Zirconium toxicity assessment using bacteria,algae and fish assays

Our contribution to Zr environmental hazard, arrived at by means of bioassays on bacteria, microscopic algae and fish, confirms the hypothesis that Zr has low toxicity. Toxic effects revealed with the Microtox test may be attributed to pH rather than specifically to Zr (5 min. EC₅₀ > 4.3 mg L^?1). Fish assays also confirmed the low toxicity of Zr (96-hr LC₅₀ > 20 mg L^?1; 96 hr minimal stress concentration > 20 mg L^?1; Mutagenicity (Fluctuation test) and genotoxicity (S.O.S. Chromotest) assays failed to show any DNA-related effects linked to this metal. Only the algal assays (ATP energy stress) demonstrated genuine toxicity at Zr concentrations between 1.3 and 2.5 mg L^?1.     

Reduction in tolerance to progressive hypoxia in the central stoneroller minnow following sublethal exposure to phenol

Acute exposure of the central stoneroller minnow to sublethal levels of phenol was found to decrease the ability of this species to tolerate hypoxic conditions as indicated by the dissolved oxygen (DO) concentration at which loss of equilibrium occurred. For fishes acclimated at 7.5 °C, loss of equilibrium occurred at progressively higher DO levels as the phenol exposure concentration was increased from 0 to 12 mg phenol L^?1. Mean DO concentrations at which loss of equilibrium occurred ranged from 2.33 ± 0.10 mg O₂ L^?1. for the control group (0 mg phenol L^?1. to 2.76 ± 0.14 mg O₂ L^?1. (at 12 mg phenol L^?1. Loss of equilibrium also occurred at progressively higher DO levels in fish acclimated at 23 °C, but only after an initial decrease among the 6 mg phenol L^?1. test fish in the loss of equilibrium DO concentration. At 23 °C, loss of equilibrium occurred at DO levels ranging from 1.3 ± 0.09 mg O₂ L^?1. (6 mg phenol L^?1. to 2.33 ± 0.16 mg O₂ L^?1. (12 mg phenol L^?1. These data indicate that acute exposures to sublethal levels of phenol can have significant effects on the ability of the stoneroller minnow to tolerate conditions of low DO, and the results agree with the previously reported relationship between phenol toxicity and DO levels.     

一株耐盐苯酚降解酵母菌的分离及降解特性研究

从化工厂污泥中分离到一株酵母菌 ,初步鉴定为德氏酵母属 (Debaryomycessp ) ,命名为Gb。该菌株可以在 0～ 2 0 %Na2 SO4环境中生长 ,并能以苯酚为唯一碳源和能源。其苯酚降解最适浓度为 1 0 0 0mgL-1 ,最适Na2 SO4浓度为 5 %,最适pH和温度分别为 5 5和 30℃ ,在 2 5 0ml三角瓶中最适装液量为 1 0 0ml。当Na2 SO4盐浓度为 5 %、苯酚浓度为 1 0 0 0mgL-1 时 ,最适条件下培养 3天即能降解 95 %的苯酚。本文还对其耐盐机理进行了初步研究 ,发现细胞内海藻糖含量随外界盐浓度增加而增加 ,表明Debaryomycessp 在高盐条件下能以海藻糖作为渗透调节物质。     

The Influence of Water Hardness, pH, and Suspended Solids on Nickel Toxicity to Larval Fathead Minnows (Pimephales promelas)

