bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving settling dynamics of activated sludge by adding fine talc powder
Authors: Rasmussen Michael R. , Larsen Torben , Clauss Frédéric 
Published: May 2018

The effect of adding varying mixtures of talc and chlorite powder to activated sludge in order to improve the settling characteristic has been studied. The powder is found to improve the settling velocity of the sludge, strictly by increasing the average density of the sludge floc aggregate. The settling velocity was measured with a recirculated settling column under different concentrations and turbulence levels.
Numerical simulation of a secondary settling tank indicates that adding fine powder will improve the overall performance considerably.
Pesticide contamination of water resources: a case study - the rivers in the Paris region
Authors: Tisseau M. A. , Fauchon N. , Cavard J. , Vandevelde T. 
Published: May 2018

For a number of years, the Compagnie Générale des Eaux has been studying pesticide contamination of surface water in order to better understand the origins and the main transfer mechanisms of these pollutants into water resources. Sampling campaigns are being carried out on the three main rivers of the Paris area to monitor a number of products from the triazine and urea families.
This monitoring has confirmed the extension of agricultural non-point source pollution. The products being sought are present in the three rivers and, in most cases, in significant concentrations.
Atrazine is the most important contaminant. Measured concentrations exceed the value of 100 ng/l most of the time, thus proving that the aquifers drained by the three rivers are contaminated. For a period of several months every year, concentrations approaching 1000 ng/l are observed in all the catchment areas being studied. These are the result of rapid transfers of atrazine in run-off water.
This surface run-off transfer mode also seems to be applicable to the ureas found in surface water, especially during the periods when the products are used to treat crops.
These works underline the complexity of agricultural non-point source pollution phenomena. They permit the identification of the predominant mechanisms operating in the transfer of the products. This is the first step towards setting up preventive measures and developing pollution forecasting tools.
Experience with nutrient removal in a fixed-film system at full-scale wastewater treatment plants
Authors: Borregaard Vibeke R. 
Published: May 2018

In the upgrade of wastewater treatment plants to include biological nutrient removal the space available is often a limiting facor. It may be difficult to use conventional suspended growth processes (i.e. activated sludge) owing to the relatively large surface area required for these processes.
Recent years have therefore seen a revived interest in treatment technologies using various types of attached growth processes. The “new” attached growth processes, like the Biostyr process, utilise various kinds of manufactured media, e.g. polystyrene granules, which offer a high specific surface area, and are therefore very compact.
The Biostyr plants allow a combination of nitrification-denitrification and filtration in one and the same unit. The results obtained are 8 mg total N/l and an SS content normally below 10 mg/l. The plants in Denmark which have been extended with a Biostyr unit have various levels of PLC control and on-line instrumentation.
Structure and function of a nitrifying biofilm as determined by microelectrodes and fluorescent oligonucleotide probes
Authors: Schramm A. , Larsen L. H. , Revsbech N. P. , Amann R. I. 
Published: May 2018

Microelectrodes for O2 and NO2−/NO3− and fluorescently labelled 16S rRNA-targeted oligonucleotide probes were combined to examine the activity and stratification of nitrifying bacteria in a trickling filter biofilm. Microprofiles showed that O2 consumption and NO3−/NO2− production were restricted to the upper 50-100 μm of the biofilm. The vertical distribution of the nitrifying bacteria Nitrosomonas sp. and Nitrobacter sp. was investigated by fluorescent in situ hybridisation (FISH) with specific oligonucleotides. Nitrifiers formed a dense layer of cells and cell clusters in the upper part of the biofilm. This correlates well with the measured activity profiles.
Ammonia- and nitrite-oxidisers occurred in close vicinity to each other supporting a fast sequential metabolism from ammonia to nitrate. Both species were not restricted to the oxic part of the biofilm, but also appeared -in lower numbers- in the anoxic layers on the bottom of the biofilm.
A short term decrease in the O2 concentration of the bulk water resulted in a quick decrease in O2 penetration and metabolic rates inside the biofilm. However, neither the stratification nor the cellular ribosome content of nitrifiers changed within a few hours.
Characterization of activated sludge flocs structure
Authors: Snidaro D. , Zartarian F. , Jorand F. , Bottero J.-Y. , Block J.-C. , Manem J. 
Published: May 2018

