bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarographic and Voltammetric Determination of Some Toxic Heavy Metal Ions in the Treated Wastewater at Abu-Dhabi, U.A.E.
Authors: El-Hasani S. R. , Al-Dhaheri S. M. , El-Maazawi M. S. , Kamal M. M.
Published: May 2018

Differential pulse polarographic (DPP) and anodic stripping voltammetric (DP-ASV) techniques were employed for determination of Zn, Cu, Pb and Cd in the treated wastewater at Abu-Dhabi, U.A.E. Four samples were collected from two different treated wastewater plants at Al-Ain and Abu-Dhabi cities during the period of May-Nov, 1996. The collected samples were subjected to UV-irradiation, before the direct analysis, to eliminate the interference effect of the organic compounds on the determination of the metal ions. Double step solvent extraction was used to minimize the effect of interference of the organic compounds on the methods of analysis. Also, the solvent extraction techniques was used for preconcentration of the four metal ions from the collected samples. The pre-treated samples with UV-irradiation and/or solvent extraction techniques were subjected to full analysis using DPP and DP-ASV methods in order to determine the operational and solution parameters for trace determination of the metal ions. A multi-step standard addition method was applied on the polarographic and voltammetric peaks of the four metal ions for calculation of the concentration level of each metal ion in the collected samples. the results indicated that the concentration range of the four metal ions in the investigated samples were 0.11-0.16, 0.020-0.025, 0.01-0.02 and 0.008-0.012 ppm for Zn(II), Cu(II), Pb(II) and Cd(II), respectively. It should be mentioned that the treated wastewater in Abu-Dhabi was used for irrigation of ornamental plants.
Water binding in biofilms
Authors: Schmitt J. , Flemming H.-C.
Published: May 2018

The main component of biofilms is water, which can make up to over 90% of the wet weight. Biofilms are therefore considered as hydrogels. Water binding and mobility are crucial for diffusion processes in biofilms as well as for dewatering of sludges. In a FTIR-ATR study, the hydrogen-deuterium exchange in native drinking water mixed population biofilms was investigated non-destructively in a flow-through cell. The exchange process of water is characterized by two steps, the first completed after 49 seconds and the second after 21 minutes, indicating different water retention mechanisms. The process is fully completed after about 2 hours. If the biofilm is treated with chlorine (6 mg L−1 for 12h), exchange happens faster and no steps can be observed, indicating a change in the matrix with respect to water binding properties. It is concluded that the water in the EPS matrix is organized in a fine structure which influences the properties of the biofilm.
Assessment of drinking water filter microbial communities using taxonomic and metabolic profiles
Authors: Moll Deborah M. , Summers R. Scott
Published: May 2018

Biofiltration is used in drinking water treatment to oxidize the biodegradable fraction of natural organic matter (NOM), thus controlling disinfection byproducts (DBP), DBP formation and microbial regrowth. Most work to date has focused on assessing drinking water biofilter performance; the microbial dynamics of biofilters have not been examined and are poorly understood. The objective of this research was to provide baseline information about the impact of design, operational and water quality parameters on NOM and DBP precursor removal, and microbial biomass and community structure profiles of biologically active drinking water rapid media filters. Phospholipid fatty acid (PLFA) profiles and the BIOLOG system for detecting the metabolism of sole carbon sources were found to be useful for characterizing the microbial communities in drinking water biofilters. Substrate removal was impacted most by ozonation, contact time, backwashing with water containing disinfectants, and low temperature. Using the PLFA technique, it was found that ozonation, contact time, and backwashing with water containing disinfectants had the greatest impact on microbial community structure. The BIOLOG system differentiated communities based on ozonation, contact time, pH, and temperature.
How biofilm clusters affect substrate flux and ecological selection
Authors: Rittmann Bruce E. , Pettis Matthew , Reeves Howard W. , Stahl David A.
Published: May 2018

We use three-dimensional mathematical modeling to represent key substrate phenomena in a prototypical cluster-and-channel biofilm. Clusters are represented as cylinders in which diffusion and reaction occur simultaneously. The geometry of the effective diffusion layer surrounding the cluster is manipulated to simulate different degrees of advection within the channels. The cluster-and-channel configuration can increase the average substrate flux per substratum area only if the channels have advection and the surface coverage is high enough. The modeling also suggests that sub-cluster niches for slower growing species, such as nutrifiers, are reduced in size when substrate penetrates the cluster from all sides. Thus, the cluster-and-channel configuration might create a competitive disadvantage for slow-growing species.
Two-dimensional simulations of biofilm development: effects of external environmental conditions
Authors: Hermanowicz Slawomir W.
Published: May 2018

A new approach to biofilm modeling based on cellular automata was described. Simple, local rules governing cell growth and erosion generated self-organized biofilm structures. In numerical experiments, the morphologies of simulated biofilms depended primarily on the thickness of the concentration boundary layer that controlled the external mass transfer. The bulk nutrient concentration had a weaker influence. For thin boundary layers, compact, dense base biofilms were generated. Thick boundary layers produced ramified, dendritic structures with higher porosities. For the same value of a critical bulk nutrient concentration, biofilm structures, generated in individual simulations, varied randomly between two very different outcomes: a dense, thick layer or almost complete erosion.
Discrete-differential modelling of biofilm structure
Authors: Picioreanu C. , van Loosdrecht M. C. M. , Heijnen J. J.
Published: May 2018

