bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of photoreactivation following ultraviolet light disinfection
Authors: Kashimada Koji , Kamiko Naoyuki , Yamamoto Kazuo , Ohgaki Shinichiro
Published: May 2018

Photoreactivation of microorganisms following UV disinfection is one of the research topics of interest in assessing the performance of UV disinfection, because there is little consensus on how the visible light intensity relates to the photoreactivation rate and the maximum survival in wastewater treatment processes. Apparent photoreactivation by a fluorescent lamp was observed in case of indicator bacteria (heterotrophic bacteria, coliform bacteria, fecal coliforms) in raw sewage, but not E. coli B and E. coli K12 A/λ(F+). Inactivation of fecal coliform was observed simultaneously during photoreactivation process by sunlight. Dose rate at 360 nm wave length as visible light intensity showed that it was a useful indicator for assessing the photoreactivation rate and the maximum survival when photoreactivation took place by both fluorescent lamp and sunlight. The model for photoreactivation was developed. The photoreactivation rate increased with increasing visible light intensity at 360 nm. However, the maximum survival value may not be affected by visible light intensity.
Use of wastewater for crop production under arid and saline conditions: yield and hygienic quality of the crop and soil contaminations
Authors: El Hamouri Bouchaïb , Handouf Abderrahim , Mekrane Mohamed , Touzani Mohamed , Khana Addi , Khallayoune Khalid , Benchokroun Taïeb
Published: May 2018

Raw (RW) and Waste Stabilization Ponds treated wastewater (TW) were used in comparison with groundwater (Control) for crop production under arid and saline conditions without any chemical fertilization. Four irrigation methods namely, surface, drip (with 2 systems “Bas Rhône” and “Rain bird”) and sprinkler irrigation were compared on each water type. The results of the 3-year-experimentation period were: a) TW applications instead of groundwater attenuated the detrimental effect of water salinity on the crop; b) Drip irrigation, “Bas Rhône” system, showed the highest irrigation performances and crop yields; c) the morphology and the way the crop was conducted were found to play an important role in determining its final bacteriological quality; d) TW irrigated crops and soils did not show any helminth eggs contaminations and e) Faecal coliforms were not isolated from the TW irrigated soil beyond the limit of 0.25 m.
Management of domestic wastewater for reuse in irrigation
Authors: Vazquez-Montiel Oscar , Horan Nigel J. , Mara Duncan D.
Published: May 2018

Treated effluent from an aerated lagoon and facultative pond system in southern Portugal, was used to irrigate fields planted to maize (Zea mays L.). The effluent was characterised with respect to its nitrogen and phosphorus content and applied by drip irrigation in response to crop evapotranspiration requirements. Nitrification of ammonia in the effluent by soil microorganisms caused a reduced soil pH early in the growing season, but this was reversed as the season continued. For most of the growth season plant nitrogen demand ensured a low soil nitrogen concentration, but towards the end of plant growth the continuous nitrogen supplied in the effluent exceeded crop requirements with a result that nitrate accumulated in the soil. The applied effluent also had a high phosphorus concentration but there was only a slight accumulation of this in the soil. The fertiliser value of the treated effluent was demonstrated by increased yields at physiological maturity and the N yield was within the range of expected values for this crop. The main removal mechanism for N during irrigation was crop uptake whereas P was removed primarily by soil processes. The advantages of wastewater reuse together with the importance of appropriate management practices for re-use are discussed.
Reuse of wastewater treated by infiltration percolation
Authors: Ouazzani Naïla , Bousselhaj Khadija , Abbas Younes
Published: May 2018

The aim of this work was to determine the depuration efficiencies of an infiltration percolation plant to remove organic matter and nutrients (N and P) and to test the effect of treatment by such system on the fertilizer value of wastewater compared to untreated influent and a control (groundwater). Results of investigations carried out over a month of each season showed the high capacity of this depuration system to remove both particulate and dissolved organic matter (TSS 91%, COD 93% and dCOD 89 to 95%) at all season. Nitrogen and phosphorus were more eliminated at winter and summer. At spring they presented a low percent removal efficiency due probably to overloaded influent. Tests consisting in the reuse a raw wastewater (RW), settled wastewater (SW) or completely treated wastewater (FW) for irrigation of (Lolium perenne) plots showed that biomass yield, nutrients (N,P) exported by plants and protein amount in the plants tissue decreased from plots irrigated by (RW) to completely treated wastewater. But all of them were more important than in the control plants (irrigated by groundwater) and exceeded the mean values reported in literature for meadows plants. The amount of nitrogen and P2O5) applied during the irrigation by wastewater, was equivalent or superior to recommanded dose of fertilizer for meadows. The expected meat or milk production showed a promising potentiality to promove the nutritional quality of farm animals food by using treated wastewater.
The denitrification and neutralization performance of an electrochemically activated biofilm reactor used to treat nitrate-contaminated groundwater
Authors: Sakakibara Y. , Araki K. , Watanabe T. , Kuroda M.
Published: May 2018