Activated sludge is the most widely used process for wastewater treatment. However basic properties such as floc structure or settling properties, still remain unknown. In order to describe activated sludge floc structure, four investigation methods were used: (i) size distribution analysis associated with sonication, (ii) transmission electron microscopy (iii) laser scanning confocal microscopy and fractal dimension analysis, and (iv) three dimensional modelling.
The evolution of floc size distribution in dispersed samples was used to build a model of floc showing that the predominating microflocs (125 μm) are formed from 13 μm aggregates, which are made up of smaller particles (2.5 μm). By transmission electron microscopy it was assumed that the 2.5 μm sub-units could correspond to microorganisms and that exopolymers form a gel-like matrix which holds the structure of the aggregates together.
The microfloc (13 μm) structure was investigated by confocal scanning light microscopy and image processing. The analysis of the mass distribution pointed out that the microfloc is a fractal object (fractal dimension around 3). The total number of cells in these aggregates was found to be 2n number. These two results suggest that division of microorganisms explained the formation of 13 μm units which are microcolonies.
A mass fractal dimension 2.5 ± 0.15 was measured for the microfloc. Its external surface was reconstructed by using interpolating software (GOCAD). It appeared that the surface is also a fractal object with a dimension 2.3 ± 0.1. According to the fractal theory, it seems that diffusion limited aggregation via monomer-cluster collision is the mechanism which describes the formation of macroflocs.
The design of wetland systems for the treatment of urban run off
Authors: Shutes R. B. E. , Revitt D. M. , Mungur A. S. , Scholes L. N. L. 
Published: May 2018

The results of studies of the pollution removal performance of constructed wetlands for urban runoff treatment are discussed. The design of urban runoff wetlands including primary treatment components, substrate composition and flow rate regulation are considered.
The use of front-end treatment systems such as oil interceptors, spillage containment facilities and wetland forebays or lagoons are recommended to provide an initial pollutant removal capacity as well as attenuating the impact of high discharges. Design criteria which will ensure inlet flow velocities do not exceed 0.7m/s and which will achieve optimum retention times (10-15 hours) for maximum pollutant removal are described. The relative advantages of different soil types are discussed and an overall minimum substrate depth of 0.6m is recommended for sub-surface systems. Two case studies of urban runoff wetlands in the UK which are currently being monitored are described.
A stochastic model for two-station hydraulics exhibiting transient impact
Authors: Jacobsen J. L. , Madsen H. , Harremoès P. 
Published: May 2018

The objective of the paper is to interpret data on water level variation in a river affected by overflow from a sewer system during rain. The simplest possible, hydraulic description is combined with stochastic methods for data analysis and model parameter estimation. This combination of deterministic and stochastic interpretation is called grey box modelling.
As a deterministic description the linear reservoir approximation is used. A series of linear reservoirs in sufficient number will approximate a plug flow reactor. The choice of number is an empirical expression of the longitudinal dispersion in the river. This approximation is expected to be a sufficiently good approximation as a tool for the ultimate aim: the description of pollutant transport in the river.
The grey box modelling involves a statistical tool for estimation of the parameters in the deterministic model. The advantage is that the parameters have physical meaning, as opposed to many other statistically estimated, empirical parameters. The identifiability of each parameter, the uncertainty of the parameter estimation and the overall uncertainty of the simulation are determined.
A procedure for selecting best identifiable parameters in calibrating activated sludge model no. 1 to full-scale plant data
Authors: Weijers Stefan R. , Vanrolleghem Peter A. 
Published: May 2018

