初沉池对污水中无机悬浮固体的影响

随着生物除磷脱氮工艺的大量使用,初沉池的设置和取消一直在学术和工程界存在争议。以重庆市某污水厂为对象,从对无机悬浮固体(ISS)、COD和TN去除效果的角度探讨了初沉池在污水处理系统的重要性。研究结果表明,在合流制排水体制下,该污水厂进水污染物浓度非常高,COD、SS和ISS的平均浓度分别为560、1 100和780 mg/L;初沉池对COD、SS和ISS的去除率分别为61%、78%和85%,对ISS的去除率比COD高20%左右;污水经过初沉池沉淀之后,ISS/COD从1.7下降到0.7左右,COD/TN从8.0左右下降到4.3,粒径由40μm下降到30μm。初沉池对大粒径的ISS具有较好的去除效果,未能被去除的小粒径ISS容易悬浮在混合液中,降低MLVSS/MLSS。从ISS/COD的削减和保持混合液MLVSS/MLSS正常的角度来讲,初沉池不应取消。     

Culture techniques for three freshwater macroinvertebrate species and their use in toxicity tests

At present only one freshwater invertebrate species (Daphnia magna) is widely used in routine toxicity tests in the United Kingdom. In this paper methods are described for the continuous laboratory culture of three European macroinvertebrates species, the dipteran Chironomus riparius, the amphipod Gammarus pulex and the isopod Asellus aquaticus. Their use as test species to assess both acute and chronic toxicity responses is discussed.     

Effect of organic suspended solids and their sedimentation on the surrounding sea area

A study of sediment contamination was made in one of the 23 specific designated important ports in Japan, the inner part of which had been used as wood pool. The study focused on the relationship between contaminants and organic matter in terms of ignition loss and the impact of the wood pool on the port area. Organic matter exists in the form of suspended solids and deposits. Sediment samples were taken from the mouths of the rivers feeding into Shimizu Port, from the wood pool and from Shimizu Port. Samples within Shimizu Port showed that as the ignition loss decreased with distance from the wood pool, other properties including the concentrations of trace metals, ignition loss and sulfide content also decreased with the distance. In conclusion, Shimizu Port seems to function as a buffer area between the wood pool and Suruga Bay.     

Evaluation of caged freshwater mussels as an alternative method for environmental effects monitoring (EEM) studies

On three occasions between 1998 and 2000, freshwater mussels were collected by divers in Lake Memphremagog during the spring and transplanted to various locations in the St-Fran?ois River (Quebec, Canada). Mussel growth was monitored by comparing total weight and length at the beginning and end of the exposure period. In 1998, mussels were caged for 60 days at 10 stations, including locations receiving treated effluents from three pulp and paper mills. Overall, there was an apparent trend of increased mussel growth from upstream to downstream along the river. However, mussels caged downstream from the effluent discharge of a bleached kraft pulp and paper mill grew more slowly than those caged immediately upstream in the river. In 1999 and 2000, we further investigated the situation in the vicinity of this bleached kraft mill. The measurements again indicated that growth of mussels in the effluent plume from this mill was reduced in comparison to sites upstream. Overall, in terms of growth, the caged mussels responded both positively and negatively to different environmental conditions. Compared with other monitoring approaches used at these sites during the same period, the caged mussel experiment results were consistent with the trends observed with the benthic invertebrate survey but not with the trends observed for fish.     

Effects of suspended solids on cyanobacterial bloom formation under different wind fields

Wind waves and suspended solids (SS) generated by the resuspension of sediments are ubiquitous characteristics of lake ecosystems. However, their effects on phytoplankton remain poorly elucidated in shallow eutrophic lakes. Laboratory experiments were carried out to investigate the responses of Microcystis aeruginosa to SS under static (wind speed of 0 m/s) and breeze (wind speed of 3 m/s) conditions. Results showed that 50 mg/L SS can promote the growth of M. aeruginosa, accelerate the formation of colonies, and increase the floating rate under no-wind conditions. Comparing with static environment, breeze can significantly increase the growth rate of M. aeruginosa and benefit the formation of larger colonies of algae cells. Driven by wind and SS, the buoyancy of the cyanobacteria community in different experimental groups was obviously different. The specific performance was that low SS concentration and breeze were in favor of the floating of cyanobacteria, while high SS concentration went against the floating of algal cells. As a conclusion, wind speed of 3 m/s and 20–50 mg/L SS have a synergistic effect on the formation of cyanobacterial blooms. This study can provide an improved current understanding of bloom formation and turbidity management strategies in shallow eutrophic lakes.

