bluuebunny/crossref_metadata_2025 huggingface dataset:
Groundwater as source of contamination for water supply in rapidly growing megacities of Asia: case of Karachi, Pakistan
Authors: Rahman Ausaf-ur
Published: May 2018

The development of essential services including water and sanitation in many megacities of the economically developing countries of Asia cannot keep pace with their rapidly growing population and accompanying urban and industrial development. The inadequate water supply and poor sanitation services lead to contamination of their water supply through the input of sewage water into groundwater. This paper examines the problem of contamination of water supply in Karachi, the largest city in Pakistan with a population of over 12 million and growing at 6 percent per annum. The paper presents the data on water quality from various sources, mainly municipal water supply, vendors and well water; the three major sources of water for domestic use in Karachi. Except municipal water from some areas and during certain periods, water from most other sources contains coliform bacteria, and in many cases faecal coliform, in amounts several magnitudes higher than any standards permit. Many samples have also been found to contain heavy metals including chromium, lead, nickel and arsenic in amounts excessive of permitted standards. The probable sources of contaminants for the various types of water (piped, vendors, wells) indicate that groundwater may be the main contributor. The very source of this groundwater is predominantly from sewage. The paper also evaluates the solutions that are being practised, proposed or may be feasible, as well as those that are evolving.
Natural bioremediation perspective for BTX-contaminated groundwater in Brazil: effect of ethanol
Authors: Corseuil Henry X. , Alvarez Pedro J. J.
Published: May 2018

Natural bioremediation, the use of indigenous microorganisms to degrade hazardous substances within aquifers without engineered stimulation, shows great promise as a cost-effective approach to hydrocarbon plume management. This technique requires thorough site characterization and monitoring to verify that the natural attenuation processes continue to provide adequate risk protection. Significant progress has been made towards understanding the hydrogeochemical and microbiological factors that influence the feasibility of natural bioremediation of fuel-contaminated aquifers in North America and Europe. Nevertheless, this experience should be extrapolated with care to contaminated sites in Brazil, where gasoline contains about 22% of ethanol. Preliminary laboratory studies show that ethanol can enhance the solubilization of BTX in water, and it might exert diauxic effects during BTX biodegradation. A better understanding of the biochemical, physical, and ecological effects of ethanol is needed to develop a rational basis for the selection, mathematical modeling, and monitoring of appropriate natural bioremediation systems in Brazil.
Dissolution of polycyclic aromatic hydrocarbons from weathered contaminated soil
Authors: Yeom I.-T. , Ghosh M. M. , Cox C. D. , Ahn K.-H.
Published: May 2018

Dissolution of PAHs from soil contaminated with multi-component coal tar was investigated using a polymeric adsorbent, Tenax-TA and a nonionic surfactant, Brij 30. Tenax created maximum concentration gradient at the soil/water interface, thus maximizing interfacial mass transfer. Even in the presence of Tenax, the release of PAHs from the weathered soil was a very slow, noneqilibrium process. The rate-limiting step in the release of PAH was identified as diffusional mass transfer within the contaminant-soil matrix. Based on model analyses, the key parameter controlling dissolution of PAHs from the soil was found to be the diffusivities of PAHs within the soil/tar matrix. Brij 30 solution (5.5 g/L) substantially increased the rate of PAH dissolution from the soil. The enhanced mass transfer rates of PAHs by Brij 30 were attributed to their enhanced matrix diffusivities rather than their increased aqueous solubilities. Matrix diffusivities of PAHs in Brij 30 solution increased by two orders of magnitude compared with those with Tenax. Swelling of the weathered tar matrix of the soil by infiltrating surfactant molecules was suggested as the mechanism responsible for the observed diffusivity enhancement.
The utilization efficiency of hydrogen peroxide on the removal of volatile organic acids in sand columns
Authors: Lu C.-J. , Fan L.-C. , Lee C. M.
Published: May 2018

Effects of hydrogen peroxide (H2O2) on the removal of volatile organic acids were studied with a series of sand columns. Hydrogen peroxide was used as an alternative oxygen source to enhance the removal of volatile organic acids. In the presence of microorganisms, H2O2 was readily decomposed to increase the dissolved oxygen concentrations (DO) in waters. The microorganisms used in this study could tolerate the toxicity of H2O2, even if its concentration reached 450 mg/L. The volatile organic acids used in this study were not chemically oxidized by H2O2. The results indicated that the concentrations of H2O2 required to remove volatile organic acids were higher than those calculated from the theoretical stoichiometry equation. Hydrogen peroxide was not effectively utilized, especially when the concentrations of H2O2 were relatively high. When the concentration of H2O2 was high, oxygen produced from the decomposition of H2O2 might not be effectively utilized by microorganisms and might escape from waters in gaseous form. The ratio of the amount of the volatile organic acid removed to the amount of H2O2 added decreased with an increase in the concentrations of H2O2. Multi-point injection of H2O2 can be used to improve its utilization efficiency, if a higher concentration of H2O2 was required.
Interactions between gems and indigenous microorganisms in aquatic ecosystem
Authors: Inamori Yuhei , Murakami Kazuhito , Sato Ruka , Tanaka Nobuyuki , Sudo Ryuichi , Kurihara Yasushi
Published: May 2018

