Necessity of Toxicity Assessment in Turkish Industrial Discharges (Examples from Metal and Textile Industry Effluents)

Toxicity of some organic and inorganic chemicals to microorganisms is an important consideration in assessingtheir environmental impact against their economic benefits.Microorganisms play an important role in several environmentalprocesses, both natural and engineered. Some organic and inorganics at toxic levels have been detected in industrial discharges resulting in plant upsets and discharge permit violations. In addition to this, even though in some cases the effluent wastewater does not exceed the discharge limits,the results of toxicity tests show potential toxicity. Toxicityknowledge of effluents can benefit treatment plant operators inoptimising plant operation, setting pre-treatment standards, and protecting receiving water quality and in establishing sewer discharge permits to safeguard the plant. In the Turkish regulations only toxicity dilution factor (TDF) with fish is part of the toxicity monitoring program of permissible wastewater discharge. In various countries, laboratory studiesinvolving the use of different organisms and protocol for toxicity assessment was conducted involving a number of discharges.In this study, it was aimed to investigate the acute toxicity of textile and metal industry wastewaters by traditional and enrichment toxicity tests and emphasize the importance of toxicity tests in wastewater discharge regulations. The enrichment toxicity tests are novel applications and give anidea whether there is potential toxicity or growth limiting and stimulation conditions. Different organisms were used suchas bacteria (Floc and Coliform bacteria) algae (Chlorella sp.), fish (Lepistes sp.) and protozoan (Vorticella sp.) to represent four tropic levels. The textile industry results showed acute toxicity for at least one organism in 8 out of 23 effluent samples. Acute toxicity for at least two organisms in 7 out of 23 effluent sampling was observed for the metal industry. The toxicity test results were assessed with chemical analyses such as COD, BOD, color and heavy metals. It was observed that the toxicity of the effluents could not be explained by using physicochemical analyses in 5 cases for metal and 4 cases for the textile industries. The results clearly showed that the useof bioassay tests produce additional information about the toxicity potential of industrial discharges and effluents.     

Monitoring of pharmaceutically active compounds on the Guadalquivir River basin (Spain): occurrence and risk assessment

Guadalquivir River (South of Spain) is among the major freshwater sources of the European Atlantic basin. Until now scientific efforts have been focused on contamination by heavy metals and some priority pollutants in Guadalquivir River. However, the presence of "emerging contaminants", such as pharmaceutically active compounds, has not yet been studied. In this work the occurrence and risk assessment of sixteen pharmaceutically active compounds, belonging to different therapeutic groups, in Guadalquivir River during its course through Seville city are reported. Wastewater effluents from four wastewater treatment plants discharging into Guadalquivir River and river water samples were analyzed. All studied pharmaceutically active compounds, except sulfamethoxazole, trimethoprim, estrone and clofibric acid, were detected in effluent wastewaters at concentration levels up to 28.9 μg L(-1). Among the pharmaceutically active compounds found in effluent wastewater, seven were present in Guadalquivir River samples at concentration levels up to 0.75 μg L(-1), which indicated an important dilution from effluent discharge. Environmental risk assessment reveals that potential ecotoxicological risk cannot be expected on Guadalquivir River at measured concentration levels. Only, the lipid regulator gemfibrozil showed a medium risk for the environment. The risk for acute toxic effects in the environment with the current use of active pharmaceutical ingredients is unlikely. However, the results do not rule out the potential for chronic environmental effects.     

