Treatment Plant Outlet Research Articles

Induction patterns of new CYP1 genes in environmentally exposed rainbow trout

The cytochrome P4501 ( CYP1) gene family comprises four subfamilies in fish: CYP1A, CYP1B, CYP1C, and CYP1D. Only two CYP1 genes, CYP1A1 and CYP1A3, are so far known in rainbow trout ( Oncorhynchus mykiss). The present study aimed to identify other CYP1 subfamily genes in rainbow trout, to establish methods for quantitative mRNA expression analysis of these genes, and to determine their basal and induced mRNA expression in gills and liver. Another goal was to examine their mRNA expression in environmentally exposed fish. We cloned four new transcripts, denoted rbCYP1B1, rbCYP1C1, rbCYP1C2, and rbCYP1C3. Levels of these and the previously known rbCYP1A transcripts were determined by real-time PCR in unexposed fish, fish exposed to the potent aryl hydrocarbon receptor (AhR) agonist 3,3′,4,4′,5-pentachlorobiphenyl (PCB126), and fish caged in various waters in the Uppsala region (Sweden). The mRNA expression patterns observed in unexposed rainbow trout (basal levels) were markedly similar to those reported for orthologous genes in other species. All six transcripts were induced by PCB126 in gills and liver, suggesting all genes to be AhR regulated. The caged fish showed clear rbCYP1 induction in gills at all monitoring sites (up to 70-fold the basal level), whereas the liver responses were weak; induction (up to 5-fold) was recorded only at the Uppsala municipal sewage treatment plant outlet. Gill filament EROD activity was induced at all caging sites. Most interestingly, the rbCYP1 gene response patterns in gills differed among caging sites and among subfamilies. The EROD induction seemed to only reflect induction of rbCYP1A transcription. Response patterns of multiple CYP1 genes in gills and liver could provide an improved monitoring strategy. Such patterns could be used to characterize complex mixtures of AhR agonists and antagonists in aquatic environments.

Determination of Aluminium and Physicochemical Parameters in the Palm Oil Estates Water Supply at Johor, Malaysia

The study was to determine the concentration of aluminium (Al) and study the physicochemical parameters (pH, total dissolved solids (TDS), turbidity, and residual chlorine) in drinking water supply in selected palm oil estates in Kota Tinggi, Johor. Water samples were collected from the estates with the private and the public water supplies. The sampling points were at the water source (S), the treatment plant outlet (TPO), and at the nearest houses (H1) and the furthest houses (H2) from the TPO. All estates with private water supply failed to meet the NSDWQ for Al with mean concentration of 0.99 ± 1.52 mg/L. However, Al concentrations in all public water supply estates were well within the limit except for one estate. The pH for all samples complied with the NSDWQ except from the private estates for the drinking water supply with an acidic pH (5.50 ± 0.90). The private water supply showed violated turbidity value in the drinking water samples (14.2 ± 24.1 NTU). Insufficient amount of chlorination was observed in the private water supply estates (0.09 ± 0.30 mg/L). Private water supplies with inefficient water treatment served unsatisfactory drinking water quality to the community which may lead to major health problems.

Distribution and survival of faecal indicator bacteria in the sediments of the Bay of Vidy, Lake Geneva, Switzerland

The purpose of this study was to determine the concentrations and the horizontal distribution of faecal indicator bacteria (FIB) including Escherichia coli and Enterococcus sp. in the bottom sediments of the Bay of Vidy, City of Lausanne, Switzerland. A vertical distribution of FIB in sediments near the municipal wastewater treatment plant (WWTP) outlet was evaluated and their persistence in those sediments was monitored for a period of 90 days. High FIB levels were measured in the sediments sampled near the WWTP outlet pipe and the mouth of the Chamberonne River, at concentrations ranging between 105 and 107 CFU 100 g−1. FIB levels at 10 cm depth in the sediments near the WWTP outlet pipe ranged between 104 and 105 CFU 100 g−1, and were still detected in the top 6 cm after 90 days. Results of this study indicate that freshwater sediments of the Bay of Vidy constitute a reservoir of faecal indicator bacteria, which can persist in certain areas of the bay. Possible resuspension of FIB and pathogens may affect water quality and may increase health risks to sensitive populations during recreational activities. FIB survival in sediments for long periods is of considerable significance for the understanding of microbial pollution in water and for the management of risk at specific recreational coastal sites.

