bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of O·− and O3·− in alkaline aqueous solutions
Authors: Gonzalez Mónica C. , Mártire Daniel O.
Published: May 2018

In aerated solutions containing molecular oxygen, O·− radicals effectively react with O2 yielding ozonide radical ions, O3·−. In the absence of O·− scavengers, O3·− mainly decays by unimolecular reaction yielding O·− and O2 and by further reaction with O·−. The decay rate of O3·− is therefore extremely sensitive to the presence of small quantities of ·− scavengers. In the present communication we have generated O3·− radicals by two different methods: photolysis of strong alkaline (pH > 12.7) solutions of either H2O2 or S2O8=. A detailed kinetic study shows a first order decay of O3·− generated after photolysis of hydrogen peroxide, while a more complex kinetics is observed when O3·− is formed following photolysis of S2O8=. These observations indicate the involvement of different reaction mechanisms. In order to obtain a complete interpretation of the experimental data, ab-initio kinetic computer simulations were done.

On one hand, the decay kinetics of O3·− generated from alkaline photolysis of H2O2 in the presence and absence of scavengers was well fitted by the ab-initio kinetic computer simulations. From the analysis of the mechanism, information on the reaction kinetics of the hydroxyl radicals with different substrates can be obtained. The possibility of retrieving information on the reaction kinetics and efficiency of these substrates as O·− and HO· scavengers, is exemplified for cyanide and carbonate ions.

On the other hand, the decay kinetics of O3·− generated from alkaline photolysis of K2S2O8 can only be understood if the participation of reaction intermediates other than SO4.·−, O·− / HO·, and O2·− are considered. Alternative reaction mechanisms are discussed.
Some effects of particle size in separation processes involving colloids
Authors: O'Melia Charles R. , Hahn Melinda W. , Chen Cheng-Tyng
Published: May 2018

The size of colloidal particles has long been considered to be a major factor in their mass transport in aquatic environments. In aggregation and deposition reactions, the mass transport rates of colloidal particles are expected to decrease with increasing particle size since thermal diffusion dominates this process. Particle size has also been considered to affect colloid chemical interactions, at least on theoretical grounds, with predicted rates of attachment in aggregation and deposition processes decreasing substantially as colloidal particle size is increased. Observations have failed to confirm this prediction. The situation becomes more complex and predictions more consistent with observations when reversible aggregation and deposition such as can occur in secondary minima are considered. This is done in this paper in simulations using a combination of Brownian dynamics and Monte Carlo (BDMC) techniques. Some experimental observations of virus transport in porous media are presented. The BDMC simulations provide a partial explanation for these results.
Oxidation reactors for water and wastewater treatment
Authors: Yue Po Lock
Published: May 2018

The essential issues in the design of oxidation reactors for water and wastewater treatment are highlighted in this paper. Examples of novel reactor design and typical results of water and wastewater treatment by various oxidation processes are given. The design of a laminar flow falling film photoreactor is illustrated.
Photochemical decomposition of 2,4-dichlorophenoxy acetic acid (2,4-D) in aqueous solution. II. Reactor modeling and verification
Authors: Martín Carlos A. , Cabrera María I. , Alfano Orlando M. , Cassano Alberto E.
Published: May 2018

An annular flow photoreactor for the direct photolysis of 2,4-dichlorophenoxyacetic acid has been developed, mathematically modeled and experimentally verified in a bench scale apparatus. The model employs a very simple kinetic equation that was previously obtained in a well stirred tank, batch laboratory reactor. Reasonably good agreement has been obtained between model predictions and experimental results. The observed errors are mainly due to the fact that the kinetics of this very complex reaction have been modeled in terms of just one single concentration.
An approach to particulate matter transfer studies in littoral zones of lakes with changing morphometry
Authors: Shteinman Boris S. , Parparov Arkadi S.
Published: May 2018

An experimental approach based on combined usAgE of the fluorescent tracers, sediment traps and measurements of the parameters of the water mass motion enabled us to reveal the main features of bottom sediment transport in the littoral zone of Lake Kinneret, depending on granulometry, wave activities, and bottom slope. Direct observations of resuspension events at different layers of the stratified water column indicate existence of water mass movements capable to cause resuspension of bottom sediments of different origin (sands and silts). Based on analysis of the heterogeneity of the vertical distribution of the resuspension, we proposed two mechanisms of resuspended particle transfer in a stratified water mass.
Activated sludge process control via particle monitoring
Authors: Jiwani Ashifa , Graham Nigel J. D. , Day Martin C.
Published: May 2018

The interrelationships between activated sludge plant operation and floc characteristics were examined in order to determine process control mechanisms for the effective treatment of domestic wastewaters and surplus activated sludge. A quantitative indicator of the physiological floc characteristics was developed and termed the morphological index. This may be evaluated by plant operators using a simple assessment form and matching photographic guide of various floc structures. The morphological index and floc size distribution were found to be useful tools for activated sludge process control and monitoring the dewaterability of surplus activated sludge.

