南方某市水源臭味物质识别及分布研究

用臭味层次分析法(FPA)、全二维气相色谱飞行时间质谱(GC×GC-TOFMS)结合臭味活性值(OAV)表征,对以SZ、SY、TG水库为代表的南方某市主要水源的臭味类型和臭味物质进行筛查识别。确定主要臭味类型为土霉味,主要土霉味物质为二甲基异莰醇(2-MIB)和土臭素(GSM)。利用优化后的顶空固相微萃取气相色谱质谱(HS-SPME-GC/MS)检测方法对3个主要水源中的2-MIB和GSM进行为期1年的检测分析,结果表明,SY和TG两水库中的2-MIB平均含量分别为48.06ng/L和41.41ng/L,SZ水库未检出。SZ、SY、TG 3座水库中GSM平均含量分别为2.55ng/L、4.89ng/L、4.30ng/L,在2-MIB和GSM两种臭味物质中,2-MIB对水源水土霉味贡献更大,为主要土霉味物质。     

SPME-GC/MS/MS法测定水中2-甲基异莰醇和土臭素

研究了固相微萃取-气相色谱/二级质谱联用法测定水中2-甲基异坎醇(2-MIB)和土臭素(GSM)的方法.确定了最佳固相微萃取条件,NaCl加入量3 g,萃取温度60 ℃,搅拌时间30 min,搅拌速度800 r/min.在优化的仪器条件对臭味物质的测定结果显示,此方法灵敏度高,具有良好的精密度和准确度.2-MIB和GSM的相关系数均大于0.999;检出限及RSD分别为0.2 ng/L、0.4 ng/L和5.86%、6.50%;加标回收率分别为100.6%和92.3%.该方法操作简单省时,可满足水中痕量异臭物质的测定.     

粉末活性炭技术处理水中臭味物质的应用研究

随着水资源日益紧缺、水质恶化,原水臭味问题成为我国给水厂迫切关注的水质问题.经过对B市地表水水源突发臭味问题进行分析,确定2-MIB为水体主要致臭物质.通过臭氧、高锰酸钾预氧化和粉末活性炭对水中2-MIB的去除试验,发现粉末活性炭对其处理效果最佳.原水投加粉末活性炭与现有水厂常规处理 活性炭工艺构成解决臭味问题的双重技术保障.通过实验室吸附试验和中试确定了粉末活性炭投加点位置和投加量等技术参数.在加强滤池反冲洗及部分回流水排放的条件下,原水2-MIB浓度达到100 ng/L时,投加15 mg/L粉末活性炭、20 mg/L聚氯化铝时,可将出厂水2-MIB控制在10 ng/L以下.     

太湖流域某净水厂嗅味物质变化特征研究

为了探讨净水厂中嗅味物质的浓度变化规律与各级处理单元之间的关系,以期为净水厂更加高效地去除水中的嗅味物质提供依据,采用固相微萃取—气质联用技术对太湖流域某净水厂中的2-甲基异莰醇(2-methylisobornel,2-MIB)、土臭素(Geosmin,GSM)、β-紫罗兰酮(β-Ionone,p-Ion)和β环柠檬醛(pCyclocitrial,p-Cyc)4种特征嗅味物质进行检测,并分析比较了净水厂各级处理单元对嗅味物质的去除效果.结果表明:β-Cyc的平均浓度最高,为5.83 μg/L,其次为β-Ion,平均浓度达到41.36 ng/L,2-MIB和GSM的平均浓度相对较低,分别为4.02 ng/L、l.13 ng/L;净水厂处理工艺对2-MIB、β-Cyc、β-Ion和GSM的去除率分别为99.93％、93.73％、64.09％和0;净水厂的处理工艺对嗅味物质具有一定的去除效果,嗅味物质浓度沿着水处理工艺流程呈下降趋势,嗅味物质的去除主要发生在深度处理阶段.     

