bluuebunny/crossref_metadata_2025 huggingface dataset:
A cost effective approach to stormwater management? source control and distributed storage
Authors: Andoh R. Y. G. , Declerck C.
Published: May 2018

Rapid urbanisation and its consequent increase in impermeable surface areas and changes in land use has generally resulted in problems of flooding and heavy pollution of urban streams and other receiving waters. This has often been coupled with ground water depletion and a threat to water resources.

The first part of this paper presents an alternative drainage philosophy and strategy which mimics nature's way by slowing down (attenuating) the movement of urban runoff. This approach results in cost-effective, affordable and sustainable drainage schemes. The alternative strategy can be described as one of prevention rather than cure by effecting controls closer to source rather than the traditional approach which results in the transfer of problems downstream, resulting in its cumulation and the need for large scale, centralised control.

The second part describes a research project which has been launched in order to quantify the cost and operational benefits of source control and distributed storage. Details of the methodology of the modelling and simulation processes which are being followed to achieve this target are presented.
Aspects of 25 years of Canadian experience with stormwater management lakes
Authors: Wisner Paul
Published: May 2018

The experience of older stormwater management (SWM) lakes in Canada shows that, even if peak flood reduction or effluent objectives requested by guidelines can be achieved, future public perceptions of lakes as an amenity were sometimes overestimated, and municipal rehabilitation efforts to avoid complaints can, in some situations, become significant. Analysis of limnologic performance and review of problems of older lakes was used in recent projects for the development of improved solutions for future lakes and a public consultation based on more realistic predictions.
Relationship between the morphology of bacteriophages and their persistence in the environment
Authors: Lasobras J. , Muniesa M. , Frías J. , Lucena F. , Jofre J.
Published: May 2018

The aim of the present work was to observe the morphological differences between bacteriophages from sewage, recent pollution and those from samples that contain microorganisms that have survived either natural inactivation or water treatment processes (persistent pollution). We studied the occurrence of bacteriophages infecting Bacteroides fragilis (HSP40 strain), F-specific coliphages (HS(pFamp)R strain) and somatic coliphages (CN13 strain). Phages isolated with B. fragilis in both wastewater and samples with persistent pollution were in all cases members of the Siphoviridae group with flexible tails. With E. coli strain HS(pFamp)R we detected F-specific coliphages in 97.7% wastewater. However, the percentage decreased to 76.9% in samples with persistent pollution. In the case of somatic coliphages in wastewater, detected using E. coli CN13, 91% of the phages belonged to the Myoviridae family and a 6% to the Siphoviridae family. In contrast, in persistent pollution samples, an increase of Siphoviridae phages was observed (up to 26.4%).
Microorganism removal in wastewater stabilisation ponds in maracaibo, Venezuela
Authors: Botero L. , Montiel M. , Estrada P. , Villalobos M. , Herrera L.
Published: May 2018

Waste stabilisation ponds are an efficient means of wastewater treatment in many parts of the world wherever suitable land is available at reasonable cost and solar energy is an abundant energy resource. This study evaluated the removal of total coliforms TC, faecal coliforms FC and coliphages C in waste stabilisation ponds functioning as a pilot system in the tropical climate of Maracaibo, Venezuela. Sampling points included raw sewage and each pond effluent. Turbidity, pH and temperature were recorded. The results for raw sewage show average levels of 4.1×106 TC, 2.8×106 FC and 7.0×105 C/100mL. Temperature, pH and turbidity ranges between 26–31°C, 6.2–9.5 and 15–98 NTU respectively. Removal of microorganisms in the three systems ranged between 93–98%. Despite the high removal efficiency of microorganisms, the final effluents showed average counts of 5.4×104−1.4×105 TC, 5.2×104−1.3×105 FC and 1.6×104−4.7×104 C/100mL. This study shows that the microbiological quality of the final effluents did not achieve the WHO water quality requirement for FC (103/100mL); therefore, they cannot be used for irrigation. Additional treatments, such as slow sand filtration, are needed in order to improve the quality of the water.
virus inactivation during disinfection of wastewater by chlorination and UV irradiation and the efficacy of F+ bacteriophage as a ‘viral indicator’
Authors: Tree J. A. , Adams M. R. , Lees D. N.
Published: May 2018

Wastewater disinfection has grown in popularity in recent years in the UK particularly for reducing faecal coliform levels in effluents impacting on bathing waters not compliant with EC Directive standards. Although disinfectants appear effective against bacterial indicators of faecal pollution, their efficiency against human viruses is still unclear. This has significance both for attainment of compliance with viral standards in the EC Bathing Waters Directive and, potentially, for protection against viruses likely to cause gastroenteritis. This study reports on bench scale disinfection of primary effluent treated with chlorination and secondary effluent treated with UV. Disinfection experiments comprised of wastewater, sterilised by gamma irradiation, seeded with monodispersed laboratory grown bacterial indicators (Escherichia coli and Enterococcus faecalis), human enterovirus (poliovirus) and F+ bacteriophage (MS2) – a potential ‘viral indicator’. Under the experimental conditions used, the inactivation of bacterial indicators was rapid in comparison to the inactivation of F+ bacteriophage which was very poor. Seeded poliovirus was significantly more susceptible to inactivation by chlorine and UV irradiation than F+ bacteriophage but was more resistant than bacterial indicators in both cases. These results indicate that the use of bacterial indicators alone to determine the effect of wastewater disinfection when using chlorination or UV irradiation underestimates human enteric virus inactivation, whereas the use of F+ bacteriophage is likely to give a conservative estimate of virus inactivation.
Survival of cryptosporidium parvum, escherichia coli, faecal enterococci and clostridium perfringens in river water: influence of temperature and autochthonous microorganisms
Authors: Medema G. J. , Bahar M. , Schets F. M.
Published: May 2018

