bluuebunny/crossref_metadata_2025 huggingface dataset:
Artificial neural networks as a tool in urban storm drainage
Authors: Loke E. , Warnaars E. A. , Jacobsen P. , Nelen F. , Almeida M. do Céu
Published: May 2018

The introduction of Artificial Neural Networks (ANNs) as a tool in the field of urban storm drainage is discussed. Besides some basic theory on the mechanics of ANNs and a general classification of the different types of ANNs, two ANN application examples are presented; The prediction of runoff coefficients and the restoration of rainfall data. From the results, it can be concluded that ANNs can deal with problems that are traditionally difficult for conventional modelling techniques to solve. Their advantages include good generalisation abilities, high fault tolerance, high execution speed, and the ability to adapt and learn. However, ANNs rely strongly on the quantity of data examples, their training is occasionally slow, and they are not transparent and obstruct any closer analysis and interpretation of their performance. Finally, it is expected that the future of ANNs will lie in its integration with other conventional and more advanced modelling techniques, creating so-called hybrid models.
Near bed solids transport rate prediction in a combined sewer network
Authors: Arthur Scott , Ashley Richard M.
Published: May 2018

The physical and biochemical nature of the material transported near the bed (‘bed-load’) in combined sewers is established. The merits of the recent evolution of the terminology used in this field are discussed. The physical characteristics of material found in transport at three separate combined sewer field sites are described. The importance of this mode of transport, in terms of the mass transported and pollutant potential, is demonstrated based on data collected from Dundee combined sewerage system sites. The development of a novel near bed solids transport prediction equation is described. Comparisons are made between measured near bed solids transport rates obtained in the field, at sites with and without deposited beds, with predictions obtained using the new methodology. The need for future research in this subject area is emphasised.
Characterization of solid and metal element distributions in urban highway stormwater
Authors: Sansalone John J. , Buchberger Steven G.
Published: May 2018

Urban drainage from paved surfaces transports a wide gradation of solids ranging from sub-micron particles to gravel size aggregates. This study measured physical characteristics of solids transported in lateral pavement sheet flow from a heavily traveled urban roadway in Cincinnati. The physical characteristic measured was particle size which was used as a surrogate of specific surface area. Solids were sorted according to particle size distributions (PSD). Solids ranged from smaller than 1 μm to greater than 10,000 μm. Particles larger than 25 μm were separated mechanically to generate PSDs. Flow rate and duration controlled the yield and size of transported solids. Metal element analysis of PSD from snow and rainfall events indicate that Zn, Cu and Pb mass increase with decreasing particle size. Cd did not exhibit a similar trend. Results provide guidance for assessment of urban runoff water quality impacts and design of in-situ treatment strategies.
Operational experience with CSO sieving treatment
Authors: Brombach Hansjörg , Pisano William
Published: May 2018

The first rotary drum type sieve filter has been automatically operating for 4 years now. At low hydraulic loads the device acts as a filter and at high hydraulic loads as a sieve. It is located at a storm overflow tank to treat the overflow of the combined sewage system into the receiving waters and thus avoid visible, unaesthetic pollution by floatables. The paper reports our experience concerning dimensioning, frequency of operation and pollution removal efficiency.
Heavy metals in freshwater ecosystems introduced by urban rainwater runoff - monitoring of suspended solids, river sediments and biofilms
Authors: Fuchs S. , Haritopoulou T. , Schäfer M. , Wilhelmi M.
Published: May 2018

Sediments, suspended solids and biofilm samples at different locations of the River Alb near Karlsruhe were analysed for their heavy metal content (Pb, Cu, Cd). The main task of this study was to validate the biofilm method by comparing the measured pollution with the results of long term monitoring programs based on sediments and suspended solid samples. All compartments of the surveyed systems showed increasing heavy metal concentrations towards highly urbanised areas. The translation of data into pollution classes detected similar pollution situations for sediments and biofilms. The presented biofilm method recommends itself as a practicable instrument for assessing the heavy metal pollution in freshwater ecosystems. The easy sampling-technique, the low variability in the detected values and the ecological relevance of biofilms are the obvious advantages of this biofilm monitoring.
Photocatalytic inactivation of phage Qβ by immobilized titanium dioxide mediated photocatalyst
Authors: Lee S. , Nishida K. , Otaki M. , Ohgaki S.
Published: May 2018

Photocatalytic inactivation of virus by immobilized TiO2 was investigated using RNA phage Qβ as a model. TiO2-coated tiles, developed for interior sterilisation, were used as immobilized photocatalyst. 2.2 log Qβ was inactivated by immobilized TiO2 mediated photocatalysis by 1h irradiation with near UV black light at an intensity of 3.6×10−3W/cm2. Experiments with a slurry TiO2 reactor were also performed as a reference for the inactivation kinetics study. Photocatalytic Qβ inactivation was expressed by first-order kinetics as the initial concentration of the phage Qβ varied. The inactivation rate constant was proportional to the light intensity in the range of 3–8×10−3W/cm2 of black light with immobilized TiO2 photocatalyst. Broth introduced with phage into the reaction solution inhibited inactivation. No noticeable difference in inactivation was observed between germicidal lamp irradiation with and without immobilized TiO2.
Abundance of bacteriophages of enteric bacteria in different freshwater environments
Authors: Araujo R. , Lasobras J. , Puig A. , Lucena F. , Jofre J.
Published: May 2018

