bluuebunny/crossref_metadata_2025 huggingface dataset:
Combination of coagulation and catalytic wet oxidation for the treatment of pulp and paper mill effluents
Authors: Verenich S. , Laari A. , Nissen M. , Kallas J.
Published: May 2018

Wet oxidation (WO) is a well established process for purification of concentrated municipal and industrial wastewaters. Many attempts have been made to modify the WO process or to create a suitable combination of processes. This work was undertaken to investigate wet oxidation integrated with coagulation, i.e. to treat the sludge remaining after coagulation with a WO process. The possibility of regeneration of the used coagulant was also considered. Two waters from paper mills were used: TMP (thermomechanical pulp) circulation water and membrane concentrate. About 50% of the COD in the original water can be removed by coagulation using Fe2(SO4)3. The results from the wet oxidation experiments show the positive effect of iron in the chemical sludge as a catalyst. The efficiency of the WO process was enhanced almost by 100%. The remaining dissolved organic matter can be easily removed biologically.
Physico-chemical and biological characteristics of thermal springs in Köyceğiz and Dalaman basins in south-western Turkey and recommendations for their protection
Authors: Kazancí N. , Girgin S.
Published: May 2018

Many hydrogeological researches exist on the thermal springs of Turkey but limnological researches are very deficient. The results of the limnological research of the thermal springs in the basin of the meromictic lake Köyceğiz and Dalaman Basin are as follows; the thermal springs are of euthermal or chliarothermal types. In the thermal springs thermotolerant diatoms constituted the major plankton flora. Recommendations for the protection of thermal springs are given according to the results of this research.
Impact of atmospheric deposition on the headworks of a wastewater treatment plant - a case study
Authors: ZAtasi K. , Fujita G. , Le Platte G. , Hufnagel C. , Keeler G. , Graney J. , Chen T.
Published: May 2018

Specialized sampling equipment and ultra-clean analytical methodology were employed to quantify the concentrations or fluxes of mercury (Hg), cadmium (Cd) and polychlorinated biphenyl (PCBs) in ambient air, precipitation, runoff, sanitary sewer, and wastewater treatment plant (WWTP) influent. The relationship between the atmospheric deposition and runoff on controlled surfaces were explored for the three pollutants. The impact of the atmospheric deposition and runoff to the headwork loading of the WWTP were investigated. Atmospheric deposition was found to be the primary source of the mass of Cd, Hg, and PCBs in runoff from the controlled surfaces. Neither atmospheric deposition nor the runoff was the main sources of the three pollutants to the Detroit Wastewater Treatment Plant (WWTP). Wet weather flow contributes the main portion of the Cd, Hg, and PCBs loading to the WWTP.
A comparison of prototype compound parabolic collector-reactors (CPC) on the road to SOLARDETOX technology
Authors: Funken K.-H. , Sattler C. , Milow B. , de Oliveira L. , Blanco J. , Fernández P. , Malato S. , Brunotte M. , Dischinger N. , Tratzky S. , Musci M. , de Oliveira J.C.
Published: May 2018

Solar photocatalytic detoxification of non-biodegradable chlorinated hydrocarbon solvents (NBCS) is carried out in different concentrating and non concentrating devices using TiO2 as a photocatalyst fixed on the inner surface of the reaction tubes or as a slurry catalyst which has to be removed from the treated water. The reaction is most effective using 200 mg/l of TiO2 as a slurry in a non concentrating CPC reactor. The concentrating parabolic trough reactor has a poor activity because of its minor irradiated reactor surface. Catalyst coated glass tubes are less efficient then the used slurry catalyst. Their advantage is that no catalyst has not to be removed from the treated water and there is no loss of activity during treatment. Yet their physical stability is not sufficient to be competitive to the slurry catalyst. Nevertheless the degradation results are very promising and will possibly lead to commercial applications of this technology.
Normalising impacts in an environmental systems analysis of wastewater systems
Authors: Kärrman E. , Jönsson H.
Published: May 2018

In an environmental systems analysis of four wastewater systems, the environmental aspects were prioritised by normalisation of predicted impacts from the studied systems to the total impacts from society. Priority Group 1 (highest priority) consisted of discharges (flows) of nitrogen, cadmium, lead and mercury to water, recycling of nitrogen and phosphorus to arable land and flows of heavy metals to arable land. A conventional wastewater system (A) was compared to irrigation of energy forest with biologically treated wastewater (B), liquid composting of toilet wastewater (C) and a conventional system supplemented with urine separation (D). Analysing the aspects in priority group one, systems B–D improved the management of plant nutrients and decreased the flow of heavy metals to water, while the flow to arable land increased, especially for system B. The suggested method is useful in municipal environmental planning and when choosing a wastewater system.
Optimal experimental design and artificial neural networks applied to the photochemically enhanced Fenton reaction
Authors: Göb S. , Oliveros E. , Bossmann S.H. , Braun A.M. , Nascimento C.A.O. , Guardani R.
Published: May 2018