Oocysts of Cryptosporidium parvum can survive for several months in surface water, one of the main factors determining their success in environmental transmission and thus their health hazard via water. Several factors in the environment, e.g. temperature, presence of predators and exo-enzymes will probably influence oocyst survival. The high persistence of oocysts may also limit the value of traditional faecal indicator bacteria. The aim of this study was to determine the rate at which C parvum oocysts, E coli, faecal enterococci and C perfringens spores die in surface water and the influence of temperature and the presence of autochthonous (micro)organisms on the die-off rate. Microcosms with autoclaved river water were inoculated with the organisms. Microcosms with untreated river water were inoculated with concentrated primary effluent containing the bacteria and with C parvum oocysts. Microcosms were incubated at 5°C or 15°C at 100rpm. Viability of oocysts was monitored by in vitro excystation and dye-exclusion; viability of the bacteria was determined on appropriate selective media. When pseudo first-order die-off kinetics were assumed, the die-off rate of oocysts at 5°C was 0.010 log10/d and at 15°C, 0.006–0.024 log10/d. These rates underestimate die-off since oocyst disintegration was not accounted for. Incubation in autoclaved or untreated water did influence the die-off rate of oocysts at 15°C but not at 5°C. The die-off rate of E coli and enterococci was faster in the non-sterile river water than in autoclaved water at both temperatures. At 15°C, E coli (and possibly E faecium) even multiplied in autoclaved water. In untreated river water, the die-off of E coli and enterococci was approximately 10x faster than die-off of oocysts but die-off rates of C perfringens were lower than those of oocysts. As for oocysts, die-off of the bacteria and spores was faster at 15°C than at 5°C. Oocysts are very persistent in river water: the time required for a 10x reduction in viability being 40–160d at 15°C and 100d at 5°C. Biological/biochemical activity influenced oocyst survival at 15°C and survival of both vegetative bacteria at 5 and 15°C. The rapid die-off of E coli and enterococci makes them less suitable as indicators of oocyst presence in water. As C perfringens survived longer in untreated river water than oocysts, it may prove useful as an indicator of the presence of C parvum.
Development of a rapid method for the enumeration of bacteria in potable water
Authors: Reynolds D. T. , Fricker E. J. , Purdy D. , Fricker C. R.
Published: May 2018

Two viability substrates, ChemChrome B and 5-cyano-2,3,4-tolyl-tetrazolium chloride (CTC) were compared with the traditional pour plate method for the enumeration of bacteria in potable water samples. ChemChrome B stained cells were counted, on a membrane, using a novel laser scanning device whereas CTC stained cells were counted using epifluorescence microscopy. A significantly higher number of bacteria were detected using the viability assays than by culture, which highlights the inefficiency of current culture techniques. Results with ChemChrome B illustrate that the use of a laser scanning device provides an efficient method for the enumeration of fluorescently labelled microorganisms.
Full scale evaluation of nitrification performance in an integrated fixed film activated sludge process
Authors: Jones R. M. , Sen D. , Lambert R.
Published: May 2018

The nitrification performance of an integrated fixed film activated sludge (IFAS) process was compared to a parallel control system at full scale. The IFAS process utilized the Ringlace and Biomatrix looped cord media products. Monitoring and evaluation of the retrofit was divided into two periods. The first monitoring period was from October 3, 1995 to June 20, 1996. The second monitoring period was started on December 2, 1996 and was completed on March 28, 1997. During the first operating period, the maximum media nitrification rate was estimated to be 0.42 kg/d/1000 m of media at an average temperature of 10°C. Settling was also improved. To correct flow short circuiting observed during the first operating period additional aerators were mounted below the media frames and baffles were mounted above existing diffusers. Nitrification performance of the media during the second operating period was found to be marginal. Although the nitrification performance in the control train was not stressed to the same degree as in the 1995/96 period, the likely main cause of the deteriorated performance of the media was a proliferation of bristle worm in the biofilm. The results of this study indicate that proper aeration design, and the prevention and treatment of worm blooms are two important issues in the application of the IFAS process.
The effect of sulphide and organic matter on the nitrification activity in a biofilm process
Authors: Æsøy Anette , Ødegaard Hallvard , Bentzen Greta
Published: May 2018