EOX concentrations in sediment in the part of the Bothnian Bay affected by effluents from the pulp and paper mills at Kemi, Northern Finland

The Bothnian Bay, which is the northernmost part of the Gulf of Bothnia in Northern Finland, is affected by effluents discharged from point sources such as the pulp and paper mills of Stora Enso Oyj Veitsiluoto Mill and Oy Metsä-Botnia Ab Kemi Mill at Kemi, and the Kemi municipal sewage plant, as well as the River Kemijoki. In this paper we discuss, how modernisation of the wastewater treatment plant at the mills, and process investments in the Best Available Techniques (BAT) for effluent treatment, have decreased the effluent discharges of biological oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus (Tot-P), total nitrogen (TOT-N), total suspended solids (TSS) and adsorbable organically bound halogens (AOX) from the mills since 1988. One specific aim of the study was to determine the EOX (Extractable Organically Bound Halogens) concentrations in bottom sediment of the Bothnian Bay in order to assess whether the EOX concentrations reflect the reduction in discharges of chlorinated compounds. According to the monitoring program carried out every third year between 1997–2006, the decreasing trend in EOX concentrations in the top 2 cm of the bottom sediment reflect the decrease in organochlorine discharges (AOX) from the mills. In 1997 the EOX concentrations in bottom sediment varied between 3–70 μg of Cl g^?1 (dry weight), and in 2006 between 3.3–32 μg of Cl g^?1 (dry weight).     

Bacterial biosensors for rapid and effective monitoring of biodegradation of organic pollutants in wastewater effluents

Significant amounts of toxic substances which are hazardous to animals, plants, microorganisms, and other living organisms including humans are released annually into aquatic and terrestrial environments, mostly from improper wastewater discharges. Early detection of such pollutants in wastewater effluents and proper monitoring before their final release into the environment is therefore necessary. In this study, two whole-cell bacterial biosensors were constructed by transforming competent cells of Shigella flexneri and Shigella sonnei with pLUX plasmids and evaluated for their potential to monitor wastewater samples undergoing degradation by measuring bioluminescence response using a microplate luminometer. Both bacterial biosensors were found to be extremely sensitive to the wastewater samples, with different patterns, concomitant with those of the COD removals demonstrated at the different days of the degradation. Generally higher bioluminescence values were obtained at the later days of the degradation period compared to the initial values, with up to 571.76% increase in bioluminescence value obtained at day 5 for 0.1% (v/v) effluent concentration. Also, a steady decrease in bioluminescence was observed for the bacterial biosensors with increasing time of exposure to the wastewater effluent for all the sampling days. These biosensor constructs could therefore be applicable to indicate the bioavailability of pollutants in a way that chemical analysis cannot, and for in situ monitoring of biodegradation. This has great potential to offer a risk assessment strategy in predicting the level of bioremediation required during municipal wastewater treatment before their final discharge into the aquatic milieu.     

Anthropogenic gadolinium anomalies and rare earth elements in the water of Atibaia River and Anhumas Creek,Southeast Brazil

The concentrations of rare earth elements (REE), measured in water samples from Atibaia River and its tributary Anhumas Creek, Brazil, present excess of dissolved gadolinium. Such anthropogenic anomalies of Gd in water, already described in other parts of the world, result from the use of stable and soluble Gd chelates as contrast agents in magnetic resonance imaging. Atibaia River constitutes the main water supply of Campinas Metropolitan area, and its basin receives wastewater effluents. The REE concentrations in water samples were determined in 0.22-μm pore size filtered samples, without and after preconcentration by solid-phase extraction with bis-(2-ethyl-hexyl)-phosphate. This preconcentration method was unable to retain the anthropogenic Gd quantitatively. The probable reason is that the Gd chelates dissociate slowly in acidic media to produce the free ion that is retained by the phosphate ester. Strong correlations between Gd and constituents or parameters associated with effluents confirmed the source of most Gd in water samples as anthropogenic. The shale-normalized REE patterns of Atibaia River and Anhumas Creek water samples showed light and heavy REE enrichment trends, respectively. Also, positive Ce anomalies in many Atibaia River samples, as well as the strong correlations of the REE (except Gd) with terrigenous elements, imply that inorganic colloidal particles contributed to the REE measured values.     