Continuous denitrification of nitrate-contaminated groundwater containing dissolved oxygen (DO), SO42−, and no buffer was carried out with three identical electrochemically activated biofilm reactors. The reactors consisted primarily of denitrifying biofilm attached to the surface of the cathode, an amorphous carbon employed as the anode, and a DC power supply. In the reactors, denitrification and neutralization caused by H2 and CO2 produced from the cathode and the anode, respectively, occurred simultaneously when an electric current was applied. A complete-mix reactor model coupled with a biofilm-electrode model was developed in conjunction with a limiting-current theory. When the biofilms were sufficiently acclimated and adapted to the electric current, the denitrification performance calculated using the model was in fairly good agreement with experimental results.
Process design for nitrogen removal using nitrifying biofilm and denitrifying suspended growth in a biofilm airlift suspension reactor
Authors: van Benthum W. A. J. , van Loosdrecht M. C. M. , Heijnen J. J.
Published: May 2018

Operation of a Biofilm Airlift Suspension (BAS) reactor was possible with nitrifying biofilm growth and heterotrophic suspended growth, simultaneously converting ammonium and acetate. Control of the location of heterotrophic growth, either in suspension or in layers over the nitrifying biofilms, was established by manipulation of the hydraulic retention time. Two process configurations (based on the BAS reactor) are identified, for nitrogen removal from wastewater by integration of nitrification in biofilms and denitrification in suspension. The first set-up consists of a conventional nitrifying BAS reactor, coupled with a suspended biomass reactor (without biomass retention). The second process configuration is a single BAS reactor which is sequentially aerated and non-aerated, by cyclically recirculating the offgas. Process design schemes for these configurations are presented and the design aspects are evaluated. Three limiting processes are identified: gas-liquid oxygen transfer, the hydraulic capacity of the settler and the minimal time needed for oxygen depletion of the gas phase during offgas recirculation. It was found that the two-reactor configuration is mainly suitable for pre-treatment of concentrated ammonia containing wastewaters. The one-reactor configuration can be applied to obtain low nitrogen concentrations in the effluent.
Characterization of aerobic azo dye-degrading bacteria and their activity in biofilms
Authors: Coughlin M. F. , Kinkle B. K. , Tepper A. , Bishop P. L.
Published: May 2018

An azo dye-degrading strain, originally named TBX65, was isolated from the mixed liquor of the Mill Creek waste water treatment plant in Cincinnati, Ohio. Strain TBX65 has the unusual ability to aerobically reduce the azo bond of several azo dyes and is able to use some of these dyes as growth substrate. Subsequent investigations have revealed that TBX65 is actually composed of several strains including two azo dye-degrading strains, MC1 and MI2. Strain MI2 is able to use the azo dyes AO7 and AO8 as its sole source of carbon, energy, and nitrogen. In contrast, MC1 can aerobically reduce the azo bond of these dyes but only in the presence of an exogenous source of carbon and nitrogen. Both MC1 and MI2 are Gram negative, rod-shaped bacteria that form yellow colonies. Sequencing and phylogenetic analysis of the 16S rRNA gene of MC1 indicates that it is a strain of Sphingomonas. Based on this phylogenetic analysis, the most closely related strain to MC1 is strain C7, a previously described azo dye-degrading bacterium isolated from biofilms growing in our laboratories. A strain-specific fluorescent antibody has been developed for strains MC1 and MI2, and is being used to determine the survival and azo dye-degrading ability of these strains in biofilms generated in a rotating drum bioreactor.
Maximizing trickling filter nitrification rates through biofilm control: research review and full scale application
Authors: Parker Denny S. , Jacobs Tom , Bower Erich , Stowe Dennis W. , Farmer Greg
Published: May 2018

Tertiary nitrifying trickling filters (NTFs) at the Littleton/Englewood wastewater treatment plant provide for nitrification to meet seasonally varying effluent requirements for ammonia nitrogen. Operation of the full-scale facilities during the past two years demonstrates highly efficient oxidation of ammonia and the effectiveness of biofilm control strategies. A decline in nitrification performance caused by predators was successfully corrected by the use of a special alkaline backwash feature which controlled the level of larval development within the NTFs.
Acceleration of mass transfer in loop reactors
Authors: Van den Heuvel J. C. , Verschuren P. G. , Ottengraf S. P. P.
Published: May 2018

Gas bubbles entrapped in biocatalyst particles subjected to hydrostatic pressure oscillations, e.g. during recirculation in loop reactors, will induce intraparticle liquid flows, and thereby enhance mass transfer in excess of diffusion. This ‘breathing particle’ mechanism was demonstrated in methanogenic granules, and led to a typical activity increase of 13% compared with static pressure conditions. From these experimental results and model predictions, it is concluded that convective acceleration of mass transfer in gas-producing systems offers interesting perspectives for the optimisation of biofilm processes in loop reactors. Development of special carrier materials with a central gas-filled cavity could lead to a novel type of bioreactor in which liquid flow through the biocatalyst is decisive.
Movement of solids in biofilms: significance of liquid phase transport
Authors: Reichert Peter , Wanner Oskar
Published: May 2018