Septic wastewater, characterised by the appearance of sulphide, is known to cause problems in sewage systems (corrosion and odour), at treatment plants (e.g. inhibition, sludge bulking) and for human beings (toxicity). Sulphide formation in sewers may be prevented by increasing the redox potential, either by oxygen/air injection (aerobic conditions) or dosage of nitrate (anoxic conditions). The effect on the nitrification capacity in a biofilm process of an anoxic wastewater as compared to a septic wastewater has been studied. The main change in wastewater quality as a result of nitrate dosage is reduced concentrations of organic matter and insignificant sulphide concentrations. The results show that a sulphide concentration of 0.5 mg/l had a considerable negative effect on the nitrification activity. The sulphide and the higher concentrations of organic matter in the septic wastewater caused together a 30-40% reduction of the nitrification capacity as compared to the anoxic wastewater, even with pre-aeration and pre-precipitation with Fe3+. The removal of organic matter in the sewer as a result of the anoxic conditions created by the addition of nitrate, resulted in a maximum nitrification capacity when particulate organic matter was removed by pre-precipitation.
Energetics of enhanced biological phosphorus and nitrogen removal processes
Authors: Tonkovic Zlatko
Published: May 2018

Recent advances by researchers with in vivo NMR spectroscopy using labelled isotopes of carbon and phosphorus have elucidated some of the biochemical pathways involved in enhanced biological phosphorus and nitrogen removal processes. This has permitted a greater understanding of carbon and phosphorus cycling within cellular processes.

All microbiological processes associated with energy transformations are dependent on enzyme induction. The enhanced phosphorus removal apparatus in certain organisms is dependent on the environmental conditions in order to induce the necessary enzymes. Enzyme expression has been linked to redox potential, which itself is a function of the culture medium and the bioenergetic condition of the cells. Redox balance is coupled to several pathways in the metabolic network of microorganisms. Changes to the redox potential result in shifts in the metabolic pathway utilisation.

In the past, nitrification and denitrification have been thought to be strictly aerobic and anoxic processes respectively. Mounting evidence has demonstrated that this classical view of nitrification and denitrification is no longer valid and that other processes can occur such as simultaneous nitrification and denitrification and aerobic denitrification. Enzyme induction plays a very important role in these processes.

Attempts have been made in this paper to elucidate the energetics of anaerobic phosphorus release based on cellular composition and various other plant operating parameters. Energetics of the denitrification process including anoxic dephosphatation, aerobic denitrification, with potential reduction in aerobic treatment requirements, are also explored.
Incorporating concepts from physical theory into stochastic modelling of urban runoff pollution
Authors: Grum Morten
Published: May 2018

On evaluating the present or future state of integrated urban water systems, sewer drainage models, with rainfall as primary input, are often used to calculate the expected return periods of given detrimental acute pollution events and the uncertainty thereof. The model studied in the present paper incorporates notions of physical theory in a stochastic model of water level and particulate chemical oxygen demand (COD) at the overflow point of a Dutch combined sewer system. A stochastic model based on physical mechanisms has been formulated in continuous time. The extended Kalman filter has been used in conjunction with a maximum likelihood criteria and a non-linear state space formulation to decompose the error term into system noise terms and measurement errors. The bias generally obtained in deterministic modelling, by invariably and often inappropriately assuming all error to result from measurement inaccuracies, is thus avoided. Continuous time stochastic modelling incorporating physical, chemical and biological theory presents a possible modelling alternative. These preliminary results suggest that further work is needed in order to fully appreciate the method's potential and limitations in the field of urban runoff pollution modelling.
An investigation of fine sediment mixing within free-flowing and surcharged manholes
Authors: Guymer I. , O'Brien R. , Mark O. , Dennis P.
Published: May 2018

Previous studies of the effects of manholes on longitudinal dispersion has concentrated on the spreading of solutes. This papers presents new data describing the influence of a surcharged and free-flowing manhole structure on the longitudinal dispersion of a fine suspended material. The effects of benching within the manhole structure are also illustrated. Laser Induced Fluorescence (LIF) techniques have been used to provide a qualitative description of the mixing processes present within a surcharged manhole. Nephelometric results have provided estimates of the parameters required to simulate the mixing effects using either increase in variance or aggregated dead zone techniques. A preliminary attempt at describing these observations using available software is discussed and recommendations for future developments are made.
Simultaneous nitrification-denitrification in a fluidized bed reactor
Authors: Sen Priyali , Dentel Steven K.
Published: May 2018

This paper describes simultaneous nitrification-denitrification (SND) in a fluidized bed reactor (FBR) without physical separation of the aerobic and anoxic zones. Continuous reactor SND trials demonstrated successful SND over distinct periods. Control was achieved by varying the reactor dissolved oxygen and the feed COD, although optimal performance could not be consistently maintained. Batch studies, using cultures from different vertical sections, demonstrated that variation of the bulk parameters successfully stratified the reactor bed into zones that predominantly either nitrified or denitrified. Evidence also indicated that both types of activity occurred throughout the FBR.
Wastewater fermentation and nutrient removal in sequencing batch reactors
Authors: Cuevas-Rodríguez Germán , González-Barceló Óscar , González-Martínez Simón
Published: May 2018

