bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of denitrification by the ordinary heterotrophic organisms in an NDBEPR activated sludge sytem
Authors: Drysdale G. D. , Kasan H. C. , Bux F.
Published: May 2018

The purpose of this study was to isolate and characterise the ordinary heterotrophic organisms (OHOs) present in a NDBEPR system in order to gain a better understanding of the organisms involved in denitrification as well as a more holistic and accurate evaluation of the OHO fraction attributable to denitrification in such a system. Heterotrophic bacteria were isolated from the pre- and secondary anoxic zones of the Darvill NDBEPR process and characterised according to their ability to reduce nitrates and/or nitrites under anoxic conditions. Results showed that the OHO fraction is more complex than currently accepted and, with respect to denitrification, can be more accurately subdivided into five functional groups, four of which interactively contribute to denitrification occurring in the system and one group that are non-denitrifying. These groups were defined as true denitrifiers (bacteria capable of both nitrate and nitrite reduction), incomplete denitrifiers (bacteria that reduced nitrates to nitrites with no further reduction of the nitrites produced), incomplete-nitrite reducers (bacteria capable of both nitrate and nitrite reduction, however, exhibiting severe inhibition of nitrite reduction by nitrates), exclusive nitrite reducers (bacteria only capable of reducing nitrites) and non-denitrifiers (bacteria not capable of nitrate or nitrite reduction).
Sludge hydrolysate as a carbon source for denitrification
Authors: Aravinthan V. , Mino T. , Takizawa S. , Satoh H. , Matsuo T.
Published: May 2018

External carbon sources such as methanol and acetate are applied in order to improve the denitrification efficiency in biological nitrogen removal processes. Excess sludge wasted from the treatment plants contains organic carbon that could be used as a feasible carbon source for denitrification. However, the excess sludge needs to be hydrolyzed first before being utilized as a carbon source. The objective of this research is to evaluate the biodegradability of the sludge hydrolysate obtained using alkaline, acid, autoclaved and combined solubilization methods. The experimental results suggest that the method of solubilization has an impact on the biodegradability of sludge hydrolysate. Autoclaved alkaline sludge hydrolysate gave the fastest denitrification rate (250 mgN/gMLSSCOD/d) due to fastest protein degradation (247 mgCOD/gLSSCOD/d) and other COD degradation rates (370 mgN/gmlsscod/d). Alkaline, autoclaved and acid autoclaved sludge hydrolysates gave nearly the same denitrification rates (185 to 200 mgN/gMLSSCOD/d). Protein degradation rate was the highest for autoclaved alkaline sludge hydrolysate (247 mgCOD/gMLSSCOD/d) whereas carbohydrate degradation rate was the fastest for autoclaved acid sludge hydrolysate (91 mgCOD/gMLSSCOD/d). For the same enzyme activity, different carbohydrate and protein degradation activities have been found suggesting the presence of easily and slowly biodegradable portions in them.
Field monitoring of toxic organic pollution in the sediments of Pearl River estuary and its tributaries
Authors: Fu J. , Wang Z. , Mai B. , Kang Y.
Published: May 2018

Field monitoring of the toxic organic compounds (PCBs, PAHs, organochlorine pesticides) in the top sediments of Pearl River Estuary and its up-streams were made. It was found that the highest concentrations of these toxic organic compounds occurred in the sediment sampled at Macau inner harbor (ZB013), which is a sink of suspended fine particles transported from the upstream waterways. Because of the affinity of the hydrophobic organic compounds (PAHs, PCBs) for the solid phase, these fine particle depositions led to accumulation of these compounds in the sediment of Macau. The atmospheric dry deposition may be another source of the toxic organic pollution in the sediment.
Statistical comparisons of the no-observed-effect concentration and the effective concentration at 10% inhibition (EC10) in algal toxicity tests
Authors: Shieh J.-N. , Chao M.-R. , Chen C.-Y.
Published: May 2018

Batch-type algal toxicity tests were conducted to evaluate the low toxic effects of metal toxicants. Both the no-observed-effect concentration (NOEC) and the effective concentration at 10% inhibition (EC10) were calculated and compared. The results of this study indicate that, for algal toxicity tests, NOEC offers better protection to the test organisms than EC10. In addition, the consistency of NOEC is found to depend on the response endpoints measured. A cut-off-value approach is proposed to determine whether NOEC or EC10 should be chosen for estimating low toxic effects. For a specific toxicity test, the average cut-off value directly indicates the magnitude of the square root of the within-group-variance. A precise test associated with small within-group-variances also produces relatively small average cut-off value (say, less than 10% of the growth reduction). This average value provides useful information on the minimum protection that can be offered by the NOEC.
Performance of triple ditch: effects of duration and periodic operation programs
Authors: Ma L. M. , Wang H. W. , Liu Y. , Jing Z. G.
Published: May 2018

The periodic variation of operation states in triple ditch (BIO-DENITRO process) was investigated in a pilot-scale and a full-scale triple ditch treating raw wastewater containing 70% petrochemical wastewater and 30% domestic wastewater. Mathematical models describing the periodic variation of activated sludge concentrations in each ditch were proposed based on theoretical analysis and were verified in the pilot-scale and full-scale triple ditches respectively. The existence of optimal cycle time and time arrangement of periodic operation programs were demonstrated and discussed according to the mathematical models and the experimental results of the pilot-scale triple ditch operated in four different stages. Four rulers determining the duration and operation programs are suggested.
Role of storage phenomena on removal of different substrates during pre-denitrification
Authors: Majone M. , Beccari M. , Dionisi D. , Levantesi C. , Renzi V.
Published: May 2018