In the one-dimensional mixed-culture biofilm model, volume expansion due to microbial growth leads to a displacement of biomass towards the biofilm surface, where solids (cells and particles) can be detached and attached. In this model there are no suspended solids in the pore volume of the biofilm. In a growing biofilm, this description makes a significant penetration of solids from the bulk fluid into the biofilm impossible and it leads to a fast elimination of attached inert particles from the biofilm. Recent experiments with fluorescent microbeads used as solid tracers are in disagreement with this description. The inert tracer particles added to the bulk fluid penetrate the biofilm quite fast and they show a residence time in the film that is much larger than that of the bacteria. For this reason the processes “transport of solids suspended in the biofilm pore volume” and “attachment to” and “detachment from the solid matrix in the biofilm interior” were added to the mixed-culture biofilm model. These processes were also implemented in the biofilm reactor compartment of the simulation program AQUASIM which is used here to demonstrate that the new processes make a qualitative simulation of the observed behavior possible. Therefore, the mixed-culture biofilm model with these processes added can be used as a tool for further research on the mechanisms which determine the development of the biofilm solid matrix and on transport of solids in the biofilm pore volume.
Inter-calibration of OH radical sources and water quality parameters
Authors: Hoigné Jürg
Published: May 2018

OH radicals are the key oxidants that control most Advanced Oxidation Processes (AOPs) currently applied in water technology and that also occur in some natural systems such as cloud waters. The efficiencies of the various OH radical sources can be experimentally quantified and compared when they are calibrated by following the oxidation of inter-calibrated reference compounds that react during the process only with OH radicals. To apply and generalize the results, however, water quality parameters controlling the lifetime of OH radicals via OH-scavenging reactions by pollutants and further solutes must also be quantified by methods that allow for calibrations.
The density of particle aggregates
Authors: Gregory John
Published: May 2018

Aggregates of particles formed in coagulation/flocculation processes very often have a fractal, self-similar structure, with the very important practical consequence that the effective density of aggregates decreases as their size increases. This has very significant effects on separation processes such as sedimentation, flotation and filtration. The fundamental factors which influence the density of aggregates (flocs) are reviewed, with a discussion of the effects on aggregate size distribution, the rate of formation of flocs and their capture by collectors. Several experimental methods for determining floc density are critically examined.
VUV-photolysis of aqueous systems: spatial differentiation between volumes of primary and secondary reactions
Authors: Heit G. , Braun A. M.
Published: May 2018

Rate and reaction pathway of the degradation of organic compounds in aqueous solution by VUV-irradiation (Xe-excimer: 172 nm) are strongly influenced by the concentration of dissolved molecular oxygen in the volume of primary reactions. Due to the very short lifetimes of the intermediates generated by the homolysis of water, this volume is almost identical with the irradiated fraction of the total reactor volume. Given the fact, that VUV-radiation is totally absorbed within less than 0.1 mm due to the high absorption cross-section of water, investigations on the concentration of dissolved molecular oxygen in the volume of primary reactions require a very high spatial resolution. This spatial resolution is reached by using a very small oxygen optode connected to the photoreactor. The measurements show that VUV-irradiation of a homogenous aqueous system is leading to pronounced heterogeneity: a very thin volume, close to the surface of the light source, which is characterised by the diffusion controlled reactions of primary radicals of very short lifetimes with the organic substrate and the trapping of the C-centered radicals by molecular oxygen, may be differentiated from the remaining major part of the reactor volume in which slower thermal reactions initiated by peroxyl radicals dominate.
Determination of aggregation and breakup constants during flocculation
Authors: Haarhoff Johannes , Joubert Hannes
Published: May 2018

The Argaman-Kaufman flocculation model holds great promise as a practical tool for the generalization of flocculation behaviour from relatively few, simple batch tests in the laboratory. There are, however, valid reasons that have prevented it from being widely accepted in design practice. This paper deals with a number of these obstacles:

• There is the need of a standardized test method in terms of equipment, procedures and data analysis. The effects of settling time and the choice of the flocculation performance parameter are demonstrated.

• The flocculation constants are critically dependent on the level of coagulant dosage. In the sweep flocculation regime, the optimum coagulant dosage cannot be precisely pinpointed with jar testing, which presents a formidable problem for routine application.

• The flocculation constants are, contrary to the model, dependent on the initial particle concentration. This currently precludes the extrapolation of test results to raw water turbidities different from the turbidity at which the test was conducted.

• The flocculation performance parameter is not an intuitive parameter in design practice, and the design procedure for flocculation systems will have to be adapted to reach a specific design objective.
Simultaneous photochemical generation of ozone in the gas phase and photolysis of aqueous reaction systems using one VUV light source
Authors: Hashem T.M. , Zirlewagen M. , Braun A. M.
Published: May 2018