This study was conducted to elucidate the interaction and biotic effect of indigenous microorganisms, especially micro animals and bacteria on prosperity and decay of GEMs (genetically engineered microorganisms). Bacterial interaction means competition for substrate to grow between GEMs and indigenous bacteria, and prey-predator interaction means effect of micro animals on survival of GEMs. So, it is considered that basic part of environmental effects of GEMs will be made clear with analysi of these phenomena. Escherichia coli HB101/pBR325 as GEM, its host strain E. coli HB101, and Bacillus cereus MC as one of dominant species of indigenous bacteria were supplied. As predator the micro animals,Tetrahymena thermophila (ciliata, filter feeder) and Aeolosoma hemprichi (oligochaeta, detritus feeder) were supplied. The results obtained from this study can be concluded as follows: 1) GEMs showed few potentials to beat their host strains in their growth competition; 2) predation of micro animals influenced equally GEMs and their host strains, and these microorganisms, such as bacteria, were expected to decrease in environment; 3) fluculation enabled GEMs to escape from predation of micro animals, but GEMs were not expected to survive long-term because various predator species of micro animals exist in environment; 4) effect of micro animals, especially their predation, on survival of GEMs was so important that more practical research should be conducted; 5) it suggests that the results obtained from this study can be used to establish regular guidelines for environmental release of GEMs such as bioremediation technologies.
Nutrient removal by water lettuce (Pisitia stratiotes)
Authors: Aoi T. , Hayashi T.
Published: May 2018

The nutrient uptake and growth rates of the water lettuce [Pisitia stratiotes] were investigated in a batch culture system and a continuous flow system. As the water hyacinth [Eichhornia crassipes] is well known and widely researched as an aquatic macrophyte, water hyacinths were used as a control in a batch culture system. It was found that the specific growth rate of water lettuce was slightly higher in dry season, and in rainy season the growth rate of water hyacinths decreased almost 70%, but the rate of water lettuce decreased only 45%. From this result, water lettuce is thought to be grow up enough even under low solar radiation. The nitrogen, phosphorus and ash contents of biomass were about 1.5 times higher in water hyacinths than in water lettuce (N:2.15% & 1.65%, P:1.67% & 1.03%, ash 19.6% & 19.9% respectively). As the biomass of water lettuce is not so big and heavy (wet weight of water lettuce was under 100g and the width and height of the plant was under 20cm), removal of surplus biomass from water bodies is easy. It was made clear that water lettuce is very effective for removing nutrient from water bodies.
Biological treatment of leachates from hazardous waste landfills using SBBR technology
Authors: Dollerer J. , Wilderer P. A.
Published: May 2018

Bench-scale experiments with two different types of fixed bed reactor have been conducted in order to investigate the potential of SBBr technology (Sequencing Batch Biofilm Reactor) for treatment of leachates from different hazardous waste landfills. Reactor A was equipped with a membrane oxygenatition system for bubble free transfer of oxygen into the bulk liquid. In constract, reactor B was bubble aerated.

The process was found to be remarkably stable. An average DOC removal rate of 68% was achieved with a 12-hour cycle. The emission of biodegradable volatile organic substances was observed to be significantly reduced by using bubble free aeration system.
Experiences and new developments in biological pretreatment and physical post-treatment of landfill leachate
Authors: Baumgarten G. , Seyfried C. F.
Published: May 2018

The leachate treatment plant of the landfill in Mechernich including biological pretreatment, reverse osmosis and evaporation and drying of the concentrate has been in operation since the beginning of 1994. Originally the plant was designed for a capacity of 130 m3/d. In the future, an average leachate amount of ca. 280 m3/d and even considerably higher montly peaks must be assumed. The necessary enlargement of the biological pretreatment will be realized by a second biological contactor plant. Corresponding to the operation of the existing plant a large amount of the ammonium can be eliminated under aerobic conditions by deammonification so no enlargement of the denitrification stage is needed. by simply replacing the reverse osmosis membranes by nanofiltration membranes, an operational capacity of ca. 280 m3/d may easily be achieved at the existing physical post-treatment stage. With the aid of this enlargement conception, the relatively high operational costs at present will be reduced considerably.
Hydrodynamic modeling of leachate recirculating landfills
Authors: McCreanor P. T. , Reinhart D. R.
Published: May 2018

Leachate recirculation is an emerging technology for the enhanced stabilization of active landfills and in-situ treatment of problematic landfills. A variety of researcher have documented the benefits of increasing landfill moisture content and liquid movement through the fill. However, little work has addressed the hydrodynamic characteristics of the recirculating landfill, specifically the effect of leachate flow rate and waste characteristics upon leachate routing. This paper presents the results of mathematical modeling of the horizontal infiltration trench and vertical infiltration well, two commonly employed leachate application methods. The results of transient unsaturated flow modeling are detailed.
Wastewater reclamation, recycling and reuse: past, present, and future
Authors: Asano Takashi , Levine Audrey D.
Published: May 2018

