bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling the spatial distribution and dynamics of a xylene-degrading microbial population in a membrane-bound biofilm
Authors: Wanner O. , Debus O. , Reichert P.
Published: May 2018

In a stirred laboratory reactor a biofilm was grown on a gas-permeable silicone membrane, Xylene was added to the bulk fluid as the only carbon source and oxygen was supplied through the membrane. For 66 days the reactor was operated under varying experimental conditions. The concentrations of five components in the reactor effluent and of two in the gas outlet were measured almost daily, the biofilm thickness was determined several times. The measured time series were used to calibrate a mathematical model which calculates pH, aerobic degradation of xylene, and microbial growth, decay and conversion to inert particulate material. The calibrated model was then used to analyze the spatial distribution and dynamics of the xylene-degrading heterotrophic population in the biofilm. The analysis revealed that as long as oxygen was supplied as air heterotrophic cells only grew within a thin zone of about two hundred micrometers near the membrane. Upon the change from air to pure oxygen this zone shifted instantaneously by half of the biofilm thickness of about two millimeters towards the biofilm surface. The immediate ability of the biofilm to convert xylene in a zone which so far had been strictly anaerobic, indicates the presence of a heterotrophic population in this zone. The conclusion is that this population had been transported from the aerobic to the anaerobic zone and that transport and growth of microbial cells are processes which are equally important in biofilms.
Adhesion strength of biofilm developed in an attached-growth reactor
Authors: Ohashi A. , Harada H.
Published: May 2018

In this study a novel methodology is proposed to estimate the adhesion strength of biofilm developed in an attached-growth reactor. The time variation of adhesion strength was quantified in the course of formation of a biofilm consisting of denitrifiers. The model biofilm was formed on the surfaces of polyvinyl-chloride plates placed in a rectangular open-channel reactor. The result indicates that the adhesion strength was not uniformly distributed throughout biofilm, but had a tendency to increase with biofilm depth and with the progression of biofilm formation. For example on the 32nd day from start-up the adhesion strength near the substratum interface attained a level in the order of 102 dyne·cm−2, whereas that in the vicinity of biofilm outer surface was only in the order of 100 dyne·cm−2. As well the biofilm dry density did not remain constant throughout biofilm, having a tendency similar to that of the adhesion strength. A strong correlation was observed between the dry density and the extracellular biopolymer content per unit biofilm volume. It was suggested that the adhesion strength was significantly affected by the dry density.
Activated carbon based biological fluidized beds for contaminated water and wastewater treatment: a state-of-the-art review
Authors: Sutton P. M. , Mishra P. N.
Published: May 2018

The ability of the biological fluidized bed (BFB) process configuration to intensify biological reaction rates through accumulation of high concentrations of active biomass has brought attention to the technology for the past twenty years. Over 80 commercial, media based BFB reactors have been installed in North America and Europe. Currently there is much interest in systems in which granular activated carbon (GAC) is used as the fluidizing media for treatment of contaminated waters and wastewaters. This paper provides a historical review of the development of the technology together with information on design and commercial application of the technology in North America.
Advances in biofilm aerobic reactors ensuring effective biofilm activity control
Authors: Lazarova V. , Manem J.
Published: May 2018

Increasing volumes of wastewaters combined with limited space availability and progressively tightening standards and quality control, promote the development of new intensive biotechnologies for water treatment. Fixed biomass processes offer several advantages compared with conventional biological treatments, respectively, higher volumetric load, increased process stability and compactness of the reactors. The purpose of this paper is to present an overview of the principal characteristics of advanced aerobic biofilm processes (performance, reactor configurations, scale-up, energy consumption, field of application, etc.), completed by a synthesis of their advantages and disadvantages. Emphasis is placed on the factors and techniques ensuring effective control of biofilm thickness and better mass transfer.

For better understanding of biofilm processes, a new bioreactor classification is proposed as a function of the state of the biomass, the state of the medium and the hydrodynamic conditions. The control of the biofilm thickness is recognized as one of the most important parameters influencing process performance and efficiency. It is concluded that three-phase bioreactors ensure enhanced biological reaction rates through an effective biofilm control. However, further studies are needed to develop new economically attractive full scale mobile bed bioreactors.
Kinetics of toluene degradation in a biofilm system under denitrifying conditions
Authors: Arcangeli J. P. , Arvin E.
Published: May 2018

In this paper a variability study of the kinetics of toluene biodegradation in biofilm systems under nitrate reducing conditions is presented. A total of 10 kinetic experiments were performed: 4 with toluene as a single compound and 6 with toluene in the presence of a mixture of aromatic compounds (benzene, ethylbenzene and xylenes: BEX). When toluene was the only substrate the maximum utilization rate, kx, and the half saturation constant, Ks, ranged between 1.3 to 1.8 d−1, and 0.17 and 1.7 mg/L respectively. Based on the nitrite production, the average yield coefficient was 1.0 to 1.2 mg biomass/mg toluene degraded. Furthermore, it was shown that the presence of benzene, xylenes and ethylbenzene significantly decreased the toluene removal.
Validation of a multisubstrate mathematical model for the simulation of the denitrification process in fluidized bed biofilm reactors
Authors: Eramo B. , Gavasci R. , Misiti A. , Viotti P.
Published: May 2018

The present paper compares the experimental results obtained from a research programme developed on a pilot-scale fluidized bed biofilm reactor and the outputs of a numeric simulation model; the mathematical model can determine the substrate concentration profile within the reactor.