The abundances of somatic coliphages, F-specific phages and B. fragilis phages were measured in freshwater environments with different levels of faecal pollution. In samples with recent pollution of domestic origin the numbers of the three groups of phages were highly correlated. In this set of samples B. fragilis phages were significantly outnumbered by F-specific and these by somatic coliphages. In waters with intermediate levels of pollution, coliphages were more abundant than phages infecting B. fragilis. The levels of the three groups of phages, which were very low, were similar in waters with persistent faecal pollution indicating that B. fragilis phages were most resistant to natural inactivation processes.
Viral and bacterial contamination of groundwater from on-site sewage treatment systems
Authors: Scandura J. E. , Sobsey M. D.
Published: May 2018

On-site septic tank-soil absorption systems treating domestic wastewater have contaminated groundwaters with enteric viruses and other pathogens and caused drinking waterborne outbreaks. The factors influencing pathogen transport, survival and fate at on-site wastewater treatment systems remain inadequately characterised. We studied the survival and transport of a model enterovirus (BE-1) and faecal coliform bacteria in four on-site wastewater treatment systems (three conventional and one low pressure, small pipe diameter, pumped system) located in sandy soils typical of the coastal plains. Septic system wastewaters were seeded seasonally with known amounts of BE-1 and the fate of BE-1, faecal coliforms and other wastewater constituents were followed for three months in seeded wastewaters and groundwaters of drainfield monitoring wells. BE-1 levels in seeded wastewaters declined exponentially by kinetics consistent with a 3d hydraulic residence time. BE-1 was detected in ground waters of monitoring wells as early as 1d after seeding and persisted up to two months. Virus detection in ground water was greater in winter than in summer and was positively associated with proximity to septic effluent distribution lines, drainfield soils with the lowest clay content, elevated ground water pH and shallower vadose zones. Viruses were not strongly associated with either distance from septic tank or faecal coliform levels in groundwater. Under optimum conditions, virus reductions were as high as 9 log10, but in systems with the most coarse (sand) soils and highest water tables (most shallow vadose zones), there was extensive ground water contamination by viruses and other wastewater constituents. Under some conditions, septic systems in sandy coastal plains soils can contaminate ground water with viruses and other wastewater constituents.
Assessment of the exposure of swimmers to microbiological contaminants in fresh waters
Authors: Medema G. J. , van Asperen I. A. , Havelaar A. H.
Published: May 2018

As part of a prospective cohort study among triathletes to determine a relationship between the microbiological quality of fresh bathing water and the risk of acquiring an intestinal infection, the exposure of the triathletes to microbiological contaminants was assessed. Waters were collected at seven triathlons (swimming course 1–1.5km) held in the summer of 1993 and 1994 to have a range of water qualities. All were influenced by sewage effluents, most also by agricultural run-off. Samples were collected several weeks before the event to establish a sampling programme (1993) and during the actual exposure of the triathletes (1993 and 1994) and examined for thermotolerant coliforms alone (samples preceding the event) and for E. coli, faecal enterococci, Staphylococcus aureus, F-specific RNAphages, enteroviruses (1993 and 1994) and for thermophilic Campylobacter, Salmonella, Aeromonas, Plesiomonas shigelloides and Pseudomonas aeruginosa (1993). The samples taken in the weeks before the exposure showed significant differences in thermotolerant coliform concentration between locations, depths and times. Also during swimmer exposure, significant differences occurred in microorganism levels at the different sampling points over the swimming course. As the triathletes swam as a group, they were exposed to approximately the same water at the same time. The geometric mean concentration was used to characterise each site. In the epidemiological study, the risk of an intestinal infection correlated with the concentration of thermotolerant coliforms and E. coli but not with the other parameters. The geometric mean concentration of thermotolerant coliforms at the triathlons ranged from 11–330/100mL and 54–1,200/100mL E. coli. Ranking of the seven sites by faecal pollution level, based on the geometric mean concentration of a faecal indicator, resulted in a different ranking for each indicator. At the fresh water sites studied, only the ratio between the geometric mean density of E. coli and thermotolerant coliforms was constant. The ratio between the other parameters related to faecal pollution (faecal enterococci, F-specific RNA phages, enteroviruses) varied considerably. Water quality standards relating to faecal pollution can only be based on parameters that show a significant correlation with risk of intestinal illness.
Bacterial removal in three pilot-scale wastewater treatment systems for rural areas
Authors: Garcia M. , Bécares E.
Published: May 2018

