bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen removal in multi-stage wastewater treatment plants by using a modified post-denitrification system
Authors: Schreff Dieter , Wilderer Peter A.
Published: May 2018

Systems in which denitrification follows nitrification (post-denitrification) copy the natural sequence of nitrogen removal. The disadvantage of post-denitrification, however, is that an external carbon source must be added to the denitrification reactor. In the concept discussed in this paper, excess sludge from a high loaded activated sludge plant is used as carbon source and as source of denitrifiers in a three-stage system. The sludge is fed into a anoxic reactor placed in between the nitrification reactor (e.g., trickling filter) and the final clarifier. Two different operation methods were investigated at a pilot-scale system set up at the Ingolstadt wastewater treatment plant. Low nitrate effluent values were obtained at high sludge feeding rates, but at the expense of a significant increase in turbidity and NH4-N effluent concentrations. This problem could be solved by a reduction of the sludge feeding rate and by applying intermittent feeling. The effluent turbidity was kept at an acceptable level, but denitrification was relatively slow in progress. To achieve both low effluent turbidity and low nitrate discharge, a combination of pre- and post-denitrification is recommended.
Experiences of nitrogen and phosphorus removal in deep-bed filters at henriksdal sewage works in Stockholm
Authors: Jonsson L.
Published: May 2018

Deep-bed down-flow two-media filters were used in pilot plant studies with filtration of secondary settled wastewater. FeSO4 or FeCl5 was applied as a precipitation agent, and NaAc·3H2O was chosen as a carbon source when denitrification was desired. The concentration of PO4-P in the filtrate from the pilot plant study never exceeded 0.05 mg PO4-P/l when iron salts were dosed. The curves showing the concentration of P-tot and PO4-P in the filtrate as a function of the quotient between the dosage of iron and the concentration of PO4-P in the influent to the filter followed approximately an exponential relationship. The total nitrogen reduction over the filter bed increased from an average of 2.3 mg (NO3+NO2)-N/l at the beginning of each experiment to an average of 4.3 mg (NO3+NO2)-N/l towards the end of the test. When only secondary settled wastewater, suspended solids, primary settled wastewater, iron salts, or sodium acetate was added, at a hydraulic load of 10 m/h, the time before clogging became 100 h, 10–15 h, 20–40 h, respectively. Almost the entire pressure drop was located on the surface of the filter bed and 0.25 metre down in the expanded clay layer.
Experience with the upgrading of 14 treatment plants to N & P removal in the municipality of Aarhus
Authors: Sørensen J. , Andersen J. , Andreasen K. , Hald K.
Published: May 2018

The experience with the upgrading of 14 treatment plants to N and P removal is presented. For all plants it has been possible to fulfil the effluent standards. Through process optimization it has been possible to achieve a stable biological P-removal. The introduction of control systems based on nn-line sensors for ammonia, nitrate and phosphate has resulted in a more stable effluent quality and an increased capacity. The experience also shows that it can be very difficult to predict and control the changes in the industrial load. From this it is concluded that instead of spending a lot of time on fine-tuning the design criteria in the design phase, it may be better to incorporate a considerable flexibility into the design, allowing the processes to be adjusted to the changing operational conditions during time.
On-site stormwater management as an alternative to conventional sewer systems: a new concept spreading in Germany
Authors: Sieker F.
Published: May 2018

In Germany a new stormwater management system is spreading across the country – the so called “Mulden-Rigolen-System” (MR-System), which may be translated as the ‘Swale-Infiltration Trench System’. The overall applicable system consists of on-site located swale-trench-elements which are connected by throttled sewers to a decentralized stormwater management system. The elements are designed and dimensioned in order to allow the highest possible infiltration of stormwater runoff. This is obtained by a short-term storage in the grassed swale and a long-term storage provided by the trench. The latter is formed by highly porous material such as gravel or lava granules, wrapped in geotextile. By infiltration through the active soil layer along the swale bottom, stormwater quality is enhanced up to the quality of drinking water. The MR-System has been applied in many German projects, not only in new developments, but also as a retrofit measure in the existing urban developments.
Tracer studies of the hydraulics of tapered flocculation
Authors: Ives K. J. , Hoyer O.
Published: May 2018

A pilot plant, with a flow capacity of 600 m3/h, was constructed as a tapered (diminishing velocity gradients) flocculation system. The flowthrough patterns of a series of 4 tanks and a transfer channel were evaluated hydraulically using an alkali (NaOH) as a tracer, using pH probes. Ideally, the tanks, containing stirrers, and the channel should have plug flow conditions. The actual conditions were affected by the inlet and outlet arrangements, and directions of rotations of the stirrers. By creating a high steady-state plateau of pH11, the subsequent decrease of pH when the alkali was cut off gave a measure of the flow regime in each tank and the channel. By adjustment of the inlet and outlet weirs and slots, the stirrers and the insertion of baffles, a best design was derived allowing for compromises among the units. It was shown that an adjustment to optimise one tank or channel affected the performance of both upstream and downstream units.
Biological leaching of trace metals from stormwater sediments: influential variables and continuous reactor operation
Authors: Anderson B. C. , Brown A. T. F. , Watt W. E. , Marsalek J.
Published: May 2018

