Laboratory tests as a basis for the control of sewage sludge dumping at sea

Toxicity and bioaccumulation studies were carried out on a number of UK sewage sludges to determine whether laboratory experiments could be used to regulate sludge dumping at sea. Whilst the acute toxicity of sewage sludges to adult marine organisms was generally low, shrimp larvae were found to be up to 500 times more sensitive than adults of the same species. No significant bioaccumulation of mercury or cadmium could be detected following up to 60 days exposure of fish, shrimps and mussels to the most heavily contaminated sludges available, although there was some uptake of lead, zinc and copper.     

Modeling biogas emission at different methods of sewage sludge disposal

A methodological approach to the substantiation of a fire-safe approach to the disposal sewage sludge, ensuring minimal release of inflammable gases, is proposed. The criteria of biogas formation and dispersion in the sludge mass include the total amount, emission rate and dynamics have been derived from calculation models. They are used in alternative estimates of the advantages of different bunker designs and their filling rate.     

Coprostanol as sewage tracer in McMurdo Sound, Antarctica

Sediment cores from the vicinity of sewage outfalls off McMurdo Station as well as surface grab samples from different locations in the McMurdo Sound, Antarctica were analysed for coprostanol (5β-cholestan-3β-ol) and epicoprostanol (5β-cholestan-3-ol) to assess the degree of sewage addition to the Sound. Sediment samples close to the point source contain as much as 3 mg g⁻¹ dry sediment of coprostanol, whereas samples farther from the source, for example from New Harbour and Granite Harbour, contain only trace levels to 40 ng g⁻¹. Coprostanol in the sediments of latter locations most likely originates from seals rather than from sewage outfalls. It appears that sewage particles are very quickly incorporated into the sediment layers close to the discharge point in the eastern Sound. However, significant levels (930 ng g⁻¹) of fecal sterols were detected in Cape Armitage surface sediments, indicating that the sewage plume could also have reached the seawater intake station, situated in between the outfall and Cape Armitage sampling site. These results suggest the need for a sound environmental monitoring and assessment of the existing wastewater practices in the region.     

The use of radon as tracer in environmental sciences

Radon can be used as a naturally occurring tracer for environmental processes. By means of grab-sampling or continuous monitoring of radon concentration, it is possible to assess several types of dynamic phenomena in air and water. We present a review of the use of radon and its progeny at the University of Cantabria. Radon can be an atmospheric dynamics indicator related with air mass interchange near land-sea discontinuities as well as for the study of vertical variations of air parameters (average values of different types of stability: 131–580 Bq m^?3). Concerning indoor gas, we present some results obtained at Altamira Cave (Spain): from 222 to 6549 Bq m^?3 (Hall) and from 999 to 6697 Bq m^?3 (Paintings Room). Finally, variations of radon concentration in soil (0.3 to 9.1 kBq m^?3) and underground water (values up to 500 Bq l^?1) provide relevant information about different geophysical phenomena.     

Possible use of non-toxic industrial spillage as a hydrographic tracer

There is a lack of information on deep water or bottom drift in the Firth of Clyde. Dust spillage from the iron ore unloading terminal at Hunterston in the inner Firth offers an opportunity for tracing bottom water movements by determination of ferric oxide levels in the sediments.     

Bromide as a conservative tracer for soil-water studies

The assumption that potassium bromide is a conservative tracer for soil-water studies was tested in a series of batch sorption experiments. Sorption experiments were conducted on soil samples collected from the O, E, and A horizons of the Albemarle soil series near Charlottesville, VA. The experiments were conducted under conditions of differing bromide concentration and filter treatments. Bromide concentrations in soil-solution mixtures were measured through time using an Orion bromide-specific electrode. An analysis of variance of results showed no significant sorption of bromide through time under any concentration level or filter treatment (α = 0·01). No sorption of bromide between different soil horizons could be determined. This work clearly indicates that bromide is conservative under the conditions examined.     

Monitoring seagrass beds around a sewage sludge outfall in South Australia

Digested sludge from the Port Adelaide Sewage Treatment Works has been discharged to Gulf St. Vincent, a marine embayment in South Australia, since 1978. The outfall is sited in seagrass meadows dominated by Posidonia spp. and Amphibolis spp. By 1982 the discharge had affected an area of approximately 1900 ha, 365 ha of which were completely denuded of these seagrasses. A monitoring programme conducted over summers 1983–1985, inclusive, was based on the above-ground biomass (standing crop) of Posidonia at fourteen sites around the outfall. All sites were surveyed in the first two summers and eight sites were surveyed in the third. The results indicate that there was no ongoing reduction in the standing crop of Posidonia at any of the sites. These data also suggested that excessive growth of epiphytes on the leaves of Posidonia was a likely cause of the observed impact on the seagrass beds.     

