bluuebunny/crossref_metadata_2025 huggingface dataset:
UASBs or anaerobic ponds in warm climates? A preliminary answer from Colombia
Authors: Peña M.R. , Rodriguéz J. , Mara D.D. , Sepulveda M.
Published: May 2018

An anaerobic pond and a UASB reactor treating the same domestic sewage under the same environmental conditions were monitored at the wastewater research and technology transfer station in Ginebra, Valle del Cauca region in Colombia. Preliminary results showed removal efficiencies in the UASB of around 66, 78 and 69% for COD, BOD and TSS, respectively. The removal efficiencies in the anaerobic pond for the same parameters were 68, 59 and 73%, respectively. A preliminary cost comparison has shown that construction and operation and maintenance costs of the anaerobic pond are 16 and 38% less than those for the UASB, respectively. Based upon this preliminary study, it would seem that technical features of these two systems (AP and UASBs) in terms of removal efficiencies are not key points to choose one over the other since they perform similarly when treating the same sewage. This is particularly true if both reactors work under optimal conditions. Therefore, a more rational and definite answer to the question – UASBs or anaerobic ponds in warm climates? – must be based on a more rigorous appraisal of social, economic and managerial factors linked to the local context.
Cross-flow ultrafiltration for surface water treatment in North Thailand
Authors: Takizawa S. , Babel S. , Pradhan N. , Prathomrungsiyunkul T. , Suwannarit K. , Yamazaki S.
Published: May 2018

Experimental studies on cross-flow ultrafiltration were carried out to evaluate the applicability to treat surface water in North Thailand. Hollow-fiber UF modules (polyacrylonitrile, MWCO 13,000 daltons, I.D. 0.8 mm, and module length 1126 mm) were used in the experiments. While the permeation flux was controlled at 1.0 m/d, the cross-flow velocity was either fixed at 0.1 m/s or varied as the membrane fouling proceeded. The comparative study on fixed and variable cross-flow velocities revealed that the variable velocity operation was superior to achieve a longer operational period before chemical cleaning. Intensive backwashing was performed when the filtration resistance rose over 1013 m–1, which revealed that more than 80% of the resistance was caused by cake-layer that can be removed by the intensive backwashing. However, the operational period was only 54% of the one for the new membranes, which suggested that the percentage reduction of the filtration resistance should not be used as an index of the efficiency of chemical or physical membrane cleaning. Despite shortened operational periods, the intensive backwashing was proposed to be an easy and rapid method to recover the permeability of fouled membranes without chemical use. The cross-flow UF system used in this study was found to be easy to operate even in small water systems in developing countries.
Flexible design and operation of a two-step UF/NF-system for product recovery from rinsing waters in batch production
Authors: Goers B. , Wozny G.
Published: May 2018

Water and concentrated product solution can be recovered from rinsing waters of the batch production of surfactants and detergents. This investigation is focused on anionic and non-ionic surfactant solutions. Two different membrane processes have been investigated experimentally. For the concentration of the product solution the ultrafiltration is investigated. The ultrafiltration process is modelled on the basis of a gel layer resistance approach. The model is validated using the experimental data. The simulation is used to calculate the optimal design and operation parameters for a multi-stage UF concentration plant. Under economic constraints, an optimal number of feed-and-bleed-stages can be found. For the water purification, a nanofiltration step has to be implemented for some surfactant solutions. Depending on the separation characteristic, CIP-batches are treated with a single (UF) or two-step membrane process (NF/ UF).
Operation of different membrane bioreactors: experimental results and physiological state of the micro-organisms
Authors: Rosenberger S. , Witzig R. , Manz W. , Szewzyk U. , Kraume M.
Published: May 2018

Lab-scale and pilot-scale activated sludge bioreactors with integrated microfiltration membranes were operated over a period of up to three years. During the entire operation period no excess sludge was removed from the bioreactors apart from sampling, resulting in highly concentrated biomass in the reactors. The dry weight of the sludge ranged from 15 to 23 g MLSS l–1 for a plant fed with municipal wastewater and up to 60 g ll–1 for a lab-scale plant fed with high strength molasses. Stable biomass concentrations were reached at F/M ratios as low as approximately 0.07 kg COD (kg MLSS)–1 d–1. The degradation performance of the analyzed reactors was high and stable. Direct microscopical studies revealed high amounts of free suspended cells and at various times also high numbers of filamentous bacteria. Surprisingly only low numbers of protozoa were observed during most of the time. By use of fluorescent in situ hybridization (FISH) only about 40% to 50% of all bacteria emitted probe conferred fluorescence signals sufficient for detection, compared to around 80% cells detectable in conventional activated sludge. Studies on oxygen consumption rates indicated that the biomass in the bioreactor was substrate limited. These data suggest that substrate is mainly oxidized and not used for growth purposes which offers the possibility to operate membrane bioreactors with significantly reduced secondary sludge production.
Membrane fouling and its control in environmental applications
Authors: Fane A.G. , Beatson P. , Li H.
Published: May 2018

Fouling is an issue in the application of membranes to environmental management. This paper describes recent developments in fouling analysis and membrane autopsy. Methods of fouling control are described with examples of feed pretreatment, membrane selection, module design and selection and mode of operation.
Kinetic model for deep waste stabilization ponds operating in batch mode
Authors: Soler A. , Moreno M. D. , Saez J. , Moreno J.
Published: May 2018

