bluuebunny/crossref_metadata_2025 huggingface dataset:
An operational survey of a natural lagoon treatment plant combining macrophytes and microphytes basins
Authors: Vandevenne Louis
Published: May 2018

The sewage treatment plant studied, located in a rural area, is designed to treat the wastewater for a population of 650. The station functions in accordance with the principle of natural lagoons via artificial wetlands combining macrophytes and microphytes lagoons arranged in series. The overall surface area including the primary lagoon gives rise to a specific load of 6 m2/inhabitant.

Both the primary and secondary treatments produce a very good water quality in accordance with the conventional parameters (SS, Suspended Solids; BOD5, the Biological Oxygen Demand over a 5 day period; COD, the Chemical Oxygen Demand). The tertiary purification of the nitrogen and phosphorus does not give as good results as expected, respectively 42% and 35% removal; very little better than those of a conventional installation. The tertiary quality standard appears not to be attainable since the successive biological mechanisms carrying out the elimination process are followed by a release of the pollutants and an insufficient elimination (plant exportation) by the macrophytes. The design and management of the macrophytes basins is relatively tricky, particularly with respect to the removal of weeds and the regulation of the water level in the macrophytes basins.
Constructed wetlands in Europe
Authors: Haberl R. , Perfler R. , Mayer H.
Published: May 2018

Many European countries have recently stated an increasing demand for small waste water treatment plants. Constructed wetlands seem to be particularly well suited for on-site treatment due to their simple construction and large buffering capacity.

A number of different designs exist in Europe, above all subsurface flow systems, which have been in use for 20 years. At first, horizontal flow was preferred but the stringent legal rules have led to the development of highly efficient vertical flow in recent years. In order to meet the higher requirements of small and very sensitive recipients, combined systems (i.e. constructed wetlands and conventional biological plants) have proved to be successful. At present, tests are being carried out to study the use of constructed wetlands for other applications as well, such as the treatment of groundwater, industrial waste water and sludge dewatering.

All our present know-how and experience with constructed wetlands should enable us to convince the authorities and to obtain legal permission for the installation of constructed wetlands.
The reality of sewage treatment using wetlands
Authors: Hiley Peter D.
Published: May 2018

Empirical performance data provide a basis for the design of wetlands to specific performance limits. BOD and suspended solids are removed up to 95% from 10-250 mg l−1. Surface flow systems in Yorkshire achieved higher effluent standards but generally lower mass load removal than subsurface flow systems. All wetland systems fill up with solids at a predictable rate, and if they are not removed or degraded, they will overflow. Ammonia is not normally oxidised, except where relatively large land areas are used and/or BOD falls below 20 mg l−1. Phosphate is accumulated until saturation. Bacteria (faecal indicators) are removed, sometimes almost completely, but not reliably. The established theoretical knowledge of sewage treatment processes explains the performance of wetlands. Plants provide a renewable support medium for microbial growth, a matrix to retain solids and assist plug flow hydraulics, but do not appear to provide oxygen. BOD removal is mainly by the aerobic breakdown of organic matter. Bacteria growing on the soil and f-horizon (litter layer) use oxygen from the atmosphere and from nitrate in the sewage. Wetlands are oxygen limited and performance is enhanced if extra aeration is provided.

There were no obvious performance differences between surface and subsurface flow systems, unless extra aeration was involved, though strict comparative data were not found. Vertical flow wetlands appear to be inefficient percolating filters. The simplest designs, construction methods, maintenance and rejuvenation methods should be used. Near design performance of surface flow wetlands is achieved in about 14 days.
Light adaptation of oscillatoria agardhii at different time scales
Authors: van Duin Elisabeth H. S. , Aalderink R. Hans , Lijklema Lambertus
Published: May 2018

The Markermeer is a eutrophic shallow wind exposed lake. In contrast to other eutrophic lakes in the area, persistent blooms of the cyanobacterium Oscillatoria agardhii do not occur. The severe variations in the available light energy, caused by an excessive resuspension of sediment, are held responsible for this absence. Field experiments were conducted in the Markermeer, to investigate the relations between O. agardhii and the specific light climate in the Markermeer, emphasizing the adaptation rate and extent to light energy level variations.

In experiments with traditional light and dark bottles, and bottles moving up and down the water column it was observed that vertical mixing tended to increase the net production of oxygen, as the exposure time near the water surface is too short to cause light inhibition. From experiments with a vertical perspex tube it was concluded that during days with maximum hourly light energy levels above 200 μE·m−2·s−1, the light utilization efficiency was much higher in the morning hours than during the afternoon. This phenomenon did usually not occur at days with lower mean irradiance levels. After prolonged periods of low energy levels (below 50 μe·m−2·s−1), the light utilization efficiency increases significantly but the maximum production level does not increase.
Phytoplankton photoadaptation during the spring period in Lake Zürich
Authors: Schanz Ferdinand , Burri Judith
Published: May 2018