It was found that floc size, morphology and in turn the dewaterability of surplus activated sludge varied with different operating conditions. Hydraulic retention times (HRTs) of < 10 hours and sludge ages of ≤8 days, resulted in the presence of small diffuse floc structures in the mixed liquor. The effluent quality was poor and the activated sludge had unfavourable filtering and dewatering properties. Switching plant operation to sludge ages in the region of ≥8 days and HRTs of ≥10 hours, was found to improve effluent quality and the dewaterability of surplus activated sludge. Here the flocs were large compact structures with short filaments protruding from the floc body.
Laboratory studies on enhancement of granulation in the anaerobic sequencing batch reactor
Authors: Wirtz Randall A. , Dague Richard R.
Published: May 2018

The phenomenon of granulation was studied in anaerobic sequencing batch reactors (ASBRs) treating a synthetic sucrose wastewater. The objective was to study methods of minimizing the time typically required for start-up of high rate anaerobic processes, such as the ASBR, when utilizing biomass from typical anaerobic digesters. More specifically, the goal was to develop granular biomass soon after initial start-up of the ASBR in order to decrease the overall time required to achieve high rate anaerobic treatment. Laboratory-scale ASBRs were seeded with anaerobically digested municipal biosolids and operated until granulation was observed. Granule development was measured by determination of the average particle diameter of a representative sample of biosolids from the ASBRs. Cationic polymer was added to the test ASBR to enhance rapid granule development and to aid in start-up. Cationic polymer addition reduced the time required to form granules by approximately 75 % compared to an un-enhanced control ASBR.
Destruction of pollutants in industrial rinse waters by advanced oxidation processes
Authors: Luck F. , Djafer M. , Karpel Vel Leitner N. , Gombert B. , Legube B.
Published: May 2018

Recycling process water is a growing need for a variety of industries faced with increasing water costs and environmental constraints. Metal finishing activities such as printed circuit board (PCB) manufacturing generate large volumes of rinse water slightly contaminated with inorganic chemicals and organic additives. While the former can be removed with proven technologies, there is a need for effective processes for elimination of trace organics in order to allow recycling of rinse water without negative impact on process bath quality.

A cooperative research project started recently to study a water recycling process adapted to this need, able to remove 95% of the Chemical Oxygen Demand (COD) of the rinse water by combining proven membrane separation with an innovative chemical oxidation. Two types of advanced oxidations based on the conjunction of heterogeneous catalysts with oxidants will be specifically investigated.

In a preliminary stage of the project, the experimental tests were performed with a set of model compounds, selected from among the chemicals most frequently used in the plating processes, namely chelating agents, surfactants and corrosion inhibitors. These compounds were oxidized comparatively by ozone and catalytic ozonation. The differences between standard oxidation and catalytic oxidation are presented and discussed.
Catalytic wet air oxidation of dyeing and printing wastewater
Authors: Lei L. , Hu X. , Chu H. P. , Chen G. , Yue P. L.
Published: May 2018

The treatment of dyeing and printing wastewater from the textile industry by oxidation was studied. The reaction was carried out in a two-litre high pressure reactor. In order to promote the oxidation of organic pollutants present in the wastewater, experiments were conducted using various catalysts including metal salts, metal oxides, and porous alumina supported metals. All catalysts tested were able to enhance the conversion of organic compounds in wastewater, shorten the reaction time, and lower the reaction temperature. The alumina supported catalyst has an advantage over other catalysts in that it can be easily separated from the treated wastewater by filtration and recycled. The conditions in preparing the catalyst supported by porous alumina were experimentally optimised.
Applying systems analysis in managing the water environment: towards a new agenda
Authors: Beck M. B.
Published: May 2018

The methods of systems analysis - principally, mathematical modelling, simulation, and optimisation - have been widely applied to solving problems in managing the water environment for over three decades. These foundations of the subject remain just as relevant today as hitherto. The problems to which they might be applied, however, or the context in which they might be applied, seem to have changed in ways that could genuinely be described as “radical”. In this survey stock is taken of these changes in perspective, especially over the past ten years: in the emergence of stakeholder participation, environmental ethics, life-cycle analysis, sustainability, industrial ecology, and design for ecological (as opposed to engineering) resilience. Whether the application of systems analysis will require a new approach or new methods with which to address these new issues, is thus open to question. For there are undoubtedly limits of method now discernible, even in respect of the more conventional problems of applying systems analysis to managing water quality. For example, we shall be obliged to acknowledge that, were we to encode all our currently available hypothetical knowledge into a model, this would not be verifiable in the conventional, rigorous sense. Similarly, in spite of a wealth of apparently ever more powerful mathematical formulations of the problem of optimisation, heuristics and intuition must still be called upon to reach even good solutions, reasonably close to where the optimum is thought to lie. Circumventing such methodological difficulties, while yet absorbing the changing currents in outlook on the man-environment relationship, is where candidate tasks for the “new agenda” of the next few years might be found. This paper presents some personal observations on a handful of such candidate tasks.
Two strategies for advanced nitrogen elimination in vertical flow constructed wetlands
Authors: Laber Johannes , Perfler Reinhard , Haberl Raimund
Published: May 2018

