混凝对二级出水中有机物分布特性的影响

以城市污水处理厂二级出水为研究对象,通过烧杯实验,确定了以三氯化铁(FeCl3)和聚合氯化铝(PAC)为混凝剂时两种混凝剂的最佳投加量,在此基础上采用XAD树脂分离技术和超滤膜法对水中溶解性有机物(DOM)进行分级表征,研究了混凝前后水中DOM的亲疏水特性、分子量分布规律以及比紫外吸收值(SUVA)和E4/E6(A465nm/A665nm)的变化.结果表明,当FeCl3和PAC投加量分别达到30 mg/L和60 mg/L时,可以使出水水质满足《城镇污水处理厂污染物排放标准》(GB18918-2002)中的一级A标准;FeCl3对含碳碳不饱和双键及芳香环的有机物的去除效果优于PAC;FeCl3对小分子有机物的去除效率更高,而PAC对分子量＞100 000的大分子有机物的去除效果优于FeC13;混凝处理对疏水性有机物的去除效果优于对亲水性有机物的去除效果,同时其对酸性物质的去除效率高于对非酸性物质的去除效率.     

水源切换条件下模拟管网铁离子释放控制简

用北京市某供水区域铸铁管段搭建2套模拟管网装置,对水源切换条件下管网铁离子释放的控制进行了研究。实验过程中利用地下水为水源,通过调节进入管网的水中氯浓度为1.0~1.1 mg/L,溶解氧浓度为7~8 mg/L,经过40 d运行后,管垢成分主要为α-FeOOH和Fe₃O₄。切换地表水源后,新的管垢组成更有助于铁氧化物中铁的氧化还原重新达到平衡,从而可以有效减少水源切换条件下铁离子的释放,管网出水浊度也得到很好的控制,保持了管网水质稳定性。     

控氧生物膜系统对微污染水体的脱氮性能

通过控制生物膜系统溶解氧(DO)浓度分别为0.5~1 mg/L(Ⅰ)、1~2 mg/L(Ⅱ)、2~3 mg/L(Ⅲ),研究在微污染城市河道水体中实现短程硝化反硝化的可行性。研究表明,在3个系统中,化学需氧量(COD)、氨氮(NH+4-N)和总氮(TN)的平均去除率分别稳定在62.3%、38.6%和38.2%(工况Ⅰ),65.5%、59.4%和28.2%(工况Ⅱ),66.1%、77.3%和22.8%(工况Ⅲ)。系统中各形态氮素含量及其变化情况分析表明,在具有一定NH+4-N去除率前提下,控制体系处于低DO浓度(1 mg/L),亚硝酸盐氧化菌(NOB)生长及活性受到抑制,NO-2-N明显累积,经反硝化作用直接转化为氮气(N2),实现了微污染城市河道水体中的短程硝化反硝化。     

Differential Sensitivity of a Coccal Green Algal and a Cyanobacterial Species to Dissolved Natural Organic Matter (NOM) (8 pp)

Background

and Aim. In non-eutrophicated freshwaters, humic substances (HS) pose chemical stresses on aquatic organisms and, hence, separating sensitive from less sensitive or even tolerant species. One of the stresses, identified so far, is the reduction of photosynthetic oxygen production and reduction in growth in freshwater macrophytes and algae. In a previous paper, it has been shown that even closely related coccal green algae responded differently upon identical stress by HS, which is consistent with the hypothesis above. Due to their much simpler cellular ultrastructure, cyanobacteria are supposed to be more sensitive to HS exposure than eukaryote should be. One coccal green algal species (Desmodesmus communis) and one cyanobacterium (Chroococcus minutus) were exposed to four natural organic matter (NOM) isolates. One NOM has been isolated from a brown water lake (Schwarzer See) in Brandenburg State; three were obtained from a comprehensive Scandinavian NOM research project and originated from Norway (Birkenes), Finland (Hietajärvi), and Sweden (Svartberget).

Methods

Cultures of D. communis and C. minutus were obtained from the Culture Collection of Algae, Göttingen, and maintained in a common medium. The cultures were non-axenic. The algae and cyanobacteria were exposed under identical conditions to environmentally realistic NOM concentrations. Cell numbers were counted microscopically in Neugebauer cuvettes in triplicates. To avoid limitation by nutrient depletion, the experiments were terminated after 14 to 15 days. Until culture day 12, no growth limitation has been observed in the controls.