Disinfection by-product formation potentials in wastewater effluents and their reductions in a wastewater treatment plant

Disinfection by-product formation potentials (DBPFPs) in wastewater effluents from eight wastewater treatment plants (WWTPs) were investigated. In addition, a WWTP with one primary effluent and two different biological treatment processes was selected for a comparative study. Formation potential tests were carried out to determine the levels of DBP precursors in wastewater. WWTPs that achieved better organic matter removal and nitrification tended to result in lower DBPFPs in effluents. For the WWTP with two processes, haloacetic acid, trihalomethane, and chloral hydrate precursors were predominant DBP precursors in the primary and secondary effluents. The percent reductions of haloacetonitrile and haloketone formation potentials averaged at 96% which was high in comparison to the reductions of other classes of DBPFPs. In addition, biological treatment changed the DBPFP speciation profile by lowering the HAAFP/THMFP ratio. The eight plant survey and the comparative analysis of the WWTP with two processes implied that besides nitrification, there may be other confounding factors impacting DBPFPs. Oxic and anoxic conditions, formation and degradation of soluble microbial products had impacts on the DBPFP reductions. This information can be used by water and wastewater professionals to better control wastewater-derived DBPs in downstream potable water supplies.     

Fate Modelling of DEHP in Roskilde Fjord, Denmark

The fate of di(2-ethylhexyl)phthalate (DEHP) is modeled in Roskilde fjord, Denmark. The fjord is situated near Roskilde, which comprises 80,000 PE, various industries, a central wastewater treatment plant, and adjacent agricultural fields. Roskilde fjord is thus a suitable recipient for studying the transport and fate of DEHP, which is used in a variety of different industries and consumer products. Wastewater from households and industries is led to the local wastewater treatment plant, which leads the effluent to the fjord. The sludge is partly stored and partly amended on an adjacent field. The model applied in the present study is a simple box model coupling water and sediment compartments of the fjord with wastewater treatment plant effluent, streams leading to the fjord, and atmospheric deposition. The fjord model comprises first-order degradation, adsorption, sedimentation, vertical diffusion in the sediment, dispersive mixing in the water, and water exchange with the surrounding sea. Experimental measurements of DEHP were made in the fjord water and sediment, in the wastewater treatment plant inlet and effluent, and in streams and atmospheric deposition. The experimental data are used to calibrate the model. The model results show that freshwater from streams is the predominant DEHP source to the fjord, followed by atmospheric deposition and effluents from wastewater treatment plants. Sedimentation is the predominant removal mechanism followed by water exchange with the sea and degradation.     

Monitoring of trace metals and pharmaceuticals as anthropogenic and socio-economic indicators of urban and industrial impact on surface waters

The research focuses on the monitoring of trace metals and pharmaceuticals as potential anthropogenic indicators of industrial and urban influences on surface water. This study includes analysis of tracers use for the indication of water pollution events and discussion of the detection method of these chemicals. The following criteria were proposed for the evaluation of indicators: specificity (physical chemical properties), variability (spatial and temporal), and practicality (capacity of the sampling and analytical techniques). The combination of grab and passive water sampling (i.e., diffusive gradient in the thin film and polar organic chemical integrated samplers) procedure was applied for the determination of dissolved and labile trace metals (Ag, Cd, Cr, Cu, Ni, Pb, and Zn) and pharmaceuticals (carbamazepine, diazepam, paracetamol, caffeine, diclofenac, and ketoprofen). Samples were analyzed using inductively coupled plasma mass spectrometry (MS; trace metals) and liquid chromatography–tandem MS electrospray ionization+/? (pharmaceuticals). Our results demonstrate the distinctive spatial and temporal patterns of trace elements distribution along an urban watercourse. Accordingly, two general groups of trace metals have been discriminated: “stable” (Cd and Cr) and “time varying” (Cu, Zn, Ni, and Pb). The relationship Cd???Cu?>?Ag?>?Cr?≥?Zn was proposed as an anthropogenic signature of the industrial and urban activities pressuring the environment from point sources (municipal wastewaters) and the group Pb–Ni was discussed as a relevant fingerprint of the economic activity (industry and transport) mainly from non-point sources (runoff, atmospheric depositions, etc.). Pharmaceuticals with contrasting hydro-chemical properties of molecules (water solubility, bioaccumulation, persistence during wastewater treatment processes) were discriminated on conservative, labile, and with combined properties in order to provide information on wastewater treatment plant efficiency, punctual events (e.g., accidents on sewage works, runoff), and uncontrolled discharges. Applying mass balance modeling, medicaments were described as relevant socio-economic indicators, which can give a picture of main social aspects of the region.     