A more efficient use of vacuum ultraviolet (VUV) radiation produced by an immersed Xe-excimer light source (172 nm) was investigated for the oxidative degradation of organic pollutants in aqueous systems. All emitted VUV radiation from one light source was used in two simultaneous but separate photochemical reactions: (1) photochemical generation of ozone by irradiating oxygen in the gas phase and (2) photolysis of the aqueous reaction system. The gas stream containing the generated ozone is sparged into the reaction system, thus enhancing the oxidative degradation of organic pollutants. The photochemically generated ozone in the gas phase was quantitatively analyzed, and the kinetics of the degradation of 4-chlorophenol (4-CP) and of the dissolved organic carbon (DOC) were determined under different experimental conditions. The results show that the rates of degradation of the substrate and of the DOC decrease in the order of the applied processes, VUV/O3 > O3 > VUV.
The structure of hydrous flocs prepared by batch and continuous flow water treatment systems and obtained by optical, electron and atomic force microscopy
Authors: Cornelissen A. , Burnett M. G. , McCall R. D. , Goddard D. T.
Published: May 2018

This paper concerns the imaging of hydrous floc particles by Light Microscopy (LM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The use of a microscope technique means that visual structural information is obtained, in contrast with other techniques measuring particle characteristics. It was found that when a preparation technique was used that involves cryogenic freezing of the sample, before observation in the SEM, larger (1-100 μm) floc particles could be imaged without the loss of structural information normally caused by drying the sample. Damage caused by drying was not apparent with the TEM technique used. It was shown that the various microscope techniques produced compatible results, together covering a wide size range (10 nm-5mm). This indicates that major artefact formation due to sample preparation is unlikely. It was furthermore shown that when a micro-scale continuous flow system was used the reproducibility of the floc structure observed increased.
Selective ozonation of polycyclic aromatic hydrocarbons in oil/water-emulsions
Authors: Kornmüller Anja , Cuno Michael , Wiesmann Udo
Published: May 2018

The ozonation of three to five ring condensed polycyclic aromatic hydrocarbons (PAH) was studied in synthetic oil/water-emulsions by batch experiments. PAH can be oxidized selectively in the presence of high concentrations of dodecane as an aliphatic solvent. No oxidation of dodecane, as a representative of mineral oil, could be observed during all experiments - even at pH around 11. At acid to neutral pH high oxidation rates of the PAH were achieved due to a direct reaction with ozone. In the investigated range of 20 to 40°C no influence of temperature on the ozonation of benzo(k)fluoranthene could be found. During competitive ozonation of five PAH, the reactions are completed in the sequence of acenaphthene, pyrene and finally benzo(e)pyrene, benzo(k)fluoranthene and phenanthrene almost at the same time.
Photocatalytic degradation of organic compounds: accelerating the process efficiency
Authors: Lindner Martin , Theurich Jörn , Bahnemann Detlef W.
Published: May 2018

The photocatalytic activites of several TiO2 materials have been compared studying the degradation of an aliphatic and an aromatic model compound under optimized experimental conditions (e.g., c(TiO2), pH of the solution). For dichloroacetic acid (DCA) a new anatase catalyst, i.e., Hombikat UV100, yielded significantly higher photonic efficiencies (ζ=15%) than almost all the other materials, especially in comparison to rutiles. For 4-chlorophenol (4-CP) the discrepancies were relatively small and the degradation was generally slower (ζ<1%); in this case the formation of intermediates has to be considered, too. While for DCA the addition of CuNO3 (1–10mM) or a platinization of the catalyst lead to a significant raise in ζ, this had almost no effect on the degradation of 4-CP. For this model compound ζ could be accelerated strongly by the addition of bromate (3mM KBrO3); the photocatalytic nature of the process could be demonstrated. The addition of other oxidants had no beneficial effect, in some cases an inhibition was observed. The stability and long time activity of standard and platinized TiO2 materials could be demonstrated.
Oxidation of aromatic compounds with UV radiation/ozone/hydrogen peroxide
Authors: Mokrini A. , Ousse D. , Esplugas S.
Published: May 2018

A large variety of organic and inorganic compounds may be found in wastewater. Among these compounds, aromatics are characterized by their high toxicity and very low degradability by conventional treatments.

This paper presents the results of an investigation about the oxidation of two substituted benzenes in a semi-batch reactor: phenol, substituted with an electron-donating group (-OH), and benzoic acid substituted with an electron- withdrawing group (-COOH). The advanced oxidation processes studied were UV, ozone, hydrogen peroxide and its combinations. The pH dependence and the influence of the initial concentration of hydrogen peroxide were studied to find the optimal conditions for a complete and fast oxidation of both compounds.

Experimental results indicated that both phenol and benzoic acid are destroyed more rapidly by ozone at higher pH (9–12), while ozonation combined with hydrogen peroxide or/and UV is considerably faster at low pH (3–7).
Wet oxidation of phenol by hydrogen peroxide: the key role of pH on the catalytic behaviour of Fe-ZSM-5
Authors: Fajerwerg K. , Foussard J. N. , Perrard A. , Debellefontaine H.
Published: May 2018