Among advanced oxidation processes (AOPs), the photochemically enhanced Fenton reaction may be considered as one of the most efficient for the degradation of contaminants in industrial wastewater. This process involves a series of complex reactions. Therefore, an empirical model based on artificial neural networks has been developed for fitting the experimental data obtained in a laboratory batch reactor for the degradation of 2,4-dimethyl aniline (2,4-xylidine), chosen as a model pollutant. The model describes the evolution of the pollutant concentration during irradiation time as a function of the process conditions. It has been used for simulating the behavior of the reaction system in sensitivity studies aimed at optimizing the amounts of reactants employed in the process, an iron(III) salt and hydrogen peroxide, as well as the temperature. The results show that the process is most sensitive to the concentration of iron(III) salt and temperature, whereas the concentration of hydrogen peroxide has a minor effect.
Oxidation of polycyclic aromatic hydrocarbons by ozone in the presence of sand
Authors: Choi H. , Kim Y.-Y. , Lim H. , Cho J. , Kang J.-W. , Kim K.-S.
Published: May 2018

A series of soil slurry experiments was performed to investigate the characteristics of PAHs removal by ozone in various conditions. Gaseous ozone was bottled into the aqueous phase in the presence of soil contaminated by PAHs. The effects of soil media, OH radical scavengers, ozone dosage, and humic acid were examined at the given experimental conditions. There exists a substantial difference in the removal of PAH according to the types of soil media tested. Baked sand showed the highest removal efficiency compared to the others. The descending order of removal rate was: BS>S>GB. This is considered to be due to the OH radical effect produced by catalytic reactions of ozone with the reactive site on the and. This is qualitatively proved by the experiment of scavenging OH radicals using tert-butanol. The comparison of half-lives of ozone in sand and glass bead columns further supports this hypothesis. It was found that about 22% of enhancement of phenanthrene destruction was accomplished by OH radicals produced by the catalytic ozone decomposition. The rate of ozone consumption for the phenanthrene oxidation was obtained as 1.88 mg/mgO3/min.
Relevance of microbial extracellular polymeric substances (EPSs) - Part II: Technical aspects
Authors: Flemming H.-C. , Wingender J.
Published: May 2018

Extracellular polymeric substances (EPSs) are involved in both detrimental and beneficial consequences of microbial aggregates such as biofilms, flocs and biological sludges. In biofouling, they are responsible for the increase of friction resistance, change of surface properties such as hydrophobicity, roughness, colour, etc. In biocorrosion of metals they are involved by their ability to bind metal ions. In bioweathering, they contribute by their complexing properties to the dissolution of minerals. The EPSs represent a sorption site for pollutants such as heavy metal ions and organic molecules. This can lead to a burden in wastewater sludge; on the other hand, the sorption properties can be used for water purification. Other biotechnological uses of EPS exploit their contribution to viscosity, e.g., in food, paints and oil-drilling ‘muds’; their hydrating properties are also used in cosmetics and pharmaceuticals. Furthermore, EPSs may have potential uses as biosurfactants, e.g., in tertiary oilproduction, and as biological glue. EPSs are an interesting component of all biofilm systems and still hold a large biotechnological potential.
Remember the water - a comment on EPS colligative properties
Authors: Keiding K. , Wybrandt L. , Nielsen P. H.
Published: May 2018

The relationship between water and activated sludge components was examined. Reevaluation of published data on freezing point depression, drying rates and dewatering has been performed. The basis of this has been the assumption that the water/sludge relationship is considered to be a colligative effect. Since the results indicate this to be the case, we suggest that the published concepts of “pools of water” are false. Data on swelling properties of EPS as a function of pH suggests that the colligative properties are largely determined by the counterions of charged polymers and surfaces.
Removing arsenic from groundwater for the developing world - a review
Authors: Jiang J.-Q.
Published: May 2018

This paper is principally concerned with summarising the experience to date of treating arsenic containing ground/surface water by oxidation, coagulation/precipitation and adsorption processes. Arsenic (As) has been verified through epidemiological evidence as one of the most carcinogenic and toxic substances in surface and ground water. Oxidation, coagulation/precipitation, and adsorption have been widely used in arsenic removal and the study results demonstrated that these technologies can remove arsenic from ground/surface water efficiently; the residual arsenic concentration in the effluent could be in the range of 5-10 μg/l, against the influent arsenic concentration in the range of 10-500 μg/l. However, these technologies need to be surveyed in order to validate the efficiency, cost and maintenance requirments by considering social and economic situations and the availability of the local resources in the developing world.
A study of the litter loadings in urban drainage systems - methodology and objectives
Authors: Marais M. , Armitage N. , Pithey S.
Published: May 2018