Predicting the effects of reduced external nitrogen loading on the nitrogen dynamics and ecological state of deep Lake Ravn, Denmark, using the DYRESM–CAEDYM model

We used the one-dimensional DYRESM–CAEDYM model, developed at the Centre for Water Research, University of Western Australia, to elucidate the role of nitrogen and nitrogen dynamics in the ecosystem of moderately deep Lake Ravn situated in an agricultural landscape in Denmark. We calibrated the model on a 7-year monitoring period and tested it successfully on another 5-year period. The model reproduced well the temperature and oxygen in both the epilimnion and the hypolimnion; however, the epilimnion oxygen concentration at its peak in late spring was generally underestimated. Monitoring data on nitrate and total nitrogen (TN) was well reproduced, although TN in the hypolimnion during the validation period was overestimated. RMSE values were overall similar for the calibration and the validation periods. Simulations of scenarios with a reduced external nutrient loading suggest that a substantial reduction (75%) of the TN input is required to obtain nitrogen concentrations sufficiently low to diminish phytoplankton biomass, while a 90% reduction is needed to significantly increase the depth limit of submerged vegetation. Model simulations suggest that a reduction of the external total phosphorus (TP) loading would be more feasible, as phytoplankton biomass significantly declines at a TP loading reduction of 40–50%. While our study demonstrates that nitrogen plays a minor role as limiting nutrient in Lake Ravn, the role of nitrogen can be more important in shallow polymictic, eutrophic lakes, where summer nitrate concentrations are often low. Thus a case-by-case analysis is required when setting targets for the critical loading of nitrogen and phosphorus in individual lakes – an approach named the “new immission concept” by Benndorf [2005. Ecotechnology: basis of a new immission concept in water pollution control. Water Sci. Technol. 52, 17–24] – instead of using rigorous common standards for all river basins and waste water treatment plant outlets.

Analysis and occurrence of pharmaceuticals, estrogens, progestogens and polar pesticides in sewage treatment plant effluents, river water and drinking water in the Llobregat river basin (Barcelona, Spain)

Summary This work investigated the presence of 21 emerging contaminants of various chemical groups (7 estrogens, 3 progestogens, 6 pharmaceuticals and personal care products (PPCPs), and 5 acidic pesticides) in the Llobregat river basin (NE Spain). Waters from the outlet of various sewage treatment plants (STP) and waterworks located along the river basin, as well as water samples from the river or its tributaries upstream and downstream of these plants were analysed in two pilot monitoring studies. Chemical analyses were performed by means of on-line or off-line solid-phase extraction followed by liquid chromatography-electrospray-tandem mass spectrometry. Methods detection limits (in ng/L) were ⩽0.85 for estrogens, ⩽3.94 for progestogens, ⩽30 for PPCPs, and ⩽0.99 for pesticides. Of the estrogens and progestogens analysed, only estrone-3-sulfate, estrone, estriol and progesterone were found to be present in the low nanogram per liter range in some of the samples investigated. Except for atenolol, all PPCPs studied (ibuprofen, diclofenac, clofibric acid, salicylic acid, and triclosan) could be identified at levels usually lower than 250 ng/L and up to 1200 ng/l (diclofenac). Of the various pesticides investigated (2,4-D, bentazone; MCPA, mecoprop and propanil) MCPA and 2,4-D were the most ubiquitous and abundant and bentazone the only one not detected. Individual concentrations were most often below 100 ng/L and never surpassed the EU limits.