A systematic procedure for selecting identifiable parameter subsets for a given set of measured outputs is proposed. The aim is to only select those parameters which can be estimated uniquely from the dataset used. The proposed procedure consists of first selecting a reduced set of most sensitive parameters by sensitivity analysis and subsequently selecting identifiable parameter subsets using the Fisher information matrix.
For a particular set of outputs obtained from a typical calibration exercise at a carrousel-type nitrogen removal plant, parameter subsets ranging from two to eight parameters were selected by this procedure. The procedure proved successful as the parameter subsets thus selected could be estimated accurately from simulated data without and with noise as well as from real data.
However, the procedure is based on a property which is local in parameter space. Consequently, as an a priori assumption on the parameter vales has to be made at the start of the procedure, the selection results might be different from the results which would have been obtained by using the a posteriori parameter values. Hence, the sensitivity towards this a priori assumption was tested explicitly. For this purpose, the parameter space was sampled according to a Latin hypercube sampling scheme and the selection procedure was applied in all sampling points as if these were a priori estimates. From this extensive study it could be concluded that the results of the procedure were not too severely influenced by the a priori assumption on the parameter values. Therefore, the proposed procedure appears to be a powerful and practical tool for efficient and reliable model calibration.
The use of constructed wetlands to upgrade treated sewage effluents before discharge to natural surface water in texel island, The Netherlands – pilot study
Authors: Schreijer M. , Kampf R. , Toet S. , Verhoeven J. 
Published: May 2018

Since 1988 experiments have been carried out on a pilot scale on polishing of sewage treatment plant (STP) effluent in a constructed wetland system, a combination of a macrophyte bed and a lagoon. The hydraulic retention time (HRT) has been between one and ten days. At HRTs of 2-3 days a favourable oxygen regime and a high degree of removal of E. coli bacteria could be obtained. The natural alternation of low and high oxygen levels resulted in an extra nitrogen removal from the low levels of nitrogen in the effluent of the STP. Phosphorus removal in the wetland system under these conditions was low, therefore chemical precipitation has to take place in the STP.
The favourable results of the study have led to the construction of a full scale 3.5 ha wetland system for the treatment of 3500 m3 effluent day−1 in 1994. The HRT is 2.1 days at dry weather flow. The purpose of this wetland is to further polish the STP effluent in order to match the water quality of the natural local surface waters.
Evaluation of sludge dewatering reed beds: a niche for small systems
Authors: Kim B. J. , Smith E. D. 
Published: May 2018

The U.S. Army Construction Engineering Research Laboratories (USACERL) has been developing and adopting improved sludge dewatering systems for U.S. Army wastewater treatment plants. USACERL selected reed beds as the best alternative for future Army sludge dewatering systems based on the system's economical and technical feasibility and on a demonstration of the technology at Fort Campbell, KY, USA.
This paper compares the Army's options for upgrading Fort Campbell's sand-drying beds, analyzes costs, discusses sludge hydraulic and solids loading rate data from existing reed bed operations in the United States, and presents 5 years' operational data from Fort Campbell. Options considered for comparison included: land application of sludge at training fields, wedgewater beds, vacuum-assisted beds, wedgewater beds and composting, mechanical dewatering systems, and a “no change” option in which sand-drying beds would have been retained.
In conclusion, this paper summarizes advantages and limitations of reed bed sludge dewatering. Advantages of reed beds may include: low investment especially when sand-drying beds are converted to reed beds, savings of sludge removal costs, and the benefits inherent to using a simple and economical technology. Limitations may include: large land requirements and little scientific understanding of this empirical technology. The challenge will be to further develop appropriate disposal technologies to meet new U.S. sludge regulations.
Effects of temperature and volatile fatty acids on nitrification-denitrification activity in small-scale anaerobic-aerobic recirculation biofilm process
Authors: Takai T. , Hirata A. , Yamauchi K. , Inamori Y. 
Published: May 2018

