不同碳源和碳氮比对一株好氧反硝化细菌脱氮性能的影响

利用间歇培养装置研究了好氧条件下丁二酸盐、乙酸盐和苹果酸盐3种不同碳源对好氧反硝化细菌X31脱氮性能的影响,并就不同碳氮比(C/N)条件下菌株X31的反硝化能力展开了研究.结果显示,不同碳源种类对菌株硝酸还原酶活性有明显影响.以丁二酸盐和乙酸盐作为碳源时,其脱氮效果均要明显好于苹果酸盐作为碳源.以乙酸盐作为碳源时菌株的反硝化速率要稍高于丁二酸盐作为碳源,其反硝化速率可以达到11.86 mg·g-1·h-1.不同碳氮比(C/N)条件下,X31菌株的好氧反硝化能力亦不相同.当C/N大于5时,脱氮率能达到90%以上.最适宜的碳氮比是5～6,在此区间能进行完全的反硝化.当C/N在1～14之间变化时,硝酸盐还原基本都发生在菌株生长的第4～10 h,整个反硝化过程中亚硝酸盐浓度一直保持在极低的水平.     

UASBB厌氧氨氧化反应器处理污泥脱水液的影响因素研究

研究基质质量浓度、温度、pH值、HRT和C/N比对厌氧氨氧化脱氮性能的影响.试验水样采用污泥脱水液,控制进水ρ(NH+4-N)/ρ(NO-2-N)为1∶1.32,分别考察了在不同基质质量浓度、HRT、温度、pH值和C/N比的情况下,UASBB厌氧氨氧化反应器的脱氮性能.结果表明,在进水NH+4-N和NO-2-N质量浓度分别为200 mg·L-1和264 mg·L-1、HRT=24 h、温度为30～35℃、pH值为7.5～8.5、C/N比在0.5左右的条件下,厌氧氨氧化反应器的脱氮效果最佳,NH+4-N、NO-2-N和TN平均去除率分别达到75.72%、76.36%和70.19%,TN平均容积负荷可达0.464 kg·(m3·d)-1,COD平均去除率在30%左右.通过合理控制进水基质质量浓度和HRT能够有效地提高厌氧氨氧化反应器的脱氮性能.只有在适宜的温度和pH值范围内,厌氧氨氧化菌才能表现出较高的活性.当进水添加有机物时,厌氧氨氧化反应器中存在反硝化现象,且随着有机物质量浓度的升高,异养反硝化菌的竞争优势逐渐增强,对厌氧氨氧化产生明显的抑制作用.     

巢湖水体氮磷营养盐时空分布特征

在不同汛期对巢湖水体进行了网格化样品采集,研究了巢湖水体中氮磷营养盐的含量与时空分布规律,确定了巢湖水体的主要污染因子.结果表明,巢湖入湖河流中TP、TN和NO-3-N指标均超过了Ⅴ类水标准,南淝河和十五里河中TP、TN、NH+4-N和NO-3-N表现出丰水期低于平水期、枯水期的季节性变化特征,在其他河流则呈现出丰水期高于枯水期、平水期的特征;巢湖湖体氮磷营养盐浓度的分布存在时空差异,西部湖区中氮磷营养盐含量远高于东部湖区;TP、TN和NH+4-N表现出在枯水期高于平水期和丰水期的变化特征,而NO-3-N在丰水期的含量较高;巢湖水体的主要污染因子为TN和NH+4-N,这些污染物从西往东质量浓度不断减少.     

提高污泥浓度对市政污水处理的影响研究

通过减少排泥提高污泥浓度,试验在高污泥浓度情况下,MLVSS的变化与MLSS的关系,以及COD、SS、氨氮的去除和MISS的关系.结果证明MLSS应维持在6 000mg/L以下,并坚持正常排泥比较合适.     

Nitrogen removal from wastewater and bacterial diversity in activated sludge at different COD/N ratios and dissolved oxygen concentrations

The impact of the organic carbon to nitrogen ratio (chemical oxygen demand (COD)/N) in wastewater and dissolved oxygen (DO) concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria (AOB) communities in activated sludge in constantly aerated sequencing batch reactors (SBRs) was determined. At DO of 0.5 and 1.5 mg O₂/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination (above 50%) was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O₂/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O₂/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.     