The recently completed report on “The removal of urban litter from stormwater conduits and streams” (by Armitage et al.) notes that little data is available on the nature and quantity of litter that finds its way into the stormwater drainage systems. The Council for Scientific and Industrial Research (CSIR) estimated in 1991 that 780 000 tonnes of waste a year was entering the drainage systems of South Africa, representing a potential removal cost in excess of two billion rand. There is thus a considerable need for finding ways to reduce litter loadings through better catchment management. Although suggestions have been made as to how this might be achieved, there is very little scientifically verified data from anywhere in the world to show that any of these proposed methods would be effective in South Africa. Only through an improved knowledge of the litter loadings in South African urban drainage systems can appropriate strategies to reduce litter loadings be arrived at. This improved knowledge is one of the twin objectives of the Water Research Commission Project No. K5/1051 entitled “The reduction of urban litter in drainage systems through integrated catchment management.” Under this project a three-year monitoring programme has been instituted in nine catchments covering a range of different land uses, socio-economic levels and densities in the Cape Metropolitan Area. This paper focuses on the methodology behind the monitoring programme and the objectives it is hoped to achieve.
Suitability of the H2S method for testing untreated and chlorinated water supplies
Authors: Nair J. , Gibbs R. , Mathew K. , Ho G. E.
Published: May 2018

Rainwater, borewater and catchment water are used for domestic water supply purposes with or without treatment in remote areas around the world. These places seldom have any facilities for routine testing of their drinking water. A simple on-site testing method is highly required in such areas. The H2S method has been tested for treated drinking water and was found to have a good correlation with the standard methods. The present study was aimed at assessing the suitability of the H2S method for testing different sources of drinking water. Since these types of water may contain H2S producing bacteria not of faecal origin the occurrence of false results in this method cannot be overruled. Therefore it was worthwhile to study whether the positive results are true positive results and what percentage of false positive and false negative results could be expected while using this test for routine analysis of water samples. Results were compared with the results using standard procedures for testing total coliforms, Escherichia coli and Salmonella spp. The present experiment analysed 121 rainwater samples, 17 borewater samples, 41 catchment water samples and 74 remote Aboriginal community water samples. Rainwater, borewater and catchment water samples gave true results of 78.5%, 82.3% and 80.5% respectively while the treated and untreated community samples gave true results of 93.7 and 84.6% respectively. It was concluded that in the developing countries where the acceptable level of total coliform is <10 MPN, the H2S method would be a good test to identify microbial contamination. In other regions, the H2S method could be used as a screening test for drinking water supplies.
Modelling production of extracellular polymeric substances in a pseudomonas aeruginosa chemostat culture
Authors: Kommedal R. , Bakke R. , Dockery J. , Stoodley P.
Published: May 2018

Formation of extracellular polymeric substances (EPSs) by mucoid pseudomonas aeruginosa was investigated using literature data from chemostat cultures. The data were used to calibrate a product formation regime allowing substrate sufficient and endogenous EPS formation. Yield coefficients for both formation conditions were elucidated based on metabolic pathway analysis. Growth and non-growth related specific formation rates of 0.18 g CEPS/g Ccell/h and 0.03 1/h were estimated, respectively. The exogenous and endogenous EPS yield was found to be 0.77 g CEPS/g Cglu and 0.79 g CEPS/g Ccell, respectively. Being structurally equivalent to comprehensive maintenance models, this model allows for non-growth related product formation, showing the same quality of fit as previous models restricted to exogenous EPS precursors.
Anaerobic treatment and biogas recovery for sago wastewater management using a fluidized bed reactor
Authors: Saravanane R. , Murthy D. V.S. , Krishnaiah K.
Published: May 2018

Starch manufacturing industrial units, such as sago mills, both at medium and large scale, suffer from inadequate treatment and disposal problems due to high concentration of suspended solid content present in the effluent. In order to investigate the viability of treatment of sago effluent, a laboratory scale study was conducted. The treatment of sago effluent was studied in a continuous flow anaerobic fluidized bed reactor. The start-up of the reactor was carried out using a mixture of digested supernatant sewage sludge and cow dung slurry in different proportions. The effect of operating variables such as COD of the effluent, bed expansion, minimum fluidization velocity on efficiency of treatment and recovery of biogas was investigated. The treated wastewater was analysed for recycling and reuse to ensure an alternative for sustainable water resourse management. The maximum efficiency of treatment was found to be 82% and the nitrogen enriched digested sludge was recommended for agricultural use.
Time-resolved study of biofilm architecture and transport processes using experimental and simulation techniques: the role of EPS
Authors: Kuehn M. , Mehl M. , Hausner M. , Bungartz H.-J. , Wuertz S.
Published: May 2018