The application of electrical conductivity as a tracer for hydrograph separation in urban catchments

Two‐component hydrograph separation was performed on 19 low‐to‐moderate intensity rainfall events in a 4·1‐km² urban watershed to infer the relative and absolute contribution of surface runoff (e.g. new water) to stormflow generation between 2001 and 2003. The electrical conductivity (EC) of water was used as a continuous and inexpensive tracer, with order of magnitude differences in precipitation (12–46 µS/cm) and pre‐event streamwater EC values (520–1297 µS/cm). While new water accounted for most of the increased discharge during storms (61–117%), the contribution of new water to total discharge during events was typically lower (18–78%) and negatively correlated with antecedent stream discharge (r² = 0·55, p < 0·01). The amount of new water was positively correlated with total rainfall (r² = 0·77), but hydrograph separation results suggest that less than half (9–46%) of the total rainfall on impervious surfaces is rapidly routed to the stream channel as new water. Comparison of hydrograph separation results using non‐conservative tracers (EC and Si) and a conservative isotopic tracer (δD) for two events showed similar results and highlighted the potential application of EC as an inexpensive, high frequency tracer for hydrograph separation studies in urban catchments. The use of a simple tracer‐based approach may help hydrologists and watershed managers to better understand impervious surface runoff, stormflow generation and non‐point‐source pollutant loading to urban streams. Copyright © 2007 John Wiley & Sons, Ltd.     

Population similarity analysis of indicator bacteria for source prediction of faecal pollution in a coastal lake

Biochemical fingerprinting (BF) databases of 524 enterococci and 571 Escherichia coli isolates and an antibiotic resistance analysis (ARA) database comprising of 380 E. coli isolates from four suspected sources (i.e. dogs, chickens, waterfowls, and human sewage) were developed to predict the sources of faecal pollution in a recreational coastal lake. Twenty water samples representing four sampling episodes were collected from five sites and the enterococci and E. coli population from each site were compared with those of the databases. The degree of similarity between bacterial populations was measured as population similarity (Sp) coefficient. Using the BF-database, bacterial populations of waterfowls showed the highest similarity with the water samples followed by a sewage treatment plant (STP). Higher population similarities were found between samples from STP and water samples especially at two sites (T2 and T3) which were located near the sewerage pipes collecting wastewater from the study area. When using the ARA-database, the highest similarity was found between E. coli populations from STP and water samples at sites T2 and T4. Both faecal indicators and as well as methods predicted human faecal pollution, possibly through leakage from submerged sewerage pipes. The results indicated that the Sp-analysis of faecal indicator bacterial populations from suspected sources and water samples can be used as a simple tool to predict the source(s) of faecal pollution in surface waters.     

Numerical responses of larval fishes to deepwater sewage disposal: a field assessment

This paper summarizes the results of a large-scale ‘beyond BACI’ designed assessment of the influences of effluent discharges from Sydney's deepwater sewage outfalls on assemblages of larval fishes. Larval fishes were sampled at three outfalls and at multiple control locations three times before and three times after the deepwater outfalls were commissioned. Sampling was stratified to account for time of year, oceanography and plume behaviour. Large numbers of fish larvae were caught near the outfalls and were thus exposed to sewage plumes. Results indicated that some larvae that normally occur at depth were displaced upwards by rising plumes, particularly when plumes surfaced. No predictable positive or negative numerical responses of larvae to outfalls were evident. Rather responses varied depending on the taxa, outfall and season. The large inherent level of natural spatial and temporal variability in abundances of larvae swamped the detection of possible impacts for many taxa. Future field based studies need to track larvae through plumes to assess changes in numbers, but also to test effects on the health and condition of larvae.     

The use of sulfur hexafluoride (SF6) as a tracer of septic tank effluent in the Florida Keys

To determine the fate and movement of sewage derived contaminants and their possible interaction with surface waters in the Florida (USA) Keys, two types of experiments were conducted using SF₆ as an artificial tracer. The first type of experiment examined fluid flow from septic tanks placed in Miami Oolite on Big Pine Key, where there is a shallow freshwater lens overlying saline groundwaters. Here groundwater transport rates were constrained to be between 0.11 and 1.87 m/h, travelling in an easterly direction. The second type of experiment took place on Key Largo where there is no freshwater aquifer and the matrix of the aquifer is solely the more porous Key Largo limestone. Here we injected the tracer into a shallow well which was screened from 0.6 to 10 m. This allowed us to evaluate groundwater movement in the shallow upper portion of the aquifer, the area to which inputs by septic tanks occur. Groundwater transport rates in the Upper Keys were as great as 3.7 m/h and were controlled by the Atlantic tide. SF₆ laden groundwater plumes moved back and forth due to tidal pumping and reached nearby surface waters within 8 h.     