Since 1991 the institute for water provision has run two vertical flow constructed wetlands for domestic wastewater treatment at two farm houses (8 p.e.) in Upper Austria. The systems are designed for elimination of organic compounds and for nitrification which was no problem even under winter conditions. In 1995 two methods were tested to achieve denitrification also in both systems. System A is a one-stage system, system B has two stages operated in series. The approach to the one-stage system consisted in pumping a part of the nitrified effluent from the soil filter back to the settling tank of the influent, where the raw wastewater mixes with the nitrified effluent-water. The approach to the two-stage system B consisted in adding an external carbon source (methanol) into the second, water saturated stage. The research was undertaken during several experimental stages to test the influence of the recirculation ratio (system A) respectively of the feeding (system B; intermittent, continuous, batch). The highest elimination rates could be achieved with system B (dosage of methanol) during experimental stage 1 (intermittent loading four times a day). The mean elimination rates were 82% for Ninorg and 78% for TN. The TN elimination performance of system A was only a little lower (72%). The elimination of COD, BOD5 and TOC was no problem throughout the whole experimental period (effluent concentrations of both systems were well below the Austrian standards).
Modeling error identification of activated sludge models
Authors: Yuan Zhigou , Vanrolleghem Peter A. , Vansteenkiste Ghislain C.
Published: May 2018

Information about the location of modeling erros is crucial for the efficient improvement of an invalid model. This article discusses how to pinpoint modeling errors through comparison of experimental data with data obtained through simulation of the invalid model. An observer-based approach is presented. By designing a dedicated observer for the system using the invalid model, a signal vector is generated, on which each modeling error imposes an easily identifiable feature. An algorithm to analyze the featured signal is then presented. With this algorithm, the features of each of the modeling errors are extracted. The approach is illustrated for a denitrification reactor model in which errors in the dimension of the state vector, in the structure of the biokinetic relationship and in the values of the parameters could be identified.
Horizontal subsurface flow systems in the german speaking countries: summary of long-term scientific and practical experiences; recommendations
Authors: Geller Gunther
Published: May 2018

There are now more than 15 years of experience with horizontal subsurface flow systems in the German speaking countries, covering the results of research projects and also that of practical daily maintenance. Till now some 50 - 100 horizontal flow systems with more than 50 pe in the German speaking countries are built. Approximately half of these use sand as filter material. The results show that the purification efficiency of these systems is in the order of that of good working conventional sewage plants, not only for BOD5 and COD, but also for nitrogen and phosphorus. Very high elimination efficiencies far better than 90% for BOD, COD and P are easily possible; similarly for elimination of N, when loading rates are below 20 mm/d, or the area is larger than 10 m2/pe. Generally there seem to be few problems with winter time and with clogging. The operation of these systems is easy and inexpensive. In nearly all reed beds Phragmites was predominant after a few years. For the planting of Phragmites an easy method using halm-cuttings is given. The long term experience with the reported systems allows us to give recommendations for design, construction and maintenance.
Constructed wetlands and nature conservation
Authors: Worrall P. , Peberdy K. J. , Millett M. C.
Published: May 2018

By reference to examples in the UK this paper examines the wildlife potential of reedbed treatment systems, both in their ability to act as pollutant buffers to protect or create downstream wetlands of conservation importance and as wildlife resources in their own right.

The constraints of size, structural diversity, pollution stresses and design criteria of constructed wetlands are evaluated in terms of wildlife conservation opportunities, and the more stringent water quality requirements for wildlife functions are discussed.

As a case study example, the paper examines in detail the South Finger Reedbed developed by The Wildfowl & Wetlands Trust. This system has been designed with the dual objectives of improving the quality of effluent from a large collection of captive wildfowl in order to buffer sensitive downstream wetlands and of creating a wetland habitat of nature conservation value. The performance of this system, constructed in 1993, indicates good treatment levels, with suspended solids reduction around 80% and BOD generally above 60%. In terms of wildlife performance the system rapidly evolved to support a broad range of vertebrate and invertebrate species.

The paper concludes that constructed wetlands for waste water treatment can be designed and managed to achieve optimal wildlife potential if approached from an ecological perspective as opposed to a strictly engineering viewpoint.
The design and performance of a nitrifying vertical-flow reed bed treatment system
Authors: Cooper Paul , Smith Mark , Maynard Henrietta
Published: May 2018

The paper describes the design, construction and the monitoring of a vertical-flow Reed Bed Treatment System (RBTS) which achieves tertiary nitrification of the effluent from a biological filter, treating the sewage flow from a population of about 200 people. It treats the flows from toilets, kitchen laboratories and a saline wastewater. The RBTS system takes effluent from an old biological filter and produces a nitrified effluent from a two-stage intermittently-dosed system. The paper shows the long-term performance of the system over a 4 year period and also describes experiments to assess the nitrification performance using a step-feed of ammonium nitrate solution. The system shows a removal of 8-13 g NH4-N/m3 of bed day. The design basis is shown and the operational features described.
Asymptotic observers as a tool for modelling process dynamics
Authors: Dochain D. , Agathos S. N. , Vanrolleghem P.
Published: May 2018