     

Comparative study on the susceptibility of freshwater species to copper-based pesticides

Copper compounds have been intentionally introduced into water bodies as aquatic plant herbicides, algicides and molluscicides. Copper-based fertilizers and fungicides have been widely used in agriculture as well. Despite the fact that copper is an essential element for all biota, elevated concentrations of this metal have been shown to affect a variety of aquatic organisms. Nonetheless, comparative studies on the susceptibility of different freshwater species to copper compounds have seldom been performed. This study was conducted to compare toxicity of copper-based pesticides (copper oxychloride, cuprous oxide and copper sulfate) to different freshwater target (Raphidocelis subcapitata, a planktonic alga and Biomphalaria glabrata, a snail) and non-target (Daphnia similis, a planktonic crustacean and Danio rerio, a fish) organisms. Test water parameters were as follows: pH = 7.4 +/- 0.1; hardness 44 +/- 1 mg/l as CaCO3; DO 8-9 mg/l at the beginning and > 4 mg/l at the end; temperature, fish and snails 25 +/- 1 degrees C, Daphnia 20 +/- 2 degrees C, algae 24 +/- 1 degrees C. D. similis (immobilization), 48-h EC50s (95% CLs) ranging from 0.013 (0.011-0.016) to 0.043 (0.033-0.057) mg Cu/l, and R. subcapitata (growth inhibition), 96-h IC50s from 0.071 (0.045-0.099) to 0.137 (0.090-0.174) mg Cu/l, were the most susceptible species. B. glabrata (lethality), 48-h LC50s from 0.179 (0.102-0.270) to 0.854 (0.553-1.457) mg Cu/l, and D. rerio (lethality), 48-h LC50s 0.063 (0.045-0.089), 0.192 (0.133-0.272) and 0.714 (0.494-1.016) mg Cu/l, were less susceptible than Daphnia to copper-based pesticides. Findings from the present study therefore suggest that increased levels of copper in water bodies is likely to adversely affect a variety of aquatic species.     

Within season and carry-over effects following exposure of grassland species mixtures to increasing background ozone

Few studies have investigated effects of increased background ozone in the absence of episodic peaks, despite a predicted increase throughout the northern hemisphere over the coming decades. In this study Leontodon hispidus was grown with Anthoxanthum odoratum or Dactylis glomerata and exposed in the UK to one of eight background ozone concentrations for 20 weeks in solardomes. Seasonal mean ozone concentrations ranged from 21.4 to 102.5 ppb. Ozone-induced senescence of L. hispidus was enhanced when grown with the more open canopy of A. odoratum compared to the denser growing D. glomerata. There was increased cover with increasing ozone exposure for both A. odoratum and D. glomerata, which resulted in an increase in the grass:Leontodon cover ratio in both community types. Carry-over effects of the ozone exposure were observed, including delayed winter die-back of L. hispidus and acceleration in the progression from flowers to seed-heads in the year following ozone exposure.     

悬浮颗粒物在河道滞留塘系统中的沉降与沉积特性

河道滞留塘系统是以颗粒物沉降为污染物主要净化机理的污染河流净化技术.通过1年的现场试验研究,考察了悬浮颗粒物SS在滞留塘中的沉降和沉积特性.在本试验条件下,随水力停留时间(HRT)延长(HRT为1.5～7 h),SS平均去除率逐渐增加,介于20%～40%之间,而SS去除速率则快速降低,SS去除速率与进水SS浓度成正比关系;不同季节河水中SS的沉降性能有较大差异,冬季河水中有机物含量较低的易沉降颗粒物比例较春秋季河水的为高,滞留塘HRT的选择应以去除易沉降颗粒物为标准,本研究条件下5 h以内是适宜的HRT选择范围.在滞留塘动态运行中,SS的沿程沉积量呈指数规律下降.     

悬浮颗粒物在河道滞留塘系统中的沉降与沉积特性

河道滞留塘系统是以颗粒物沉降为污染物主要净化机理的污染河流净化技术。通过1年的现场试验研究，考察了悬浮颗粒物SS在滞留塘中的沉降和沉积特性。在本试验条件下，随水力停留时间（HRT）延长（HRT为1．5-7h），SS平均去除率逐渐增加，介于20％-40％之间，而SS去除速率则快速降低，SS去除速率与进水SS浓度成正比关系；不同季节河水中SS的沉降性能有较大差异，冬季河水中有机物含量较低的易沉降颗粒物比例较春秋季河水的为高，滞留塘HRT的选择应以去除易沉降颗粒物为标准，本研究条件下5h以内是适宜的HRT选择范围。在滞留塘动态运行中，SS的沿程沉积量呈指数规律下降。     

Evidence of differences in the biotransformation of organic contaminants in three species of freshwater invertebrates