A kinetic model has been developed to predict changes with time of different parameters (COD, nitrogen, phosphorus, phytoplankton and alkalinity) in urban wastewater stored in deep (13.5 m) stabilization ponds in southeastern Spain. The effect of thermal stratification on the behaviour of the pond is represented in the model by means of two interconnected reactors, one above the other, representing the hypolimnion and the epilimnion respectively, separated by a moving thermocline. The values predicted by the model closely matched the experimental results.
Potential application of computational fluid dynamics to pond design
Authors: Shilton A.
Published: May 2018

The ability to reliably predict the fluid flow through a pond and relate these hydraulic characteristics to pond treatment performance would clearly be a very valuable tool to the design engineer. The application of computational fluid dynamics (CFD) mathematical modelling has the potential to do this.

In recent years there has been rapid advancement of computing power and mathematical modelling software. CFD simulation gives the pond designer the potential to explore the hydraulic performance for a wide range of design configurations and scenarios. This paper reports on the application of the PHOENICS CFD package for this purpose.

To demonstrate the potential application of CFD to pond design, this paper presents a series of simulations of a small community pond. The simulations undertaken were three-dimensional and incorporated the k-e turbulence model. The first of these modelled the existing pond arrangement, after which the effects of adding a baffle is shown as an example of how CFD can be applied for design.

In addition to the fluid velocity field, plots of a simulated tracer slick were produced. This simulated tracer movement is used to produce hydraulic retention time distribution curves of the tracer concentration at the outlet. These are then integrated with a simple, first-order decay model for BOD removal and faecal coliform die-off to calculate treatment efficiency. This allowed direct comparison of the expected treatment efficiencies with and without the baffle modification.
Three-dimensional computational fluid dynamic modelling of a facultative lagoon
Authors: Salter H. E. , Ta C. T. , Ouki S. K. , Williams S. C.
Published: May 2018

A series of facultative lagoons operated by Thames Water treating industrial wastewater in Thailand were found to be performing poorly, particularly with respect to the removal of biological oxygen demand (BOD). A review of the design parameters for the site found that all the lagoons are of a sufficient area for the flow and BOD load. However, observations of the lagoons suggested that there may be significant hydraulic short-circuiting. Computational fluid dynamics (CFD) modelling was therefore carried out on one of the lagoons to establish the hydraulic regime. Two consecutive simulations were carried out, both with and without baffles; the first to establish steady flow conditions, and the second using a chemical species transport model to obtain the residence time distribution (RTD). The results of the modelling indicate that the lagoons do currently suffer from significant short-circuiting, and large dead-zones are present. The installation of baffles in the CFD model improved the plug-flow characteristics of the lagoons, substantially reducing the short-circuiting and the size of the dead-zones. It has therefore been concluded that the installation of baffles in the lagoons will lead to an improvement in their performance, by increasing the retention time of the system.
Influence of organic loading rate on membrane fouling in membrane separation activated sludge process
Authors: Nagaoka N. , Kono S. , Yamanishi S. , Miya A.
Published: May 2018

A Laboratory-scale experiment was conducted to investigate the influence of organic loading rate to a reactor on the bio fouling in a membrane separation activated sludge system. A flat-sheet-type membrane module was used and the change of the pressure and the filtration resistance were measured. Using synthetic substrate, TOC loading rate was set in the range between 0.3 g l–1 day–1 and 1.5g l–1 day–1. Also an experiment on the consolidation characteristics of sludge accumulated on membrane was conducted. A mathematical model was developed to simulate temporal changes of suction pressure, flux and filtration resistance considering accumulation, detachment and consolidation of bacterial extracellular polymers on the membrane surface. A reactor with higher loading rate showed sudden increase of trans-membrane pressure, while a reactor with lower loading rate showed delayed increase of the pressure. The experimental results were simulated well by the developed model.
Approaches to membrane fouling control in anaerobic membrane bioreactors
Authors: Choo K-H. , Kang I-J. , Yoon S-H. , Park H. , Kim J-H. , Adiya S. , Lee C-H.
Published: May 2018

Various fouling control methods were investigated for polymeric and ceramic microfiltration membranes in the anaerobic membrane bioreactors where inorganic precipitates and/or fine colloids have been recently known as the most significant foulants: (i) Substantial improvement of flux was achieved by backfeeding of acidic wastewater through the membrane module. The backfeeding mode formed an acidic environment around the membrane pores and thus suppressed struvite formation. (ii) Struvite precipitation was also mitigated when an additional combined dialysis/zeolite unit was attached to the bioreactor. With this combined unit the flux improvement for the ceramic membrane, where struvite had a severer fouling effect, was achieved more significantly than that for the polymeric membrane. (iii) To control the deposition of organics and fine colloids onto the polymeric membrane, powdered activated carbon (PAC) was added into the bioreactor, which gave rise to the reduction of specific cake resistances of biosolids through the sorption and/or coagulation of dissolved and colloidal matter. (iv) The hydrophilic modification of polypropylene (PP) membranes by graft polymerization reduced membrane fouling. Its effectiveness was most substantial at 70% of the degree of grafting, indicating that there was an optimal degree of grafting. This is possibly due to the steric hindrance of grafted polymer chains and the increase in the hydrophilicity of the grafted PP membrane.
New perspectives in anaerobic digestion
Authors: van Lier J. B. , Tilche A. , Ahring B. K. , Macarie H. , Moletta R. , Dohanyos M. , Hulshoff Pol L. W. , Lens P. , Verstraete W.
Published: May 2018

