bluuebunny/crossref_metadata_2025 huggingface dataset:
Digestion of municipal sludge by anaerobic sequencing batch reactor
Authors: Chang Duk , Hur Joon Moo , Chung Tai Hak
Published: May 2018

Laboratory experiments were conducted to investigate the performance of the anaerobic sequencing batch reactor (ASBR) for digestion of a municipal sludge. The reactors were operated at an HRT of 10 days with an equivalent loading rate of 0.8-1.5 g VS 1−1 d−1 at 35°C. Solids were accumulated rapidly in the ASBR during start-up period. Flotation thickening occurred in the ASBRs, and its efficiency was comparable to that of additional thickening of the completely mixed control reactor. Solids concentrations in the ASBRs were 2.6 times higher than that in the control. The dehydrogenase activity had a strong correlation with the solids concentration. The ASBRs with 3- and 4-day cycle showed almost identical high digestion performances without adverse effect on digestion stability. The organics removals based on subnatant of the ASBRs were consistently above 90%. Remarkable increase in equivalent gas production of 52% was observed at the ASBRs compared with the control though the control and ASBRs showed similar effluent quality. Thus, digestion of a municipal sludge was possible using the ASBR in spite of high concentration of settleable solids in the sludge.
Safeguards against pathogens in danish biogas plants
Authors: Bendixen H. J.
Published: May 2018

A veterinary research project is organized in Danish biogas plants (BGP) to study the ‘pathogen reducing effect’ (PRE) of the treatment in digestion tanks and sanitation tanks, and the ‘pathogen reducing capacity’ (PRC) of the entire plant. In addition the feasibility of measures to prevent spread of animal and human pathogens is studied. Ten BGPs are currently in operation closely related to the agricultural sector. Slurry constitutes 80-85% of the biomass treated, various industrial by-products and urban waste the rest. Rules have been issued to prevent spread of pathogens between animal holdings during the collection, transport and distribution of biomass. Criteria for the treatment in digestion tanks and sanitation tanks have been introduced to ensure removal of pathogens. Official regulations on hygienic measures and conditions for treatment of biomass which is spread on agricultural land are included in Danish legislation. An indicator method based on faecal enterococci (streptococci) (FE) has proven its practical value for checking the functions, detecting leakage or wrong management, and for evaluating the PRE at temperatures below 55 to 60°C. Studies of the persistence of pathogens in biomass at higher temperatures are in progress. The role of the competent central, regional and local authorities for approval, regular supervision and inspection of the BGPs is described. The Veterinary Service takes action when outbreaks of serious diseases occur.
Upgrading of rotating biological contactor (RBC) systems to achieve higher effluent quality, including biological nutrient enrichment and reduction techniques
Authors: Neu Kenneth E.
Published: May 2018

This paper explores RBC system mechanical and process upgrade alternatives. There may be multiple upgrade opportunities. Some process upgrades are proprietary while others are not. Mechanical and process upgrades describe many positive advantages for existing plants that need to be upgraded to meet more stringent effluent limits or for increased capacity.

A case study was conducted to evaluate a process upgrade. Simple physical manipulation of existing process parameters within the treatment plant and the addition of a new process feature to facilitate secondary sludge recycle to the RBCs showed increased organic capacity and improvement in effluent quality. Also, a significant reduction in nutrients (N & P) without the use of chemicals and a significant reduction in RBC shaft weight were other benefits. The easily settleable solids contained at least a doubling of the phosphorus content and dewatered well without chemical supplementation.
High rate aerated biofilters for plant upgrading
Authors: Rogalla F. , Lamouche A. , Specht W. , Kleiber B.
Published: May 2018

Biocarbone aerated biofilters were developed more than ten years ago. Almost one hundred plants worldwide provide complete treatment in very short hydraulic retention time. This allows to construct compact plants in sensitive areas such as inner cities, sea or mountain resorts. The filters can be adapted to high effluent qualities expected by the European directive on wastewater treatment. Full oxidation of ammonia can be achieved in less than two hours. A plant for complete removal of nitrogen has been operated for more than a year in Denmark to meet Europe's most stringent effluent requirements by using an anoxic biofilter in series with the Biocarbone.

A new aerated biofilter, turning the Biocarbone principle upside down, is presented : a synthetic floating material allows enhanced performance, simplified backwash and a combination of anoxic and aerobic zones in one reactor. Effluent quality of less than 10 mg/l for all components (BOD, SS, TN) was demonstrated in a one-year long on-site test in Denmark and the first facility for 60 000 population equivalents is under startup. Full scale results of the upflow floating filter, Biostyr, are presented for nitrogen and phosphorus removal according to the European directive.
Upgrading of the Munich waste water treatment plants for denitrification in effluent filters
Authors: Eichinger J.
Published: May 2018