This paper deals with the dynamical modelling of processes with a special emphasis on wastewater treatment. Dynamical process modelling is usually derived from mass balance considerations and results in models which contain two types of terms representing the hydrodynamics and transport dynamics, and the conversion due to the involved (bio)chemical reactions involved, respectively. The conversion terms are indeed generally speaking the products of two terms: a yield coefficient and a reaction rate (strictly speaking, the kinetics). The latter usually concentrates a predominant part of the model uncertainty. The bioprocess model building exercise is usually global in the sense that it concerns all the terms involved in the model. In addition to the inherent bioprocess modelling difficulties (model complexity, data scarcity), this makes the interpretation of the model identification results difficult if not questionable. In this paper it is suggested how to use asymptotic observers to model and validate reaction schemes independently of the reaction kinetics. The results will be illustrated with two wastewater treatment processes: an activated sludge process and a detoxification reactor.
Long term performance of the sand-plant-filter Schattweid (Switzerland)
Authors: Schönborn Andreas , Züst Brigitta , Underwood Evelyn
Published: May 2018

The human waste concept of the Centre for Applied Ecology Schattweid, Switzerland combines treatment of feces in compost toilets and a constructed wetland for the liquid wastes. The wastewater of 5.1 population equivalents (greywater and urine) is treated in a two chambered settling tank followed by an underground vertical flow sand filter and a horizontal flow constructed wetland. The wastewater system has been in operation since 1985. Its performance has been monitored on COD, NH4-N, NO3-N, NO2-N, Total-P and Total-N almost monthly since then, and on other parameters (Total-Fe, Cl) occasionally.

COD elimination (91.4 %) and Total-P removal (90.6%) were stable over the years, whereas NH4-N and Total-N elimination have improved markedly from around 55% to 93.0% (NH4-N) and 80.0% (Total-N). Performance in winter was excellent. The addition of an easily degradable carbon source to the plant filter in summer 1991 led to a markedly decreased phosphorus retention and a washout of iron during the experiment.
The effects of uncertainties on the control performance of sewer networks
Authors: Méthot Jean-François , Pleau Martin
Published: May 2018

The effects of uncertainties on the performance of a Certainty Equivalent Open Loop Feedback Control approach is investigated throughout simulations of the Quebec Urban Community Sewer Network. The optimization algorithm is based on nonlinear programming with the peculiarity that all the constraints are linear. The hydraulic routine is a Linear Time Invariant (LTI) model associated to a Kalman filter. Preliminary results show the benefit of adding a filtering action to guarantee robust performance in the presence of measurement errors and model mismatch. The selected control scheme seems to be a good compromise between the short computational time required for Real Time Control applications and the high performance expected in the presence of uncertainties.
A prototype small swine waste treatment system for land limited and tropical application
Authors: Yang P. Y. , Khan E. , Gan G. , Paquin D. , Liang T.
Published: May 2018

A prototype of a 300-pig waste treatment system was constructed at the animal research farm of the University of Hawaii. The system includes a solid/liquid separation (12 m3), two anaerobic reactors (10 m3 each), one aeration unit (20 m3) and one combined rock bed filter with the aquatic plant reactor (20 m3). Based on the current results of a 240-pig operation, the methane gas production and TS reduction are 0.75 m3/m3/day and 72.7%, respectively, at the loading rate of 3.09 kg TS/m3/day. The aeration unit provides a TCOD and NH3-N reduction of 94% and 91%, respectively. The rock filter achieves a TCOD, NH3-N and NO3-N reduction of 32.8%, 26.8% and 68.4%, respectively. The annual cost for each of the treatment component is presented. It is very useful for the application of each treatment unit for the various needs of each pig farm.
Performance of clinoptilolite alone and in combination with sand filters for the removal of ammonia peaks from domestic wastewater
Authors: Baykal Bilsen Beler , Guven Didem Akca
Published: May 2018

Ion exchange using clinoptilolite for the removal of peak concentrations of ammonia from domestic wastewater as a second stage, by itself and in combination with sand filters, is evaluated. It is observed that there is no significant loss of capacity of clinoptilolite when placed in sand filters. All three configurations studied are successful in the removal of peak concentrations of ammonia, and hence can be used as a polishing unit, to comply with the demands of stringent standards. Among those investigated, the combined scheme, with clinoptilolite and aerated sand filters where biological activity is enhanced, is found to be the most effective provided that sufficient time for the development of nitrifiers are allowed. The performance loss of the clinoptilolite was observed to be 10% after 10 cycles of regular operation and regeneration.
Effects of molecular oxygen on GAC adsorption of energetics
Authors: VanderLoop Sarah L. , Suidan Makram T. , Berchtold Sandra R. , Moteleb Moustafa A. , Maloney Stephen W.
Published: May 2018