Research was conducted on a bioremediation process for the treatment of urban stormwater sediments contaminated with trace metals. Referred to as bioleaching, the process relies on specific strains of naturally occurring, acid-producing bacteria to reduce the pH of a sediment slurry, thereby solubilizing adsorbed and particulate metals into the liquid phase, for collection and processing. The research was first conducted at the bench-scale to investigate the process and the influence of the variables substrate loading, solids loading, temperature, starting pH, benefit of inoculation, mixing, aeration and grade of substrate used. Of these, it was found that temperature and substrate availability exerted the greatest influence on the acidification process. This information allowed for the design of pilot-scale 100 L continuous bioreactors for treating stormwater sediments. At retention times as low as 1.3 days, these reactors achieved almost complete solubilization of copper and zinc, while chromium and lead were partially removed. These results indicate that bioleaching is a promising alternative for the remediation of these contaminated sediments.
The role of physical-chemical treatment in wastewater reclamation and reuse
Authors: Adin Avner , Asano Takashi
Published: May 2018

Amid the heightened public health concerns for emerging microorganisms such as cryptosporidium and enteropathogenic E. coli in the water environment, there have been many instances where optimization of chemical coagulation-flocculation processes and filtration of wastewater was not achieved in practice, resulting in waste of coagulant chemicals and breach of the multiple barriers to pathogen removal and inactivation; thus, unnecessarily endangering public health. In addition, lack of information on the optimization of these processes has hampered the establishment of alternative and more cost-effective wastewater reclamation methods for tertiary and advanced wastewater treatment.

Thus, the purpose of this paper is to evaluate the basic factors affecting the optimization of chemical coagulation-flocculation and filtration processes in municipal wastewater reclamation and reuse, based on the theoretical developments and practical applications. Reference is also made to the wastewater treatment processes and operations that can produce reclaimed water with an extremely small probability of enteric virus contamination.
Drinking water production by coagulation-microfiltration and adsorption-ultrafiltration
Authors: Yuasa Akira
Published: May 2018

Microfiltration (MF) and ultrafiltration (UF) pilot plants were operated to produce drinking water from surface water from 1992 to 1996. Microfiltration was combined with pre-coagulation by polyaluminium chloride and was operated in a dead-end mode using hollow fiber polypropylene and monolith type ceramic membranes. Ultrafiltration pilot was operated in both cross-flow and dead-end modes using hollow fiber cellulose acetate membrane and was combined occasionally with powdered activated carbon (PAC) and granular activated carbon (GAC) adsorption. Turbidity in the raw water varied in the range between 1 and 100 mg/L (as standard Kaolin) and was removed almost completely in all MF and UF pilot plants to less than 0.1 mg/L. MF and UF removed metals such as iron, manganese and aluminium well. The background organics in the river water measured as KMnO4 demand varied in the range between 3 and 16 mg/L. KMnO4 demand decreased to less than 2 mg/L and to less than 3 mg/L on the average by the coagulation-MF process and the sole UF process, respectively. Combination of PAC or GAC adsorption with UF resulted in an increased removal of the background organics and the trihalomethanes formation potential as well as the micropollutants such as pesticides. Filtration flux was controlled in the range between 1.5 and 2.5 m/day with the trans-membrane pressure less than 100 kPa in most cases for MF and UF. The average water recovery varied from 99 to 85%.
Point and diffuse load of nutrients to the Baltic Sea by river basins of North East Germany (Mecklenburg-Vorpommern)
Authors: Behrendt H. , Bachor A.
Published: May 2018

The results of a study on the riverine nutrient emissions and loads of nine river basins of the country Mecklenburg-Vorpommern to the Baltic Sea are presented for the period 1992 to 1994. The basins represent about 76% of the Baltic Sea catchment area of Mecklenburg-Vorpommern. The population living in the basins causes point emissions of 1752 tN/a and 293 tP/a. The analysis of diffuse emissions of nutrients is based on digitized maps of the land use and the soil types, the livestock numbers in the basins and measurements on the nutrient concentrations in the groundwater and drainage areas. The used method considers different pathways of diffuse sources as load from urban areas, erosion, load by groundwater, and drainage systems, atmospheric deposition, and direct load by agricultural activities. The dominant pathway of nitrogen emissions is the emissions of drainage. For phosphorus the emissions by erosion, groundwater and drainage are the main sources. The emissions of point sources contribute to the total emissions to 10% (N) and 25% (P), respectively. The measured nutrient load at the monitoring stations of the rivers is in all cases lower than the sum of the nutrient emissions. This behaviour can be explained by intensive retention processes in the rivers, which depends on the specific runoff, and for nitrogen additionally on the area of surface water in the basin.