Munich has been studying denitrification in effluent filters, as has been practiced in the USA for over 15 years in a full scale demonstration, pilot- plant for over a year (October 1991 through October 1992). The results have been very encouraging; in spite of very low wastewater temperatures, a high degree of denitrification has been achieved very economically. Excellent BOD5 and COD effluents have been achieved. At the same time P-removal has improved. Nitrite has always been low. This was done at dry weather hydraulic loads averaging 4.4 m/hr with a daily peak of 6 m/hr and storm water maximums of 14.4 m/hr. Additional smaller scale, pilot studies were begun in May 1993, whose object is to optimize the technology under European conditions.
Anaerobic digestion of high-sulphate-content wastewater from the industrial production of citric acid
Authors: Colleran E. , Finnegan S. , O'Keeffe R. B.
Published: May 2018

The start-up and steady-state operation of a full-scale fixed bed digester treating citric acid production wastewater with an estimated COD/sulphate ratio of approximately 4 are described. Parallel studies at laboratory-scale with two reactors, one of which received the same high influent sulphate concentration as the full-scale plant, confirmed the finding that methanogenesis was not inhibited by the level of sulphate reduction shown to occur. After long-term operation on a high sulphate influent, the retained biomass in the laboratory and full-scale reactors displayed a very low specific methanogenic activity against propionate and butyrate. Since propionate and butyrate were barely detectable in the effluents at steady-state, their oxidation under high influent sulphate conditions may be completely or incompletely mediated by fatty-acid-utilising SRB.
Pilot-scale biological sulphate and nitrate removal utilizing producer gas as energy source
Authors: du Preez L. A. , Maree J. P.
Published: May 2018

The discharge of effluents rich in sulphate and nitrate is of increasing concern, as the former leads to mineralisation of surface water, and the latter is a plant nutrient. A process is described whereby sulphate is reduced to sulphide under anaerobic conditions with producer gas as substrate. Sulphide stripped off is then converted to elemental sulphur by reacting it with biologically produced iron(III). The study consisted of laboratory batch and continuous experiments, as well as pilot scale studies. Sulphate was reduced to sulphide at a rate of 1.2 g SO4 1−1 d−1 with H2/CO as substrate, and 2.4 g SO4 1−1 d−1 with only CO as substrate. Nitrate was converted to ammonia in the anaerobic reactor. Sulphide was removed from 2 000 mg 1−1 (as SO4) to less than 90 mg 1−1. The iron(II), produced after reduction of iron(III) with H2S, was oxidised biologically to iron(III). The volumetric reaction rate was 5.5 g Fe 1−1 d−1.
Application of anaerobic-uf membrane reactor for treatment of a wastewater containing high strength particulate organics
Authors: Harada Hideki , Momonoi Kiyoshi , Yamazaki Shinichi , Takizawa Satoshi
Published: May 2018

A cross-flow ultrafiltration (UF) membrane separation was applied to anaerobic process for treatment of a wastewater containing high proportion of particulate COD. A synthetic wastewater with the total strength of 5000 mg COD·1−1 consisting of soluble and particulate COD (cellulose) in the ratio of 1:1 was fed to the reactor. The reactor was operated for 190 days at two loading rates, i.e. 1.5 and 2.5 kg COD·m−3·d−1. More than 98% of COD removal was consistently achieved throughout the duration, and the system was furthermore likely to accommodate much higher loading. Although the permeate COD was always kept at less than 80 mg COD·1−1, soluble COD of reactor broth accumulated up to 1200 mg COD·1−1. The biomass concentration saturated around 15 000 mg ML VSS·1−1. There was no tendency for cellulose to accumulate in the reactor over the whole period, which constituted only 1-2% of the total solids retained in the reactor. The methanogenic activity of the sludge increased 3.4 times for H2/CO2 and 10 times for acetate after 40 days operation. Afterwards, however, a further cultivation caused declines to 50% of the respective peak values for both substrates, because of a low sludge loading. The methanogenic activity using cellulose as a test substrate also exhibited a similar tendency. The membrane permeate flux deteriorated significantly with the cultivation time, owing to the change in rheological properties of the reactor mixed liquor that had been caused not only by increment of MLSS but also by accumulation of soluble high molecular organics.
Use of a Tropical Basin Model to Assess the Importance of Urbanized Land Condition on the Increase of Flood Peak
Authors: Wong Tommy S W. , Chen Charng-Ning
Published: May 2018

Using the computer model of the Upper Bukit Timah Basin of Singapore, the effect of urbanized land condition on the flood peak increase due to urbanization has been assessed. The model results are presented in isopleths, which are lines of equal ratio of flood peak after and before urbanization. The degree of urbanization is expressed in terms of the percentage of area developed and the percentage of area channelized. By subjecting the Basin to the Singapore 2-year rainfall, the results show that the transformations from a forest to a developed land with 30% imperviousness may cause a three-fold increase in the flood peak. If the imperviousness of the developed land were to increase to 100%, the flood peak increase could be as high as five times. Evaluation of flood peak increase is therefore highly dependent on the degree of imperviousness of the urbanized land.
Statistical Water Quality Modelling for Urban Runoff Control Planning
Authors: Li J. Y. , Adams B. J.
Published: May 2018