Cellular material and extracellular polymeric substances are the basic structural elements in biofilm systems. The structure and role of EPS for biofilm development and metabolic processes have not been precisely determined and, therefore, have not yet been included as a necessary element in modelling and simulation studies. This is due to the difficulty of experimentally detecting the extracellular polymeric substances in situ and differentiating them from cellular material on the one hand, and to the subsequent uncertainty about appropriate models - e.g. rigid hindrances, porous microstructure or visco-elastic structure - on the other hand. In this work, we report on the use of confocal laser scanning microscopy to monitor the development of a monoculture biofilm of Sphingomonas sp. grown in a flow cell. The bacterial strain was genetically labelled resulting in strong constitutive expression of the green fluorescent protein. The development of extracellular polymeric substances was followed bybinding of the lectin concavalin A to cell exopolysaccharides. The growth of the resulting strain was digitally recorded by automated confocal laser scanning microscopy. In addition, local velocity profiles of fluorescent carboxylate-modified microspheres were observed on pathlines throughout the biofilm. The CLSM image stacks were used as direct input for the explicit modelling and three-dimensional numerical simulation of flow fields and solute transport processes based on the conservation laws of continuum mechanics. At present, a strongly simplifying EPS-model is applied for numerical simulations. The EPSs are preliminarily assumed to behave like a rigid and dense hindrance with diffusive-reactive solute transport.
Comparison of pollutant runoff in Lake Biwa tributaries, Japan and the brunette river watershed, Canada
Authors: Ichiki A. , Hall K. J. , Maruta Y. , Yamada K.
Published: May 2018

This study is aimed at verifying runoff pollutant loadings from urban areas. Urban runoff has been considered an important source of diffuse pollution especially during storm events. This paper describes the pollutant runoff during storm events, mainly in terms of effects of watershed characteristics. Data collected from Lake Biwa tributaries, Japan, have shown fundamental information to control pollutant runoff into receiving water. Also, data from the Brunette River watershed, Canada, which is a highly urbanized watershed in the Vancouver region, have been used for a comparative analysis. In the results, available information for the environmental management of urban storm water runoff was obtained by comparing the data on pollutant runoff in both watersheds.
Global predictive real-time control of Quebec Urban Community's westerly sewer network
Authors: Pleau M. , Pelletier G. , Colas H. , Lavallée P. , Bonin R.
Published: May 2018

Quebec Urban Community (QUC) has selected Global Predictive Real-Time Control (GP-RTC) as the most efficient approach to achieve environmental objectives defined by the Ministry of Environment. QUC wants to reduce combined sewer overflows (CSOs) frequency to the St Lawrence river to two events per summer period in order to reclaim the use of Jacques-Cartier Beach for recreational activities and sports of primary contact. QUC's control scheme is based on the Certainty Equivalent Control Open Loop Feedback (CEOLF) strategy which permits one to introduce, at each control period, updated measurements and meteorological predictions. A non-linear programming package is used to find the flow set points that minimise a multi-objective (cost) function, subjected to linear equality and inequality constraints representing the physical and operational constraints on the sewer network. Implementation of GP-RTC on QUC's westerly network was performed in the summer of 1999 and was operational by mid-August. Reductions in overflow volumes with GP-RTC compared to static control are attributed to the optimal use of two existing tunnels as retention facilities as well as the maximal use of the wastewater treatment plant (WWTP) capacity.
Application of mathematical tools to improve the design and operation of activated sludge plants. Case study: the new WWTP of Galindo-Bilbao Part II: Operational strategies and automatic controllers
Authors: Galarza A. , Ayesa E. , Linaza M. T. , Rivas A. , Salterain A.
Published: May 2018

This paper presents a new sensitivity analysis methodology for Activated Sludge WWTPs. It is based on both (a) the calculation of the range of “manipulated input variables” that satisfy the restrictions imposed on the “output variables” and (b) on the computation of isolines of the output variables inside the feasible operating space. This analysis allows a more precise description of the operating constraints, facilitates the understanding of the steady-state behaviour of the process and detects possible areas where the process is very sensitive to small disturbances. The feasible operating space for two Activated Sludge WWTP processes for CN removal (RDN, DRDN), using SRT and DO level as “input variables” as well as effluent quality and exploitation costs as the main “output variables” is studied. The proposed methodology facilitates the selection of the appropriate operational strategy and the design of automatic controllers. Some examples of the application of this methodology for the design of automatic controllers in a real WWTP are briefly presented.
Advanced monitoring and control of anaerobic wastewater treatment plants: diagnosis and supervision by a fuzzy-based expert system
Authors: Puñal A. , Rodríguez J. , Franco A. , Carrasco E. F. , Roca E. , Lema J. M.
Published: May 2018

A fuzzy-based expert system (ES) for the diagnosis and supervision for anaerobic digesters is presented. The system was developed in a Microsoft Windows support using fuzzy logic inference together with a rule base for the implementation of expert knowledge. The ES runs on-line through three main modules, which determine the state and trend of the process, and the best set points for the actuation on the final control elements of the plant. Two further modules run in parallel, when they are required by the operator, using off-line and on-line information for the detection of inhibition due to toxic compounds in the process and for the validation of the on-line diagnosis.