Nickel (Ni) is an ubiquitous, naturally occurring metalthat is associated with metal mining and other industrialactivities. Despite elevated Ni concentrations reportedfor many industrial receiving waters, Ni receives littleresearch attention addressing factors influencing itstoxicity to freshwater fish. This study examined theinfluence of water hardness, pH, and total suspended solids(TSS) in soft, reconstituted water on Ni toxicity to larvalfathead minnows (Pimephales promelas). Increasingwater hardness from 20 to 140 mg L^-1 (as CaCO₃) reduced acute Ni toxicity by 5-fold (96-h LC50s 0.45 and 2.27 mg Ni L^-1, respectively). Low pH had a slight protective effect against Ni toxicity relative to neutral pH conditions. At pH 5.5, the 96-h LC50 was 0.69 mg Ni L^-1, compared to 0.54 mg Ni L^-1 at pH 7.0. However,Ni toxicity was significantly reduced at pH 8.5 where the 96-h LC50 was 2.21 mg Ni L^-1. These results were explainedon the basis of Ni speciation. Total suspended solids also reduced Ni toxicity (expressed as 96-h LC50s) from 0.35 to 1.12 mg Ni L^-1 over a TSS range of 10 to 100 mg L^-1.This reduction of toxicity due to TSS is significant becausemine effluents often have a combination of elevated TSS andmetals. The ameliorative effect of TSS was not as significantas high hardness or pH probably because there is a TSS threshold, after which physical irritation to fish gills counteracts any protective effect conferred by TSS. This finding is relevant to choices made in design of mine effluenttreatment systems; i.e., there may be an optimum range ofTSS concentrations that protect aquatic biota againsteffects of metals that remain after treatment.     

Toxicity of Sb and Cu in Sewage Sludge to Terrestrial Plants (Lettuce,Oat, Radish), and of Sludge Elutriate to Aquatic Organisms (Daphnia and Lemna) and its Interaction

Antimony (Sb) and Copper (Cu) are two metals of major concern in sewage sludge. Antimony because its use in society is increasing and this might lead to increased Sb concentrations in sludge. Copper because its total volume in use in society is large and because of corrosion from water pipes it is most difficult to reduce the Cu concentrations in sludge. Fresh digested sewage sludge was spiked with Cu or Sb and the sludge was cultivated with oat (Avena sativa), lettuce (Lactuca sativa) or radish (Raphanus sativus). Elutriates from the cultivated sludge were tested for toxicity with Lemna minor (7-d growth) and Daphnia magna (48 h immobility). Before cultivation the elutriates were toxic to Lemna and Daphnia due to high concentrations of ammonia (NH₃) and nitrite (NO₂ ^-). Cultivation decreased the concentrations of both NH₃ and NO₂ ^-, thereby reducing the impact of these compounds in the toxicity tests. Cultivation also decreased the metal concentrations and pH. Daphnia magna was the most sensitive test organism in this study with a 48 h EC₅₀ of 1130 mg Cu kg^-1 dry wt and 5 mg Sb kg^-1 dry wt in elutriates from sludge cultivated with oat. In sludge cultivated with radish the 48 h EC₅₀ was 1700 mg Cu kg^-1 dry wt and 22 mg Sb kg^-1 dry wt. The effect of Cu could be predicted by pH and Cu concentrationin the elutriate, but the effect of Sb could not solely be explained by its concentration in the elutriate.     

Attempts to derive EC50 values for heavy metals from land-applied Cu-, Ni-, and Zn-spiked sewage sludge

We established a field trial to assess the impacts on soil biological properties of application of heavy metal-spiked sewage sludge, with the aim of determining toxicity threshold concentrations of heavy metals in soil. Plots were treated with sludges containing increasing concentrations of Cu, Ni and Zn in order to raise the metal concentrations in the soil by 0-200 mg Cu kg⁻¹, 0-60 mg Ni kg⁻¹ and 0-400 mg Zn kg⁻¹, and were then cultivated and sown in ryegrass-clover pasture and monitored annually for 6 years. All biological properties measured (soil basal respiration, microbial biomass C, and sulphatase enzyme activities), except phosphatase activity, increased in all plots over the duration of the experiment. Consequently, it was only possible to assess effects of heavy metals across time if, each year, all data for each metal were normalised by expressing them as percentages of the activities measured in an un-sludged control plot. When this was done, no significant effects of increasing heavy-metal concentrations on basal respiration, microbial biomass C or respiratory quotient (qCO₂) were observed, although total Cu and soil solution Cu were significantly negatively related to microbial biomass C when it was expressed as a proportion of soil total C. None of the properties measured were affected by increasing Ni concentrations. Phosphatase and sulphatase activities were significantly negatively related to increasing Zn concentrations, but not usually to increasing Cu unless they were expressed as a proportion of total C. A sigmoidal dose-response model was used to calculate EC₂₀ and EC₅₀ values using the normalised data, but generally, the model parameters had very large 95% confidence intervals and/or the fits to the model had small R² values. The factors primarily responsible for confounding these results were site and sample variations not accounted for by the normalisation process and the absence of any data points at metal concentrations beyond the calculated EC₅₀ values. In the few instances where reasonable EC₂₀ values could be calculated, they were relatively consistent across properties, e.g., EC₂₀ for total Zn and phosphatase (330 mg kg⁻¹), total Zn and sulphatase (310 mg kg⁻¹), and EC₂₀ for total Cu and sulphatase (140 mg kg⁻¹) and total Cu and microbial biomass C (140 mg kg⁻¹), when both sulphatase and microbial biomass C were expressed as a proportion of total C. Our results suggest that Cu and Zn at the upper concentrations used in this experiment were possibly having adverse effects on some soil biological properties. However, much higher metal concentrations will be needed to accurately calculate EC₂₀ and EC₅₀ and this may not be easily achievable without many applications of sewage sludge, even if the sludge is spiked with heavy metals.     