Effects of a sewage treatment plant outlet pipe extension on the distribution of contaminants in the sediments of the Bay of Vidy, Lake Geneva, Switzerland

In 2001, the municipality of Lausanne extended the outlet pipe of the sewage treatment plant into the Bay of Vidy (Lake Geneva, Switzerland) as a measure to reduce bacterial water pollution and sediment contamination close to the lake beaches. The aim of the present study was to assess the impact of this measure. Lake bottom sediments were collected and analyzed for grain size, organic matter, organic carbon, nitrogen, phosphorus, heavy metals and hydrophobic organic compounds to evaluate their concentration and spatial distribution. Our results demonstrate that, compared to results obtained before the outlet pipe prolongation, the surface area of highly contaminated sediments was reduced by one third after the pipe extension. However, contaminant concentrations are still high and the accumulation of pollutants may represent a significant source of toxicity for benthic organisms. One concludes that contaminant reduction at the source will be necessary for a further improvement.

Some Chemical Contaminant of Surface Sediments at the Baltic Sea Coastal Region with Special Emphasis on Androgenic and Anti-Androgenic Compounds

Androgenic and anti-androgenic compounds including p,p′-DDE, Diuron, Linuron, Fenarimol, Vinclozolin, 1-(3,4-dichlorophenyl) urea (DCPU), 1-(3,4-dichlorophenyl)-3-methylurea, (DCPMU), tributyltin (TBT) and triphenyltin (TPT) and their metabolites (DBT, MBT, DPT, MPT) as well as metallic elements (Ni, Cu, Zn, As, Cd, Pb, Co, Tl, Cr, Fe, Mn, Al, K, Mg, Na, Ca, Ba, Ti, Sn), PAHs (16 indicator compounds), DDTs and PCBs have been quantified in top layer (0–10 cm) of up to 37 surface sediment samples collected from several sites in costal zone of the Gulf of Gdańsk, an inland freshwater area of Brdyujście in Poland and the tidal flats of the Norderney Island, Wadden Sea in 2002–2003. These sites differed in the degree of anthropogenic activities, including chemical pollution and related impact on biota. Especially in sediments near shipyards, ship repair facilities, harbours, other industrial activities or close to municipal sewage treatment plant outlets butyltins, PAHs and some metallic elements were found at high concentrations. Diuron, Linuron and DCPMU were detected at a few sites, Fenarimol only once, while Vinclozolin and DCPU were not detected. DDT concentrations in the sediments from the Gdańsk and Gdynia region of the Gulf show a stepwise decrease following the ban for production and use, while diffusion of PCBs at some industrial sites seems to continue. Elevated PAH concentrations in sediments seem to be mainly due to pyrogenic and less to mixed pyrogenic and petrogenic sources, while for a few sites rather petrogenic sources dominated. The reference sites in the Norderney Island, Wadden Sea showed similar or slightly higher loads of DDTs, BTs, PAHs, PCBs and metallic elements when compared to sediments from the least contaminated sites in the coastal Gulf of Gdańsk area, while phenyltins were not detected at both spatially distant European areas.

Comparing pharmaceutical and pesticide loads into a small Mediterranean river

During 2003/2004, water samples were collected upstream and downstream of two wastewater treatment plant (WWTP) outlets in order to determine the contribution of urban centres to concentration of selected pharmaceuticals (antiphlogistics, lipid regulators and carbamazepine) and pesticides into a Mediterranean river basin (Arc river, Aix en Provence, France). Pharmaceutical loads were compared to pesticide ones. They could be nearly regarded as important as pesticide ones at least at one sampling site. The observed pollution patterns differed from pesticides to pharmaceuticals. Pesticide pollution occurred through a high pollution peak in spring while pharmaceuticals were continuously infused into the river via WWTP effluents. Carbamazepine and bezafibrate were detected in almost all samples at concentration levels ranging from ng/L to μg/L. The major pharmaceutical source could be ascribed to WWTP effluents and pharmaceutical concentrations increased during low flow rate conditions (summer), when municipal wastewater effluents accounted for the majority of the river water flow. Treated wastewaters contributed to a lesser extent to pesticide river water pollution. In an urbanized Mediterranean river basin, a deep understanding of water pollution by organic waste contaminants is required in order to set up an efficient programme of pollution reduction measures.