A fully quantitative two- and three-dimensional approach for biofilm growth and structure formation has been developed. The present model incorporates the flow over the irregular biofilm surface, convective and diffusive mass transfer of substrate, bacterial growth and biomass spreading. A future model will also include a mechanism for biofilm detachment due to biofilm deformation stress. Any arbitrary shape of the carrier surface can be accommodated in the model, as well as multispecies and multisubstrate biofilms. Results of model simulations show that the ratio between nutrient transfer rate to the biofilm and the bacterial growth rate influences to a great extent the biofilm roughness and porosity. A low mass transfer rate, i.e., low Reynolds numbers or high values of Thiele modulus, results in the development of a rough and open biofilm. When the biofilm growth is not limited by the substrate availability but by the rate of bacterial metabolism, the biofilm forms as a compact and homogeneous structure. The multidimensional biofilm modelling approach we used is very suitable for theoretical investigation of factors that affect biofilm structure and ecology.
Bacteriological Evaluation of Composting Systems in Sludge Treatment
Authors: Shaban Ahmad M.
Published: May 2018

Sludge disposal was considered as a serious problem to the authorities. Thus, the treatment of sludge resulting from sewage treatment plants to remove pathogenic microorganisms and to improve its impact on the environment was considered as the main objective of several investigators. Composting is one of the methods of sludge treatment. Different systems of composting (static pile, windrow and natural draft) were applied and evaluated bacteriologically. Faecal coliform and salmonellae were removed completely during the first two weeks in case of forced aeration, but the former are still present till near the end of experiment with natural aeration. For the natural draft system with sawdust base, faecal coliform reduction increased up to 100% after 7 weeks, while faecal streptococci and coliphage decreased gradually and were removed completely at the end of treatment. Salmonellae disappeared after a few days from starting treatment. In case of alkaloids addition (cement and lime), the tested organisms reached acceptable levels with any concentration of alkaloids. Coliphage and faecal streptococci survived till the end of treatment. So, from the previous results it is clear to say, coliphage and faecal streptococci were more resistant to the composting processes than other organisms.
Development of a simple in vitro test system for the disinfection of bacterial biofilms
Authors: Härkönen P. , Salo S. , Mattila-Sandholm T. , Wirtanen G. , Allison D. G. , Gilbert P.
Published: May 2018

This paper evaluates the use of poloxamer-hydrogel biofilm-constructs for the routine evaluation of biocide formulations at use strength. Aqueous solutions of Poloxamer F127 show thermo-reversible gelation, being liquid at temperatures <15°C yet robust gels at temperatures >15°C. Chilled poloxamer solutions (30%w/v) were made up in tryptone soya broth and inoculated with c104-5 cfu/ml of stationary phase cultures of eleven foodborne spoilage and pathogen test-strains, including Listeria and Salmonella spp. Drops (200μl) were placed, in triplicate, onto pre-warmed, sterile stainless steel discs (8mm diam.) held in sealed-Petri dishes. These were incubated for 5h at 30°C during which time all strains grew well giving between 106-7 cfu/ml. Previous work had demonstrated that cells grown within poloxamer hydrogels in this manner adopted biofilm-phenotypes which were distinct from those of planktonically grown cells and which were characteristically resistant to a range of biocides. Incubated poloxamer gels, together with their supports were transferred to solutions (10ml) of four commercial biocide formulations: (i) a buffered (pH 10) tertiary alkyl amine formulation in an amphoteric surfactant (TAAS), (ii) a hydrogen peroxide, peracetic acid, acetic acid (pH 1) formulation (HPPA), (iii) sodium hypochlorite and sodium hydroxide formulation (pH 13) (HYPO), and (iv) isopropyl alcohol in lactic acid (pH 2.3) (IPA). After 5min the test pieces were removed and transferred to neutralizer at 15°C. The gels dispersed rapidly releasing the cells and enabling viable counts to be made. All formulations effected a >5-log kill of planktonic challenges within 5min whilst the levels of killing effected within the biofilm-constructs varied between 0.5 and 3-log reductions. The results were highly reproducible with patterns of susceptibility varying both as a function of organism, biocide-type and concentration. The experiments strongly support the view that poloxamer constructs might find application in trials and testing of new disinfectant formulations.
Influence of organic and ammonia loading on nitrifier activity and nitrification performance for a two-stage biological aerated filter system
Authors: Gilmore K. R. , Husovitz K. J. , Holst T. , Love N. G.
Published: May 2018