The scientific basis for the current status of wastewater reclamation, recycling and reuse has evolved from developments in water and wastewater engineering coupled with increasing pressures on water resources. Milestone events that have led to the safe use of reclaimed wastewater are reviewed. The role of engineered systems associated with reclaimed wastewater is discussed in the context of the natural hydrologic cycle. A synopsis of the significant studies that form the basis for current regulatory approaches and technological innovations is presented. Current water reclamation strategies incorporate multiple measures to minimize health and environmental risks associated with various reuse applications. A combination of source control, advanced treatment process flowschemes, and other engineering controls provides a sound basis for increased implementation of water reuse applications. The feasibility of producing reclaimed water of a specified quality to fulfill multiple water use objectives is now a reality due to the progressive evolution of technologies and risk assessment procedures. Future water reuse directions are charted.
The coming era of intensive wastewater reuse in the Mediterranean region
Authors: Shelef Gedaliah , Azov Yossi
Published: May 2018

Reuse of wastewater will intensify in the coming decades in the Mediterranean countries due to water shortage, the climatic conditions, the need for agricultural irrigation, the necessity of improving health and environmental conditions for the growing population as well as for the large tourists population. Reuse in agricultural irrigation of unrestricted crops as well as municipal uses of watering of public parks, sport fields and golf courses are of first priority. Groundwater recharge and toilet flushing in high-rise hotels and office buildings should be also considered in the near future. These reuses require considerable treatment and a high and uncompromising quality of effluent. A brief review of the current experience in various countries in the Mediterranean ranging from demonstration to full-scale plants is given. Some reuse schemes in Israel are briefly described as examples of the reuse trends and practices as well as some of the cost and economics of various reuse existing and proposed schemes.
Artificial wetlands for wastewater treatment, water reuse and wildlife in Queensland, Australia
Authors: Greenway Margaret , Simpson John S.
Published: May 2018

Queensland, Australia has a subtropical-tropical climate with dry winters and wet monsoonal summers. Arid climatic conditions prevail inland with hot dry days and cold nights. The climatic conditions are conducive to high plant growth rates and hence offer great potential for constructed wetlands for water pollution control. The water (a scarce resource during the dry season and in arid regions) can also be used to irrigate crops, playing fields, parks and gardens or golf courses. The water discharged from the wetlands is also of an acceptable quality to flow into estuarine and riverine environments. Many natural wetlands are only seasonally inundated and during the dry season wildlife has to seek alternative refuges. Artificial wetlands receiving sewage effluent provide permanent wildlife habitats and improve the landscape amenity. The Queensland government's Department of Primary Industries has initiated an Artificial Wetlands for Water Pollution Research Program. Under this scheme 10 experimental pilot artificial wetlands have been established and a further 6 university research projects are being conducted on various aspects of artificial wetlands including nutrient and heavy metal uptake and bioavailability in wetland plants, sediment biogeochemistry and mass balances. One gold mine rehabilitation project has an artificial wetland to treat mine leachate. This paper presents 3 case studies which include significant results with respect to wastewater polishing and re-use.
Recycled water – a source of potable water: City of San Diego health effects study
Authors: Olivieri Adam W. , Eisenberg Don M. , Cooper Robert C. , Tchobanoglous George , Gagliardo Paul
Published: May 2018

During the late 1980's and early 1990's the City of San Diego built and operated a 1,900 m3/d (0.5 Mgal/d) wastewater pilot facility to evaluate the efficacy of a unique combination of treatment methods for the reclamation of wastewater to a quality acceptable for human consumption. The primary objective of the study was to investigate if the City's advanced wastewater treatment system could reliably reduce the contaminants of concern to levels such that the health risks posed by an assumed potable use are no greater than those associated with the present water supply. The results of this substantial research effort indicated that the processes involved can reliably produce a water of equal or better quality than that of the present raw water supply.
Water reclamation and reuse criteria in the U.S.
Authors: Crook James , Surampalli Rao Y.
Published: May 2018

Increasing demands on water resources for domestic, commercial, industrial, and agricultural purposes have made water reclamation and reuse an attractive option for conserving and extending available water supplies. Also, many water reuse projects are implemented to eliminate a source of contamination in surface waters or as a least-cost alternative to meeting stringent discharge requirements. Reclaimed water applications range from pasture irrigation to augmentation of potable water supplies. Water reclamation and reuse criteria are principally directed at health protection. There are no federal regulations governing water reuse in the U.S.; hence, the regulatory burden rests with the individual states. This has resulted in differing standards among states that have developed criteria. This paper summarizes and compares the criteria from some states that have developed comprehensive regulations. Guidelines published by the US. EPA and the rationale behind them are presented for numerous types of reclaimed water applications.
Conceptual model for production and composition of exopolymers in biofilms
Authors: Nielsen Per Halkjær , Jahn Andreas , Palmgren Rikke
Published: May 2018

The presence and the transformations of organic fractions within biofilms are not usually included in biofilm models, mainly owing to the lack of knowledge of the important processes, the stoichiometry and the kinetics. A conceptual biofilm model taking into account microbial physiology with regard to production of extracellular polymers and their transformation within the biofilm is suggested. The suggested components in the biofilm are the cell biomass and the various extracellular polymeric substances (EPS), such as polysaccharides, protein, humic substances and nucleic acids. In addition, environmental factors that influence the microbial exopolymer production and composition are taken into account. The suggested conceptual model can be helpful in structuring the design and evaluation of biofilm experiments focusing on biofilm structure and properties.
Study of toluene degradation kinetics in a flat plate vapor phase bioreactor using oxygen microsensors
Authors: Villaverde S. , Mirpuri R. , Lewandowski Z. , Jones W.L.
Published: May 2018