A simple system for estimating the biofilm formation potential of water: first experiments on slow-sand filtered water

The new european regulation specifies that drinking water quality should now be assessed at the consumer's tap rather than at the outlet of treatment plants. So, it is very important for all drinking water producers and suppliers, whatever their analytical means are, to have efficient tools for the quantification of biofilms, so that they can detect problems and react as quickly as possible. Thus, on the basis of a previous european programme research, we developed and tested a simple and easily reproducible experimental procedure to assess the biofilm formation potential of waters. Sturdy stainless steel incubators, highly adapted to industrial field conditions and containing glass beads were designed to allow the biofilm formation and the measurement of technically basic parameters (HPC) or more complex parameters (Fixed Total Organic Carbon, fixed total bacteria). Such incubators were connected to a surface water after a slow sand filtration stage. The maximal quantities measured were lower than those typically reported in the literature: about 10 3 /cm 2 for HPC-R2A, 10 4 /cm 2 for total bacteria and 0.5 μg/cm 2 for Fixed Total Organic Carbon (FTOC). A significant linear relationship exists between FTOC and total bacteria or HPC but it seems that the most part of FTOC is of extra-cellular origin. More generally, the results obtained validate the use of this type of incubators as a monitoring system which is a suitable tool for all potable water producers and suppliers.

Myocarditis: An expected health hazard associated with water resources contaminated with Coxsackie viruses type B

Enteroviruses, especially Coxsackie B viruses (CBVs), are responsible for approximately 50% of cases of viral myocarditis. In the present study, serum samples (160) were collected from acute myocarditis patients at different age groups and 104 samples of the same age groups as a control. Cholesterol, LDH, CPK, and GOT were measured for all serum samples (264). Also, to study the source of virus transmission, 72 water and 72 wastewater samples were collected from water and wastewater treatment plants at intakes and outlets. Water and wastewater samples were concentrated by filtration through Zeta-plus filter cartridges and reconcentrated by the PEG-6000 precipitation method. Serum, water, and wastewater samples were inoculated in BGM cells for three successive passages. RT - PCR with enterovirus primers was carried out directly for serum samples and for 1st and 3rd cell culture passages. The positive samples were used for neutralization assay using anti-CBV sera pool to determine the CBV followed by neutralization with separate antisera. The results showed that 50 (31.25%) serum samples from acute myocarditis patients and two (1.4%) samples from the controls were positive for enterovirus RT - PCR. For water and wastewater samples enteroviruses were present in 63.8% and 8.3% for intake and outlet of water treatment plants and, 66.6% and 47.2% for intake and outlet of wastewater treatment plants, respectively. The level of CBV serotypes was varied where CBV3 was dominant for all age groups of myocarditis patients and CBV2 and CBV5 were also detected while CBV2 was the main CBV in water samples and CBV2, 3 and 5 were detected in wastewater samples. The integration of cell culture-PCR reduces the time required for virus detection and enhances the sensitivity of the test.

Impact of raw water turbidity fluctuations on drinking water quality in a distribution system

Turbidity is a widely used parameter around the world for describing drinking water quality. Sometimes, turbidity at water treatment plant outlets may reach high values during short periods of time, and this is acceptable according to some current drinking water regulations. In this study, the quantity and nature (chemical and microbiological) of suspended matter, which may travel throughout a distribution system (DS) during turbid events — affecting both raw water and water treatment — were evaluated. Treated water included filtration with no coagulant addition. During turbid events, the concentration of suspended particles increased in treated water, and a similar increase (quantity and nature) was observed throughout the DS. Bacterial indicators of contamination (total and fecal coliforms, enteroccocci, spores of Clostridium perfringens) were not found in either treated water nor in the DS during turbid events. Nevertheless, a higher bacterial aerobic spore concentration was associated with turbid events for raw, treated, and distributed water, therefore suggesting the potential passage of pathogens, if present in raw waters. Cultivable bacteria concentrations remained low in treated and distributed water regardless of the turbidity. These results emphasize the need to carefully monitor raw and treated water quality for utilities using "high quality" water resources with limited treatment barriers, especially when such water resources are affected by even slight turbidity variations. Key words: aerobic spore-forming bacteria, distribution system, drinking water, filtration, turbidity, suspended particles, water quality.