This research project was conducted to analyze the performance of a SBR reactor when being fed with anaerobically fermented wastewater. Important was to determine the capacity of the system to remove nitrogen and phosphorus. Two SBR reactors, each one with a volume of 980 liters, were used: one used as fermenter and the other as activated sludge SBR. Using 8-hour cycles, the reactors were operated and studied during 269 days. The fermenter produced an effluent with an average value of 223±24 mg/l of volatile fatty acids. The activated sludge SBR was tested under 3 organic loading rates of 0.13, 0.25, and 0.35 kgCODtotal/kgTSS·d. For the three tested organic loading rates, PO4-P concentrations under 1.1 mg/l and COD between 37 and 38 mg/l were consistently achieved. Exceptionally high NH4-N influent values were measured during the time of the experimentation with the organic load of 0.25 kgCODtotal/kgTSS·d, not reaching in this case full nitrification. Denitrification was observed during the fill phase in every cycle. SVI values between 40 and 70 were determined during the experimental runs.
The Actiflo method
Authors: Plum Victoria , Dahl Claus P. , Bentsen Leif , Petersen Carsten R. , Napstjert Lis , Thomsen N. B.
Published: May 2018

The Actiflo method is a compact physico-chemical water treatment method. The method has for many years been used in waterworks for the treatment of surface water to produce drinking water, but is now to an increasing extent being used for treating wastewater and combined sewer overflows (CSO). The method works as weighted settling combined with lamella settling. Typical treatment efficiency: suspended solids 85%, COD 60%, Kjeldahl N 18% and total P 85%. The method also permits efficient removal of heavy metals. Krüger has a mobile pilot plant with a capacity of 80-120 m3/h in Scandinavia and a similar pilot plant in the USA. As an Actiflo plant can be started up in less than 15 minutes, it has many applications. Several applications may also be combined, e.g. treatment of overflows during rain and treatment of lake water in the recipient nearby in dry weather. As an alternative to detention basins in combined sewer systems the Actiflo method is often a competitive method.
Tracing volatile organic compounds in sewers
Authors: Haas Bettina S. , Herrmann Reimer
Published: May 2018

A combined method of passive and active sampling of volatile organic compounds (VOCs) in a sewer system is presented. Passive sampling devices are used to locate and identify volatile organic compounds in the sewer atmosphere. Passive sampling is a time-integrating method and its results are only qualitative. To get quantitative information active sampling of wastewater is necessary. Concentrations of VOCs obtained from active sampling are used as input values for a simplified form of the two-film-model. This model allows to compute concentrations of VOCs at different points in a sewer stretch. We employed this method to describe the behaviour of volatile chlorinated hydrocarbons within a sewer stretch in Bayreuth, Germany.
Application of constructed wetlands for domestic wastewater treatment in an arid climate
Authors: Mandi L. , Bouhoum K. , Ouazzani N.
Published: May 2018

The present study consists in assessing the efficiency of a constructed reed bed for domestic wastewater purification under an arid climate. The experimental system is made up of four beds differing in length (20, 30, 40 and 50 m) and planted with Phragmites australis. Raw domestic wastewater inflow through these beds is horizontal with a flow of 10 litres per second. Hydraulic application rate varies between 0,86 to 2,16 m3.m−2.day−1. The frequency of irrigation is weekly. The studied parameters are: the organic load (COD and TSS), nutrients (total Kjeldhal nitrogen: TKN, NH4, total phosphorus: TP, PO4) and the parasitical load (helminth eggs).

Results shows that the constructed reed beds are efficient in reducing organic load (TSS: 58% to 67%; COD:48% to 62%) and parasitical load (Helminth eggs: 71% to 95%) in arid climates even with high hydraulic application rate. However, reduction of nutrient concentrations by the four beds is slight (TKN: 23 to 43%; NH4: 18 to 41%; TP: 5 to 17%; PO4: −9 to 13%). At the hot period (March to August), the reed beds seem to be more efficient in reducing organic load, nutrients and parasitical load. This period coincides with the reed's exponential growth phase. Moreover, the largest bed (50m in length) showed the best efficiency in the removal of nutrients (TKN: 53%; NH4: 61%; TP: 30%; PO4: 14%) and parasitical load (helminth eggs: 99%). This is due to its lowest application rate (0,86 m3.m−2.day−1).
Chromium speciation in municipal solid waste: effects of clay amendment and composting
Authors: Goen Ho , Liang Qiao
Published: May 2018

The addition of clay in the form of bauxite refining residue (red mud) prior to composting has been suggested as a way to control heavy metal mobility in compost. Leachability and plant availability of metals in a mixture of grass clippings and sawdust spiked with metal solution was markedly reduced during the composting process. The fate of metals in municipal solid waste compost applied to land was examined by using a sequential step extraction to investigate metal speciation (into exchangeable and bound to carbonate forms, to Mn & Fe oxides, to organic matter and in residue phase) in red mud amended compost. The effects of red mud and the composting process on metal speciation in the compost for Cd, Cr, Cu, Ni, Pb and Zn were investigated, and a comparison of some effects with biosolids compost was made. Addition of red mud reduced the metal mobility and the potential hazard of releasing metals from compost through promoted precipitation, adsorption and complexation of free metal cations to red mud. Red mud however, was not able to desorb metals bound to organic matter. Since most of the metals in the municipal solid waste were not usually bound to organic matter, the addition of red mud prior to composting fixed the free metal ions before they bound to this fraction. Results for Cr speciation are reported in this paper.
Efficiency control of particle removal by rapid sand filters in treatment plants fed with reservoir water: a survey of different methods
Authors: Clasen Jürgen
Published: May 2018