Uptake,transport and assimilation of 15N-nitrate and 15N-ammonium in tea (Camellia sinensis L.) plants

¹⁵N studies were conducted using hydroponically grown tea (Camellia sinensis L.) plants to clarify the characteristics of uptake, transport and assimilation of nitrate and ammonium. From the culture solution containing 50 mg L^-1 N0₃-N and 50 mg L^-1 NH.-N, the uptake of NH₃-N after 24 h was twice as high as that of NO₃-N, while the uptake of N0₃-N from the culture solution containing 90 mg N0₃-N and 10 mg NH₃-N was twice that of NH₄-N. The presence of 0.4 mM Al had no significant effect on the N0₃-N and NH₄-N uptake from the culture solutions containing 50 mg L^-1 N0₃-N and 50 mg L^-1 NH₄-N, 90 mg L^-1 N0₃-N and 10 mg L^-1 NH₄-N or 99 mg L^-1 N0₃-N and 1 mg L^-1 NH₄-N. Transport of N0₃-derived N to young leaves was much more rapid than that of NH₄-derived NO₃ and NH₄-derived N was largely retained in the roots and lower stem. Young and mature shoots separated from the roots absorbed more N0₃-N than intact plants. Nitrate assimilation occurred in both, roots and young as well as mature leaves. Internal cycling of N0₃-derived Nand NH₄-derived N from one root part to another part was not appreciable after 28 h, suggesting that a longer of time is required for cycling in woody plants.     

Utilization of created wetlands to upgrade small municipal wastewater treatment systems

Created wetlands offer a low cost, low maintenance, and practical alternative for upgrading secondary municipal wastewater treatment systems. The removal efficiencies, effects of seasonal temperature variations, and effects of increased loading rates on contaminant removal within such a system was studied by Auburn University researchers at a created wetland site in Hurtsboro, Alabama. The 0.16 ha system consisted of a two cell wetlands planted with cattails (Typha latifolia), bulrush (Scirpus validus), arrow duck potatoes (Sagitaria latifolis), burr reeds (Spargaminum eurycarpun), water pennywort (Hydrocotyl ranunculoides), and parrotfeather (Myriophyllum brasiliense). Testing occurred from January through September of 1988 at hydraulic loading rates of 169, 289, and 345 m³ ha^?1 d^?1. The monthly average total suspended solids influent: effluent mg L^?1 concentration ratio during the study period was 135:19 while the monthly average total BOD₅ influent: effluent mg L^?1 concentration ratio was 38:8. Once the system stabilized, the monthly average total BOD₅ effluent concentration remained essentially constant over the range of average BOD₅ loading rates employed in this study. Total Kjeldahl N removal was more effective at loading rates of 2.6 kg ha^?1 d^?1. The monthly average influent: effluent TKN mg L^?1 concentration ratio was 15:4.     

Combined effects of technical grade fenitrothion, humic acids and particulate matter on cholinesterase activity in freshwater invertebrates

Purpose

The relative sensitivity of two freshwater invertebrate organisms to the organophosphorus insecticide fenitrothion was assessed by measuring cholinesterase (ChE) activity, a well-known biomarker of both exposure and effect to organophosphorus pesticides. The influence of different concentrations of humic acids (HAs) and particulate matter on fenitrothion bioavailability was assessed in the more sensitive species.