The experimental campaign investigated heterotrophic biological denitrification in anoxic conditions. The model is based on multi-substrate Michaelis-Menten kinetics and considers mass transport resistancephenomena within and outside bioparticles.

A monodimensional model of the reactor taking into consideration, in steady-state condition, phenomena due to convective transport and turbulent diffusion has been used.

The fluidization model applied to describe the behaviour of the biofilm-covered rigid particle bed is based on the Wen and Yu correlation.
Biofilms growing on gas permeable membranes
Authors: Rothemund C. , Camper A. , Wilderer P. A.
Published: May 2018

In a Membrane Biofilm Reactor (MBR) gas permeable membranes are used as a substratum for bacteria to grow in. The membrane separates an oxygen containing gas space from a compartment through which wastewater is pumped. Biofilms attached to the membrane are supported with oxygen from the adhesion site, and with substrates from the bulk liquid.

The MBR is a promising tool for the aerobic treatment of industrial wastewaters. Volatile organics are kept from getting stripped into the atmosphere. Bacteria with special metabolic properties can be immobilized and exploited under controlled process conditions. By using porous membranes the bacteria are allowed to colonize not only the membrane surface but also its pores. By that, a starter culture is maintained and used as an inoculum in case biofilm gets lost through erosion, abrasion, grazing or sloughing.

Experiments have been conducted to study structure and functions of membrane bound biofilms. Visualisation of biofilms by scanning and transmission electron microscopy revealed that the pores of the membranes get densely colonized. In situ identification of microorganisms by genetic probes in cross sections of a biofilm could successfully be carried out. Oxygen concentration profiles measured by means of microelectrodes demonstrated the efficiency of the oxygen partial pressure as a parameter to control oxygen supply of membrane bound biofilms.
Results and experience with the NEBIO tube reactor process in the water treatment plant coswig near Dresden
Authors: Boehler E. , Haldenwang L. , Schwabe G.
Published: May 2018

Research work in the field of heterotrophic denitrification was done in Dresden between 1976 and 1980; in 1985 it was resumed with new objectives. A fluidized-bed reactor with a floatable granular carrier material was developed and represents a novel solution. The process could be essentially improved by making use of the NEBIO tube reactor, where the fluidized bed is produced by downward flow of the water to be treated. The circulation of a partial stream is not required. In February 1989 a pilot plant with a capacity of 650 m3/d was taken into operation. Due to the good results, further work has been sponsored by the Bundesministerium für Forschung und Technologie from the middle of 1990. Planning work for a demonstration plant was carried out in 1991. In August 1992 two reactors with a water throughput of 6,100 m3/d were already started, and the aftertreatment unit with aeration, multi-layer and activated-carbon filter, pH adaptation by gas exchange and a two-stage disinfection with chlorine was taken into operation. In November 1992 for the first time water was fed into the supply system. The NEBIO tube reactor process proved to be a reliable and safe process for the biological elimination of nitrate. Continued research work will focus on the development of models for the degradation processes in the tube reactor and the optimisation of the overall technology.
Biotransformation of aromatic hydrocarbons in subsurface biofilms
Authors: Zhang W. , Bouwer E. , Wilson L. , Durant N.
Published: May 2018

Bioremediation is an emerging in situ treatment technology for soil and groundwater cleanup. Research in the past decade has made significant progress toward understanding how to stimulate microbial growth in the subsurface by optimizing the physical/chemical conditions. Recent laboratory observations and field demonstrations indicate that bioremediation can also be limited by mass transfer processes. In this paper, factors restricting microbial growth are reviewed, and the importance of bioavailability on the performance of in situ bioremediation is discussed by using aromatic hydrocarbons as model contaminants. Successful application of bioremediation relies upon an understanding of interactions among microorganisms, organic contaminants and soil/aquifer materials. Applications of biofilm kinetics toward this goal are addressed. Model simulations and laboratory studies suggest that both low temperature and slow desorption rate could greatly lengthen the time required for effective in situ bioremediation of aromatic hydrocarbons.
Integrated approaches for achieving sustainable development of urban storm drainage
Authors: Ellis J. B.
Published: May 2018