The IWA specialised group on anaerobic digestion (AD) is one of the oldest working groups of the former IAWQ organisation. Despite the fact that anaerobic technology dates back more than 100 years, the technology is still under development, adapting novel treatment systems to the modern requirements. In fact, most advances were achieved during the last three decades, when high-rate reactor systems were developed and a profound insight was obtained in the microbiology of the anaerobic communities. This insight led to a better understanding of anaerobic treatment and, subsequently, to a broader application potential.

The present “state-of-the-art” paper, which has been written by members of the AD management committee, reflects the latest achievements and sets future lines for further development.
Rapid-rate thermophilic, single-stage and two-phase methane fermentation of synfuel-industry wastewaters
Authors: Ghosh S. , Jerger D. , Henry M. P. , Sajjad A.
Published: May 2018

Thermophilic (55°C) anaerobic digestion of wastewaters from wet carbonization of Minnesota peat was conducted in a simple, upflow digester at an HRT of one day to provide a methane yield of 0.20 SCM/kg VS added and a BOD5 reduction of 85%. Carbonization of Maine peat conducted for a much longer duration of thermal treatment produced recalcitrant and potentially toxic end products that reduced the biodegradability of wastewaters. Methane fermentation of the Maine-peat wet-carbonization waste was inhibited at an HRT of one day in the single-stage digester. However, two-phase digestion with separate acid-phase fermentation to promote hydrolytic degradation of toxic end products followed by separate methane fermentation at an HRT of 2 days exhibited a methane yield of 0.21 SCM/kg VS added and a BOD5 reduction of 76%. Volatile fatty acids profiles along the depths digesting cultures indicated that single-stage and two-phase digestion could be accomplished at one-half the reactor residence times (one day for single-stage and three days for two-phase) used in this research.
Comparison of enumeration methods for ammonia-oxidizing bacteria
Authors: Konuma S. , Satoh H. , Mino T. , Matsuo T.
Published: May 2018

MPN, antibody, fluorescent in situ hybridization (FISH) and dot blot hybridization methods for enumeration of ammonia-oxidizing bacteria were applied to various samples from suspended systems. As for FISH, reoptimization of an oligonucleotide probe Nso190 was attempted. The advantages and disadvantages of these methods were discussed. MPN appeared to have disadvantages of underestimation. Dot blot hybridization had lower detection limit and higher reliability than other methods. It could be applied to mixed liquors and effluents of municipal wastewater treatment plant (WWTPs), lab-scale reactor and enrichment cultures of ammonia-oxidizing bacteria. FISH could be successfully applied to high ammonium loading system such as enrichment cultures, but weak signal, auto-fluorescence and non-specific binding could cause problems when applied to low ammonium loading systems such as effluents of WWTPs and river water. Mixed liquor of municipal WWTP seemed to be a critical case for FISH.
Comparison of different operational modes of a two-stage activated sludge pilot plant for the extension of the Vienna STP
Authors: Müller-Rechberger H. , Wandl G. , Winkler S. , Svardal K. , Matsché N.
Published: May 2018

A pilot plant has been operated over a period of two years in order to investigate the performance and the operating characteristics of the plant concept developed for the extension of the main Vienna STP and to develop a simulation model which will be applied for operation support of the full stage plant. The pilot plant is a two stage activated sludge plant, each stage comprising of four aeration tanks and a clarifier tank. The pilot plant layout allows three different operational modes, each of which has been operated for several periods. The performance of the pilot plant during these periods is described and the different operational modes are compared to each other.
Microbial storage products, biomass density, and settling properties of enhanced biological phosphorus removal activated sludge
Authors: Schuler A. J. , Jenkins D. , Ronen P.
Published: May 2018

The relationships between bacterial storage products, density, and settling characteristics were determined in a laboratory-scale sequencing batch reactor (SBR) enhanced biological phosphorus removal (EBPR) system. Both long-term and single anaerobic-aerobic cycle variations in these properties were studied. Increased polyphosphate (PP) content of the biomass during long-term operation resulted in improved sludge volume index (SVI) values. End-aerobic phase (after phosphate (P) uptake) values were consistently lower than end-anaerobic phase (after P release) values. Neither filamentous nor slime bulking were evident by microscopic observations. Biomass density increased at a rate of 1.2 mg/L per each 1% increase in biomass P content. End-aerobic phase samples had an average 25% higher buoyant density than end-anaerobic phase samples, which was attributed to aerobic P uptake. Biomass density was negatively correlated with SVI values, and SVI values increased sharply at low biomass density. A mathematical model developed by Mas et al. (1985) was modified to predict total cell density based on literature values of PP, glycogen (GLY), and poly-b-hydroxybutyrate (PHB) densities. Model predictions were in good agreement with experimental results, although improved measurement of PP density is required to improve model predictions.
Evaluation of nitrification-inhibition measurements
Authors: Jönsson K. , Aspichueta E. , de la Sota A. , la C Jansen J.
Published: May 2018