This paper presents an original approach to the treatment of phenolic aqueous wastes using H2O2 with Fe-ZSM-5 as a heterogeneous catalyst. The Fe-ZSM-5 zeolite with MFI structure allows a total elimination of phenol and a significant total organic carbon (TOC) removal at 90°C and atmospheric pressure in a batch reactor. The studies with this Fe-ZSM-5 catalyst deal mainly with the influence of external diffusion and pH on the oxidation process. It appears that the phenol degradation and the toxicity reduction, on the one hand, and the leaching-off of Fe(III) ions in the solution, on the other hand, depend strongly on the pH. In these conditions, an optimum value exists at pH = 5. At higher pH values, the system becomes less effective. At lower values, a significant leaching-off will induce homogeneous catalysis and the degradation of the catalyst. Generally speaking, when this heterogeneous catalyst is used in the presence of H2O2, the reaction rates depend on the degree of hydroxylation of the aromatic compound in contact with the catalyst. So, a chain radical mechanism could be envisaged.
Particle counters as tools for managing Cryptosporidium risk in water treatment
Authors: Hall Tom , Croll Brian
Published: May 2018

Outbreaks of waterborne cryptosporidiosis have been a major concern for the Water Industry in the UK and US over the past ten years. Management of risk from Cryptosporidium in water supplies relies heavily upon operation and control of water treatment processes to maximise oocyst removal. Difficulties in measuring oocyst concentrations in water supplies have led to evaluation of surrogate parameters with which to assess oocyst removal by treatment. Whilst turbidity measurement can give an indication of the risk of oocyst breakthrough from filters, a more sensitive indicator appears to be particle counts in filtered water. The paper gives a demonstration of the potential for particle counting as a tool for managing Cryptosporidium risk, and describe ways in which particle counting can be used for monitoring and controlling water treatment plant operation. With the present level of knowledge, the most suitable application for particle counting is as a diagnostic tool for the identification of operating conditions which reduce or minimise particle counts in filtered water at individual sites.
Detoxification and recycling of wastewater by solar-catalytic treatment
Authors: Freudenhammer H. , Bahnemann D. , Bousselmi L. , Geissen S.-U. , Ghrabi A. , Saleh F. , Si-Salah A. , Siemon U. , Vogelpohl A.
Published: May 2018

An introduction to a joint research project is given which deals with the technical application of solar photocatalysis for wastewater detoxification. A non-concentrating thin-film fixed-bed reactor (TFFBR) is used to study applications and areas where a solar-catalytic treatment or recycling of wastewater is possible. This reactor excels by its low cost and an easy-to-build construction using molecular oxygen in air as the oxidising agent. The design parameters of the reactor as well as the process itself have been determined from the reaction kinetics of a model substance, the hydrodynamics and the mass transfer. The treatment of different real wastewaters was successfully carried out, and biologically pre-treated textile wastewater maximum solar degradation rate was about 3 g COD h−1 m−2. A comparison of reaction rates with artifical and solar illumination shows the necessity of outdoor experiments. Due to the reaction rates observed, photocatalysis is suitable as the final stage of purification of biologically or physically pretreated wastewater and will offer a great opportunity for sunrich areas.
Low-concentrating CPC collectors for photocatalytic water detoxification: comparison with a medium concentrating solar collector
Authors: Malato S. , Blanco J. , Richter C. , Curcó D. , Giménez J.
Published: May 2018

The photocatalytic oxidation of 2,4-Dichlorophenol (DCP), using TiO2 suspensions under solar radiation, has been studied at pilot-plant scale at the Plataforma Solar de Almería (PSA). Two different reactor designs were tested: a medium concentrating radiation system called a Parabolic-Trough-Collector Reactor, PTCR, equipped with two motors (azimuth and elevation) to adjust the position of the module perpendicular to the sun, and a low-concentrating radiation system, the Compound-Parabolic-Concentrator Reactor, CPCR, facing south and inclined 37 degrees. Substrates were dissolved in water to required mg L−1 levels in a reservoir tank. In both cases, 0.2 g L−1 of the suspended TiO2 catalyst was used in a 250 L solution of the contaminant, which was recirculated through the photoreactors using a centrifugal pump and an intermediate reservoir tank. The advantages and disadvantages of the two types of photoreactors in DCP oxidation are compared and discussed. The strong potential of photocatalytic peroxydisulphate-assisted degradation in high DCP concentrations was demonstrated in both systems, and chemical actinometry (the decomposition reaction of oxalic acid by radiated uranyl salts) in the CPC reactor is compared with the results obtained in the PTC.
Particle size distribution in an efluent from an advanced primary treatment and its removal during filtration
Authors: Landa H. , Capella A. , Jiménez B.
Published: May 2018

The filtration efficiency of an Advanced Primary Treatment System (APT) was analyzed in terms of suspended solids concentration, particle size distribution and helminth eggs counts. A study was carried out on three one-metre deep sand filters with a specific size (ES) of 0.6, 0.8 and 1.2 mm. More than 50 runs were done with operating rate of 7, 10, 12 and 15 m/h. Basic design-related information was obtained for the APT system. A filter with a 1.2 mm ES provided the best effluent, with 0.1 Helminth egg/L. The average suspended solid concentration in the effluent was 39 mg/L. The most recommendable filtration rate was 10 m/h with a run time of 33 h. A study of the particle distribution was made for each step of the process based on size.
Particle size analysis and sedimentation properties of activated sludge flocs
Authors: Hilligardt Dieter , Hoffmann Erhard
Published: May 2018

Activated sludge is one of the best investigated and understood suspensions. But up to now we still lack the factors influencing the sedimentation velocities concerning the main sludge characteristics/properties to describe the settleability of different sludges. Different in terms of SVI, organic loading, sludge retention time, composition, content of polymers, iron or aluminium, density, porosity and particle size distribution. But for the design of clarifiers most of these parameters are disregarded, of none importance or neglectable. With the help of PSD and particle shape analysis we can improve our knowledge of the settleability of activated sludge flocs. The measurements, done with the CIS show the influence of the differential sedimentation in comparison to the effluent of the secondary clarifiers under different conditions.