Increased concern for the impact of urban runoff on receiving water quality makes acute the need to develop runoff quality control models for the various stages of urban runoff control planning. Analytical probabilistic models, which compare favourably with the STORM simulation model, have been derived to predict the long-term pollution control performance of storage-treatment systems from rainfall statistics. With knowledge of the cost functions of storage-treatment systems, the developed cost optimization precedure can be used to determine the least-cost combination of storage and treatment systems which can achieve various levels of quality control. This information is useful for specification of design performance and subsequent design level analyses of control systems.
Causal Stochastic Simulation of Dissolved Oxygen Depletion in Rivers Receiving Combined Sewer Overflows
Authors: Schaarup-Jensen K. , Hvitved-Jacobsen T.
Published: May 2018

A method for stochastic analysis of the effect of combined sewer overflows on the dissolved oxygen concentration in receiving rivers is developed. The method is based on repeated operation of the water quality model MOUSE-DOSMO. Each operation of this model covers a series of overflow events calculated by the MOUSE-SAMBA runoff model based on a historical rainfall record. For each event selected input data and model parameters in both models are drawn from fundamental statistical distributions by a simple Monte Carlo method. These data and parameters vary from event to event in each series. Each operation of the MOUSE-DOSMO model results in an extreme event statistics on dissolved oxygen minimum values -while repeated operation of the model yields extreme event percentiles by means of which a probability-based assessment of the model result may be performed.
A Stochastic Pollutant Load Model for the Design of Stormwater Detention Facilities
Authors: Segarra-García R. , Loganathan G. V.
Published: May 2018

A set of equations dependent on specified pollutant trap efficiency for computing storage capacity-treatment rate combinations of a stormwater detention system is provided. The equations are expressed in terms of the statistics of the runoff event variables: mean depth, duration, and interevent time. The hydrologic random variables are assumed to be independent and exponentially distributed. A mass balance equation is derived for the detention unit based on a first-order pollutant load model. With the aid of statistical derived distribution techniques, an expression for the expected pollutant washoff load is derived, which is further used to develop analytical storage/treatment isoquants for specified levels of pollutant trap efficiency. The isoquants are defined in terms of the design storage capacity, the treatment rate, the pollutant trap efficiency, and the runoff process statistics. A further extension of the model allows the derivation of equations for the estimation of the settling efficiency of pollutants of stored stormwater. The estimators for storage capacity-treatment rate are obtained from closed form expressions that, in addition, yield lower and upper bound estimates of the design variables. Illustrative examples using data for catchments in Minneapolis and Denver are provided.
Sedimentation in Storage Tank Structures
Authors: Stovin Virginia R. , Saul Adrian J.
Published: May 2018

Although storage tanks provide an effective means of reducing the magnitude and frequency of combined sewer overflow discharges, and thereby of alleviating urban watercourse pollution, poorly designed storage structures frequently suffer from maintenance problems arising from sedimentation. The development of design guidelines that optimise the self-cleansing operation of storage structures is clearly a priority for urban drainage research.

This paper describes a system that has been developed to study sediment deposition in laboratory model-scale storage structures. The patterns of deposition resulting from a selection of flow regimes are described, and the need for time-varying and time series storm tests is highlighted. Sedimentation patterns are shown to predominantly depend on the flow field, and the critical bed shear stresses for deposition and erosion in the model situation are identified. Hence, the potential application of numerical models to the design problem is discussed.
The Prediction of Combined Sewer Overflow Performance from Models – A Case Study
Authors: Hedges Peter D.
Published: May 2018

Hydrodynamic separators have been employed as combined sewer overflows (CSOs) in the UK since the early 1960s. Since little was known of their operating characteristics, Severn Trent Water Authority contracted Aston University to monitor the performance of a separator constructed during 1986-87 at James Bridge, Walsall, UK. Unfortunately only three overflow events were fully documented during the monitoring period, which was particularly dry. One separator was therefore artificially charged by pumping from the adjacent river to simulate storm flow conditions. A model study was not included in the original proposal, but one was established to complement the main programme since the characteristics of hydrodynamic separators were poorly understood.

The arrangement of the field site is described, and the results from the monitored storm events, pump tests and model studies are summarised. Characteristics derived from the model study are combined with sewage settling velocity grading curves to predict the performance of the prototype hydrodynamic separator for one of the observed storm events. Given the limitations inherent in the sewage data used, a comparison of the predicted and observed separator efficiencies demonstrates the potential of this approach for the design and selection of CSOs for specific locations.
A Model to Assess the Performance of Controlled Urban Drainage Systems
Authors: Nelen Fons
Published: May 2018