Materials and methods

The selected invertebrates were the dwelling feeding oligochaete Lumbriculus variegatus and the pulmonate gastropod Biomphalaria glabrata. Acute 48-h bioassays were performed exposing organisms to different fenitrothion concentrations. The concentrations that induced 50 % inhibition of enzyme activity (EC₅₀) were calculated. Fenitrothion bioavailability was investigated using different concentrations of commercial HA or particulate matter. Sand and a diverse selection of chromatographic resins that have been proposed as analogues of natural sediments were selected. For these experiments, animals were exposed to a fenitrothion value similar to the EC₅₀.

Results and discussion

The 48-h EC₅₀ values were 12?±?2 and 23?±?3 μg?l^?1 for L. variegatus and B. glabrata, respectively. Depending on HA concentration and the characteristics of particles, ChE activity was similar or higher than the value recorded for animals exposed only to the pesticide in aqueous solution.

Conclusion

The results indicated that L. variegatus was the more sensitive species of the two. In this species, fenitrothion bioavailability did not increase due to the presence of either different HA concentrations or particulate matter. The experimental approach may constitute a useful tool to predict the influence of dissolved organic matter and sediment particles on fenitrothion bioavailability and toxicity to non-target aquatic invertebrates.     

Cadmium Uptake by Yeast, Candida tropicalis, Isolated from Industrial Effluents and Its Potential Use in Wastewater Clean-Up Operations

This study is aimed at assessing the ability of metal-resistant yeast, Candida tropicalis, to uptake cadmium from the liquid medium. The minimum inhibitory concentration of Cd²⁺ against C. tropicalis was 2,800 mg L^?1. The yeast also showed tolerance towards Zn²⁺ (3,100 mg L^?1), Ni²⁺ (3,000 mg L^?1), Hg²⁺ (2,400 mg L^?1), Cu²⁺ (2,300 mg L^?1), Cr⁶⁺ (2,000 mg L^?1), and Pb²⁺ (1,200 mg L^?1). The yeast isolate showed typical growth curves, but low specific rate of growth was observed in the presence of cadmium. The yeast isolate showed optimum growth at 30°C and pH 7. The metal processing ability of the isolate was determined in a medium containing 100 mg L^?1 of Cd²⁺. C. tropicalis could decline Cd²⁺ 57%, 69%, and 80% from the medium after 48, 96, and 144 h, respectively. C. tropicalis was also able to remove Cd²⁺ 56% and 73% from the wastewater after 6 and 12 days, respectively. Cd produced an increase in glutathione (GSH) and non-protein thiol levels by 146.15% and 59.67% at 100 mg L^?1 concentration, respectively. Metal tolerance and accumulation together with changes in the GSH status and non-protein thiols under Cd exposure were studied in C. tropicalis.     

Localization of aluminum in tissues of fish

The concentrations of Al in fish gills has been used as a measure of fish exposure to this metal in acidified waters. This experiment was designed to determine if other fish tissues also accumulate Al and thus possibly contribute to the cause of death. Rainbow trout (Salmo gairdneri) were exposed to the following fours test conditions for 48 hr or until death: (1) pH 6.8, <0.001 mg.L^?1 Al (n=6); (2) pH 5.2, <0.001 mg₁L^?1 Al (n=2);(3) pH 5.2,1.0 mg.L^?1 Al (n=5); (4) pH 6.8, 1.0 mg.L^?1 Al (n=3). The trout were held in synthetic, low Ca water prior to, and during, experimentation. Esophagus-stomach, gonad, gall bladder, gill (left and right), heart, intestine, kidney, liver, muscle (epaxial), and spleen were digested in a 4:1 mixture of HNO₃:HClO₄ and analyzed by Inductively Coupled Plasma Emission Spectrophotometry. Elevated Al concentrations were found in gill and gastrointestinal tissues. Left and right gills of fish exposed to pH 5.2, 1.0 mg.L^?1 Al were the only tissues found to be significantly different (p<0.01) between the test conditions. The mean total Al concentrations of these test 3 fish, for the left and right gill were 3.61 and 4.33 mg.g^?1 Al dw. The Al concentration in thle gastrointestinal tissues of the fish exposed to pH 6.8 at 1.0 mg.L^?1 Al was greater than that of the control fish, but not statistically significant. These results suggest that the analysis of whole gill remains an effective indicator of Al exposure in fishes at low pH.     