Removal mechanisms of different substrates during the pre-denitrification step of an anoxic/aerobic sequencing process are studied. Biomass was cultivated in an anoxic/aerobic SBR and fed with a mixture of low and high molecular weight compounds. Substrate removal mechanisms are studied by means of batch tests, performed under anoxic conditions. The dynamic response to a spike of four different substrates (acetate, glucose, glutamic acid and ethanol) is described by simultaneously considering substrate and electron acceptor removal, and PHB and carbohydrates storage. PHB storage is a relevant mechanism during the removal of acetate and ethanol, while glucose is removed mainly by carbohydrate storage.
Carbon and nitrogen removal from a wastewater of an industrial dairy laboratory with a coupled anaerobic filter-sequencing batch reactor system
Authors: Garrido J. M. , Omil F. , Arrojo B. , Méndez R. , Lema J. M.
Published: May 2018

A set of two reactors, an Anaerobic Filter (AF) of 12 m3 and a Sequencing Batch Reactor (SBR) of 28 m3, coupled in series, were used to treat the wastewaters from an industrial milk analysis laboratory. The characteristics of these effluents are similar to those discharged by dairy factories (average values around 10 kg COD/m3 and 0.20 kg N/m3). These wastewaters were produced as the result of the final mixture of the analysed milk samples, with a very high organic load, and other low strength effluents, such as sewage and other minor liquid streams generated in the laboratory. Two microbial growth inhibitors, sodium azide and chloramphenicol, were systematically added to the milk before its analysis. Preliminary results have shown that these compounds did apparently not inhibit the methanogenic activity of the anaerobic sludge. Toxicity determination, using the Microtox method, resulted in EC50 values for the wastewaters of 20 g/L, whereas the final effluent from the SBR was non toxic. A maximum OLR of 8 kg COD/m3·d was treated in the AF, being the maximum OLR in the SBR around 1.5-2 kg COD/m3·d. During operation, the soluble COD of the final effluent from the SBR was usually below 200 mg/L, and total nitrogen (mainly nitrate) below 10 mg N/L. Assimilation of nitrogen for growth and nitrification-denitrification were the main mechanisms of nitrogen removal from the wastewater. In the anaerobic system between 50-85% of the organic matter was converted into methane, being the remaining COD and most of the nitrogen removed in the suspended culture system. Overall COD removal in the treatment system was 98% and the nitrogen removal up to 99%. The combination of the AF and the SBR was advantageous resulting in a lower energy consumption and sludge generation in the treatment system.
Modelling biological phosphorus removal from a cheese factory effluent by an SBR
Authors: Ky R. C. , Comeau Y. , Perrier M. , Takacs I.
Published: May 2018

A mathematical model, named A3DX, based on ASM3(A3) for C and N removal, on the bio-P metabolic model of the Technological University of Delft (D), and on extra processes (X) for chemical and biological phosphorus removal, was developed and used to simulate the treatment of a fermented cheese factory effluent by a sequencing batch reactor (SBR). Experimental data obtained from a pilot-scale SBR were used to calibrate the model. The model calibration was performed by changing a minimal number (four) of default values for parameters, and by introducing a Monod function to account for magnesium limitation. This study suggests that the value of stoichiometric and kinetic model parameters determined with municipal effluents or enriched bio-P cultures can be reasonably used with some agro-industrial effluents with minimal parameter adjustment for calibration.
Strategies to enhance the biodegradation of toxic compounds using discontinuous processes
Authors: Buitrón G. , Soto G. , Vite G. , Moreno J.
Published: May 2018

This study presents two strategies used to enhance the biological degradation of phenolic wastewaters. In the first one the operation of a sequencing batch biofilter added with granular activated carbon (SBB-AC) was studied. The second strategy presents the results of the automation of a sequencing batch reactor in order to optimize the reaction phase. In this case, the dissolved oxygen was employed to monitor and control the reactor. The results of the SBB-AC system, based on the configuration of the reactor, type and size of activated carbon and size of the packing material, are discussed. The system biodegraded efficiently (total phenol removals as high as 97%) high concentrations (600 mg/l) of a mixture of phenol, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. Maximal eliminated loads of 4.33 kg COD/m3-d were achieved. For the second strategy, the applicability of an optimal control for a SBR using the dissolved oxygen as the measured variable was demonstrated. When the reactor was operated under the time-optimal control strategy, the degradation time of 4-chlorophenol was reduced. A very satisfactory operation of the reactor was observed, since the removal efficiencies were around 99%.
Influence of HRT (hydraulic retention time) and SRT (solid retention time) on the hydrolytic pre-treatment of urban wastewater
Authors: Ligero P. , De Vega A. , Soto M.
Published: May 2018