The LOCUS modelling package, which has been designed to assess the performance of an urban drainage system that is controlled in real time is presented. Besides the simulation of 'optimal' controlled systems, LOCUS offers the possibility to simulate local (or static) controlled systems as well (i.e. the present way of operation of most urban drainage systems). Since an identical system description is used in both cases, the difference between the results is only due to the way the system is operated and hence the effects of real time control can be quantified by comparing the results. The use of the model is illustrated by a simple example, which shows that it is worth investigating the potential of real time control before constructing extra storage in the system. For a small fictitious system with limited storage capacity at the downstream section it is shown that this potential is comparable to increasing the storage capacity by 1.5 mm at this particular section.
Selector Volume in Pulp and Paper Activated Sludge Wastewater Treatment Plants – Bench Scale and Pilot Plant Studies
Authors: Wessberg J. , Welander T. , Jönsson M.
Published: May 2018

Laboratory activated sludge reactors were operated on effluent wastewater from a kraft mill. Two of the three reactors were initially preceded with a “normal” size aerated selector, 2% of the total aerated volume, with unsatisfactory sludge volume index development. When the selectors were replaced by larger ones, 13% of the aerated volume, the sludge volume index could be kept below 50 ml/g for the selector processes while continuing to be higher and more unstable in the reference process.

A pilot plant, operated in situ on the same wastewater, showed a comparable improvement in sludge volume index when its selector, 7% of the total volume, was replaced by one that constituted 13% of the total volume, corresponding to a selector load of 3 g BOD / g VSS * d.

According to studies of the COD balance around one bench scale selector, the COD removal mechanism in the selector was respiration/assimilation rather than uptake/storage.
Biological aerated filters: assessment of the process based on 12 sewage treatment plants
Authors: Canler J. P. , Perret J. M.
Published: May 2018

Biological aerated filtration is a recent and intensive process which has been greatly developed over the last few years. It is a technology based on biological processes with certain advantages, in particular the absence of secondary clarifiers, the modular nature and the wide variety of treatment applications.

The monitoring of a dozen medium capacity (7,500 to 150,000 p.e.) plants designed to treat organic pollution, has enabled us to evaluate the process and its performance.

The results obtained show that at applied loads of less than 7 kg of COD, the effluent is of satisfactory quality (< 90 mg / 1 of COD) and that the process has a high efficiency to remove suspended solids. Numerous other aspects have been studied and the data collected confirm the potential of this process, which nevertheless requires a careful and regular system operation procedure.
Tertiary nitrification in aerated pilot biofilters
Authors: Tschui M. , Boller M. , Gujer W. , Eugster J. , Mäder C. , Stengel C.
Published: May 2018

Three different types of internally aerated pilot scale biofilters were operated as tertiary nitrification systems. Long-term performance of the three aerated biofilters was tested under various operating conditions. The maximum volumetric nitrification rates under non NH4-limiting conditions for the three aerated biofilter systems were investigated. Based on measured temperature dependencies, an exponential relationship was established enabling the prediction of the nitrification rates at desired temperatures. Based on a temperature of 10°C, the results allow a comparison between the surface and volume specific nitrification rates in the tested biofilters as a function of the NH4 effluent concentration.

As shown by experiments, nitrification performance depends on water as well as air velocities in the filter. Higher velocities of both air and water increase the nitrification rate. However, they also increase the head loss and thus decrease the filter run time. Therefore, the optimal operating conditions depend also on the filter media and the required effluent quality.

Compared to fully O2-limiting operating conditions, nitrification performance during a period under partially NH4-limiting conditions clearly decreased in all tested biofilters.
Hydrodynamics and kinetics in biofilm systems - recent advances and new problems
Authors: Lewandowski Z. , Stoodley P. , Altobelli S. , Fukushima E.
Published: May 2018

Application of microelectrode techniques, Nuclear Magnetic Resonance Imaging, and Confocal Laser Microscopy permitted analysis of hydrodynamics, kinetics, and internal structure in biofilm systems. The commonly accepted concept of one dimensional diffusion through a three compartment model (bulk solution, biofilm, and substratum) requires revision based on recent progress in understanding the internal structures of biofilms. Biofilms seem to form three dimensional porous structures with a network of interstitial voids filled with water, forming a network of channels connected with each other and with the biofilm surface. The basic unit of this structure appears to be a bacterial cluster (sometimes called microcolony).
Population dynamics of methanogenic biofilm consortium during a start-up period of anaerobic fluidized bed reactor
Authors: Araki N. , Harada H.
Published: May 2018

The changes in physical properties and microbial activities were investigated during initial biofilm formation in lab-scale anaerobic fluidized bed reactors. Four different upflow velocities, i.e., 4, 7, 14 and 25 m·hr−1 were applied to four respective reactors of an equal size. The upflow velocities caused a prominent difference in the pattern of initial biofilm formation. The biofilm thickness attained eventually approximately 100 μm after 100 days of operation, independent of upflow velocity. On the contrary the biofilm density varied from 4.4 to 24.1 mg-VSS·cm−3 with an increase in the upflow velocity imposed. The activity of acetoclastic methane production increased remarkably 15 to 30 fold of seed sludge, regardless of upflow velocity. Microbial activities with respect to acetate production, H2-utilizing methanogenesis and acetate-utilizing methanogenesis increased finally up to 3-4 times as large as those of suspended grown sludge in a chemostat.
Fluidized bed reactor operation for groundwater denitrification
Authors: Green M. , Shnitzer M. , Tarre S. , Bogdan B. , Shelef G. , Sorden C. J.
Published: May 2018

