bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature effects on flocculation, using different coagulants
Authors: Fitzpatrick C.S.B. , Fradin E. , Gregory J.
Published: May 2018

Temperature is known to affect flocculation and filter performance. Jar tests have been conducted in the laboratory, using a photometric dispersion analyser (PDA) to assess the effects of temperature on floc formation, breakage and reformation. Alum, ferric sulphate and three polyaluminium chloride (PACl) coagulants have been investigated for temperatures ranging between 6 and 29°C for a suspension of kaolin clay in London tap water. Results confirm that floc formation is slower at lower temperatures for all coagulants. A commercial PACl product, PAX XL 19, produces the largest flocs for all temperatures; and alum the smallest. Increasing the shear rate results in floc breakage in all cases and the flocs never reform to their original size. This effect is most notable for temperatures around 15°C. Breakage, in terms of floc size reduction, is greater for higher temperatures, suggesting a weaker floc. Recovery after increased shear is greater at lower temperatures implying that floc break-up is more reversible for lower temperatures.
Deciphering the science behind electrocoagulation remove suspended clay particles from water
Authors: Holt P.K. , Barton G.W. , Mitchell C.A.
Published: May 2018

Electrocoagulation removes pollutant material from water by a combination of coagulant delivered from a sacrificial aluminium anode and hydrogen bubbles evolved at an inert cathode. Rates of clay particle flotation and settling were experimentally determined in a 7 L batch reactor over a range of currents (0.25-2.0 A) and pollutant loadings (0.1-1.7 g/L). Sedimentation and flotation are the dominant removal mechanism at low and high currents, respectively. This shift in separation mode can be explained by analysing the reactor in terms of a published dissolved air flotation model.
Fundamental characteristics of bubbles and ramifications for the flotation process
Authors: Dockko S. , Han M.Y.
Published: May 2018

Flotation processes involve the use of very small bubbles (micro-bubbles) to separate particles from water. The process has become a good alternative to sedimentation, especially where the particles are small or of low density. Although the flotation process commences with a collision between particles and bubbles, most research has been focused only on the characteristics of the particles. In this paper, recent theoretical and experimental research on the characteristics of bubbles is summarized. The effect on the collision efficiency of the size and charge of bubbles is calculated through trajectory analysis. The size and charge of bubbles are measured under different conditions and the ramifications of the results are discussed. The results may lead to a better understanding and optimization of the existing process. In particular, we discuss an idea that a new advanced flotation process might be possible by the modification of the characteristics of the bubble alone or of both bubble and particle.
A CFD study of the deep bed filtration mechanism for submicron/nano-particle suspension
Authors: Tung K.L. , Chang Y.L. , Lai J.Y. , Chang C.H. , Chuang C.J.
Published: May 2018

The mechanism of the deep bed filtration for submicron and nano particles suspension was conducted by means of a force analysis on the suspended particles flow path through order-packed granular filter beds. The flow fields through the filter beds were calculated by using the commercial available CFD software - Fluent. Various types of granular packing structures, such as the simple cubic packing, bodycentered packing and face-centered packing structures were chosen for analysis. The motion of suspended particle of 2.967, 0.816, 0.460 and 0.050 μm in diameter, respectively, were tracked by considering the following forces including a net gravitational force, hydraulic drag force, lift force, Brownian force, van der Waals force and a double layer force. The effects of the granular bed packing structure, the porosity of these beds and the suspended particle diameter on the capture efficiency of a granular filter bed were examined. The force analysis depicts that the inertial effect and van der Waals force increased the capture probability of particles on the granular filter bed while the lift force and the Brownian force decreased the particle deposition. Simulated results show that among the chosen packing structures, the face-center packed granular bed gives the greatest pressure drop and capture efficiency of particles due to the lower packing porosity. The simple cubic packed filter bed showed the lowest pressure drop and capture efficiency of particles due to the greatest packing porosity among the chosen packing structures. It is mainly due to the simple cubic packing structure in which there exists the free vertical downward flowing path and thus exhibits a higher packing porosity. The comparisons of the simulated capture efficiency with experimental results depicted that the body-centre packed granular bed showed the best approximation of capture efficiency compared to that of the randomly packed granular bed.
Nitrification of high-strength ammonium wastewater by a fluidized-bed reactor
Authors: Botrous A.E.F. , Dahab M.F. , Mihaltz P.
Published: May 2018

A laboratory-scale fluidized-bed reactor with an external aeration loop was used for nitrification of high-strength ammonium wastewater (up to 500 mg NH4-N/L). The results demonstrated that the system is capable of handling ammonium removal rates of up to 2.5 kg NH4-N/m3·d, while removal efficiencies were as high as 98% and independent of the applied ammonium loading rates. Ammonium loading rates higher than 2.5 kg NH4-N/m3·d resulted in decreased ammonium removal efficiency. The data show that near complete ammonium removal occurred at DO concentrations as low as 0.3-0.5 mg/L. However, the nitrite-nitrogen fraction in the effluent increased from 3.5% to 23.2% when the DO dropped from 1.0 mg/L to approximately 0.4 mg/L, respectively. The high specific removal rates in this system are one order of magnitude higher than that of suspended-growth systems. This can reduce the supplementary reactor volumes required for nitrification to less than 10% of that needed in conventional activated sludge systems. These results clearly indicate the potential economic gains that could be achieved through implementation of this technology.
Operation of a nitrite-type airlift reactor at low DO concentration
Authors: Tokutomi T.
Published: May 2018