Calculating the sedimentation velocities, the behaviour of activated and precipitated sludge could be explained and conclusions can be drawn to optimize the solid flux in secondary clarifiers.
Large scale development of a light-enhanced fenton reaction by optimal experimental design
Authors: Oliveros E. , Legrini O. , Hohl M. , Müller T. , Braun A. M.
Published: May 2018

Photochemical advanced oxidation processes (AOP) for the treatment of waste waters containing biocidal or non-biodegradable organic compounds rely mainly on the production of a potent oxidizing agent, the hydroxyl radical. The Fenton's reagent, a mixture of hydrogen peroxide and ferrous ion, represents one possible source of hydroxyl radicals and it has been shown recently that degradation rates may be significantly enhanced by UV/visible irradiation. In this context, we have investigated the feasibility of a large scale application of the light-enhanced Fenton reaction to the treatment of a highly contaminated industrial waste water containing toxic aromatic amines (dimethyl anilines or xylidines) as the main pollutants. Following preliminary laboratory tests performed on the model compounds, 2,4- and 3.4-xylidines (200 mg/L, 2 L), experimentation on the industrial waste water at a large scale level (3000 mgC/L, 500 L) has been carried out using the experimental design methodology for the simulation and the evaluation of the effects of the two critical factors, hydrogen peroxide and ferrous ion concentrations. The light-enhanced Fenton reaction has been proven to be a most effective treatment process under acidic conditions and might be an alternative to adsorption of xylidines on activated carbon as used at present.
Removal of different kinds of particles in deep bed filters consisting of permeable synthetic collectors (PSC)
Authors: Gimbel R. , Nahrstedt A.
Published: May 2018

The possible use of deep bed filter media composed of permeable synthetic collectors (PSC's) was studied. The PSC's were made of open porous plastic foam or non-woven fabrics in the shape of cylinders with dimensions of some millimeter. With such media, particle retention takes place throughout the entire body of the collectors. Theoretical analysis based on trajectory calculations for non-Brownian particles was carried out for estimating the particle collection efficiency. A parametric study was made to examine the effect of various operating variables (e.g. inner porosity and fibre diameter of the PSC's) and of particle characteristics (e.g. their size and density). In contrast to conventional deep bed filtration using impermeable filter grains, filtration using PSC's performs much better in particle collection. This conclusion was confirmed by experiments with different kinds of particles for the initial and dynamic phase of filtration. Special investigations using an endoscope showed that the adhesion behaviour of the particles inside the PSC's is getting more and more important with increasing amount of deposited particles in the collectors.
Photocatalytic oxidation of aromatic aminocompounds in aqueous solutions and groundwater from abandoned military bases
Authors: Preis Sergei , Krichevskaya Marina , Kharchenko Anna
Published: May 2018

Experimental research into the photooxidation of aqueous solutions and polluted groundwater containing aromatic aminocompounds was undertaken. For the experiments with synthetic solutions, titanium dioxide under near-UV irradiation was selected as a photocatalyst, and aniline, p-toluidine and 2,4-xylidine were selected as model compounds. The photooxidative treatment of synthetic solutions was found to be more effective in acidic and strongly alkaline media. Methylated aminocompounds (p-toluidine, 2,4-xylidine) yield slightly better to photooxidation than aniline. The results obtained from experiments using model compounds were compared with the results of photooxidative purification of polluted groundwater from an abandoned military base in Estonia. Being heavily polluted, the groundwater yields better to photooxidation when diluted with potable water at a 7:3 ratio. Anatase, immobilised onto the surface of buoyant hollow glass microspheres, was less effective than when suspended in slurry. However, the immobilised photocatalyst enables water to be treated without the expense of constant stirring. This also avoids complications concerned with catalyst separation following treatment. Degussa P25 was more effective than Aldrich anatase both in stirred slurry type reactors and when attached to hollow glass microspheres.
Partial oxidation effects during the combined oxidative and biological treatment of separated streams of tannery wastewater
Authors: Jochimsen Jan C. , Jekel Martin R.
Published: May 2018