Mercury bioaccumulation in fish in an artificial lake used to carry out cage culture

As a global toxic pollutant,mercury(Hg)bioaccumulation within food chain could be influenced by human disturbance.Ten typical fish species were collected from Changshou Lake,an artificial lake used to carry out cage fish culture,to investigate the C/N isotopic compositions and Hg bioaccumulation in fish.The results showed that the total Hg(THg)and methylmercury(MeHg)levels in fish muscles((56.03±43.96)and(32.35±29.57)ng/g,wet weight),comparable with those in most studies in China,were significantly lower than the international marketing limit(0.5 mg/kg).Past human input for cage culture in this lake led to abnormal~(15)N enrichment in food chain,as the quantitative trophic levels based onδ~(15)N were different with that classified by feeding behaviors.This phenomenon subsequently demonstrated that it should be considered thoughtfully with respect to the application of the traditional method for understanding Hg bioaccumulation power by the slope of log_(10)[Hg]withδ~(15)N regression in specific water body(i.e.,Changshou Lake).In addition,no significant linear correlation between Hg and body weight or length of some fish species was observed,suggesting that the fish growth in the eutrophic environment was disproportionate with Hg bioaccumulation,and fish length or weight was not the main factor affecting Hg transfer with food web.The occurrence of human disturbance in aquatic system presents a challenge to a better understanding of the Hg bioaccumulation and biomagnification within the food chain.     

新型后置反硝化工艺处理低C/N(C/P)比污水脱氮除磷性能研究

从内碳源有效利用角度出发,开发了新型连续流后置反硝化AOA工艺,将厌氧段混合液按一定比例分流至缺氧段,从而强化缺氧段反硝化除磷作用.进水NH₄⁺-N和PO₄^3--P浓度保持在(38.31±2.03) mg·L^-1和(5.74±0.13) mg·L^-1,在不同运行阶段进水COD分别控制在300 mg·L^-1和250 mg·L^-1,考察了AOA工艺处理低C/N(C/P)比污水过程影响因素.当进水C/N比和C/P比分别为7.41±0.26和52.36±1.25时,通过将SRT由10 d延长到16 d,系统TN和PO₄^3--P去除率分别稳定在65.86%±2.06%和90.00%±3.97%;当进水C/N比、C/P比降至6.14±0.32和43.40±1.37时,在SRT为16 d条件下,将A/O/A体积比由1/3/1调整为1/2/2,TN和PO₄^3--P去除率分别升至69.76%±3.36%和98.73%±1.82%.结果表明,采用控制SRT、调整好氧/缺氧HRT等策略,可保证处理低C/N(C/P)比污水AOA工艺高效稳定运行.     

前置反硝化脱氮系统外加碳源在线控制基础

以低碳氮比(C/N)生活污水为研究对象,对连续流前置反硝化生物脱氮系统外加碳源的控制方法进行了研究,从而能使出水硝酸盐和亚硝酸盐(NO_x-N)的浓度在满足出水水质标准的情况下,尽可能减少外加碳源的投加量.试验结果表明:总回流比大于2碳源不足时,增加总回流比并不能提高脱氮效率;总回流比一定,缺氧区出水NO_x^--N的浓度达到2mg/L左右时,即使碳源投加量成倍增加,TN的去除率提高不多.在对总回流比与投加碳源量的相互关系分析的基础上提出了外加碳源量的控制方案:通过使缺氧区出水NO_x^--N浓度维持在2mg/L左右来控制外加碳源的投加量,总回流比由进水TN及出水NO_x^--N浓度的标准值来确定.该控制方案既容易判断碳源投加的最佳点又能节省碳源的投加量,易于在污水处理实践中实现.     

基于EIO-LCA模型的纯电动轿车温室气体减排分析

纯电动轿车燃料周期的温室气体排放是否低于汽油轿车的排放仍然存在争议.为评价纯电动轿车的温室气体减排效率,此研究利用中国2007温室气体排放EIO-LCA模型分别核算了普通级纯电动轿车和汽油轿车燃料周期的温室气体排放量.结果表明纯电动轿车燃料周期的温室气体排放总量为124gCO2,e/km,汽油轿车相应的排放总量为265gCO2,e/km,纯电动轿车与汽油轿车相比,减排温室气体53%.模型计算结果还表明影响纯电动轿车温室气体排放的主要行业包括电力、热力的生产和供应业与煤炭开采和洗选业等.因此,纯电动轿车温室气体减排应通过优化一次能源结构、提高电网综合效率等方法实现.     

A novel integrated step-feed biofilm process for the treatment of decentralized domestic wastewater in rural areas of China

For wastewater treatment in rural areas, a novel three-stage step-feed wastewater treatment system, combined with a drop-aeration biofilm process, was tested in the laboratory to investigate its performance in removing suspended solids (SS), chemical oxygen demand (COD), NH4+-N, total nitrogen (TN), and total phosphorus (TP). The removal rates of SS, COD and NH4+-N were 90%, 80%, and 90% in efluent concentrations less than 10 mg/L, 50 mg/L and 8 mg/L, respectively. The TP removal rate was less satisfactory....