A screening method for nitrification-inhibition determination has been evaluated at two laboratories, one in Sweden and one in Spain. Allylthiourea (ATU), methanol, chromium and zinc were used as reference toxicants in combination with different kinds of full-scale sludge and sludge produced in the laboratory. Different results were obtained with different combinations of activated sludge and toxicants. It was found that activated sludge often exposed to small amounts of a variety of toxic substances may build up a general resistance to toxic substances. Specific adaptation to certain substances was also observed. Domestic activated sludge responded in the same way to ATU regardless of whether it originated from Sweden or Spain. Synthetic sludge and domestic sludge exhibited the same inhibition of nitrification when tested with ATU as a toxicant. Synthetic activated sludge from two laboratory-scale plants run in parallel did not exhibit exactly the same sensitivity to certain toxicants. The variation in repeated tests with the synthetic sludges was about the same as for repeated tests with full-scale sludge and for other biological toxicity tests. Limits of detection were calculated to be about 5% for a single sample with three blanks as references at both the laboratories.
The reactivity of natural organic matter to disinfection by-products formation and its relation to specific ultraviolet absorbance
Authors: Kitis M. , Karanfil T. , Kilduff J. E. , Wigton A.
Published: May 2018

Five natural waters with a broad range of DOC concentrations were fractionated using various coal- and wood-based granular activated carbons (GAC) and alum coagulation. Adsorption and alum coagulation fractionated NOM solutions by preferentially removing components having high specific ultraviolet absorbance (SUVA). UV absorbing fractions of NOM were found to be the major contributors to DBP formation. SUVA appears to be an accurate predictor of reactivity with chlorine in terms of DBP yield; however, it was also found that low-SUVA components of NOM have higher bromine incorporation. SUVA has promise as a parameter for on-line monitoring and control of DBP formation in practical applications; however, the effects of bromide concentration may also need to be considered. Understanding how reactivity is correlated to SUVA may allow utilities to optimize the degree of treatment required to comply with DBP regulations. The reactive components that require removal, and the degree of treatment necessary to accomplish this removal, may be directly obtained from the relationship between SUVA removal and the degree of treatment (e.g., alum dose).
Changes in the organic composition of wastewater during biological treatment as studied by NMR and IR spectroscopies
Authors: Dignac M.-F. , Ginestel P. , Bruchet A. , Audic J.-M. , Derenne S. , Largeau C.
Published: May 2018

Despite its importance, relatively little is known about the composition and fate of wastewater organic matter (OM) in treatment plants. Monitoring the chemical changes in OM during activated sludge treatment can improve our knowledge of the processes involved in the biological elimination of OM. Direct chemical analyses of treated water OM typically account for about 20% of the OM, and structural information was obtained in this study using Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) spectroscopic techniques. Distinct changes in the OM during wastewater biological treatment were underlined. 13C and 1H NMR showed that aromatic carbons were minor constituents of the samples. Alkyl chains exhibited a more highly branched character in treated water, as compared to long chain aliphatic carbons present in wastewater. Carboxyl signals in the 13C NMR spectrum of wastewater could be due to peptide bonds in proteins, whereas in the treated water spectrum, this signal could be related to the presence of non-proteinaceous nitrogen. Besides the non-degraded compounds, treated water OM could contain recondensation products of simple molecules. Their refractory character probably derives from their complex structures rather than from particular chemical functions, as suggested by the lack of fundamental differences in the chemical structures of wastewater and treated water OM.
Detection of estrogenic activity in Flemish surface waters using an in vitro recombinant assay with yeast cells
Authors: Witters H. E. , Vangenechten C. , Berckmans P.
Published: May 2018

Numerous environmental chemicals possess estrogen-like properties. At elevated doses, natural estrogens and environmental estrogen-like chemicals are known to produce adverse effects on humans and wildlife. Sources of potential exposure to endocrine disrupting compounds have to be identified for risk and hazard assessment. Extracts prepared from 16 selected water samples taken in Flemish rivers, effluents of municipal wastewater treatment plants and reservoirs for drinking water production were analysed for estrogenic activity with a cellular bioassay. Yeast cells, which are stably transfected with the DNA sequence of hER and which contain expression plasmids with the reporter gene lac-Z, encoding the enzyme b-galactosidase, were used to measure receptor binding. Flemish rivers showed the highest estrogenic potency, compared to effluents of waste water treatment plants and reservoirs which showed low induction factors (β-galactosidase production) relative to solvent control conditions. By comparison with a standard curve for 17β-estradiol (E2), estrogenic potency in water samples was calculated as E2-equivalents and ranged from below detection limit (˜ 2.75 ng E2/l) up to 81.4 ng/l E2-equivalents. About 7 water samples had more than 10 ng/l E2-equivalents. These elevated levels of E2-equivalents are likely to exert significant adverse effects on reproduction success of wildlife, which should be verified with in vivo studies.
Monitoring and classification of toxicity using recombinant bioluminescent bacteria
Authors: Gu M. B. , Choi S. H.
Published: May 2018

