And Its Control Strategies

The disinfection by-products in drinking water have great harm to human health because of the strong carcinogenic, teratogenic and mutagenic effect, therefore, research on its analysis method, formation process and control strategies is of great importance and necessity.A novel method with high accuracy that use methyl tertiary butyl ether (MTBE) as extractant and1,2-dibromopropane as internal standard for the determination of trichloroacetone (TCAce) by gas chromatography mass spectrometry (GC-MS) was established. The recovery rate, relative standard deviation and minimum detection limit of TCAce test method was96.4%～104.8%,3.14%～6.11%and0.92μg/L～1.90μg/L, respectively.The process of L-threonine chloride to TCAce and its influencing factors were evaluated. It was indicated from the formation process that the TCAce amount produced increased with the increase of pH value from5.5to8.5. It was also found that when the chlorine dosage increased from4to16mmol/L, the TCAce formation amount increased. It was also found that when the L-threonine dosage increased from0.5to4mmol/L, the TCAce formation amount decreased. Temperature effect the TCAce formation from L-threonine a lot, especially in the range of10-30℃. The TCAce formation amount was inceased with the increase of temperature. The formation process of TCAce chlorided by L-threonine contained substitution, oxidation reaction, amino diazotation, reduction and a series of complicated reaction.Impregnated modified method using0.1mol/L sodium hydroxide was used to modified the granule activated carbon(GAC) to enhance the removal efficiency and adsorption capacity of TCAce. The surface physical and chemical properties of GAC and NaOH-GAC were investigated, the results indicated that the specific surface area of NaOH-GAC increased by9.47%compared to that of GAC, while the acidic groups (mainly carboxyl group, lactone group and phenolic hydroxyl group) on the surface of NaOH-GAC reduced by29.6%, which revealed that the adsorption capacity of TCAce by NaOH-GAC was enhanced.The results of adsorption tests indicated that when the initial concentration of TCAce solution was20μg/L, the optimum dosage of GAC and NaOH-GAC was0.6g/L and0.8g/L, respectively. When the dosage of adsorbent was0.6g/L, TCAce removal rate by NaOH-GAC was91.39%, which was1.17times higher than that by GAC. The adsorption process of TCAce by the modified GAC could be divided into three phases, which were rapid phase, slow phase and dynamic equilibrium phase. The time of equilibrium adsorption of TCAce by NaOH-GAC was60min earlier than GAC.It was found that the TCAce adsorption by GAC and NaOH-GAC increased with the increase of their dosage and temperature. Original concentration of TCAce had less effect on the TCAce adsorption by GAC and NaOH-GAC. The TCAce adsorption by GAC and NaOH-GAC accorded with the Freundlich adsorption isotherm model and followed the pseudo second-order kinetics model.The TCAce removal rate of iron scraps was pretty high, when the addition of iron scraps and TCAce concentration was120g/L and20μg/L, respectively, TCAce removal rate was70.59%. The concentration of iron scraps and temputure was of great impact on TCAce removal, the removal increased with the increase of iron scraps addition and temputure. Original concentration of TCAce had less effect on the TCAce reduction by iron scraps. The TCAce reduction by iron scraps followed the first-order kinetic model.