This work presents the results obtained from a study on the pretreatment of urban wastewater using a digester that acted as a system for the retention of solids (sedimentation-filtration), hydrolysis of the retained solids and acidification of the dissolved substances. After start-up (Phase I), the digester was operated at hydraulic retention times (HRT) of 4.4, 3.4 and 2.2 h and at solid retention times (SRT) of 24, 16 and 14 d, during Phases II, III and IV, respectively. The retention and removal of suspended solids (SS) was maintained slightly above 60%, independently of HRT and SRT. Conversely, eliminated chemical oxygen demand (COD) decreased slightly upon reducing HRT and SRT. The influence of these two parameters on the generation of volatile fatty acids (VFA) is more notable, reaching effluent VFA concentration of 29 (Phase II), 96 (Phase III), and 107 (Phase IV) mg COD/l. VFA to SS generation ratios were 0.13 (II), 0.35 (III), and 0.48 (IV) g VFACOD/g SS added. Optimum values were reached at an HRT of 2.2 h. Taking 100 kg influent COD as a base, the conversion of different kinds of COD was as follows (in kg influent:kg effluent): VFACOD (4:17), non-VFA soluble COD (45:23), VSSCOD (51:23). Simultaneously to these conversions, 2 kg VSSCOD are generated as purge stream and 35 kg COD are eliminated during the process.
Psychrophilic one- and two-step systems for pre-treatment of winery waste water
Authors: Kalyuzhnyi S. V. , Gladchenko M. A. , Skylar V. I. , Kizimenko Ye. S. , Shcherbakov S. S.
Published: May 2018

The operation performance of a single and two (in series) laboratory UASB reactors (working volume of 2.7 l, recycle ratio varied from 1:1 to 1:18) treating diluted wine vinasse was investigated under psychrophilic conditions (4-10°C). For a single UASB reactor seeded with granular sludge, the average organic loading rates (OLR) applied were 4.7, 3.7 and 1.7 g COD/l/d (hydraulic retention times (HRTs) were around 1 d) at 9-11, 6-7 and 4-5°C, respectively. The average total COD removal for preacidified vinasse wastewater was around 60% for all the temperature regimes tested. For two UASB reactors in series, the average total COD removal for treatment of non-preacidified wastewater exceeded 70% (the average OLRs for a whole system were 2.2, 1.8 and 1.3 g COD/l/d under HRTs of 2 days at 10, 7 and 4°C, respectively). In situ determinations of kinetic sludge characteristics (Vm and Km) revealed the existence of substantial mass-transfer limitations for the soluble substrates inside the reactor sludge bed. Therefore an application of higher recycle rations is essential for enhancement of UASB pre-treatment under psychrophilic conditions. The produced anaerobic effluents were shown to be efficiently post-treated aerobically - final effluent COD concentrations were around 0.1 g/l.
Evaluation of an anaerobic/aerobic system for carbon and nitrogen removal in slaughterhouse wastewater
Authors: Núñez L. A. , Martínez B.
Published: May 2018

In this work the performance of an anaerobic UASB reactor coupled with an activated sludge reactor for carbon and nitrogen removal in slaughterhouse wastewater is investigated. Periods with and without recirculation of aerobic effluent over 165 days are analysed. Working with a recirculation ratio of 2, removal efficiencies up to 90% and 65% are obtained for DQO and total nitrogen (TN), respectively. Higher recirculation ratios caused severe washout of active biomass in both reactors due to the high hydraulic loading rates applied. Denitrification in the UASB reactor was complete, with no nitrite accumulation and mainly to nitrogen gas. Significant decreases in COD removal efficiencies in the UASB reactor were observed at recirculation ratio of 2. Sudden decreases in total nitrogen efficiencies were related to inhibition process of nitrifying microorganisms, especially at high recirculation ratios.
Mechanism of radiation purification of polluted water and wastewater
Authors: Pikaev A.K.
Published: May 2018

The paper summarizes the results of the studies on radiation purification of polluted water and wastewater conducted in the author's laboratory in cooperation with other institutions. The removal of heavy metals (cadmium, lead, chromium and mercury) from water and wastewater, the purification of wastewater from surfactant and petroleum products, molasses distillery slops, municipal wastewater in the aerosol flow, river water from colored natural organic pollutants, wastewater of dyeing complex and paper mill, the decomposition of some dyes, hydrogen peroxide, chlorine-containing organic compounds, formic acid, etc. were investigated in detail. As a rule, electron-beam treatment in combination with ordinary methods (biological, coagulation, adsorption, flotation, etc.) was used. The main attention is paid to the mechanism of purification of the studied systems. The role of redox reactions of primary products of water radiolysis and secondary short-lived species formed from pollutants, formation of precipitates capturing the pollutants etc. is discussed.
Subcritical wet oxidation of municipal sewage sludge: comparison of batch and continuous experiments
Authors: Lendormi T. , Prevot C. , Doppenberg F. , Foussard J.N. , Debellefontaine H.
Published: May 2018