Munitions wastewaters are commonly treated by granular activated carbon (GAC) adsorption followed by incineration of the spent carbon. The design of effective GAC unit processes hinges on the knowledge of GAC adsorption capacity for the compounds of interest as well as the types of chemical interactions to expect. GAC can often catalyze polymerization or chemical degradation of the adsorbate in the presence of molecular oxygen. Some adsorbates, though less common, may be subject to catalytic activity even when no molecular oxygen is present. The products of these interactions may enhance or interfere with effective waste treatment. This study individually evaluated the adsorption properties of a variety of energetics compounds. A number of surface catalyzed polymerization and degradation reactions were noted.
Origin of trihalomethane (THM) precursors in Kurose River, Hiroshima, Japan
Authors: Galapate Ritchelita P. , Kitanaka Atsushi , Ito Kazuaki , Mukai Tetsuo , Shoto Eiji , Okada Mitsumasa
Published: May 2018

Origin of trihalomethane (THM) precursors in Kurose River, one of the sources of potable water in Hiroshima Prefecture, were investigated. THM formation potential (THMFP) at different stations of the river and the contribution from point and nonpoint sources within the river basin were determined. Contributions from both wet and dry precipitations were also evaluated. UV 260, DOC and THMFP were relatively high in water samples collected from stations where inflows of industrial effluents, domestic wastewater and agricultural drains were in the vicinity. Low values were noted at stations near wooded areas. However significant increase in UV 260, DOC and THMFP were observed in the presence of stormwater runoffs which is attributed to water soluble organic substances extracted from forest litter and top soil. The results indicate that the THM precursors in Kurose River could be attributed mainly to industrial effluents, domestic wastewater and agricultural drains. In case of rain, stormwater runoffs contributed significant amounts of THM precursors to the river.
Effects of flow velocity and depth on the rates of reaeration and bod removal in a shallow open channel
Authors: Leu Horng-Guang , Ouyang C. F. , Pai Tze-Yi
Published: May 2018

This study developed an analytical solution of reaeration rate coefficient (K2) and modified the equation of BOD removal in a shallow artificial open channel. A series of well-controlled batch tests were carried out to measure the K2 and BOD removal rate in the channel at different flow conditions. The results of these tests indicated that measured K2 within the developing zone of the laminar boundary layer is better described by the analytical solution of this study than by the five semi-empirical formulae mentioned in this paper. On the other hand, a resuspension-sedimentation coefficient, Rs, was added to the BOD removal equation to describe the variation in BOD due to varied flow conditions. Based on the results of the experimental data the following conclusions in the BOD removal process were reached. It was found that a direct correlation exists between the flow velocity to depth ratio (U/h) and the deoxygenation rate coefficient (K1), but there is an inverse correlation between U/h and Rs as well. This modified BOD removal equation can predict BOD removal rate at different travel times or known downstream distances in an open channel under varied flow conditions.
Advanced biological enhanced nutrient removal processes by the addition of rotating biological contactors
Authors: Su Jau-Lang , Ouyang Chaio-Fuei
Published: May 2018

Advanced removal efficiency of organic carbon, phosphorus and nitrogen from municipal wastewater was achieved by using an anaerobic-anoxic-oxide (A2/O) process with the addition of fully and partially submerged RBC biofilms. The experiments were carried out in a range of F/M ratio 0.21 to 0.32 kg BOD/kg MLSS/d and at a various total hydraulic detention times (HRT), return activated sludge ratio (r) and mixed liquid recycle ratio (R). Another pilot plant A2/O process without adding RBC was conducted for control experiments. Compared with A2/O process, this new process could achieve a higher degree of nitrification rate without decreasing the removal efficiencies of organic carbon and phosphorus. The new process provides an environment for combining the long solid retention time (SRT) biofilm and the short SRT suspended activated sludge. This concept can resolve the conflict in SRT between nitrogen and phosphorus removal simultaneously. Correspondingly, the benefits of the new process are shorten the hydraulic detention time, progress the efficiency of nutrient removal, more stable for operation and more economic for required land cost.
Roles of baffles in waste stabilization ponds
Authors: Muttamara S. , Puetpaiboon U.
Published: May 2018

Performance of baffles in waste stabilization ponds (WSP) comprising laboratory-scale ponds with different number of baffles was evaluated. This study was aimed at promoting waste stabilization ponds practice for wastewater treatment in tropical countries by reducing the land area requirement through the use of baffles which increased the biofilm and biomass concentrations. The experiments started with the tracer study to find out the hydraulic characteristics of each pond. It was shown that the dispersion number decreased with increasing flow length and number of baffles, which indicates more plug flow conditions. The deviation of actual HRT from theoretical HRT was computed and the flow pattern suggested the existence of an optimum spacing of baffles in baffled waste stabilization pond (BWSP) units. The investigations by feeding with synthetic wastewater further revealed that more than 65% TN and 90% NH3-N removal were achieved at HRT of 5 days in 6-baffled pond which corresponds to the specific area of 35.20 m2/m3. TN and NH3-N removal was increasing with number of baffles in the BWSP units. COD removal increased with higher number of baffles with its maximum removal efficiency at 6 baffles. The computed COD removal encompassed first-order reactions of both suspended and biofilm biomass was higher than that without the biofilm biomass activity and agreed well with the observed data. Compared with normal WSP, BWSP gave higher TN, NH3-N and COD removal. The effluent SS concentrations from 6 baffled-pond were less than 20 mg/l at HRT of 3 days.
Organic wastewater treatment without greenhouse gas emission by photosynthetic bacteria
Authors: Nakajima F. , Kamiko N. , Yamamoto K.
Published: May 2018