Laboratory scale experiments were performed to evaluate the feasibility and potential of nitrite-type nitrification process with an airlift reactor having aerobic granular biomass. Oxygen limitation was selected as the main control parameter for inhibiting the growth of nitrite oxidizer and thus achieving only nitritation. To enhance granule formation, seeding of methanogenic anaerobic granules was used to serve as an initial carrier material. After 90 days of operation at low DO concentration of less than 1.0 mg/l, the maximum nitrite conversion rate of 2.6 g NO2-N/L/d could be achieved. During the continuing year-long stable operation, the granular mass of nitritation granules increased to about 15 g VSS/L with an average granule size of 0.7 mm. Nitrate-N concentration was observed to be below 10 mg/L during the whole operational period. From the results of the experiments, it is concluded that a granule-type airlift reactor with DO control is feasible for achieving stable nitritation.
Nitrification-denitrification via nitrite for nitrogen removal from high nitrogen soybean wastewater with on-line fuzzy control
Authors: Wang S.Y. , Gao D.W. , Peng Y.Z. , Wang P. , Yang Q.
Published: May 2018

This study is to demonstrate the performance of a new technology for complete nitrogen removal from soybean wastewater with high nitrogen concentrations. Nitrification-denitrification via nitrite was performed in three kinds of operating condition, i.e. nitrification-denitrification via nitrite under traditional SBR process, nitrification-denitrification via nitrite by alternating oxic/anoxic under fixed-time control and nitrification-denitrification via nitrite by alternating oxic/anoxic under on-line fuzzy control.The best one is nitrification-denitrification via nitrite by alternating oxic/anoxic under on-line fuzzy control. It not only improves both nitrification and denitrification rates and decreases total reaction time, but also saves the amount of added carbon source and alkalinity. In addition, reaction time can be shortened and operation cost can be saved by using real-time fuzzy control aeration and mixing time. So this method enhances the efficiency and the stability of nitrogen removal, and reduces operating costs and construction investment in the process of wastewater treatment.
Oxidative treatment characteristics of biotreated textile-dyeing wastewater and chemical agents used in a textile-dyeing process by advanced oxidation process
Authors: Lim B.-R. , Hu H.-Y. , Ahn K.-H. , Fujie K.
Published: May 2018

The oxidative treatment characteristics of biotreated textile-dyeing wastewater and typical chemicals such as desizing, scouring, dispersing and swelling agents used in the textile-dyeing process by advanced oxidation process were experimentally studied. The refractory organic matters remained in the effluent of biological treatment process without degradation may be suitable for the improvement of biodegradability and mineralized to CO2 by combined ozonation with and without hydrogen peroxide. On the other hand, the refractory chemicals contained in the scouring agent A and swelling agent may not be mineralized and their biodegradability may not be improved by ozonation. However, the BOD/DOC ratio of scouring agent B increased from 0.3 to 0.45 after ozonation. Based on the results described above, advanced treatment process involving the ozonation without and with the addition of hydrogen peroxide, followed by biological treatment was proposed for the treatment of refractory wastewater discharged from the textile-dyeing process.
Performance of constructed wetland treating wastewater from seafood industry
Authors: Yirong C. , Puetpaiboon U.
Published: May 2018

Wastewater from seafood industry contains high concentrations of organic matter, nitrogen compounds, and solid matter. Constructed wetland can be used as tertiary treatment and for nutrient recycling. This research studied the performance of nitrogen and suspended solids removal efficiency of a constructed wetland treating wastewater from a seafood-processing factory located at Songkhla, southern Thailand. The existing constructed wetland has dimensions of 85 m, 352 m and 1.5 m in width, length and depth respectively, with an area of about 29,920 m2. The water depth of 0.30 m is maintained in operation with plantation of cattails (Typha augustifolia). Flow rate of influent ranged between 500-4,660 m3/d. Average hydraulic retention time in the constructed wetland was about 4.8 days. Influent and effluent from the constructed wetland were collected once a week and analyzed for pH, temperature, dissolved oxygen (DO), biochemical oxygen demand (BOD5), Suspended solid (SS), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3-N), organic nitrogen (Org-N), nitrate (NO3-N), and nitrite (NO2-N). The average removal efficiencies of BOD5, SS, TKN, NH3-N, and Org-N were 84%, 94%, 49%, 52% and 82%, respectively. It was found that the constructed wetland acting as a tertiary treatment process provided additional removal of BOD5, SS and TKN from wastewater from the seafood industry.
Effect of C/N ratio on nitrous oxide emission from swine wastewater treatment process
Authors: Kishida N. , Kim J.H. , Kimochi Y. , Nishimura O. , Sasaki H. , Sudo R.
Published: May 2018