Recombinant bioluminescent biosensing cells were used to detect and classify toxicity caused by various chemicals in water environments. Classification of the toxicity was realized based upon the chemicals' actions of toxicity by using DNA-, oxidative- and membrane-damage sensitive strains. Tested samples contained a single chemical or mixture of chemicals in media, wastewater, or river water. Finally, it is suggested that this method for classification of toxic chemicals in wastewater or other aqueous systems may be adopted for primary screening steps of the samples and can give useful information about the samples' characteristics.
Partial oxidation of reactive dyestuffs and synthetic textile dye-bath by the O3 and O3/H2O2 processes
Authors: Balcioğlu I. A. , Arslan İ.
Published: May 2018

Ozonation and O3/H2O2 oxidation of reactive dyestuffs and simulated textile dye-bath were investigated. Effects of reaction pH, initial dye concentration, H2O2 concentration and assisting chemicals on treatment efficiency were examined. We found considerable improvement in COD and colour removal rates at pH=11, that was almost the actual pH of the prepared textile wastewater, whereas in particular increasing the initial dyestuff concentration had an adverse effect upon oxidation rates. Removal of colour, COD and TOC were found to be fairly sensitive to the introduction of soda that is frequently applied as an auxiliary chemical during the reactive dyeing process. The addition of H2O2 had negligible effect on COD removal efficiency and decolorization rate compared to ozonation alone at different pH values. Accordingly it can be inferred that the theoretically expected effect of OH· radical scavengers (e.g. carbonate, chloride) present in the synthetic dye-bath as well as introduced radical formationpromoters (e.g. H2O22, OH–) were probably hidden due to the complexity of the synthetic wastewater matrix. Biodegradability of the ozonated dye-bath was accelerated by a factor of three corresponding to a 233% relative enhancement. The inhibition of the oxygen uptake rate decreased from 91% to 75% within only 5 min treatment time.
Biotreatability studies of pharmaceutical wastewater using an anaerobic suspended film contact reactor
Authors: Venkata Mohan S. , Prakasham R. S. , Satyavathi B. , Annapurna J. , Ramakrishna S. V.
Published: May 2018

The pharmaceutical industrial effluents, which include several organic solvents and other toxic chemicals, are generally treated by aerobic process, which is cost intensive in nature. The alternative anaerobic route to degrade the toxic effluents is attractive due to the lower cost of treatment and the generation of gas, which can supplement the energy requirements. There are few reports on the anaerobic treatment of the pharmaceutical effluents. In the present investigation, the effluents from a bulk drug industry, which utilizes several organic chemicals, have been taken to assess their applicability for anaerobic treatment. The organic loading rates were varied from 0.25 kg/m3/day to 2.5 kg/m3/day and the COD reduction was found to be in the range of 60 to 80%. Long term operation of an anaerobic suspended film contact reactor carried out with 1.25 kg/m3/day was found to be optimum. The biogas generated during the degradation process was monitored and the methane content was found to be 60–70%.
Photocatalytic degradation of azo dye in TiO2 suspended solution
Authors: Hung C.-H. , Chiang P.-C. , Yuan C. , Chou C.-Y.
Published: May 2018

The photocatalysis of azo dye, Orange G, by P-25 anatase TiO2 was investigated in this research. The experiments were conducted in a batch reactor with TiO2 powder suspension. Four near-UV lamps were used as the light source. The experimental variables included solution pH level, amount of TiO2, illumination light intensity, and reaction time. A pseudo-first order reaction kinetic was proposed to simulate the photocatalytic degradation of Orange G in the batch reactor. More than 80% of 10 mg/L Orange G decomposition in 60-minute reaction time was observed in this study and fast decomposition of Orange G only occurred in the presence of both TiO2 and suitable light energy. Faster degradation of Orange G was achieved under acid conditions. The degradation rates of Orange G at pH = 3.0 were about two times faster than those at pH = 7.0. Faster degradation of azo dye was observed for greater irradiated light intensity and more TiO present during the reaction. The reaction rates were proportional to TiO2concentration and light intensity with the power order of 0.726 and 0.734, respectively.
Performance of an SBR-plant for advanced nutrient removal, using septic sludge as a carbon source
Authors: Morling S.
Published: May 2018

The Tjustvik SBR-plant outside Stockholm, Sweden has been in operation for four years. The plant has to meet stringent effluent standards, BOD7<10 PPM, total N < 15 PPM and total P < 0.3 PPM. The plant is a typical two reactor SBR-plant, sized for about 15 000 inhabitants. During the first year of operation there were difficulties in meeting the P consent level. The difficulties were linked to a deficit of available organic carbon and a secondary phosphorus release. The problem was solved with the addition of septic sludge, in an amount equivalent to about 10,000 to 15,000 inhabitants with respect to the BOD-load.

The altered operation resulted in a very stable and good effluent quality from the plant that has been maintained ever since, giving typical discharge levels as follows: BOD7, < 3 mg/l; Total-P, < 0.15 mg/l; Total-N, < 7 mg/l; NH4-N, < 1 mg/l.