The diagnosis and supervision ES was tuned up in order to adjust the membership functions describing the process, and lately tested, running on-line, to study the response of the rule base.
Closed-loop identification and control application for dissolved oxygen concentration in a full-scale coke wastewater treatment plant
Authors: Yoo C. K. , Cho J. H. , Kwak H. J. , Choi S. K. , Chun H. D. , Lee I.
Published: May 2018

The objective of this paper is to apply a closed-loop identification to actual dissolved oxygen control system in the coke wastewater treatment plant. It approximates the dissolved oxygen dynamics to a high order model using the integral transform method and reduces it to the first-order plus time delay (FOPTD) or second-order plus time delay (SOPTD) for the PID controller tuning. To experiment the process identification on the real plant, a simple set-point change of the speed of surface aerator under the closed-loop control without any mode change was used as an activation signal of the identification. The full-scale experimental results show a good identification performance and a good tracking ability for set-point change. As a result of improved control performance, the fluctuation of dissolved oxygen concentration variation has been decreased and the electric power saving has been accomplished.
Developing a model based decision support tool for the identification of sustainable treatment options for domestic wastewater
Authors: Balkema A. J. , Preisig H. A. , Otterpohl R. , Lambert A. J. , Weijers S. R.
Published: May 2018

To enable decision makers to select sustainable wastewater treatment systems, insight into the sustainability of a wide variety of systems should be provided in a transparent way leaving room for adaptation and interpretation according to the local situation. To provide this insight a structured methodology comparing wastewater treatment systems with respect to sustainability is defined. Similar to life cycle assessment (LCA) three phases can be distinguished: (1) goal and scope definition, (2) inventory analysis, and (3) optimisation and results. In the goal and scope definition we set the system boundaries to include most of the water cycle and part of the food cycle. Furthermore, we defined a multi-disciplinary set of sustainability indicators including technical, economic, environmental, and socio-cultural aspects. In the inventory analysis these sustainability indicators are quantified using simple static models of wastewater unit operations. Selection of unit operations results in a model of a complete wastewater treatment system. In the optimisation phase the decision maker can weigh the different sustainability indicators and select sustainable options through integer programming.
Improving uncertain nutrient load estimates for Lake Balaton
Authors: Clement A.
Published: May 2018

Annual nutrient loads have been estimated for Lake Balaton over three decades. Tributaries may transport about half of the loads into the lake. The contribution of diffuse sources may reach two thirds of the total load. Biweekly/monthly water quality monitoring on small inflows (0.01 m3/s-0.3 m3/s range) results in a high uncertainty of load estimates. This paper evaluates the degree of uncertainties by using analytical expressions of sampling theory. Load-flow relationships were derived for five streams and annual total phosphorus load was predicted by four load estimation methods. A seasonal regression model, based upon the evaluation of historical set of observed phosphorus loads, appeared best to refine load estimates on small inflows. Correction frequently led to load estimates that exceeded uncorrected loads by a factor of two to three. Since the dynamics of the watercourses determined the errors of load estimates, stratified sampling is needed to decrease the uncertainties.
Development of a risk assessment based technique for design/retrofitting of WWTPs
Authors: Rousseau D. , Verdonck F. , Moerman O. , Carrette R. , Thoeye C. , Meirlaen J. , Vanrolleghem P. A.
Published: May 2018

Up to now, within the design/retrofit of wastewater treatment plants (WWTPs), deterministic models were used to evaluate different scenarios on their merits in terms of effluent compliance. This paper describes an approach in which a Monte Carlo engine is coupled to a deterministic treatment plant model, followed by risk interpretation in the form of concentration - duration - frequency (cdf) curves of norm exceedance. The combination of probabilistic modelling techniques with the currently available deterministic models allows to determine the probability of exceeding the effluent limits of a WWTP. This percentage of exceedance is accompanied by confidence intervals resulting from the inherent uncertainty of influent characteristics and model parameters. The approach is illustrated for a hypothetical case study, consisting of a denitrifying plant model inspired by the benchmark model described by Spanjers et al.
Identifiability and uncertainty analysis of the River Water Quality Model No. 1 (RWQM1)
Authors: Reichert P. , Vanrolleghem P.
Published: May 2018

State of the art models as used in activated sludge modelling and recently proposed for river water quality modelling integrate the knowledge in a certain field. If applied to data from a specific site, such models are nearly always overparameterised. This raises the question of how many parameters can be fitted in a given context and how to find identifiable parameter subsets given the experimental layout. This problem is addressed for the kinetic parameters of a simplified version of the recently published river water quality model no. 1 (RWQM1). The selection of practically identifiable parameter subsets is discussed for typical boundary conditions as a function of the measurement layout. Two methods for identifiable subset selection were applied and lead to nearly the same results. Assuming upstream and downstream measurements of dissolved substances to be available, only a few (5-8) model parameters appear to be identifiable. Extensive measurement campaigns with dedicated experiments seem to be required for successful calibration of RWQM1. The estimated prior uncertainties of the model parameters are used to estimate the uncertainty of model predictions. Finally an estimate is provided for the maximum possible decrease in prediction uncertainty achievable by a perfect determination of the values of the identifiable model parameters.
Full-scale experiences with anaerobic treatment of industrial wastewater
Authors: Frankin R.J.
Published: May 2018