High conversion of wastewater into biomass of photosynthetic bacteria was investigated. This biomass is possibly utilized as feed for fish or extraction source of PHA (polyhydroxyalkanoate). As a fundamental investigation, batch experiments were carried out using purple nonsulfur bacteria Rhodobacter sphaeroides to determine the growth rate and yield and to quantify CO2 release/uptake during substrate assimilation. The substrates used for this study were five kinds of VFA namely, acetate, propionate, n-butyrate, n-valeric acid and n-caproate. Growth rates for n-valeric acid and n-cvaproate were lower than those for other VFAs. Yields, defined as carbon in bacteria divided by removed organic carbon, for n-butyrate, n-valeric acid and n-caproate exceeded 1 due to simultaneous CO2 uptake and no net greenhouse gas emission. Maximum CO2 uptake was 17% of removed DOC (dissolved total organic carbon) in the case of n-valeric acid supplemented with 2.00 g/l of NaHCO3.
Exergy analysis and nutrient flows of various sewerage systems
Authors: Hellström Daniel , Kärrman Erik
Published: May 2018

There is an increasing demand for more sustainable sewerage systems. An important tool in the analysis of the sustainability of a sewerage system is exergy analysis. It is possible, by using an exergy analysis, to estimate the consumption of physical resources. In the present study, the demand on resources in the sewerage system of Bergsjon, a district of Göteborg, Sweden, was evaluated through exergy analysis. The case study included the existing system and two sewerage system alternatives. One important aspect of a sustainable sanitary system is nutrients recycling from sewage to agriculture. The exergy analysis has therefore been complemented with an analysis of the mass-flows of phosphorus and nitrogen. The study shows that the hypothetical calculated exergy consumption during operation will be lower in a system with local treatment and urine separation toilets compared with a conventional alternative. The amount of phosphorus that could be recycled is the same for the studied alternatives, but the amount of nitrogen that could be recycled is considerably higher for systems with urine separation techniques.
Treatment of a milkpowder/butter wastewater using the AAO activated sludge configuration
Authors: Donkin Michael J. , Russell John M.
Published: May 2018

A laboratory-scale nutrient removal activated sludge system, based on the AAO configuration, was used to treat a synthetic wastewater from a milkpowder/butter factory. In this system, substrate is fed to anaerobic and anoxic selectors in series with an aerobic reactor. Sludge is returned to the anaerobic selector, and mixed liquor from the aerobic reactor is recycled to the anoxic selector. The overall system is operated at an HRT of 7 days and a nominal sludge age of 20 days. This system was prone to prolonged bulking periods, with filamentous bacteria Sphaerotilus natans, Type 0411 and Haliscomenobacter hydrossis being identified in the mixed liquors, although effective clarifier operation prevented loss of suspended solids. Theory suggests that selectors may be used to circumvent low F:M bulking, and to bring about enhanced biological nutrient removal. An investigation of the initial design revealed that relatively high nitrite levels were present in the system, and a larger anoxic selector with an HRT of 820 minutes was substituted for the original one with an HRT of 48 minutes. This resulted in a decrease in nitrite and a equivalent increase in nitrate in the system. Overall nitrogen removal remained unchanged at 66%, and SVI levels did not improve. On resetting the anoxic selector to its original size, the effect was not reversed. Phosphorus removal efficiency was detrimentally affected by the anoxic sizing experiment (49% to 20%), and this may be linked to the raised level of nitrate in the system. COD removal efficiency remained excellent throughout the trial at over 90% removal.
Application of enzymatic activity measurements to biological phosphate removal from wastewater
Authors: Czerska Bernadetta , Miksch Korneliusz , Matsché Norbert , Franz Andreas
Published: May 2018

Activity measurements of enzymes have been used in the research. Properties of microorganism populations of activated sludge have been estimated by this method. During the experiments, the activity of the following enzymes catabolising polyphosphate changes were measured: polyphosphatases, adenylate kinase, AMP:PP phosphotransferase. In order to designate the phosphorous release and uptake rate, a batch test has been carried out together with the activity measurement. Activated sludge for the experiments was taken from three substantially different wastewater treatment plants (WWTP). The enzymatic activities of the activated sludges which come from different WWTP indicate a high ability of microorganisms to change polyphosphates. The interpretation of the results shows good correlations of polyphosphatase and AMP:PP phosphotransferase activity with the phosphate release rate. The results of the experiments indicate the suitability of the activity measurement for defining potential possibility of a microorganism population to carry out biological phosphate removal by the activated sludge method.
The impact of microbiological tools on mathematical modelling of biological wastewater treatment
Authors: Pollard P. C. , Münch E. v. , Lant P. A. , Greenfield P. F.
Published: May 2018

Biological systems are being used to treat an increasing range of complex wastes; domestic and industrial wastewaters containing nutrients and refractory organic compounds, soil sites and groundwater contaminated by organics, and organic solid residues. These treatment processes rely on micro-organisms and, more than ever before, must deliver higher quality outcomes at higher levels of reliability to protect the environment. At the same time, pressures to deliver cost-effective treatment have increased. The challenge for these biological treatment technologies and the associated engineering is to achieve the environmental and economic goals simultaneously. Mathematical modelling is an essential component in developing a detailed understanding of such processes, as well as design guidelines and suitable operating and control strategies.