A comparative study on the removal of several pathogenic bacteria and their indicators was carried out at three natural wastewater treatment systems: stabilisation pond, high-rate algal pond and a free-water macrophyte system, retention times being 24, 5 and 3 days respectively. The macrophyte system showed higher removal efficiency for most of the groups, followed by stabilisation pond and high rate algal pond. All systems showed their highest efficiencies in the reduction of total coliforms, ranging from 98.68% for the stabilisation pond to 99.48% for the macrophyte process. Highly significant differences were found between the systems for bifidobacteria, C. perfringens and total coliforms removal. Pathogens and their indicators showed a different behaviour in their daily removal rate depending on the treatment plant.
Effects of peracetic acid and UV irradiation on the inactivation of coliphages in wastewater
Authors: Rajala-Mustonen R. L. , Toivola P. S. , Heinonen-Tanski H.
Published: May 2018

This study aimed to determine the effectiveness of peracetic acid (PAA) on the inactivation of bacteriophages in wastewater. The possibility of utilising a shorter contact time by combining the treatment by PAA and UV irradiation was also investigated. The phages added in wastewater were exposed to UV irradiation and different concentrations of PAA. The treatment was followed by 15min with PAA and 60min with UV. In the combined treatment, PAA was first added to the wastewater and samples taken after 5 and 10min. Then UV irradiation was applied and samples taken after 1 and 2.5min. The inactivation of the DNA- and RNA-phages by UV irradiation alone for 2.5min was more than 5 log10 and more than 3 log10 units respectively. Peracetic acid inactivated the DNA-phage more than 6 log10 units and RNA-phage about 4 log10 units in 1h contact time. The same inactivation was achieved in 12.5min by PAA and UV together as by PAA alone in 1h. The turbidity of the water decreased the inactivation to some degree. The DNA-phage was clearly more sensitive to both UV irradiation and PAA than the RNA-phage.
Persistence of human astrovirus in fresh and marine water
Authors: Bosch A. , Pintó R. M. , Villena C. , Abad F. X.
Published: May 2018

Large gastroenteritis outbreaks associated with astroviruses are being reported with increasing frequency suggesting that astrovirus may be an important agent of epidemic acute non-bacterial gastroenteritis in children and adults. In this study, a procedure, based on infection of CaCo-2 cell monolayers followed by reverse-transcription polymerase chain reaction, was developed to ascertain the persistence of infectious human astroviruses in tap and marine water at 4±1°C and 20±1°C. The adequacy of this methodology for monitoring the decay of infectious fastidious viruses was assessed by determining the survival of a cytocidal virus (poliovirus 1) concomitantly by MPNCU and cell infection plus RT-PCR. After 60d in dechlorinated tap water, the decay of astrovirus infectivity was lower than 2 logs at 4±1°C and around 3.6 logs at 20±1°C, while after 90d the titre reduction was around 3.3 and 4.3 logs at 4±1°C and 20±1°C respectively. In natural non-autoclaved seawater at 20°C, astrovirus showed a lower level of persistence. The possibility to acquire data on the survival of fastidious viruses in the environment opens new perspectives on the epidemiology of some health significant infections transmitted by the faecal-oral route.
Regrowth of faecal coliforms and salmonellae in stored biosolids and soil amended with biosolids
Authors: Gibbs R. A. , Hu C. J. , Ho G. E. , Unkovich I.
Published: May 2018

Stabilised wastewater sludge (biosolids) has beneficial re-use properties but these are limited by the presence of human pathogens. In this study soil amendment with biosolids and storage of biosolids prior to re-use were examined as disposal and treatment options. In a soil amendment trial biosolids were mixed with sandy soil and monitored for 37 weeks. In two storage trials biosolids were stored in piles 1m high and monitored for <60 weeks. Included in the monitoring programme were tests to determine the concentrations of faecal coliforms, faecal streptococci and salmonellae. In both the soil amendment trials and biosolids storage trials, concentrations of indicator organisms and salmonellae decreased through an extended hot, dry summer period. Although these organisms were not detected in the majority of samples taken during the summer, repopulation of faecal coliforms and salmonellae occurred in the trials following rainfall at the beginning of the winter. In the case of one of the storage trials repopulation occurred following a period of 50 weeks when salmonellae and faecal coliforms were not detected. When repopulation occurred, faecal coliform concentrations increased to higher than those at the beginning of the trials. These results suggest that faecal coliforms and salmonellae were at undetectable concentrations through the summer period but were able to grow when provided with favourable conditions. From this limited trial it was concluded that soil amended with biosolids could not be considered free from pathogens for at least one year following amendment.
T90 as a tool for engineers: interest and limits
Authors: Guillaud J. F. , Derrien A. , Gourmelon M. , Pommepuy M.
Published: May 2018

Coastal management and water protection must provide acceptable water quality for shellfishing and tourist activities. To determine the impact of sewage on microbial water quality, engineers need to know the laws of bacterial reduction. In this study, experiments were performed with Escherichia coli in the laboratory and in situ (Atlantic and Mediterranean coast) using diffusion chambers at several depths. T90 was calculated from culturable bacterial counts over time. Establishing an abacus integrating the depth of water impacted by sewage and turbidity enabled us to calculate T90 from daily sunlight illuminations. Results obtained by cultures minimise health risks and yet viability and cellular integrity of E. coli remain, even under intense sunlight stress. When direct viable count is used to calculate a VT90, the results are dramatically higher and show how necessary – and difficult – it is to develop a concept which takes account of better understanding of sanitary risks in impact studies.
Biochemical fingerprinting of coliform bacterial populations – comparisons between polluted river water and factory effluents
Authors: Kühn I. , Allestam G. , Engdahl M. , Stenström T.-A.
Published: May 2018