The paper describes the toluene degradation process in a flat plate vapor phase bioreactor (VPBR) by a Pseudomonas putida 54G biofilm. Oxygen microelectrodes were used to measure oxygen concentration profiles through the gas, liquid, and biofilm phases. The linear shape of the dissolved oxygen concentration profile in the outer 87% of the biofilm thickness suggested an absence of reaction in this layer. Oxygen consumption in the remaining basal 13 % (0.3 mm) followed zero order kinetics with a rate constant of 102.2 g m−3 h−1, for toluene gas concentration of 1.5 g m−3.

The increase in respiratory activity near the substratum was confirmed by microscopic study of cryogenic biofilm sections, and the lack of activity in the surface film was interpreted as a consequence of injury exerted by the toxic substrate. The accumulation of dead cells on the top of the biofilm contributed a resistance to the transport of substrates to deeper layers of the biofilm suggesting a protective role of the outer layer against the harmful effect of the toxic. These results highlight a new conceptual biofilm model in which both microbial growth and inactivation are controlled by substrate transport, leading to a structure that itself controls substrate availability.
The effect of bacterial injury on toluene degradation and respiration rates in vapor phase bioreactors
Authors: Jones Warren L. , Mirpuri Rajesh G. , Villaverde Santiago , Lewandowski Zbigniew , Cunningham Alfred B.
Published: May 2018

The effects of prolonged toluene exposure and degradation on bacterial cultures of Pseudomonas putida 54G were investigated in three reactor systems: a batch suspended culture system, a bench-scale flat plate biofilm reactor, and a bench-scale packed column reactor. Humidified air containing 150 ppmv (toluene limiting) to 750 ppmv (oxygen limiting) toluene vapor was the sole source of carbon and energy supplied to these systems. Results from the suspended batch culture experiments were used to develop rate expressions and kinetic parameters for loss of culturability and of toluene degradative capacity. Experiments in the flat plate reactor were carried out to examine the effects of injury on biofilm structure and function. The packed column studies were performed under conditions relevant to field application, and confirmed results from the other two studies - that decreased culturability on toluene media correlated with decreased specific toluene degradation rate, particularly at higher toluene concentration.
Fluid bed biological nitrification and denitrification in high salinity wastewater
Authors: Vredenbregt Leo H. J. , Nielsen Karsten , Potma Andrea A. , Kristensen Gert Holm , Sund Christina
Published: May 2018

Wastewater from wet lime(stone)-gypsum flue gas desulphurisation (FGD) processes in coal-fired power plants contains nitrate. Where case selective catalytic reduction (SCR) of NOx is applied the wastewater can also contain ammonia. For the removal of both nitrate and ammonia, biological processes are an attractive option. A bottle-neck for application of biological processes might be the high chloride concentration and relatively high temperature of the wastewater. Therefore research work was performed in fluid-bed reactors at pilot-plant scale for both biological nitrification and denitrification. Biological nitrification was studied up to 34 gCl−/l and nitrite was the main product formed. Biological denitrification was effective up to at least 45 gCl−/l. Both nitrate and nitrite were removed effectively.
Effect of influent quality variability on biofilter operation
Authors: Le Tallec Xavier , Zeghal Slim , Vidal Alain , Lesouëf André
Published: May 2018

Fixed-film processes have been developed and are now widely used to upgrade or to build wastewater treatment plants adapted to very stringent standards, in situations where the existing technologies are unable to meet these objectives with acceptable cost and reliable operation (Rogalla et al., 1992). Often based on daily average samples, these standards may require compliance 95% of the time on grab samples. To satisfy such requirements, the biological processes have to ensure an acceptable outlet quality in spite of variable inlet quality and flow. In this study, the performance of the Biostyr® process used in the nitrification/denitrification design are assessed at very low ammonia outlet residuals with different inlet variability conditions.
Modelling the effect of oxygen concentration on nitrite accumulation in a biofilm airlift suspension reactor
Authors: Picioreanu C. , van Loosdrecht M. C. M. , Heijnen J. J.
Published: May 2018

For an integrated nitrification-denitrification process, nitrite formation in the aerobic stage leads to big savings. Recently experimental observations (Garrido et al., 1996) have shown that it is possible to obtain full ammonium conversion with approximately 50 % nitrate and 50 % nitrite in the effluent of a biofilm air-lift suspension reactor. With oxygen concentrations between 1 and 2 mg/l a maximum nitrite accumulation of 50 % was reached. Here we give a simple diffusion-reaction model describing these results. All the kinetic and mass transfer parameters were taken from the literature, except the mass transfer coefficient around the biofilm surface, which was fitted. The proposed model describes very well the measured data, despite the assumptions made. Using this model the influence of operational parameters was evaluated in order to establish ways to affect the NO2− concentration. None of these (surface loading, k1, pH) had a significant effect on the maximal NO2− accumulation. Controlling the oxygen concentration seems to be the most practical method to obtain optimal nitrification to nitrite in BAS reactors.
Denitrification with methanol in tertiary filtration at wastewater treatment plant Zürich-Werdhölzli
Authors: Koch G. , Siegrist H.
Published: May 2018