The change of process saved the community from a major investment in a separate treatment facility for the septic sludge. The stabilisation degree of the waste activated sludge is sufficient to by pass the anaerobic digestion for the time being. In the beginning, the SBR-process stability played an unwanted role during start up as it maintained a secondary phosphorus release for a considerable time. Later the process stability became an asset as the varying loads from the septic sludge addition were handled with very good results.
Effects of fill modes on N2O emission from the SBR treating domestic wastewater
Authors: Park K. Y. , Lee J. W. , Inamori Y. , Mizuochi M. , Ahn K. H.
Published: May 2018

Nitrous oxide (N2O) gas is emitted as an intermediate in the biological nitrogen removal process. A track study was performed to investigate the characteristics of N2O emission depending on the cyclic mode of a sequencing batch reactor (SBR). A major emission of N2O took place at the aerobic phase, while N2O emission at the anoxic phase was insignificant. Especially, the highest N2O emission rate was observed at the initial stage of aerobic phase under the limited dissolved oxygen (DO) condition. Under such a condition, nitrite (NO2-) was transiently accumulated along with significant N2O emission due to incomplete nitrification. In addition, N2O production at the aerobic phase was strongly related with incomplete denitrification by nitrifiers. N2O emission could be reduced by change in fill modes in the SBR. A significant conversion to N2O took place in the SBR with the anoxic fill mode, while only small amount of N2O was conversed in the SBR with the aerobic fill mode. Relatively high concentration of ammonia nitrogen (NH4+) accelerated N2O production at the aerobic phase in the SBR with the anoxic fill compared to the aerobic fill. For control of N2O emission in the SBR, the aerobic fill mode could be an effective method even if denitrification efficiency may be reduced at the anoxic phase.
An enhanced biological phosphorus removal (EBPR) control strategy for sequencing batch reactors (SBRs)
Authors: Dassanayake C. Y. , Irvine R. L.
Published: May 2018

A control strategy was developed for enhanced biological phosphorus removal (EBPR) in a Sequencing Batch Reactor (SBR). Unlike past research that focused on maximizing polyhdroxyalkanoate (PHA) formation during the anaerobic period, this study investigated some of the factors that govern aerobic PHA dynamics and its efficient regulation during phosphate (P) uptake. Influent COD, influent P, and the time for aeration were critical factors that governed PHA use and P uptake during aerated react. Unnecessary PHA oxidation (i.e., in the absence of extracellular P) occurred if the time for aerated react exceeded the time required for P uptake. By adjusting the aeration time to that required for P uptake, residual PHA was sustained in the SBR and excess phosphate uptake reaction potential (PRP) was generated for use during transient influent excursions in P. Unlike space oriented systems, the time for react is simply adjusted in the SBR. Because residual PHA is easily maintained once achieved, high influent COD events can be harnessed to increase or sustain excess PRP for management of expected variations in influent P.
Sequencing batch reactor with submerged hollow fibre membranes for the biomass separation
Authors: Krampe J. , Krauth K.
Published: May 2018

A method to reduce the cycle time of the SBR-process by utilising submerged membranes is described. The time necessary for the sedimentation of the activated sludge and the extraction of the clear-water phase takes up a major part of the entire cycle period within the SBR-process. By using membranes it is possible to start the clear-water extraction already during the reaction time. The time needed for the sedimentation of the activated sludge can be dispensed with altogether. The paper presents the initial results of a semi-technical test plant, with particular emphasis on the fact that the running of the SBR-plant did not lead to any problems with fouling or scaling. In cases of high solids contents, the oxygen input was below par; this, however, did not have any unfavourable impact on the nitrification.
How water scarcity will shape the new century
Authors: Brown Lester R.
Published: May 2018

Water resources are increasingly being overexploited, such that current food production, which relies heavily on irrigation schemes, is unsustainable. Many steps, including improved irrigation techniques, more water-efficient crops and animal protein production, etc., will be needed to raise water productivity across the board. Water must in future be recognised as a scarce resource and not taken for granted.
Water is a catalyst for peace
Authors: Asmal Kader
Published: May 2018

Despite much recent rhetoric predicting growing conflict, even wars, over water, the weight of historical evidence points overwhelmingly to peaceful resolution of such conflicts. Water in fact tends to act as a catalyst for cooperation.
Green water security for the food makers of tomorrow: windows of opportunity in drought-prone savannahs
Authors: Rockström Johan
Published: May 2018

The largest remaining biophysical water challenge is whether there is enough fresh water to sustain global food production and service natural ecosytems. Focussing on the drought-prone savannahs and small-scale farming, this paper argues that the crucial resource is vapour flow, not 'blue' water, and there are grounds for optimism if resource management can be improved.
Thermophilic anaerobic digestion of methanol in UASB reactor
Authors: Paulo P. L. , Jiang B. , Rebac S. , Hulshoff Pol L. , Lettinga G.
Published: May 2018