Groundwater denitrification was carried out in a laboratory scale fluidized bed reactor using sand particles as the biomass carrier. This paper is concentrated on the fluidized bed reactor operation at very high nitrate loading rates (between 30 to 100 kg.NO3/m3 reactor/day) with corresponding short retention times (5 to 1.5 minutes). The effects of nitrate loading rate on nitrate and nitrite removal, as well as on reactor biomass profiles and biofilm characteristics, are presented in this article. The results of the present study indicate that this type of reactor can operate efficiently at retention times shorter than 3 minutes and at nitrate loading rates higher than 70 kg.NO3/m3/day. However, this system requires careful control of the biofilm thickness to achieve a reliable reactor operation.
Numerical modeling of a biofilm-electrode reactor used for enhanced denitrification
Authors: Flora J. R. V. , Suidan M. T. , Islam S. , Biswas P. , Sakakibara Y.
Published: May 2018

The enhancement of biological denitrification using a biofilm-electrode reactor (BER) is demonstrated. Removal efficiencies greater than 98% can be achieved. At electric currents in excess of 20 mA, the rate of denitrification within the BER is reduced due to hydrogen inhibition. A detailed steady-state biofilm model is developed taking into account hydrogen inhibition kinetics, the diffusion of neutral and ionic species, the effects of the applied current on the diffusion of ions, gas production within the biofilm, and the presence of a phosphate buffer and a mass transfer boundary layer. The biofilm model is coupled to a model of a completely stirred tank reactor (CSTR). The models are in excellent agreement with the experimental results when the applied electric current is between 0 and 20 mA. The results of the reactor model qualitatively predict the performance of the BER at currents greater than 20 mA using a hydrogen inhibition constant of 10−4 M.
Urban stormwater: the analysis of the failure of the alternative techniques and the management of quality
Authors: Alfakih E. , Barraud S. , Azzout Y. , Chocat B.
Published: May 2018

The implementation of alternative techniques in urban stormwater management is a difficult problem in terms of choice, design, construction, and operating. We applied a quality management approach to try and have a better understanding of these techniques. The quality of an alternative technique in urban stormwater management is defined; the factors that lead to failures were identified and analysed. In order to reduce these factors, tools were developed, and measures that allow the achievement of the necessary standard of quality are suggested. In this article, all the illustrations refer to the porous pavement technique.
An alternative road construction for stormwater management in cold climates
Authors: Stenmark Christer
Published: May 2018

A field study of an infiltration and detention facility in northern Sweden is presented. Streets in a housing area were reconstructed to increase the permeable area. Permeable asphalt was used covering a coarse fill material and swales (ditches) were constructed along both sides of the streets. The project will include studies of the water balance during different seasons, frost heave and frost penetration of the streets and the stormwater quality. Due to the reduced infiltration capacity during snowmelt periods, detailed studies will be performed on components of the facility that are important for the disposal of meltwater. Some initial tests of the infiltration capacity of permeable asphalt in cold temperatures indicated sufficient capacity during snowmelt periods.
Review of hydrodynamic separator-regulator efficiencies for practical application
Authors: Hübner Martin , Geiger Wolfgang F.
Published: May 2018

Different approaches to assess hydrodynamic separator performance are presented. These approaches are applied to the same data, evaluated at both steady state and at unsteady state conditions. It is shown that the overflow and baseflow concentration of particles at steady state conditions is increasing with increasing hydraulic load under constant inflow concentration. The different qualitative approaches allow a very contrary interpretation. Their value increases, decreases or has a maximum over the varied flow conditions. Furthermore it is shown that none of the presented approaches can accurately describe hydrodynamic separator performance at unsteady state conditions. Finally a set of two approaches is presented which is able to describe the quantitative and qualitative performance of a hydrodynamic separator and also takes unsteady state conditions into account.
Biodegradation rates of aromatic contaminants in biofilm reactors
Authors: Arcangeli Jean-Pierre , Arvin Erik
Published: May 2018

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.
Optimized lamellae settling for urban stormwater waste
Authors: Delporte C. , Pujol R. , Vion P.
Published: May 2018

Lamellae sedimentation is an efficient and compact solution for handling high stormwater influx at wastewater treatment plants during rainy periods. This paper presents and comments on the results obtained at several different sites using specially adapted lamellae settlers.

Surface hydraulic loads above 100 m3/m2.h have been reached using optimized doses of chemical reagents.