Long- and short-term photoadaptations as a response to increased light availability in spring phytoplankton communities in Lake Zürich have been investigated. At various stages fundamental changes in species composition and species adaptation in a plankton community of approximately constant structure were apparent.
Horizontal distribution patterns during a cyanobacterial bloom
Authors: Pettersson K. , Forsell L. , Hasselrot A. T.
Published: May 2018

A hierarchical sampling was performed in order to give a picture of the horizontal distribution of cyanobacterial colonies. It showed how the importance of different scales in distance changed during the summer bloom of Gloeotrichia echinulata in the moderately eutrophic and stratified Lake Erken in southeastern Sweden. G. echinulata colonies occurred in patches at a distance of ∼1000 m and the variance at smaller scales was low. For colony content of phosphorus, chlorophyll a and size, however, the largest variances were found at the 20 m (and error) scale if the variances between dates are not taken into account. It was concluded that in order to estimate the lake population of cyanobacterial colonies properly these variances must be considered when deciding the sampling program.
Effects of Daphnia on the response of mesotrophic lakes to experimental enrichment
Authors: Cottingham K. L. , Knight S. E.
Published: May 2018

We are currently involved in a whole-lake experiment designed to assess how Daphnia affect the response of mesotrophic lakes to increased nutrient loading. In the first year of the experiment, we wished to demonstrate that there are P loading rates which eutrophy lakes without Daphnia but not lakes with Daphnia. In order to do this, we needed to choose an appropriate level and schedule for the experimental enrichment. This paper describes how we made that choice, then evaluates whether our choice was successful. Based on the literature, a simulation model, and a mesocosm experiment, we decided that enriching at a rate of 1 μg P L−1 d−1 would create the desired contrast between lakes with and without Daphnia. Model simulations indicated that mean algal response to enrichment would be comparable under monthly, weekly, or continuous additions. We chose to add nutrients continuously at ambient N:P ratios. Experimental results from 1993 suggest that we achieved a nutrient loading rate consistent with our goal: chlorophyll responded less to enrichment in the lake with Daphnia than in the lake without Daphnia. The modeling, mesocosm, and whole-lake studies summarized here support the idea that Daphnia reduce chlorophyll at P loads ≤1 μg P L−1 d−1. However, cyanobacteria may escape control by all grazers at relatively low P loading rates.
Size distributions of microcystis aeruginosa colonies: a flow cytometric approach
Authors: Dubelaar G. B. J. , van der Reijden C. S.
Published: May 2018

We introduce a method for the determination of size distributions of natural Microcystis aeruginosa colonies. The analyses can be done on a routine basis with the (Eur)OPA flow cytometers. Colony sizes expressed as the number of mean single cells per colony are obtained using the ratio between the measured fluorescence per colony and the mean fluorescence of the single cells. The method is tested in three independent experiments. Several applications of this and similar analyses to cyanobacterial and phytoplanktonic studies and monitoring are discussed.
Characterising the quantity and quality of domestic wastewater inflows
Authors: Butler David , Friedler Eran , Gatt Kevin
Published: May 2018

A major source of inflow into sewer networks derives from domestic (sanitary) wastewater. The wastewater is made up of contributions from the various household appliances, influencing both flow quantity and quality. The results from two appliance usage surveys are presented to give detailed insight into the sub-daily variations of flow (quantity) and the relative importance of each appliance throughout the day. The most significant wastewater generating appliance is shown to be the WC, with the least contribution coming from the wash-basin. To establish at-source quality and its variation, limited published information was analysed in conjunction with the survey data. The contribution of each appliance to a wastewater pollutant concentration is a combination of both the appliance flow rate and pollutant load, the proportions of which vary throughout the day. Pollutagraphs were produced for BOD, ortho-phosphate, ammonia and nitrate. The WC was found to be a major contributor to all four pollutants and in particular to ammonia. The washing machine was a significant contributor to ortho-phosphate and nitrate and the wash-basin to ortho-phosphate. Inflow pollutant concentrations were of comparable magnitude to published treatment plant data, although BOD values were found to be higher than expected.
A comparison of models for coastal circulation
Authors: Stamou Anastasios I. , Christodoulou George C. , Bensasson Lisa A. , Lazaridis Iason E.
Published: May 2018

A comparative study of coastal circulation by means of two depth-averaged numerical models, a finite difference and a finite element model, is undertaken. From the application of the models to Amvrakikos Gulf, a nearly enclosed coastal water body of particular ecological interest in Western Greece, the following conclusions are drawn. (i) Circulation patterns calculated for the same eddy viscosity coefficient with both models are essentially identical. (ii) Increasing the value of eddy viscosity coefficient results in a significant reduction of the magnitude of the flow velocities with no major changes on the general flow pattern. (iii) Preliminary calculations with the finite difference model show that the incorporation of the k-ε turbulence model has minor effects on the results, but it improves the rate of convergence. (iv) Calculations with both models using alternative conditions in the open sea boundary show only minor differences in the proximity of the boundary.
Principles and approaches for numerical modelling of sediment transport in sewers
Authors: Mark Ole , Appelgren Cecilia , Larsen Torben
Published: May 2018