To evaluate control parameters for nitrous oxide (N2O) emissions in the swine wastewater treatment process, the N2O emission was compared in the activated sludge from SBRs acclimated in different carbon/nitrogen (C/N) ratios. N2O emission from a denitrification phase was very strongly dependent on C/N ratio of swine wastewater, and the total N2O emission in the operating condition of BOD5/TN ratio of 2.6 was approximately 270 times greater than that in BOD5/TN ratio of 4.5. However, the effect of C/N ratio on N2O emission amount from nitrification was not significant in an oxic phase study. It is considered that stabilization of the C/N ratio through optimal solid-liquid separation of slurry or use of an external carbon source is indispensable for effective N2O emission control from nitrogen removal process of swine wastewater.
Application of chemical precipitation for piggery wastewater treatment
Authors: Lee S.-H. , Iamchaturapatr J. , Polprasert C. , Ahn K.-H.
Published: May 2018

Several series of experiments were conducted to investigate the treatment of piggery wastewater using chemical precipitation (CP) where various types of coagulants such as aluminium sulfate (Al2(SO4)3), poly aluminium chloride (PAC), ferric chloride (FeCl3), ferric sulfate (Fe2(SO4)3), ferrous sulfate (FeSO4) and ferrous chloride (FeCl2) were used. Throughout the experiments, CP was found to achieve high removal efficiencies for organic compounds and nutrients (nitrogen and phosphorus) from the piggery wastewater. Experimental results showed the optimal doses of FeCl3, Fe2(SO4)3, FeCl2 and FeSO4 was 2.0 g/L, while 0.31 g/L and 2.5 g/L were the optimum dose for PAC and Al2(SO4)3, respectively. The pH range 4-5 resulted in the best performance to all coagulants except FeCl2 and FeSO4, whose optimum pH were more than 6. Percentage removal efficiencies for COD were in the ranges of 70-80%, 90-95% for SS, 80-90% for organic-N and TP. Those removal efficiencies were achieved within 5 min of operation. Three times of repetition in CP resulted in higher removal efficiencies for COD, SS and colour up to 74%, 99% and 94% respectively, in which Al2(SO4)3 was used as the coagulant. Removal efficiencies of various water quality parameters in a continuously operated reactor were similar to those of the batch experiments. Biodegradable ratios (BOD5increased up to 65% after the application of CP.
Tertiary treatment of biologically treated piggery wastewater using vibratory shear-enhanced RO membrane
Authors: Lee J. , Kim S. , Choi J. , Hwang H. , Cha M. , Kim J.
Published: May 2018

This study presents a good example for the tertiary treatment of biologically treated piggery wastewater using vibratory shear enhanced RO membrane (VSEP RO). Through a simple process combination, utilizing Bioceramic SBR(BCS) and VSEP RO, at Gimhae plant livestock wastewater is treated excellently to meet the strict effluent standards. Application of RO membrane directly to the biologically treated effluent has been successful without any pretreatment to reduce high suspended solids. The combination of VESP UF followed by RO filtration processes produced a higher recovery rate in the 3-week pilot test.
The removal of residual organic matter from biologically treated swine wastewater using membrane bioreactor process with powdered activated carbon
Authors: Whang G.D. , Cho Y.M. , Park H. , Jang J.G.
Published: May 2018

The objective of this study was to characterize the mechanisms of the COD removal in the membrane bioreactor (MBR) process with powdered activated carbon (PAC) addition and to determine its optimal operation, for the removal of residual organic matters (ROM) from biologically treated swine wastewater. The MBR process with PAC showed higher removal efficiency of chemical oxygen demand (CODMn) than that without PAC. When the average CODMn concentration of the influent was 217 mg/L, the average CODMn concentration of the permeate from the MBR with PAC was about 41.5 mg/L, indicating an approximate removal efficiency of 81%. On the other hand, the average CODMn concentration of the permeate from the MBR without PAC was 172 mg/L. The PAC dosage estimated to obtain the above removal efficiency was about 0.74 g per litre of influent. Among the total residual organics removed by PAC-added MBR, 46.5% was removed by PAC adsorption, 20.8% by biodegradation, 4.4% by membrane separation, and 9.3% by enhanced microorganism activity. From these results, the MBR process with PAC was considered as a very useful treatment process for the reduction of CODMn in biologically treated swine wastewater.
The effect of intermittent feeding on aerobic granule structure
Authors: McSwain B.S. , Irvine R.L. , Wilderer P.A.
Published: May 2018

Self-immobilized biofilms, or aerobic granules without the addition of carrier material, have only been reported in one suspended growth system, the Sequencing Batch Reactor (SBR) with a very short fill time (dump fill). The SBR utilizes intermittent feeding which creates a period of high load followed by starvation (often referred to as feast-famine). In this experiment, three identical SBRs were operated with different feeding conditions to determine the role of feast-famine on granule formation. All three SBRs were operated with a total volumetric load of 2.4 kg/m3·d. The 90 minute Fill phase was altered for each reactor, providing an increasing time of Aerated Fill. A dump fill condition was applied for one reactor, while the other two reactors were aerated for different times during Fill, resulting in a smaller COD load at the beginning of each React phase. Aerobic granules formed in all reactors, but the structural properties and content of filamentous organisms were clearly dependent on a high feast condition. Only the reactor with dump fill formed compact, stable granules. It is concluded that intermittent feeding associated with the SBR affects the selection and growth of filamentous organisms and has a critical role in granule structure and composition.
Anaerobic ammonium oxidation of ammonium-rich waste streams in fixed-bed reactors
Authors: Fux C. , Marchesi V. , Brunner I. , Siegrist H.
Published: May 2018