Bacteria from different pollution sources may consist of essentially the same species but with different strains predominating. Therefore, sub-typing of bacterial strains recovered in the polluted water and comparison with those present in possible pollution sources is a valuable tool for identification of the source. Since such studies require investigations of large numbers of isolates, simple laboratory methods combined with automated data evaluation and presentation are necessary. The Phene Plate (PhP) system for biochemical fingerprinting of bacteria is based on measurements of the kinetics of biochemical tests, performed in micro-plates. The system also includes mathematical models to calculate the diversity (Di) of the bacterial flora within samples, as well as the similarities between bacterial populations in different samples as the population similarity coefficient (Sp). We have used the PhP system to type coliform bacteria isolated from a polluted river in Sweden and from the outlets from three paper mills that were suspected contamination sources. From each of 27 river water samples and 8 samples from factory outlets, collected on eight sampling occasions, between 10 and 50 coliforms were typed, yielding altogether 1,027 isolates. The diversity among the bacteria in river water samples was generally high (mean Di = 0.95) compared with factory outlets (mean Di = 0.63) which usually were dominated by isolates belonging to a few PhP types. These PhP types were very rarely recovered from the river water samples which is also reflected in low similarities between bacterial populations in river water and factory outlets (mean Sp = 0.03). Thus the bacteria from factory outlets did not seem to have spread downstream. In contrast, bacterial populations from sampling sites close to each other in the river were more similar to each other (mean Sp 0.13), indicating the presence of several, diffuse contamination sources, possibly from animal or human faecal material.
Immunomagnetic separation of Cryptosporidium oocysts from water samples: round robin comparison of techniques
Authors: Campbell A. , Smith H.
Published: May 2018

A prototype immunomagnetic separation (IMS) technique was tested in five laboratories, which undertake routine analysis of water samples for Cryptosporidium oocysts, by comparing the recovery efficiency of the IMS technique with techniques in current use (the “Blue Book” Standing Committee of Analysts, SCA, method and flow cytometry, FCM). In very low turbidity samples (clean waters) of both 1ml and 10ml volumes the IMS demonstrated significantly better results than both SCA and FCM methods. Not only were higher oocyst recovery efficiencies reported but variation in recovery efficiency was reduced and fewer negative results were reported from oocyst-seeded samples than with the other two techniques. In trials with clean water or low turbidity water, FCM was the technique which most consistently reported negative results in oocyst-seeded samples and for clean water this difference was found to be statistically significant. When the water sample was turbid the recovery efficiency of the IMS technique diminished. The results suggest that the IMS technique is affected to different extents by different material constituents in water concentrates and that FCM is apparently less affected by interfering particulate matter. Despite the potential difficulties with the IMS method with turbid water samples, the results from these trials indicate that this technique would be a very useful addition to the armoury of methods for the concentration of oocysts from water samples and was considered by the trial participants to be simple, user-friendly and applicable to the processing of multiple samples simultaneously.
Optimisation of the PEG reconcentration procedure for virus detection by cell culture or genomic amplification
Authors: Vilaginès Ph. , Suarez A. , Sarrette B. , Vilaginès R.
Published: May 2018

A double reconcentration procedure was developed for virus detection in tapwater concentrates obtained by conventional adsorption-elution techniques suitable for cell inoculation as well as for genomic amplification. Using 7.5% PEG 6000 and 2.5% NaCl, a 15min contact time under agitation at room temperature followed by centrifugation (first step: 3,500xg, 90min, 4°C; second step 10,000xg, 20min, 4°C) were the conditions to obtain overall average virus recovery efficiencies of 71% for poliovirus from 900ml eluates and 88, 83 and 75% for poliovirus, coxsackie B2 and rotavirus respectively (400ml eluates). Direct extraction of viral RNA from the first PEG pellet with TrizolTM was efficient for RT-PCR assays without any further treatment. Primer pairs were selected to amplify rotavirus group A and poliovirus in seeded tapwater concentrated by adsorption elution through glass wool. A positive signal was obtained for theoretic virus concentration of 1 PFU. Analysis of field samples (1001) by cell culture and genomic amplification resulted in a higher sensitivity with the latter.
Origins and characteristics of urban wet weather pollution in combined sewer systems: the experimental urban catchment “Le Marais” in Paris
Authors: Gromaire-Mertz Marie-Christine , Chebbo Ghassan , Saad Mohamed
Published: May 2018

An experimental urban catchment has been created in the centre of Paris, in order to obtain a description of the pollution of urban wet weather flows at different levels of the combined sewer system, and to estimate the contribution of runoff, waste water and sewer sediments to this pollution. Twenty-two rainfall events were studied from May to October 1996. Dry weather flow was monitored for one week. Roof, street and yard runoff, total flow at the catchment outlet and waste water were analysed for SS, VSS, COD and BOD5, on both total and dissolved fraction. Results show an evolution in the characteristics of wet weather flow from up to downstream: concentrations increase from the catchment entry to the outlet, as well as the proportion of particle-bound pollutants and the part of organic matter. A first evaluation of the different sources of pollution establishes that a major part of wet weather flow pollution originates from inside the combined sewer, probably through erosion of sewer sediments.
Analysis of the methods for determining the settling characteristics of sewage and stormwater solids
Authors: Lucas-Aiguier Emmanuelle , Chebbo Ghassan , Bertrand-Krajewski Jean-Luc , Gagné Benoit , Hedges Peter
Published: May 2018