High rate anaerobic treatment for industrial wastewater was first applied on a commercial scale in the sugar industry in the mid 70's. Since that time the technology has developed into a standard method of wastewater treatment for a wide variety of industries. The technology is now functional in over 65 countries and a total of approximately 1,400 plants were build by the 16 leading vendors of such systems. These plants account for approximately 65% of the total number of anaerobic treatment plants for industrial applications, which is estimated to be ca. 2,000. From the analysis from a database consisting of 1,215 plants it appears that the UASB technology as originally developed in the Netherlands is the most predominant process. It is also seen that the higher loaded EGSB type systems are gradually replacing at least some of the UASB applications.
Dissolved air flotation in drinking water production
Authors: Schofield T.
Published: May 2018

Dissolved Air Flotation (DAF) has become increasingly important in the field of potable water treatment, as a preferred option for treating upland and stored lowland waters. This paper outlines the development of dissolved air flotation (DAF) in potable water treatment, the benefits and disadvantages and the recent advances that has taken the process technology from an art to a science.
Treatment of spent filter backwash water using dissolved air flotation
Authors: Eades A. , Bates B. J. , MacPhee M. J.
Published: May 2018

There is increasing interest in treating recovered spent filter backwash water in the drinking water industry. In the USA the Filter Backwash Recycling Rule will come into effect in the near future. The purpose of the Rule is to prevent the concentrated pathogenic agents, potentially in the filter backwash water, from being returned to the head of the water treatment works without some form of treatment or dilution. By treating this flow both public health and financial liability can be better managed by the operating utility. Dissolved Air Flotation (DAF) was investigated as a possible technology alternative to simple or advanced sedimentation techniques. This application is not widespread but sits somewhere in between the two normal applications of DAF as a high solids sludge thickener and a low turbidity clarification system. Given this a pilot plant program, supported by jar testing, was undertaken to determine the process capability and the design parameters for this application.

DAF proved to be very suitable for backwash water recovery. DAF effluent turbidities of <1.0 NTU could be easily obtained, when raw water turbidities were in excess of 50 NTU. Chemical requirements were low with only a single low dose of polymer required to bind the floc particles to form a solids matrix suitable for flotation. Flocculation contact times ranged from 0–10 minutes depending on the nature of the raw water. Recycle rates as low as 5% performed satisfactorily with no significant improvement when increased to 20%. Sludge solids of 3.5–9.6% dry solids were found and very low volumes of sludge, <0.1% of the incoming flow make the DAF solids handling system very compact.
Combining the biological nitrogen and sulfur cycles in anaerobic conditions
Authors: Fdz-Polanco F. , Fdz-Polanco M. , Fernández N. , Urueña M.A. , García P.A. , Villaverde S.
Published: May 2018

The biochemical processes involved in the anaerobic degradation of carbon, nitrogen and sulfur compounds can be represented by an oxidation-reduction or electron donor-acceptor scheme. The theoretic values of Gibbs free energy (ΔG0) calculated from thermodynamic data indicate the feasibility of the reactions. The interactions C-S and C-N are well known but there is a lack of information about the interaction N-S. The anaerobic transformation of nitrates using reduced sulfur compounds can be explained considering that nitrate acts as electron acceptor while reduced sulfur compounds are the electron donors.

A new N-S interaction in anaerobic conditions (ORP = -425 mV) has been experimentally observed when treating industrial wastewater rich in organic nitrogen and sulfate. The mass balances of the different nitrogenous and sulfur compounds in the liquid and gas phases clearly indicated an uncommon evolution. An important percentage of the nitrogen entering the reactor as TKN was removed from the liquid phase appearing as N2 in the gas phase. Simultaneously, only part of the sulfate initially present in the influent appeared as sulfide in the effluent or as hydrogen sulfide in the gas. These experimental observations may suggest a new anaerobic N-S biological interaction involving simultaneous anaerobic ammonium oxidation and sulfate reduction, ammonium being the electron donor and sulfate the electron acceptor.
Evaluation of flocculation and dissolved air flotation as an advanced wastewater treatment
Authors: Pinto Filho A. C. , Brandão C. C.
Published: May 2018

A bench scale study was carried out in order to evaluate the applicability of dissolved air flotation (DAF) as an advanced treatment for effluents from three different domestic wastewater treatment processes, namely: (i) a tertiary activated sludge plant ; (ii) an upflow sludge blanket anaerobic reactor (UASB); and (iii) a high-rate stabilization pond.
Sewage treatment by anaerobic biological process associated with dissolved air flotation
Authors: Reali M. A. P. , Campos J. R. , Penetra R. G.
Published: May 2018