In co-ordination with the EU-guidelines the large wastewater treatment plants in Switzerland have to be extended with enhanced nitrogen removal. Denitrification in tertiary filtration is a cost-effective alternative to extended denitrification in the activated sludge system, which needs additional reactor volume. At the wastewater treatment plant Zürich-Werdhölzli full-scale experiments of denitrification with methanol in tertiary filtration were performed during a summer and a winter campaign of 4 months each. For this purpose one of the original 22 filter cells was equipped with a methanol dosage. At temperatures of 12-15°C rates of denitrification of about 1.0 kgN m−3 d−1 are attained. After main backwashing, denitrification is significantly reduced. Frequent backwashings (several times per day) led to methanol breakthroughs due to biofilm loss. The yield coefficient YCOD was 0.4 kg CODX kg−1 CODme. In spite of methanol dosage the quality of the filter effluent was very good during normal operation in the winter campaign. Accumulation of the nitrite intermediate product was observed in summer at temperatures of 20-22°C.
Treatment of municipal wastewater in a CIRCOX® airlift reactor with integrated denitrification
Authors: Frijters C. T. M. J. , Eikelboom D. H. , Mulder A. , Mulder R.
Published: May 2018

In this study it was investigated whether the CIRCOX® airlift technology with integrated denitrification was suitable to treat municipal wastewater. The standard CIRCOX® reactor was extended with an anoxic compartment. The sludge on carrier is circulated alternately over the anoxic and oxic compartments by means of an airlift pump. The study was performed in two pilot reactors, a standard CIRCOX® reactor and a CIRCOX® reactor with integrated denitrification. Concerning BOD conversion and nitrification, no differences between the two systems were observed. It was shown that both BOD and nitrogen were removed efficiently. In the effluent, mean soluble BOD concentrations of 7 mg/l were attained at varying COD loading rates. Nitrification was complete in both reactors at temperatures above 15°C and at COD conversion rates of more than 2.5 kg COD/m3/d. Nitrification rates below 15°C were higher as compared to a low loaded activated sludge system. Substrate conversion rates were found to be constant throughout the denitrifying reactor. Denitrification matched the rates theoretically feasible. This could be achieved by controlling the recirculation and the aeration in relation to the loading rate. It can be concluded that the denitrifying CIRCOX® airlift technology seems to be an interesting alternative to treat municipal wastewater.
Experiences of nitrogen and phosphorus removal in deep-bed filters in the Stockholm area
Authors: Jonsson Lena , Plaza Elzbieta , Hultman Bengt
Published: May 2018

Experimental studies of nutrient removal in a discontinuous downflow two-media filter on a pilot plant scale are described and compared with previously reported results from a continuous upflow filter (DynaSand) studied at full scale. Under controlled conditions both filters show low effluent values of total nitrogen and phosphorus. Removal mechanisms were more complex in the discontinuous downflow filter owing to the use of two media, deposition of sludge on the filter surface, and changes of the biological activity over time after backwashing. The discontinuous downflow filter was much influenced by the formation of nitrogen gas bubbles clogging the filter, while the influence of nitrogen gas formation in the DynaSand filter was minor. Multivariate methods were used to evaluate factors influencing nitrate and phosphate removal and the time passing before the filter became clogged.
Mechanisms of biofilm detachment in fluidized bed reactors
Authors: Nicolella Cristiano , Chiarle Stefania , Di Felice Renzo , Rovatti Mauro
Published: May 2018

Biofilm detachment in liquid fluidized bed biological reactors was investigated to point out how different mechanisms influence the process. Erosion due to liquid shear and abrasion due to collisions of particles were considered as possible mechanisms of biomass detachment in liquid fluidized beds. A dimensional analysis technique allowed the identification of the significant parameters affecting the process. The influence of these parameters was established on a lab-scale reactor. An empirical model was proposed to correlate the experimental data and to analyze the effect of some characteristic quantities, such as particle Reynolds number, biomass fraction, liquid shear stress and solid concentration, on the detachment rate. Detachment rate strongly increased with fluid velocity while, owing to modifications in biofilm structure and morphology during the biological growth, it slightly decreased with liquid shear stress.
Floc agglomeration and structuration by a specific talc mineral composition
Authors: Bidault A. , Clauss F. , Helaine D. , Balavoine C.
Published: May 2018

The quality of the effluent from a waste water treatment plant using the activated sludge process depends upon the bacteria flocculation efficiency. Intensive research work has been devoted to understanding flocculation phenomena and to correct disorders. The addition of very fine but dense talc particles to the aeration tank immediately improves floc formation and densifies the new flocs created. In the longer term, the fine talc particles improve floc structuration and form stable and strong flocs. This has been demonstrated by running a modified activated sludge through the high shear strength of pumps and hydrocyclones. These fine talc particles offer a solution to solve floc settleability problems which so frequently arise when biological disorders appear in waste water treatment plants. Two practical cases are presented.
Photocatalytic degradation of aromatic and alicyclic pollutants in water: by-products, pathways and mechanisms
Authors: Pichat Pierre
Published: May 2018