东太湖水体中嗅味物质分布及网围养殖对其影响

东太湖是太湖流域重要的水源地,苏州市吴江区取水口位于其中,水体中出现异嗅味。为了解东太湖水体中嗅味物质的空间分布及甄别围网养殖可能对其的影响,在东太湖的不同区域设置监测点位,利用GC-MS对水体中的嗅味物质进行监测。结果表明:1)水体中嗅味物质2-甲基异莰醇(MIB)和土嗅素(Geosmin)的浓度分布具有显著的空间异质性,其浓度随距养殖区域距离的增加而递减;2)水体中嗅味物质2-MIB和Geosmin的浓度与温度显著正相关,当温度为最高时,其最大浓度分别达到1121.99 ng/L和34.29 ng/L;3)水温和硝酸盐氮浓度对2-MIB浓度有极显著影响(P 0.01),水温越高,硝酸盐氮浓度越高,2-MIB浓度越高,总磷浓度和硝酸盐氮浓度对土嗅素浓度有显著影响(P 0.05)。网围养殖可能是水体中嗅味物质的一个重要来源,在东太湖及其它水源地治理中应引起高度重视。     

固相微萃取-气质联用法在水体嗅味物质测定中的应用

采用固相微萃取-气质联用法对水体中常见嗅味物质土臭素(GEO)和2-甲基异莰醇(2-MIB)进行分析测定。选取65μm PDMS/DVB纤维萃取头,经实验确定最佳萃取条件:Na Cl投加量为6 g;水浴温度为70℃;萃取时间为30 min。用内标法测定结果显示:GEO和2-MIB在5~900 ng/L范围内标准曲线线性良好,且该法检出限低,对GEO和2-MIB的检出限分别为0.5 ng/L和0.7 ng/L;精密度(RSD)分别为0.31%和0.94%;加标回收率分别为107%和103%,能够满足分析测试要求。     

太湖流域水源地多环芳烃分布、溯源与生态风险评估

利用GC-MS对太湖流域水源地多环芳烃(PAHs)的浓度水平进行监测分析。结果表明,3月水相、悬浮颗粒物和沉积物中PAHs的质量浓度分别为63.5~393.9 ng/L、167~4 358.2 ng/g和940.8~7 398.3 ng/g,分别远高于6月的21.1~64.6 ng/L、125.6~282.3 ng/g和337.3~1 318 ng/g。不同月份单体PAH浓度水平差异较大,可能受控于污染物来源、径流稀释和水动力条件的差异性。特征比值判源结果表明,6月水相和悬浮颗粒物中PAHs主要来源于石油类泄漏和燃烧过程,而沉积物中PAHs在3月和6月均体现为混合源。生态风险评估结果表明,水相、悬浮颗粒物和沉积物中PAHs的生态风险较小,但个别样点单体PAH的含量高于基于生物影响试验的风险评价低值ER-L和ISQV-L,说明存在一定的健康风险,需引起重视。     

顶空固相微萃取-气质联用法测定水中五种嗅味物质的不确定度评定

建立测定水中5种嗅味物质不确定度的数学模型,逐层对不确定度来源进行分析,计算各不确定度分量并合成出标准不确定度和扩展不确定度.当试样中2-异丙基-3 甲氧基吡嗪(IPMP)含量为97.2ng/L时,其扩展不确定度为(97.2±13.7)ng/L包含因子k=2;当试样中2-异丁基-3-甲氧基吡嗪(IBMP)含量为98.8ng/L时,其扩展不确定度为(98.8±13.0)ng/L包含因子k=2;当试样中2-甲基异莰醇(2-MIB)含量为97.4ng/L时,其扩展不确定度为(97.4±14.1)ng/L包含因子k=2;当试样中2,4,6-三氯苯甲醚(TCA)含量为97.3 ng/L时,其扩展不确定度为(97.3±13.7)ng/L包含因子k=2;当试样中土臭素(GSM)含量为100.0 ng/L时,其扩展不确定度为(100.0±14.4)ng/L包含因子k =2.影响测定结果不确定度的主要来源为样品顶空固相微萃取、标准系列溶液配制、内标物的加入,其他因素的影响相对较小.     