A pilot-scale, two-stage (carbon oxidation stage one, ammonia oxidation stage two) fixed film biological aerated filter (BAF) process was operated during the wintertime on-site at a domestic wastewater treatment plant. Over the study period, hydraulic loadings to the system were varied and generated a range of organic and ammonia loading conditions. Nitrification performance was monitored based on water quality along the length of the filters, effluent water quality, and activity levels of ammonia-oxidizing bacteria within the biofilm using an oligonucleotide probe. Overall nitrification efficiency for wintertime conditions (average temperature 12.4 ± 0.1°C) was greater than 90 percent when ammonia-N loadings to the second stage were 0.6 kg/m3-day or less. Nitrification efficiency started to deteriorate at loadings beyond this point. Biofilm and liquid samples were collected along the distance of the two columns at high and low ammonia loadings. The degree of activity observed by ammonia oxidizing bacteria in the biofilm corresponded with the disappearance of ammonia and the generation of nitrate as water passed through the columns. The zones of ammonia oxidizing activity progressed along the length of the columns as organic and ammonia loadings to the system increased. The oligonucleotide probe data suggest that this shift in the location of the nitrifier population is due to higher BOD loads to the second stage, which supported higher levels of heterotrophic growth in the column.
Methods to extract the exopolymeric matrix from biofilms: a comparative study
Authors: Azeredo Joana , Lazarova Valentina , Oliveira Rosário
Published: May 2018

To study the composition of a biofilm a previous extraction method is required to separate cells from the matrix. There are several methods reported in the literature; however they are not efficient or promote leakage of intracellular material. In this work several extraction methods were assayed in mixed culture and pure culture biofilms and their efficiency was evaluated by the amount of organic carbon, proteins and intracellular material extracted. The results showed that the extraction with glutaraldehyde 3% (w/v) was the most suitable method, extracting great amounts of organic carbon without promoting cell lysis or permeabilization. Glutaraldehyde is a bifunctional reagent that binds to cell walls avoiding their permeabilization and the biofilm matrix is solubilized in the solution.
Long-term eutrophication development in five coastal lakes of the Bulgarian black sea region
Authors: Kalchev R. K. , Botev I. S.
Published: May 2018

Referring to data for orthophosphate phosphorus and soluble inorganic nitrogen consisting of NO31− and NH41+ ions, an attempt was made to estimate the trophic status and to follow up trophic changes over 15 to 30 year periods. The PO43−-P concentrations alone put most lakes permanently in the highest trophic state (hypereutrophic level) according to the Likens (1975) scale, set for total phosphorus and nitrogen concentrations. Only the Ezerets and Shabla lakes presented an exception in the 1963-1967 period. The nitrogen concentration covered the range from higher than oligomesotrophic to hypereutrophic levels. The average values of the N/P ratio of Dourankoulak and Bourgas lakes (the more shallow lakes) varied around the optimum, and the lakes have been tending to become slightly nitrogen limited, while Ezerets, Shabla and Mandra lakes (the deeper lakes) turned from phosphorus into clearly nitrogen limited lakes. The dominance changes in phytoplankton composition of Shabla lake corresponded to the variations in the N/P ratio. The NH41+ -nitrogen/ NO31− -nitrogen ratio shows higher values and a greater increase in the more shallow lakes than in the deeper lakes, which reveals the differences of eutrophication development in lakes of different depths.
Treatment of Thermomechanical Pulping (TMP) Whitewater in Thermophilic (55°C) Anaerobic-Aerobic Moving Bed Biofilm Reactors
Authors: Jahren Sigrun J. , Ødegaard Hallvard
Published: May 2018

Thermomechanical pulping whitewater was treated in an anaerobic followed by an aerobic Kaldnes moving bed biofilm reactor at 55°C. The anaerobic reactor was mixed by gas circulation and the aerobic reactor was mixed by aeration. The anaerobic reactor was started with mesophilic inoculum, while the aerobic reactor was started without inoculation. The reactors were operated on molasses water for one and a half years before the experiment was started. Total biomass concentrations (suspended and attached) were 3.3 g VSS/L in the anaerobic reactor and 1.6 g VSS/L in the aerobic reactor when starting feeding the reactors with TMP whitewater. After 7 months of operation the biomass concentrations had reached 5.5 and 6.5 g VSS/L in the anaerobic and aerobic reactors, respectively. The CODsol removals in the anaerobic reactor were around 30 % at loading rates up to 7 kg CODsol/m3d, and over-all CODsol removals of about 60 % were achieved. The results show that the anaerobic-aerobic moving bed biofilm process could be feasible for the thermophilic treatment of thermomechanical pulping whitewater.
Performance evaluation of on-site treatment facilities for wastewater from Households, Hotels and Restaurants
Authors: Nakajima Jun , Fujimura Yoko , Inamori Yuhei
Published: May 2018

