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题名: 饮用水深度处理过程中溴酸根控制技术的研究
作者: 李伟伟
学位类别: 博士后
答辩日期: 2015-08
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 陈卫平 ; 强志民
关键词: 溴酸根 ; 臭氧 ; 过氧化氢 ; 氨氮 ; 紫外 ; 给水处理Bromate ; Ozone ; Hydrogen peroxide ; Ammonia nitrogen ; UV ; Water treatment
学位专业: 生态学
中文摘要:       由于工农业和生活污水的污染,我国许多城市的饮用水源面临着非常严峻的形势。为了保证用水安全,许多水厂采用了臭氧(O3)—生物活性炭深度处理工艺以进一步去除水体中的有机物。但对于易受海水侵袭的沿海地区,其地表水或地下水中往往含有较高浓度的溴离子(Br−)。Br−可被臭氧氧化生成潜在致癌物溴酸根(BrO3−),制约着臭氧相关技术的应用。本研究针对上海某水厂臭氧生物活性炭工艺中BrO3−生成的风险,考察了在臭氧氧化过程中投加过氧化氢(H2O2)和氨氮(NH3-N)两种药剂工艺控制BrO3−生成的效果及可行性,以及UV/H2O2这一臭氧替代技术的效果和可行性,以期为生产实践提供借鉴。
      利用模拟水样和该水厂砂滤出水探讨了Br−浓度、臭氧投加量、温度、pH及有机物含量对臭氧氧化过程中BrO3−生成的影响。高pH 促进BrO3−的生成,但因为自然水体的缓冲能力,水源水质pH 常年稳定,因此可以忽略其对实际水体BrO3−生成的影响。TOC 与Br−竞争消耗臭氧,所以TOC 越高BrO3−生成越少。高水温会促进BrO3−的生成,但考察该水厂进水Br−的季节变化,水温则是个有利因素,因为Br−浓度高时水温低,水温高时Br−浓度低。臭氧投加量越大,BrO3-生成越多,因为臭氧活性炭的主要目的是去除有机物,所以控制BrO3−生成不能依靠降低臭氧投量。初始Br−浓度越大,溴酸根生成越多。初始Br−浓度大于40g/L 时生成的BrO3−超标(常温20oC,臭氧浓度2.3 mg/L)。总之,虽然上述因素都对BrO3−的生成有很大影响,但对实际生产而言,很多因素如pH、TOC 和温度都是不可或不易改变的,所以在臭氧投量一定的条件下,重点关注初始Br−浓度即可。结合文献和本研究,建议进水Br−浓度大于40 g/L 时进行BrO3−的控制。
    以该水厂砂滤出水为实验水样(人工调节初始Br− 350 g/L),发现H2O2 的加入可有效抑制BrO3−的生成。H2O2/O3(液相中质量浓度比值)为0.25 时(H2O2投加量0.6 mg/L),BrO3−抑制率为59.6%;当H2O2/O3 ≥0.5(H2O2 投加量≥1.2mg/L)时,BrO3
−抑制率达100%。H2O2的加入进一步降低了出水的UV254和TOC,但提升了水体的三卤甲烷生成势(THMsFP),特别是低H2O2 投加量下。综合考虑BrO3−和THMs 两类消毒副产物,建议采用较大的臭氧和H2O2 投加量。该水厂本底氨氮浓度较低,NH3-N 的投加(0.2−1.5 mg/L)可有效抑制BrO3−的生成。BrO3−抑制率与NH3-N 投加量之间无明显相关关系,低剂量的NH3-N(0.2−0.5mg/L)即可取得较好的BrO3−抑制效果。NH3-N 的加入对臭氧氧化有机物的影响不明显,虽然UV254 有所降低(< 30%),但出水TOC 升高且荧光SF(Synchronous fluorescence scanning)扫描显示有机物结构在氨氮加入前后保持不变。综合考虑BrO3−和THMs 两类消毒副产物以及生活饮用水卫生标准中对氨氮和硝氮浓度的
限定,建议氨氮投加量为0.5 mg/L。
    采用UV/H2O2 对水厂砂滤出水进行氧化,在实验参数范围内(UV 剂量0−3000 mJ/cm2,H2O2 投量1−10 mg/L)均未发现BrO3−的生成,Br−浓度也没有改变。在UV 剂量500 mJ/cm2 和H2O2 投加量5 mg/L 时,出水UV254 和TOC 分别降低34%和21%,随后氯消毒过程中的THMsFP 降低了50%。改变水中的氨氮浓度(0−1.2 mg/L)和Br−浓度(80、380g/L),发现出水UV254 和TOC 基本不变,THMs 由于NH3-N 的加入显著降低。此外,UV/H2O2 高级氧化工艺还可以有效降解多种具有内分泌干扰效应的农药及农药代谢物等特殊污染物(甲萘威、残杀威、涕灭威、乐果、甲基对硫磷、甲草胺、毒草安、除草定和乙撑硫脲),适用于上海含高浓度Br−水源水的深度处理。
英文摘要:       Because of the industrial, agricultural pollution and domestic sewage, the drinking water sources in many cities are facing a very severe situation. In order to ensure the safety of drinking water, ozone-biological activated carbon (O3-BAC), as an advanced treatment technology following conventional treatment processes, has been extensively applied in many drinking water treatment plants (DWTPs), to further remove organics in water. However, the surface water and groundwater near the coastal areas, which are vulnerable to the invasion of seawater, often contain high concentrations of bromide ions (Br−). Bromate (BrO3−), a potential carcinogenic by-product, will be generated from ozonation of Br− and thus limits the application of ozonation technologies. O3-BAC was applied in the studied DWTP in Shanghai, and the concentration of BrO3− in the effluent has a risk to exceed the sanitary standards for the drinking water quality. Therefore, the addition of hydrogen peroxide (H2O2) or ammonia nitrogen (NH3-N) before ozonation was tested to study its effect on
inhibiting BrO3− formation. As an alternative technology, UV/H2O2 was also examined for its feasibility, in order to provide useful reference for practice.