Principles and guidelines are outlined for the development and implementation of integrated design approaches to achieve sustainable levels of environmental enhancement in urban floodways and corridors. In-channel bioengineering combined with out-of-channel landscaping offers a range of opportunities for conservation, recreation and amenity as well as providing basic flood and pollution control. In addition, integrated local-scale restoration and remediation is compatible with holistic concepts of wider catchment management as well as supporting local community objectives of land enhancement. Approaches to watercourse design are described and key functional relationships identified for the achievement of integrated landscape design.
Accelerating the rate of cometabolic degradations requiring an intracellular electron source-model and biofilm application
Authors: Bae W. , Rittmann B. E.
Published: May 2018

This paper applies our recently acquired knowledge of the large and systematic changes in internal reducing power to controlled changes in the cell's primary electron-donor and -acceptor substrates. The systematic cellular responses of the NADH/NAD ratio is incorporated into kinetic equations for reductive dehalogenation and oxygenation reactions. Results show that the external donor and acceptor concentrations strongly affect the percentage removal of hazardous compounds. The simplest strategy for maximizing the efficiency of reductive dehalogenation is to maintain a saturating concentration of the primary electron donor, or, as a next best alternative, to minimize the concentration of electron acceptors. For mono- or dioxygenation reactions, consistently high percentage removals can be achieved when the concentrations of both primary substrates are high.

Removals of carbon tetrachloride in denitrifying biofilm experiments are in perfect accord with the model predictions for reductive dehalogenation. They show a dramatic increase in percentage removal when the primary electron acceptor (NO3−) is removed from the reactor and a substantial decrease when the electron donor (acetate) is removed. Thus, the biofilm experiments verify that biodegradation reactions can be accelerated dramatically by manipulation of primary donor and acceptor concentrations and in a manner consistent with modeling predictions based on the internal reducing power.
Water diffusion device design in reservoir structures
Authors: Dakhlaoui Mohamed , Gaujous Didier , Raimbault Georges , Tabuchi Jean-Pierre
Published: May 2018

In order to reduce urban runoff flowrates, reservoir structures are now used. Such use often implies the injection of rainwater coming from nearby buildings or catchments through these structures. This injection requires some diffusion devices to secure the homogeneous filling of the structure. This paper presents some useful instructions for the design of such devices. It provides information about diffused flowrates through a drain element according to the inside piezometric water head. It also deals with the hydraulic behaviour of a drain supplied with water from one end. A numerical model simulates this hydraulic behaviour. Lastly, a chart is provided in order to help water diffusion device designers.
On-site stormwater detention: improved implementation techniques for runoff quantity and quality management in Sydney
Authors: Nicholas Douglas I.
Published: May 2018

On-site stormwater detention has become well established in Sydney and several thousand systems are now in place. Mistakes have been made because education and training, design and installation skills and supporting technology have not kept pace with the concepts. Much has been learned from the problems, however, and the development industry has now come to accept that new ways of dealing with stormwater runoff are here to stay. The result is that techniques are emerging which will make future OSD systems more effective, easier to maintain, less obtrusive, more attractive to owners and occupiers and less expensive. The paper describes some of the systems which are being used to improve discharge control, storage efficiency, harmonious site integration and effluent quality while, at the same time, reducing cost.
Fluidized-bed biofilms for chlorophenol mineralization
Authors: Puhakka Jaakko A. , Melin Esa S. , Järvinen Kimmo T. , Koro Päivi M. , Rintala Jukka A. , Hartikainen Päivi , Shieh Wen K. , Ferguson John F.
Published: May 2018

This paper summarizes a five-year research effort on the development of a high-rate fluidized-bed biofilm system for remediation of chlorophenol contaminated groundwater. Laboratory-scale experiments with model compounds and actual contaminated groundwater included studies on aerobic and anoxic treatment, strategies for selective enrichment of chlorophenol degrading microorganisms, kinetics and stoichiometries of chlorophenol conversions, toxicity removal, growth and culture characterization, recovery from process upsets, and operation at suboptimal temperatures. The aerobic process using chlorophenols as the sole source of carbon and energy showed the greatest versatility and efficiency. The contaminated groundwater consisted of 2,3,4,6-tetrachlorophenol, 2,4,6-trichlorophenol and pentachlorophenol with total chlorophenol concentrations ranging from 45 to 55 mg/l. At room temperature, groundwater remediation resulted in over 99.9% mineralization at chlorophenol loading rates of 1000 mg/l/d and hydraulic retention times of less than 1h. At the groundwater temperature (7°C), similar removal efficiencies were obtained at chlorophenol loading rates of up to 740 mg/l/d. The laboratory results were successfully repeated in an on-site, pilot-scale demonstration.
Development and application of bacterial cultures for the removal of chlorinated aliphatics
Authors: Janssen Dick B. , de Koning Wim
Published: May 2018