In order to evaluate performance of on-site treatment facilities which can be provided for environment protection in coastal areas, effluent qualities and removal efficiencies were surveyed in actual treatment facilities for wastewater from households, hotels and restaurants. On-site treatment facilities in Japan are fundamentally built according to the structural standards. They have a pretreatment process (sedimentation separation tank, anaerobic filter or equalization tank with screens) followed by an aerobic process (contact aeration, activated sludge, etc.). Small-scale facilities for individual household wastewater showed good performance of BOD removal with their effluent BOD below 20mg 1−1. They also exhibited nitrogen removal efficiency when they were operated in mixed liquor recycle mode. The facilities applied to wastewater from hotels, restaurants and stores showed good performance when the influent oil (hexane extracts) concentration had been decreased below 30mg 1−1 by using pretreatment. Nitrogen removal performance was high in the facilities which treated wastewater from a residential area or a condominium when they were operated in intermittent aeration mode. But resort condominiums of which influent BOD load was extremely low showed low performance of nitrogen removal even though they were operated in intermittent aeration mode because of the low BOD/N ratio in the influent. An equation was proposed to estimate the amount of methanol to be added in facilities in which the influent BOD/N ratio is low.
Nitrogen removal by submerged membrane separation activated sludge process
Authors: Nagaoka H.
Published: May 2018

The performance of the submerged membrane separation activated sludge (SMAS) process with intermittent aeration was investigated in a laboratory scale experiment. By intermittent aeration (30 minutes cycle), nitrogen was removed successfully (95% removal rate) from influent containing NH4-N and acetic acid. A mathematical model was developed to simulate the performance of the SMAS considering the behavior of extracellular polymers (production, degradation, accumulation on the membrane and consolidation) and the experimental result was successfully simulated by the model. Degradation of EPS was accelerated by intermittent operation, which suggests that the combination of biological denitrification with the membrane separation process is advantageous in the prevention of membrane fouling in the BOD-removal-type membrane process.
Development and Evaluation of a Partitioned Upflow Anaerobic Sludge Blanket (UASB) Reactor for the Treatment of Domestic Sewage from Small Villages
Authors: Chernicharo Carlos Augusto L. , dos Reis Cardoso Marcílio
Published: May 2018

This paper presents the development and field evaluation of a partitioned UASB reactor, conceived for the treatment of domestic sewage from small villages and areas with large variation of the daily flowrate. In such situations, conventional single compartment UASB reactors are submitted to very extreme hydraulic conditions, that can disturb the behaviour of the treatment system. In the partitioned reactor, which is constituted of three digestion compartments, three gas separation devices and a single settler compartment, an adequate distribution of the variable incoming wastewater into one, two or three digestion chambers, allows the establishment of more stable up flow velocities and less occurrence of dead zones. As a result, a better contact between substrate and biomass can be achieved and an improved performance of the system can be expected.

The partitioned UASB reactor was evaluated during a period of 16 months of continuous operation. The system presented a vary good performance during most of the operational period, showing very high efficiencies when the reactor was operated at a HRT of 7.5 hours. In this phase, the unit presented COD removal efficiencies around 80% and an average SS concentration in the final effluent of 32 mgSS/L. The research is still going on, focussing on the evaluation of the system under higher hydraulic loads and on the assessment of sludge activity and dehydration potential.

Due to the operational simplicity and low cost of the system, it is believed that this type of reactor can become a very attractive alternative for domestic sewage treatment in small villages, particularly in Brazil where the number of rural areas with wastewater treatment is negligible.
Effect of Nitrogen Loading Rate and Carbon Source on Denitrification and Sludge Settleability in Upflow Anaerobic Sludge Blanket (UASB) Reactors
Authors: Cuervo-López F. M. , Martinez F. , Gutiérrez-Rojas M. , Noyola R. A. , Gómez J.
Published: May 2018

The combined effect of carbon source and nitrogen loading rate (NLR) on denitrification and sludge granular settleability in upflow anaerobic sludge blanket (UASB) bench-scale reactors was studied. Acetate, lactate and glucose were used as carbon sources for denitrification. Three NLR were evaluated: 500, 1000 and 2000 mg NO3−-N/ld. It was found that NO3−-N consumption efficiency was 99% for all the cases. Denitrification efficiencies were high (85-96%) for all substrates and NLR tested, but specific denitrifying rates were a better representation of the denitrifying process. The results showed that specific denitrifying rate was dependent on type of carbon source and NLR. It was also found that sludge settleability and reactor stability was influenced by the carbon source. The use of acetate did not influence the sludge settleability while, sludge flotation was always observed when lactate was used as carbon source. Foaming was present when glucose was used, causing reactor unstability. An increase in the exopolymeric protein and carbohydrate content was observed when lactate and glucose were fed, in comparison with acetate as carbon source. Results obtained in this work suggest that the exopolymeric composition here referred to as protein/carbohydrate ratio (P/C) could be a better stability indicator than the sludge volumetric index (SVI).
Processes for the Removal of Humic Substances from Water - an Overview Based on Norwegian Experiences
Authors: Ødegaard Hallvard , Eikebrokk Bjørnar , Storhaug Ragnar
Published: May 2018

Humic substances can be removed from water by a number of different treatment processes because the humic substances are high molecular weight organic molecules carrying a negative charge, like colloids. The conventional treatment method is by coagulation/floc separation, but also sorption processes like ion exchange and adsorption on activated carbon as well as membrane filtration processes and oxidation/biofiltration processes can be used. In this paper an overview of design and operational experiences with all these treatment processes is given based on the experiences that have been gathered in Norway during the last 25 years.
Probabilistic modelling of sewer system overflow emissions
Authors: Willems P. , Berlamont J.
Published: May 2018

The main advantages of the probabilistic modelling of urban drainage systems are the possibility of quantification and efficient reduction of the risk of ‘wrong’ management decisions or engineering designs, as well as the less biased mathematical modelling. Such probabilistic modelling achieves quantification of the uncertainty in the field of model-output. In the modelling of sewer system overflow emissions, a lot of uncertainties are involved: uncertainties about the spatial rainfall-input, model simplifications of the sewer system and runoff catchment, and biases and uncertainties about the model parameters.