Pyridine, 1-2-dimethoxybenzene, morpholine and lindane are mineralized by the TiO2-UV process. In the studies briefly reviewed here, their intermediate products, in particular the aliphatics, were identified both to determine what are the compounds that may be left in the treated water and to increase our understanding of the photocatalytic pathways. In addition to the oxidation and cleavage of the bonds, H(Cl) atom addition (or transfer) and coupling reactions were found to occur, which illustrates the complexity of photocatalytic degradations. Moreover, a comparison of the primary products of quinoline degraded either by photocatalysis or by the photo-Fenton process (Fe ions-H2O2-UV) showed that OH° radicals are not the only active species involved in photocatalytic degradations. From the effects of adding superoxide dismutase, it was inferred thatin situ formed O2−o anion-radicals intervene chemically, possibly by reacting with quinoline cation-radicals generated via electron transfer from quinoline to TiO2.
Flocculation in presence of organic macromolecules of natural water and secondary effluents
Authors: Narkis Nava , Rebhun Menahem
Published: May 2018

Flocculation processes were studied in three types of water representing turbid natural surface water, controlled synthetic systems of reference clay minerals suspensions in the presence of humates and fulvates at various degrees of interactions, and municipal wastewater treatment plant effluents. These systems contain suspended and colloidal dispersed solids accompanied by organic substances in dissolved or colloidal form. The presence of organic anionic macromolecules and soluble organics in water affects flocculation processes by raising the flocculant demand appreciably and hence affects the final water quality. Extraction and elimination of the organics from natural suspended solids, and removal of soluble organics from effluents reduced the organic content, thus decreasing considerably the flocculant demand. The addition of the extracted and separated organics to pure clay dispersions increased accordingly the cationic polyelectrolyte flocculant demand.
Realistic coagulation mechanisms in the use of aluminium and iron(III) salts
Authors: Licskó István
Published: May 2018

The processes leading from coagulant feed to the development of flocs suited to solid-liquid phase separation are examined and analyzed in the light of available information and experimental data. It is concluded that at the relatively high buffering capacity (HCO3− concentration above 1.8 meg/L) and close to neutral pH values (7.0<pH<8.4) typically found in the surface waters of Hungary, flocs suited to solid-liquid phase separation develop from the coagulant added within a very short period of time (10-20 seconds). These flocs are not capable of changing the charge of the particles on the colloidal, quasi-colloidal, or destabilizing the dispersion. Between the hydrolysis of the coagulant and the development of large flocs, “short-lived” water soluble aluminium and iron(III) hydroxide complexes, metal hydroxide sols are formed, which also carry a positive charge. These latter two metal hydroxide types (which also exist for a brief period - a few seconds - only) are the ones capable of destabilizing the dispersion. The bond between the suspended solids to be removed and the metal hydroxide sols and water soluble metal hydroxide complexes must be established within this short period. Rapid mixing of the coagulant will ensure rapid hydrolysis of the coagulant, contact between the sols and the suspended solids and will retard the development of large flocs which are inactive in destabilizing the dispersion.
Wet air oxidation: kinetics of reaction, carbon dioxide equilibrium and reactor design - an overview
Authors: Debellefontaine H. , Cammas F. X. , Deiber G. , Foussard J. N. , Reilhac P.
Published: May 2018

Aqueous wastes containing organic pollutants can be efficiently treated by wet air oxidation (WAO), i.e. oxidation by molecular oxygen in the liquid phase, under high temperature (200 to 325°C) and pressure (up to 150 bar). In western Europe, only an handful of industrial plants are in operation. Most of them were designed by extrapolating results from pilot plants. Only a very few studies have been devoted to the scientific design of such reactors (bubble columns). This paper discusses what needs to be known for this scientific design. The usual design methods assume that the column is divided into a number of cells. Each cell is a perfectly mixed reactor connected with the contiguous cells. Reliable data and models are available for hydrodynamics (axial dispersion, gas hold up) and mass transfer. Data are also needed for the kinetics of chemical reactions and are available from numerous sources, but have not yet been generalised. The thermodynamics (fugacities and enthalpy) of the gas phase can be determined with the Peng Robinson equation of state, and the Henry law for the solubility of gases in water describes the equilibrium conditions. But additional data are needed for water solutions containing salts. This paper describes a method that allows such a determination to be made by establishing rigorous balances on a batch autoclave. At present, these data are being used to implement a computer program aimed at determining the performance of a wet air oxidation reactor depending on the various operating parameters. Some typical profiles within the reactor are presented, establishing that the pH of the solution is a very important parameter.
Degradation of herbicides (ametryn and isoproturon) during water disinfection by means of two oxidants (hypochlorite and chlorine dioxide)
Authors: Lopez A. , Mascolo G. , Tiravanti G. , Passino R.
Published: May 2018