The possibility of obtaining microbial cultures for the degradation of halogenated aliphatic hydrocarbons is mainly determined by the diversity and activity of catabolic enzymes that exist in nature. If a suitable organism is available, applications for the treatment of different waste streams can be developed. The relation between the kinetic parameters of the key enzymes and the properties of the organisms relevant for such applications is discussed, both for growth supporting and cometabolic degradation. When growth on a chlorinated aliphatic compound is possible, development of a biological remediation process is likely to be relatively easy. This is illustrated with the degradation of 1,2-dichloroethane, a synthetic compound that can be mineralized by specific cultures. Closely related compounds may be recalcitrant, which can be understood from an examination of the degradative pathways. The development of biological treatment processes based on cometabolic degradation is more demanding because selection of the proper organisms and maintaining them in the process are not straightforward. The range of compounds that can be degraded cometabolically is significantly larger. The potential of obtaining improved degradation by genetic adaptation and the use of biofilms is discussed.
Application of remote sensing technology to the relation of submarine pipelines and coastal morphology
Authors: Yüksel Y. , Maktav D. , Kapdasli S.
Published: May 2018

Submarine pipelines must be designed to resist wave and current induced hydrodynamic forces especially in and near the surf zone. They are buried as protection against forces in the surf zone, however this procedure is not always feasible particularly on a movable sea bed. For this reason the characteristics of the sediment transport on the construction site of beaches should be investigated. In this investigation, the application of the remote sensing method is introduced in order to determine and observe the coastal morphology, so that submarine pipelines may be protected against undesirable seabed movement.
Optimal design of in-sensor-experiments for on-line modelling of nitrogen removal processes
Authors: Vanrolleghem P. , Coen F.
Published: May 2018

In-Sensor-Experiments are proposed as a means of providing highly informative data concerning the bioprocesses occurring in N-removal systems. It is highlighted that the changing nature of both wastewater and activated sludge enforces the continuous adjustment of the proposed In-Sensor-Experiments to maintain the quality of the sensor's outputs. Central to the automated design of the experiments performed in these adaptive sensors is a mathematical representation of the processes occurring in the device. This model is continuously updated on the basis of previously acquired data. It is illustrated how different design criteria (objective functions), such as most reliable model selection capability or minimal parameter variance, influence the experimental designs. The concepts are illustrated with real-life data from two types of In-Sensor-Experiments. First, short-term (fed-)batch respirometric experiments are used to estimate the biokinetics of the nitrifying population. Second, a new device is presented in which a sensing element is placed at the end of a plug-flow reactor, hence the term “Plug-Flow-Sensor”. The optimally designed and continuously updated variation of the flow rate through the plug flow reactor results in a retention time distribution. This allows us to monitor a variable as function of the reaction time and this within a narrow (user-specified) window of reaction times, increasing the measuring frequency and accuracy compared to equivalent batch experiments. As a first example, ORP is applied as measured variable. By using ORP “nitrate knees” can be detected after a certain reaction time. This information is an indicator of the denitrifying capacity of the sludge.
Observability of reduced order models - application to a model for control of alpha process
Authors: Ayesa E. , Oyarbide G. , Larrea L. , Garciía-Heras J. L.
Published: May 2018

This paper describes the theoretical basis and some applications of a identifiability/observability test for state-space models based on the recursive calculation of the numerical condition of the observability matrix. This test evaluates the possibility of estimating the unknown states and parameters of a mathematical model under defined experimental conditions and available information. The numerical value of the proposed “observability parameter” is also an index of uncertainty propagation through the model. As examples of the utility of the proposed test, the paper presents the analysis of a reduced-order model for two wastewater treatment plant configurations (D-N and Alpha process), evaluating the on-line information that is theoretically indispensable in distinguishing each one of the unknown states and parameters under steady or dynamic conditions.
Selection of one-dimensional sedimentation: models for on-line use
Authors: Grijspeerdt Koen , Vanrolleghem Peter , Verstraete Willy
Published: May 2018

A comparative study of several recently proposed one-dimensional sedimentation models has been made. This has been achieved by fitting these models to steady-state and dynamic concentration profiles obtained in a down-scaled secondary decanter. The models were evaluated with several a posteriori model selection criteria. Since the purpose of the modelling task is to do on-line simulations, the calculation time was used as one of the selection criteria. Finally, the practical identifiability of the models for the available data sets was also investigated. It could be concluded that the model of Takács et al. (1991) gave the most reliable results.
Denitrification in secondary clarifiers
Authors: Siegrist H. , Krebs P. , Bühler R. , Purtschert I. , Röck C. , Rufer R.
Published: May 2018

Denitrification in secondary clarifiers is primarily due to hydrolysis of particulate degradable COD and decay of biomass. The reduction factor of these processes under anoxic as compared to aerobic conditions was investigated in the treatment plants of the City of Zurich. The Zürich-Glatt plant has circular clarifiers with central inlet. The treatment plant Zürich-Werdhölzli has rectangular clarifiers with cross flow and scrapers with vacuum removal of the sludge. At Zürich Glatt denitrification capacity in the clarifiers was 30% of total denitrification, whereas at Zürich-Werdhölzli only 15 % was observed. The sludge mass in the secondary clarifier depends on inlet flow, return sludge flow, activated sludge concentration, sedimentation properties of the sludge and scraper intervals. During dry weather and due to good sedimentation properties the activated sludge blanket in the thickening zone of the rectangular clarifiers at Zürich-Werdhölzli is almost completely removed after passage of the scraper. Denitrification volume in the secondary clarifier can therefore be modelled in relation to the ratio of inlet to return sludge flow and scraper interval. With the aid of control of return sludge flow and scraper intervals denitrification capacity in the secondary clarifiers may be improved. In order to control denitrification in the secondary clarifier the model must include a variable sludge volume in the clarifier related to scraper interval under the assumption of constant sludge mass in the entire system.
Evaluation and design of full-scale wastewater treatment plants using biological process models
Authors: Daigger Glen T. , Nolasco Daniel
Published: May 2018