Evaluation of nanosilicon dioxide and chitosan on tissue culture of apple under agar-induced osmotic stress

In vitro, applications of nanosilicon dioxide (SiO₂) and chitosan were investigated for their effects on growth and proliferation of apple (Malus domestica Borkh. ‘Gala’) explants under osmotic stress induced by agar to simulate drought stress and under non-stressed conditions. The experiment included five levels of SiO₂ (0, 25, 50, 100, and 200 mg L^?1), two levels of chitosan (0 and 40 mg L^?1), and two levels of agar (7 g L^?1 and 9 g L^?1) added to Murashige and Skoog medium. Under non-stressed conditions (7 g L^?1 agar), application of SiO₂ at 50 or 100 mg ^?1 increased proliferation of apple explants. Use of 50 or 100 mg L^?1 SiO₂ or 40 mg L^?1 chitosan increased growth of apple explants under osmotic stress (9 g L^?1 agar). This research suggests that use of SiO₂ or chitosan may improve plant growth and tolerance to stress.     

Toxic and Sublethal Effects of Ammonium Chloride on a Freshwater Fish Oreochromis mossambicus

The effects of ammonium chloride on survival and feeding energetics of the freshwater fish Oreochromis mossambicus were studied. At a concentration of 600 mg L^-1 ammonium chloride, 100% mortality was observed within 24 h; no mortality occurred at 400 mg L^-1 within 96 h; Concentration of 450 mg L^-1 ammonium chloride was found as median lethal concentration at 96 h exposure. Rearing the fish in increasing sublethal concentrations of ammonium chloride, it was found that the feeding rate decreased from 20.309 ± 0.506 mg g live fish^-1 day^-1 (mg g^-1 d^-1 (control) to 11.594 ± 0.479 mg g^-1 d^-1 at the highest sublethal concentration (100 mg L^-1. Growth rate was drastically reduced.     

多样生物污水净化系统研究及其应用

传统的污水生物处理方法经过近100年的应用和技术改进，其工艺和设备日臻完善，但仍存在投资大、能耗高、管理复杂等特点。多样生物污水净化系统是按照食物链代谢规律，设置微生物-植物-水生动物3个处理单元，污水中的有机物作为微生物的食料在第1单元被厌氧微生物消化降解成CO2、H2O、NH^ 4、CH4和PO^3-4等，除CH4作为生物能源可回收利用外，其他物质都是植物的营养物质，在第2单元被藻类等多种植物吸收，通过光合作用合成植物细胞，并释放O2。在第1、第2单元增殖的过量细胞和藻类成为水生动物的食料，在第3单元被浮游动物和鱼类捕食并转化成动物蛋白。污水中有机物在3个单元组成的生态净化系统中被多样生物逐级利用，最终转化成植物细胞和动物蛋白，使污水得到净化三级处理水平，不产生二次污染，是对环境安全的污水处理新技术之一，成为21世纪的新科技。该污水净化系统通过达到自我调控生态平衡，具有工艺流程简单、投资省、运行费用低、管理简便等优点，适合我国国情且应用前景前景广阔，尤其适用于小城镇污水处理。     