Acute static bioassays were performed using three freshwater invertebrate species (the oligochaete Lumbriculus variegatus, the fingernail clam Sphaerium corneum and the larvae Chironomus riparius) exposed separately to a variety of 14C radiolabelled contaminants. The aim of this work was to investigate if the chemicals remained as parent compounds after the treatments. Chemicals used were 2,4-dichlorophenol; 2,4,5-trichlorophenol; pentachlorophenol; pyrene; Fenpropidin, and Trifluralin. Homogenates of the whole body tissue of each organism were prepared and total radioactivity was measured. Contaminants were then extracted into organic solvents and analysed by high-pressure liquid chromatography techniques. Chromatograms showed that most of the substances extracted were present as parent compounds in S. corneum and in L. variegatus. In contrast, for C. riparius a low proportion of the chemicals was recovered as parent compounds. These results suggest that different metabolic processes could take place in the different species.     

Perfluorooctane sulfonic acid and organohalogen pollutants in liver of three freshwater fish species in Flanders (Belgium): relationships with biochemical and organismal effects

A perfluorooctane sulfonic acid (PFOS) assessment was conducted on gibel carp (Carassius auratus gibelio), carp (Cyprinus carpio), and eel (Anguilla anguilla) in Flanders (Belgium). The liver PFOS concentrations in fish from the Ieperlee canal (Boezinge, 250-9031 ng/g wet weight, respectively) and the Blokkersdijk pond (Antwerp, 633-1822 ng/g wet weight) were higher than at the Zuun basin (Sint-Pieters-Leeuw, 11.2-162 ng/g wet weight) and among the highest in feral fish worldwide. Eel from the Oude Maas pond (Dilsen-Stokkem) and Watersportbaan basin (Ghent) had PFOS concentrations ranging between 212 and 857 ng/g wet weight. The hepatic PFOS concentration was significantly and positively related with the serum alanine aminotransferase activity, and negatively with the serum protein content in eel and carp. The hepatic PFOS concentration in carp correlated significantly and negatively with the serum electrolyte concentrations whereas a significant positive relation was found with the hematocrit in eel. Although 13 organochlorine pesticides, 22 polychlorinated biphenyl (PCB) congeners and 7 polybrominated diphenyl ethers (PBDEs) were also measured in the liver tissue, only PCB 28, PCB 74, gamma-hexachlorocyclohexane (gamma-HCH) and hexachlorobenzene (HCB) were suggested to contribute to the observed serological alterations in eel.     

人工湿地生物降固池对悬浮物及总氮的净化效果

通过植物泥培筛选实验、植物密度实验和水力停留时间优化实验对4种沉水植物进行筛选并研究了植物的最佳种植密度和生物降固装置对水体悬浮物和总氮的净化效果。结果表明：穗花狐尾藻适应能力较强,在北方冬季低温环境下仍能继续生长;种植密度为100株·m-2的穗花狐尾藻对悬浮物的吸附和截留作用最明显;生物降固装置最佳HRT为6~8 h。在HRT为6 h条件下,植物组对悬浮物的去除率为78.6%,比对照组高39%;总氮去除率为8.9%,说明生物降固装置可以有效截留、吸附悬浮物,但在较短HRT条件下对总氮吸附作用不明显。悬浮物达到同样去除效果,生物降固装置比自然沉降需要的时间少2~4 h。同时,种植水生植物的生物降固装置对总氮有一定的去除效果,降低人工湿地进水氮负荷。     

Human exposure to respirable suspended particulate and airborne lead in different roadside microenvironments

The aim of this study is to evaluate the particulate air pollution in selected roadside microenvironments of Hong Kong through an intensive field study dated from January 1997 to February 1997. The study employed the microenvironment monitoring technique to access the exposure of pedestrians to respirable suspended particulate and airborne lead (Pb) at heavily trafficked roadsides. A total of 62 roadside sites in 14 districts covering the most urbanized and densely populated areas were selected. It was found that pedestrians were exposed to a 24 h average of respirable suspended particulate, PM10, and airborne Pb (APb), typically ranged from 25.56 to 337.40 microg/m3 and 70.71 to 285.71 ng/m3, respectively. The average PM10 concentrations at different roadside microenvironments corresponding to urban residential, urban commercial, urban industrial and new town areas were 91.84, 129.08, 83.83, and 118.89 microg/m3 respectively. The corresponding values for APb were 130.01, 143.40, 127.40 and 173.17 ng/m3, respectively. It was found that measurement at EPD nearby rooftop monitoring stations might not reflect the actual roadside PM10 exposure. Most APb field study data was significantly higher than the nearby fixed station data.     