A study has been carried out with the objectives of describing the effect of sediment deposits on the hydraulic capacity of sewer systems and to investigate the sediment transport in sewer systems. A result of the study is a mathematical model MOUSE ST which describes sediment transport in sewers. This paper discusses the applicability and the limitations of various modelling approaches and sediment transport formulations in MOUSE ST. Further, the paper presents a simple application of MOUSE ST to the Rya catchment in Gothenburg, Sweden.
Treatment of industrial wastewaters with ozone/hydrogen peroxide
Authors: Gulyas H. , von Bismarck R. , Hemmerling L.
Published: May 2018

Treatment with ozone and ozone/hydrogen peroxide was tested in a laboratory scale reactor for removal of organics from four different industrial wastewaters: wastewaters of a paper-mill and of a biotechnical pharmaceutical process as well as two process waters from soil remediation by supercritical water extraction. Moreover, an aqueous solution of triethyleneglycoldimethylether and humic acid which was a model for a biologically treated oil reclaiming wastewater was also oxidized. The aim of the oxidation of the pharmaceutical wastewater was the removal of the preservative 1.1.1-trichloro-2-methyl-2-propanol (TCMP). Although TCMP could easily be removed from pure aqueous solutions by treatment with ozone/hydrogen peroxide, the oxidation of the wastewater failed to be effective in TCMP degradation because of competitive ozonation of other organic solutes in the wastewater. The ozonation of the paper-mill wastewater and of the soil remediation process waters decreased COD and TOC to some extent. The presence of organic wastewater solutes which contain C-C double bonds (ligninsulfonic acid in the treated paper-mill effluent and humic acid in the oil reclaiming model wastewater) were shown to yield hydrogen peroxide by the reaction with ozone. Therefore, these wastewaters are efficiently ozonated even without addition of hydrogen peroxide. Chemical Oxidation of paper-mill wastewater and of wastewaters resulting from soil remediation did not improve biological degradability of organic wastewater constituents.
Control of VOC emissions from sewers: a multi-parameter assessment
Authors: Corsi Richard L. , Birkett Steve , Melcer Henryk , Bell John
Published: May 2018

A computational model is described which facilitates multi-parameter analyses of VOC emissions from sewers. The model, CORAL+, was used to simulate more than 3.6 million combinations of five system parameters, including sewer channel slope, relative depth of flow, pipe diameter, Henry's law coefficient, and headspace ventilation rate. Lumped results were analyzed using a graphical frequency array approach to identify parameter combinations that lead to potential VOC emission hot spots. Additional modeling was completed to provide examples of passive VOC emission reductions through control of system parameters. Computational results provide information related to combinations of parameters that either never or always lead to potential VOC emission hot spots, independent of the values associated with all other parameters. Results indicate that the common assumption of infinite ventilation can lead to significant overestimates of VOC emissions, and that controlled headspace ventilation can be used to reduce VOC emissions by an order of magnitude or more. This may be of significance with respect to reducing emissions from on-site industrial sewers by maintaining biodegradable VOCs in solution prior to discharge to a downstream biological treatment system. Results also suggest that VOC emissions are highly sensitive to wastewater flow rate, increasing as flow rate decreases. This is an important observation with respect to the fact that some municipalities encourage industrial discharges at night for purposes of flow equalization.
The disinfection of municipal wastewater by ultraviolet light: a French case study
Authors: Perrot J. Y. , Baron J.
Published: May 2018

A disinfection installation using the Ultraviolet technology (Trailigaz/Trojan, series UV 3000) was installed at the end of May 1994 at the new Outreau-Le Portel (Pas de Calais) municipal wastewater plant, the outflow of which flows into the sea near Le Portel beach. Such a unit is the first of this type in France. The installation is described. The disinfection guarantees are an outflow the germ concentration of which should be below 200 Escherichia coli/100 ml geometric average over 30 days, and below 2000 E. coli 100% of the time. The results obtained from 1 June to 3 October are specified.

The disinfection performance was highly satisfactory: the mean residual Escherichia coli and faecal streptococcus values were 43 and 42 germs/100 ml for kills of 3.2 and 2.8 u.log. The disinfection guarantees have never been exceeded. In particular, only 2 samples out of 58 taken showed an E. coli concentration after UV greater than 1,000 germs/100 ml. The UV transmission (T) of the effluent varied from 35 to 63% as a consequence of the station's output increase. The least satisfactory results were recorded during periods of lower % UV T. During the 4 months of the study, three acid washes were carried out of the quartz sleeves: the speed at which the UV system used at Le Portel (low pressure UV lamps in an open channel) is contaminated is thus low.
The philosophy of Neeltje Jans
Authors: Cornelis Arnold
Published: May 2018