Particle removal is one of the main objectives of rapid sand filters. The particles to be removed are considerably different regarding size, shape and nature. They are either imported from the catchment area or formed in the reservoir. With the exception of storm events in central Europe the latter are in the majority of cases the most important ones. These are different plankton organisms comprising phyto- and zoo-plankton as well as bacteria and protozoa. Other particles are formed by the precipitation of manganese, iron or calcium. There exists a great variety of methods for the quantification of these particles in raw and filtered water, the most important being turbidity measurement, particle counting, microscopic investigation, counting CFUs as well as SON (suspended organic nitrogen) and chlorophyll analysis. Which method is to be preferred depends on the local conditions and on the problem to be investigated.
Effects of detergent zeolite in a nitrogen removal activated sludge process
Authors: Piirtola L. , Hultman B. , Löwén M.
Published: May 2018

Two detergent zeolites, Doucil-P and Doucil-A24, were tested for their weighting effect in batch tests and on a nitrogen removal activated sludge process. The batch tests with a long contact time revealed a negative effect of zeolite on sludge filterability. In continuous pilot tests, the zeolite accumulated in sludge causing an increase in sludge suspended solids of up to 25 to 30%. This accumulation improved the activated sludge settling characteristics. The zeolite did not affect the treatment efficiency or the amount of filamentous bacteria. Measurements were made on sludge surface characteristics, i.e. specific surface area, surface potential and surface energy. A slight increase in surface area and decrease in negative surface charge caused by zeolite addition was observed. The aluminium concentrations in sludge increased but there was no correlation to the concentration of the accumulated zeolite in sludge.
Preozonation coupled with flotation filtration: successful removal of algae
Authors: Montiel Antoine , Welté Bénédicte
Published: May 2018

The renovating of a new water treatment plant in Paris which produces 15% of the capital's drinking water supply is described: an original treatment plant consisting of a preozonation, a flotation with a low level of coagulant coupled with contact coagulation. Coagulation on filter has been tested on a pilot plant. The results are excellent (95 to 99%) and have led to the building of a new water treatment plant with very flexible operating conditions depending on the quality of the water.
The significance of algae as trihalomethane precursors
Authors: Graham Nigel J. D. , Wardlaw Valerie E. , Perry Roger , Jiang Jia-Qian
Published: May 2018

The objective of this study was to assess the relative importance of algae and algal derived organic precursors in the generation of Trihalomethane compounds (THMs). Laboratory tests have been carried out using cultures of two common algal species dominating natural reservoir populations to assess the importance of species, growth phase and biomass versus Extracellular product (ECP) in THM production. The results of the study showed that THMFP of algae cells and ECP increased with culture age. THM formation from cells was more than double that from ECPs for Asterionella formosa and Anabaena flosaquae. It is predicted that typical blooms in a reservoir of either species could produce a substantial fraction of the THM's formed during chlorination.
Activated sludge as a possible source of biodegradable plastic
Authors: Satoh H. , Iwamoto Y. , Mino T. , Matsuo T.
Published: May 2018

Polyhydroxyalkanaote (PHA) is known to be temporarily stored by microorganisms in activated sludge especially in the anaerobic-aerobic processes. When PHA is extracted from activated sludge, it is a thermoplastic with the remarkable characteristics of biodegradability. We investigated the possibility of using activated sludge for the production of PHA, focusing on increasing the PHA content of activated sludge. Activated sludge from laboratory scale anaerobic-aerobic reactors accumulated PHA of around 20% under anaerobic conditions and up to 33% under aerobic conditions. In order to further increase the PHA content of activated sludge, we introduced the “microaerophilic-aerobic” process, where a limited amount of oxygen is supplied into the anaerobic zone of the anaerobic-aerobic process. Activated sludge acclimatized in the microaerophilic-aerobic process accumulated PHA of as much as 62% of sludge dry weight. The “microaerophilic-aerobic” process was demonstrated to be an effective process for the enrichment of PHA-accumulating microorganisms.
Preliminary evaluation of the performance of new pre-polymerised inorganic coagulants for lowland surface water treatment
Authors: Jiang Jia-Qian , Graham Nigel J. D.
Published: May 2018

This paper is concerned with the performance of relatively new kinds of pre-polymerised inorganic coagulants, poly-alumino-iron-sulphate (PAFS) and polyferric sulphate (PFS). Laboratory experiments were undertaken to evaluate the PAFS and PFS, in comparison with conventional coagulants such as ferric sulphate (FS) and aluminium sulphate (AS), for the coagulation of algal-type model waters and a lowland surface water containing algae and natural organic matter (NOM). Experimental results demonstrated that under the conditions studied, the performance of pre-polymerised coagulants were consistently superior to conventional coagulants (i.e., FS and AS). This is attributed to the presence of a range of pre-formed polymerised species. The coagulation mechanism of PAFS and PFS has been discussed in the paper.
A modeling approach to simulate impact of climate change in lake water quality: phytoplankton growth rate assessment
Authors: Hassan Hany , Hanaki Keisuke , Matsuo Tomonori
Published: May 2018