Measures against the high nutrient load have to be focussed on the reduction of diffuse sources, especially the emissions of nitrogen and phosphorus by drainage systems have to be reduced, and additionally in the case of phosphorus the emissions by erosion and by direct agricultural load.
Decreased leaching and increased retention potential co-operative measures to reduce diffuse nitrogen load on a watershed level
Authors: Gustafson A. , Fleischer S. , Joelsson A.
Published: May 2018

Governmental programmes and international agreements to counteract eutrophication have largely not attained agreed goals (e. g. reduction by half of the anthropogenic nitrogen load on Swedish coastal waters and to the Baltic Sea). One explanation to the fact that the goals are not achieved yet might be that the most effective building blocks to counteract diffuse pollution are far from being fully implemented. It is therefore important to stress the potential in some very effective measures and find ways to fully implement them in a strategic way at the watershed level. To avoid overdoses of fertilizers in crop production is very important since overdoses lead to an exponential growth in the leaching magnitude. Field experiments indicate that the use of winter crops or an undersown catch crop outside the main cropping season has cut back the nitrate losses with up to 75% in a single year and close to 50% during a longer period of successive years. In southern Sweden, the area of wetlands has been decreased considerably (more than 90%) by melioration activities. In a recent project, mass balances in full scale restored ponds, verified the importance of ponds and wetlands in nitrogen retention. Per unit area, increased nitrogen loading implied increased nitrogen retention, but often a decreased retention percentage. Sedimentation of organic material must be favoured in order to obtain adequate conditions for denitrification. To achieve the governmental goal in nitrogen load reduction, proper agricultural practices must be combined with restoration of ponds/wetlands.
Stochastic modelling of N-leaching using gis and multivariate statistical methods
Authors: Németh T. , Pásztor L. , Szabó J.
Published: May 2018

After the growing season, a part of the nitrogen remains in forms sensitive to changes of the conditions, such as nitrate. In years with above-average precipitation a significant amount of nitrate can leave the rooting zone. Integration of knowledge related to environmental conditions of a certain area with the soil, water, and crop management practices helps to prevent the simultaneity of the unfavourable processes leading to nitrate leaching, thus water resources may be protected from nitrate pollution of agricultural origin. In our work we present a stochastic approach for the evaluation of the vulnerability of soils for nitrate leaching. The method was applied for mapping N-leaching hazard in Hungary at a scale of 1:1M.
Simulation of nonpoint source pollutant loadings from urban area during rainfall: an application of a physically-based distributed model
Authors: Haiping Zhang , Yamada Kiyoshi
Published: May 2018

A physically-based, distributed model, PROUW, is applied to a small urban watershed in Japan with an area of 66.18 ha. The model includes a description of evapotranspiration, percolation, runoff generation, overland flow routing, pollutant accumulation in dry weathers and washoff during storm events, overland pollutant routing, and flow and pollutant routing in drainage system. The finite difference schematization of the urban watershed provides a representation of the spatial pattern of topography, land-use, soil types and meteorological inputs. The watershed is divided into 7500 grids of 10m × 10m and the runoff rate and pollutant loadings are simulated with a time step of 5 sec. The data for the storm event of April 28, 1995 is used for model calibration. Simulated hydrograph and pollutographs of the storm event of April 18, 1995 are compared with the observed data. Results show a reasonable degree of fit, indicating that the model provides a reasonable interpretation of the overall runoff and pollutant generation processes in the urban area. The results also suggest that the model should be improved further by incorporating new reliable equations for pollutant washoff estimation.
Experimental observations of salt purging in a model sea outfall diffuser with eight soffit connected risers
Authors: Burrows R. , Ali K. H. M. , Spence K. , Chiang T. T.
Published: May 2018

Improved rehabilitation design for the long-term hydraulic function of marine outfalls with soffit connected risers is the main aim of the research programme reported here. As a step towards this goal a better understanding of the processes of saline intrusion and saltwater purging has been developed from detailed laboratory studies. Unsteady flow cycles have been investigated and observed riser purging sequences have been compared against theoretical criteria. From the monitoring of riser flow salinity, quantitative measures of the salt wedge front entrainment process have been obtained together with indicative figures for salt wedge expulsion rate. This interim outcome is intended to alert the designer and operator of outfalls of the potential problems with soffit connected riser systems.
Use of variable orifice “duckbill” valves for hydraulic and dilution optimization of multiport diffusers
Authors: Duer Michael J.
Published: May 2018

The use of variable orifice “duckbill” valves hydraulically optimizes marine effluent diffusers by generating higher jet velocity at low flows, reduced headloss at peak flow, and a more uniform port discharge distribution. Recent laboratory experiments showed that near field mixing and dilution were substantially improved with duckbill valves, and the purging of salt water from an outfall occurs at much lower flow than the theoretical flow required to purge a conventional outfall. An inherent characteristic of the duckbill valve is that it is a check valve that prevents the ingress of salt water, sediment, and marine organisms into the outfall during periods of low flow and hydraulic transients.