The paper reports the results of an investigation aimed to find out the number and the chemical structures of byproducts which form during the reactions occurring in aqueous solution between two very common disinfectants, sodium hypochlorite (NaClO) and chlorine dioxide (ClO2), and two herbicides widely used in agriculture and frequently found in groundwaters: ametryn and isoproturon. Under controlled experimental conditions [T=20°C, pH=7, reaction-time = 48h, herbicide/disinfectant molar ratios: 0.05 and 0.05×10−2], ametryn reactions with chlorine dioxide much slower than with sodium hypochlorite, whereas the opposite trend has been observed for isoproturon. In any case, however, the higher the reagents concentration the faster the reactions. As for reaction byproducts, they have been detected by HPLC and identified by HPLC-MS. In particular, ametryn (R-S-CH3) reaction with NaClO gives rise to the consecutive formation of four derivatives: the sulphoxide (R-SO-CH3), the sulphone (R-SO2-CH3), the sulphonate ester (R-O-SO2-CH3) and its hydrolysis product (R-OH). Within the fixed reaction time (48h), ametryn reaction with ClO2 forms only the sulphoxide derivative (R-SO-CH3). As for isoproturon, it reacts with both oxidants forming aromatic-ring substituted derivatives. In particular, during the reactions with NaClO and ClO2, four and two (chlorinated and/or hydroxylated) derivatives are respectively formed.
Solar water treatment: principles and reactors
Authors: Goslich Roland , Dillert Ralf , Bahnemann Detlef
Published: May 2018

Solar detoxification of dichloroacetic acid (DCA) as a model compound was studied. Different types of reactors, either light-concentrating or non-concentrating were used and their advantages and disadvantages were compared and discussed. The influence of hydrogen peroxide and molecular oxygen on the degradation process was studied with this model compound.
Particle size analysis in primary and secondary waste water effluents
Authors: Neis U. , Tiehm A.
Published: May 2018

Primary and secondary effluents of three waste water treatment works were analyzed for the size distribution of particle mass, chemical oxygen demand (COD), and phosphorus. Fractionation of suspended solids was done by 0.1-8.0μm polycarbonate filters and 32-125μm sieves, respectively. Primary as well as secondary effluents exhibited characteristic differences in the size distribution curves. Particle size distributions in terms of particle mass could be represented by a power law function. Automatic measurement of particle size distribution by a laser scanning device (CIS-100) was evaluated. Especially low concentrated waste water suspensions proved to be susceptible to aggregation during analysis. Therefore repeated short time analysis of subsamples is recommended.
Photochemical elimination of phenols and cod in industrial wastewaters
Authors: Chen Jian , Rulkens Wim H. , Bruning Harry
Published: May 2018

It is demonstrated that toxic pollutants such as phenols in industrial wastewaters can be eliminated efficiently by photochemical methods using a combination of UV and heterogeneous photocatalyst, and combinations of UV, H2O2, and ferric compounds. The combination of UV and photocatalyst even decreases the COD of some of the toxic industrial wastewater around 60–70% in 1–4 hour treatment time depending on the source of the wastewater. The different combinations of UV (200 W high pressure mercury lamp, wavelength 313 ≤ λ ≤ 456 nm), magnetite or aluminium oxide (as photocatalyst), H2O2 and iron compounds (FeCl3, Fe(NH3)2(SO4)2, as Fenton reagent) were used in lab scale experiments to examine the elimination at aerated conditions of pure phenol in solutions (initial concentration = 25 ppm) and of substituted phenols and COD in industrial wastewaters originally from phenolic resin manufacture, oil refinement, shale oil dry distillation, and naphthenic acid production. The results clearly show the separate and combined effect of UV, Ferric compounds and H2O2 on the elimination of phenols and COD.
Chemical oxidation for the treatment of leachate-process comparison and results from full-scale plants
Authors: Steensen Martin
Published: May 2018

Before landfill leachate is discharged, extensive removal of organic substances is required which cannot be achieved by biological treatment only. Chemical oxidation has the advantage of the substances being almost completely converted. Hydrogen peroxide/UV, ozone and ozone/fixed bed catalyst processes were used for the purification of three biologically pre-treated leachates. With all processes sufficient purification levels were achieved. However, the required energy consumption is largest with the hydrogen peroxide/UV process. If chemical oxidation is combined with biological purification, the discharge quality can be increased at decreased oxidant consumption.
Oxidative degradation of AOX and COD by different advanced oxidation processes: a comparative study with two samples of a pharmaceutical wastewater
Authors: Höfl Claus , Sigl Gerhard , Specht Oliver , Wurdack Ilse , Wabner Dietrich
Published: May 2018

Using two samples of a pharmaceutical wastewater, the efficiency of three advanced oxidation processes (AOPs) (H2O2/UV, O3/UV and H2O2/Fe(II)) for the removal of adsorbable organic halogen (AOX) and chemical oxygen demand (COD) were compared on a laboratory scale. The AOX contents of these samples ranged from 3 to 5 mg/L. Generally the results showed that all three methods are suitable for the degradation of AOX and COD. UV irradiation involved a high selectivity for the degradation of AOX compared to COD. On the other hand, processes based on hydroxyl radicals were less selective but considerably more effective in COD degradation. This explains why the combined methods H2O2/UV and O3/UV lead both to a complete destruction of AOX and a large removal of COD. During ozone treatment – without UV radiation – a decrease of AOX was also observed, although to a lower degree. Using Fenton's reagent both AOX and COD could be removed almost completely. The reaction time needed for this kind of treatment was very low compared to the other two AOPs. O3/UV treatment showed the largest consumption of “activated” oxygen (AO) during COD degradation. H2O2/Fe(II) treatment required almost the same amount of AO as H2O2/UV.
Influence of ultrasonic field on structure and parameters of sewage sludge for dewatering process
Authors: Bien January B. , Kempa Edward S. , Bien Jurand D.
Published: May 2018