The name of Neeltje Jans comes from prehistoric times, born in the hidden Flemish and Dutch past, at the border of the Helle, now called the North Sea. The ‘hell’ (Helle, Houle, Ho¨lle, Holle, Harle) was the place of the dead, in the past, as the sea was the major cause of death. Neeltje Jans was the Gooddess of the sea, like Gai¨a was the mother of the earth. Neeltje Jans brought mythical security, stabilizing the emotion of anxiety in an unstable world without dikes and drainages. Rijkswaterstaat took over her role, producing security in living with water by technological means. Our twentieth century brought a technology that was admirable and powerful, but Neeltje Jans wept, as she had discovered that her intellectual child, called rationality, was blind-born. At first she kept her discovery secret, taking part in an unintended conspiracy of the twentieth century against the logic of feeling, which was called subjective and irrational. But blind rationality, pretending not to know what is quality and value, was going to loose the battle of the mind. In the recent development of the philosophy of technology, water is no longer an enemy, but a field of work for value and quality. This new development of Dutch water technology makes Neeltje Jans smile, her hidden logic has been recognized by the engineer and by a growing public encouragement. Almost half a million people come each year to share the promise of the philosophy of Neeltje Jans, along the line of the unconscious logic of feeling and without knowing consciously why. This paper intends to clear up the poetic mystery and the hidden steering of the logic of feeling behind the new technology of living with water.
Living with water: Rhine River basin management
Authors: Ruchay Dietrich
Published: May 2018

Protecting the River Rhine always means dealing with a complex international system of environment, economic and transport policy problems. About 50 million people live and work in the Rhine catchment area. Since 1950 the governments of Switzerland, France, Germany, Luxembourg and The Netherlands have co-operated in the International Commission for the Protection of the Rhine against Pollution (ICPR). So far, three phases characterize this co-operation. During the first phase up to the mid-seventies joint work was developed and organised, learning processes about national efforts took place and the first inventory of the hot spots was conducted. The second phase comprises the period from the signing of the Convention on the Protection of the Rhine against Chemical Pollution to the fire at the Sandoz warehouse at the end of 1986. It was characterized by efforts to determine international threshold values for extremely hazardous substances. The third phase will be terminated at the same time as the Rhine Action Programme in 1999. Its most important target is the return of higher species, such as the salmon, to the Rhine. In December 1994 the Conference of Rhine Ministers has to decide about next phase. It is expected that its beginning will be marked by a new improved Bern Convention.
Effects of water transfers projected in the Spanish National Hydrological Plan on the ecology of the lower River Ebro (N.E. Spain) and its delta
Authors: Prat Narcís , Ibañez Carles
Published: May 2018

This paper refers to the effects of projected water transfers, envisaged in the Spanish National Hydrological Plan, on the ecology of the lower River Ebro and its delta. Present management strategies, have resulted in highly eutrophic river water and a salt wedge which runs for more than 30 km upstream from the river mouth and its presence has been recorded during most of the year. Some parts of the delta coast are in regression as most of the inorganic sediments carried by the river are trapped in the dams. This is also leading to the sinking of the deltaic plain because subsidence and eustatic sea level rise are not compensated by new sediments. The high productivity of two bays and the coastal zone adjacent to the delta is related to influx of freshwater from irrigation channels, used in rice cultivation and the river. In the new National Hydrological Plan, a withdrawal of water upstream from the delta of 2012 hm3/year (15% of the mean annual discharge) is planned as well as the construction of 49 new reservoirs, mainly for irrigation purposes. A minimum river flow of 100 m3/s will be established by the Plan. If the plan is carried through, due to the water abstraction, forecasts based on ecological studies in the area predict: (1) increased presence of the salt wedge in the final 18 km of the river with detrimental effects on river fauna and flora; (2) serious threats to aquaculture and fisheries in the bays; (3) reduction of fish and crayfish production in the platform area; (4) further reductions in sediment and freshwater inputs to delta; (5) salinization of fields under cultivation; and (6) detrimental side effects on deltaic ecosystems.
A method for describing biofilm surface roughness using geostatistical techniques
Authors: Gibbs J. T. , Bishop P. L.
Published: May 2018

Biofilm reactors, such as rotating biological contactors (RBCs) and trickling filters, have been used to treat both municipal and industrial waste streams. One fundamental property of biofilms which may affect their performance is surface roughness, or the magnitude of variability in height over the structure's profile. This property has an effect on the rate of diffusion of nutrients into the biofilm for degradation through its influence on the thickness of the concentration boundary layer.

The method presented here to quantify the surface characteristics of a biofilm involves the in situ analysis of biofilm surface profile data collected at discrete points. For each point, a microprobe is lowered from some datum above the surface, and the distance down to the biofilm surface is measured at that point. Statistical analysis performed on the data set produces the correlation coefficient between heights on the biofilm surface at various separation intervals. A graph relating the correlation coefficient to the separation interval between heights is constructed from many points to determine the length over which points with low correlation can be collected. A set of nearly independent height data collected at that length interval is then analyzed for mean and standard deviation. The resulting statistics are characteristic of the magnitude of the variability between independent heights on the surface profile, and can be used to compare and contrast the roughness of biofilm surfaces.

