MBR短程硝化反硝化处理高氨氮废水影响因素的研究

采用AOMBR处理模拟高氨氮废水,研究了短程硝化反硝化的效果,试验表明：在DO为1．0mg／L-1．5mg／L,系统温度为28℃,pH控制在7．5到8．6之间,进水NH3-N在598．2mg／L-701．3mg／L时,能够迅速启动反应器,在其他工况稳定不变的条件下,探讨了pH、温度和DO等对系统短程硝化稳定运行的影响,并探讨了此过程的影响机理。整个实验过程中,pH和进水氨氮的浓度能够短暂的影响亚硝酸盐的积累,但是并不能长久的使之稳定运行。在形成短程硝化的过程中膜污染逐渐加剧,经过清洗之后膜通量并不能完全恢复。     

膜生物反应器处理生活污水的实验研究

实验采用一体式膜生物反应器处理生活污水，实验表明：当污泥浓度为6000mg／L，DO为3．0mg／L以上，进水pH值为7．0—8．5，温度为7—13℃。HRT为8h的条件下，膜生物反应器对COD、BOD，悬浮物、氨氮、总氮、总磷的去除率分别为95％、98％、100％、97％、60％-80％、34％-54％。同时发现，膜生物反应器内部存在部分同步硝化反硝化的条件；对TP的去除率较低，主要是由于系统排泥较少。     

亚硝化SBR反应器快速启动过程的控制条件优化

以模拟城市生活污水为处理对象,采用SBR反应器,在低DO浓度条件下,成功快速启动了亚硝化反应工艺,并对启动过程中的影响因素及实现过程进行研究。反应过程中控制反应器主要参数:DO为0.5~0.7 mg/L,pH为7.2~7.5,温度30~33℃,曝气时间6 h,通过循序递增的氨氮浓度(35~85 mg/L)间歇交替进水,经过33天的稳定运行成功实现了亚硝化的快速启动并且实现亚硝态氮积累率90%以上。考察了SBR亚硝化启动过程的影响因素。研究结果表明,DO直接影响亚硝化进程,当DO平均浓度约为0.5 mg/L时,亚硝酸盐氧化菌的活性得到恢复;在SBR周期试验中,pH、DO浓度与短程硝化密切相关,可作为亚硝化过程的控制参数。     

控制ORP实现连续流反应器部分亚硝化稳定运行

利用ORP在线监控设备,研究了控制ORP值实现连续流部分亚硝化反应器稳定运行的可行性,并使出水水质满足厌氧氨氧化需求.结果表明,在亚硝氮与氨氮比值、温度和pH值恒定的条件下,反应器内ORP值波动主要由于DO浓度波动引起.在稳定的亚硝化系统中,当ORP值大于250mV左右时,反应器出水亚硝氮与氨氮比值大于2.1;当ORP值控制在150mV左右时,反应器出水亚硝氮与氨氮比值稳定在1.2~1.3之间.ORP值控制在120mV时,反应器出水亚硝氮与氨氮浓度比值为0.9~1.06.将ORP值控制在150mV时,随着进水氨氮浓度由300mg/L提高至813mg/L,反应器出水亚硝氮与氨氮比值基本维持在1.1~1.3之间.但随之增加的游离氨浓度易导致亚硝化菌活性抑制.因此,在低氧环境下ORP作为连续流部分亚硝化反应器亚硝化程度的控制指标,其灵敏度和精度明显优于DO监测设备.     

pH控制生物膜移动床反应器完全亚硝化的研究

接种硝化污泥以优势菌种法挂膜,在DO浓度为1.5～2.0 mg/L,温度为(30±1)℃,HRT为24 h的条件下,以pH控制启动移动床完全亚硝化生物膜反应器,并研究了氨氮负荷(NLR)和水力停留时间(HRT)对系统稳定性的影响.结果表明,在进水氨氮浓度为150 mg/L的情况下,pH控制在7.7～8.2,经过10 d驯化生物膜系统达稳定的完全亚硝化状态,氨氮转化率达96%以上,亚硝酸盐积累率高于95%;NLR(以NH4 -N计)从0.15 kg/(m3·d)提高到0.24 kg/(m3·d)基本不影响完全亚硝化的稳定性,氨氮转化率高于90%,亚硝酸盐积累率始终维持在96%左右;低NLR下,延长HRT由于过度曝气导致硝化类型改变为完全硝化,然而缩短HRT仍可恢复为亚硝化.     

常温限氧条件下SBR反应器中的部分亚硝化研究

常温下(14.1～24.2℃)以二级出水(NH 4-N 30～100 mg/L)为原水,在限氧条件下(DO为0.3～0.4 mg/L)的SBR反应器中研究了适合ANAMMOX工艺进水的部分亚硝化工艺.ANAMMOX反应器进水要求NH 4/NO-2=1/1.31,即仅有一部分氨氮形成亚硝酸盐.研究中通过控制进水碱度,以在线DO趋势线为指示,实现部分亚硝化,最终获得NH 4-N/NO-2-N合适比例的出水.当约57%的氨氮转化为亚硝酸盐时,同等比例的HCO-3/NH 4消耗会导致pH值的自然下降.当pH值下降到一定程度时,氨氧化细菌代谢速率的减小导致了耗氧速率(OUR)的急剧下降,DO趋势线就会出现突跃的特征点(本研究以DO突跃至1.0 mg/L为判别),指示出部分亚硝化反应的终点.试验对30～100 mg/L范围内4种氨氮浓度条件下部分亚硝化的最佳碱度进行了研究.结果表明,本试验中进水碱度与氨氮浓度的比率是影响部分亚硝化工艺出水亚硝化比率(NO-2,NH 4)的重要因素,通过对进水碱度的控制完全可以实现向ANAMMOX反应器提供进水的部分亚硝化工艺.     