Wet oxidation in subcritical conditions is a new alternative to usual routes for sewage sludge treatment and it complies with environmental standards. The paper presents tests carried out on a batch reactor and on a continuous pilot unit, treating municipal sewage sludge. A method is proposed that shows that the oxidation efficiency in a continuous reactor can only be easily predicted from the residence time distribution and batch tests results. Nevertheless, a partial settling of the solid residue in the continuous bubble column reactor is evident, and it increases the solid residence time and then decreases its organic content with respect to a similar batch test. In addition, these results highlight the considerable influence of temperature in the oxidation reactor and of the type of sewage sludge which is treated. At temperatures around 240deg;C, foaming can seriously impair the operation of the continuous reactor, because of the presence of non-degraded fatty compounds and surfactants. Moreover, the COD reduction is limited to 70%. On the contrary, at 300deg;C, COD removal efficiency greater than 80% is achieved without any catalyst additive and, in addition, only highly biodegradable compounds remain in the oxidised liquor.
Highly concentrated phenolic wastewater treatment by heterogeneous and homogeneous photocatalysis: mechanism study by FTIR-ATR
Authors: Araña J. , Tello-Rendón E. , Doña-Rodríguez J.M. , Valdés do Campo C. , Herrera-Melidán J.A. , González-Díaz O. , Pérez-Peña J.
Published: May 2018

The degradation of high phenol concentrations (I g/L) in water solutions by TiO2 photocatalysis and the photo-Fenton reaction has been studied. From the obtained data it may be suggested that degradation of phenol by TiO2-UV takes place onto the catalyst surface by means of peroxo-compounds formation. At low phenol concentrations other mechanism, the insertion of OH• radicals, may be favored. On the other hand, highly concentrated phenol aqueous solutions treatment by the photo-Fenton reaction gives rise to the formation of polyphenolic polymers. These seem to reduce the process rate. Degradation intermediates have been identified by HPLC and FTIR. The FTIR study of the catalyst surface has shown infrared bands attributable to different chemisorbed peroxo-compounds, formates, ortho-formates and carboxylates that can inactivate the catalyst.
Evaluation of appropriate system for reclaimed wastewater reuse in each area of Tokyo using GIS-based water balance model
Authors: Aramaki T. , Sugimoto R. , Hanaki K. , Matsuo T.
Published: May 2018

The appropriate type of reclaimed wastewater reuse system in each area of Tokyo was evaluated from the aspect of economic efficiency, using a GIS-based water balances model. The following four reclaimed wastewater reuse systems and conventional waterworks and sewerage system were evaluated; “Rain water storage and use system”, “Onsite wastewater treatment and reuse system”, “Sewage treatment and reuse at an intermediate point on the sewer pipe” and “Treated water supply system in sewage treatment plant”. In the case that we install them to office and residential buildings, the supplied volume by reclaimed wastewater reuse systems is 693 thousands m3/d, this corresponds to 15% of total water demand in the area. Furthermore, the effects of the following scenarios brought about by technological innovation in water treatment were investigated; the case that flush water in toilet and wastewater from kitchen are also available as source in a “onsite wastewater treatment and reuse system” and the casethat reclaimed water is used for laundering in residential buildings. When reclaimed water is used for laundering in residential buildings, the supplied volume by these systems increases to 814 thousand m3/d in the case that these systems are installed to office and residential buildings.
Semiconductor-mediated photocatalysed degradation of two selected pesticide derivatives, terbacil and 2,4,5-tribromoimidazole, in aqueous suspension
Authors: Muneer M. , Bahnemann D.
Published: May 2018

The photocatalysed degradation of two selected pesticide derivatives, namely 3-tert-butyl-5-chloro-6-methyluracil (terbacil) and 2,4,5-tribromoimidazole (TBI) has been investigated in aqueous suspensions of titanium dioxide (TiO2) under a variety of conditions employing a pH-stat technique. The degradation was studied by monitoring the change in substrate concentration of the model compound employing HPLC analysis, and the decrease in total organic carbon (TOC) content, respectively, as a function of irradiation time. The degradation kinetics were studied under different conditions such as reaction pH, substrate and photocatalyst concentration, type of TiO2 photocatalyst and the presence of alternative additives such as H2O2, KBrO3 and (NH4)2S2O8 besides molecular oxygen. The degradation rates and the photonic efficiencies were found to be strongly influenced by the above parameters. Toxicity tests for the irradiated samples of the pesticide derivatives measuring the luminescence of bacteria Vibrio fischeri after 30 minutes of incubation were also performed.
Environmental conditions and pathogen removal in macrophyte- and algal-based domestic wastewater treatment systems
Authors: Awuah E. , Anohene F. , Asante K. , Lubberding H. , Gijzen H.
Published: May 2018

The environmental conditions and pathogen removal in macrophyte (Pistia stratiotes and Lemna paucicostata) and algal-based wastewater treatment systems were determined over a period of 29 days under tropical conditions. The experiment was conducted on a batch scale in 4.5 plastic containers immersed in moist sand beds. A control of raw sewage stored under dark conditions was included. Environmental conditions such as pH, temperature DO and conductivity and heterotrophic and faecal enterococci populations were monitored five times a week at 8, 12 and 20 GMT. BOD was monitored once a week for five weeks. Average temperatures within the systems ranged between 28.3°C in the control to 30.6°C in the algal-based system. Low pH levels of pH of 4.5 and DO levels of 3 mg/L were recorded in the water lettuce treatment systems. High pH levels around 10.5 and DO levels of about 20 mg/L were observed in the algal-based system. The control and duckweed system remained neutral. All treatment systems performed equally well in pathogen removal and BOD reduction. The BOD decreased from 130mg/L to 5.0, 7.5, 10 and 15 mg/L in the duckweed, water lettuce, control and algal based treatment systems respectively. The faecal enterococci population decreased from 1.18×105 /ml to values below 100/ml in all treatment systems.
Quantification of the bond energy of bacteria attached to activated sludge floc surfaces
Authors: Mikkelsen L. H. , Nielsen P. H.
Published: May 2018