This method was used to define the roughness of artificial and real biofilm surfaces. Artificial biofilms, which were made from agar roughed with sand paper of varying grit size, were found to have distinct and consistent roughness, as determined by this method. It was useful to compare the standard deviation (roughness) of real biofilms to these values, because the roughness of sand paper is easily observable, and standardized.
Growth of an aerobic and an anoxic toluene-degrading biofilm - a comparative study
Authors: Arcangeli Jean-Pierre , Arvin Erik
Published: May 2018

The growth dynamics of a toluene-degrading biofilm was investigated under aerobic and under nitrate-reducing (anoxic) conditions. The study was performed with a continuously fed biofilm reactor (biodrum system). Under denitrifying conditions, the maximum toluene degradation in the reactor was achieved during the exponential growth phase of the biofilm. Under aerobic conditions, however, the maximum toluene degradation was reached during the lag phase of biofilm growth. Meanwhile, a simultaneous increase of the suspended biomass concentration in the bulk occurred concomitant with the toluene removal. The comparison of the structure of the aerobic and anoxic biofilms indicated that the anoxic biofilm was smooth and regular whereas the aerobic biofilm showed a lot of irregularity and a filamentous structure on top of the biofilm. Both the aerobic and the anoxic growth were modelled using the computer programme BIOSIM from EAWAG. The models considered active and inactive biomass. The active biomass was growing on toluene as sole carbon source, whereas the inactive biomass was composed of polymers and dead cells unable to degrade toluene. Model simulations showed that the biofilm activity was mainly concentrated in the top-layer of the biofilm under both aerobic and anoxic conditions.
Nitrification in a tertiary trickling filter at high hydraulic loads - pilot plant operation and mathematical modelling
Authors: Wik T. , Mattsson A. , Hansson E. , Niklasson C.
Published: May 2018

A large pilot scale trickling filter with an established nitrifying biofilm on a cross flow plastic material having a high specific surface area has been used to evaluate the short term effects of changes in hydraulic load and influent ammonium concentration. The experiments were conducted as 15 randomized 22 factorial design experiments where the hydraulic load was set at 5.7 or 11.3 m/h and the influent ammonium concentration was set at 8 or 16 gN/m3 independently of the hydraulic load. An evaluation of the factorial design experiments revealed no difference in nitrification rate between a high hydraulic load and a low ammonium concentration and vice versa for the two setups with the same ammonium load. The short term dynamics were investigated by pulse experiments and step changes in ammonium load. These investigations revealed that the amount of water in the trickling filter was approximately independent of the flow and that stable conditions after a drastic change in the influent conditions were achieved in the time order given by the residence time distribution. A mathematical model based on a general multispecies biofilm model was used for comparison with the experimental data. The model simulations showed good correlation with experimental data indicating a feasibility for multispecies biofilm models also for large scale processes.
An experimental study on aerobic denitrification with polyvinyl alcohol as a carbon source in biofilms
Authors: Bang D.-Y. , Watanabe Y. , Noike T.
Published: May 2018

Aerobic denitrification occuring in the biofilms attached to a partially submerged RBC, was investigated. Denitrification using polyvinyl alcohol (PVA) as a organic carbon source, was well proceeded by aerobic RBC systems at 25 °C. At an influent C/N ratio of around 1.2, the maximum net-denitrification efficiency was about 78% at a TOC loading of 2g/m2/d. In a chemostat experiment, aerobic denitrification was well proceeded under the dissolved oxygen concentration of 3 to 6 mg/L. The PVA-decomposing bacteria, nitrifiers, and denitrifiers co-existed in the biofilm, but the population of PVA-decomposing bacteria and denitrifiers in the surface layer was 1 to 2 orders of magnitude higher than those in the middle and bottom layers. It may indicate that the surface layer had a higher denitrifying activity. The nitrogen mass balance obtained using the experimental data clearly indicates a reasoning for aerobic denitrification.
The direct measurement of bacterial growth in biofilms of emergent plants (Schoenoplectus) of an artificial wetland
Authors: Pollard Peter C. , Flood Janine A. , Ashbolt Nicholas J.
Published: May 2018

In the wastewater industry, artificial wetlands are used to improve water quality. Biofilms on these plant surfaces are thought to retain most of the active bacterial community that decomposes organic matter and aid in nutrient removal. Wetland design and operation could be enhanced with the in situ measurement of growth and dynamics of the biofilm-bacteria. This paper describes how to directly measure the rate of bacterial growth on the surface of submerged sections of emergent macrophytes, with the radioactively labelled DNA precursor [methyl-3H] thymidine. We found that the isotope was rapidly and efficiently incorporated into the bacteria growing on plant surfaces, without a lag phase. Isotope dilution was avoided by using a specific activity of 2 Ci.mmol−1. Highest growth rates appeared to be associated with the top 10 mm of submerged plant tissue. The method accommodated the natural heterogeneity of biofilms both between plants and along the stem of the same plant. These findings are important for future studies of biofilm dynamics.
A methodology for water quantity and quality assessment for wetland development
Authors: Vadas Rolando G. , Garcia Luis A. , Labadie John W.
Published: May 2018