Trihalomethane formation potential and concentration changes during water treatment at Mumbai (India).

The treated water at the outlet of treatment plants and representative service reservoirs of Mumbai city have been evaluated for trihalomethane formation potential in 1995-1996. Chloroform, dichlorobromomethane, chlorodibromomethane and bromoform have been monitored during monsoon, winter and summer. The levels of chloroform are found above the regulated WHO guideline value of 200 microg L(-1) in final water during postmonsoon at Ghatkopar (226 microg L(-1)), Malbar (210.3 microg L(-1)) and Tulsi (231.26 microg L(-1)).

Impact of an urban centre on the nitrogen cycle processes of epilithic biofilms during a summer low‐water period *

AbstractNitrogen transformations in epilithic biofilms of a large gravel bed river, the Garonne, France, has been studied upstream (one site) and downstream (four sites) of a large urban centre (Toulouse, 740 000 inhabitants).High biomass, up to 49 g AFDM m−2 (ashes free dry matter) and 300 mg chlorophyll a m−2 (Chl. a), were recorded at 6 and 12 km downstream from the main wastewater treatment plant outlet. The lowest records upstream and larger downstream (less than 16 g AFDM m−2 or 120 mg Chl. a m−2) could be explained by recent water fall (early summer low‐water period).Measurements of nitrogen exchange at the biofilm–overlying water interface were performed in incubation chambers under light and dark conditions. The addition of acetylene at the mid‐incubation time allowed evaluation of both nitrification (variation in NH4+ flux after the ammonium monooxygenase inhibition) and denitrification (N2O accumulation related to the inhibition of N2O reduction). Denitrification (Dw) and nitrification rates were maximum at sites close to the city discharges in dark conditions (up to 9.1 and 5.6 mg N m−2 h−1, respectively). Unexpected denitrification activities in light conditions (up to 1.4 mg N m−2 h−1) at these sites provided evidence for enhanced nitrogen self‐purification downstream.As confirmed by most probable number (MPN) counts, high nitrification rates in biofilm close downstream were related to enhanced (more than almost 3 log) nitrifying bacteria densities (up to 7.6×109 MPN m−2). Downstream of an urban centre, nitrogen transformations in the biofilm appeared to be influenced by the occurrence of an adapted microflora which is inoculated or stimulated by anthropic pollution. Copyright © 2002 John Wiley & Sons, Ltd.

Impact of an urban centre on the nitrogen cycle processes of epilithic biofilms during a summer low-water period This paper arose from the Eighth International Symposium on Regulated Streams (EISORS).*

Nitrogen transformations in epilithic biofilms of a large gravel bed river, the Garonne, France, has been studied upstream (one site) and downstream (four sites) of a large urban centre (Toulouse, 740 000 inhabitants). High biomass, up to 49 g AFDM m−2 (ashes free dry matter) and 300 mg chlorophyll a m−2 (Chl. a), were recorded at 6 and 12 km downstream from the main wastewater treatment plant outlet. The lowest records upstream and larger downstream (less than 16 g AFDM m−2 or 120 mg Chl. a m−2) could be explained by recent water fall (early summer low-water period). Measurements of nitrogen exchange at the biofilm–overlying water interface were performed in incubation chambers under light and dark conditions. The addition of acetylene at the mid-incubation time allowed evaluation of both nitrification (variation in NH4+ flux after the ammonium monooxygenase inhibition) and denitrification (N2O accumulation related to the inhibition of N2O reduction). Denitrification (Dw) and nitrification rates were maximum at sites close to the city discharges in dark conditions (up to 9.1 and 5.6 mg N m−2 h−1, respectively). Unexpected denitrification activities in light conditions (up to 1.4 mg N m−2 h−1) at these sites provided evidence for enhanced nitrogen self-purification downstream. As confirmed by most probable number (MPN) counts, high nitrification rates in biofilm close downstream were related to enhanced (more than almost 3 log) nitrifying bacteria densities (up to 7.6×109 MPN m−2). Downstream of an urban centre, nitrogen transformations in the biofilm appeared to be influenced by the occurrence of an adapted microflora which is inoculated or stimulated by anthropic pollution. Copyright © 2002 John Wiley & Sons, Ltd.