Global climate change induced by increased concentrations of greenhouse gases (especially CO2) is expected to include changes in precipitation, wind speed, incoming solar radiation, and air temperature. These major climate variables directly influence water quality in lakes by altering changes in flow and water temperature balance. High concentration of nutrient enrichment and expected variability of climate can lead to periodic phytoplankton blooms and an alteration of the neutral trophic balance. As a result, dissolved oxygen levels, with low concentrations, can fluctuate widely and algal productivity may reach critical levels. In this work, we will present: 1) recent results of GCMs climate scenarios downscaling project that was held at the University of Derby, UK.; 2) current/future comparative results of a new mathematical lake eutrophication model (LEM) in which output of phytoplankton growth rate and dissolved oxygen will be presented for Suwa lake in Japan as a case study. The model parameters were calibrated for the period of 1973–1983 and validated for the period of 1983–1993. Meterologic, hydrologic, and lake water quality data of 1990 were selected for the assessment analysis. Statistical relationships between seven daily meteorological time series and three airflow indices were used as a means for downscaling daily outputs of Hadley Centre Climate Model (HadCM2SUL) to the station sub-grid scale.
Application of computational fluid dynamics technique to storage reservoir studies
Authors: Ta C. T. , Brignal W. J.
Published: May 2018

The flow dynamics in Grimsbury reservoir is studied using Computational Fluid Dynamics (CFD). Under no wind condition, flows circulate in the horizontal plane. These circulations, in general, lead to short circuiting and zones of stagnation. Modifications to the inlet and the outlet are investigated to maximise the residence time. They include the manifold inlet arrangement, the submerged baffle inlet and the central outlet arrangement.

The results of the residence time simulation indicate that the manifold inlet option gives the best ‘plug-flow’ efficiency, next the submerged baffle option and finally the central outlet option. The submerged baffle inlet option, however, is considered to be the preferred option because of its low installation cost and because of the reasonable balance between the degree of mixing and the residence time.
Use of computational fluid dynamics to model reservoir mixing and destratification
Authors: Cox Julian D. , Padley Martin B. , Hannon Joe
Published: May 2018

Destratification of reservoirs by the use of artificial mixing is a method of improving the impounded water quality. In order to design a destratification device at Stocks Reservoir, NW England, a Computational Fluid Dynamics model was used to trial different types and sizes of mixing device. It was found that a perforated pipe bubble mixing device performed far better than a large banana blade mixer at destratifying Stocks Reservoir. Two important criteria for the effective operation of a mixing device were established. These were a minimum upflow velocity of entrained water through the reservoir, and the need for a reverse flow along the surface of the reservoir away from the abstraction point. These criteria have been incorporated into design equations which can be extended to use at other reservoirs. A bubble mixer was installed at Stocks Reservoir, and has been shown to fully destratify the reservoir and to reduce the levels of dissolved manganese in the water by more than 50%.
A study on the role of hydraulic retention time in eutrophication of the Asahi River Dam reservoir
Authors: Kawara Osami , Yura Eisaku , Fujii Shinobu , Matsumoto Toyohisa
Published: May 2018

The Asahi River Dam reservoir is one of the important freshwater resources for Okayama City, Japan. The eutrophication of the reservoir has been warned of since the 1980s. In this study, we discuss the relationship between hydraulic retention time and increase of phytoplankton, and the influence of wind-driven currents on the spatial distribution of phytoplankton based on the observations and numerical simulations. Observations were carried out from 1993 to 1995. The numerical simulation of hydraulics in the reservoir was carried out by applying an orthogonal curvilinear finite difference method. Judging from phosphorus and nitrogen concentrations, the water quality of the Asahi River Dam reservoir is usually eutrophic. However, high concentrations of chlorophyll-a are not always observed. The observed dependence of chlorophyll-a concentration on hydraulic retention time is reproduced fairly well by a simple relationship derived from the balance of phytoplankton based on the assumption of complete mixing. The hydraulic retention time is a limiting factor of an increase in phytoplankton in the Asahi River Dam reservoir. It takes a retention time of 2 weeks for the sufficient increase of phytoplankton. The results obtained by the simulations show that the wind-driven currents play an important role in the spatial distribution of phytoplankton.
Case study: automatic reservoir aeration to control manganese in raw water Maryborough town water supply Queensland, Australia
Authors: Burns Frank L.
Published: May 2018

The city of Maryborough in Queensland, Australia, is supplied with treated water from the 8.6m maximum depth, 3.5 mill m3 capacity, Teddington weir - a long sinuous storage formed by damming a 15km length of Tinana Creek. Thermal stratification in this semi-tropical storage produced problems at the water treatment plant due to manganese release from the bottom sediments under low oxygen conditions leading to high and fluctuating levels of manganese in the raw water. Automatic aeration, controlled by temperature sensors, was installed in the storage in January 1996 to maintain continuous unstratified well oxygenated conditions in the storage. The result has been a significant general reduction in manganese and its variability in the raw water.
Integrated water quality management of the große dhünn reservoir
Authors: Scharf Wilfried
Published: May 2018