From total suspended solids to molecular biology tools--a personal view of biological wastewater treatment process population dynamics

The development of the tools needed to study the population dynamics of biological wastewater treatment processes is traced from its beginnings in the early 1900s to today's use of molecular biology tools (Oerther and Love, 2003). Examples of the benefits of population dynamics research in improving the performance and aiding the design and operation of biological wastewater treatment processes are given. Some thoughts on future areas of study are presented.     

Systems-level modeling the effects of arsenic exposure with sequential pulsed and fluctuating patterns for tilapia and freshwater clam

The purpose of this paper was to use quantitative systems-level approach employing biotic ligand model based threshold damage model to examine physiological responses of tilapia and freshwater clam to sequential pulsed and fluctuating arsenic concentrations. We tested present model and triggering mechanisms by carrying out a series of modeling experiments where we used periodic pulses and sine-wave as featured exposures. Our results indicate that changes in the dominant frequencies and pulse timing can shift the safe rate distributions for tilapia, but not for that of freshwater clam. We found that tilapia increase bioenergetic costs to maintain the acclimation during pulsed and sine-wave exposures. Our ability to predict the consequences of physiological variation under time-varying exposure patterns has also implications for optimizing species growing, cultivation strategies, and risk assessment in realistic situations.     

The effects of simulated acid rain on the growth of three herbaceous species grown on a range of British soils

Seedlings of winter barley, perennial ryegrass and white clover were grown on a range of British soils for 21-24 weeks and exposed to simulated acid rainfall treatments of pHs 5.6, 4.5, 3.5 and 2.5. Whilst leaves of white clover developed leaf lesions after 18 weeks of exposure to the pH 2.5 treatments, there were no signs of visible injury to the other two species. At harvest, it was noted, for all species, that there was a large amount of variation in the sizes of individual plants and this made it difficult to detect differences between the treatments for plants on an individual soil. However, in combined analyses for all soils, it was found that the treatments had substantial effects on the yields of plants. The yields of both winter barley and clover were highly correlated with rainfall pH, showing substantial reductions in the more acid rains as compared to the pH 5.6 (control) treatment. In contrast, plants of perennial ryegrass produced higher yields of shoots at the most acid (pH 2.5) as compared to the other treatments. It was noted that the pH 2.5 treatment resulted in a generally lower soil pH at the termination of the experiment.     

Assessing the toxicity of sodium chloride to the glochidia of freshwater mussels: implications for salinization of surface waters

Chloride concentrations in surface waters have increased significantly, a rise attributed to road salt use. In Canada, this may be a concern for endangered freshwater mussels, many with ranges limited to southern Ontario, Canada’s most road-dense region. The acute toxicity of NaCl was determined for glochidia, the mussel’s larval stage. The 24 h EC50s of four (including two Canadian endangered) species ranged from 113-1430 mg Cl L⁻¹ (reconstituted water, 100 mg CaCO₃ L⁻¹). To determine how mussels would respond to a chloride pulse, natural river water (hardness 278-322 mg CaCO₃ L⁻¹) was augmented with salt. Lampsilis fasciola glochidia were significantly less sensitive to salt in natural water (EC50s 1265-1559 mg Cl L⁻¹) than in reconstituted water (EC50 285 mg L⁻¹). Chloride data from mussel habitats revealed chloride reaches levels acutely toxic to glochidia (1300 mg L⁻¹). The increased salinization of freshwater could negatively impact freshwater mussels, including numerous species at risk.     

The effects of fenvalerate on different tissues of freshwater fish Cirrhinus mrigala

The histopathological changes of fenvalerate on the gill, kidney, liver and intestine tissues of the Cirrhinus mrigala were determined by light microscopy. The fish were exposed to two sub-lethal concentrations of fenvalerate (1.5-3.0 ppb). The most common gill changes at all concentrations of fenvalerate were epithelial hyperplasia, epithelial necrosis, desquamation and lamellar fusion. Besides, epithelial lifting, oedema, swelling at the tips of secondary lamellae and curling of secondary lamellae were other histopathological changes. Necrosis of tubular epithelium, pycnotic nuclei in the hematopoietic tissue, hypertrophied epithelial cells of renal tubules, narrowing of the tubular lumen, expansion of space inside the Bowman's capsule and contraction of the glomerulus were observed in kidney tissues of fish. Hepatic lesions in the liver tissues of fish exposed to fenvalerate were characterized by congestion, cloudy swelling of hepatocytes and focal necrosis. Atrophy of epithelial cells, necrosis of epithelial cells, desquamation of mucosal epithelium and infiltration of lymphocytes into the lamina propria were detected in intestine tissues of fish after exposure to fenvalerate.