The purpose of this study is to clarify effects of temperature, volatile fatty acids (VFAs) and recirculation on nitrification-denitrification activity and biota such as nitrifying bacteria in a small-scale domestic wastewater treatment process. Effects of VFAs produced in anaerobic biofilm reactors under various flow-rates and recirculation ratios on nitrifying bacteria were also investigated with laboratory-scale plants on a long-term stable conditions. As a result, at a temperature of 10°C, nitrification activity could be increased about 65% by recirculation and nitrogen removal efficiency was also surely raised. Temperature coefficients of nitrification rate at recirculation ratios of 0 and 4.0 were 1.039 and 1.090, respectively, and that of denitrification was 1.065 at recirculation ratio of 4.0.
High concentrations of VFAs were found in anaerobically treated effluent, especially at 10°C without recirculation, and inhibition of nitrite oxidation and nitrite accumulation were observed in the aerobic biofilm reactor. From batch experiments, VFAs' inhibition constants γ in nitrification activity of aerobic biofilm was calculated, and consumption rates of each VFA was investigated on the condition that denitrification was progressed or not. It was clarified that each VFA did not inhibit ammonium oxidation in observed concentration, but slightly inhibited nitrite oxidation. Acetic acid was used as a carbon source of denitrification at the rate of 17.3mg/mg-SS/hr. On the other hand, propionic acid was not used effectively and denitrification did not occur. It was concluded that the recirculation was indispensable to promote nitrification-denitrification activity and biodegradation of VFAs in the small-scale anaerobic-aerobic biofilm process.
Effects of hydraulic shock loads on small on-site sewage treatment unit
Authors: Panswad T. , Komolmethee L. 
Published: May 2018

This research was to determine the effects of hydraulic shock loads by intermittent feeding on the removal efficiency of a small prefabricated real-sized septic tank/anaerobic filter unit. Besides the ‘control’ 24-hour continuous runs the other twice a day feeding periods covered 16, 12 and 8 hours per day, with the tank's retention time varying from 22.5 to 90 hours. It was demonstrated that the variation of the hydraulic feeding patterns ranging from 24-hour continuous feed to 8 h per day intermittent feed did not affect the performance of the system much. The percentage of BOD reduction was decreased from 85 to 82 and 81 percent for the feed times of 24, 16 and 8 hours per day, respectively.
The tank capacity played a relatively major role in determining the removal efficiency of the process. The efficiency of BOD and SS reduction dwindled from 82.2 to 68.9 and 56.0% with the corresponding reduction in tank sizes from 90 to 45 and 22.5 hours retention, respectively. In any event, the unit could not satisfactorily remove nutrients. A retention period of not less than 48 hours is recommended if the Thai effluent standards are to be met. Equations for predicting the BOD removal capability were also developed.
Effects of calcium ion on sludge conditioning
Authors: Chang Min-chao , Chuang Shun-hsing , Lin Hui-ling 
Published: May 2018

Investigating the sludge conditioning behavior and improving sludge conditionability were the primary objectives of this study. The effects of calcium ion with and without polyelectrolyte conditioning behavior on two industrially activated sludge systems were studied via Capillary Suction Time (CST) tests.
Experimental results indicated that the calcium ion can strongly enhance the conditionability of the industrial biological sludge system. The good conditionability of calcium ion added system could have possibly resulted from the interaction of polysaccaride from activated sludge with calcium ion. Additionally, adding polyelectrolyte solution first would produce more suitable conditioning in a situation in which calcium ion is involved with polyelectrolyte system.
Improved design and control of industrial and municipal nutrient removal plants using dynamic models
Authors: Coen F. , Vanderhaegen B. , Boonen I. , Vanrolleghem P. A. , Van Meenen P. 
Published: May 2018