Results

All NOM isolates modulated the growth of the algae and cyanobacteria. During the early culture days, there was a slight growth promotion with the coccal green alga and to a much lesser degree with the cyanobacterium. Yet, the major effect were significant reductions in cell yield in both primary producer cultures. C. minutus was much more affected than D. communis. This applies particularly to the three tested Scandinavian NOM isolates, which were effective at concentrations even below 1 mg L-1 DOC.

Discussion

The growth promoting effect may be due to an increase in bioavailability of some trace nutrients in the presence of NOM, the release of some growth promoting substances by microbial or photochemical processing of the NOM, and/or a hormetic effect. The growth reducing effect can be explained as a herbicide-like mode of action that affects the photosystem II most prevalent by blocking the electron transport chain, absorption of electrons, or production of an internal oxidative stress after processing the bioconcentrated HS. Furthermore, it may be postulated that also photo-toxicity of these HS in the algal cells contributes to the overall toxicity; however, experimental evidence is lacking so far.

Conclusions

Upon exposure to HS, cyanobacteria appear to be much more sensitive than coccal green algae and respond in growth reduction. This high sensitivity of cyanobacteria to HS may explain phytoplankton patterns in the field. Eutrophic, humic-rich lakes do not support the cyanobacterial blooms characteristic of eutrophic, but humic-poor lakes. In the humic-rich systems, raphidophytes or, less frequent, specific coccal greens are more common. Obviously, cyanobacteria appear to be unable to make advantage of their accessory pigments (phycocyanin) to exploit the reddish light prevailing in humic-rich lakes.

Recommendation

. At present, no effective structure can be figured out which may be responsible for the adverse effect on the cyanobacterial species. It is reserved to future research whether or not HS may be applied more specifically (for instance, with elevated moieties of the effective structures) as a natural geochemical to combat cyanobacterial blooms.

     

PAC与粘土矿物混凝去除颤藻及残余铝形态研究

研究了PAC与不同粒径的天然粘土矿物复合混凝去除给水中的颤藻。结果表明,两者复合除藻效果显著优于单加PAC。当PAC浓度为12 mg/L,矿物浓度为24 mg/L,粒径为160目时,除藻效果最好,浊度和叶绿素a去除率分别为98.2%和100%。两者复合后PAC形态含量都发生了变化,悬浮态铝含量相对增加,溶解态铝含量相对减少,总残余铝量减小。     

Sewage treatment by vermifiltration with synchronous treatment of sludge by earthworms: a low-cost sustainable technology over conventional systems with potential for decentralization

Earthworms’ body works as a ‘biofilter’ and they have been found to remove the 5 days’ BOD (BOD₅) by over 90%, COD by 80–90%, total dissolved solids (TDS) by 90–92%, and the total suspended solids (TSS) by 90–95% from wastewater by the general mechanism of ‘ingestion’ and biodegradation of organic wastes, heavy metals, and solids from wastewater and also by their ‘absorption’ through body walls. Earthworms increase the hydraulic conductivity and natural aeration by granulating the clay particles. They also grind the silt and sand particles, increasing the total specific surface area, which enhances the ability to ‘adsorb’ the organics and inorganic from the wastewater. Intensification of soil processes and aeration by the earthworms enable the soil stabilization and filtration system to become effective and smaller in size. Suspended solids are trapped on top of the vermifilter and processed by earthworms and fed to the soil microbes immobilized in the vermifilter. There is no sludge formation in the process which requires additional expenditure on landfill disposal. This is also an odor-free process and the resulting vermifiltered water is clean and disinfected enough to be reused for farm irrigation and in parks and gardens G. Bharambe—GU & Research Assistant (Under Rajiv K. Sinha), U. Chaudhari—GU (Worked on vermiculture project).     

A Tool for Modeling the Winter Oxygen Depletion Rate in Arctic Lakes1

Abstract: Many arctic lakes freeze completely in winter. The few that retain unfrozen water for the entire winter period serve as overwintering fish habitat. In addition to serving as fish habitat, water in arctic lakes is needed for industrial and domestic use. Permits for water extraction seek to maximize water use without impacting dissolved oxygen (DO) levels and endangering fish habitat. The relationship between lake volume, winter DO budget, and extraction of water through pumping has historically not been well understood. A management model that could estimate end‐of‐winter DO would improve our understanding of the potential impacts of different management strategies. Using under‐ice DO measurements (November to April) taken from two natural lakes and one flooded gravel mine on the North Slope of Alaska, a physically based model was developed to predict end‐of‐winter DO concentration, water‐column DO profiles, and winter oxygen depletion rate in arctic lakes during periods of ice cover. Comparisons between the measured and model‐predicted oxygen profiles in the three study lakes suggest that the depth‐based DO modeling tool presented herein can be used to adequately predict the amount of DO available in arctic lakes throughout winter.     