This paper provides a brief summary of the development of mathematical models for biological waste treatment systems, why they have become increasingly complex and how certain microbiological tools can provide the experimental means to validate more complex segregated and structured models of biological behaviour. With a number of specific modelling examples in the field of wastewater treatment, we illustrate the potential of these modern microbiological tools and their implications for gaining an improved understanding of biological waste treatment.
Anaerobic treatment of complex wastewater and waste activated sludge – application of an upflow anaerobic solid removal (UASR) reactor for the removal and pre-hydrolysis of suspended COD
Authors: Zeeman Grietje , Sanders Wendy T. M. , Wang Kaijun Y. , Lettinga Gatze
Published: May 2018

The application of one phase anaerobic wastewater systems for the treatment of complex wastewaters containing high amounts of suspended solids or lipids is usually limited by accumulation of these compounds in the sludge bed. This accumulation reduces the solid retention time and methanogenic activity of the sludge. The aim of the presented research was to achieve removal of suspended solids or lipids in an Upflow Anaerobic Solids Removal reactor to make higher reactor loadings possible. Raw sewage, waste activated sludge and dairy wastewater were pre-treated in an UASR reactor. When treating the raw sewage at 17°C and 3.0 h HRT 65% of the suspended COD could be entrapped in the sludge bed. Treatment of 2 g COD/l waste activated sludge at 9.6h HRT and 20°C resulted in 98% removal of the suspended COD. In both cases only 6–7% acidification of the complex wastewater took place. Dairy wastewater consists of mainly dissolved and colloidal COD. The lipids are surrounded by a protein membrane. These proteins will precipitate at pH <4.6 resulting in co-precipitation of the lipids. At 20°C and 4.5h HRT 57% of the lactose present in the wastewater was acidified, resulting in a pH of 4.0 and 98% lipids removal. It was concluded that the UASR reactor can achieve very high removal efficiencies for CODss and lipids, yet the retained COD is just partly hydrolysed. The produced sludge can be post-digested at thermophilic or mesophilic conditions to produce methane gas.
Strategy for land application of sewage sludge in Norway
Authors: Paulsrud Bjarne , Nedland Kjell Terje
Published: May 2018

The Norwegian public health and environmental authorities have launched a regulation for sewage sludge handling and disposal aiming at increasing the amount of sludge to be utilised on land areas. The strategy for achieving this is to secure that only high quality sludge is being offered to agriculture and green areas; the two disposal routes acceptable for land application of sludge in Norway.

Most sewage treatment plants have experienced a considerable reduction in sludge heavy metals content during the last 15-20 years and the major reason for this is believed to be the continuous control of industrial effluents discharged to the municipal sewerage system and the implementation of cleaner technologies in the industry.

Health risks and odour nuisance from the sewage sludge will be almost eliminated by employing treatment processes with the main purpose of disinfection and stabilisation of the sludge.
Significance of pressure and recirculation in sludge thickening by dissolved air flotation
Authors: Tai Hak Chung , Doo Yeon Kim
Published: May 2018

An experimental study was conducted to identify the effect of each operating variable on the liquid-solids separation efficiency using a bench scale batch flotation system and waste activated sludge. Interpretation of the experimental results was performed by use of the characteristic constants of an empirical equation proposed. Minimum A/S ratio for reliable operation of dissolved air flotation should be greater than 0.009. However, unstable sludge rising took place at the initial clarification stage due to excessive shear and turbulence when the pressure was high in spite of high A/S ratio. The efficiency increased as the A/S ratio increased except a case of high pressure coupled with high A/S ratio. High recirculation flow with a saturator pressure less than 5 atm is recommended for stable and efficient operation. The pore size of a diffuser did not affect the thickening efficiency significantly. Concentration gradient of the float solids became larger as flotation continued. Skimming of a top layer or a long skimming interval is desirable for high thickening efficiency.
Processes for the removal of recalcitrant organics from industrial wastewaters
Authors: Gulyas H.
Published: May 2018

