【作者】 张胜利；

【导师】 刘丹；

【作者基本信息】 西南交通大学 ， 市政工程， 2010， 博士

【摘要】 垃圾渗滤液中有机污染物种类众多,不仅含有大分子难生物降解有机物,而且还含有许多有毒难生物降解的小分子有机物,这将降低甚至抑制生物处理中微生物的活性。为此,本文以成都市长安垃圾填埋场的渗滤液为研究对象,在对其中有机污染物进行较全面分析的基础上,从理论上提出高浓度有机废水厌氧可生化性的新指标,并就其适用性与传统的可生化性指标进行了对比分析。采用石灰沉淀-混凝与氧化法组合对垃圾渗滤液中的有机污染物进行预处理,阐明了去除含量较低的难生物降解有机物对提高渗滤液可生化性的重要性；考察了次氯酸钠氧化降解垃圾渗滤液中典型有机物的影响因素及途径。本文通过将超声波辅助萃取引入样品的预处理,与传统的振荡萃取相比,明显提高了萃取效率。利用C-MS分析仪,就不同极性色谱柱对有机污染物分析结果的适用性开展实验。结果表明：极性柱比较适于测定垃圾渗滤液中极性大的有机酸、醇类等物质,非极性柱能提高低含量烷烃、酯类等物质的检出率。长安垃圾填埋场的渗滤液在试验阶段为早期渗滤液与晚期渗滤液的混合液,因此,两种柱子配合使用非常必要。基于理论分析,提出CODCH4/COD值作为废水厌氧可生化性的评价指标,确定了CODCH4/COD值表示厌氧可生化性的数值界限。同时,在BMP分析的基础上,采用CODCH4/COD值考察了垃圾渗滤液的厌氧可生化性,并与BOD5/COD值评价结果进行对比。研究显示,CODCH4/COD值与BOD5/COD值用于垃圾渗滤液可生化性的评价时,得出的结论具有相似性,但CODCH4COD值略大于BOD5/COD值。究其原因：好氧条件下,总的生化耗氧量(BODu)小于理论完全需氧量(COD)；厌氧条件下,有机物完全去除时CODcH4等于理论完全需氧量。此外,BOD5测试时间仅5d,而BMP测试时间一般在30d以上,从而使微生物有足够的时间去适应废水水质,故能较好地反映废水的可生化性。进一步的GC-MS分析表明,垃圾渗滤液中有机污染物的种类和性质直接影响其生化性能。在可生化处理的渗滤液A中(BOD5/COD=0.3～0.4),检出的有机污染物约90%为有机酸类物质；在不易生化处理的渗滤液B中(BOD5/COD<0.15),检出的有机污染物烷烃类约占50%。但无论是BOD5/COD值较低的渗滤液B,还是BOD5/COD值较高的混合渗滤液A,在进行生物处理之前都有必要先通过物化法将其所含的有毒有机污染物去除或降低到适当的浓度范围,以改善后续工艺的运行状况。本文以垃圾渗滤液A作为多级预处理的研究对象。在石灰沉淀-混凝法预处理部分,由于饱和石灰水本身碱性不高且渗滤液具有一定的缓冲作用,所以调节pH值时加入适量的NaOH有助于石灰沉淀作用。相对于FC和FS, PAC为较佳的絮凝剂。助凝剂PAM和PAC配合使用不但增大了渗滤液COD的去除率,而且有利于絮体的沉降。采用GC-MS法对石灰沉淀-混凝预处理前后渗滤液中有机污染物的分析表明,石灰沉淀-混凝预处理可以去除渗滤液中部分有机污染物,特别是含量较低的难生物降解有机物,进而提高渗滤液的可生化性。与此同时,表征渗滤液中难生物降解有机物的指标A260的分析结果也表明预处理后该类物质可去除约48.67%。为了将垃圾渗滤液中有毒且难生物降解的小分子有机物去除或降低到适当的浓度范围,实验对石灰沉淀-混凝预处理出水进行氧化处理。考察了pH值、氧化剂用量、反应时间和反应温度等对NaClO、Ca(ClO)2、KMnO4氧化处理效果的影响,并筛选出较优的氧化剂NaClO。采用NaClO进行正交试验时,试验结果表明：影响次氯酸钠氧化作用的主次顺序为NaClO折合有效氯用量>反应时间>反应温度,且次氯酸钠用量对处理效果有显著影响。氧化预处理后渗滤液中有机污染物的GC-MS分析显示,渗滤液中低含量有机污染物的谱峰经氧化处理明显下降的同时,有机污染物的总离子流图上部分短链脂肪酸的峰高增加。这归因于氧化剂NaClO将渗滤液中的部分有毒或难生物降解有机污染物转化成一系列小分子有机物,从而提高了渗滤液的可生化性。最后,以垃圾渗滤液中的典型有机污染物苯酚为对象,分别在无氨氮体系和氨氮体系中考察了NaClO处理苯酚废水的氧化特性,探讨了相应的反应途径。实验结果表明：无氨氮体系中,NaClO氧化降解苯酚时氯化中间产物氯酚有且仅有5种,它们分别是2-MCP、4-MCP、2,6-DCP、2,4-DCP和2,4,6-TCP。在试验所取的pH值范围6-9内,同一氯酚在不同pH条件下随反应时间增加表现出相似的变化趋势,但不同pH条件下浓度变化速率存在一定差异,且弱碱性条件下有利于苯酚连续氯化反应的进行。加氯量的增大不仅有利于苯酚的氯化,而且有利于苯酚氯化中间产物的转化和氧化降解。在含氨氮的苯酚废水中加入NaClO,氨氮将与苯酚发生竞争反应。折点加氯曲线表现为当氯与氨氮质量比由5.35上升到27.67时,氨氮去除率的变化趋势滞后；而余氯量则不断减小,没有折点出现。随着氨氮浓度增加,苯酚的氧化降解受到抑制：一方面,苯酚的去除率不断下降；另一方面,体系中检洲到一系列氯酚中间产物。这些氯酚中间产物至少有2种(2-MCP和4-MCP),至多有5种(2-MCP、4-MCP、2,6-DCP、2,4-DCP和2,4,6-TCP)。因此,在氨氮体系中加入NaClO氧化降解苯酚时将有利于大大降低THMs和HAAs等有害副产物的生成量。实验结果对NaClO处理含氨氮的难生化或有毒的有机废水具有一定的参考价值。更多还原

【Abstract】 The sanitary landfill is the main treatment technology for municipal solid waste disposal currently. Landfill leachate generated at a landfill contains high concentration of organic pollutants, not only the recalcitrant ones with macromoleculars, but also toxic ones with small moleculars. All above will reduce or even inhibit the activity of microorganisms in biological treatment. Therefore, the leachate of Chang’an landfill in Chengdu was collected to research in this experiment. Based on a comprehensive analysis of organic pollutants by GC-MS, new anaerobic biodegradability index for high concentration organic wastewater was proposed in theory, and whose applicability was compared with the traditional biodegradability index. Landfill leachate was pretreated by the combination of lime sedimentation, coagulation and oxidation method for removing organic pollutants. The importance of removing low content of refractory organic pollutants for improving leachate biodegradability was illustrated. The influencing factor and reaction pathway were also studied when