This paper presents the hydraulic advantages of variable orifice duckbills verses fixed orifices with emphasis on enhancements in initial dilution and minimization of headloss at peak flow. The process of salt water purging will also be presented along with a brief discussion on failure mechanisms of conventional diffusers.
European attitude to the disposal of wastewater in the sea: the case for a (European) network for sea outfall research
Authors: Burrows R. , Neves M. J. V. , Larsen T. , Carratelli E. P. , Veltri P.
Published: May 2018

A network of European organisations with interests in the utilisation of long sea outfalls as an integral element in the sewerage of coastal communities has recently been established. The central aim is to provide a focus both for the adoption of best practices and the identification of outstanding problem areas across the European community, against the background of the standards of practice demanded by the recent implementation of the European Commission's (EC) Urban Waste Water Treatment Directive. This article is intended both to inform a wider audience of the existence of the network and to extend the call for membership both to European parties and others interested in being informed on European developments in this area.
Use of historical rainfall series for hydrological modelling – workshop summary
Authors: Einfalt Thomas , Arnbjerg-Nielsen Karsten , Fankhauser Rolf , Rauch Wolfgang , Schilling Wolfgang , Nguyen Van-Than-Van , Despotovic Jovan
Published: May 2018

From 4-7 December 1997 the 3rd International Workshop on Rainfall in Urban Areas took place in Pontresina, Switzerland. Forty-five participants from 20 countries around the world made it a success. Presentations and discussions represented a high scientific level without neglecting the practitioners point of view. In fact, future trends, such as coupling of models of different origins for rainfall forecasting, detailed spatial analysis of rainfall, methods for quality control of measured data, and aspects of climatic change were cornerstones of the workshop. In the following, the outcome of the sessions are briefly highlighted.
A short time-step point rainfall stochastic model
Authors: Thauvin V. , Gaume E. , Roux C.
Published: May 2018

This paper deals with the development of a point rainfall stochastic model, which generates synthetic sequences of 5 min rainfall rates. This time step is necessary to derive correctly the short hydrological response of urban catchments. The model simulates dry and rainy sequences in alternance. Particular attention has been paid to intense periods which are of utmost importance as far as flooding is concerned. This leads us to describe a rain event as a juxtaposition of inter-showers and showers. The intensity of an inter-shower is assumed to remain constant. Showers are defined as a succession of « peaks » with a single maximum and a trapezoidal shape. The model has been calibrated with raingauge data from the Seine Saint Denis area, situated near Paris, in France. This paper presents the definition of the model variables, the calibration of their probability distributions and the initial validation results. The conclusion insists on the fact that for the model to be completed, hydrological validation is necessary.
Formulating and testing a rain series generator based on tipping bucket gauges
Authors: Arnbjerg-Nielsen Karsten , Madsen Henrik , Harremoës Poul
Published: May 2018

Changing needs of the society also change the goals of hydrological calculations. The “design storm” concept cannot provide adequate answers to the complex problems on many time scales that society is facing today. This paper present a novel approach to generate artificial rain data with a time resolution sufficient for urban hydrology. The model is based on Wolds process of intervals, ie. it generates waiting times observed at a tipping bucket gauge conditional on the previous waiting time. The model is verified both with respect to average and extreme values and by testing it on urban drainage problems and it is concluded that the model appears to have captured to properties of rainfall well.
Bias introduced in rainfall risk assessment by a rain gauges network
Authors: Neppel L. , Desbordes M. , Masson J. M.
Published: May 2018

When large periods of observation are considered, the densest information are often a collection of the daily rain gauges network. As this information is scattered in space, the stochastic results and specially the rainfall risk assessment, are biased because of the rainfall events that are not ‘observed’ by the network. Rainfall risk can be assessed using a punctual approach with the estimation of regional return period of a punctual rainfall depth exceeding a given value, or using a spatial approach with the frequency analysis of the areas of isohyets defined at a given rain threshold τ. This last approach consists, for a given τ, in estimating the return period of isohyet areas. Using simulation, a method of unbiased rainfall risk assessment is proposed for the Languedoc-Roussillon region (France). It has been shown that the bias influence is negligible for the regional return periods of isohyet areas, for 24-hour and 48-hour duration, when compared to their confident limits. On the contrary the return periods of punctual rainfall depths above a given value are more sensitive: for values above 170 mm/24h and 270 mm/48h, the biased return periods could be up to 3 times overestimated.
Infrastructure configurations for wastewater treatment and reuse: a simulation based study of membrane bioreactors
Authors: Jeffrey P. , Seaton R. A. F. , Stephenson T. , Parsons S.
Published: May 2018