A 5.1 L laboratory scale upflow anaerobic sludge bed (UASB) reactor was operated at 55°C over 130 days in order to investigate the feasibility of treating methanol-containing wastewater under thermophilic conditions, focussing on start-up and process stability. Batch assays were conducted to elucidate the most probable pathway for methanol conversion. The results demonstrated a good performance, with a chemical oxygen demand (COD) removal averaging 82% throughout the experiment. No significant VFA accumulation was detected in the effluent, even with bicarbonate concentration exceeding 20 mM. Acetate was the main component of the VFA at relatively low organic loading rates (OLR). At high OLR, the main components were propionate and butyrate. Reactor performance was hardly affected when the system was exposed to non-optimal conditions, i.e., temperature drop, overloading and no feeding. Good thermophilic granular sludge was retained in the reactor. Washout of biomass was not severe during the experiment. From the pathway analysis it could be concluded that indirect pathways play an important role in the methanol degradation by the cultivated consortia.
Workshop 5 (synthesis): feminization of water security
Authors: Morgan James , Falkenmark Malin
Published: May 2018

Water management can be greatly improved if the capacities, skills and perspectives of women are promoted
Feminization as a critical component of the changing hydrosocial contract
Authors: Turton A. R. , Schreiner B. , Leestemaker J.
Published: May 2018

The Dublin Principles recognize the role that women play in water resources management. The South African Minister of Water Affairs, Prof. Kader Asmal, coined a new expression by referring to the “feminization of water”. The article explores some of the ramifications of this and shows that the two aspects are not necessarily the same thing. Feminization does not necessarily mean bringing more women into management processes as it is often depicted. This is the quantitative aspect that is often referred to by male managers and it has been given a negative implication as a result. The more important issue is the qualitative aspect that involves processes such as stakeholder participation, viewing alternatives before a decision is made and accountability.
Biodegradation of disperse blue 79 using sequenced anaerobic/aerobic biofilters
Authors: Cruz A. , Buitrón G.
Published: May 2018

A sequential anaerobic/aerobic treatment process was used to biodegrade the azo dye disperse blue 79 (DB79). The integrated process was successfully tested and operated for the mineralization of the DB79 dye until a concentration of 120 mg/l in 96 h. In the first stage, the anaerobic biofilter biotransformed the DB79 to amines with efficiencies of decolorization higher than 95% in 72 h. The amines produced in the first stage were degraded in the aerobic biofilter with efficiencies of 65% in 24 h. It was observed that the use of a co-substrate on the anaerobic biofilter influenced the performance of the bioreactor only when the concentration of the DB79 was higher than 48 mg/l. It was found that the residual dye in the effluent of the anaerobic stage inhibits the performance of the aerobic microorganisms.
Post-treatment of anaerobic effluents in an overland flow system
Authors: Chernicharo C. A.L. , da Silva Cota R. , Zerbini A.M. , von Sperling M. , Novy de Castro Brito L.H.
Published: May 2018

This research aimed at the investigation of an overland flow system applied to the post-treatment of anaerobic effluents. The system treated domestic sewage in Itabira City (Brazil), being composed by an anaerobic reactor and an overland flow system, the latter working as a post-treatment unit. A portion of the reactor's effluent was directed to a group of three overland flow slopes (demonstration scale), that were operated with different application rates. During Phase 1 of the research, the overland flow system was fed under a permanent hydraulic regime (constant flows), having as inflow the effluent from an UASB reactor (full-scale, volume of 477 m3). During Phase 2, the overland system was fed under a hydraulic transient pattern (variable flows with hourly variations), having as inflow the effluent from a partitioned UASB reactor (demonstration-scale, volume of 9 m3). In general, the performance of the overland flow system as a polishing step was very good, mainly because of the low solids and organic matter concentration in the final effluent (average values of BOD from 48 to 62 mg/L; COD from 98 to 119 mg/L and SS from 17 to 57 mg/L). Regarding nutrients and coliforms, the system also reached satisfactory efficiency levels. Based on the experience obtained with this study, it is suggested that overland flow systems, working as post-treatment step of UASB reactors, can work with application rates in the range of 0.4 to 0.5 m3/m.h, which are higher than those normally applied.
Nitrification-denitrification of UASB effluents highly loaded with nitrogen in an activated sludge reactor operated with short cycled aeration
Authors: Villaverde S. , Lacalle M. L. , García-Encina P. A. , Fdz-Polanco F.
Published: May 2018

A conventional activated sludge reactor operated with short cycled aeration was used for total nitrogen removal of UASB anaerobic reactor effluent containing nitrogen (up to 1,200 mg NKT/L) and organic matter (up to 2,000 mg COD/L). Initially the reactor was fed with synthetic water to progressively introduce the UASB effluent. This favored the acclimation of the microorganisms to the real environment. The results obtained throughout this study showed that initially the tested technology is feasible and can report significant cuts on operation and maintenance when compared to conventional activated sludge processes. Total nitrogen removal up to 66% was attained treating the effluent of an UASB process designed for treating the wastewater of a potato starch factory. Total nitrogen removal capacities ranging between 0.1 and 0.58 kg of nitrogen per cubic metre per day are reported. Short-cycled aeration allowed for a more efficient use of the oxygen supply for nitrification and the organic carbon content present in the wastewater for denitrification.