In this paper I introduce protection measures and management options which are applied to the watershed as well as to the reservoir itself and later their impact on water quality is discussed. Emphasis is given to nutrients from non-point sources and nutrient removal from such sources by pre-reservoirs is considered in detail. Phosphorus removal has to work mainly during flood events, when most of the nutrient load enters the reservoir. As our results reveal, 55% of the total annual TP-input can be removed in pre-reservoirs. I also introduce our concept of fishery management, which involves stocking the reservoir with lake trout (Salmo trutta lacustris) and pike perch (Stizostedion lucioperca). The advantage of having lake internal management options available, i.e. selective take-off from raw waters, is also considered in the case of development of metalimnetic blue-green algal (Planktothrix) populations. Preparatory measures i.e. cleaning of the reservoir basin, which has to be done before the rivers are impounded, are discussed. “Trophic upsurge”, in the sense of nutrient leaching, was not important during the first filling years. Improvements in water quality during the “ageing process” are due to lake internal mechanisms, i.e. the increase of sedimentation capacity and decrease of the ratio of epi- to hypolimnetic water volume, which were supplemented later by sewage diversion. Our results present ample evidence that it is due to our philosophy of integrated water quality management that Große Dhünn Reservoir is oligotrophic today - always able to fulfil its purposes.
Development of water quality management strategies for the proposed isikli reservoir
Authors: Gündüz Orhan , Soyupak Selçuk , Yurteri Coskun
Published: May 2018

A two-dimensional laterally averaged hydrodynamic and water quality model (CE-QUAL-W2) is used to simulate the water quality behavior in the proposed Isikli Reservoir of the Ankara Water Supply System to determine appropriate strategies for the management of water quality.

Isikli application of the model is used to demonstrate the potential water quality degradation patterns in the reservoir under different pollution loads. The results of the modeling study are compared with the drinking water quality standards currently effective in Turkey to formulate various water quality management strategies for the reservoir and its catchment area. In addition, various treatment options are evaluated considering the existing treatment system of Ankara City.

Based on the findings of this study, treatment or interception of wastewaters originating from the existing pollution sources around the reservoir area are introduced as the major infrastructural control techniques. Further, establishment of protection zones around the reservoir and relocating the possible pollution sources to a point downstream of the dam axis are found to be the most applicable administrative control methods for water quality preservation in the proposed reservoir.
A generalized settling approach in the numerical modeling of sedimentation tanks
Authors: Mazzolani G. , Pirozzi F. , d'Antonoi G.
Published: May 2018

Numerical models for the prediction of turbulent flow field and suspended solid distribution in sedimentation tanks are characterized by refined modeling of hydrodynamics, but apparently weak modeling of settling properties of suspensions. It is known that sedimentation tanks typically treat highly heterodisperse suspensions, whose concentrations range from relatively high to low values. However, settling is modeled either by considering one or more particle classes of different settling velocity, without accounting for hindered settling conditions, or by treating the suspension as monodisperse, even in regions of low concentration.

A new generalized settling model is proposed to account for both discrete settling conditions in low concentration regions of the tanks and hindered settling conditions in high concentration regions. Settling velocities of heterodisperse suspensions are then determined as a function of particle velocities in isolation and their total concentration. The settling model is used in the framework of a transport model for the simulation of hydrodynamics and solid distribution in a rectangular sedimentation tank. Results show that solid distribution is mainly affected by particle interactions in the inlet region and by settling properties of individual particles in the outlet region. Comparison of the proposed settling model with other settling models suggests that a generalized approach of the modeling of settling properties of suspensions is a primary concern to obtain reliable predictions of the removal rate.
Pure oxygen desorption method - a new and cost-effective method for the determination of oxygen transfer rates in clean water
Authors: Wagner Martin R. , Poöpel H. Johannes , Kalte Peter
Published: May 2018

Many clean water tests with the well known absorption method using sodium sulphite for deoxynation have shown that there are problems connected with solving these chemicals. Because of this, a new test method was developed at the Darmstadt University of Technology to determine oxygen transfer rates fine bubble aeration systems without sodium sulphite and a cobalt catalyst. The new method is called “Pure oxygen desorption method”. Contrary to the absorption method, the oxygen concentration in the test tank is increased well above the normal oxygen saturation concentration. This high excess concentration is obtained by feeding pure oxygen into the main pipe of the fine bubble aeration system. After starting normal aeration, the oxygen concentration in the clean water decreases towards the oxygen saturation concentration by stripping of the excess oxygen. The desorption curve is used to calculate the parameter aeration coefficient kLa and oxygen saturation concentration under process conditions c∞*. In comparison to the absorption method with sodium sulphite, the pure oxygen desorption method is a simple and cost-effective method for determining oxygen transfer rates.
Eutrophication vulnerability analysis: a case study
Authors: Vieira José M. P. , Pinho José L. S. , Duarte António A. L. S.
Published: May 2018