Recent research on advanced wastewater treatment methods and techniques has generated a new set of technologies developed for use at anything from the household to the city scale. However, one of the central issues in the application of new technologies is the relevant scale at which to design and implement physical systems. This contribution reports the design and use of a demand based simulation model to study issues of appropriate scale and connectivity for a wastewater reuse system. The particular case of membrane bioreactors as treatment units to supply sub-potable demand is considered in detail. Results identify optimum levels of system connectivity and size with regard to both the cost of distributing recycled water and savings in potable quality resources.
Calibration of tipping bucket rain gauges
Authors: Overgaard S. , El-Shaarawi A. H. , Arnbjerg-Nielsen K.
Published: May 2018

A tipping bucket rain gauge measures rain fall volumes with high resolution, thus enabling calculation of rain intensities. To ensure that the volume of one tipping is independent of the rain intensity a syphon is introduced. However, the syphon introduces problems with respect to both a time lag and problems when reconstructing the underlying rain intensities. This problem is studied in detail. The rain gauge in question is a RIMCO tipping bucket rain gauge, used by the Danish Water Pollution Control Committee (DWPCC). The rain gauge has been tested in the laboratory and in the field. The study shows, that it is possible to reduce the syphon volume to a level where the problems of the syphon are small and yet maintain the same accuracy with respect to volume registrations.
Systems view of integrated water quality monitoring within the requirements of the new national water policy in South Africa
Authors: Marjanovic P. , Miloradov M.
Published: May 2018

The new National water policy will change the way water quality is managed in South Africa. The paper considers the water policy and the repercussions it will have for water quality monitoring in South Africa. Using the systems approach the paper discusses an integrated water quality monitoring system for ambient water quality and point and non point sources of aquatic pollution. The proposed methodology makes possible continuos assessment of water quality in an efficient manner so as to support water quality management in South Africa.
Historical precipitation time series for applications in urban hydrology
Authors: Johann G. , Papadakis I. , Pfister A.
Published: May 2018

The quality of results of rainfall runoff modelling depends strongly on the hydrologic input data. In particular, for urban hydrology applications long-term rainfall series without gaps and of high quality and reliability are required in rainfall runoff and hydraulic simulation of the investigated drainage and receiving water system.

The presented study discusses a method for filling gaps in precipitation time series provided by the Emschergenossenschaft and Lippeverband (EG/LV) in north west Germany. Various time intervals based on deterministic and statistical approaches are investigated. Intervals between 5 and 120 min will be discussed in particular. Several neighbour stations of the EG/LV raingauge network are considered. On the basis of representative examples it is shown how the time intervals mentioned above influences the quality of the estimated gap-filling rainfall data.
Application of nuclear magnetic resonance imaging (MRI) to migration studies of oil-related residues in estuarine sediments (Tay Estuary)
Authors: Reeves A. D. , Chudek J. A.
Published: May 2018

The tendency for selected organic compounds to sorb to sediments has been investigated extensively. These studies, however, have not permitted the ‘observation’ or measurement of advection/diffusion processes and the breakdown of organics within sediments.

MRI is a multidimensional technique allowing the position of nuclei (most commonly protons) to be charted within a volume. We introduce MRI as a means of monitoring movement of oil within a series of estuarine sediments, thus offering a method of assessing the harming potential of oils in nearshore environments.

Results presented in terms of the % change of oil distribution within a sediment sample, show the great potential of MRI in studying protonated contaminants in sediments.
Limitations of sediment quality surveys: a case study of an urban watershed in British Columbia, Canada
Authors: McCallum D. W. , Hall K. J.
Published: May 2018

This case study of a 7200 ha. urban watershed illustrates the challenges involved in using sediment quality surveys to determine pollutant sources and trends. Trace metal and chlorinated hydrocarbon analyses were performed on sediment samples obtained from 33 stream, 24 street, and 1 lake (sediment core) locations. The stream and street sediment survey was initially conducted in 1973 and repeated in 1993. Consistent results across all sediment media indicate significant reductions in Pb, PCB, and DDT levels have occurred since the 1970's as a result of source controls. While streambed results indicate Hg and Mn levels have increased significantly since 1973, neither a spatial analysis of streambed results or a comparison to street concentrations indicate a source for the increase. A more detailed geo-chemical analysis and/or atmospheric contaminant survey may provide more conclusive source information.
Carbon to chlorophyll-a ratio in modeling long-term eutrophication phenomena
Authors: Jin Haisheng , Egashira Shinji , Chau K. W.
Published: May 2018

Carbon to chlorophyll-a ratio (CCHL) is formulated based on the assumption that adaptive changes in carbon to chlorophyll occur so as to maximize the specific growth rate for ambient conditions, including solar radiation and water temperature. With the dynamic CCHL, an unsteady two-layered, two-dimensional eutrophication numerical model for density stratified coastal waters has been developed. Saturated light intensity (IS) is determined as weighted average of the light intensity for previous three days to incorporate light acclimation by phytoplankton. The bottom water anoxic condition during summer in Tolo Harbour, Hong Kong is successfully reproduced by the present method. Otherwise, the simulation with a constant CCHL gave a wrong result.
River Water Quality Modelling: III. Future of the Art
Authors: Somlyódy L. , Henze M. , Koncsos L. , Rauch W. , Reichert P. , Shanahan P. , Vanrolleghem P.
Published: May 2018