A methodology has been presented to quantify the different uncertainty-sources in a decomposed way by separating uncertainties about the model structure, the model input and the model parameters. It has been applied to an existing sewer system and WWTP, for which the emission modelling has been performed both by a full hydrodynamic and a simplified conceptual model. In this application, the importance of having accurate (spatial) rainfall data and a thoroughly calibrated runoff model has been noticed. A well-considered simplification of a full hydrodynamic model, for instance by a conceptual reservoir model, has a negligible influence on modelled values of sewer system emissions. Such simplification achieves a reduction of calculation times, which is a necessity in probabilistic modelling.
Enhanced Coagulation: US Requirements and a Broader View
Authors: Edzwald James K. , Tobiason John E.
Published: May 2018

Enhanced Coagulation is a new regulatory requirement in the United States aimed at removing TOC by coagulation thereby controlling formation of disinfection byproducts. Coagulation principles are summarized for alum coagulation of natural organic matter (NOM). Negatively charged NOM creates a coagulant demand for positively charged Al species resulting in a stoichiometric relationship between the alum dosage and the raw water DOC that is pH dependent. The paper addresses coagulation with a broader view than Enhanced Coagulation, termed multiple objective coagulation. In general the objectives include: 1) to maximize particle and turbidity removals by downstream solid-liquid separation, 2) to maximize TOC and DBP precursor removals, 3) to minimize residual coagulant, 4) to minimize sludge production, and 5) to minimize operating costs. Optimum coagulation conditions are those that maximize pathogen removals, produce low turbidities and particle counts, and minimize residual Al. It is shown, for treatment of waters of low alkalinity, that the optimum alum dosage selected to minimize UV absorbance with strict pH control produced excellent treatment for turbidity, pathogens, and NOM. Full scale plant data are used to demonstrate a dual coagulation strategy of alum and cationic polymer that reduces sludge production and overall operating costs compared to alum alone.
Experimental Evaluation of Cationic Polyelectrolytes for Removing Natural Organic Matter from Water
Authors: Bolto Brian , Abbt-Braun Gudrun , Dixon David , Eldridge Rob , Frimmel Fritz , Hesse Sebastian , King Simon , Toifl Melissa
Published: May 2018

The effectiveness of water treatment processes in removing natural organic matter varies with the nature of the natural organic matter (NOM), its molecular size, polarity and charge density, and with properties of the raw water such as turbidity and hardness. In some cases conventional alum treatment is inefficient. We have compared NOM removals achieved by conventional and polymer-based processes in bench-scale treatment of reconstituted ground and surface waters of varying colour, made from NOM isolated from the same waters. NOM isolates were fractionated by adsorption on non-functionalised resins and an anion exchanger, and characterised by size exclusion chromatography. Jar tests with the isolated NOM compared coagulation with polyelectrolytes, alum, clays and metal oxides, with each of the inorganics being in conjunction with a polyelectrolyte.

Jar tests on reconstituted waters with alum and/or cationic polyelectrolyte show synergistic benefits from combinations of the two. The more hydrophobic NOM fractions were the most easily removed by polymer. The performance of cationic polymers improved significantly with increasing charge density and molecular weight. An alum/polymer combination is the most attractive treatment option.
Removal of Humic Substances by Oxidation/Biofiltration Processes - a Review
Authors: Graham Nigel J. D.
Published: May 2018

The paper is concerned principally with summarising the experience to-date of treating low alkalinity, low turbidity, humic-rich surface waters by the combination of ozone oxidation and biological filtration processes. In the UK, USA and other countries, upland coloured waters have often been treated by slow sand filtration in which only moderate removals of DOC have been achieved (< 20%). The presence of significant levels of humic matter in filtrate waters has led to difficulties in achieving compliance with the standards for colour and THMs, and concern about the stability of residual chlorine and potential biogrowth in water supply pipework. This has led to several investigations (eg. in the UK, Sweden and the USA) of the benefits of applying ozonation prior to slow sand filtration in view of its known capability to decolorise humic substances and enhance biodegradability of the organic fractions. This paper summarises the experience to-date and highlights the benefits and problems that have been identified. Some studies have attempted to compare the relative performances of slow sand filters and granular activated carbon (GAC) filters for the removal of BDOC and the paper reviews the principal findings of these studies in view of the growing worldwide interest in the application of ozone-GAC. One major limitation with the use of ozone-GAC is the need periodically to remove and regenerate the carbon, since bed lives for the removal of humic substances are typically short. An alternative approach is to use inorganic adsorbents instead of carbon which have the potential to be chemically regenerated in-situ. The paper refers to the results of laboratory tests that have been carried out on the potential use of pre-ozonation followed by inorganic adsorbents (eg. Activated alumina, bauxite) for the removal of humic substances.
Removal of Humic Substances by Adsorption/Ion Exchange
Authors: Fettig Joachim
Published: May 2018