The paper discusses the results of experiments with ultrasound application. Ultrasound is applied to change the polyelectrolyte's structure. Presented results indicate that the ultrasonic field may be useful for sewage sludge dewatering.
Removal of substituted pyridines by combined ozonation/fluidized bed biofilm treatment
Authors: Stern Marco , Heinzle Elmar , Kut Oemer M. , Hungerbühler Konrad
Published: May 2018

3-Methylpyridine (MP) and 5-ethyl-2-methylpyridine (EMP) were quantitatively removed in batch ozonation. Formate, acetate and oxalate where detected as ozonation products representing only about 10% of the total organic carbon after 90% removal of MP. Only 30% of the nitrogen was detected as nitrate. 5 moles of ozone were needed per mol of MP removed but at this time dissolved organic carbon (DOC) was only reduced by 10%. EMP was initially oxidised much faster but the reduction of DOC was only 5% when EMP was removed by 90%. Only 15% of the nitrogen was converted to nitrate. Small amounts of formate, acetate and oxalate were accumulated. 4 moles of ozone were required to remove one mole of EMP. In continuous combined experiments, wastewater was fed to a fluidised bed biofilm reactor with a mixed culture. The liquid was circulated through an ozonation bubble column. Ozone supply was controlled to keep the dissolved ozone concentration at a low level in the oxidation reactor. Complete mineralisation of MP and extensive mineralisation of EMP was observed during the whole experiment. During adaptation of biomass the ozone requirement decreased from 10 mol mol−1 of MP oxidised to 4 mol mol−1.
Water treatment with a fixed bed catalytic ozonation process
Authors: Logemann F. P. , Annee J. H. J.
Published: May 2018

Progress in developing the fixed bed, catalytic ozonation process “ECOCLEAR” continues. Experimental evidence supports a reaction mechanism that predominantly takes place at the surface of the solid catalyst. This sets “ECOCLEAR” apart from all other advanced oxidation techniques which depend on the presence of ·OH radicals in the aqueous phase. The catalytic ozonation process requires less ozone, is substantially less affected by dissolved radical scavengers such as (bi)carbonates and is equally effective under both highly acidic conditions – when ·OH radicals are not formed – as well as under highly alkaline conditions. Results of industrial plants in operation are given.
Do macrophytes play a role in constructed treatment wetlands?
Authors: Brix Hans
Published: May 2018

The larger aquatic plants growing in wetlands are usually called macrophytes. These include aquatic vascular plants, aquatic mosses and some larger algae. The presence or absence of aquatic macrophytes is one of the characteristics used to define wetlands, and as such macrophytes are an indispensable component of these ecosystems. As the most important removal processes in constructed treatment wetlands are based on physical and microbial processes, the role of the macrophytes in these has been questioned. This paper summarizes how macrophytes influence the treatment processes in wetlands.

The most important functions of the macrophytes in relation to the treatment of wastewater are the physical effects the presence of the plants gives rise to. The macrophytes stabilise the surface of the beds, provide good conditions for physical filtration, prevent vertical flow systems from clogging, insulate the surface against frost during winter, and provide a huge surface area for attached microbial growth. Contrary to earlier belief, the growth of macrophytes does not increase the hydraulic conductivity of the substrate in soil-based subsurface flow constructed wetlands. The metabolism of the macrophytes affects the treatment processes to different extents depending on the type of the constructed wetland. Plant uptake of nutrients is only of quantitative importance in low-loaded systems (surface flow systems). Macrophyte mediated transfer of oxygen to the rhizosphere by leakage from roots increases aerobic degradation of organic matter and nitrification. The macrophytes have additional site-specific values by providing habitat for wildlife and making wastewater treatment systems aesthetically pleasing.
N- and COD-removal in vertical-flow systems
Authors: von Felde Katrin , Kunst Sabine
Published: May 2018

Examination of COD-degradation and N-conversion within vertical flow systems and determination of influencing factors was done on constructed wetlands as well as on unplanted soil columns at laboratory scale. Topics of investigation were influent and effluent concentrations and removal efficiency of vertical flow beds, soil water composition at different depths and N-conversion activity with different operating methods, different hydraulic loadings (50, 100, 150 mm/d) and different soil materials.

The extent of degradation and conversion are especially determined by O2-supply which can be influenced by operating method, hydraulic loading and soil material.

COD-degradation and N-conversion take mainly place in soil depths down to 20 cm depending on the O2-supply and soil material. In general a sufficient O2-supply in an intermittently loaded vertical flow bed leads to a COD- and NH4-reduction ≥ 90% and prevents a Ntot-degradation of more than 50%. The determination of N-conversion activities of different soil samples has shown that nitrification activity as well as nitrate reductase activity have their maximum in soil depths down to 10 cm.