The great majority of activated sludge bacteria exist incorporated in flocs. The increase in dispersed bacteria when exposed to increasing turbulent shear rates has been successfully modelled by a model assuming that the adhesion and erosion of cells may be considered in analogy to ordinary chemical phase transitions. By this adhesion-erosion model (AE-model), an “enthalpy” of cell adhesion can be estimated, and this value in turn determines the range of shear rates in which erosion of cells predominates. Application of the model has indicated that only a mass fraction less than ca. 6-17% may be released from activated sludge, even when exposed to a severe turbulent environment, i.e. only a small fraction of the flocs is dispersible by means of erosion by turbulence. The shear sensitivity and the dispersible floc fraction were found to depend on the floc composition. A net decrease in the floc EPS content during anaerobic sludge stabilisation causes a dramatic increase in the dispersed fraction, indicating the important role of EPS for the floc strength. It was found also that activated sludge cells do not reflocculate completely after exposure to high shear rates. This may be an indication that the cohesion energy of bacteria growing in colonies is greater than the energy of the more stochastic adhesion of dispersed cells to floc surfaces. It could also be another indicator of the importance of entanglement forces, which do not reform instantly, once broken. When the bond strength of cell attachment to sludge surfaces is altered by changes in the chemical environment, this may cause a change in the dispersible floc fraction as well as a change in the shear range of erosion. When the shear sensitivity constant kSS is adopted for sludge characterisation, an increased degree of dispersion under standard test conditions will result in increased shear sensitivity estimates. The shear sensitivity may be used for the estimation of en equivalent change in the Gibb's energy of cell adhesion (Δ(ΔGad/RT)).
Wastewater management in Greece: experience and lessons for developing countries
Authors: Tsagarakis K. P. , Mara D. D. , Angelakis A. N.
Published: May 2018

Technologies to treat wastewater are now well established and are capable of producing almost any degree of purification. The main issue surrounding the selection of a given process lies in deciding which is the most appropriate and applicable technology for the particular social, political and economic environment. This paper concentrates on the development of the municipal wastewater treatment sector in Greece. It examines the deficiencies and problems arising from the implementation of wastewater management policies and makes a number of suggestions and recommendations. The areas considered include, among others, historical development, economic development and pollution control, key issues for wastewater treatment policies and lessons applicable to developing countries. It is hoped that this study will be a valuable source of information for countries embarking on nationwide sanitation projects.
Agarose hydrogels as EPS models
Authors: Strathmann M. , Griebe T. , Flemming H.-C.
Published: May 2018

For investigating the influence of extracellular polymeric substances (EPSs) on biofilm properties, artificial models of defined composition and structure can be very helpful. Different immobilised cell systems can be useful in the fitting of experimental results. Two different types of artificial EPS matrix model were developed earlier. Homogeneous agarose beads (50-500 μm diameter) and porous beads (260 μm mean diameter) containing pores with diameters from 10 to 80 μm (28 μm on average), allowed the embedding of cells, particles and typical EPS matrix components such as proteins and polysaccharides. In this paper, some physico-chemical properties of the artificial EPS matrices were described and compared with results known from natural EPS. The stability of the artificial matrix polymer against solution in the aqueous medium was studied in batch experiments. The water binding and water retaining capabilities of the EPS models were investigated by drying and re-swelling experiments. The simulation of protective effects of the artificial EPS matrix against toxic substances like biocides in comparison to such known protective effects of the EPS of native biofilms were proved by the application of sodium hypochlorite (0.5 mg/l, 30 min) and subsequent microscopic investigation of the cell population after LIVE/DEAD staining (Molecular Probes).
Effect of carbohydrate and protein in the EPS on sludge settling characteristics
Authors: Shin H.-S. , Kang S.-T. , Nam S.-Y.
Published: May 2018

EPSs have been believed to play a bonding role in microbial floc formation. However, the precise role is not well known. In this study, sludge settling characteristics and the carbohydrate to protein ratio in the EPS were tested at various airflow rates. Sludge was collected from three modified sequencing batch reactors (MSBRs), which were operated with airflow rates of 0.8 L/min, 2 L/min and 4 L/min, respectively. During the operation periods, the reactor operated at an airflow rate of 0.8 L/min showed a sludge volume index (SVI) of 80 to 90 mL/g and a constant ratio of carbohydrate to protein in the EPS, while a significant increase of this ratio and the SVI occurred in the other reactors. High airflow rate increased the amount of carbohydrate in the EPS, but the protein level was almost constant for reactors with airflow rates of 2 L/min and 4 L/min. The higher ratio of carbohydrate to protein caused the bulking of the sludge; hence it was not favourable for sludge settling. The ratio of carbohydrate and protein in the EPS is inferred to be essential for solid floc formation.
Adequate model complexity for scenario analysis of VOC stripping in a trickling filter
Authors: Vanhooren H. , Verbrugge T. , Boeije G. , Demey D. , Vanrolleghem P. A.
Published: May 2018

Two models describing the stripping of volatile organic contaminants (VOCs) in an industrial trickling filter system are developed. The aim of the models is to investigate the effect of different operating conditions (VOC loads and air flow rates) on the efficiency of VOC stripping and the resulting concentrations in the gas and liquid phases. The first model uses the same principles as the steady-state non-equilibrium activated sludge model SimpleTreat, in combination with an existing biofilm model. The second model is a simple mass balance based model only incorporating air and liquid and thus neglecting biofilm effects.