One key advantage of the reactor is that start-up is practically instantaneous; this means that efficient treatment is obtained right from the start of the high flow period.
Experimental and conceptual studies on mass transport in biofilms
Authors: Lewandowski Z. , Stoodley P. , Altobelli S.
Published: May 2018

It is demonstrated that the flow velocity distributions in a flat plate reactor with and without biofilm are considerably different. Flow velocity profiles perpendicular to the channel wall indicate water movement in the space occupied by the biofilm. The flow velocity does not reach zero at the biofilm surface. Water flows through the pores in the biofilm causing convective mass transport. Longitudinal profiles of the flow velocity indicate that the presence of the biofilm disturbs the flow, which increases the entry length required for fully developed viscous flow to be established. Recently it has been shown that biofilms consist of cell clusters separated by interstitial voids. This newly proposed concept of biofilm structure helps to explain these experimental observations. However, the hydrodynamics and mass transport in biofilm systems appear to be more complex than previously assumed.
Cometabolism in biofilm reactors
Authors: Speitel Gerald E. , Segar Robert L.
Published: May 2018

Aerobic cometabolism of chlorinated aliphatic solvents in biofilm reactors is a potential treatment technology for contaminated water and air streams. This research investigated cometabolism by pure and mixed cultures of methanotrophs and mixed cultures of phenol-degrading bacteria. Initial experiments with continuous-flow, packed-bed bioreactors proved unsuccessful; therefore, the major focus of the work was on sequencing biofilm reactors, which cycle between two modes of operation, degradation of chlorinated solvents and rejuvenation of the microbial population. Particular success was obtained with a mixed culture of phenol degraders in the treatment of chlorinated ethenes (e.g., trichloroethylene - TCE). Under the best operating conditions, 90% removal of TCE occurred at a 14-minute packed-bed hydraulic residence time. The bioreactors required only two, 1.5 h biomass rejuvenation periods per day to sustain this removal. Experiments with Methylosinus trichosporium OB3b were less successful because of the organism's slow growth rate, relatively poor ability to attach to surfaces, and its inability to successfully compete with other methanotrophs in the bioreactor environment. Overall, however, the research demonstrated the potential attractiveness of sequencing biofilm reactors in treating water contaminated with chlorinated solvents.
A multi-source approach to hydrologic parameter estimation in urban basins
Authors: Campana Néstor A. , Mendiondo Eduardo M. , Tucci Carlos E. M.
Published: May 2018

A procedure for estimating hydrological parameters is presented which combines a) remote sensing and GIS techniques with b) data extracted from site visits to city districts; the estimate so obtained is compared with estimates from rainfall data. It is developed in urban sub-basins of Dilúvio Basin in the metropolitan region of Porto Alegre, Brazil. A Fuzzy Algorithm which performs within sub-pixel level is used. Cover classes studied are: highly and slightly impervious, bare ground, grassed open space, and forest. A soil thematic map is determined based on pedological studies. A final distributed thematic map of potential runoff is obtained by superimposing previous data. It is compared with lumped runoff potential from rainfall events in sub-basins. These broad multi-source data hold basic information to develop an alternative strategy for hydrologic studies in urban basins.
Evaluation of hydrodynamic characteristics of the Bosphorus regarding the performance of the marine outfall systems
Authors: Akyarli Adnan , Arisoy Yalçin
Published: May 2018

Considering strong interrelations between hydrodynamic features of the Bosphorus and the tube-tunnel crossing which may affect the performance of marine outfall systems, the Institute of Marine Science and Technology (IMST) conducted a comprehensive meteo-oceanographic data acquisition campaign to collect information both for the reliable design of marine outfall systems and for the environmental impact assessment (EIA) of the railroad tunnel, on the joint request of the owners of the projects.

The main objectives of this paper are to outline the results of the EIA, and also to discuss the newly adopted plan which proposes to divert the sewage collected in the Kadìköy drainage area to Riva, located along the Black Sea. Recent evaluations by the authors on the blocking of lower layer flow, and findings presented on the mixing along the Bosphorus, have been included as scientific evidences in this discussion.
The dynamic behaviour of nitrifying Activated sludge systems influenced by inhibiting wastewater compounds
Authors: Nowak O. , Svardal K. , Schweighofer P.
Published: May 2018

More or less severe nitrification inhibition was observed in several pilot and full-scale activated sludge plants treating industrial wastewaters. In order to control the treatment process under inhibiting conditions, extended nitrification models have been developed on base of the ‘Activated sludge model No. 1’. In the case of temperatures between 25 and 30°C, the nitrification process has been expressed as a two-step reaction with nitrite as intermediate. Model elements for competitive and non-competitive inhibition as well as for biodegradation of the inhibitor were added, if required. The dynamic behaviour of the investigated activated sludge systems indicates that there are biodegradable non-competitive inhibitors. Operational as well as simulation results show that nitrifying activated sludge plants may become acclimatized to inhibitory compounds but have to be protected from peak loads of both nitrogen and inhibitory compounds.
Statistical identification of monod-kinetic parameters from on-line measurements
Authors: Carstensen Jacob , Harremoës Poul , Madsen Henrik
Published: May 2018