This operating protocol has demonstrated serious advantages in terms of operation costs and simplicity when total nitrogen removal is wanted. Most of the existing activated sludge processes, i.e. single continuous flow reactors, can be updated for total nitrogen removal essentially at no cost, the inversion (aeration control system) is rapidly returned as reduction in energy expenditure.
Application of an innovative methodology to improve the starting-up of UASB reactors treating domestic sewage
Authors: Rodríguez J. A. , Peña M. R. , Manzi V.
Published: May 2018

This study shows the results obtained during the starting-up evaluation of an UASB reactor treating domestic sewage. It is located in the municipality of Ginebra, Valle del Cauca region in Colombia. Its design flow is 7.5 l/s with a maximum capacity of 10 l/s. The reactor was seeded with a deficient quality inoculum which accounted for 20% of the total reactor volume. The starting-up methodology comprised the sequential washing of the sludge (inoculum) by applying three different upflow velocities. This procedure resembles what other authors term the “selective pressure method”. Once the sludge was washed, the reactor was started-up with an initial hydraulic retention time (HRT) of 24.9 hours, which was steadily reduced down to 6.7 hours in the final stage. Along the starting-up phase, there was a positive evolution in terms of quantity, quality and spatial distribution of the sludge. Consequently, there was a positive evolution in organic matter removal mechanisms. For HRT above 14 hours, the removal mechanisms were mainly physical whilst for HRT below 9 hours the removal mechanisms were mostly biological. Based on the above considerations and on the water quality parameters measured, it may be concluded that the start-up of an UASB reactor for domestic sewage treatment seeded with a low quality inoculum can be done with HRT as low as 15 or 12 hours. In this way, it is possible to reduce the starting-up period of these reactors down to 4 to 6 weeks, provided that the starting-up methodology is properly applied.
Kinetics of ozone reactions with 1-naphthalene, 1,5-naphthalene and 3-nitrobenzene sulphonic acids in aqueous solutions
Authors: Calderara V. , Jekel M. , Zaror C.
Published: May 2018

This paper describes the ozone oxidation kinetics of 1-naphthalene (1NS), 1,5-naphthalene (1,5NDS), and 3-nitrobenzene (3NBS) sulphonic acid. The presence of hydroxyl radicals and their effect on the overall rate of reaction was studied. Second order kinetic constants of direct reactions were estimated at around 252 M-1s-1, 41 M-1s-1 and 22 M-1s-1, for 1NS, 1,5NDS, and 3NBS sulphonic acids, respectively. At pH 3, the indirect reaction accounted for 2%, 15% and 4% of total primary oxidation of 1NS, 1,5NBS, and 3NBS sulphonic acids, respectively. At pH 9, indirect reaction contribution increased to 73%, 84% and 48%, respectively. C4 compounds (maleic and fumaric acids), C2 (oxalic), C1 (formic) and sulphate were identified as oxidation by-products in all cases. TOC slowly decreased throughout ozonation, reaching around 40-60% and 60-70% reduction over 90 minutes at pH 7 and 3, respectively.
River Water Quality Model no. 1 (RWQM1): II. Biochemical process equations
Authors: Reichert P. , Borchardt D. , Henze M. , Rauch W. , Shanahan P. , Somlyódy L. , Vanrolleghem P.
Published: May 2018

In this paper, biochemical process equations are presented as a basis for water quality modelling in rivers under aerobic and anoxic conditions. These equations are not new, but they summarise parts of the development over the past 75 years. The primary goals of the presentation are to stimulate communication among modellers and field-oriented researchers of river water quality and of wastewater treatment, to facilitate practical application of river water quality modelling, and to encourage the use of elemental mass balances for the derivation of stoichiometric coefficients of biochemical transformation processes. This paper is part of a series of three papers. In the first paper, the general modelling approach is described; in the present paper, the biochemical process equations of a complex model are presented; and in the third paper, recommendations are given for the selection of a reasonable submodel for a specific application.
Water decolorization using UV radiation and hydrogen peroxide: A kinetic study
Authors: Martín C.A. , Alfano O.M. , Cassano A.E.
Published: May 2018

Sometimes, provision of water for domiciliary consumption faces the problem of natural contamination originated by the presence of organic substances such as humic or fulvic acids. Very often, after conventional sanitary treatments this water exhibits a persistent yellowish coloration that affects its use. Moreover, these substances may act as precursors of tri-halomethanes formation during pre-desinfection with chlorine. This paper presents, with a simplified mechanistic approach, the intrinsic reaction kinetics of natural water decolorization employing UV radiation and hydrogen peroxide. The main variables for the model are: contaminant concentration expressed as TOC, hydrogen peroxide concentration and the photon absorption rate.
Sulfide production and wastewater quality – investigations in a pilot plant pressure sewer
Authors: Tanaka N. , Hvitved-Jacobsen T.
Published: May 2018

The relationship linking sulfide production rate and wastewater quality in terms of its biodegradability was studied using a pilot plant pressure sewer (inner diameter: 102 mm, length: 47 m). Furthermore, anaerobic transformations of wastewater organic matter were investigated. Wastewater characterization based on oxygen utilization rate (OUR) measurements and VFA analyses was employed. As wastewater quality parameters essential for the sulfide production, COD components and dissolved carbohydrate were focused on. Readily biodegradable substrate and fermentable, readily biodegradable substrate were better parameters than traditional dissolved COD for the prediction of sulfide production rates in a pressure sewer. From the results obtained, it was possible to integrate the sulfide production process with the transformation processes of wastewater organic matter in pressure sewers.