In order to optimise the design and the management of sewer networks and settling tanks, there is a need to determine the settling velocity characteristics of sewage and stormwater solids. Devices and test methods for measuring settling velocities of these solids have been developed (Chebbo, 1992), (Michelbach and Wohrle, 1993) and (Tyack et al., 1993). In order to quantify the influence of the experimental procedure on the settling velocity grading curves, we have compared three selected methods (Cergrene, Aston, Camp) when tested with the same sample with the method developed by UFT (Michelbach and Wohrle, 1993). The results of the comparative tests indicate that the settling velocities are significantly higher with the UFT test procedure than the other methods. This is mainly explained by the fact that the UFT method takes only settleable solids into account. When the calculations of the four methods are made with the total mass of SS, the study has shown that the settling velocity curves of the same samples are different. The differences vary between the nature of the samples and the test procedures which were compared. The influence of the experimental procedure for separating a sample by settling velocities fractions is demonstrated. In conclusion, we explain the need to develop an international test procedure in order to be able to compare the results.
Factors affecting phosphorus removal in a two-stage intermittent aeration process treating domestic sewage
Authors: Zhao H. W. , Mavinic D. S. , Oldham W. K. , Koch F. A.
Published: May 2018

A bench-scale, continuous-flow, study was conducted to investigate the factors affecting phosphorus removal in a two-stage, intermittent aeration (IA) process. The two-stage process used consisted of an anaerobic zone and an intermittently aerated, completely mixed (IACM) tank, in which intermittent aeration was controlled by absolute ORP. The factors examined were the average ORP control level (used for aeration control), external acetate dosage, and intermittent aeration cycle. The degree of phosphorus removal in the two-stage IA process depended mainly on the presence of acetate in the anaerobic zone. The average ORP control level also affected the phosphorus removal at relatively low external acetate dosages. Small phosphorus release in the presence of nitrate and dissolved oxygen was observed during the air-off period. This suggests that a relatively long aeration cycle should be avoided in the two-stage IA process for preventing significant phosphorus release in the IACM tank.
Sewer solids management using invert traps
Authors: Fraser Alasdair G. , Ashley Richard M. , Sutherland Morven M. , Vollertsen Jes
Published: May 2018

During the 20th century, the once common practice of trapping sewer sediments at key locations within sewerage systems has lost favour with UK sewerage designers and, to a lesser extent, operators. The reasons for this include the perception of a priori unquantifiable maintenance, and the difficulties of sewer sediment extraction in town centres in an environmentally acceptable fashion. In order to assess the need for and requirements of such trapping systems, a survey of UK sewerage operators was carried out. The results of this survey have been used as a starting point to initiate the development of a design and operational methodology for the utilisation of traps. The survey highlighted the lack of guidance available and the importance of trap monitoring to enhance performance. A fill rate model is proposed for the design and operational aspects of cleaning and monitoring traps, using two of the most recently developed “near bed solids” transport equations. The model has been applied to a trap situated on a trunk sewer in the city centre area of Dundee. The pollution potential of trap and in-pipe sediments has also been assessed by considering the biodegradability of the sediment fractions likely to be released into the flow column during storm events.
Some physiological characteristics of a phosphate-removing bacterium, microlunatus phosphovorus, and a simplified isolation and identification method for phosphate-removing bacteria
Authors: Ubukata Y. , Takii S.
Published: May 2018

Some physiological characteristics of a phosphate (Pi)-removing bacterium, Microlunatus phosphovorus, are investigated using aerobically grown cells and cells exhibiting excess Pi accumulation (EPA) in order to determine a simplified isolation and identification method for other Pi-removing bacteria. Such a method would save on the amount of sterile equipment needed, and reduce the number of experimental steps and labor time. The EPA activity of the isolate reached a plateau 13 hours into the anaerobic incubation time, but it reached 70% of that level after only 5 hours. The EPA activity of the cells during the stationary growth phase was higher than that during the exponential growth phase. Polyphosphate (polyP) accumulated in the cells was shown to be used as an energy storage material (a phosphagen) under both aerobic and anaerobic conditions. During aerobic starvation, the rate of decrease in the ATP concentration of the suspension of cells that contained polyP was markedly less than that of the suspension of cells without polyP. Therefore, bacterial cells rich in polyP survive longer than bacterial cells lacking polyP.
Storm water quality modelling, an ambitious objective?
Authors: Ahyerre M. , Chebbo G. , Tassin B. , Gaume E.
Published: May 2018

As a consequence of the awareness of the pollution impact of storm sewer overflows, managers need tools to evaluate and control stormwaters according to water quality criteria. After an experience of 25 years in storm water quality modelling, very few models are widely and regularly used. According to managers this is due to their cost and their low level of accuracy.