This paper presents the results of a study performed with a lab-scale batch DAF unit fed with previously coagulated (with FeCl3 or cationic polymer) effluent from a pilot scale up-flow anaerobic sludge blanket (UASB) reactor treating domestic sewage. The adequate coagulation/flocculation conditions – chemical dosage, time (Tf) and mean velocity gradient (Gf) in the flocculation step – and air requirements for flotation process were investigated. Best results were achieved for 65 mg.l−1 of FeCl3 at Tf around 15 min and Gf of 80 s−1. In the assays where only polymer was applied, 7 mg.l−1 of cationic polymer dosage gave optimum removals with Tf around 15 min and Gf of 30 s−1. Air requirements ranged from 9.5 to 19.0 g of air.m−1 wastewater. Best TSS (95% and residual of 2 mg.l−1), COD (85% and residual of 20 mg.l−1) and total phosphate (95% and residual of 0.6 mg.l−1) removals were obtained when applying FeCl3, although the use of cationic polymer also produced good level of TSS (74% and residual of14 mg.l−1) and COD (75% and residual of 45 mg.l−1) removals. For the UASB-DAF (batch) system and FeCl3, global efficiencies would be 97.2% for COD, 97.9% for phosphate and 98.9% for TSS.
Ozonation followed by coagulation/flocculation and flotation as post-treatment of the effluent from an anaerobic baffled reactor treating domestic sewage
Authors: Marchioretto M. M. , Reali M. A.
Published: May 2018

This paper reports on the use of ozonation and dissolved air flotation as a post-treatment of the effluent from an anaerobic baffled reactor treating domestic sewage. After preliminary essays, the present experiment was performed fixing coagulant doses and, to all of them, some ozone doses were investigated. Later, the pH value and the ozone dose which provided the best removal efficiencies of all the parameters involved were tested, changing the coagulant dose and varying, for each of them, two ozone doses: the zero one and the optimum. Considering the best conditions of coagulation/flotation (ferric chloride dose of 65 mg.L−1: and pH around 5.5), the ozone dose application of 6 mg.L−1 led to a significant level in the removal efficiency of COD (80.4%), BOD (79.0%), total phosphate (93.4%), apparent color (91.9%) and turbidity (97.0%), demonstrating that the system seems to be efficient and capable of promoting a high degree of sewage post-treatment, reducing the coagulant dose until 30%, with a consequent reduction in the sludge generation.
Removal of hydrocarbons from petrochemical wastewater by dissolved air flotation
Authors: Galil N. I. , Wolf D.
Published: May 2018

The dissolved air flotation (DAF) method has an important role in the removal of hydrocarbons, as well as in the protection of the biological treatment, which usually follows the DAF. The aims of this study were to evaluate the removal efficiencies of suspended solids, general organic matter, hydrocarbons and phenols by DAF, as influenced by the flocculant type, aluminum sulfate (alum) or a cationic polyelectrolyte. Laboratory batch experiments included chemical flocculation followed by DAF, controlling the flocculant dose and the air to solids ratio. The characterization of the influent and effluent was based on general analysis of organic matter (COD), suspended solids, hydrocarbons and phenols. The influent to all experiments was supplied daily from the outlet of a full scale oil-water gravitational separation unit at a petrochemical complex in Haifa, Israel. The influent contained hydrocarbons in the range of 20 to 77 mg/L. Usually less than 10% were found in “free” form, 70 to 80% were emulsified and 10 to 20% were dissolved. The DAF process enabled us to reduce the general hydrocarbon content by 50 to 90%. The effluent was characterized by stable and uniform levels of suspended solids, and oil, almost without depending on the influent concentrations. The results indicate that the chemical flocculation followed by DAF removed efficiently the emulsified phase, which could be aggregated and separated to the surface. However, it was found that the process could also remove substantial amounts of dissolved organic matter. This mechanism could be explained by the hydrophobic characteristics of some of the substances, which could bind to the solid surfaces. It was found that aggregates created by the flocculation with the cationic polyelectrolite (C-577) could remove up to 40% from the dissolved hydrocarbon. Alum flocs also indicated removal of soluble materials, mainly phenols. The results obtained in this study indicated the possibility to improve the protection of the biological treatment process by preliminary removal of hydrophobic compounds, usually considered as either inhibitory or toxic. This removal can be based on sorption onto aggregates created by chemical flocculation, which can be efficiently removed by dissolved air flotation.
Perspectives on anaerobic treatment in developing countries
Authors: Foresti E.
Published: May 2018

Developing countries occupy regions where the climate is warm most of the time. Even in sub-tropical areas, low temperatures do not persist for long periods. This is the main factor that makes the use of anaerobic technology applicable and less expensive, even for the treatment of low-strength industrial wastewaters and domestic sewage. Based mainly on papers presented at the ‘VI Latin-American Workshop and Seminar on Anaerobic Digestion’ held in Recife, Brazil, in November 2000, this text approaches the perspectives of anaerobic treatment of wastewaters in developing countries. Emphasis is given to domestic sewage treatment and to the use of compact systems in which sequential batch reactors (SBR) or dissolved-air flotation (DAF) systems are applied for the post-treatment of anaerobic reactor effluents. Experiments on bench- and pilot-plants have indicated that these systems can achieve high performance in removing organic matter and nutrients during the treatment of domestic sewage at ambient temperatures.
A multiphase CFD model of DAF process
Authors: Ta C. T. , Beckley J. , Eades A.
Published: May 2018