Microbiological quality of drinking water at eight water treatment plants

Eight drinking water treatment plants were sampled monthly during one year to evaluate the removal of bacterial indicators, new indicators and some pathogenic bacteria. Six plants are allocated along the Nile River at Cairo segment and the two others on Ismailia Canal. In this study many parameters were determined; the classical bacterial indicators (total bacterial counts at 22 and 37°C, total coliforms, faecal coliforms and faecal streptococci) show the same trend in all plant intakes except faecal streptococci parameter. The numbers of faecal streptococci in plant intakes on the main stream of Nile River ranged from 8 to 250 MPN/100 ml, but the others ranged from 80 to 2700 MPN/100 ml. With regard to new indicators; total yeasts, Candida albicans, Aeromonas hydrophlia and total staphylococci ranged from 101 to 105, 102 to 105, 102 to 105 and 102 to 103 cfu/100 ml, respectively. In case of pathogens, salmonellae ranged between 102 and 103 cfu/100 ml, total vibrios varied between 102 and 104 and the Listeria group ranged from 102 to 105 cfu/100 ml from the intake samples. All tested samples from the outlet of water treatment plants, which produce drinking water, were free of classical bacterial indicators. So the produced water has a good quality from the bacteriological point, according to national and international regulations. On the other hand, the drinking water from some tested plants had one or more positive parameters of new indicators and pathogenic bacteria.

Acute and chronic toxicity of tributyltin and linear alkylbenzene sulfonate to the marine copepod Acartia tonsa

AbstractThe acute toxicities of linear alkylbenzene sulfonate (LAS) and tributyltin (TBT) to the marine copepod Acartia tonsa were tested in 48‐h tests at two salinities, 18 and 28‰. For LAS 48‐h median lethal concentration (LC50) values were 2.1 and 8.8 mg/L, respectively. For TBT the 48‐h LC50 values were 0.47 and 0.24 μg/L, respectively. The given effect concentrations are based on nominal concentrations. In an 8‐d test, effects of LAS on larval survival and development effects (effective concentration, 10%) were found at 0.2 to 0.3 mg/L. This effect concentration is higher than environmental concentrations, but at the same level as the concentration that can be expected in effluent from well‐operated activated sludge treatment plants. Environmental effects of LAS on sensitive organisms such as A. tonsa would only be expected close to the outlet of effective treatment plants, or if the treatment of the sewage effluent was inefficient. Tributyltin inhibited the developmental rate of larvae at 1 ng TBT/L, whereas the survival of larvae was affected at 15 to 20 ng TBT/L. Acartia tonsa is thus extremely sensitive to TBT. Environmental concentrations of TBT of 20 to 100 ng/L have been found near marinas. Effects on organisms as sensitive as A. tonsa are thus to be expected in the vicinities of marinas. The test method using larval survival and development is easy to perform and nonlaborious compared to, for example, a reproduction test with Daphnia magna. The acute test method as well as the egg–embryo test method may be suitable for standardization.