This paper is the third of a three-part series summarizing the background to and objectives of the activity of the IAWQ Task Group on River Water Quality Modelling (RWQM). On the basis of the two other papers and a comparison between the best known state of the art river model, QUAL2E, and the IAWQ Activated Sludge Model (ASM) No. 1, the Task Group proposes to develop improved conversion models for inclusion in a river water quality model. The model should describe the cycling of oxygen, nitrogen, and phosphorus in both water and sediment, and should be compatible with the ASM to support the development of integrated emission reduction strategies. The model should be particularly well suited to handle problems characterized by significant temporal and spatial influences (e.g. CSOs and NPSs). It should serve for research, education, improved communication, knowledge transfer, regulatory applications such as catchment planning, and improved data collection. Anticipated results of the Task Group effort include: (i) standardized conversion sub-models; (ii) a decision support tool to guide model construction and usage; and (iii) case study applications. The model development, which is not intended to result in a software product, is intended to be an open-ended and flexible process to encourage the participation of interested professionals.
Environmental engineering education at the millenium: an integrated approach
Authors: Bhamidimarri Rao , Butler Ken
Published: May 2018

The rapid economic growth initiated by the Industrial Revolution has occurred within a paradigm of exploitation of nature for the benefit of humanity. However, a rising tide of ecological disasters has convinced society that human well-being is intimately linked with ecological well-being, and that society's long term future is dependent upon an ethic of sustainability. Sustainability requires more than end of pipe solutions, and environmental problems are invariably laden with social and ethical dimensions. The environmental engineer needs skills of integration, communication, and conceptualisation in addition to a traditional engineering background. Such a complex knowledge and skill mix is best promoted by a specially designed program. An environmental engineering degree program must impart the required knowledge and skill base and promote the intellectual versatility to develop appropriate technical solutions to environmental problems within existing ethical, ecological and legal frameworks.
Evaluation of the impact of different sewage treatment processes on shellfishery pollution using a geographic information system (GIS)
Authors: Lee R. J. , Glover R. J. O.
Published: May 2018

Filter-feeding bivalve molluscs such as oysters, clams, mussels and cockles can concentrate microorganisms, including pathogens, from contaminated waters. Consumption of shellfish contaminated by human sewage may then result in illness such as viral gastroenteritis or infectious hepatitis. Under the EC Shellfish Hygiene Directive (91/492/EEC) controls are placed on the commercial harvesting of shellfish from such areas in order to reduce the risk of infection. Reduction of contamination should result in a reduction of the risk of illness and should also increase the commercial potential of harvesting areas. Predicting the effect of change in sewage treatment type on the extent of contamination of nearby shellfisheries is more difficult than predicting the effect on water quality. A geographic information system (GIS) was used to relate microbiological data obtained from shellfish monitoring to the type and size of sewage discharges in the vicinity of harvesting areas. Data extracted using the GIS were further analysed using a statistical software package. The generic relationships obtained using this method were tested against shellfish monitoring data obtained from the vicinity of individual sewage improvement schemes. The results are discussed in relation to the most appropriate policy for capital investment on discharge schemes impacting molluscan shellfisheries.
Intelligent control system based on blackboard concept for wastewater treatment processes
Authors: Ohtsuki T. , Kawazoe T. , Masui T.
Published: May 2018

An intelligent control system for wastewater treatment processes has been developed and applied to fullscale, high-rate, activated sludge process control. In this control system, multiple software agents that model the target system using their own modeling method collaborate by using data stored in an abstracted database named ‘blackboard’. The software agents, which are called ‘expert modules’, include a fuzzy expert system, a fuzzy controller, a theoretical activated sludge model, and evaluators of raw data acquired by various online sensors including a respirometer. In this paper, the difficulties of controlling an activated sludge system by using a single conventional strategy are briefly reviewed, then our approach to overcome these difficulties by using multiple modeling methods in the framework of an ‘intelligent control system’ is proposed. Case studies of applications to a high-rate activated sludge process that treats BOD and nitrogen of human excrement are also presented.
Helminth egg concentration in wastewater: influence of rainwater
Authors: Capizzi S. , Schwartzbrod J.
Published: May 2018