A Eulerian-Eulerian multiphase CFD model is employed for the air/water flow. A 3D structure grid is used to incorporate the air nozzle and tank geometry. The fixed frictionless wall boundary approximating the free surface acts as a sink to allow the air bubbles to escape. The air/water volume fraction in the flotation tank is evaluated to determine the effective air/water fluid density. The floc particle is then introduced and is tracked in the air/water fluid using a disperse Lagrangean model. Fate of these flocs depends on their sizes and density. Flocs therefore can either escape through the top water surface, settles in the main tank or breakthrough under the outlet weir. The CFD model is developed for a full scale DAF tank to predict the flow dynamic, particle removal and settled solid profile. The general flow pattern is compared with flow visualisation using the underwater camera. Comparison of average fluid velocities is carried out using acoustic Doppler velocimetry ADV measurement.
Characteristics of alumino-humic flocs in relation to DAF performance
Authors: Bache D. H. , Rasool E.
Published: May 2018

This paper examines the implications of pretreatment in the context of the likely behaviour of flocs in DAF units. Evidence indicates that the maximum floc size (dmax) of alumino-humic is scaled by the Kolmogorov length (η) with dmax/η ˜ 1. A larger ratio exists when polymer is present. Data from the literature suggests that velocity gradient in the inlet chamber may exceed 1000 s−1, suggesting η ˜ 40 μm. This view of the response of floc to shear is supported by shear tests carried out on samples of floc withdrawn from flocculators at full scale water treatment works. Using an underwater CCTV camera, coupled with image analysis, it is shown that floc sizes in conventionally designed flocculators are much bigger than the sizes which are likely to exist in DAF units. Circumstantial evidence gained from water treatment works suggests that DAF units perform satisfactorily whatever the size of the incoming floc. From such evidence, the authors question the conventional design of the flocculators in association with DAF units.
The performance of the human nose in odour measurement
Authors: Walker J.C.
Published: May 2018

Over the last 20 years or so, there has been steadily increasing activity in the area of applied human odour measurement. This has been especially true outside of the United States. Yet, for about 40 years, there has also been decreasing interest and activity, on the part of academic smell researchers, in rigorous quantitative measurement of the functional properties of the human olfactory system. There are some optimistic signs, however, that this situation may be improving. Applied meetings such as this one are reaching out to learn more about basic research in human olfaction and some research groups are venturing out to indoor air quality, environmental health, water quality and other applied areas. In this paper I hope to support and accelerate the increasingly fruitful interactions that are beginning. The paper aims to make four main points. First, some of the most important ways in which the laboratory differs from everyday life will be noted. Keeping these differences in mind lessens the risk that laboratory data will be used uncritically to make predictions of real-world responses to chemical stimuli. Next, the specific benefits that would accrue from more fruitful interactions between basic and applied researchers will be highlighted; this is perhaps best seen by noting problem areas resulting from too little cross-fertilisation. Third, the CEN standard for the measurement of odour thresholds will be discussed in light of what is known concerning both the functional aspects of the human olfactory system and the current state of knowledge concerning best methods for investigating this system. Finally, some recent work we have done that was designed to help characterise human odour responses and demonstrate improved methodology, will be briefly mentioned. The paper concludes with suggestions as to how the scientific basis of applied odour measurement may best be enhanced.
Use of electronic noses for detection of odour from animal production facilities: a review
Authors: Nimmermark S.
Published: May 2018

In the field of controlling livestock and poultry odours in the internal and external environment and in derived food products, one main obstacle is how to measure the odour in a suitable way. Olfactometry and a human panel have been used in most studies of farm odour until now. Alternatives like electronic noses are interesting considering disadvantages for olfactometry regarding cost and labour requirement. An electronic device can produce an almost instant response which is useful in many applications. Studies have shown detection of farm odour for some electronic noses and also response to odour concentrations. Other studies have shown very high odour threshold values compared to human noses. Electronic noses with a large number of sensors have been developed since a base was formed in the 1950s. The fast progress in data processing and sensor development in the latest years have made the electronic noses interesting for a large number of industrial applications in the food processing industry, as well as in other areas. Materials like manure produce a complex mixture of odorous compounds and the interaction between these creates a unique odour where no specific dominating and characterising compound seems to exist. Related to swine farms almost 200 different odorous compounds have been reported. The electronic noses can, depending on the sensitivity of its sensors, detect some compounds at lower levels than the human nose, while other compounds offensive to a human nose cannot be detected. Proper function of the electronic noses with sensitivity for the odorous gases in the application must be followed by satisfying properties regarding ageing, temperature stability, humidity and other environmental factors.