Results from application of the IAWQ Activated Sludge Model No. 1, either with or without the excess biological phosphorus removal model of Dold, to thirteen full-scale wastewater treatment plants are presented. For nitrogen removal applications the model is capable of accurately predicting full-scale plant performance and trends in performance, even using model default parameters. Additional work is needed to allow accurate predictions of the effect of reactor configuration and oxygen transfer systems on plant performance. The model of Dold accurately characterized the steady-state performance of biological nitrogen and phosphorus removal systems, but not their dynamic behavior. Detailed wastewater characterization is necessary to allow accurate prediction of the steady-state performance of biological phosphorus removal systems. Further work is necessary to demonstrate its applicability to dynamic applications.
The implementation of biokinetics and conservation principles in ASIM
Authors: Gujer Willi , Larsen Tove A.
Published: May 2018

The Activated Sludge SIMulation program ASIM is introduced as a didactic tool to be used in design courses for the simulation of the dynamic behaviour of modern nutrient removal activated sludge systems. It allows for free definition of the biokinetic model, the flow scheme, process control strategies and load variation. Its user interface is simple enough to be used in the classroom but powerful enough to support even professional work.

The most difficult aspect of ASIM is the preparation of the biokinetic model (transformation processes) to be used. A systematic use of stoichiometric conservation principles simplifies this task and at the same time reduces the number of empirical parameters. The practical application of conservation principles for charge, elements and theoretical COD is presented in detail. Composition equations are introduced as a link to the wastewater treatment plant reality.
Constructed wetlands in water pollution control: fundamentals to their understanding
Authors: Wood Andrew
Published: May 2018

Constructed wetland systems for the treatment of wastewaters, pollution control and environmental enhancement have been gaining increasing international interest and application. This interest has was stimulated by the 1986 Piracicaba Conference at which the IAWPRC Specialist Group was motivated, followed by specialist conferences in Chattanooga 1988, Cambridge 1990, Sydney 1992, and subsequently the present conference in Guangzhou 1994. During this time it is estimated that over 1000 wetland systems have been implemented as well as many research projects throughout the world into the mechanisms and performance optimization of such systems for a wide variety of applications and objectives. This paper provides a brief review of some of the existing understanding of the technology, identifying recent design philosophies, performance expectations and some limitations to present understanding and confident design basis.
Integrated constructed wetland for small communities
Authors: Urbanc-Bercic Olga , Bulc Tjaša
Published: May 2018

Constructed wetlands proved to be an effective and low-cost technology to control environmental pollution. The introduction of such low-tech systems is supported by the Slovenian Government. The aim of our research project was to intensify the reduction of nutrients (nitrogen compounds mainly) prior to discharging the effluents into the rivers, a contribution to the common target of the global environmental policy. The construction of the integrated system was completed in Autumn 1993 to treat domestic sewage for 10 PE. The system consists of three interconnected beds with vertical and horizontal flows. The vertical flow at the first stage is intermittent, while the horizontal one is continuous. The system is flexible due to mode of operation and the quality of the influent. Ten analyses were made during the initial months of operation. In bed B nitrification was taking place and the reduction of all other parameters but NO3-N was documented. In bed A denitrification was on in spite of intermittent vertical flow. Since the reed stand was scarce, recultivation was needed. The system showed its characteristics more clearly when more concentrated domestic wastewater was led in. Further investigation should reveal further details on proper media, surface area, and flow sequence selection. Reduction of some parameters was as follows: NH3-N 97.5%, NO3-N 74.5%, org-N 84.8%, P-tot 97.1% and COD 94.4%.
The use of extended aeration and in-series surface-flow wetlands for landfill leachate treatment
Authors: Martin Craig D. , Johnson Keith D.
Published: May 2018