In a first approach, the first model was incorporated in a five-layer hydrodynamic model of the trickling filter, using the carrier material design specifications for porosity, water hold-up and specific surface area. A tracer test with lithium was used to validate this approach, and the gas mixing in the filters was studied using continuous CO2 and O2 measurements. With the tracer test results, the biodegradation model was adapted, and it became clear that biodegradation and adsorption to solids can be neglected. On this basis, a simple dynamic mass balance model was built. Simulations with this model reveal that changing the air flow rate in the trickling filter system has little effect on the VOC stripping efficiency at steady state. However, immediately after an air flow rate change, quite high flux and concentration peaks of VOCs can be expected. These phenomena are of major importance for the design of an off-gas treatment facility.
Diffuse sources of heavy metals in the Rhine basin
Authors: Mohaupt V. , Sieber U. , van den Roovaart J. , Verstappen C. G. , Langenfeld F. , Braun M.
Published: May 2018

An estimate of diffuse sources of heavy metals (Hg, Cd, Cu, Zn, Pb, Cr, Ni) in the Rhine catchment stressed the urban storm water discharges in the German part and drainage flow in the Dutch part as the most important pathways. Additional sources are erosion and, to a far lesser extent, atmospheric deposition on open water areas. All other pathways were of minor importance. Meanwhile, after reduction of the point sources by between 72-95%, the diffuse sources dominate the total emissions. For several metals the anthropogenic diffuse sources amounted to 40-80%, the point sources to 15-40% and the geogeneous sources to 5-40%. The estimated inputs sufficiently agreed with the loads of the river Rhine. For the estimation, mean values were used for the water masses and the substance concentrations of the different hydrological pathways. It is recommended to undertake further studies on diffuse sources of heavy metals in urban areas and on the possibilities to improve urban storm water management. The calculation methods and the recommendations of the International Commission for the Protection of the Rhine (ICPR) are explained in detail.
Development and evaluation of a mathematical model for the study of sediment-related water quality issues
Authors: Zeng W. , Beck M. B.
Published: May 2018

A mathematical model (Sediment-Transport-Associated Nutrient Dynamics - STAND) has been developed for the study of sediment-associated water quality issues. The model is intended to simulate changes of water composition associated with sediment behavior. It has a 3-level structure. The first level accounts for the hydraulics of open-channel flow. The second computes sediment transport potential and actual rates based on the information provided by the first level. A non-equilibrium approach is used. In the third level, changes of nutrient concentrations along a studied river are computed with the consideration of nutrient transport, adsorption/desorption, and release. In order to calibrate the model, field data were collected from the Oconee River, a major tributary of the Altamaha River in Georgia, USA. Two stations, approximately 17 km distant from each other, were established along the river for the purpose of data collection. Observations of the river's hydraulics, suspended sediment, and water quality (mainly ortho-phosphate, nitrate, temperature, specific conductivity, oxidation-reduction potential, dissolved oxygen, and pH) were collected at the two stations. Another data set collected along a major tributary of the Yellow River in China was also used for calibration of the model's hydraulics and sediment transport parts. Calibration and validation results are encouraging, which suggests STAND may be a useful tool for the thorough study and understanding of nutrient dynamics associated with sediment behaviour.
Modeling of a reactive primary clarifier
Authors: Gernaey K. , Vanrolleghem P. A. , Lessard P.
Published: May 2018

Even though many models have been proposed for primary clarification, none is directly compatible with the ASM1. The objective of this paper is to present the development of a reactive primary clarifier model to be used in a wastewater treatment plant simulator (WEST). A model simulating COD behavior has been developed based on the Takacs model, and was tested with full-scale data. Particulate effluent COD was well described but problems occurred predicting the underflow suspended solids concentration. The model had to be upgraded with a residence time and a flocculation term to simulate the behavior of soluble COD. An ammonification term was added to the model, resulting in an improved model fit on effluent ammonium.
Non-point pollution from China's rural areas and its countermeasures
Authors: Yin C.-Q. , Yang C.-F. , Shan B.-Q. , Li G.-B. , Wang D.-L.
Published: May 2018

Most lakes in the eastern part of China are eutrophic and non-point pollution accounts for more than half of the nutrient load to the lakes and reservoirs. Some efforts have been made to reduce the non-point source pollution in the catchments of sensitive water bodies. Technologies for the control of non-point pollution in Chinese rural areas are multipond systems, biogas fermentation, hilly area ecological agriculture, constructed wetlands, ecotone engineering and others. They are effective in the removal of nutrients from the runoff water or reduction of waste, and they are used with multi-purposes. To control non-point pollution, the cooperation with farmers and other residents in the countryside is the key to success, and the program has to consider their benefits. There are still many difficulties with its control, and more efforts are needed to develop suitable technologies and environmental education.
Comparison of nutrient budgets betwen three forested mountain watersheds on granite bedrock
Authors: Kunimatsu T. , Hamabata E. , Sudo M. , Hida Y.
Published: May 2018