Comparative Salinity Tolerance of Three Indigenous Tropical Freshwater Cladoceran Species; Moinodaphnia Macleayi, Ceriodaphnia Rigaudii and Diaphanosoma Brachyurum

The acute salinity tolerance of three tropical freshwater cladoceran species, M. macleayi, C. rigaudii and D. brachyurum was determined. The existence of these species represented new records for Trinidad and Tobago, a tropical Caribbean island. It has a large oil based industry, in which, the primary effluent (saline produced water) is discharged directly into many freshwater systems. Cladoceran species are used routinely in temperate regions, to assess the impacts of chemicals and effluents in freshwater systems. However, relatively few studies have assessed the salinity tolerance of these organisms. Test organisms were assayed using seven salinity treatments (0, 1, 3, 5, 10, 15, 20, 25‰) prepared by volumetrically mixing natural filtered seawater with dilution water. C. rigaudii had a 48 h LC50 of 1.6‰, M. macleayi 1.5‰ and D. brachyurum <1‰. The CSmax (critical salinity maximum) for C. rigaudii and M. macleayi was 3‰ after 48 h, compared to 1‰ for D. brachyurum. There was no salinity value at which there was 100% survival. The resulting salinity response curve was a straight line which indicated that each species was intolerant of salt. Consequently, any of these can be considered as a representative freshwater organism for toxicity testing in Trinidad and Tobago.     

Adsorption of the antiepileptic carbamazepine onto agricultural soils

Carbamazepine is an antiepileptic pharmaceutical which is commonly found in environmental matrices. It passes through wastewater treatment plants (WWTPs) almost completely unaffected and has been found to be highly persistent in the environment. The application of sludge in agricultural fields and the use of WWTP effluents for irrigation constitute a potential source of soil contamination. Consequently, the assessment of the interaction between carbamazepine and soils is of crucial importance to understand its fate in the environment. To monitor the sorption behavior of carbamazepine onto agricultural soils, batch equilibrium experiments were performed using soils subjected to distinct long-term fertilizations. In order to follow the adsorption experiments, an UV spectral deconvolution methodology was applied and the results compared with those from micellar electrokinetic chromatography. The results obtained by both methods did not present significant statistical differences at 95% confidence level. Therefore, it was proven that, in the context of adsorption studies, UV spectral deconvolution is a valid alternative to common chromatographic methods, with the major advantage of being a simple and fast procedure. The adsorption of carbamazepine onto the selected soils was satisfactorily described by the Freundlich model. The obtained Freundlich parameters (K(F)) (between 1.79 ± 0.07 and 4.8 ± 0.2 mg kg(-1) (mg L(-1))(-N)) indicate that the adsorption behavior of carbamazepine is dependent on the soil fertilization. Also, it is not extensively sorbed, indicating that carbamazepine present in soils can be a potential source of contamination of surface and ground waters through run-off and infiltration.     

A Characterization of Selected Endocrine Disruptor Compounds in a Portuguese Wastewater Treatment Plant