包头市画匠营子总水源厂冬季水质异味分析研究

通过对包头画匠营子总水源厂冬季水质进行长期监测分析,认为造成水质异味的主要物质为水源水中含有痕量藻类次生代谢产物(Geosmin、MIB、IPMP、TCA).在对黄河水、水库水进行长期监测的基础上分析得出是由于藻类的大量繁殖造成该水厂出厂水有异臭味.研究结果表明冬季水库藻类的总数及各种属,以绿藻门、硅藻门、隐藻门三大门类为主,其中以绿藻门的小球藻、鼓藻,隐藻门中的卵形隐藻、啮齿隐藻,硅藻门的圆筛藻、星杆藻最为常见.异味明显时,水库藻类数量一直在107个/L以上.还用OLSA-GC法测定了藻类分泌物--痕量致味物质土臭素、地霉素、TCA和IPMP的含量,MIB含量在29～102 ng/L,超出嗅阈值3～10倍;TCA范围为13～59 ng/L,超过其嗅阈值2～9倍;地霉素20～65 ng/L,超过其嗅阈值2～6倍;IPMP9～38 ng/L,超过其嗅阈值4～19倍.研究结果为今后解决包头市冬季饮用水中异味问题提供了基础资料.     

水源水质标准中嗅味标准的研究

在我国现有的《生活饮用水水源水质标准》(CJ3020-93)标准中并未对嗅味做定性和定量的规定。嗅味层次分析方法能够对水样中的嗅味种类以及嗅味强度做出定性和定量化的判断,通过嗅味层次分析方法以及SPME-GC/MS化学分析的结果,给出了饮用水嗅味的推荐值。按不同水源地类型对二甲基异莰醇(2-MIB)的标准进行了研究,综合考虑感官分析和化学分析结果,水厂可处理程度以及消费者可接受情况,给出2-MIB标准的推荐值,一级、二级水源地的标准推荐值为10 ng/L,三级水源地的标准推荐值为50 ng/L。二甲基异莰醇(2-MIB)嗅味标准推荐值的给出在一定程度上对水源地的划分又提供了一个参考依据,开辟了水质感官分析的新思路,为我国城市水源中2-MIB含量的划分提供了参考。     

The effect of applying a pipe-joint lubricant to connect ductile iron pipe on off-flavors in drinking water distribution systems.

This study was used to help define the contribution to taste and odor problems caused by the application of a pipe-joint lubricant to connect ductile iron pipe in drinking water distribution systems. Tyton Joint Lubricant (TJL) was studied. The lubricant produced odors that are continually oxidized by chlorine or oxygen. The mechanism of oxidative rancidity, one of the major causes of food spoilage is the apparent mechanism of oxidation. The odors produced by the lubricant were characterized by a Flavor Profile Analysis (FPA) panel as well as GC/MS and Sensory GC analysis. The most common odors perceived in the TJL water samples for the first six days were waxy/oily and soapy odors with a rancid oil, odor note. The waxy/oily and soapy odors decreased with time in the chlorine medium as the rancid oily odor note increased. Numerous aldehydes, ketones, alcohols and borneol compounds, produced from the lubricants, were tentatively identified and linked to the odors perceived by the FPA panel.     

Synthesis and odour thresholds of mixed halogenated anisoles in water.

Earthy-musty off-flavour compounds in water samples are usually associated with the presence of geosmin and 2-methylisoborneol. However, the presence of 2,3,6- and 2,4,6-trichloroanisoles or other halogenated anisoles can impart objectionable tastes and odours to the water even at very low trace levels. This paper shows the synthesis of non-commercial 2,3,6- and 2,4,6- mixed chloro/bromoanisoles which can be present in bromide rich waters and could also be suspected of imparting earthy-musty off-flavours to the water. All the synthesized compounds were subjected to the flavour profile analysis (FPA) method and their odour threshold concentrations (OTC) in water were carried out giving values in the low ng/L range.     