Processes that are suitable for the elimination of recalcitrant organics from industrial wastewaters are reviewed. Most advantageous are separation processes which enable not only reuse of the water phase but also the recycling of the wastewater constituents. Besides separation processes many degradative wastewater techniques are available. However, for the removal of recalcitrant organics biological processes (which are economically beneficial) cannot be chosen, but a variety of nonbiological degradative processes exist which can be divided into oxidative and reductive technologies. The latter are in the research and development state. The chemical oxidative treatment technologies comprise wastewater incineration and wet air oxidation for wastewaters with high organic concentrations, the so-called advanced oxidation processes (AOPs) as e.g. ozone/hydrogen peroxide which generate the nonselective but very powerful oxidant OH radical, and processes with other oxidants as e.g. Fe(VI) compounds or peroxodisulfate. Also electrochemical oxidation of organic wastewater constituents is possible. All degradative processes that do not lead to total mineralization of organic wastewater constituents may form transformation products which sometimes are more toxic than the original organic compounds.
Characterization and treatability studies of cigarette industry wastewaters: a case study
Authors: Bozarslan G. , Çelebi S. K. , Sengül F.
Published: May 2018

In this study, the wastewater of one of the cigarette factories in Izmir was characterized and treatability studies were done. The characterization studies of the wastewater showed that the COD, and the pH changes drastically. The chemical treatability studies of the influent wastewater were done by using Ca(OH)2, FeCl3 and Fenton Reagent. The optimum dose of FeCI3 was determined by jar tests. When using Ca(OH)2, the best flocculation, settling behaviour, and the highest COD removal occurred around pH 11. The optimum doses of Fenton Reagent (FeSO4 and H2O2) were determined. The supernatants of the previously chemically treated wastewaters were used for biological treatment. According to total COD removal efficiencies and the amount of sludge production during chemical treatment, FeCl3 was found to be the most economical and effective coagulant. Chemical treatment units were designed for a batch and a continuous system. The batch system has more advantages than a continuous system in this case.
Quantification of resin acids in CTMP (chemithermomechanical pulping) effluents using an enzyme-linked immunosorbent assay
Authors: Li K. , Serreqi A. , Breuil C. , Saddler J. N.
Published: May 2018

An enzyme-linked immunosorbent assay (ELISA) based on polyclonal antibodies was used to quantify resin acids in the effluents from a chemithermomechanical pulp (CTMP) mill. Using a direct ELISA format, with polyclonal antibodies immobilized on the plate, the assay had a 50% inhibition concentration (I50) of 49.7 ppb and a detection limit of 4.5 ppb. Good recoveries were obtained from DHA spiked buffer. CTMP effluents with different levels of resin acids were quantified and the ELISA data were shown to compare favourably with both total abietic type resin acids and total resin acids as determined by gas chromatography (GC).
Upgrading aerated lagoons at pulp and paper mills
Authors: Welander Thomas , Löfqvist Anders , Selmer Anders
Published: May 2018

The possibility of improving the efficiency of aerated lagoons treating pulp and paper industry effluents by introducing a support material for microbial growth was studied on a pilot plant scale. Two 20 m3 pilot plants were operated for approximately one year in parallel with full-scale aerated lagoons at two Swedish pulp and paper mills. A support material specifically developed for application in aerated lagoons was installed in the pilot plants. A considerably higher treatment efficiency was obtained in the pilot plants than in the full-scale lagoons. While 30-40% of the COD was removed in the full-scale lagoons, a COD-removal of 60-70% was achieved in the pilot plants. Phosphorus, an important discharge parameter at both mills, was removed to 60-70%, while the removal in the full scale lagoons was only 0-10%. The suspended solids in the treated effluent after clarification was around 20 mg/l.
Nitrogen in the effluent of the pulp and paper industry
Authors: Järvinen Risto
Published: May 2018

Nitrogen concentrations of effluent before and after treatment plant in two mills have been measured during five days time in a bleached kraft pulp mill and in a newsprint mill. In effluents before treatment the concentration of inorganic nitrogen was low but in the effluent of kraft pulping process, the main part is inorganic nitrogen. In effluent after treatment the concentration of inorganic nitrogen is low. After activated sludge treatment plant the concentration of dissolved organic nitrogen is about 0.6 mg/l and nitrogen in suspended solids determines fluctuation of nitrogen content in treated effluent. There is no need for biological nitrogen removal processes if the addition of nitrogen in the treatment is correct.
Dye removal using low cost adsorbents
Authors: Ramakrishna Konduru R. , Viraraghavan T.
Published: May 2018

Dyestuff production units and dyeing units have always had a pressing need for techniques that allow economical pretreatment for color in the effluent. The effectiveness of adsorption for dye removal from wastewaters has made it an ideal alternative to other expensive treatment options. The current paper deals with an investigation on four low-cost adsorbents locally available in Saskatchewan, Canada for dye removal. Peat, steel plant slag, bentonite clay and fly ash were utilized for this study and their performance evaluated against that of granular activated carbon. Batch kinetic and isotherm studies, and column studies were undertaken, and the data evaluated for compliance with the Langmuir, Freundlich and BET isotherm models. Synthetic dye wastewaters prepared from commercial grade acid, basic and disperse dyes were used in this study and the results showed high removals of acid dyes by fly ash and slag while peat and bentonite exhibited high basic dye removals. For the acid and basic dyes, the removals were comparable with that of granular activated carbon, while for the disperse dyes, the performance was much better than that of granular activated carbon. The results obtained point towards viable adsorbents which are both effective as well as economically attractive for color removal from wastewaters.