Influence of thermal power station effluents on hydrobiology of seawater

The hydrobiological parameters of the waters in the vicinity of ash slurry and cooling water outfall from Ennore Thermal Power Station located on the shore of Bay of Bengal, Madras were determined. In the outfall site, an increase in mean temperature (35 °C), salinity (3.5%), nitrite ? N (25 μg L^?1), ammonia ? N (185 μg L^?1), phosphate ? P (1 mg L^?1), silicate ? SiO₂ (1.65 mg L^?1), chlorophyll a (21.1 mg m^?3), respiration (76% of gross production), suspended solids (3.84 g L^?1), BOD (3.65 mg O₂) and decrease in pH (8.1), dissolved oxygen (DO) (5.5 mg L^?1), nitrate ? N (15 jig L^?1), gross production (16.6 Mg C m^?3 hr^?1) were recorded. Phaeopigment and respiration were inversely related with chlorophyll a and net productivity, respectively. Microbial biomass varied spatially, but was generally low (114.5 jig L^?1), at the outfall site. The hydrobiological characteristics of water with high turbidity indicate that the ash slurry and coolant water play a crucial role in a localized area resulting in environmental disturbance. The effect was profoundly influenced by an initial dilution, dispersion, wave mixing and current direction. The ecological relationships between these parameters and their implications in coastal pollution are discussed.     

Nutrient Retention in a Northern Prairie Marsh (Frank Lake,Alberta) Receiving Municipal and Agro-Industrial Wastewater

Agro-industrial wastewater and municipal sewage wereused to restore Frank Lake, a 1246 ha northernprairie marsh in southern Alberta, Canada, to providewaterfowl habitat and improve water quality. Meanannual inflow wastewater nutrient concentrations were17 mg L^-1 NH₃-N, 30 mg L^-1 NO₃-Nand 11 mg L^-1 SRP. Mean flows greater than 5000 m³ day^-1 loaded the marsh with 23 000 kg of P annually. Summer NH₃-N, NO₃-N andtotal phosphorus (TP) surface water concentrationswere decreased by 76, 87 and 64%, respectively, aswaters flowed through the first basin of the marsh.Winter treatment was less successful, with surfacewater NH₃-N, NO₃-N and TP reductions of46, –26 (export) and 26%, respectively.Short-circuiting of water flow through the marsh andcold seasonal conditions with ice cover caused spatialand temporal variation in marsh treatment. Continuedhigh loadings to the marsh may lead to sediment saturation, eutrophication or phosphorus export from the marsh.     

Batch Culture Enrichment of Indiginous Soil Microorganisms Capable of Catabolizing Creosote Components

Batch enrichment cultures for creosote catabolizing microorganisms was carried out using a creosote-contaminated soil as the inoculum. The flasks were separately spiked with phenol, o-cresol, m-cresol, p-cresol, naphthalene, anthracene, phenanthrene, pyrrole, fluorene, pyrene, fluoranthene, chrysene,benzo(a)pyrene and creosote (a complex mixture of about 400 compounds) in concentrations of 50, 100, 500, 1000, 5000, 10 000, 15 000, 20 000, 25 000 and 30 000 mg L^-1. The flasks were incubated on a rotary shaker in the dark at 30 °C. Samples for analysis were taken from the flasks every three days for three weeks. Counts of microorganisms were observed to be highest in most cases in 5000 mg L^-1 cultures. The pH values were observed to fluctuate between 5 and8 but this did not seem to affect the growth of the organisms except at 50 and 100 mg L^-1 in the phenolics and some polycyclic aromatic hydrocarbons (PAHs) were the decreases correlated with decreases in cell counts. The isolates in the first week were mainly of one morphological type in most cultures. In subsequent weeks, the populations became mixed. The higher molecular mass PAHs at higher concentration continued to support only a few types of organisms. Isolates included bacteria, actinomycetes and fungi. The phenolics and naphthalene were more readily removed (up to 100%) from the cultures. Other hydrocarbons removal were between 45 and 83% with the higher molecular mass compounds being most recalcitrant. The decreases in creosote concentration was similar to those in the phenolic compounds and the lower molecular mass compounds up to a concentration of 10 000mg L^-1. Decreases in creosote concentration started to decrease from a concentration of 15 000 mg L^-1 upward. Subsequent subculturing was observed to enhance the degradative capabilities of the isolates and the further removal of the higher molecular mass compounds. However, this enhanced degradation was much lower in creosote cultures than in the other cultures.     