Effect of the substrate-concentration on the methane fermentation of sewage sludge

Summary In batch fermentation tests the effect of the substrate concentration on the methane fermentation process of the sewage sludge was controlled. In the range of 1.5 up to 6.5 percent of dry solids content in the raw sludge no changes could be demonstrated in the fermentation course, digestion of the organic substance, sludge gas production and in the organic compounds decomposition. The ratio of the solid phase concentration to the water content determined the ion concentration of the solution, which during the fermentation process would increase. The ion concentration affects the enzymatic activity of the bacteria and their metabolic process as well. The increase of the concentration of some ions, e.g. of ammonia-ions, above the given limit would inhibit the fermentation course. At conditions of the tests this limit would not be exceeded so that the inhibition of the fermentation could not be observed. In accordance with the composition of the mineral and organic part of the sludge particles the buffer capacity of media would result which is considered to be most significant for preserving the pH value in suitable limits for the bacteria, participating on the methane fermentation of organic substrate.

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Zusammenfassung In Schichtfermentations-Versuchen wurde der Einfluss der Subtratkonzentration auf die Methanfermentation von Kl?rschlamm bestimmt. Es wurde nachgewiesen, dass im Bereich von 1,5 bis 6,5% Trockensubstanz keine ?nderungen im Verlaufe der Fermentation, in der Digestion organischer Stoffe, in der Faulgasproduktion und im Abbau der Kohlenstoffverbindungen auftreten. Das Konzentrationsverh?ltnis der festen Phase des Schlammes zu seinem Wassergehalt bestimmt aber die Ionenst?rke des Milieus, die w?hrend der Fermentation erh?ht wird. Die Ionenkonzentration beeinflusst die enzymatische T?tigkeit der Bakterien und dadurch auch ihre metabolischen Vorg?nge. Die Erh?hung von Ionenkonzentration (z.B. Ammoniumionen) über eine gewisse Grenze inhibiert den Fermentationsverlauf. Unter den Bedingungen der angeführten Versuche, wo die Substratkonzentration die bei dem Betrieb der Faulbeh?lter üblichen Werte nicht überschritten hat, wurde denn auch keine Inhibition der Methanfermentation beobachtet. Die Zusammensetzung des organischen und anorganischen Anteils des Schlammes bestimmt die Pufferkapazit?t des Milieus, die für die Erhaltung des pH-Wertes in den für die Bakterient?tigkeit geeigneten Grenzen wichtig ist.

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Résumé L'on a, dans des essais de fermentation par couches, étudié l'effet de la concentration du substrat sur le processus de fermentation des boues d'épuration au méthane. On constata que, lorsque les boues ont une teneur en matière sèche entre 1,5 et 6,5%, il ne se produit aucun changement dans la fermentation, dans la digestion des substances organiques, dans la production de gaz de digestion, ni dans la décomposition des carbures. C'est toutefois du rapport entre la phase solide des boues et leur teneur en eau que dépend la concentration du milieu en ions, concentration qui augmente au cours de la fermentation. La concentration en ions influe sur l'activité enzymatique des bactéries et, de ce fait, aussi sur leur métabolisme. L'augmentation des concentrations de certains ions (ions d'ammonium par exemple) au-delà d'une certaine limite freine le processus de fermentation. Dans les conditions qui régnaient pendant les essais en question, les concentrations du substrat ne dépassèrent pas les valeurs observées dans la pratique, de sorte qu'il ne se produisit aucune inhibition de la fermentation au méthane. La composition de la fraction organique et celle de la fraction inorganique des boues détermine la capacité tampon du milieu, capacité qui est très importante pour le maintien de la valeur pH dans les limites favorables à l'activité bactérienne.