混合污泥接种的厌氧氨氧化处理污泥脱水液的启动

采用UASB反应器,接种由好氧颗粒污泥、厌氧颗粒污泥、氧化沟活性污泥及短程硝化活性污泥组成的混合污泥,以污泥脱水液经短程硝化处理后水质为进水,在温度(30±0.2)℃, pH值7.3~7.9,初期进水氨氮、亚硝氮容积负荷分别为0.07, 0.10kg/(m3×d)条件下,经过24d运行,氨氮和亚硝氮得到稳定同步去除,186d时TN去除负荷达0.99 kg/(m3×d).启动初期,氨氮、亚硝氮进水浓度分别为20,30mg/L,二者浓度随去除量增加而逐级增加,最高分别达到157,216mg/L;启动过程中,系统受到O2抑制以及O2和亚硝氮基质的连续抑制,分别经过了约10d和30d才得以恢复. 厌氧氨氧化(ANAMMOX)反应与反硝化反应可以共存于系统中,产气量与总氮去除呈正比关系,可及时地指示系统运行状态,对气体成分检测,氮气含量在99.8%.在稳定期ANAMMOX反应呈pH值升高而碱度略有降低.接种混合污泥、低基质负荷启动ANAMMOX,可30d内实现稳定的氨氮和亚硝氮同步去除,180d左右启动成功.     

亚硝化-厌氧氨氧化联合工艺处理高含氮废水的研究

采用实验室规模的亚硝化-厌氧氨氧化联合工艺,研究其对高含氮、低C/N废水的处理能力.结果表明,亚硝化反应器的水力停留时间控制在1.0d时,亚硝化活性比较稳定,进水氨氮浓度对其影响不大.进水氨氮浓度在400～600 mg/L时,出水亚硝酸氮浓度都在260～280 mg/L,可以通过控制进水氨氮浓度调节出水亚硝酸氮/氨氮的比率.亚硝化反应器出水的亚硝酸氮/氨氮的比率对厌氧氨氧化脱氮率有重要的作用.当进水氨氮浓度为480 mg/L时,出水中亚硝酸氮/氨氮的比率为1.2左右,进入厌氧氨氧化反应器的氮物质去除率达到     

生物转盘系统中短程硝化的实现

在生物转盘反应器接种普通好氧污泥,在进水COD浓度为300mg/L,氨氮浓度为15mg/L,pH7.5～8.0,室温条件下启动试验,挂膜成功后对盘面以表层异养菌为主的生物膜层进行亚硝酸盐氧化菌的驯化,通过不断提高进水氨氮负荷和控制较低的C/N,系统硝化反应经历了由弱→强→弱的变化,而氨氧化反应不断得到强化。64d时,当进水N/C比为3.75,COD和氨氮浓度分别为40mg/L和150mg/L,氨氮面积负荷为7.46g/m·2d,HRT=3.16h时,出水亚硝氮累积率达到56.7%,系统中实现了短程硝化反应,随着系统的稳定,亚硝氮平均累积率为80%,最高达95.8%;驯化过程中生物膜厚度由0.2cm增加到0.5cm,颜色也由浅黄色变成黄褐色,镜检发现微生物种类变少,钟虫和累枝虫等消失,膜体中间由大量的丝状体连接。     

低碳氮比条件下膜生物反应器处理高氨氮废水时稳定亚硝化过程的建立

以人工配制高氨氮低碳氮比(C/N)废水为进水,采用膜生物工艺,通过控制亚硝化池内温度为28~30℃,溶解氧浓度为0.5 mg/L,水力停留时间为12 h,pH为7.8~8.0,进水氨氮浓度为200 mg/L、CODCr为40 mg/L,在亚硝化池中成功实现了C/N为1∶5条件下废水的亚硝化。经过14 d的运行时间,污泥龄控制在100 d,在膜生物反应器(MBR反应器)中得到了稳定的亚硝酸盐氮积累。将氨氮浓度分别提高至400和800 mg/L的情况下,其亚硝化菌的耐受浓度负荷冲击能力均较强。     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb,Puntius gonionotus,exposed to the nominal concentration of 0.06 mg/L Cd for 60 d,were assessed for histopathological alterations(gills,liver and kidney),metal accumulation,and metallothionein(MT)mRNA expression.Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae,vacuolization in hepatocytes,and prominent tubular and glomerular damage in the kidney.In addition,kidney accumulated the highest content of cadmium,more than gills and liver.Expression of MT mRNA was increased in both liver and kidney of treated fish.Hepatic MT levels remained high after fish were removed to Cd-free water.In contrast,MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water.The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.     

Seed selections for crystallization of calcium phosphate for phosphorus recovery

Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.