Treatment of taste and odor material by oxidation and adsorption.

Massive blooms of blue-green algae in reservoirs produce the musty-earthy taste and odor, which are caused by compounds such as 2-MIB and geosmin. 2-MIB and geosmin are rarely removed by conventional water treatment. Their presence in the drinking water, even at low levels (ng/L), can be detected and it creates consumer complaints. So those concentrations have to be controlled as low as possible in the drinking water. The removals by oxidation (O3, Cl2, ClO2) and adsorption (PAC, filter/adsorber) were studied at laboratory and pilot plant (50 m3/d) to select suitable 2-MIB and geosmin treatment processes. The following conclusions were derived from the study. Both of the threshold odor levels for 2-MIB and geosmin appeared to be 30 ng/L as a consequence of a lab test. For any given PAC dosage in a jar-test, removal efficiencies of 2-MIB and geosmin were increased in proportion to PAC dosage and were independent of their initial concentration in raw water for the tested PAC dosages. In comparison of geosmin with 2-MIB, the adsorption efficiency of geosmin by PAC was superior to that of 2-MIB. The required PAC dosages to control below the threshold odor level were 30 mg/L for geosmin and 50 mg/L for 2-MIB at 100 ng/L of initial concentration. Removal efficiencies of odor materials by Cl2, ClO2, and O3 were very weak under the limited dosage (1.5 mg/L), however increased ozone dosage (3.8 mg O3/L) showed high removal efficiency (84.8% for 2-MIB) at contact time 6.4 minutes. According to the initial concentrations of 2-MIB and geosmin, their removal efficiencies by filter/adsorber differed from 25.7% to 88.4%. For all those, however, remaining concentrations of target materials in finished waters were maintained below 30 ng/L. The longer run-time given for the filter/adsorber, the higher the effluent concentration generated. So it is necessary that the run-time of the filter/adsorber be decreased, when 2-MIB or geosmin occurs in raw water.     

Sensory evaluation of the odors produced during bromophenol formation using a multi-level statistical model.

In response to reports of medicinal taste and odor problems in suburban Paris, a lab scale study was conducted to investigate the contribution of different water quality parameters--pH, phenol, bromide, chlorine, temperature and dissolved oxygen levels--on bromophenol medicinal odor formation using the Flavor Profile Analysis (FPA) method. A study of six parameters at 2 levels (64 experiments) analyzed by the FPA method suggests that chlorine at high concentration is more important as a controlling agent than phenol under similar conditions and the ratio of HOBr:Phenol and the time for reaction will control subsequent brominated products of reaction. Results from a three-level statistical model indicate that high pH was associated with lower odor intensities, whereas high levels of chlorine, phenol and temperature were associated with high odor intensities. Potential worst case scenarios of water quality conditions were determined for evaluation by chemical identification and kinetics.     

Effects of chlorine and chloramines on earthy and musty odors in drinking water.

Water treatment plants in the US may operate under the assumption that chlorine masks earthy and musty odors from geosmin and 2-methylisoborneol (MIB) in drinking water. To test this hypothesis, we evaluated the effects of chlorine and chloramines on geosmin and MIB by two sensory analysis approaches--a statistical Pairwise Comparison Test, and Flavor Profile Analysis (FPA). All Pairwise Ranking test statistics were significant (p<0.05); we conclude that panelists can differentiate minor differences in geosmin and MIB concentrations in a Pairwise Comparison Test even in the presence of chlorine. FPA appeared to be more challenging in discerning subtle differences in concentrations of geosmin or MIB than did the Pairwise Comparison Test, and the presence of chlorine (0.5-20 mg/L) and chloramines (3-24 mg/L) confused the panelists (i.e showed a larger error in the intensity of response reported by the panel), but did not necessarily mask geosmin or MIB.     