The budgets of nutrients and major ions between the input flux from atmospheric deposition and the output flux to streams were measured on three forested small mountain watersheds, Aburahi-N (23.8 ha), Aburahi-S (3.8 ha, 2 km south from Aburahi-N) and Myokoji (1.77 ha, 28 km northwest from Aburahi-N), located at 34-35 N and 136 E around the central part of Japan. The bedrock of the watersheds is granite. The main vegetation of Aburahi-N and Aburahi-S was planted with Japanese cypress (Chamaecyparis obtusa Sieb. et Zucc), and Myokoji was a secondary forest growing deciduous broadleaf trees and Japanese red pine. The chemical analysis of the stream waters was carried out once a week at Aburahi-N from 1987 to 1991, at Aburahi-S from 1995 to 1998, and at Myokoji from 1991 to 1993. Wet and dry depositions were collected every month at Aburahi-N. The annual mean concentrations of total nitrogen (TN) of the stream water of Aburahi-N, Aburahi-S and Myokoji were 0.408, 0.614 and 0.349 mg/l, respectively, total phosphorus (TP) contents were 0.0074, 0.0046 and 0.0096 mg/l, and the potassium ion (K+) contents were 0.83, 0.49 and 0.77 mg/l. The average annual output fluxes of TN from the watersheds of Aburahi-N, Aburahi-S and Myokoji were calculated to be 5.85, 4.10 and 12.7 kg/ha/y, TP 0.131, 0.045 and 0.280 kg/ha/y, K+ 9.63, 3.23 and 9.70 kg/ha/y, and discharge 1062, 508 and 1265 mm/y, respectively. The annual outputs tended to increase as the annual precipitation increased. The average annual input fluxes of TN, TP and K+ for six years from 1990-1998 were 12.5, 1.31 and 7.64 kg/ha/y, respectively, and the precipitation averaged 1449 (1019-1947) mm/y.
Application of mathematical tools to improve the design and operation of activated sludge plants. Case study: the new WWTP of Galindo-Bilbao Part I: Optimum design
Authors: Rivas A. , Ayesa E. , Galarza A. , Salterain A.
Published: May 2018

This paper presents a mathematical formulation for the optimum design of a new activated sludge WWTP. The WWTP optimum design problem has been formulated as a Mathematical Programming problem, which is solved through a nonlinear optimisation method. The plant model has been based on the ASM1. The minimum volume of the biological reactors and the minimum total cost (including construction and exploitation costs) have been considered as optimisation criteria. Some practical results are also included, using as a case study the design of the second stage of the Galindo-Bilbao WWTP.
System analysis for optimal control of a wastewater treatment benchmark
Authors: Vrečko D. , Hvala N. , Kocijan J. , Zec M.
Published: May 2018

The paper presents an analysis and optimisation of a wastewater treatment benchmark. The benchmark is a simulation environment defining a plant layout, simulation model, influent data, test procedures and evaluating criteria that should be used for comparing different control strategies. In this paper an analysis of the benchmark which addresses the influences of potential manipulated variables on control performance under different operating conditions is presented. In the study optimisation is used to define the optimal values of the manipulated variables under constant as well as dynamic influent conditions. The results indicate that such an analysis and optimisation give important information about the manipulated variables under varying influent conditions and consequently about possible control strategies.
Model system for the management of nitrogen leaching at the scale of river basins and regions
Authors: Wendland F. , Kunkel R. , Grimvall A. , Kronvang B. , Müller-Wohlfeil D. I.
Published: May 2018

In the framework of the EU-project RANR (Regional analysis of subsurface nitrogen retention and its impact on the nitrogen export from land to sea) a model system was developed to estimate groundwater-borne nitrogen inputs into river systems. The core of this model system is composed of a soil nitrogen leaching model (SOIL-N) and a groundwater residence time/denitrification model (WEKU). The application of the model system was carried out for the study catchment areas of the Uecker basin (ca. 2400 km2, Germany) and the Gjern basin (ca. 200 km2, Denmark). For both catchment areas, the modelled average nitrogen loads leached into the groundwater were about 40 kg N/ha a, while the remaining groundwater-borne nitrogen intake to rivers was quantified to an average of about

2 kg/ha a. The comparision with observed groundwaterborne riverine nitrogen loads showed a very good agreement, proofing the key role nitrogen retention in groundwater plays in the two catchment areas. With regard to the generalisationand transfer of the SOIL-N/WEKU model concept we assume that the model can be applicated in catchment areas in the European Pleistocene Lowland, which ranges from the Netherlands in the west to the Baltic States and the Ukraine in the east.
Georeferenced regional simulation and aquatic exposure assessment
Authors: Matthies M. , Berlekamp J. , Koormann F. , Wagner J.-O.
Published: May 2018

A simulation model system of the waste water pathways and the aquatic fate assessment is coupled to a discrete digitized river network. Temporal concentration distributions of down-the-drain chemicals are calculated from variable and uncertain input data and compared to monitoring data. The accuracy of the predictions are within a factor of three for the studied pilot catchments. Spatial distributions of the whole catchment give stochastic information on a regional basis for probabilistic risk assessments.
Ecological concern as a factor in the optimal attenuation of diverse stressor sources in a stream
Authors: Jooste S.
Published: May 2018