Recently in the USA, the Solid Waste Industry has undergone specific changes in landfill regulations. The Federal Resource Conservation and Recovery Acts (RCRA); and EPA subtitle D regulations, as well as stringent State regulations, impose minimum criteria for municipal solid waste facilities in the areas of location, operation, groundwater monitoring, and leachate management. In conjunction with these State and Federal mandates the University of West Florida developed a leachate treatment technique utilizing extended aeration and surface-flow constructed wetlands. Sampling of water quality has occurred monthly since February 1992. Parameters examined include: Nitrogen (NH3,), Total Suspended Solids (TSS), Total Phosphate (TPO4), Total Organic Carbon (TOC), pH, Alkalinity, and Chlorides. Chemical Oxygen Demand (COD), Total and Fecal Coliforms, Priority Pollutant Metals, and limited organic analytes are sampled on a less frequent basis. Samples are collected at a raw leachate site (L0), primary aerated lagoon (L1), and 6 stations within the 1.1 hectare constructed wetland complex (S1; W1; W3; W5; W7; W9) and one sandfilter (SF) location. Results thus far indicate removal percentages of the tested analytes average between 64% and 99%. This data suggests various physical, microbiological and chemical processes occurring within the aerated lagoon and constructed wetlands can provide an effective alternative to standard techniques for landfill leachate treatment and disposal. The methods as described have proven to be ideal for the circumstances occurring at the Perdido Landfill.
Ammonium and nitrate removal in vegetated and unvegetated gravel bed microcosm wetlands
Authors: Tong Zhu , Sikora F. J.
Published: May 2018

A greenhouse experiment was conducted at Tennessee Valley Authority, Alabama, USA, in the summer of 1993 to investigate ammonium and nitrate removal processes in constructed wetlands. Microcosm wetlands cells were used in the study and consisted of plastic containers with 0.4 × 0.35 m2 surface area and 0.5 m depth. Two separate experiments were conducted. One experiment analyzed NH4-N removal and the other analyzed NO3-N removal. Nutrient solutions containing approximately 48 mg/l NH4-N or NO3-N were added in a batch mode to the wetland microcosms and the solution chemistry was analyzed with time. Treatments consisted of unplanted cells or cells planted with canarygrass (Phalaris arundinacea), reed (Phragmites communis), bulrush (Scirpus atrovirens georgianus) or typha (Typha latifolia). Another treatment consisted of added nutrient solutions containing or not containing C at 112 mg/l. In the NH4-N removal experiment, the rate of NH4-N removal occurred in the order: reed > canarygrass = bulrush > typha ≫ unplanted in wetland cells with and without C. The order of NH4-N removal was believed to be associated with the density of root biomass in the gravel. The greater the root biomass, the greater the chance for plant N uptake or nitrification mediated by O2 transport to the rhizosphere. In the NO3-N experiment, the rate of NO3-N removal occurred in the order: reed = canarygrass > typha = bulrush > unplanted cells. Labelled K15NO3 was used to trace the NO3-N removal process. By measuring the 15N in the plant biomass, the quantity of NO3-N removed via plant uptake was delineated from combined removal processes of denitrification and immobilization. In the treatments with C, 55 to 70% of the NO3-N was removed via denitrification and immobilzation. For bulrush, reed and typha, the quantity of NO3-N removed via denitrification and immobilization without added C was reduced to 14 to 30%. However, NO3-N removal via denitrification and immobilization remained high at 72% of added NO3-N in canarygrass cells due to high concentrations of organic C released from the canarygrass roots (15-20 mg/l C) that apparently did not limit denitrification or immobilization.
The use of wetlands for water pollution control in Australia: an ecological perspective
Authors: Mitchell D. S. , Chick A. J. , Raisin G. W.
Published: May 2018

The potential use of natural and constructed wetlands to treat rural and urban wastewaters and run-off has been under active investigation in Australia by the authors and others associated with them for about 15 years. The results of these investigations will be briefly summarised in relation to factors affecting their performance and their application for management of water pollution.

Investigations have included rigorous experimentation with wetland microcosms, calculation of nutrient balances for natural and artificial wetlands, fundamental research on the role of wetland plants, the construction of experimental wetlands of various designs at a pilot scale, and the installation of operating systems.

The results confirm the potential of wetland systems to ameliorate water quality but do not demonstrate how to do this consistently under normal day-to-day operating conditions. Issues that now need to be addressed include hydraulic short-circuiting, the role and management of the wetland plants, the extent to which constructed systems should mimic natural systems, and problems associated with scaling up from successful experimental systems to full scale operating treatment plants.
Nutrient-related selection mechanisms in marine phytoplankton communities and the impact of eutrophication on the planktonic food web
Authors: Riegman R.
Published: May 2018

A general increase in nutrient discharges during the last few decades has caused various changes in the algal community structure along the European continental coast. Coincidentally and maybe consequently, the foodweb structure and functioning has altered in local areas causing various phenomena like oxygen depletion, mortality of groups of organisms, foam on beaches, and an increase in the productivity of benthic communities and some commercial fish species. The observed increases in algal biomass and shifts in species composition are discussed in relation to the involved key mechanisms: resource competition and selective grazing.

Along the Dutch coastal zone of the North Sea eutrophication has caused a doubling of the yearly averaged algal biomass during the past three decades. The sudden appearance of Phaeocystis summer blooms coincided with a shift from P-limitation towards N-limitation in the Dutch coastal area due to a stronger increase in P-discharge relative to the increase in N-discharge. Competition experiments in continuous cultures showed Phaeocystis to become dominant under N-limitation. Additionally, the large Phaeocystis colonies, which can reach a diameter up to one centimetre, escape from microzooplankton grazing.