phenol, a typical organic matter in leachate, was oxided by sodium hypochlorite (NaClO).Organic pollutants in leachate were extracted by ultrasonic with CH2Cl2 and determined by GC-MS. Compared with the traditional liquid-liquid extraction, ultrasonic extraction could improve extraction rate of organic pollutants effectively. Capillary column stationary phase was researched on GC-MS measuring in order to offer an accurate method for the measure and analysis of organic matter in leachate. The results of study were as follows:polar capillary column HP-1NNOWAX was applicable for the analyse of polar organic pollutants such as carboxylic acids and alcohols, which were the major components of early landfill leachate. Non-polar capillary column HP-1MS could improve detectable rate and credibility of organic pollutants such as alkanes and esters whose content was low in early leachate and high in old leachate. Because the Leachate of Chang’an landfill in Chengdu was a mixed leachate, polar capillary column and non-polar capillary column should be used together.On the basis of theoretical analysis, that CODCH4/COD was regarded as wastewater’s anaerobic biodegradability index was presented, and the bound of numberical value was laid down. At the same time, the anaerobic biodegradability of landfill leachate was appraised by CODCH4/COD through biochemical methane potential (BMP) test. When the anaerobic biodegradability index respectively were CODCH4/COD and BOD5/COD, a similar conclusion was obtained. But CODCH4/COD was greater than BOD5/COD for the same sample. The possible explanation was that total biochemical oxygen demand (BODu) was smaller than total chemical oxygen demand (COD) in aerobic condition, and with organic pollutants converted completely into methane CODCH4 was equal to COD in anaerobic condition. In addition, the test time was only 5 days for BOD5 and above 30 days for BMP where microbial flora had enough time to adapt to wastewater. Thus CODCH4/COD was feasible for the biodegradability evaluation of wastewater such as landfill leachate. Further GC-MS analysis showed that the type and nature of organic pollutants had an direct effect on leachate biodegradability. In high biodegradability (BOD5/COD=0.3～0.4) leachte A, the detected organic pollutants in leachate were mainly composed of carboxylic acids and their content was about 90%. While in low biodegradability (BOD5/COD<0.15) leachte B, the detected organic pollutants in leachate were mainly composed of alkanes and their content was about 50%. In spite of the high BOD5/COD value, mixed leachate A should be pretreated by physic-chemical methods before biological treatment like leachate B for increasing biodegradability.This study selected landfill leachate A as research subject of multiple pretreatment. Lime sedimentation and cogulation was used at the first stage. Because of the weak alkaline of saturated limewater and buffer action of landfill leachate, adding some NaOH was helpful for the lime sedimentation. Compared to ferric chloride(FC) and ferric sulfate(FS), poly aluminium chloride(PAC) was the better flocculant. The combined use of aid flocculating polyacrylamide(PAM) and PAC not only increased the removal rate of COD, but also was helpful to the sedimentation of flcos. The organic matter in leachate A which was pretreated before and after was analyzed by GC-MS. The results showed that some