The feasibility of anaerobic ammonium oxidation (Anammox) in fixed-bed reactors was evaluated on laboratory and pilot scales. Using synthetic wastewater, the specific nitrogen removal rate was increased from 0.05-0.1 kgNm-3reactord-1 to 0.35-0.38 kgNm-3reactord-1 within a year (T = 22-27°C) in all applications. However, the anammox activity was seriously and repeatedly inhibited at prolonged high nitrite concentrations (e.g. six days at 30-50 gNO2-Nm-3) and recovery was always a lengthy process. But even at a moderate nitrite concentration (11 ± 10 gNO2-Nm-3), the observed specific growth rate was only 0.018 d-1 at 26.4 ± 0.8°C, which corresponds to approximately 0.025 d-1 at 30°C (doubling time: 28 days). In a second experimental period for another 250 days, one of the laboratory reactors was fed with partially nitrified sludge liquors from a domestic wastewater treatment plant (WWTP). In this case, the specific elimination rate was as high as 3.5 kgNm-3reactord-1 at 26-27°C. Independently of the feed, the average nitrogen elimination rate lay between 80-85% in all applications. An appropriate hydraulic design is essential to prevent clogging and local nitrite inhibition in fixed-bed reactors.
Effect of an industrial waste water on the nitrification in fixed-bed biofilm reactors - use of fluorescence in-situ hybridization (FISH)
Authors: Hörsch P. , Leve J. , Frimmel F.H.
Published: May 2018

The influence of an industrial waste water containing partly toxic and poorly biodegradable substances on an autotrophic biocenosis was investigated. Nitrifying bacteria were identified using fluorescently-labeled oligonucleotide probes and epifluorescence microscopy. Industrial waste water was used untreated and after ozonation to simulate the effects of indirect discharge to municipal waste water treatment plants. Results were compared to those obtained with acetate as a non-toxic and easily biodegradable substance and a mixture of acetate and pyruvate. The degradation of ammonium and the formation of nitrite and nitrate were measured and compared with the results obtained by fluorescence in-situ hybridization (FISH). The untreated waste water, containing higher amounts of refractory substances, disturbed nitrification, which was restored after reaching higher elimination of the organic substances. However, it showed only minor effects on the bacterial composition. These findings were similar to those reached by the addition of acetate and pyruvate. On the other hand, the ozonated waste water, showing higher toxicity than the untreated waste water, caused a stabilization in nitrification, but the composition of the population of ammonium-oxidizing bacteria changed significantly. In all cases, nitrite-oxidizing bacteria were only little affected both in activity and abundance.
Design of water hyacinth ponds for removing algal particles from waste stabilization ponds
Authors: Kim Y. , Giokas D.L. , Chung P.-G. , Lee D.-R.
Published: May 2018

In this study it was demonstrated that when water hyacinth ponds (WHPs) are used for polishing the effluent from waste stabilization ponds (WSPs), suspended solids (mostly algal particles) are efficiently separated, which also resulted in the reduction of insoluble forms of COD and nutrients. The high pH of the WSPs effluent was easily adjusted to 6-7 as it passed through the WHPs. However, the use of water hyacinth rapidly reduced dissolved oxygen at the first cell to less than three mg/L or very frequently to a level of anaerobic state. Reduction of suspended solids at the WHPs mainly depends on the detention time and pH. An empirical separation model incorporating the detention time and pH dependence was developed.
Performance of a small wastewater stabilisation pond system in tropical climate in Dar es Salaam, Tanzania
Authors: Mbwele L. , Rubindamayugi M. , Kivaisi A. , Dalhammar G.
Published: May 2018

Waste stabilisation ponds (WSP) are widely used in Tanzania. Their traditional design focuses on BOD and pathogen removal, but nutrient removal is equally important. WSP performance was evaluated to come up with information that would be used to evaluate pond performance. Samples were analysed twice a month for six months. Results showed total and faecal coliform removal by 4 log units (99.96 and 99.98% respectively). There was partial reduction of COD, BOD, (46% and 27% respectively), conductivity and total dissolved solids (32.6 and 32.4% respectively). Variation for the nutrients like inorganic phosphorus, ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen was not consistent and there was practically no reduction, although there is some nitrification taking place. From this study it may be concluded that BOD and nutrients may not be useful to evaluate pond performance. Instead parameters such as conductivity, total dissolved solids, coliform bacteria, dissolved oxygen, pH and chlorophyll would be suitable for that purpose, due to their consistent variation within cells of the pond system. But BOD and nutrient removal are important and have to be improved to enhance treatment in the WSP.
Hydrogen-based, hollow-fiber membrane biofilm reactor for reduction of perchlorate and other oxidized contaminants
Authors: Nerenberg R. , Rittmann B.E.
Published: May 2018