Anthropogenic compounds that are able to disrupt the endocrine system of wildlife species are a major cause for concern and have led to a demand for new screening methods. The identification and quantification of endocrine disruptor compounds at wastewater treatment plant is of major interest to assess the endocrine activity of wastewater treatment plant discharges into the environment. This study consists of a preliminary survey of concentrations of previously selected endocrine disruptor compounds, undertaken to establish environmental concentrations and to support a biological program assay exposing freshwater fish to them. Selected endocrine disrupting chemicals (APEs, bisphenol A and 17 β-estradiol) were measured in samples from a wastewater treatment plant located in Lisbon (Portugal), using recent commercial enzyme-linked immunosorbent assay kits and also LC-MS/MS. The results show that the wastewater treatment plant treatment process is efficient on the removal of target endocrine disruptor compounds. However, environmentally significant concentrations are still present in the treated effluent. The results also show that enzyme-linked immunosorbent assay kit is suitable for routine analysis of the selected compounds. The results are also useful since the wastewater treatment plant is located in a Mediterranean region, which results in an effluent with its own characteristics.     

Clear and present danger? The use of a yeast biosensor to monitor changes in the toxicity of industrial effluents subjected to oxidative colour removal treatments

Discharges of coloured effluents into surface waters provide conspicuous evidence of the impact of industry on the environment. The textile industry is an obvious candidate for sources of such discharges. Conventional treatment methods appear to alleviate this situation by removing colour, however the affect on toxicity is less obvious. The objective of this study was to examine the changes in effluent toxicity during the course of two alternative wastewater treatment methods, ozonation and electrochemical oxidation, using a novel toxicity biosensor, GreenScreen EM. The biosensor is capable of measuring both general acute toxicity (cytotoxicity), and more specifically genotoxicity, that is damage to a cell's DNA structure, replication or distribution, caused by substances that may be mutagenic and/or carcinogenic. The biosensor utilises a modified strain of the brewers yeast Saccharomyces cerevisiae, incorporating a gene encoding green fluorescent protein (GFP) linked to the inducible promoter of the DNA damage responsive RAD54 gene. Upon exposure to a genotoxin, the production of GFP is up-regulated in parallel with RAD54, and the resulting cellular fluorescence provides a measure of genotoxicity. Acute toxicity is simultaneously determined by monitoring relative total growth of the cell culture during incubation. The results presented in this paper show that a reduction in colouration does not necessarily correspond to a reduction in effluent toxicity.     

Input of selected human pharmaceutical metabolites into the Norwegian aquatic environment

The occurrence of the metabolites of five human pharmaceuticals was investigated in treated wastewater, surface waters and sediments. Metabolites of carbamazepine (carbamazepine epoxide), diclofenac (4'- and 5-hydroxy diclofenac) and atorvastatin (o- and p-hydroxy atorvastatin) were typically detected in flow proportional 24 h composite samples of wastewater effluent collected from the Norwegian cities of Oslo and Troms? at higher concentrations than the parent pharmaceutical. The concentrations determined in discharged effluent were as high as 3700 ng L(-1) for 5-hydroxy diclofenac. The overall mean concentration of metabolites being typically higher in the primary treated effluent from the city of Troms? compared to the tertiary treatment performed on the Oslo effluent. Metabolites of carbamazepine (carbamazepine-10,11-epoxide), metoprolol (α-hydroxy metoprolol) and simvastatin (hydroxy simvastatin) were detected in surface water samples collected from Oslofjord at concentrations of up to 108 ng L(-1), whilst α-hydroxy metoprolol and simvastatin hydroxy carboxylic acid were also detected in sediments at low ng L(-1) concentrations. These screening data show that the metabolites of selected pharmaceuticals are being discharged into the Norwegian coastal environment and that certain metabolites occur in marine surface waters and sediments.     

Occurrence and removal of titanium at full scale wastewater treatment plants: implications for TiO2 nanomaterials