The generation and the transport of the pollution in urban systems during a storm event are very complex because they concern many media and many space and time scales. Nevertheless, a typology of the existing models shows that this complexity has been inscribed into the models. This tendency towards complexity makes sewer quality models difficult to put into operation and three main difficulties can be underlined: doubtful mathematical formulation of processes, uncertainties on input and calibration data, difficulties and cost of calibration.

Further research is needed to improve the modelling approach and basic knowledge, and we think that a clear distinction should be made between management tools and research models.
A process and model concept for microbial wastewater transformations in gravity sewers
Authors: Hvitved-Jacobsen T. , Vollertsen J. , Nielsen P. H.
Published: May 2018

A fundamental and conceptual description of the microbial system in sewers in terms of wastewater organic matter transformations is presented. The description is examplified being under gravity sewer conditions and a conceptual model including main aerobic transformations is shown. The conceptual model of the microbial system basically agrees with the activated sludge model, (Henze et al., 1987). The model can be extended, e.g. to include anaerobic processes and processes taking place in resuspended sewer sediments under aerobic conditions. The concept for modelling transformations of wastewater during transport in sewers is recommended as the basis for further development.
Release of nitrous oxide (N2O) from denitrifying activated sludge caused by H2S-containing wastewater: quantification and application of a new mathematical model
Authors: Schönharting Barbara , Rehner Ruxandra , Metzger Jörg W. , Krauth Karlheinz , Rizzi Manfred
Published: May 2018

A new mathematical model is presented which describes the denitrification process by dynamic material balance equations. In this approach the kinetic rate expressions of the single denitrification steps and the observed strong inhibition of nitrate on nitrite and nitrous oxide reduction are based exclusively on fundamental enzyme kinetics. This allows a prediction of the denitrification process in a wide range of wastewater-relevant nitrate concentrations. The model was successfully applied to the description of the kinetic behavior of a standardized denitrifying activated sludge system. Furthermore the experimentally investigated influence of hydrogen sulfide was quantified by extending the model with a non-competitive inhibition mechanism involving all steps of the denitrification process. The inhibitory effect was related to the free membrane-permeable hydrogen sulfide concentration. This means that the extent of its inhibition depends additionally on the pH-value. Even very low hydrogen sulfide concentrations lead to a strong inhibition of nitrous oxide reduction and therefore to a high release of nitrous oxide from wastewater treatment plants.
Phosphate removal in real anaerobic supernatants: modelling and performance of a fluidized bed reactor
Authors: Battistoni P. , Pavan P. , Cecchi F. , Mata-Alvarez J.
Published: May 2018

Phosphate removal in anaerobic supernatant coming from a centrifugation sludge station of an A2O process is studied. A fluidized bed reactor is employed to crystallize phosphate as hydroxyapatite or struvite using only air stripping to reach the supersaturation pH. The classic composition of supernatant (alkalinity 3550 mgCaCO3/l, PO4 139 mg/l, Mg 24 mg/l) does not require any addition of chemicals for phosphate removal. Seventeen runs are performed in a bench scale FBR obtaining very high conversion and removal efficiency and phosphate loss in the effluent ≤3.5%. The use of Ca or Mg enriched supernatant has no meaningful influence on efficiency, but it determines the prevalent salt formed between MAP or HAP. Efficiency can be related to pH and sand contact time in a double saturational model. The half efficiency constants: 0.075 h for t and 7.75 pH, have an important role in the process knowledge and optimization of plant design. Exhaust sand analysis indicates the same composition at the top, bottom and mean of the sand bed (39% mol MAP and 61% mol HAP). This result together with the high half efficiency constant for contact time indicate that the phosphate growth on the bed is not competitive. Finally, the phosphate release from the plant is studied. Results show a weak release rate, equivalent to 2.8-10% d−1 phosphate as MAP, obtained at an operative pH range of 8.1-8.4.
Field examination on reed growth, harvest and regeneration for nutrient removal
Authors: Hosoi Y. , Kido Y. , Miki M. , Sumida M.
Published: May 2018

A wetland where aquatic macrophytes grow is expected to have the function of water purification. Nutrients assimilated by them are removed from the water by harvesting those plants. In order to carry out harvesting to remove nutrients effectively, it is essential to know the life cycle behavior of the plants. In this study, the characteristics of reed growth and regrowth after harvest were examined in the actual field. The height and number of the shoots, the standing biomass and nutrient contents were observed. The average height of living shoots reached its maximum when total sunshine duration was 500 hours since harvest. Nutrient contents showed the maximum value in the early growth stage. On the basis of these results, the numerical simulation model about the life cycle of the aboveground part of reed was developed to investigate nutrient removal efficiency by various harvest methods. It was recommended to harvest twice a year for the effective nutrient removal.
Rapid determination of fractal structure of bacterial assemblages in wastewater treatment: implications to process optimisation
Authors: Guan J. , Waite T. D. , Amal R. , Bustamante H. , Wukasch R.
Published: May 2018