Dynamic simulation can be used to improve the design and performance of the activated sludge process. This is illustrated by means of two case studies:The simulation of a full scale industrial plant treating nitrogen-rich wastewater by an intensive nitrification-denitrification process. By means of simulation the most important operational cost (dosage of an external carbon source) was optimised and a control strategy was proposed.The simulation of a municipal wastewater treatment plant with the extension of nitrogen removal. Based on simulation the feasibility of the redesign was evaluated.
In both cases the wastewater composition was characterised and the biological model (the activated sludge IAWQ-model No. 1) calibrated. By means of respirometry and standard laboratory analyses it was possible to estimate the COD fractions of the wastewater and the parameters for heterotrophic and autotrophic growth of biomass.
Nitrogen removal from wastewater with high ammonia nitrogen concentration via shorter nitrification and denitrification
Authors: Surmacz-Górska Joanna , Cichon Andrzej , Miksch Korneliusz 
Published: May 2018

Shorter nitrification is reached through Nitrobacter bacteria activity inhibition. Nitrobacter bacteria responsible for nitrite nitrogen oxidation are sensitive to free ammonium. The presence of free ammonium depended on a high ammonia nitrogen concentration in wastewater and its pH. It was the pH of the wastewater that was the decisive parameter in Nitrobacter bacteria activity inhibition in stable temperatures and at stable ammonia nitrogen concentrations. Reaction control in the aeration phase of the treatment process guaranteed the concentration of free ammonium within the 1 to 6 mg NH3/l range and at the same time concentration of free nitrous acid did not exceed 0.04 mg HNO2/l. It allowed nitrification to be significantly shortened and to receive build-up of nitrite nitrogen up to 300 mg NO2-N/l. Nitrification rate was about 0.06 g N/g MLSS·d.
Measured oxidation rates of particular groups of nitrifying bacteria as oxygen uptake rates by Nitrosomonas and Nitrobacter bacteria respectively made control of shorter nitrification easier and gave insight into the activity of both nitrifier groups.
A technique in confocal laser microscopy for establishing biofilm coverage and thickness
Authors: Silyn-Roberts G. , Lewis G. 
Published: May 2018

This study uses confocal laser scanning microscopy to determine the coverage and thickness of biofilms on rock types commonly used in wetland sewage treatment systems in New Zealand. Samples of scoria, greywacke and slag - with glass used as a comparison - were submerged in subsurface flow wetlands and examined after six weeks.
An image analysis technique was used to quantitatively determine the coverage and thickness of each biofilm. The technique consisted of the biofilm quantification of each individual image obtained from the confocal optical sectioning. The results indicated that the biofilm coverage for the substrata types did not exceed 25%. However, there was a marked difference between the biofilm structures grown on the different substrata; that on glass formed thin spindly structures, and slag and scoria showed similar dense patches interspersed with open channel structures that followed the contours of the pocketed rock surface.
Study of the reactor with down-flow injection on the characteristics of ozonation
Authors: Morioka Takayuki , Kato Yasuhiro , Hoshikawa Hiroshi , Okada Mitsumasa , Moniwa Takeo 
Published: May 2018

The ozone transfer from the gas-phase to the liquid phase in the down-flow tube of the reactor showed high efficiency because of its large value of gas-liquid interface area. The estimated gas-liquid interface area of the down-flow tube was approximately in the range from 60 to 600 (1/m).
The ozone transfer efficiency (O.T.E.) of the down-flow tube was increased with the increase in ozone gas concentration. Therefore, it was clear that a high concentration of ozone gas should be applied when a higher ozone dose was needed for ozonation.
The estimated dissolved ozone concentration and O.T.E. by a mathematical model which was developed in this investigation showed good agreement with experimentally obtained data. As a result, it was shown that the model was able to describe the ozone absorption in the reactor with down-flow injection (DFI) in the wide range of operational variables.
In the case study that was carried out to compare the Cryptosporidium removal of DFI with that of a conventional fine bubble diffusion reactor by numerical simulation, DFI showed a higher performance. This higher performance is contributed to the advantage of DFI which includes the usage of high concentration ozone, greater gas-liquid interface area in the down-flow tube, and the preferable dissolved ozone profile in DFI.