Titanium dioxide nanoparticles increasingly will be used in commercial products and have a high likelihood of entering municipal sewage that flows to centralized wastewater treatment plants (WWTPs). Treated water (effluent) from WWTPs flows into rivers and lakes where nanoparticles may pose an ecological risk. To provide exposure data for risk assessment, titanium concentrations in raw sewage and treated effluent were determined for 10 representative WWTPs that use a range of unit processes. Raw sewage titanium concentrations ranged from 181 to 1233 μg L(-1) (median of 26 samples was 321 μg L(-1)). The WWTPs removed more than 96% of the influent titanium, and all WWTPs had effluent titanium concentrations of less than 25 μg L(-1). To characterize the morphology and presence of titanium oxide nanoparticles in the effluent, colloidal materials were isolated via rota-evaporation, dialysis and lyophilization. High resolution transmission electron microscopy and energy dispersive X-ray analysis indicated the presence of spherical titanium oxide nanoparticles (crystalline and amorphous) on the order of 4 to 30 nm in diameter in WWTP effluents. This research provides clear evidence that some nanoscale particles will pass through WWTPs and enter aquatic systems and offers a methodological framework for collecting and analyzing titanium-based nanomaterials in complex wastewater matrices.     

Occurrence of perfluorinated compounds in the aquatic environment as found in science park effluent,river water,rainwater, sediments,and biotissues

The current article maps perfluoroalkyl acids (PFAAs) contamination in the largest Science Park of Taiwan. The occurrence of ten target PFAAs in the effluent of an industrial wastewater treatment plant (IWWTP), its receiving rivers, rainwater, sediment, and the muscles and livers of fish was investigated. All target PFAAs were found in effluent of IWWTP, in which perfluorooctane sulfonate (PFOS) (6,930 ng/L), perfluorohexyl sulfonate (PFHxS) (2,662 ng/L) and perfluorooctanoic acid (PFOA) (3,298 ng/L) were the major constituents. Concentrations of PFBS and PFOS in the IWWTP downstream areas have exceeded safe concentration levels of avian and aquatic life, indicating a potential risk to wildlife in those areas. In sediment samples, predominant contaminants were PFOS (1.5–78 ng/g), PFOA (0.5–5.6 ng/g), and perfluorododecanoic acid (PFDoA) (nd–5.4 ng/g). In biological tissue samples, concentrations as high as 28,933 ng/g of PFOS were detected in tilapia and catfish liver samples. A positive correlation for log (C _sediment/C _water) and log (C _tissue/C _water) was found. The concentration and proportion (percentage of all PFAAs) of PFOS found in biotissue samples from the Keya River (which receives industrial wastewater) were found to be much greater (200 times) than those of samples from the Keelung River (which receives mainly domestic wastewater). These findings suggest that the receiving aquatic environments and, in turn, the human food chain can be significantly influenced by industrial discharges.     

Impact of wastewater treatment plant discharge of lidocaine, tramadol, venlafaxine and their metabolites on the quality of surface waters and groundwater

The presence of the anesthetic lidocaine (LDC), the analgesic tramadol (TRA), the antidepressant venlafaxine (VEN) and the metabolites O-desmethyltramadol (ODT) and O-desmethylvenlafaxine (ODV) was investigated in wastewater treatment plant (WWTP) effluents, in surface waters and in groundwater. The analytes were detected in all effluent samples and in only 64% of the surface water samples. The mean concentrations of the analytes in effluent samples from WWTPs with wastewater from only households and hospitals were 107 (LDC), 757 (TRA), 122 (ODT), 160 (VEN) and 637 ng L(-1) (ODV), while the mean concentrations in effluents from WWTPs treating additionally wastewater from pharmaceutical industries as indirect dischargers were for some pharmaceuticals clearly higher. WWTP effluents were identified as important sources of the analyzed pharmaceuticals and their metabolites in surface waters. The concentrations of the compounds found in surface waters ranged from 相似文献   

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A Study of Eichhornia crassipes Growing in the Overbank and Floodplain Soils of the River Yamuna in Delhi, India