Time series analysis of on-line monitored ammonia and nitrate concentrations from full-scale wastewater treatment plants operated according to an alternating scheme makes the identification of Monod-kinetic expressions possible. The models presented in the present context only include kinetic parameters which have shown to be significant in a statistical sense. Estimates of kinetic parameters for the nitrification and denitrification processes are obtained by applying these models to the time series of ammonia and nitrate concentrations. In this paper, the concept of statistical identification which depends on the two conditions of theoretical and practical identification, is described. Experiences from estimating time series models of the nitrification and denitrification processes with data from two wastewater treatment plants are discussed. It appears that the dynamic of the biological processes on a full-scale plant is strongly varying. The proposed models are suitable for on-line control, because the states of the plant are continuously updated as new information from the on-line sensors becomes available.
Environmental model studies for the Istanbul master plan. Part I: hydrodynamical design basis and marine disposal of wastewater
Authors: Hansen I. S. , Vested H. J. , Latif M. A.
Published: May 2018

A modelling study of the hydrodynamics and spreading of wastewater from existing and future outfalls in the Bosphorus region has been conducted applying a 3-Dimensional model. The modelling is based on SYSTEM 3, which is a general modelling system for baroclinic flow simulating unsteady currents, waterlevels, salinity and temperature within the model area. The model set-up covers the Black Sea-Bosphorus-Marmara Sea junction area. The set-up is calibrated by data from a dedicated field program and previous field experience. The model is designed to describe the characteristic features of the flow in the junction area such as the effects of variations in waterlevel differences between the Sea of Marmara and the Black Sea on the important two-layer structure in the strait and the flow fields generated by the upper layer jet in the Bosphorus-Marmara junction. This model has been applied for evaluation of disposal of wastewater and for the subsequent water quality studies. The general use of a baroclinic 3-D hydrodynamic model to simulate disposal of wastewater is discussed. Examples of the application of the model of the junction area to evaluate the different strategies for disposal of wastewater are presented.
Near-field modeling of the Mamala Bay outfalls
Authors: Roberts Philip J. W.
Published: May 2018

Preliminary results of near-field modeling of the wastefield formed by the Sand Island, Honolulu, outfall are presented. Over one thousand simulations were run with the mathematical model RSB using as input data long time series of effluent flowrate and oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers (ADCPs), and density stratification measured by thermistor strings. It was found that considerable variability in plume behavior occurs, whose extremes depend on particular combinations of flowrate, current, and density stratification. The wastefield is predicted to be submerged, usually deeply, about 90% of the time for the conditions simulated. It is demonstrated that the use of these recently developed instruments combined with appropriate mathematical models can lead to greatly improved predictions of the statistical characteristics of wastefield behavior in coastal waters than has been previously possible.
Mass balance of total phosphorus in the Izmit Bay
Authors: Legovic T. , Morkoç E. , Okay O. S. , Egesel L. , Tüfekci V. , Tüfekci H.
Published: May 2018

Elements needed to obtain mass balance of a nutrient in a coastal sea by direct methods are: movement of water masses (current field), estimates of location and intensity of all major nutrient sources, estimate of nutrient inflow from the neighboring sea and a reliable estimate of the nutrient extinction in the water column. In practice, the intensity of major sources and extinction of nutrient water column are seldom known. Therefore inverse methods for the transport equation are employed to obtain mass balance.

Mass balance of total phosphorus in the Izmit Bay for March 1994 suggests that total source from the coast is about 1.3 t P/day. The extinction constant is 12 days. The majority of TP originating from the land-based sources of the bay proper ends up in the lower layer of the bay. A small part is transported into the Marmara sea.
Scientific basis for wastewater treatment and disposal in Istanbul
Authors: Orhon Derin
Published: May 2018

The Istanbul Metropolitan Area is located in a very critical area between the Marmara Sea, the Bosphorus and the Black Sea. Recent investigations clearly indicate that the Marmara Sea now possesses all the striking properties of a sensitive zone. Therefore the nature and the magnitude of wastewater treatment and disposal is a major factor to be considered for the protection of the Marmara Sea. Conversely, wastewater management in Istanbul should be carefully defined and optimized on the basis of the delicate hydrodynamic and ecological balance between the adjacent seas. The paper critically reviews all related findings to provide a scientific basis for major factors requiring specific emphasis in a wastewater management program for Istanbul. In this framework, highly controversial issues, such as need for nutrient removal for discharges to the Marmara Sea, degree of treatment required around Bosphorus and the junction zone, and the location of Kadiköy and Riva discharges are critically evaluated in the light of the existing scientific evidence.
Modelling of the micromorphology of the activated sludge floc: low do, low F/M bulking
Authors: Takács Imre , Fleit Ernö
Published: May 2018