refratory organic compounds, in particular low content of them, could be removed by lime sedimentation and coagulation. Meanwhile, removal of UV260 absorbance which characterize refractory orgaic matter in leachat was 48.67% after pretreatment.For further decreasing the concentration of small molecular recalcitrant or toxic organic pollutants, chemical oxidation method was used for the effluent of limewater sedimentation and coagulation pretreatment. The effect of pH, oxidant dose, oxidation time and reaction temperature on the preoxidation of NaCIO, Calcium hypochlorite [Ca(ClO)2] and potassium permanganate (KMnO4 was respectively investigated. Contrast to Ca(C10)2 and KMnO4, NaClO was the best oxidant. Orthogonal experiments were designed to optimize the oxidation conditions of NaCIO based on the single affected factor. The results discovered that the influences of operating factors followed the order of oxidant dose>oxidation time> reaction time. And NaCIO dose had a drastic effect. GC-MS analysis showed that with peak height of low content orgaic pollutants decreased obviously, peak height of some small aliphatic acid increased in TIC of orgaic pollutant in leachate. The cause was that NaClO transformed some recalcitrant or toxic compounts into biodegradable products, or even to CO2.Phenol was a typical organic pollutant in landfill leachate. The degradation of phenol by oxidation using sodium hypochlorite were respectively investigated with ammonia nitrogen(NH3-N) and without NH3-N. And the reaction pathway during the oxidation processes were deduced. The results showed that there were only five chlorophenols such as 2-monchlorophenol(2-MCP),4-monchloropthenol(4-MCP),2,6-dichlorophenol(2,6-DCP), 2,4-monchlorophenol(2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) without NH3-N. In the range of 6-9, the variation of same chlorophenol concentration with reaction time showed similar trend, but the reaction rate was different at different pH. And the successive chlorination process could be facilitated in slightly alkaline and alkaline media. The increase of chlorine dose was not only beneficial to the chlorination of phenol, but also the conversion and degradation of chlorination products. In NH3-N system, there was a competion between ammonia and phenol after sodium hypochlorite was added to wastewater. Breakpoint chlorination curve was as follows:When the chlorine/ammonia weight ratio (Cl/N) rose from 5.35 to 27.67, the trend of NH3-N removal lagged behind and residual chlorine continuously decreased with no discont point. With increasing NH3-N concentration, the degradation of phenol was inhibited:on the one hand, the removal rate of phenol declined; on the other hand, a series of chlorophenols whose amount and sort showed an increase before decreasing were detected. Analysis of products by HPLC revealed that chlorophenols were only two chlorophenols(2-MCP and 4-MCP) at least, and five chlorophenols(2-MCP, 4-MCPl,2,6-DCP,2,4-DCP and 2,4,6-TCP) at most.2-monchlorophenol and 4-monchlorophenol were the highest activity of forming trihalomethanes (THMs), While 2,6-dichlorophenol,2,4-monchlorophenol and 2,4,6-trichlorophenol were the highest activity of forming haloacetic acids (HAAs).The experimental results provided certain reference value for dealing with organic wastewater with low biodegradability or toxicity by sodium hypochlorite in NH3-N.更多还原