This paper gives an overview over the ability of four different sorbent media, activated carbon, anion exchange resins, carbonaceous resins and metal oxides, for the removal of humic sustances. Both sorbent characteristics and solution parameters that affect the ultimate capacities are discussed, and approaches developed in order to describe sorption equilibria and rate of uptake are reported. In addition, successes and failures of predictive models are described. Some general conclusions about favorable conditions for the removal of humic substances by sorption processes are given.
Charge vs. Porosity - Some Influences on the Adsorption of Natural Organic Matter (NOM) by Activated Carbon
Authors: Newcombe G.
Published: May 2018

The adsorption of NOM ultrafiltration fractions onto ten activated carbons was studied. The aim of the research was the clarification of the effects of carbon charge and pore volume distribution and NOM charge and molecular weight on adsorption. The effect of pH and ionic strength on adsorption mechanisms was determined, and it was found that, in the absence of strong electrostatic effects, adsorption occurred by a pore filling mechanism in which the available pore volume was filled. At neutral pH the NOM has a significant negative charge which can affect the adsorption in several ways. At low surface concentrations on activated carbon with positive surface groups there is direct surface-NOM electrostatic attraction (screening reduced adsorption). At higher surface concentrations the adsorption becomes predominantly a physical surface-NOM attraction, possibly due to hydrophobic or aromatic ring interactions. The electrostatic effects are mainly caused by the lateral repulsion of the NOM that prevents the close-packed arrangement apparent at pH 3 (screening enhanced adsorption). For one activated carbon it was shown that the degree of ionisation of the adsorbed NOM is strongly dependent on the surface concentration.
A decision support model for the rehabilitation of “non-critical” sewers
Authors: Fenner R. A. , Sweeting L.
Published: May 2018

20% of the UK drainage network is made up of “critical sewers” (those with the highest economic consequences of failure) and in the last 15 years these have been systematically rehabilitated. The remaining 80% of non-critical sewers are dealt with by reactive maintenance only. The paper describes how a flexible and rational decision support model for rehabilitating non-critical sewers has been developed by analysing existing sewer performance data and asset information. The method represents information contained in asset and event databases in a GIS to rank variable sized grid squares into priority zones for action. A second stage uses a Bayesian statistical analysis of each pipe length within those grid squares most at risk from sewer failure. The model has been validated on data from several water company regions and whilst it does not enable an absolute prediction of sewer condition, the procedures help to distinguish those parts of the system in greatest need of attention.
Optimisation of control strategies for the urban wastewater system - an integrated approach
Authors: Schütze Manfred , Butler David , Beck M. Bruce
Published: May 2018

Currently, the sewer system, treatment plant and receiving water body are normally considered as separate units in water quality management. The study reported in this paper analyses the potential of integrated control of the urban wastewater system in its entirety. Assembly and implementation of an integrated simulation and optimisation tool, named SYNOPSIS, are presented. This software package allows water quantity and quality processes in the urban wastewater system to be simulated. Furthermore, optimisation modules included in this tool can be applied for off-line optimisation of control strategies. This procedure is exemplified for a semi-hypothetical case study site. Results obtained for this case study suggest that integrated control of the urban wastewater system can indeed lead to some improvement of its performance. This study demonstrates that a tool is now available for assessment of the potential of integrated control.
Controlling Adsorbable Organic Halogens (AOX) and Trihalomethanes (THM) Formation by Ozonation and Two-Step Granule Activated Carbon (GAC) Filtration
Authors: Vahala R. , Långvik V.-A. , Laukkanen R.
Published: May 2018

A pilot plant study in four parallel filter runs was performed in order to determine the effect of ozonation and two-step granular activated carbon (GAC) filtration on the removal of disinfection by-product (DBP) precursors. The results showed that ozonation significantly decreased the adsorbable organic halogens (AOX) (35%), simulated distribution system (SDS) AOX (37%) and SDS trihalomethanes (THM) (76%) from chemically treated and sand-filtered lake water, but did not decrease either short-term or the long-term chlorine demand. Biofiltration with exhausted GAC had a minor importance in the precursor removal (0-20%). The performance of adsorptive GAC filtration was strongly dependent on the age of the GAC filter bed, which was also seen as a strong correlation between the natural organic matter (NOM) measurements and DBP formation potential. Disinfection with chloramine produced lower THM, AOX, mutagenicity and MX (Z-3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone) levels compared to chlorine disinfection.
Comparison of the efficiency of best stormwater management practices in urban drainage systems
Authors: Mehler R. , Ostrowski M. W.
Published: May 2018

Increasingly extended and alternative methods for urban stormwater management have been discussed in Germany and elsewhere. Without question an economically and ecologically sound combination of central and decentral measures will be a concept of the future. Yet, at present the introduction of approaches other than traditional combined sewer systems is restricted due to missing planning tools and technologies. Adding a number of frequently used Best Stormwater Management Practices (BSMP's) has widely extended the applicability of an existing stormwater water balance and pollution load model.
The European Union Water Framework Directive: Taking European Water Policy into the Next Millennium†
Authors: Blöch H.
Published: May 2018