A computer model is presented which demonstrates a shift from bottom-up towards top-down control if the pelagic environment becomes eutrophicated. Implementation of this concept in a size-differential phytoplankton control model generates the prediction that algal blooms are dominated by species that escape from grazing by those zooplankton species which have a high potential numerical response. In marine environments these are microzooplankton species. These organisms mainly feed on cyanobacteria, prochlorophytes and some nano-algal species. One of the consequences for foodweb structure and the carbon fluxes in marine foodwebs is that eutrophication will lead to the dominance of poorly edible algal species.

Eutrophication favours the downward transport of carbon and nutrients towards the sediments not only due to higher algal biomasses but also as a consequence of a shift towards larger algal species with higher sedimentation characteristics.

An example is given how these new insights can be used for water quality management purposes.
Influence of benthic diatoms on the nutrient release from sediments of shallow lakes recovering from eutrophication
Authors: Van Luijn F. , Van der Molen D. T. , Luttmer W. J. , Boers P. C. M.
Published: May 2018

Measures taken to combat eutrophication resulted in a decrease in phytoplankton chlorophyll and an increase in transparency in the lakes studied. Because of the low nutrient concentrations in the overlying water, the increased light availability and the relatively nutrient rich sediments, a benthic algae community developed. In this study the interactions between the benthic algae and the nutrient release from the sediments is examined. In laboratory experiments it is demonstrated that benthic diatoms are able to grow on nutrients released from the sediments. The direct result is a decrease of the nutrient flux from the sediments by uptake by benthic diatoms. An indirect effect is an increased loss of nitrogen from the sediment water system to the atmosphere by stimulation of the coupled nitrification-denitrification. This is caused by an increased O2 penetration depth due to the photosynthesis of benthic diatoms. Based upon these laboratory results and additional calculations, it is concluded that the benthic diatoms in the field are able to reduce the nutrient release from the sediments and thus the availability for the phytoplankton. The benthic diatoms therefore may accelerate the process of recovery from eutrophication.
Transition of a lake to turbid state six years after biomanipulation: mechanisms and pathways
Authors: van Donk E. , Gulati R. D.
Published: May 2018

Six years after application of biomanipulation in 1987, Lake Zwemlust (The Netherlands) returned during the summer from a clear water state dominated by aquatic vegetation to a turbid state characterized by high algal biomass. Herbivory and growth of epiphytes on macrophytes were the main factors triggering the switch. Selective herbivory by coots (Fulica atra) and rudd (Scardinius erythrophthalmus) caused a change in macrophyte species composition from a dominance of Elodea nuttallii in 1988/1989 to Ceratophyllum demersum in 1990/1991, and finally to Potamogeton berchtholdii in 1992/1993/1994. Observations revealed a general lack of epiphytes associated with Elodea and Ceratophyllum, while Potamogeton showed a progressive coverage with epiphytes, causing Potamogeton to decline markedly during late summer. Phytoplankton blooms, dominated by cyanobacteria, appeared again during three consecutive autumns, 1992, 1993 and 1994, with chlorophyll-α concentrations reaching 60-240 μg 1−1.
The impact of runoff and sediment transport from the Provadiyska and Devnenska rivers on the Beloslav lake
Authors: Mihailov Grigor , Daskalov Kristio , Lissev Nikolay
Published: May 2018

The most essential results of processing and analyses of regular and field study data for the hydrophysical and hydrochemical characteristics of the Provadiyska river, the “Padina” canal flowing into it, the Devnenska river, the settling basin and the western part of the Beloslav lake, carried out by a group of scientists from UACEG at the end of 1994 are presented. Based on the available data from the National Institute of Meteorology and Hydrology, the general hydrological characteristics of the Provadiyska and Devnenska rivers are determined. The ratio between natural sediments and industrial/chemical ones entering into the settling basin and Canal 2 is estimated. Physical and chemical parameters as well as the quantities of the bottom sediments in the settling basin and in the Beloslav lake are determined.
The pollution of the Black Sea from livestock and steps towards its limitation
Authors: Marinova Svetla M.
Published: May 2018

New aspect of the recreation policy is the renovation of the environment via limiting the pollution of the water and the seaside around the territory of the Black Sea. The development of new methods for limiting pollution from the livestock and swine breeding farms near the seaside is shown. The limits for the concentrations of the pollutants and the kinds of polluter are given, so that they do not disturb the ecological balance.
The ecological situation in the Russian part of the Black Sea-isotopic-geochemical monitoring in a shore-sea system
Authors: Kochetkov Michael V. , Zairy Namik M. , Polkanov Michael P. , Vilenkin Vladimir A.
Published: May 2018