Evaluating Cover Crops (Sudex,Sunn Hemp,Oats) for Use as Vegetative Filters to Control Sediment and Nutrient Loading From Agricultural Runoff in a Hawaiian Watershed1

Abstract: A study was conducted to determine the effects of three land covers (sunn hemp –Crotalaria juncea, sudex, a sorghum‐sudangrass hybrid –Sorghum bicolor x S. bicolor var. sudanese, and common oats –Avena sativa) planted as vegetative filter strips on the reduction of sediment and nutrient loading of surface runoff within the Kaika‐Waialua watershed on the island of Oahu, Hawaii. Runoff samples were collected and analyzed for total suspended solids (TSS), total dissolved solids (TDS), phosphorous, and three forms of nitrogen (nitrate, ammonium, total nitrogen). Study results show that during seven out of 10 runoff events, the three cover crop treatments significantly reduced TSS as compared to the fallow treatment. Average removal efficiencies were 85, 77, and 73% for oats, sunn hemp, and sudex, respectively, as compared to the fallow treatment. Nutrient concentrations were low with phosphorous concentrations, lower than 1 (μg/ml) for all treatments, and total nitrogen (TN) concentrations below 7 (μg/ml) except in the sunn hemp treatment, where TN concentrations were less than 10 (μg/ml). Results of analysis of TDS showed that the cover crop treatments did not decrease dissolved solids concentrations in comparison with the fallow treatment. Analysis of nutrient concentrations in runoff samples did not detect any significant decreases in phosphorous, nitrogen, ammonium, or TN concentrations in comparison to the fallow treatment. However, a significant increase in TN concentrations in the sunn hemp treatment was detected and showed the nitrogen fixing capacity of sunn hemp. No treatment effects on runoff volume were detected, and runoff volumes were directly correlated with rainfall amounts showing no crops significantly impacted soil infiltration rates. These results were attributed to extremely low soil hydraulic conductivities (0.0001‐7 cm/day at the soil surface, 15 and 30 cm below the soil surface). This study showed that cover crops planted as vegetative filters can effectively reduce sediment loads coming from idle and fallow fields on moderately steep volcanically derived highly weathered soils.     

稻鸭、稻鱼共作对稻田P素动态变化的影响

以稻鸭和稻鱼生态系统为研究对象,通过大田试验研究了稻田P的动态变化及转化规律,及其对环境的影响。结果表明,施P后土壤和田面水P含量立即达到最大值,一周后迅速降低。相对于空白（CK）,养鸭处理（RD）和养鱼处理（RF）田面水总P浓度、溶解P浓度、土壤速效P含量和水稻吸P量显著增加,而土壤全P含量有所增加。研究还表明,水稻吸P量与田面水溶解P、土壤速效P显著相关。对田面水P素径流流失的潜在环境效应分析表明,施P后的一周左右是控制P素流失的关键时期;由于养鸭养鱼能提高稻田P含量,在稻鸭、稻鱼共作期间,要注意避免农田排水和防止因降雨引起的田面水外溢。同时,由于鸭子和鱼能提高土壤有效养分含量,降低化肥的施用量,进而降低了化肥损失所造成的环境危害。     

改进沉淀法在溶解性无机碳稳定同位素测定中的应用研究

水体中溶解性无机碳(Dissolved inorganic carbon, DIC)的稳定碳同位素比值(δ¹³C_DIC)是揭示碳循环过程的重要技术指标。DIC的分离和富集是测定δ¹³C_DIC的基础,也是影响δ¹³C_DIC测定准确度的主要过程之一。沉淀法和气体法均为常用的DIC分离和富集方法。相比于气体法,沉淀法操作流程简单,适用性较强,在δ¹³C_DIC测定过程中具有广阔的应用前景。然而,基于沉淀法的DIC分离和富集过程中常存在碳稳定同位素分馏问题。为此,本研究在综合气体法和沉淀法优缺点的基础上,以超声时间,水浴温度和氮气吹扫速率为自变量,以δ¹³C_DIC的理论值与实测值之间绝对误差的最小化为目标,采用响应面法对传统NaOH-BaCl₂沉淀法进行了改进。基于改进沉淀法测定的δ¹³C_DIC理论值与实测值之间的...