Rainwater runoff in urban areas removes helminth eggs into the sewer system where they are carried to the treatment plant by the rainwater or remain in the sewer system until the next heavy rainfall. The concentration of parasite eggs varies according to the water flow rates in the urban system. Heavy rain cleans both the urban surfaces and the drains. In particular, it removes particles less than 100 μm diameter which are laid down in the pipes. These particles are present in high concentration in storm water whenever heavy rain is preceded by days with low rainfall. Variations in parasite concentration are thus dependent upon the precipitation of the previous days making it difficult to predict the concentrations of parasites in raw wastewater at input to the treatment plant. Many factors may affect parasite concentration including the presence of sediment in the sewer system, the intensity of rainfall and the amount of rain that has fallen on previous days. Parasites account for only a small proportion of the mass of suspended solids in rainwater. However, they represent a major health hazard in case of overflow of storm water associated with wastewater into the natural environment.
Advanced wastewater disinfection technologies: short and long term efficiency
Authors: Lazarova V. , Janex M. L. , Fiksdal L. , Oberg C. , Barcina I. , Pommepuy M.
Published: May 2018

Advanced disinfection processes (peracetic acid, UV irradiation and ozonation) have been tested and evaluated through bench and pilot scale studies. 3 log removals of total coliforms, faecal coliforms and faecal streptococci were achieved by 10mg/L peracetic acid at a 10min contact time, by UV radiation at 35mW.s/cm2 and by ozone at 5mg/L for 10min contact time. Higher doses are required for virus removal by UV and PAA and especially for highly resistant viruses such as F-specific bacteriophage MS2. Ozonation has the advantage of having a strong effect on all types of bacteriophages and protozoa cysts even when low treatment doses and short contact times are applied. The results of this study demonstrated that evaluation of disinfection efficiency of ozone, UV and PAA depends on the criteria and methods employed. Standard method (plate count) results showed an important disinfection effect on culturability, while results from non-standard methods (respiratory activity and β-galactosidase activity assay) indicated less reduction of viable cells. Moreover, the results confirm that disinfectants act on bacteria in different ways. It has been clearly demonstrated that b-galactosidase activity is affected by PAA while UV treatment has no or very limited effect on the enzyme activity. Even without sunlight reactivation, bacterial regrowth in seawater was observed after disinfection of sewage effluents. This study also shows that the biodegradability of sewage effluent for an E coli strain was affected differently by the oxidative disinfectants ozone and PAA. Biodegradability should therefore be considered when evaluating the total disinfection efficiency.
Time dose reciprocity in UV disinfection of water
Authors: Sommer R. , Haider T. , Cabaj A. , Pribil W. , Lhotsky M.
Published: May 2018

The microbicidal effect of UV light depends on the dose in both, disinfection processes and natural inactivation by the sunlight in surface water. Deviations of the time dose reciprocity are well known from chemical water disinfection whereas no data are available about this effect in UV inactivation in water. In a previous study we found that the UV inactivation behaviour of yeast strains does not follow the time dose reciprocity, insofar that longer exposure led to higher reduction of cultivable cells. In contrast, an earlier study about E coli B/r claimed a higher inactivation with single exposure compared with fractionated UV irradiation. To investigate this question we selected water-relevant microorganisms and studied their UV inactivation behaviour (253.7nm) by means of a specially designed UV irradiation apparatus (a) under standard irradiation conditions (2W/m2) and (b) with three levels of UV dose rate (2, 0.2 and 0.02W/m2). The test organisms were (i) three E coli strains (ATCC 25922, ATCC 11229 and an isolate from sewage) representing the routinely used faecal indicator, (ii) three bacterial viruses (MS2, ϕX174 and B40-8) proposed as indicators for viral contamination in water and (iii) spores of Bacillus subtilis because of their use as a biodosimeter in prototype testing of commercial UV plants for drinking water disinfection. We found, under standard inactivation conditions, that the E coli strains and phage ϕX174 are most UV susceptible, followed by B40-8 and finally MS2 and bacterial spores. The dose protraction experiments revealed for the E coli strains a higher inactivation with high dose rates compared to low dose rates at the same UV doses (difference of about 1 log10 at 80-100J/m2). The other test organisms did not deviate from the time dose reciprocity in the proven range of dose.
Evidence that tropical soil environment can support the growth of Escherichia coli
Authors: Byappanahalli M. N , Fujioka R. S.
Published: May 2018

Concentrations of faecal coliforms and Escherichia coli in environmental waters have historically been used to establish recreational water quality standards. When these bacteria are used as indices of water quality, it is assumed that there are no significant environmental sources of these bacteria which are unrelated to direct faecal contamination. However, we have previously reported that in tropical island environments such as in Hawaii, these faecal indicators are consistently found at high concentrations in all streams and the source of these faecal bacteria is the soil. To become so well established in soil we hypothesized that these faecal bacteria must have the ability to multiply in the natural soil environment at ambient temperature (23–25°C). Three lines of evidence support this hypothesis: (1) E. coli was shown to grow on 10% soil extract agar, (2) populations of faecal coliforms and E. coli from sewage were shown to immediately increase by about three logs when simple nutrients (glucose and salts) were added to natural soil and (3) faecal coliforms and E. coli increased by two logs within 24 h when a minimal amount of sewage was added to cobalt-irradiated soil. These results indicate that tropical soil environments provide sufficient means to support the growth of faecal coliforms and E. coli. However, under natural soil conditions, indigenous soil microorganisms are much more efficient in obtaining nutrients and we hypothesize that faecal bacteria grow sporadically in response to available nutrients.
Sludge storage for countering nitrogen shock loads and toxicity incidents
Authors: Yuan Z. , Bogaert H. , Vansteenkiste G. , Verstraete W.
Published: May 2018