      The effects of initial Br− concentration, ozone dose, temperature, pH and dissolved organic matter (DOM, expressed by total organic carbon (TOC)) on BrO3− formation during ozonation were examed in simulated water and sand filtered water, respectively. BrO3
− formation increased as pH rose. However, the effect of pH change on BrO3− formation could be neglected, as water pH maintained quite steady due to the buffering capacity of natural waters. The presence of organics reduced the formation of BrO3− because of the competitive reaction against Br− for O3. Both water temperature and Br− concentration changed with seasons, which made water temperature unfavorable for BrO3− formation. Water temperature became low when Br− concentration was high in winter, and the concentration of Br− became low when temperature was high in summer. The increase of ozone dose promoted BrO3− formation. But the reduction of BrO3− formation could not be realized by decreasing ozone concentration, as sufficient ozone was necessary for the removal of organics.BrO3− formation also increased as the initial Br− concentration rose. The concentration of BrO3− exceeded maximum contaminant level (MCL, 10 g/L) when
Br− concentration was higher than 40 g/L in sand filtered water at room temperature (O3: 2.3 mg/L). In summary, pH, TOC and temperature were either unadjustable or difficult to adjust, so the initial Br− concentration was more important under certain ozone doses. It is suggested that BrO3− should be monitored and controlled at Br− concentration > 40 g/L in raw water.
      The addition of H2O2 effectively inhibited BrO3− formation in sand filtered water, at an initial Br− concentration amended to 350 g/L. The inhibition efficiencies reached 59.6% and 100% when the mass concentration ratios of H2O2/O3 were 0.25 and > 0.5 respectively. The UV254 and TOC also decreased after addition of H2O2, however the formation potential of thihalomethanes (THMsFP) in the effluent increased especially at a low dosage of H2O2. Considering the formation of both BrO3− and THMs, a relatively large dose of O3 and a high ratio of H2O2/O3 were generally needed. NH3-N addition also inhibited BrO3− formation on condition that the background ammonia concentration was low. There was no significant correlation between BrO3− inhibition efficiency and NH3-N dose, and a small amount of NH3-N (0.2−0.5 mg/L) could effectively inhibit BrO3− formation. The oxidation of organics seemed unaffected by NH3-N addition. Though UV254 in the effluent slightly decreased, TOC increased and the structure of organics reflected by synchronous
fluorescence scanning (SF) remained almost unchanged before and after NH3-N addition. Considering the formation of BrO3− and THMs, and the MCL for NH3-N regulated by the drinking water standards, the optimal dose of NH3-N was suggested to be 0.5 mg/L.
      Neither BrO3− formation nor variation of Br− concentration was found in UV/H2O2 oxidation of the sand filtered water with a UV dose range of 0−3000 mJ/cm2 and a H2O2 dose range of 1−10 mg/L. UV254 and TOC were decreased by 34% and 21%, respectively, with 500 mJ/cm2 UV doase and 5 mg/L H2O2 . THMsFP was decreased by 50% in subsequent chlorination process. The change of NH3-N and Br− concentrations had no effect on UV254 and TOC removals. THMsFP was obviously decreased by NH3-N addition. Moreover, many pesticides including their metabolites,e.g. carbaryl, propoxur, aldicarb, dimethoate, parathion-methyl, alachlor, propachlor, bromacil and ethylenethiourea, could be effectively degraded by UV/H2O2, which makes UV/H2O2 feasible as an advanced treatment technology for water with a realtively high concentration of Br− in Shanghai.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34488
Appears in Collections:环境水质学国家重点实验室_学位论文
城市与区域生态国家重点实验室_学位论文

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Recommended Citation:
李伟伟. 饮用水深度处理过程中溴酸根控制技术的研究[D]. 北京. 中国科学院研究生院. 2015.
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