Occurrence of the Odor Compounds, 2-Methylisoborneol and Geosmin in Eastern Lake Ontario and the Upper St. Lawrence River

Unpleasant tastes and odors in drinking water from the upper St. Lawrence River were investigated in the fall of 1996 and 1997 as the result of increasing taste and odor events in recent years. Taste and odor events resulted in widespread public reaction to the earthy/musty tasting water produced and a need for accurate information to assist water treatment efforts. The presence of geosmin, (trans, trans-1,10-dimethyl-9-decalol) and 2-methylisoborneol (MIB2, 1,2,7,7-tetramethyl-exobicyclo[2.2.1]heptan-2-ol), the most common causes worldwide of earthy and musty odors in water, were investigated in eastern Lake Ontario and the upper St. Lawrence River. Gas chromatography-mass spectrometry was used for quantitation and confirmation of the presence of these compounds in water samples. Both geosmin and MIB2 were detected in river water samples at concentrations ranging from 5 to 20 ng/L and 2 to 25 ng/L, respectively. The compounds were also detected in southern coastal lake water which serves as a source to the St. Lawrence River, but not in mid-lake samples. Similar levels of geosmin and MIB2 were detected in untreated Lake St. Lawrence water, in samples taken following pre-chlorination for zebra mussel control, and in samples taken following conventional treatment at a water filtration plant.     

Characteristics of salt taste and free chlorine or chloramine in drinking water.

Salty taste with or without chlorine or chloramine flavour is one of the major consumer complaints to water utilities. The flavour profile analysis (FPA) taste panel method determined the average taste threshold concentration for salt (NaCl) in Milli-Q water to be 640 +/- 3 mg/L at pH 8. Chlorine and chloramine disinfectants have no antagonistic or synergistic effects on the taste of NaCl, salt, in Milli-Q water. The flavour threshold concentrations for chlorine or chloramine in Milli-Q water alone or in the presence of NaCl could not be estimated by the Weber-Fechner curves due to the chlorine or chloramine flavour outliers in the 0.2-0.8 mg/L concentration range. Apparently, NaCl is not equilibrated with the concentration of ions in the saliva in the mouth and the concentration of free chlorine or chloramines cannot be tasted correctly. Therefore, dechlorinated tap water may be the best background water to use for a particular drinking water evaluation of chlorine and chloramine thresholds. Laboratory FPA studies of free chlorine found that a 67% dilution of Central Arizona Project (CAP) (Tucson, AZ) water with Milli-O water was required to reduce the free chlorine flavour to a threshold value instead of a theoretical value of 80% (Krasner and Barrett, 1980). No synergistic effect was found for chlorine flavour on the dilution of CAP water with Milli-Q water. When Central Avra Valley (AVRA) groundwater was used for the dilution of CAP water, a synergistic effect of the TDS present was observed for the chlorine flavour. Apparently, the actual mineral content of drinking water, and not just NaCl in Milli-Q water, is needed for comparative flavour tests for chlorine and chloramines.     

O_3和O_3/H_2O_2氧化对饮用水中痕量臭味物质的处理效果研究

研究了O3、O3/H2O2深度氧化法对饮用水中的Geosmin、MIB、IBMP、IPMP及TCA等痕量异味物质的去除效能。当O3投加量为4.66mg/L时,对痕量异味物质的去除率按IBMP、TCA、Geosmin、IPMP和MIB的排列,其中对Geosmin的绝对去除量最大,达到了140ng/L。投加O30.43mg/L和H2O210mg/L氧化去除5种痕量异味物质,对IBMP和TCA去除率分别达到75%和67.2%,去除效率较高;但在O3及O3/H2O2这样的投加量下,痕量异味物质尚不能达到标准中对嗅阈值的要求,还需配合后续处理工艺。