     

The use of 137Cs as a tracer in an erosion study in south limburg (the Netherlands) and the influence of chernobyl fallout

The ¹³⁷Cs radioactivity of soils was used as a tracer of soil erosion in a catchment in the Netherlands: 143 samples were analysed to map the ¹³⁷Cs redistribution using geostatistical interpolation methods. Caesium-137 activities on grassland are significantly higher than on arable land. Also, ¹³⁷Cs activities on waning slopes are higher and activities on steep slopes are lower. The soil erosion estimates, derived from the ¹³⁷Cs data, are used to validate the USLE erosion model. The recent Chernobyl nuclear accident also contributed to the ¹³⁷Cs activity. However, the Chernobyl input of ¹³⁷Cs, with a constant ratio of 1.765:1 to ¹³⁴Cs, cannot be used as a tracer of soil erosion. Because of the rapid decay of ¹³⁴Cs, we will not be possible to separate the sources of ¹³⁷Cs in the near future in areas significantly influenced by Chernobyl fallout and in these areas ¹³⁷Cs can no longer be used as a soil erosion tracer.     

Polychlorinated biphenyls in sewage sludge and sediments of the New York Bight

Sediments of the New York Bight were analysed for polychlorinated biphenyls (PCB) and found to be heavily contaminated by such substances. The highest concentrations are adjacent to an offshore sludge dump zone, implying that the primary source of PCBs is sewage sludge in the area under consideration. Widespread transport of PCBs out of the bight is not evident as the area of contamination is limited to areas of mud accumulation. The PCB profile in a core of these mud facies can be historically correlated to the commercial production of PCBs.     

Fluctuations of electrical conductivity as a natural tracer for bank filtration in a losing stream

A key parameter used in the assessment of bank filtration is the travel time of the infiltrated river water during the passage through groundwater. We analyze time series of electrical conductivity (EC) in the river and adjacent groundwater observation wells to investigate travel times of young hyporheic groundwater in adjoining channelized and restored sections of River Thur in North-East Switzerland. To quantify mixing ratios and mean residence times we perform cross-correlation analysis and non-parametric deconvolution of the EC time series. Measurements of radon-222 in the groundwater samples validate the calculated residence times. A simple relationship between travel time and distance to the river has not been observed. Therefore, we speculate that the lateral position and depth of the thalweg as well as the type of bank stabilization might control the infiltration processes in losing rivers. Diurnal oscillations of EC observed in the river and in nearby observation wells facilitate analyzing the temporal variation of infiltration. The diurnal oscillations are particularly pronounced in low flow situations, while the overall EC signal is dominated by individual high-flow events. Differences in travel times derived from diurnal and overall EC signals thus reflect different infiltration regimes.     

Incidence of urban sewage disposal in the salt-ponds areas of the south of the Bay of Cadiz

The highest pollution indices in the marsh and tide-lands situated to the south of the Bay of Cadiz have been evaluated. At the present, the salt industry of this area is being transformed into mariculture installations. This study consisted of the systematic evaluation of different parameters at 26 sampling stations during the period 1976–1981. The results suggest that extensive zones are too seriously affected to make use of them as marine piscifactories.     

Beneficial use of municipal sludge in the ocean

The micronutrients in municipal sludge enhance ocean productivity in much the same way as they enhance plant productivity when applied to the land. The organic solids of municipal sludge can also directly enhance production of valuable biomass in the ocean, particularly benthic biomass. Studies of municipal sludge and wastewater discharge into marine waters throughout the world have demonstrated that, if the application rate of municipal sludge or wasterwater was optimized by utilizing larger sites, beneficial enhancement of marine production could be achieved without the adverse effects associated with excessive application rates and overfertilization. Existing evidence indicates that, although not risk- or disadvantage-free, beneficial use of municipal sludges in the ocean is a viable management option which, in some instances, is likely to have fewer negative environmental side effects than other feasible beneficial use options.     

Potential use of mangroves as constructed wetland for municipal sewage treatment in Futian,Shenzhen, China

A pilot-scale mangrove wetland was constructed in Futian, Shenzhen for municipal sewage treatment. Three identical belts (length: 33 m, width: 3 m, depth: 0.5 m) were filled with stone (bottom), gravel and mangrove sand (surface). Seedlings of two native mangrove species (Kandelia candel, Aegiceras corniculatum) and one exotic species (Sonneratia caseolaris) were transplanted to the belts with one species for each belt. The hydraulic loading was 5 m³ d⁻¹ and hydraulic retention time 3 d. High levels of removal of COD, BOD₅, TN, TP and NH₃–N were obtained. The treatment efficiency of S. caseolaris and A. corniculatum was higher than that of K. candel. Faster plant growth was obtained for S. caseolaris. The substrate in the S. caseolaris belt also showed higher enzyme activities including dehydrogenase, cellulase, phosphatase, urease and β-glucosidase. The removal rates of organic matter and nutrients were positively correlated with plant growth. The results indicated that mangroves could be used in a constructed wetland for municipal sewage treatment, providing post-treatment to remove coliforms was also included.