Spare nitrification capacity is usually needed for a nitrifying activated sludge plant to counter nitrogen shock loads and/or toxicity incidents. The traditional way to provide this capacity is to apply a sludge retention time which is much longer than what needed to obtain a stable nitrification, resulting in over designed plants. Another approach, which is investigated in this paper, is to store the spare biomass in a separate sludge storage tank and return it to the main stream process when a shock nitrogen load or a toxicity incident occurs. Model based analysis reveals the unique feature of the scheme: different particulate components in the sludge have a different retention time, and more specifically, active biomass stays longer in the plant than inert solids. This results in that a plant with a storage tank can have the same amount of active biomass as a traditional plant but less sludge, opening the potential of reducing the volume of the plant. Analysis shows that a plant with a sludge storage tank can be about twenty percent smaller than a traditional plant that has the same treatment capability. Analysis is verified by simulation studies.
Model-based control of the substrate concentration in an aeration basin using the wastewater level
Authors: Czeczot Jacek
Published: May 2018

This paper deals with the minimal-cost control of the modified activated sludge process with varying level of wastewater in the aerator tank. The model-based adaptive controller of the effluent substrate concentration, basing on the substrate consumption rate and manipulating the effluent flow rate outcoming from the aerator tank, is proposed and its performance is compared with conventional PI controller and open loop behavior. Since the substrate consumption rate is not measurable on-line, the estimation procedure on the basis of the least-square method is suggested. Finally, it is proved that cooperation of the DO concentration controller with the adaptive controller of the effluent substrate concentration allows the process to be operated at minimum costs (low consumption of aeration energy).
A mathematical filter backwash model
Authors: Hall D. , Fitzpatrick C. S. B.
Published: May 2018

A mathematical model for deposit detachment and removal during the backwash of rapid gravity filters has been derived for a fluidising water wash. The model consists of two parts; part 1 determines the volume of deposit dislodged into suspension at any instant, and part 2 determines the change in concentration emerging from the filter bed at any stage during the backwash. Initial conditions for the backwash model are determined from a filtration model.
Molecular biological methods to detect “Microthrix parvicella” and to determine its abundance in activated sludge
Authors: Bradford Debbie , Christensson Camilla , Jakab Nicole , Blackall Linda L.
Published: May 2018

Molecular biological methods were evaluated in attempts to detect and quantitate levels of “Microthrix parvicella” in activated sludges. Approximately 66% of the 23S rRNA gene sequence of a strain (Ben43) of the Gram positive bulking and foaming organism “Microthrix parvicella” was determined, while a lesser amount was determined for “M. parvicella” strain RN1. The high mol%G+C Gram positive bacteria (HGCGPBs) possess two powerfully diagnostic regions in the 23S rDNA and these were investigated in both strains. Firstly, the 18 nucleotide HGCGPB probe sequence (HGC69a) varied in at least two nucleotides with the sequence from both strains of “M. parvicella”. Secondly, an approximately 100 nucleotide stable insert between helices 54 and 55 in the 23S rRNA of HGCGPBs was discovered to be present in “M. parvicella”, but in both strains it was unique in length (79 nucleotides) and sequence. The region of the 23S rDNA with the stable insert was exploited to develop a polymerase chain reaction assay in which amplicons from “M. parvicella” were larger than those from nonHGCGPBs (i.e. all Bacteria except the HGCGPBs), and smaller than those from HGCGPBs. This assay was evaluated with DNAs extracted from activated sludges but although “M. parvicella” was morphologically identified, and was a dominant filament in at least one of the samples, no “M. parvicella” specific sized amplicons could be recovered from it. Amplicons of sizes generated by nonHGCGPBs and HGCGPBs were routinely produced in the stable insert PCR with DNAs from activated sludges where the highest yield was of amplicons from nonHGCGPBs.

A second series of experiments were undertaken with the objective of evaluating the use of a non-radioactive hybridization method, based on extraction of bacterial RNA, for quantifying “M. parvicella” in activated sludge samples. Total nucleic acids were extracted from activated sludge samples and immobilized on nylon membranes. Probing with 16S rRNA-directed DIG-labelled oligonucleotide probes, detection of chemiluminescent signals on membranes and densitometry allowed hybridization signals to be quantified. The relationship between the amount of nucleic acid hybridized and the hybridization signal intensity observed was found to be linear over a specified range of signal intensities. A range of activated sludge samples were analysed for “M. parvicella” and variations in levels could be distinguished.