A methodology is presented for water quantity and quality assessment for wetland development which enables planners to evaluate the results of restoring and managing a large wetland complex based on a set of criteria developed under multi-disciplinary guidelines. The methodology includes addressing temporal and spatial variability of climatic data for determination of wetland water requirements; determination of wetland evapotranspiration; determination of critical areas for wetland and agricultural development using GIS; modelling the water delivery ystem (quantity, quality, location, and timing) of a wetland complex using HEC-5 and WASP; and water management using the GAMS/MINOS optimization program. The methodology is applied through the use of a Decision Support System (DSS). The goal of the DSS is to provide tools for spatial and temporal simulation, evaluation and management of a wetland system. The user has access to a common analysis environment consisting of models and data within a Graphical User Interface (GUI). Simulation and optimization modules, combined with a graphical user interface, permit efficient and convenient study of various resource management scenarios.
Groundwater flow systems analysis on a regional and nation-wide scale in the Netherlands; the use of flow systems analysis in wetland management
Authors: Kloosterman F. H. , Stuurman R. J. , van der Meijden R.
Published: May 2018

The project “National Groundwater Flow System Analysis” in The Netherlands was initiated in 1991 and will last until 1995. Financed by three Dutch Ministries, the project aims at the mapping of the regional groundwater flow systems to support policy makers at national levels and water/nature resources management. Much emphasis is put on biotic aspects such as the relation between groundwater and patterns in vegetation. The results are used in a detailed flow system analysis of the eco-hydrological valuable drainage basin of the brooks Beerze and Reusel in the southern parts of the country. In this study vegetation patterns and hydrological situations were analyzed in present and in historical settings to unravel the changes in the last decades leading to severe deterioration of habitats and wetlands. Historical data on flora from the beginning of this century on the basis of km-grid cells show a strong relation with the historical exfiltration areas where deep alkaline groundwaters rich in calcium-carbonate emerged. Agriculture and man-made changes to the natural drainage systems have led to diminishing nature values. Combining a sound understanding of the groundwater flow systems and the changes in the last decades produced a number of practical and viable measures to restore historical wetland settings and to preserve existing ones.
The habitat evaluation procedure as a tool for ecological rehabilitation of wetlands in the Netherlands
Authors: Duel H. , Specken B. P. M. , Denneman W. D. , Kwakernaak C.
Published: May 2018

In the USA, the Habitat Evaluation Procedure (HEP) has become a standard approach for impact assessment and evaluation of measures and management activities causing changes in the environmental conditions of the habitats for fauna species. Recently, the method was implemented in The Netherlands. HEP is used to predict the ecological impact of measures and management activities concerning the ecological rehabilitation of rivers, tidal wetlands, lakes and marshes. For more than 30 fauna species the habitat requirements and preferences have been modelled. Examples of species-habitat relationships are presented. First results of the application of the method in ecological rehabilitation projects of rivers, lakes and marshes are presented. The results show that the HEP approach is a useful tool in ecological water management.
Characteristics of leachate produced from simulation of landfill in a tropical country
Authors: Karnchanawong Somjai , Ikeguchi Takashi , Karnchanawong Seni , Koottatep Suporn
Published: May 2018

Four different heights of lysimeter were prepared to investigate the leachate characteristics produced from waste beds. The solid wastes from Chiang Mai municipal area were filled into the lysimeters with an inplace density of about 0.85 ton/m3. The experiment had been started for 853 days from May, 1990 to October, 1992. The leachates were collected every week to every month depending on the age of the waste and analysed for pH, conductivity, total solids, suspended solids, total dissolved solids, total volatile solids, alkalinity, acidity, total volatile acid, Cl−, SO=4, BOD, COD, TOC, TKN and NH3−N. The results showed that conductivity, volatile acid, total solids, total volatile solids, COD, BOD and TOC were very high in the first rainy season or in the first dry season, after that, they decrease abruptly, and then gradually decrease until the end of the experiment. Acidity, alkalinity, suspended solids, TKN and NH3−N were high in the first rainy season and gradually decreased until the end of the experiment. High percentage reduction of acidity, volatile acid, COD, BOD and TOC concentrations in the leachate produced from lysimeters after one year of waste filling showed that the acidogenic phase of the biodegradation process had terminated and that the major portion of carbonaceous organic matter in the waste bed had been utilised within the first year of the experiment. For the deeper waste layer, nitrogenous compounds in the leachate produced after two years of waste filling were still high due to the low activity of nitrification in the waste bed. It was found that the shallower waste layer produced lower concentrations of pollutants in the leachate. Higher amounts of leachate volume and extracted substances per dry weight of wastes were produced from the shallower waste layer.
The use of a zeolite-iron column for residual ammonia and phosphorus removal in the effluent from a membrane process as an on-site small-scale domestic wastewater treatment
Authors: Ratanatamskul C. , Chiemchaisri C. , Yamamoto K.
Published: May 2018