Many oxidized pollutants, such as nitrate, perchlorate, bromate, and chlorinated solvents, can be microbially reduced to less toxic or less soluble forms. For drinking water treatment, an electron donor must be added. Hydrogen is an ideal electron donor, as it is non-toxic, inexpensive, and sparsely soluble. We tested a hydrogen-based, hollow-fiber membrane biofilm reactor (MBfR) for reduction of perchlorate, bromate, chlorate, chlorite, chromate, selenate, selenite, and dichloromethane. The influent included 5 mg/L nitrate or 8 mg/L oxygen as a primary electron accepting substrate, plus 1 mg/L of the contaminant. The mixed-culture reactor was operated at a pH of 7 and with a 25 minute hydraulic detention time. High recirculation rates provided completely mixed conditions. The objective was to screen for the reduction of each contaminant. The tests were short-term, without allowing time for the reactor to adapt to the contaminants. Nitrate and oxygen were reduced by over 99 percent for all tests. Removals for the contaminants ranged from a minimum of 29% for chlorate to over 95% for bromate. Results show that the tested contaminants can be removed as secondary substrates in an MBfR, and that the MBfR may be suitable for treating these and other oxidized contaminants in drinking water.
Development of a knowledge-based decision support system for identifying adequate wastewater treatment for small communities
Authors: Comas J. , Alemany J. , Poch M. , Torrens A. , Salgot M. , Bou J.
Published: May 2018

The identification of adequate treatment for small communities is a complex problem since it makes it necessary to combine aspects of the community and landscape, the receiving environment, and the available wastewater treatment technologies. This paper presents the development and implementation of a Knowledge-Based Decision Support System (KB-DSS) to tackle this problem. Different knowledge sources have been consulted in order to make up a comprehensive and accurate knowledge base. The core of the KB-DSS embraces two objectives. The first one is to assist in the selection of the treatment level adequate to fulfil the target quality standards for the receiving environment. The second one is to select the specific type of treatment. The KB-DSS is being applied to each one of the 3,482 different small communities comprised in the Small Communities Wastewater Treatment Plan of Catalonia, grouped according to river catchments. This paper also summarizes the different steps involved in the operation of the knowledge-based DSS when solving a real case study.
Upgrading of the biotreatment in a pharmaceutical industry with activated carbon addition
Authors: Çeçen F. , Aktas Ö
Published: May 2018

The impact of powdered activated carbon (PAC) on the biotreatment of a chemical synthesis wastewater emerging from a pharmaceutical industry was studied. The aim of this addition was to decrease inhibitory and non-biodegradable organics. In the first step, PAC was directly added to activated sludge. In the next step, the wastewater was first contacted with PAC and then treated in an activated sludge reactor. COD, oxygen uptake rate (OUR) and ultraviolet-visible (UV-Vis) spectral measurements were carried out for the evaluation of performance. Direct PAC addition and PAC pretreatment led to similar results, but direct PAC addition was considered more practical than pretreatment with PAC. With the addition of PAC, the level of non-biodegradable matter and the colour of the wastewater were significantly reduced. In any case, the addition of PAC increased the OUR of activated sludge, indicating that inhibition could be decreased. The combined evaluation of OUR, spectral parameters and COD gave a better insight into the processes taking place than the COD parameter alone.
Biological denitrification of drinking water using various natural organic solid substrates
Authors: Aslan S. , Türkman A.
Published: May 2018

Denitrification of drinking water was studied using various natural organic solid substrates (NOSS) such as poplar, hornbeam, pine shavings and wheat straw as a carbon source in a batch unit. The highest nitrate removal efficiency was observed with the wheat straw, so it was chosen as the carbon source for biodenitrification in an upflow laboratory reactor. In order to remove solid particles from the effluent water, a sand filter unit was placed after the denitrification reactor. The soluble DOC contents in the reactor affected the efficiency of nitrate elimination and nitrate concentration of the effluent water remained below acceptable values (50 mg/l NO3-). In order to remove colour, DOC and nitrate from the water, powdered activated carbon adsorption studies were performed in the batch unit.
Wastewater characteristics from Greek wineries and distilleries
Authors: Vlyssides A.G. , Barampouti E.M. , Mai S.
Published: May 2018

The present paper deals with the characterization of wastewater generated from Greek wineries and wine distilleries. The quantity and the quality of the wastewater of a distillery depends on the type of wine (white or red), on the processes followed for the production of wine as well as on the volume of the tanks that are used. The total production of wastewater from a winery is about 1.2 times greater than the production of wine with BOD5 1740 mg/l and 1970 mg/l for white and red wine respectively, while the corresponding prices for COD are 3112 mg/l and 3997 mg/l and for the total phenolic compounds 280 and 1440 mg/l respectively. From these results, it is expected that the biological treatment of wastewater from white wines will be more efficient than that from red wines. The characteristics from the waste (vinasses) from the distillation of wines and wine lees are also presented.
Chemical hazard identification and assessment tool for evaluation of stormwater priority pollutants
Authors: Eriksson E. , Baun A. , Mikkelsen P.S. , Ledin A.
Published: May 2018