The ozonation of biologically pre-treated tannery wastewater and the influence of the applied specific ozone consumption onto a subsequent biological treatment were investigated. Combining sum parameters, such as COD, DOC and UV-absorbance, it could be differentiated between mineralization and partial oxidation effects. In the case of UV-removal the newly developed partial oxidation parameters correlate with the subsequent biological removal. It could be shown that partial oxidation of COD is favourable for subsequent biodegradation, whereas further mineralization reduces the effectivity of biological oxidation. The optimal range of subsequent biological treatment was observed at a specific ozone consumption of 1 to 3 g O3/g DOC0. As far as the distribution of molecular weight fractions is concerned, the ozonation leads to a relative increase of the low molecular weight DOC-fraction (< 1,000 u), which includes the majority of the residual UV-absorbance at 254 nm. Acute toxicity, measured as luminescence inhibition of Vibrio fischeri, is affected by ozonation as well. The calculated 1/EC20 data decrease with increasing specific ozone consumption.
Implementation of constructed wetlands in developing countries
Authors: Denny Patrick
Published: May 2018

In developing countries, the wise use of natural and artificial wetlands for water purification is particularly valuable and exploitable for the protection of water quality in catchments, rivers and lakes. Constructed wetlands are potentially good, low-cost, appropriate technological treatment systems for domestic wastewater in rural areas. Better still, they can be integrated into agricultural and fish production systems where the products are useable and/or re-cycled for optimal efficiency. However, currently, constructed wetlands are rarely installed. The reasons for this are discussed drawing attention to the limitations of aid programmes from donor countries and the need for in-house research, training and development. Recommendations for the development and wider use of constructed wetlands in developing countries are made.
Multiple data parameter identification for nonlinear conceptual models
Authors: Eberl Hermann , Khelil Amar , Wilderer Peter
Published: May 2018

A numerical method for the identification of parameters of nonlinear higher order differential equations is presented, which is based on the Levenberg-Marquardt algorithm. The estimation of the parameters can be performed by using several reference data sets simultaneously. This leads to a multicriteria optimization problem, which will be treated by using the Pareto optimality concept. In this paper, the emphasis is put on the presentation of the calibration method. As an example identification of the parameters of a nonlinear hydrological transport model for urban runoff is included, but the method can be applied to other problems as well.
Investigation of alternative method for nitrification in constructed wetlands
Authors: Green Michal , Friedler Eran , Ruskol Yuri , Safrai Iris
Published: May 2018

Nitrification of secondary effluent using a variant of the vertical flow bed system was investigated. In this vertical flow bed oxygen required for the nitrification process is supplied by a passive air pump. The passive air pump is based on a fill and draw cycle, where oxygen depleted air is removed from the system and fresh air is introduced. Each volume of effluent drained is displaced by an equal volume of fresh air. Experimental results of nitrification and the corresponding oxygen consumption show good agreement with theoretical calculations based on physico-chemical considerations.
Novel application of a back-propagation artificial neural network model formulated to predict algal bloom
Authors: Yabunaka Ken-ichi , Hosomi Masaaki , Murakami Akihiko
Published: May 2018

This paper describes the novel application of an artificial neural network (ANN) model based on the back-propagation method formulated to predict algal bloom by simulating the future growth of five phytoplankton species and the chlorophyll a concentration in the second largest lake in Japan: eutrophic freshwater Lake Kasumigaura. Comparison of observed and calculated values showed that (i) seasonal variations in the biomass of Microcystis spp. were well-predicted with respect to the timing and magnitude of algal bloom, and (ii) the concentration of chlorophyll a, as an indicator of the total biomass of phytoplankton, was well predicted in general. The resultant correlations for the other species, however, showed that model learning was insufficient to effectively predict species biomass; thereby indicating that some unknown factors which are not represented by the set of water quality parameters used as model input data affect phytoplankton growth. A sensitivity analysis performed on input parameters showed that chlorophyll a concentration was mainly affected by PO4-P concentration, while cyanobacteria and diatom species were affected by NO3-N and NH4-N concentrations, respectively. These results indicate that the “algal bloom” ANN model achieved reasonable effectiveness with respect to learning the relationship between the selected water quality parameters and algal bloom.
Microbial characteristics of constructed wetlands
Authors: Ottová Vlasta , Balcarová Jarmila , Vymazal Jan
Published: May 2018

Constructed wetlands have been shown to be capable of removing a wide variety of contaminants, including bacterial pollution. Wetlands are known to act as biofilters through a combination of physical, chemical and biological factors which all participate in the reduction of the number of bacteria. Five constructed wetlands in the Czech Republic were studied during 1994 and 1995 in order to determine removal of total and faecal coliform bacteria and Enterobacteriaceae. In addition, total count of aerobic and anaerobic bacteria were determined in water. Populations of nitrogen cycle bacteria were monitored on roots and rhizomes ofGlyceria maxima in the system at Doksy. The results revealed that the retention of coliform bacteria is very high and exceeds common retention values for conventional systems. The measurements also indicated that nitrifying bacteria were not present in wastewater, however, quite large numbers were found on the surface of roots and rhizomes of Glyceria. This fact can explain the significant nitrification observed in this system.
Reed stands in constructed wetlands: “edge effect” and photochemical efficiency of PS II in common reed
Authors: Urbanc-Bercic Olga , Gaberšcik Alenka
Published: May 2018