Laboratory-scale experiments were performed to investigate the performance of the on-site small-scale combined system of membrane separation bioreactor (MSB) and zeolite-iron (Z-Fe) column. Average nitrogen removal by the membrane separation bioreactor was varied from 83% at an influent nitrogen concentration of 30 mg/l to 50% at 75 mg/l. Residual ammonia nitrogen in the effluent from the membrane separation bioreactor was further polished by a Z-Fe column to an initially non-detectable concentration and finally to 1.2 mg/l. The average phosphorus removal by this column unit was 70%. Improvement by providing aeration to the bottom part of iron bed in the long column improved phosphorus removal efficiency to as much as 92% until water logging occurred inside the column. Moreover, further improvement was achieved by inserting three short columns in series for 116 day of operation. Average effluent phosphorus concentrations of 1.2, 0.39 and 0.16 mg/l were obtained after the 1st, 2nd and 3rd column respectively with an applied influent phosphorus concentration of 5.3 mg/l on average. Furthermore, batch experiments were carried out to investigate the factors, such as pH and temperature, which affect the performance of the Z-Fe column in phosphorus removal.
Aquaculture feeds and the environment: the asian experience
Authors: Tacon A. G. J. , Phillips M. J. , Barg U. C.
Published: May 2018

Asia, the birth place of aquaculture, supplies 85% of global aquaculture production and has had a long tradition in the development and use of different dietary feeding strategies, ranging from the use of fertilizers and simple supplementary feed mixtures to the manufacture of ‘water-stable’ pelleted shrimp feeds. The present paper reviews the different aquaculture feeding strategies used within semi-intensive and intensive farming systems in selected Asian countries, and in particular examines their relative impacts upon the aquatic environment. Emphasis is placed on the environmental compatibility and central role played by small scale polyculture-based integrated farming systems in Asian aquaculture, and the need to carefully balance exogenous supplementary feed inputs with the endogenous supply of natural food organisms within semi-intensive pond farming systems. In the case of intensive pond/cage-based farming systems attention is focused on the need to further improve feed formulation, feed manufacture, and on-farm feed and water management so as to maximize feed intake and feed efficiency, and minimize feed wastage and water pollution. Furthermore, in view of the negative experiences of some countries in the region with deteriorating water quality and disease outbreaks within intensive pond/cage-based farming systems, there is an urgent need to improve farm husbandry methods and reduce the current reliance of the aquaculture sector on chemotherapeutants; including limiting the use of the antibiotics only to qualified personnel by developing appropriate Codes of Practice. In this respect there is also a need to recognize the important role played by nutrition in disease resistance. In addition, the paper reviews the legislative controls concerning aquafeed manufacture in selected Asian countries, and highlights the implications of applying government feed legislative controls (i.e. relating to feed composition, feed manufacture, feed efficiency or water pollution) directly from one environmental setting or country to another, and urges countries to develop their own solutions depending upon the farming system employed (i.e. intensive or semi-intensive; tank, cage or pond; coldwater or warmwater; freshwater or seawater), national government policies and priorities, and the resources available to them. In conclusion the paper stresses the key role which can be played by the resident aquafeed manufacturing sector in helping farmers, not only in the provision of feed inputs, but more importantly concerning the management of the feed on the farm and in the use of appropriate environmentally sound husbandry practices; feed manufacturers usually having the closest contact with farmers and in many countries being the only link in the chain between the farmer and the government legislature.
Environmental impact of nutrients from nordic fish farming
Authors: Enell M.
Published: May 2018

During the last 20 years there has been an interesting development of the Nordic fish farming, with regard to the feeding and farming technology and to the increase in production quantities. During the period 1974-1994 the production increased from 15,800 to about 250,000 tonnes/year. In 1974 the major part of the production was in Denmark, and in 1994 the major part was in Norway. The nutrient impact of fish farming on surrounding sea areas is mainly a function of the feed coefficient, the feed composition and metabolic processes in the fish. The comprehensive development of the feed composition and the feeding technology has resulted in reduced load of unmetabolized nutrients from fish farms, calculated per tonne fish produced. In 1974 the mean Nordic feed coefficient was 2.08 and in 1994 the coefficient was 1.25. Feed coefficients of 1.0-1.1 are now reported for Danish and Norwegian freshwater and marine fish farms. The nitrogen (N) and phosphorus (P) content of the feed has decreased, in addition the quality of the nutrient substances in the feed has changed, especially for N. The N content has decreased from 7.8 to 6.8% during the period 1974-1994 and the content of P has decreased from 1.7 to 0.7% during the same period. This development of the feed coefficient and the feed composition has resulted in a present load from a typical Nordic fish farm of 55 kg N and 4.8 kg P/t fish produced. The figures for 1974 were 132 kg N and 31 kg P/t fish produced.