Acute Toxicity of Gramoxone to Oreochromis niloticus (Trewavas) in Nigeria

The acute toxicity of paraquat (1,1-dimethyl-4,4-bipyridinium dichloride) to fingerlings of Oreochromis niloticus (Trewavas) was determined in 96 hr staticbioassays. During the assays opercular ventilation and tailfin movement rates of the fish were determined.Haemotological parameters of the blood and histopathology ofthe gills were observed.The 96 hr LC₅₀ of paraquat to fingerlings of O. niloticus was observed to be 11.84 mg L^-1.Histopathology of gills of the fish exposed to 12.00 mgL^-1, and 14.20 mg L^-1 showed a dose-dependentdisruption of the architecture of the lamellae, filamenthyperplasia and atrophy, leading to impairment in oxygenuptake. Other symptoms of toxicosis in exposed fish includeloss of equilibrium; agitated swimming; air gulping;haemorrhaging of the gills, pectoral and pelvic fins; periodof quiescence and finally, death.     

Toxic potential of different types of sewage sludge as fertiliser in agriculture: ecotoxicological effects on aquatic,sediment and soil indicator species

Purpose

Treated and processed sewage sludges (biosolids) generated during the treatment of wastewater usually contain substantial concentrations of nutrients, especially phosphorus, which is essential for plant growth. Sewage sludge therefore can be used as an alternative fertiliser in agriculture. But since sewage sludge could also contain pollutants, analysis and ecotoxicological tests on affected soil and stream water organisms are necessary in order to guarantee its harmless use.

Materials and methods

Three test species were chosen to cover the environmental compartments, water, sediment and soil. The following test species and parameters were applied to evaluate the acute effects of three sewage sludge samples: Lemna minor (growth inhibition, discolouration and colony breakup), Gammarus fossarum (mortality, behaviour) and Eisenia fetida (avoidance behaviour). Chemical assessment included nutrients, organic pollutants and heavy metals.

Results and discussion

The assessment of a non-dewatered sludge (S1) sample resulted in an inhibition of growth of L. minor starting from 0.6 g total solid (TS)?l^?1 after 7 days (EC₅₀ 1.2 g TS l^?1). G. fossarum displayed significantly decreased movement activity at 0.5 and 1.2 g TS l^?1 sludge concentration during an exposure time of 2 days, leading to decreased survival after 4 days of exposure in 0.5 g TS l^?1 (LC₅₀ 0.5 g TS l^?1). After 2 days, E. fetida exhibited an increased avoidance behaviour of contaminated soil from 0.2 g TS kg^?1 sewage sludge (EC₅₀ 0.4 g TS kg^?1). The dewatered sludge samples (S2 and S3) had a lower toxic effect on the test organisms. G. fossarum was the most sensitive test species in the applied test setups. The realistic application amounts of the tested sewage sludge samples of approximately 6.0 g TS kg^?1 (maximum allowed application amount of sewage sludge) and approximately 3 g TS kg^?1 (maximum agronomical relevant application amount) in worst case studies are higher than the analysed EC₅₀/LC₅₀ values of S1 and of the LC₅₀ (G. fossarum) of S2 and S3.

Conclusions

All three tested sewage sludge samples have to be classified as toxic at high concentration levels under laboratory conditions. Realistic output quantities of S1 will negatively influence soil invertebrates and freshwater organisms (plants and crustacean), whereas the dewatered sludge samples will most likely not have any acute toxic effect on the test organisms in the field. Test with environmental samples should be conducted in order to support this hypothesis.

     

Effect of oils and oil-products on crustaceans

The effect of oil and oil products on the 5 species of crustaceans in the Caspian sea was investigated. Two species of shrimp (Palaemon elegans, P. adspersus), crab (Thithropanopeus harrisii tridentatus), amphipoda (Pontogammarus maeoticus), and cirripeda crayfish (Balanus improvisus) are classified among them. Various oil products (oil, phenol, fuel oil, xerosene, gasoline, solar oil) were used in the experiments. The influence of oil on the respiration and mass increase, quality of generation, and larval stages of the crustaceans was studied. Minimal critical concentrations for the crustaceans are 0.001 mg L^?1 of fenol, 0.4 mg L^?1 of oil, 0.1 mg L^?1 of solar oil, 0.01 mg L^?1 of gasoline and fuel oil.