River Yamuna, like most of the major rivers of India, has become increasingly polluted over the years from both point and non-point sources, particularly in the urban sectors such as Delhi. Field studies, conducted in January, 1994 have investigated the impact of wastewater discharges from four major drains (Najafgarh, Power House, Barapula, Kalkaji) on the overbanks, floodplains and Eichhornia in River Yamuna in Delhi, with particular reference to elemental contamination. It is concluded that except for Cd and Co, overall mean soil concentrations along the full stretch of the river in Delhi are within the world background levels of uncontaminated soils. However, the wastewater discharges from the drains, with the exception of Barapula drain, generally increase the elemental concentrations of overbank soils downstream of the discharges. Eichhornia plants growing along the banks receiving wastewaters from the Najafgarh and Barapula drains are unhealthy and reduced in population which can be attributed to a combination of alkaline pH of the growth medium, metal toxicity and high BOD at the site receiving effluents from the Najafgarh drain, and alkaline pH, metal toxicity and the turbid conditions of water with fly ash particle deposition on the plant surfaces at the site receiving effluents from the Barapula drain. Generally, considering the entire stretch of the river in Delhi, the roots of these plants growing on the overbank soils are found to be accumulators of all elements except Co, Al and Fe, with Co uptake being minimal. There are marked differences in elemental uptake of the water hyacinths growing on the overbanks and floodplains of the river.     

厌氧-缺氧-好氧处理工艺的污水处理厂进出水的毒性评价

为了准确评估厌氧-缺氧-好氧（A²/O）处理工艺对废水毒性的削减效率,采用斑马鱼胚胎急性毒性实验、发光细菌急性毒性实验和小鼠L929细胞毒性实验进行测试,结合理化指标,通过毒性当量（TU）法、平均毒性（AvTx）法、毒性指数（TxPr）法、最敏感测试（MST）法和潜在生态毒性效应（PEEP）法对常州市6家污水处理厂（生活污水、综合废水、化工废水、制药废水）进水和出水的生物毒性进行了评价。结果表明,斑马鱼胚胎的毒性敏感程度最高,3种受试生物的毒性评价结果具有较好的一致性。理化达标的污水处理厂出水仍存在一定的生物毒性效应,出水毒性较大的是综合污水处理厂,排入受纳水体后可能会对周围的生态环境产生潜在的生态风险。A²/O处理工艺对各污水处理厂进水的毒性削减较好,其中对制药废水的毒性削减最高,AvTx、TxPr、MST和PEEP的毒性削减率分别为99.45%、99.64%、99.48%和69.66%。与AvTx、TxPr、MST法相比,PEEP法能够更综合地评价废水毒性。     

Physicochemical quality of an urban municipal wastewater effluent and its impact on the receiving environment

The physicochemical qualities of the final effluents of an urban wastewater treatment plant in South Africa were assessed between August 2007 and July 2008 as well as their impact on the receiving watershed. The pH values across all sampling points ranged between 6.8 and 8.3, while the temperature varied from 18°C to 25°C. Electrical conductivity (EC) of the samples was in the range of 29–1,015 μS/cm, and turbidity varied between 2.7 and 35 NTU. Salinity and total dissolved solids (TDS) varied from 0.36 to 35 psu and 16 to 470 mg/L, respectively. The concentrations of the other physicochemical parameters are as follows: chemical oxygen demand (COD, 48–1,180 mg/L); dissolved oxygen (DO, 3.9–6.6 mg/L); nitrate (0.32–6.5 mg NO $_{3}^{-}$ as N/L); nitrite (0.06–2.4 mg NO $_{2}^{-}$ as N/L); and phosphate (0.29–0.54 mg PO $_{4}^{3-}$ as P/L). pH, temperature, EC, turbidity, TDS, DO, and nitrate varied significantly with season and sampling point (P?<?0.05 and P?<?0.01, respectively), while salinity varied significantly with sampling point (P?<?0.01) and COD and nitrite varied significantly with season (P?<?0.05). Although the treated effluent fell within the recommended water quality standard for pH temperature, TDS, nitrate and nitrite, it fell short of stipulated standards for other parameters. The result generally showed a negative impact of the discharged effluent on the receiving watershed and calls for a regular and consistent monitoring program by the relevant authorities to ensure best practices with regard to treatment and discharge of wastewater into the receiving aquatic milieu in South Africa.