The European Union is currently thoroughly restructuring its water policy. A proposal by the European Commission for a Water Framework Directive is currently being negotiated at the European Parliament and the Council of Ministers. This legislation will have the following main objectives:

• expanding the scope of water protection to all waters, surface waters and groundwater

• achieving “good status” for all waters by a certain deadline

• water management based on river basins

• “combined approach” of emission limit values and quality standards

• getting the prices right

• getting the citizen involved more closely

• streamlining legislation

The progress on negotiating the future European water legislation seems to indicate a final adoption in 1999.
Management of the Ebro River Basin: Past, Present and Future
Authors: Comín Francisco A.
Published: May 2018

The Ebro River Basin (85,500 km2 in NE Spain) is characterised by a marked spatial heterogeneity of its geology, topography, climatology and land use. Many reservoirs (138, total water storage capacity of 6,837 hm3) and canals were constructed during this century for agricultural irrigation, electricity production and domestic use. Now, irrigation is allowed in 778,284 ha. There are also 40 aquaculture systems producing 35% of the total Spanish trout production. The mouth of the Ebro River (a 320 km2 delta area) is very productive for agriculture and fisheries. Industrial activities are localised in the upper NW and central parts of the Basin, causing low water quality in the fluvial system. Salinisation of land and river water occurs in the central part, because of salt dissolution, run-off from irrigated fields and groundwater abstraction. Present management is under the responsibility of different administrative agencies. A special agency is responsible for water control and distribution. A new management plan has been recently prepared with the major objective of satisfying the water demands, which are estimated as 7,000 hm3 yr−1 (18,200 hm3 yr−1 is the estimated available water). Most of this comes from agriculture for irrigation (6,310 hm3 yr−1), human use (313 hm3 yr−1) and industrial activities (414 hm3 yr−1). Water is also demanded from other basins. A total water demand of 10,771 hm3 yr−1 has been estimated in the Ebro Basin for the year 2015, maintaining similar proportions as before for the three major uses. In the future, saving and recycling water should be incorporated to the basin management as part of an strategy to distribute water as a function of existing and potential uses in the Basin and for promoting and re-adapting land and water uses to the availability of the resources, including inter-annual climatic fluctuations, and to preserve natural habitats.
The influence of hydrological pathways on the transport of the herbicide, isoproturon, through an underdrained clay soil
Authors: Heppell C. M. , Burt T. P. , Williams R. J. , Haria A. H.
Published: May 2018

This paper reports the findings of a 12 month field monitoring programme at Wytham (Oxfordshire, UK), which examined the leaching of the phenylurea herbicide, isoproturon, from an agricultural clay hillslope to the adjacent ephemeral stream. Isoproturon was shown to reach the drains (at 50 cm depth) through a combination of vertical and lateral macropore flow through wormholes and inter-pedal cracks. Seasonal changes in hydrological response were also observed at the site, with lateral flow through inter-pedal cracks providing an important route by which herbicide was transported during autumn and early spring when the clay soils were wetting up.

Concentrations of isoproturon in drainflow frequently exceeded the Environment Agency's (EA) non-statutory Environmental Quality Standard (EQS) of 20 μg/l for isoproturon in surface waters. Even under low intensity rainfall (< 1 mm/hr) the saturated region at the base of the hillslope was shown to conduct macropore flow containing significantly high concentrations of herbicide to the drain. The results of this study suggest that those regions close to surface waters which are areas of converging hydrological flow may be key contributors to the problem of isoproturon contamination of surface waters.
Best management practices applied to urban runoff quantity and quality control
Authors: Braune M. J. , Wood A.
Published: May 2018

South Africa currently has one of the highest rates of urbanisation in the world causing a significant increase in surface water runoff. This, in turn, causes increased flooding and a significant decrease in water quality due primarily to the accumulation of pollutants.

The need exists to manage urban stormwater runoff on an integrated catchment basis, thereby reducing the negative impact of urbanisation on the environment and quality of life.

In this paper, details on how existing problem areas can be identified and ranked, the use of Best Management Practices (BMPs) to reduce the impacts of urbanisation on the environment and the effectiveness of BMP's are discussed and illustrated, based on expertise gained from studies in South Africa as well as visits to the USA and Australia.
Assessing the performance of urban BMPs in Scotland
Authors: Jefferies C. , Aitken A. , McLean N. , Macdonald K. , McKissock G.
Published: May 2018

Best Management Practices (BMPs) in urban drainage have been promoted in Scotland for a number of years in response to the need to combat pollution arising from diffuse sources in urban areas. This has led to the construction of around one hundred BMP installations using both source and end of pipe control. These are principally in the East of Scotland, and the number is growing rapidly as education and knowledge increases.