Methodological aspects and main results of the 1st stage (1993) of isotopic-geochemical monitoring in the Russian part of the Black Sea are considered. Interpretation of data has shown that carbon- and sulphur-containing products of technogenesis have different sources: in the first case great sea ports and terminals with oil products can be clearly identified; in the second – mainly surface run-off from agricultural areas and watersheds of big rivers. Metal compounds originated due to destruction of ore mineralization zones are clearly separated from the products of human activity. The main mass of contaminants is transported along seashore and turns to the deep part of the sea in the region of Tuzla cape where are evidently the main geochemical barriers and accordingly sedimentation of contaminants. High concentrations of metals of 1 and 2 groups by toxicity found in geochemical anomalies do not indicate their technogenic origin. The only criteria of their ranging in this case are isotopic data on C and S being combined with traditional geochemical analysis.
Wind-induced circulations of the black sea
Authors: Kiran Nilgün , Yenigün Orhan , Albek Erdem , Börekçi Osman
Published: May 2018

A two-dimensional single layer hydrodynamic model of the Black Sea is constructed in which currents are driven by the forcing effect of the wind. An explicit finite difference scheme was used where the equations were discretized over a 128 × 79 non-staggered grid. To represent the seasonal wind patterns the sea is divided into 14 sectors and for each season the dominating wind in each sector was selected. The model incorporating the sectoral wind patterns was applied to all of the four seasons. The results successfully simulate some of the well known circulation patterns in the sea.
Wastewater treatment in a company with advanced demands for water quality
Authors: Heinrich D.
Published: May 2018

The result of the North Sea Conference 1987 in London was the 50% reduction of dangerous and nutritive substances before 1995. To reach that aim the wastewater treatment plants discharging to the river Elbe were subjected to more severe discharge standards. In our case the company could also use the publicly owned treatment plant of Hamburg and so we were in direct competition with that plant. After several conferences with the client and the water authority we began the planning. The treatment plant also includes removal of nitrogen in the last stage and phosphorus in the biological stage (not only with chemicals). Another difficulty was that only a small area between the dam of the Elbe with a street alongside and the offices was available. So we had to plan a very compact treatment plant. To avoid the emission of odours the plant was completely housed. As in other factories we also had the problem that on weekends and during the holidays very little water is flowing to the plant. The sewage system collected the wastewater in one system and stormwater in another. Since the area is flat, several pumpstations transport the water. So we planned a modular system with sieve screen and three SBR reactors to use it further as cascaded activated sludge tanks with predenitrification and enhanced biological phosphorus removal. The sludge treatment was realized as an aerobic thermophilic process in a separate tank. To improve matters we also installed a computer for process control. The influent concentrations are higher than municipal wastewater which is conditioned by the separate system of transportation without infiltration water. For example COD influent concentrations are about 1500 mg/l, NH4-N about 130 mg/l and total phosphorus Ptot about 17 mg/l. The results we obtained in the plant are presented in this paper.
TSS/BOD removal efficiency and cost comparison of chemical and biological wastewater treatment
Authors: Nenov Valentin
Published: May 2018

Based on standard settling column tests, Jar tests and continuous activated sludge laboratory experiments as well as combination of these processes implemented for a treatment of municipal wastewater with a composition typical for the influent water of Ravda Municipal Wastewater Treatment (MWWT) plant, the removal efficiency obtained in respect of the total suspended solids (TSS) and the biochemical oxygen demand (BOD) was evaluated.

The laboratory experiments confirmed the high efficiency of the chemically enhanced mechanical treatment (CEMT) towards TSS and BOD/COD removal. The data obtained show that low dose chemical treatment in a large range of surface flow rate of precipitation provides a reduction of TSS and BOD/COD larger than 60% and 50%, respectively.

Regarding Ravda WWTP as a typical case for the Black Sea coast it was proved that CEMT is an attractive alternative for retrofitting the existing plants based on the activated sludge process as a secondary treatment process. CEMT upgrading can be done at much lower cost (practically only O&M treatment expenditure is required) compared with an eventual biological step extension.
Substrate removal in long sewer lines
Authors: Özer Adem , Kasirga Ersin
Published: May 2018

Wastewaters generated from large dwelling areas are collected and disposed of by means of long sewer trunk lines. The wastewater treatment potential of sewers is not a novel phenomenon, however, it has not been thoroughly investigated in the past. In this study, possible treatment efficiencies are estimated in the presence of sufficient oxygen. Suspended and attached growth kinetics are studied to explore the significance of aeration in sewer trunks. Although there are several existing models describing consumption mechanisms of soluble substrates and reaction rates, a new method is investigated in this paper for shortening the parameters used in biological rate equations. Soluble substrate consumptions of suspended growth microorganisms are taken into consideration by means of an experimental approach and they are estimated by using respiration rates. Relationships between respiration rate, substrate utilization rate and biodegradable organic matter concentrations are observed during the experimental program. An empirical relationship which provides the utilization rate in correspondence with diminishing substrate concentrations along a sewer line is developed based upon the experimental results. Expected treatment efficiencies are determined considering utilization rates of attached and suspended growth microorganisms.