Two common causes of filamentous bulking of activated sludge are low dissolved oxygen (DO) concentration and low food to microorganism (F/M) ratio in the activated sludge system. A dynamic mathematical model was developed to simulate the population dynamics of two groups of bacteria, floc-formers and filaments within the microenvironment of the activated sludge floc. An arbitrary grid of 50 by 50 elements was applied to a hypothetical floc of maximum 100 μm in diameter. The concentration of DO and soluble substrate was calculated inside the floc core under different bulk concentration conditions in order to simulate the effect of heterogeneous, gradient-governed microenvironments on dual species composition. Dynamic simulation runs were performed to calculate the growth of the two morphological types of microorganisms inside the floc under diffusion governed conditions. The results indicate that the method accurately predicts the onset of excessive filamentous growth (directly linked to bulking) even when traditional models neglecting diffusion limitation fail to do so. The positive feedback effect of the non-random (unidirectional) growth on the selective enrichment of filamentous organisms under electron acceptor (DO) or soluble substrate (F/M) limited conditions is demonstrated.
Review of marine outfall systems in Taiwan
Authors: Lei Yang
Published: May 2018

There are three marine outfall systems in Taiwan called Da-Lin-Pu (DLP), Chung-Chou (CC), and Tso-Ying (TY), respectively. All of the systems are located in the south of Taiwan along the 20 km long coastline of Kaohsiung City. The DLP and TY systems are discharging industrial wastewaters, while the sewage produced from Kaohsiung City with population of 1.4 million is discharged into the ocean through the CC marine outfall system. The lengths of the DLP, CC and TY outfall pipes are 3350, 3000 and 5045 m, respectively, and all three are designed with the same initial dilution ratio of 100:1. The three systems are located within a 20 km long coastline. Thus the ocean climate and seawater quality of the outfall field are similar to one another. On average, the coastal current flows mostly southeastwards with velocities ranged between 30 and 40 cm/sec, while the average tidal range is about 47 cm. Generally, the seawater quality in the outfall fields is still under the limiting criteria. However, the concentrations of phenols and oil and grease are found, sometimes, higher than the limiting criteria. This is probably because the wastewaters are mostly from petrochemical plants, and the outfall fields are near the Kaohsiung Harbor. Since the concentrations of N and P nutrients in the seawater are still below the limiting criteria, the problem of “red tide” has not yet occurred in this oceanic area.
Removal efficiency of the constructed wetland wastewater treatment system at Bainikeng, Shenzhen
Authors: Yang Yang , Xu Zhencheng , Hu Kangping , Wang Junsan , Wang Guizhi
Published: May 2018

In this paper, three years study on a constructed wetland wastewater treatment system at Bainikeng, Shenzhen, is reviewed and summarized. The wetland system under study occupies an area of 8400m2, with a design flow of 3100 m3 per day. The study was conducted to understand removal efficiencies of constructed wetland systems for municipal wastewaters from small or medium scale towns in the sub-tropics. Such parameters as biological oxygen demand, chemical oxygen demand, suspended solids, total nitrogen, and total phosphorus in the influent and effluent of the wetland system are examined, and their removal rates are determined. It is shown that the system is very effective in removing organic pollutants and suspended solids and its removal efficiency is much similar to those of the constructed wetlands at Tennessee Valley Authority (TVA) (Choate et al., 1990) while better than those of conventional secondary biochemical treatments.
Nitrogen removal from pretreated wastewater in surface flow wetlands
Authors: Wittgren Hans B. , Tobiason Scott
Published: May 2018

The wastewater treatment plant in the town of Oxelösund (12,500 inhabitants), Sweden, has mechanical and chemical treatment for removal of BOD and phosphorus. With the aim to achieve 50% nitrogen removal, a surface flow wetland system of 21 ha was created as a final step during 1993. It consists of 5 cells, where 2+2 are operated in parallel with a final common cell. This allows intermittent filling and emptying, the goal of which is to promote both nitrification and denitrification for a design flow of 6000 m3 day−1. During the first year of operation, August 1993 to July 1994, the wetland removed 720 kg ha−1 of total nitrogen from the load of 1810 kg ha−1. Ammonium-N was the dominant fraction at the inlet as well as at the outlet, 79% and 90% of total nitrogen, respectively. The large fraction of NH4+ at the outlet showed that nitrification was the limiting step. An intensive monitoring effort in May 1994 indicated that neither wastewater toxicity nor oxygen deficiency were likely to limit nitrification. Instead, sub-optimal hydraulic loading conditions; a lack of suitable surfaces for ion exchange of NH4+, as well as for attachment of nitrifiers; and phosphorus deficiency, were considered potentially important factors in limiting nitrification. In addition to nitrogen removal, the wetland system reduced total phosphorus, BOD7 and E. coli (44°C) to very low levels at the outlet.
Cold-climate constructed wetlands
Authors: Mæhlum T. , Jenssen P. D. , Warner W. S.
Published: May 2018

This paper outlines design considerations for constructed wetlands with horizontal subsurface flow treating domestic wastewater in cold climates of northern latitudes. Particular attention is devoted to the use of a filter medium with high phosphorus adsorption capacity. Experience from two Norwegian multistage systems consisting of an aerobic pretreatment step followed by constructed wetland units indicates purification processes are nearly the same during winter and summer seasons, with quite high removal of organic matter (COD, BOD), phosphorus and nitrogen.