A programme of investigations into the factors which influence the performance of the systems commenced in 1997. A range of types of BMP are under study including both source control and end of pipe systems. The sites have been divided into groups for which different depths of investigation are being undertaken. The programme involves a number of parallel investigations requiring field studies, data reviews and enquiries to confirm applicability and performance in situ. Many of the factors which influence the selection, installation and operation of a particular system are social, legal and administrative in addition to those which relate to its design and construction. The different strands of the study have been developed to ensure that all influences are identified and evaluated.
Evaluating measures to control the impact of agricultural phosphorus on water quality
Authors: Heathwaite Louise , Sharpley Andrew
Published: May 2018

Current issues in phosphorus loss from non-point sources are reviewed. The need to balance both source and transport control mechanisms in field approaches aimed at controlling P loss from agricultural land is explored. Other control measures such as P source manipulation are evaluated. A case is made for integrating work on P loss at various research scales, from plot to hillslope to catchment, and a simple field-scale model to evaluate the factors controlling P loss in surface runoff is presented.
Modelling the impacts of management practices on agricultural phosphorus losses to surface waters of Finland
Authors: Rekolainen S. , Grönroos J. , Bärlund I. , Nikander A. , Laine Y.
Published: May 2018

This paper presents the changes in cultivation practices in Finnish agriculture resulting from the Agri-Environmental Support Scheme of the Common Agricultural Policy of the European Union. Detailed data were collected by interviewing farmers in four different areas of the country. The potential impacts of changes in cultivation practices on phosphorus losses were assessed using a mathematical simulation model. The variables monitored were: fertilization, winter green cover and soil tillage methods in autumn. The use of fertilizers has decreased to meet the requirements of the support programme. Winter green cover has increased in areas to a minimum level of 30% of the cultivated area. However, the potential impacts on nutrient losses were small. There are two reasons for this: the increase in reduced tillage practices is likely to increase the loss of dissolved phosphorus in southern Finland, and the reduction of set-aside has led to slight increases in particulate phosphorus losses. However, the reduction in grassland fertilization rapidly decreased loss of dissolved phosphorus in northern Finland.
Wastewater Reuse for River Recovery in Semi-Arid Israel
Authors: Juanico Marcelo , Friedler Eran
Published: May 2018

Most of the water has been captured in the rivers of Israel and they have turned into dry river-beds which deliver only sporadic winter floods. In a semi-arid country where literally every drop of water is used, reclaimed wastewater is the most feasible water source for river recovery. Two topics are addressed in this paper: water quality management in rivers where most of the flowing water is treated wastewater, and the allocations of reclaimed wastewater required for the recovery of rivers and streams. Water quality management must consider that the main source of water to the river has a pollution loading which reduces its capability to absorb other pollution impacts. The allocation of treated wastewater for the revival of rivers may not affect negatively the water balance of the region; it may eventually improve it. An upstream bruto allocation of 122 MCM/year of wastewater for the recovery of 14 rivers in Israel may favor downstream reuse of this wastewater, resulting in a small neto allocation and in an increase of the water resources available to the country. The discharge of effluents upstream to revive the river followed by their re-capture downstream for irrigation, implies a further stage in the intensification of water reuse.
The Use of Computational Fluid Dynamics for Improving the Design and Operation of Water and Wastewater Treatment Plants
Authors: Brouckaert C. J. , Buckley C. A.
Published: May 2018

Computational Fluid Dynamics (CFD) studies of a secondary clarifier at Durban's Northern Wastewater Treatment Works, and of a clarifier at the potable water treatment plant at Umzinto, a small town near Durban, have been undertaken with a view to improving their load capacities. In both cases the units are located in relatively old treatment plants, which face continually increasing loads due to population growth. Increasing the capacity of existing equipment, rather than installing new equipment, constitutes an efficient use of development capital. Although the two clarifiers have considerable design differences, the CFD studies indicated remarkably similar circulating flows, which concentrate up-flow near the outer wall of the clarifier in the region of the clarified water overflow weirs. Baffles were designed to disrupt the circulation so as to distribute up-flow over a wider area, thereby reducing the maximum vertical velocities. In the case of the wastewater secondary clarifier, the modification has been implemented, and evaluated in comparative tests involving an otherwise identical unmodified clarifier. In the case of the potable water clarifier, the modification has still to be implemented.
Continuous Ozonation of Polycyclic Aromatic Hydrocarbons in Oil/Water-Emulsions and Biodegradation of Oxidation Products
Authors: Kornmüller A. , Wiesmann U.
Published: May 2018

The continuous ozonation of polycyclic aromatic hydrocarbons (PAH) was studied in a two stage ozonation system followed by serobic biological degradation. The highly condensed PAH benzo(e)pyrene and benzo(k)fluoranthene were oxidized selectiely in synthetic oil/water-emulsions. The influence of the ozone mass transfer gas-liquid on the reaction rate of benzo(k)fluoranthene was studied for process optimization. The dissolved ozone concentration is influenced by temperature to a higher degree than the reaction rate of PAH. In dependence on pH, PAH oxidation occurs by a direct reaction with ozone inside the oil droplets. Two main ozonation products of benzo(e)pyrene were quantified at different retention times during ozonation and their transformation could be shown in the biological treatment step.