Assessment of chemical hazards is a critical issue, which have to be dealt with when evaluating different strategies for sustainable handling of stormwater. In the present study, a methodology for identifying the most critical and representative chemical pollutants was developed. A list of selected stormwater priority pollutants (SSPP-list) is the out-put from the procedure. Two different strategies for handling of stormwater were considered; discharge into a surface water recipient and infiltration. However, the same methodology can be used for other types of wastewater and other strategies for handling and treatment. A literature survey revealed that at least 656 xenobiotic organic compounds (XOCs) could be present in stormwater. In the next step, 233 XOCs were evaluated with respect to the potential for being hazardous towards either aquatic living organisms or humans, or causing technical or aesthetical problems. 121 XOCs were found have at least one of these negative effects, while 26 XOCs could not be assessed due to the lack of data. The hazard assessment showed that 40 XOCs had a PEC/PNEC ratio above one., e.g. they should be considered as priority pollutants. The final step is the expert judgement, which resulted in a final SSPP-list containing 16 selected priority pollutants.
High-rate stormwater clarification with polymeric flocculant addition
Authors: Wood J. , He C. , Rochfort Q. , Marsalek J. , Seto P. , Yang M. , Chessie P. , Kok S.
Published: May 2018

Treatment of urban stormwater by clarification, with flocculant addition, was studied in Toronto, Canada using a pilot-scale clarifier with removable lamellar plates. Almost 90 stormwater runoff events were characterised at the study site and found fairly polluted. The previous research phase indicated good treatability of this stormwater by lamellar clarification with flocculant addition (total suspended solids, TSS, removal of 84%, at a surface load of 15 m/h), but there were concerns about cleaning plates after storm events. With the aid of numerical modelling, hydraulic improvements to the clarifier inlet zone were retrofitted in 2004 and permitted the removal of the lamellar pack without a loss in treatment efficiency. In the modified clarifier, a cationic polymeric flocculant dosage of 4 mg/L with conventional clarification provided a TSS removal of 77%, at surface loads up to 43 m/h. The use of the polymer did not increase the acute toxicity of the treated effluent. The clarifier sludge was severely polluted by several heavy metals and would require special disposal. The treatment process tested could be well applied in projects requiring intensive stormwater treatment at compact sites.
Radar-based alert system to operate a sewerage network: relevance and operational effectiveness after several years of use
Authors: Faure D. , Payrastre O. , Auchet P.
Published: May 2018

Since January 2000, the sewerage network of a very urbanised catchment area in the Greater Nancy Urban Community has been operated according to the alarms generated in real time by a storm alert system using weather radar data. This alert system is based on an automatic identification of intense rain cells in the radar images. This paper presents the characteristics of this alert system and synthesises the main results of two complementary studies realised in 2002 in order to estimate the relevance and the operational effectiveness of the alert system.

The first study consisted in an off-line analysis of almost 50,000 intense rain cells detected in four years of historical radar data. The second study was an analysis of the experience feedback after two years of operational use of this alert system. The results of these studies are discussed in function of the initial operational objectives.
An integrated inundation model for highly developed urban areas
Authors: Chen A.S. , Hsu M.H. , Chen T.S. , Chang T.J.
Published: May 2018

A numerical model is developed in this study with various components for simulating the complex flow phenomena in urban drainage basins. The model integrates the HEC-1 model, a 1-D dynamic channel-flow model, a 2-D non-inertia overland-flow model and the SWMM model to reflect the hydraulic processes in areas with different characteristics. The inundation of underground infrastructure during flood is also considered in the model. The typhoon Nari event in 2001, which resulted in severe flood in downtown Taipei, is simulated by the model. The result is compared with the survey records of flooded areas, which reveals the storage effect of underground infrastrucures is significant to the simulation results of highly developed urban areas.
Identification of ecological status of stream impacted by urban drainage
Authors: Komínková D. , Stránský D. , Št'astná G. , Caletková J. , Nabělková J. , Handová Z.
Published: May 2018

The adoption and implementation of the Directive 2000/60/EC with respect to crucial changes in an approach to water protection require a complex methodology for river and stream status assessment. This paper presents a possible method for assessing the ecological status of urban streams, on for example the Botic creek, the largest tributary of the Vltava River in Prague. The study stream does not possess a good ecological status. The degradation of the ecosystem quality is caused mainly by combined sewer overflows, which reduce water and sediment quality and induce chemical and hydraulic stress for the benthic community.
Spatial variability of characteristics and origins of urban wet weather pollution in combined sewers
Authors: Kafi-Benyahia M. , Gromaire M.G. , Chebbo G.
Published: May 2018