River Cavado water quality variability was studied for eutrophication vulnerability assessment at a new surface water supply intake. Since the river flow regime is artificially controlled by upstream multipurpose reservoirs, mathematical modelling was applied in evaluating alternative management scenarios. Due to the fact that surface water quality at intake location is mainly affected by a wastewater treatment plant effluent discharge 5 km upstream, algae and nutrients concentration simulations have been worked out in order to identify critical situations. Different algal concentration profiles along the river were obtained for local conditions of light energy, water temperature and estimated nutrient loads, showing high probability of eutrophication occurrence for some of the simulated scenarios. The discussion of results of this study appears to be very useful for river basin wide water management policies evaluation.
Modelling benthic activity in shallow eutrophic rivers
Authors: Rauch W. , Vanrolleghem P. A.
Published: May 2018

In this paper a simple modelling approach is presented that allows fast computation of benthic activity in rivers. The approach extends the half-order reaction concept used in biofilm models for use in a multiple substrate/multiple bacterial species system. Moreover, it is compatible with the IAWQ Activated Sludge Model no. 1 format and has closed mass balances. The conversion of carbonaceous organic matter under aerobic and anoxic conditions and nitrification are represented in the model. The case study to which it was applied revealed that benthic activity is highly influenced by the eutrophic state of the river (presence/absence of algae) leading to diurnal oxygen fluctuations. More specifically the spatial distribution of species along the river was significantly different, resulting in postponed (downstream) nitrification in the eutrophied river. Also, oxygen depletion is found to be more severe and its spatial extension is larger.
Coagulation monitoring in surface water treatment facilities
Authors: Chichuan Kan , Chihpin Huang
Published: May 2018

Coagulant dosing is traditionally determined according to results from jar-tests or operator's experience, which often lead to overdosing or insufficient dosing. In this study, the feasibility of applying an optical monitoring technique to determine chemical dosage and to monitor the coagulation performance in water treatment plants were assessed. To examine the applicability of the monitor under various operation conditions, series of batch trials in the field were conducted to explore the effects of turbidity, pH and rapid mixing intensity on the effectiveness of coagulation. The performance was directly reflected in the output ratio of the monitor, which proved to be an effective index for the floc size and its settling velocity. Therefore, we consider that the optical monitor is an useful instrument in monitoring coagulation in water treatment.
Decoloration system using rotating membrane UF module
Authors: Ohnishi Makoto , Okuno Yutaka , Ohkuma Naoki
Published: May 2018

A wastewater reclamation system using a rotating membrane UF module has been studied by adding a powdered activated carbon to a biological treatment process to remove the organic colored matter. In this system, a powdered activated carbon dosage of 50 mg/l, and retention time of 4.5 hours have been required to stably obtain a treated water with a color of less than 5 degrees. It was found that the activated sludge dewaterability could be improved by adding the powdered activated carbon and the rotating membrane UF module could operate at a set flux of 1.0 m3/m2·d for about one and half years.
Impact of water quality and reactor hydrodynamics on wastewater disinfection by UV, use of CFD modeling for performance optimization
Authors: Janex M. L. , Savoye P. , Do-Quang Z. , Blatchley E. , Laîné J. M.
Published: May 2018

In order to ensure reliable operating conditions for adequate wastewater disinfection in a UV reactor, two aspects were investigated as having a critical impact on the disinfection performances: water quality and hydrodynamics of the water flow through the system. Tests performed with a collimator on several wastewater effluents enabled us to relate the UV inactivation to the total suspended solids content of the water to be treated, the influence being decisive under 5 mg/l TSS. On the other hand, a CFD (Computational Fluid Dynamics) numerical tool was used to provide an accurate characterization of the flow pattern within a vertical flow reactor. On the basis of such modeling, modifications in the geometry of the reactor could be proposed aiming at reducing zones of low dose and therefore improving disinfection performances. Side-by-side experimental comparisons between modified and unmodified pilots enabled us to validate that approach.
Electrochemical treatment of copper cyanide wastewaters using stainless steel electrodes
Authors: Szpyrkowicz L. , Zilio-Grandi F. , Kaul S.N. , Rigoni-Stern S.
Published: May 2018

A study was carried out to define the best conditions for the simultaneous electroxidation of cyanides and recovery of copper as a metallic deposition on the cathode from weak concentration rinse wastewaters, using plate stainless steel electrodes. A direct electroxidation process and an indirect electroxidation in a chloriderich medium were tested at pH from 10 to 13. The results show that the process of the direct electroxidation is feasible and economically convenient if conducted at pH 13. It was possible to reduce copper concentration from 470 mg−1 by 79% in 1.5 h, at an energy consumption of 17 kWh kg−1 and to recover 335.3 mg of Cu as pure metal, electrodeposited on the cathode. The CuO film formed simultaneously on the anode had catalytic properties for CN− electroidation. The efficiency of the destruction of cyanides was in the same order of magnitude, with kinetics being of first order with respect to cyanide concentration (first order reaction rate k = 0.007 min−1).