Toxicity identification of pocomoke river porewater

Toxicants associated with sediments affect many natural aquatic ecosystems. Pocomoke River (PR) is one of the 150 rivers and streams that feed its sediment into the Chesapeake Bay. The objective of this study was to use USEPA Toxicity Identification Evaluation (TIE) tests to identify toxicants in the sediment-porewater of PR. Samples from three depths (0–7.7, 7.8–15.4 and 15.5–23.1 cm) at four sites (1.6 km upstream of, adjacent to and 1.6 and 3.2 km downstream of the municipal sewage treatment plant (STP) outlet) were collected. The porewater samples were tested for toxicity (EC 50) using the Microtox R marine luminescent bacteria ( Vibrio fischeri), TOXITRAK TM toxicity test (Inhibition-%I), and Ceriodaphnia dubia (48-h survival-%S). High toxicity values (EC 50 = 12.8%, % I = 93 and % S = 11) were observed for the samples collected at the site 1.6 km downstream of the STP outlet, which is near an intensive agricultural area including a poultry farm. Toxicity reduced significantly with increasing depth at every sampling site. Toxicity also decreased with distance from the most contaminated site both upstream and downstream. Qualitative MetPLATE TM analyses showed that toxic forms of metals were present in all the sampling sites except for the site 1.6 km upstream of the STP outlet. Phase I TIE tests suggested that the toxicity was due to oxidants, metals and organic compounds. Phase II TIE tests identified chlorine (total) and heavy metals [zinc (Zn), lead (Pb), copper (Cu), cadmium (Cd) and Arsenic (As)]. Polychlorinated biphenyls (PCBs) and organochlorine pesticides were found in PR porewater.

Toxicity study of a Chesapeake Bay tributary - Wicomico River

The aquatic life in the Chesapeake Bay is being harmed by the inflow of nutrients, sediments and toxic contaminants. Wicomico River is one of the 150 rivers and streams that feed into the Bay. The objective of this study was to use USEPA Toxicity Identification Evaluation (TIE) tests to identify the toxicants in the sediment-porewater of Wicomico River. Samples from three different depths (7.7, 15.4 and 23.1 cm) at four different sites (1.6 km before, adjacent to, 1.6 and 3.2 km after the municipal sewage treatment plant outlet) were collected. The sediment-porewater samples were tested for toxicity (EC 50) using the Microtox R marine luminescent bacteria ( Vibrio fischeri), TOXITRAK TM toxicity test (Inhibition-%I), and Ceriodaphnia dubia (48-hr survival-%S). High toxicity values (Microtox EC 50 = 21.3%, Toxitrak % I = 85.6 and Ceriodaphnia dubia % S = 22) were observed for the samples collected adjacent to the sewage treatment plant outlet. Toxicity reduced significantly with depth at every sampling site. Qualitative MetPLATE TM analyses showed that toxic forms of heavy metals were present only in the sampling site adjacent to the sewage treatment plant outlet. Phase I TIE tests indicated that the toxicity was due to a pH sensitive toxicant (such as ammonia) and heavy metals and not from organic compounds. Phase II TIE tests identified ammonia, zinc (Zn), lead (Pb), copper (Cu) and cadmium (Cd) as the toxicants.

UV-disinfection of treated wastewater: possible effects on surface waters

UV-irradiation as an effective method of diminishing germs in the outlet of wastewater treatment plants was studied in a half-scale pilot-project sponsored by the State of Bavaria/BRD for a period of 3 years. Technical, physical and biological parameters capable of influencing this process were examined. The possibility to improve the hygienic and also the ecological structure of receiving waters was put to discussion. Possible effects of formed bypproducts upon the water biocoenosis of rivers were pointed out. The results demonstrated that UV-irradiation can diminish the number of germs in the outlet of a treatment plant to an extent which is sufficient to guarantee the maintenance of the bacteriological and presumably also the virological values set by the EC Bathing Water Directive. Nevertheless the UV-treatment process requires further technological development and research work concerning i.e. the improvement of hydraulic conditions, coat-forming on the quartz sleeves of the lamps, photochemical forming of by-products, after-growth and effects upon the localised benthic flora and fauna of the receiving water. It has to be stressed that a significant improvement of the bacteriological structure of flowing waters is only attainable, if the influx from non-point sources can be reduced simultaneously.

Surface tension of wastewater samples measured by the drop volume method

rn A systematic study of the application of the drop volume technique to the measurement of the surface tension of wastewater samples taken at the second clarifier outlet of sewage treatment plants in the Zurich area is reported. Use of a computer-controlled drop volume instrument allows us to obtain reproducible surface tension data for samples containing surface-active solutes in widely varying concentrations. It is shown that biodegradation must be inhibited (by sodium azide) between sampling and measurement. Two measuring procedures (standard and equilibrating) capable of yielding reproducible surface tension data are suggested.