An experimental on-site observatory of urban pollutant loads in combined sewers was created in the centre of Paris to quantify and characterise the dry and wet weather flow in relation to spatial scale. Eight rainfall events were studied from April 2003 to May 2004. Samples were analysed for suspended solids, organic matter, nitrogen and heavy metals. Results confirm the extent of wet weather pollution. They have shown the relative homogeneity of SS and organic matter characteristics from one urban catchment area to another. Two groups of heavy metals were identified. The first one concerns Cu, which has a higher concentration in wet weather flow (WWF) than in dry weather flow (DWF), and runoff. The second includes Cd, Pb and Zn, where higher concentrations were measured in urban runoff than in WWF and DWF. A first evaluation of contribution of wastewater, urban runoff and sewer deposit erosion sources to wet weather pollution was established and has highlighted the contribution of wastewater and sewer deposits to this pollution. However, it has shown that sewer deposit erosion remains an important source of wet weather pollution at different spatial scales.
Effect of detached/re-suspended solids from sewer sediment on the sewage phase bacterial activity
Authors: Leung H. D. , Chen G. , Sharma K.
Published: May 2018

This study was conducted to make an assessment of the effects of the detached/re-suspended solids on the bacterial activity in the sewage phase of a gravity sewer. A physical sewer-model was used to simulate two extreme conditions: sewage flow without the presence of sewer sediment, and filtered sewage flow with the sediment. The first scenario was to evaluate the effect of the settling of solids on the bacterial activity, while the second scenario was to examine the effect of purely re-suspended or detached solids. The water media were aerated to obtain an initial DO level at about 6 mg/L, and the bacterial activity was monitored at a regular time interval during each operation. Two bacterial cell staining techniques, one using 4′, 6-diamidino-2-phenyl indole (DAPI), and another using 5-cyano 2, 3-ditoyl tetrazolium chloride (CTC), were employed to measure the amount of total and respiring bacteria, respectively. Both the DAPI and CTC counts decreased with time in the first case, while that increased with time in the second case. The bacterial activity in a sewer phase was observed to be contributed by smaller sized particles. Also, the solids originated from the sewer sediment through re-suspension or detachment demonstrated a higher bacterial activity than the solids originally present in the sewage.
Treatment of nitrogen-rich wastewater using partial nitrification and Anammox in the CANON process
Authors: Third K.A. , Paxman J. , Schmid M. , Strous M. , Jetten M.S.M. , Cord-Ruwisch R.
Published: May 2018

Partial nitrification combined with Anammox in a single reactor (the CANON process) is an energy-efficient N-removal technology that could substantially lower the N-load of a WWTP by separate treatment of nitrogen-rich side streams, preventing the need for extensive expansion and reducing the total energy requirement. This study looks at the enrichment of Anammox from activated sludge and its application in the CANON process on lab-scale. The aim was to identify the critical process control parameters necessary for successful operation of CANON. An Anammox culture capable of removing 0.6 kg N/m3/d was enriched in 14 weeks in a sequencing batch reactor. Nitrifying biomass was inoculated into the Anammox reactor (10% v/v) together with limited oxygen supply (< 8 mL/min) to initiate the CANON process in continuous culture. The small flocs formed by the biomass (< 1000 μm) were sensitive to low O2 concentrations (< 0.1 mg/L) which prevented simultaneous nitrification and Anammox. Operation with 20 min aerobiosis and 30 min anaerobiosis was necessary to achieve sustained, completely autotrophic N-removal for an extended period at a rate of 0.08 kg N/m3/d. Essential process control parameters for stable CANON operation were the nitrite concentration, oxygen concentration, pH and the temperature.
Runoff modelling using radar data and flow measurements in a stochastic state space approach
Authors: Krämer S. , Grum M. , Verworn H.-R. , Redder A.
Published: May 2018

In urban drainage the estimation of runoff with the help of models is a complex task. This is in part due to the fact that rainfall, the most important input to urban drainage modelling, is highly uncertain. Added to the uncertainty of rainfall is the complexity of performing accurate flow measurements. In terms of deterministic modelling techniques these are needed for calibration and evaluation of the applied model. Therefore, the uncertainties of rainfall and flow measurements have a severe impact on the model parameters and results. To overcome these problems a new methodology has been developed which is based on simple rain plane and runoff models that are incorporated into a stochastic state space model approach. The state estimation is done by using the extended Kalman filter in combination with a maximum likelihood criterion and an off-line optimization routine. This paper presents the results of this new methodology with respect to the combined consideration of uncertainties in distributed rainfall derived from radar data and uncertainties in measured flows in an urban catchment within the Emscher river basin, Germany.
Modelling non-structural Best Management Practices– focus on reductions in stormwater pollution
Authors: Ahlman S. , Malm A. , Kant H. , Svensson G. , Karlsson P.
Published: May 2018

This paper describes a modelling approach for evaluating the efficiency of different non-structural best management practices for stormwater management. A scenario with a set of source reduction practices was simulated using the substance flow model SEWSYS for an urban catchment in the city of Göteborg, Sweden. The scenario is based on a hypothetical control program that includes prevention, education and regulations. The simulation shows relatively high reductions of copper and PAH, 77% and 50%, respectively. The reduction in copper is mainly due to less copper roof corrosion and brake wear, while reduced road wear has the greatest effect for PAH. An important result from this study is that the non-structural BMPs applied did not give a sufficient reduction in pollution to meet the desirable environmental quality criteria. To meet these criteria, additional BMPs must be implemented, preferably a combination of both non-structural and structural measures.
Automatic calibration of urban drainage model using a novel multi-objective genetic algorithm
Authors: di Pierro F. , Djordjević S. , Kapelan Z. , Khu S.-T. , Savić D. , Walters G.A.
Published: May 2018