The use of an objective function based on fuzzy ecological effect expectation in a genetic optimisation algorithm to obtain site or situation specific stressor attenuation values for the management of diverse stressors emanating from several sources is investigated. The approach is based on the premise that both regulator and regulatee are able to formulate their goals in fuzzy terms. In the case of the regulator the goals will be formulated in terms of acceptability of levels of ecological concern (a fuzzy analogy to ecological risk). In the case of the regulatee it will be formulated in terms of acceptability of the level of attenuation, which is also the control variable. A hypothetical catchment is used to illustrate the principle.
Development of an effluent discharge policy for the Tay Estuary based on a finite element model
Authors: Passone S. , Das D. B. , Nassehi V.
Published: May 2018

The tidal hydrodynamics and effluent distribution in estuaries involve a complicated range of solute transport phenomena modelled by partial differential equations. Therefore, the quantitative estimation of the risks of water and soil contamination of coastal areas as a result of polluted estuary flows, or effects of the effluent input on the chemical loads, involves the solution of these equations. Generally, the pollutants load in an estuary is determined by the nature of land use which by altering the watershed hydrology or chemical detention/release in the river banks affect the water quality of the estuaries. The present modelling work aims to investigate the solute transport behaviour in the Tay Estuary in Scotland. Based on this study, an attempt to devise an estuary specific discharge strategy for the Tay has been made. The numerical calculations are based on using 2D Galerkin finite element discretisation of the governing equations in an Eulerian co-ordinate system. The flexibility of the formulation allows it to be extended to moving boundary situations encountered in most tidal water systems.
Use of fuzzy method to estimate river nutrient loads from scarce observation
Authors: Buzás K.
Published: May 2018

Evaluation of data time series in order to get information about water systems is one of the routinely needed tasks. The results are always associated with uncertainties, of which one arises from data scarcity. Traditional methods, such as regression analyses etc. become rapidly useless with decreasing number of data available. A method based on fuzzy set theory was applied to get more reliable information about the system from scarce databases. Monitored daily flow and water quality data of the medium size Zala River in Hungary were considered as elements of fuzzy sets. Fuzzy rules were generated form data pairs (flow, suspended solids concentration, water temperature and phosphorus load as inputs and output, respectively) from which combined rule bases were set up. These rule bases can be considered as a tool of mapping from the input space to the output space using defuzzification procedure. The method is trainable: it can learn from observations. It is demonstrated that the method is capable to generate daily phosphorus loads and annual balance with acceptable accuracy when it is trained only by weekly, biweekly or monthly data pairs. In comparison to other approaches the tool is well suited to utilize better the information content of scarce observations. Furthermore, monitoring costs can be considerably decreased without substantial information loss since sampling of expensive and labour intensive parameters can be reduced.
Integral water quality modelling of catchments
Authors: van Griensven A. , Bauwens W.
Published: May 2018

ESWAT - Extended Soil and Water Assessment Tool - was developed to allow for an integral modelling of the water quantity and quality processes in river basins. The diffuse pollution sources are assessed by considering crop and soil processes and - together with the point sources - further transformed by an in-stream water quality module. An autocalibration procedure allows for the optimisation of the process parameters. The optimisation uses a global optimisation criterion, whereby several objective functions can be considered or combined and whereby several output variables can be taken into account simultaneously. The model and the calibration procedure are applied to the river Dender in Belgium.
Recalcitrance as a catalyst for new developments
Authors: Field J.A.
Published: May 2018

Humic substances are very recalcitrant in anaerobic environments as substrates, mostly due to their non-hydrolyzable high molecular weight structure, which is incompatible for cell uptake. The recalcitrant nature can be applied towards immobilizing pollutants into non-toxic humic substances. Certain anaerobic bioconversions such as demethylation of lignin and reduction of nitro- or azo groups can activate pollutants for humification processes upon subsequent exposure to air. Although humic substances provide no carbon or energy for microorganisms, the evidence presented here indicates that they are very active as terminal electron acceptors and redox mediators promoting the anaerobic degradation and biotransformation of priority pollutants.
Pretreatment of bakery wastewater by coagulation-flocculation and dissolved air flotation
Authors: Liu J. C. , Lien C. S.
Published: May 2018

The pretreatment of wastewater from a large-scale bakery was studied. In the coagulation-flocculation reaction, it was found that both alum and FeCl3 were effective in the jar tests. When at coagulant dosage of 90 to 100 mg/l, 55 % of COD and 95 to 100% of SS could be removed. The optimum pH was at 6.0. In addition, the removal of SS was affected by pH more significantly, while the removal of COD was not affected in the pH range of 6.0 to 8.0. In the DAF experiments, 48.6% of COD and 69.8% of SS were removed in 10 min at a pressure of 4 kg/cm2, recycle ratio of 0.3 l/min, and pH of 6.0. Upon the addition of 100 mg/l of alum, the removal efficiency of COD did not increase while SS removal increased to 82.1%. It was found that 5-min flocculation time did improve the COD removal while it had little effect on SS removal. Flocculation for longer than 5 min did not enhance the flotation performance. Similar phenomena were observed when FeCl3 was used as the coagulant, except that flocculation had an insignificant effect on COD and SS removal. It was also found that FeCl3 was relatively more effective than alum. In summary, both coagulation-flocculation and DAF were efficient for the pretreatment. The advantages and disadvantages were discussed.