The Nordic fish farming production in 1994 resulted in a load of about 13,750 t N and about 1,200 t P on the actual recipients. The load from the Swedish, Finnish and Danish fish farming operations, with the Baltic Sea and the Skagerrak as the recipients, is negligible in comparison with other pollution sources. The quantities of N and P from the fish farming are equal to 0.5% of the atmospheric deposition on the sea surface and 3% of the atmospheric P load. Norwegian, Icelandic and the Faroe Islands fish farming operations are using the North Sea and the Norwegian Sea as the recipients. However, the nutrient load from single fish farms in certain coastal and inland water bodies can be significant and must be considered in the impact assessment together with other sources.
Bioengineering and biotechnological strategies for reduced waste aquaculture
Authors: Mayer Ian , McLean Ewen
Published: May 2018

While recent years have witnessed dramatic advances in the reduction of aquaculture waste production, primarily due to advances in feed technology, the co-implementation of new bioengineering and biotechnological strategies are vital for alleviating the environmental impact of the rapidly expanding global aquaculture industry. The deployment of a new generation of automated feeding devices, and continued advances in recirculation technologies for land-based systems are amongst the more significant bioengineering advances that have resulted in reduced waste production. Advances in feed technologies will continue to play a pivotal role in the reduction of aquculture waste. Further, the advent of modern recombinant DNA technologies now allows for the economic production of a variety of feed supplements, most notably microbial phytases. Other, often overlooked, biotechnological strategies for achieving improved growth and conversion efficiencies include such physiological modifications as sustained exercise and compensatory growth. Somewhat more controversial biotechnological methods which may be beneficial in reduced waste management include endocrine manipulations and genetic engineering. Again, recent advances in recombinant DNA and transgenic technologies have also led to renewed interest in these strategies.
Measurements of feed intake and excretion in fish using radiography or chemical indicators
Authors: Gudmundsson O. , Tryggvadottir S. V. , Petursdottir Th. , Halldorsdottir K.
Published: May 2018

Experiments were conducted to determine the effectiveness of measuring feed consumption and excretion in salmonid fish by radiographic and chemical indicator methods. To do this it was also necessary to measure concurrently the digestibility. Digestibility was determined in 16 diets of different origin comparing n-alkanes (C28 and C32) as indigestible indicators with chromium sesquioxide and celite. Research was also conducted comparing the radiographic method for measuring feed intake with that of using C32 alkane as an external indicator to measure faecal output. The results show that n-alkanes can be used as internal and external indicators in measuring faecal output, digestibility and intake in fish. The radiographic method and the n-alkane indicator method are compatible for the measurement of feed consumption, but both methods give high variability, making small differences in feed consumption difficult to detect.
Formulation of fish diets with reduced phosphorous content
Authors: Jacobsen C. , Børresen T.
Published: May 2018

The reduction of phosphorous waste from farmed rainbow trout (Oncorhynchus mykiss) was attempted by feeding diets of reduced P content. The protein source was fishmeal in which the bone fraction had been removed. This was achieved either by solubilizing the fish material (press cake) by enzymatic treatment and subsequent filtering, or by removing the fish bones by a skin/bone separator. Two fish species were used, sand eel (Ammodytes marinus) and sprat (Sprattus sprattus). Due to the small size of the fish, only bones were retained in the skin/bone separator. Traditional fishmeal from the same species were used for control experiments. The fishmeal samples were used together with other ingredients in a traditional extruded dry feed formulation (Ecolife 19).

The diets were used in full scale experiments in a fresh water fish farm in Denmark, as well as in small scale experiments in aquaria. Direct calculations on the feed conversion ratio and the specific growth rate on both experiments showed that the enzyme treated codes performed less well than the other codes. However, when compensating for the different energy content of the diets, the enzymatic treatment did not give rise to a higher feed conversion ratio, nor did it give rise to a lower average growth rate than the other codes. It was not possible to make any final conclusions with respect to the effect of the enzymatic treated fishmeal on the pollution risk from P. This was due to large variation on the P determinations.
Effects of dietary protein/energy ratio, ration size, dietary energy source and water temperature on nitrogen excretion in rainbow trout
Authors: Médale F. , Brauge C. , Vallée F. , Kaushik S. J.
Published: May 2018

Postprandial nitrogen excretion was measured on groups of rainbow trout of mean body weight (MBW) 35g, fed, from maintenance to near satiation, diets containing graded levels of digestible energy (14 to 20 kJ/g dry matter) with digestible protein (DP)/digestible energy (DE) ratios of 18 and 23 mg/kJ at each protein level (DP: 32.5 or 37% dry matter). Irrespective of the diet and the ration size, urea-N excretion amounted to 15-16% of ammonia-N excretion. The higher the dietary DP/DE ratio, the greater was the amount of ammonia excreted. At high ration levels (1.5% and 2% of MBW/d), N excretion was 39-40% of digestible N intake for diets with a DP/DE ratio of 18 mg/kJ and 44% of digestible N intake for diets with a DP/DE ratio of 23 mg/kJ irrespective of the dietary protein level. At lower ration levels, N excretion as percent of N intake was higher than at higher feeding levels.

Another experiment was performed to compare the effect of dietary lipid and digestible carbohydrate on ammonia excretion in rainbow trout reared at two water temperatures (8°C and 18°C). Neither water temperature nor dietary sources of non-protein energy had any significant effect on N excretion expressed as proportion of digestible N intake.