A rapid method of determining the structure of aggregated particles using small angle laser light scattering is applied here to assemblages of bacteria from wastewater treatment systems. The structure information so obtained is suggestive of fractal behaviour as found by other methods. Strong dependencies are shown to exist between the fractal structure of the bacterial aggregates and the behaviour of the biosolids in zone settling and dewatering by both pressure filtration and centrifugation methods. More rapid settling and significantly higher solids contents are achievable for “looser” flocs characterised by lower fractal dimensions. The rapidity of determination of structural information and the strong dependencies of the effectiveness of a number of wastewater treatment processes on aggregate structure suggests that this method may be particularly useful as an on-line control tool.
The effects of macromolecular substrates and a metabolic inhibitor on volatile fatty acid metabolism in thermophilic aerobic digestion
Authors: Chu A. , Mavinic D. S.
Published: May 2018

The effects of spiking macromolecular substrates and an inhibitor on the metabolic behavioral patterns of thermophilic aerobic digestion (TAD) biomass, from a pilot scale system, were studied. The 3 macromolecules examined were linoleic acid (lipid), peptone (protein) and dextrin (carbohydrates). Linoleic acid did very little in terms of volatile fatty acid (VFA) stimulation in either anaerobic or microaerobic environments. Dextrin stimulated propionate and acetate production in a rough 2 propionate to 1 acetate molar ratio under anaerobic conditions. Peptone was the only one of the three tested substrates that stimulated only acetate production under fermentative conditions. Under microaerobic conditions (oxygen demand exceeds oxygen supply), both peptone and dextrin stimulated the production of acetate. The results seen under both anaerobic and microaerobic experimental conditions, with the exception of linoleic acid, in so far as redox balance is concerned, are consistent with the hypothesized biochemical mechanisms describing substrate metabolism in TAD proposed by Chu et al. (1996). Since fermentative reactions do not utilize oxidative phosphorylation to produce energy, 2,4-dinitrophenol had no measurable effect on VFA metabolism in an anaerobic environment. The effect of this agent under microaerobic conditions, was to induce the process biomass to switch from generating energy via oxidative means to using substrate level phosphorylation reactions. This results in the accumulation of large amounts of acetate in excess of the control condition that was not treated with 2,4-dinitrophenol, since acetate production from acetyl-Coenzyme A yields energy.
Sustainability in biosolids management
Authors: Matthews Peter
Published: May 2018

The paper reviews the latest position in interpreting the Global Atlas of sludge and biosolids management launched at the last biennial conference. It uses the principle of sustainability as a benchmark concept and gives examples of how this would look against the practical operations of Anglian Water in Eastern England.
Coagulation and sedimentation in lakes, reservoirs and water treatment plants
Authors: O′Melia Charles R.
Published: May 2018

Coagulation and sedimentation occur naturally in all lakes and reservoirs and, by design, in water treatment plants using surface supplies. Important factors that affect water quality in lakes and reservoirs include nutrient loading, areal hydraulic loading, and detention time together with the concentrations of land-derived (pedogenic) natural organic matter and hardness in waters entering the lake or reservoir. These, in turn, have important effects on the design and operation of potable water treatment systems. It is difficult and expensive to use the good physics to compensate for poor chemistry in water treatment plant design. There are many interesting and useful similarities among the physical and chemical characteristics of lakes, reservoirs, and water treatment plants.
Coliform transport in a pristine reservoir: modeling and field studies
Authors: Garvey Elisa , Tobiason John E. , Hayes Michael , Wolfram Evelyn , Reckhow David A. , Male James W.
Published: May 2018

This paper reports on field studies and model development aimed at understanding coliform fate and transport in the Quabbin Reservoir, an oligotrophic drinking water supply reservoir. An investigation of reservoir currents suggested the importance of wind driven phenomena, and that both lateral and vertical circulation patterns exist. In-situ experiments of coliform decay suggested dependence on light intensity and yielded an appropriate decay coefficient to be used in CE-QUAL-W2, a two-dimensional hydrodynamic and water quality model. Modeling confirmed the sensitivity of reservoir outlet concentration to vertical variability within the reservoir, meteorological conditions, and location of coliform source.
Problems and practical experiences during refilling of the Kerspe-Talsperre under unfavourable climatic conditions
Authors: Nienhüser A. E. , Braches P.
Published: May 2018

Refilling of the Kerspe-Talsperre reservoir after restoration of the dam caused severe problems in water quality and supply due to a long-lasting ice-cover period and minimal precipitation. Unusually short spring overturn, high algal mass in spring and certainly the overflooding of the sediment, which had not been removed, caused a tremendous oxygen deficit in early summer. The whole hypolimnion turned anoxic and even in the metalimnion oxygen declined to a minimum. Manganese and iron reached high concentrations. Despite the poor water quality, raw water was urgently needed for the water supply and was pumped from the epilimnion during the clear water phase and in July when algal biomass was low. In the middle of August holomixis was induced artificially in order to improve water quality. The decline in algal production during and after artificial mixing was probably caused by light limitation of the algae.
Landfill codisposal of pentachlorophenol (PCP)-treated waste wood with municipal solid waste
Authors: Pohland F. G. , Karadagli F. , Kim J. C. , Battaglia F. P.
Published: May 2018

Pentachlorophenol (PCP) has been used as a biocide and preservative for wood power poles and crossarms. If disposed in landfills, the natural capacity of landfills to transform hazardous constituents to less hazardous or inert substances may also apply to such PCP-treated materials. The principal reaction of interest in the anaerobic environment of a landfill is reductive dechlorination.