In order to successfully calibrate an urban drainage model, multiple calibration criteria should be considered. This raises the issue of adopting a method for comparing different solutions (parameter sets) according to a set of objectives. Amongst the global optimization techniques that have blossomed in recent years, Multi Objective Genetic Algorithms (MOGA) have proved effective in numerous engineering applications, including sewer network modelling. Most of the techniques rely on the condition of Pareto efficiency to compare different solutions. However, as the number of criteria increases, the ratio of Pareto optimal to feasible solutions increases as well. The pitfalls are twofold: the efficiency of the genetic algorithm search worsens and decision makers are presented with an overwhelming number of equally optimal solutions. This paper proposes a new MOGA, the Preference Ordering Genetic Algorithm, which alleviates the drawbacks of conventional Pareto-based methods. The efficacy of the algorithm is demonstrated on the calibration of a physically-based, distributed sewer network model and the results are compared with those obtained by NSGA-II, a widely used MOGA.
Model description of storage and infiltration functions of infiltration facilities for urban runoff analysis by a distributed model
Authors: Furumai H. , Jinadasa H.K.P.K. , Murakami M. , Nakajima F. , Aryal R.K.
Published: May 2018

Although there have been simulation researches focusing on reduction of stormwater peak flow by introduced infiltration facilities, model simulation of dynamic runoff behavior is still limited for frequently occurring rainfall events with weak intensity. Therefore, dynamic simulation was carried out in two urban drainages with infiltration facilities incorporated with a distributed model using two methods for describing functions of infiltration facilities. A method adjusting effective rainfall model gave poor simulation of runoff behavior in light rainfalls. Another method considering dynamic change of storage capacity as well as infiltration rate gave satisfactory estimation of the runoff in both drainages. In addition, assumption of facility clogging improved the agreement between measured and simulated hydrographs in small and medium-sized rainfall. Therefore, the proposed method might be useful for quantifying the secondary effects of the infiltration facilities on groundwater recharge and urban non-point pollutant trapping as well as runoff reduction.
Development of a method for assessing flood vulnerability
Authors: Connor R.F. , Hiroki K.
Published: May 2018

Over the past few decades, a growing number of studies have been conducted on the mechanisms responsible for climate change and the elaboration of future climate scenarios. More recently, studies have emerged examining the potential effects of climate change on human societies, including how variations in hydrological regimes impact water resources management. According to the Intergovernmental Panel on Climate Change's third assessment report, climate change will lead to an intensification of the hydrological cycle, resulting in greater variability in precipitation patterns and an increase in the intensity and frequency of severe storms and other extreme events. In other words, climate change will likely increase the risks of flooding in many areas. Structural and non-structural countermeasures are available to reduce flood vulnerability, but implementing new measures can be a lengthy process requiring political and financial support. In order to help guide such policy decisions, a method for assessing flood vulnerability due to climate change is proposed. In this preliminary study, multivariate analysis has been used to develop a Flood Vulnerability Index (FVI), which allows for a comparative analysis of flood vulnerability between different basins. Once fully developed, the FVI will also allow users to identify the main factors responsible for a basin's vulnerability, making it a valuable tool to assist in priority setting within decision-making processes.
Stormwater quality models: sensitivity to calibration data
Authors: Mourad M. , Bertrand-Krajewski J.-L. , Chebbo G.
Published: May 2018

Stormwater quality modelling is a useful tool in sewer systems management. Available models range from simple to detailed complex ones. The models need local data to be calibrated. In practice, calibration data are rather lacking. Only few measured events are commonly used. In this paper, the effect of the number and the variability of calibration data on models of various levels of complexity are investigated. The study is carried out on “Le Marais” catchment for suspended solids where 40 reliable measured events and good knowledge of the sewer system are available. The method used is based on resampling subsets of measured events among the 40 available ones. Three types of models were calibrated using subsets of events of different sizes and characteristics resampled among the 40 available ones. For each calibration, the model was validated against the remaining events to stand upon the quality of the model. It was found that the models are quite sensitive to calibration data, a problem neglected in practical studies. The use of more complex models does not necessarily improve modelling results since more problems and error sources are to be expected. The findings are specific to “Le Marais” catchment and the models used.
Water systems and risk analysis
Authors: Hoes O.A.C. , Schuurmans W. , Strijker J.
Published: May 2018

Worldwide the water management sector is about to review the design standards for water systems, as expected climate changes may possibly increase the frequency of flood events. This paper reviews new flood standards for surface water systems in The Netherlands, also presenting a cost-benefit analysis. Flood standards were formulated after several serious incidents in 1998 and 2001 to inform residents about the level of protection that they may expect to receive. At this moment all water boards are about to evaluate their water systems using these standards. The cost-benefit approach has been applied to determine whether the necessary measures to comply with such standards were cost-effective. We found that the standards make too much a simplification of the variety of water systems, and lead to costly measures without being beneficial while many small-scale floods in The Netherlands do not cause any significant damage. A better starting point to anticipate on climate change is to prevent damage, instead of the prevention of flooding.