In this study an attempt has been made to estimate the vitality of the common reed (Phragmites australis) grown in the constructed wetland. The efficiency of solar radiation uptake of leaves was measured and terminal electron transport system (ETS) activity of roots was determined in specimens from different locations on the reed bed. The results showed that photochemical efficiency of PS II, expressed as FvFm ratio, was higher in plants growing in the middle of the well established stand, but it was lower in plants growing in the area permanently flooded with leachate, where plants were significantly lower. Potential respiration of roots on the vertical rhizome decreases with depth, while it showed slight variations when determined at the same depth, but in plants from different locations within three beds of RBTS.
Soil clogging in vertical flow reed beds – mechanisms, parameters, consequences and.......solutions?
Authors: Platzer Christoph , Mauch Klaus
Published: May 2018

The purification efficiency of vertical flow reed beds (VFB) is dependent on a very efficient soil aeration. In most systems this is achieved by intermittent pulse loading at the surface providing an oxygenation by mass flow and diffusion. These oxygen transportation mechanisms only function as long as the upper layers of the bed have a high drainage capacity. Purification efficiency drops significantly when constant ponding occurs.

A review of the literature on clogging in sand filters is given. In our evaluations the following observations are made. Clogging occurs only in the upper 0-15 cm of the bed. Clogging is dependent on the height of organic mass loading. The content of volatile solids in the upper layers could not be proven as a significant parameter influencing clogging. The infiltration rate can be restored by giving the beds a recovery period of several weeks. The required length of rest is dependent on weather conditions, winter is the most critical time.
The design and performance of a vertical flow reed bed for the treatment of high ammonia, low suspended solids organic effluents
Authors: Morris Michael , Herbert Robert
Published: May 2018

A design approach for vertical flow constructed wetlands based on selection of not only bed size, but also substrate characteristics, configuration, plant species/variety and management is piloted in a trial system to treat sugar beet processing wastes. In the beet processing season these wastes are hot, low in suspended solids and relatively high in ammoniacal nitrogen.

The pilot system consists of a small, coarse substrate first stage followed by a larger, fine substrate second stage. Results in the beet processing season show 87.3% COD removal, 87.7% TSS removal and a 79.5% reduction in ammoniacal nitrogen. Treating larger volumes of cooler stored wastes out of season, the mean removal efficiencies were 73.9% for COD, 88.0% for TSS and 93.4% for ammoniacal nitrogen.

TSS removal m−2 was found to be independent of influent concentration and temperature, whilst COD removal m−2 was found to be independent of temperature, but not influent concentration. Removal of ammoniacal nitrogen appeared to be dependent upon influent concentration and, in particular, upon temperature. Infiltration rates were shown to be negatively correlated to length of dosing cycle. Simple models of substrate permeability based on substrate particle size distribution are seen to be inadequate for describing infiltration rates in vertical downflow systems, even those treating low strength wastes.
Application of derived probability and dynamic programming techniques to planning regional stormwater management systems
Authors: Papa Fabian , Adams Barry J.
Published: May 2018

There exists a need on the part of land developers or municipalities responsible for stormwater servicing master planning to reduce the costs associated with the initial construction of stormwater facilities as well as with their operation and maintenance. Common integral components of stormwater control systems include stormwater management ponds for water quality control. These ponds may occupy valuable urban land and, hence, it is desirable to minimize the land coverage of these facilities while simultaneously satisfying water quality control objectives. The employment of optimization techniques in the planning and design process can thus play an important role by reducing the costs associated with the implementation of such facilities.

This paper presents an optimization methodology for single catchments using a single stormwater quality control pond. This methodology is then further developed for a multiple parallel catchment (each with a single pond upstream of its outlet) optimization procedure employing principles of dynamic programming. The principal constraint of the problem formulation is to meet a specified pollution control level at the outfall to a receiving water body. The optimization technique employs analytical probabilistic models for stormwater management planning and analysis which are in a mathematically closed form and thus easily integrated into an optimization framework. The costs explicitly considered are land-associated costs and construction costs. Operation and maintenance costs can be incorporated into the framework if desired.
The use of constructed wetland for landfill leachate treatment
Authors: Bulc Tjaša , Vrhovšek Danijel , Kukanja Vlasta
Published: May 2018

Based on data that none of the 53 registrated and 60 000 illegal landfill sites in Slovenia is properly structured, the landfill leachate is deemed to be one of the most serious pollution problems. A pilot constructed wetland (CW), as an innovative technology that provides simple and inexpensive waste water treatment was introduced for landfill leachate treatment at the Dragonja landfill site on the Adriatic coast. The system consists of two interconnected beds with a subsurface flow, covering an area of 450 m2. An average hydraulic load was 3 cm d−1. The influent concentrations were for COD 1264 mg l−1, BOD5 60 mg l−1, NH3-N 88 mg l−1, undissolved solids 400 mg l−1, and Fe 10 mg l−1. Monitoring of CW performance was initiated in 1992 by analysing physical, chemical and microbiological parameters. Evident reductions after the initial period have been achieved in COD (68%), BOD5 (46%), NH3-N (81%), Fe (80%), and bacteria (85%). The results show that CW was fairly efficient, although it was very difficult to determine the proper area especially because of specific hydraulic and pollution fluctuations. Therefore, further investigations should give more data on proper design.