The fate and transformation of PCP-treated wood was investigated in simulated landfill bioreactors operated under single pass leaching and leachate recirculation. The wood samples consisted of 2% of the total mass by weight loaded into the bioreactors. The PCP leaching potential was examined at varying pH conditions with TCLP and Soxhlet extractions. Adsorption of PCP to the synthetic solid waste was used to determine its role in immobilizing leachate PCP. Routine indicator parameters were used to describe the acidogenic and methanogenic phases of landfill stabilization. Leached PCP was transformed without inhibitory effects on landfill stabilization, thereby affirming the acceptability of such a codisposal practice.
Technological and hygienic consequences of reservoirs eutrophication in the Czech Republic
Authors: Sládecková Alena , Žácek Ladislav
Published: May 2018

More than one half of drinking water demand in the Czech Republic is covered by surface water resources. The most frequent problems of the water treatment and supply are caused by the eutrophication of reservoirs. Biological parameters of drinking water quality based upon the microscopic analysis are included in local standards and commonly used in water works laboratories. Several new methods and criteria have been elaborated: microscopic evaluation of the separation efficiency of water treatment, categorization of microorganisms according to their separability, a screening bioassay for the assessment of biological stability of the water in course of the treatment and distribution, biological indicators of the eutrophication degree of reservoirs and their tributaries. A set of supplementary biological methods and criteria for special cases was published. Algal toxins have been detected not only in cyanobacterial water blooms in reservoirs but also in periphyton layers growing in different units of water works treatment trains. Two examples of the integrated system approach to the water supply from eutrophicated reservoirs inclusive of proposed preventive and remedial measures are selected from a recently finished extensive research project. Improvement actions in the resources protection, water works design and operation, laboratory control system and legislation are recommended.
Phosphorus elimination by longitudinal subdivision of reservoirs and lakes1
Authors: Paul Lothar , Schrüter Kurt , Labahn Jörg
Published: May 2018

An epilimnetic volume of nearly 350,000 m3 was separated by the installation of an overflown, submerged flexible curtain (SFC, 160 m long, 6 m deep) perpendicular to the flow direction in the Haselbach mouth region of the Saidenbach Reservoir (Saxony, Germany). The SFC produced (i) an interruption of hydraulic short circuits between inlet and main reservoir basin, (ii) a longer retention time of the inflowing water, and (iii) a 30% to 40% increase of the elimination of soluble reactive phosphorus in the mouth region during summer stratification. It is conclusive that flexible curtains may be cost-effective substitutes for conventional pre-dams of thermally stratified lakes or reservoirs.
Calibration of three resuspension/sedimentation models
Authors: Blom Gerard , Aalderink R. Hans
Published: May 2018

Three resuspension and sedimentation models (Blom, Lick and Partheniades and Krone) are calibrated and evaluated on data from flume experiments with sediments from Lake Ketel and in situ suspended solids measurements. We applied a formal parameter estimation technique in combination with a statistical evaluation of the model fit and parameter estimates. All three models produce a reasonable reconstruction of the data from the flume experiment and the in situ observations. The differences in the model fit of the three models are small, except for the in situ observations. Here the sum of squared residuals for Partheniades and Krone's is about twice the sum for Blom's and Lick's model. The correlation between parameters in resuspension/sedimentation models can be very high, leading to an uncertainty in parameter estimates of 25-50. The parameter estimations based on the flume data are up to orders of magnitude higher than those estimated from field observations.
Cyanobacterial dominance in the lakes Veluwemeer and Wolderwijd, The Netherlands
Authors: Reeders H. H. , Boers P. C. M. , van der Molen D. T. , Helmerhorst T. H.
Published: May 2018

The lakes Veluwemeer and Wolderwijd have long suffered from eutrophication stress. Recently, however, water quality has improved substantially. An overview of the developments in water quality (transparency, PTOT, chlorophyll) is presented for 1969-1996. Dominance of filamentous cyanobacteria in summer is analyzed. P-reduction is the key-factor to reduce cyanobacterial dominance. At PTOT>0.20 mg l−1 cyanobacterial dominance approaches 100%, at 0.05<PTOT<0.20 mg l−1 the dominance decreases rapidly, while at PTOT≤0.05 mg l−1 filamentous cyanobacteria virtually disappear. In the intermediate range for P summer dominance of cyanobacteria may be either high or low. The occurrence of these two states is related to the winter conditions and the global insolation in spring (April-May). Low summer dominances may occur after a severe winter. A severe winter results in a low inoculum of filamentous cyanobacteria, a mild winter in a high inoculum. High cyanobacterial dominance in summer is related to a high inoculum and/or high global insolation in spring. When the inoculum is low, i.e. after a severe winter, cyanobacterial dominance in summer may be either low or high. Low global insolation does not provide an indication for poor conditions for growth.