bluuebunny/crossref_metadata_2025 huggingface dataset:
Elimination of p-chlorophenol in biofilm reactors - a comparative study of continuous flow and sequenced batch operation
Authors: Kaballo Hans-Peter , Zhao Yuangang , Wilderer Peter A.
Published: May 2018

The chlorophenol elimination potential of two identically designed fixed bed biofilm reactors was compared. One of the reactors was operated continuously, and the other in sequenced batch mode. In the continuous flow biofilm reactor (CFBR) a stratification of biomass occurred, whereas biomass in the sequencing batch biofilm reactor (SBBR) developed uniformly due to the use of an advanced fill strategy. Recirculation was needed to overcome biosorption during filling and to achieve equal biomass distribution. Under shock loading, degradation in SBBR was better than in CFBR. However, even the CFBR showed a high flexibility, i.e. it performed better than expected. Sorption properties in both reactors seem to be responsible for the flexibility in terms of break through. Experimental studies and modelling of sorption properties are necessary to describe the response of biofilm reactors to unsteady state conditions.
UK research into the performance of permeable pavement, reservoir structures in controlling stormwater discharge quantity and quality
Authors: Pratt C. J. , Mantle J. D. G. , Schofield P. A.
Published: May 2018

The paper reports on a field study on a permeable, reservoir pavement constructed in 1986 at Nottingham, UK; surfaced with permeable, concrete block paving; and with a different sub-base stone-type in each of four reservoirs, from which the discharges were monitored for quantity and water quality. Hydrological relationships involving rainfall, outflow, outflow duration and antecedent conditions are presented. Water quality parameters are shown to be stable in value after some six months, by which time surface contaminants on the sub-base stone had been washed out of the construction. As outflow volume is reduced and water quality parameters (SS and Pb) are low in value, pollutant outflow loadings are significantly lower than with traditional, impermeable surfaces.
An infiltration device as a best management practice for immobilizing heavy metals in urban highway runoff
Authors: Sansalone J. J. , Buchberger S. G.
Published: May 2018

Anthropogenic constituents in highway runoff include metal elements and suspended solids which result from traffic activities, atmospheric deposition, roadway degradation and highway maintenance. A best management practice (BMP) for immobilizing heavy metals and suspended solids is a partial exfiltration trench (PET). A PET is designed to exfiltrate a percentage of infiltrated runoff to subsoil with the balance discharged through an underdrain. The PET functions through adsorptive-filtration, where dissolved metals are immobilized through sorption and metals associated with suspended solids are immobilized through filtration. An important PET design consideration is potential association of heavy metals with suspended solids. This paper investigates the correlation between heavy metals and suspended solids in highway runoff. Results indicate a strong positive correlation between heavy metal and suspended solid concentrations for snow washoff events and a poor correlation for rainfall-runoff events. Similar results are observed for correlations between metals and suspended particle sizes. From these findings, it is argued that a PET holds promise as a device for immobilizing metals associated with suspended solids transported during snow washoff and long duration rainfall events.
Effects of biofilm structure, microbial distributions and mass transport on biodegradation processes
Authors: Bishop Paul L. , Zhang Tian C. , Fu Yun-Chang
Published: May 2018

The influence of biofilm structure on transport and transformation processes in biofilms has been investigated microscopically using microelectrodes, a micro-slicing procedure and various chemical and microbiological tests. The study demonstrates that the biofilm structure is highly stratified, characterized by an increase of biofilm density, a decrease of metabolically active biomass, and a decrease of porosity with biofilm depth. Both the effective diffusivity for dissolved oxygen and the effectiveness factor decrease with biofilm depth. Competition for substrate and space in biofilms results in this stratified structure, which is also affected by biofilm thickness. The study reveals that there are different trends for the density increase and the decreases of porosity, microbial activity and DO effective diffusivity with biofilm depth for different biofilm thicknesses. The results of this study are helpful in obtaining a clearer physical description of biofilms, and help to bridge the gap between the mathematical modelling and external-phenomenon observation of biofilm systems.
A stochastic approach to designing wetlands for stormwater pollution control
Authors: Wong Tony H. F. , Somes N. L. G.
Published: May 2018

Central to wetland design for stormwater pollution management is the proper control of the hydrologic regime of these wetlands and wet detention basins. The paper proposes a stochastic approach in determining the appropriate wetland size for stormwater treatment in recognition of the inherent variability of stormwater runoff and pollutant load generation within a storm event and between storm event. The determination of wetland size would include the use of stochastic generation of stormwater runoff and continuous wetland behaviour simulation. A typical design chart summarising the interaction between wetland size, prescribed retention period of stormwater and wetland hydrologic effectiveness for Melbourne is presented. The chart enables the selection of the appropriate storage volume and outlet characteristics on the basis of long-term average effectiveness of the wetland to retain stormwater over a desired minimum period rather than a prescribed level of performance for an individual probablistic event.
Modelling of inundation management during extreme storms
Authors: Barnett A. G. , MacMurray H. L. , Wallace P. L. , Lester R. T.
Published: May 2018

The “major/minor” approach is being adopted as standard urban drainage design practice in many countries. Further to the normal primary drainage design for minor storms, this approach now requires management of inundation during extreme storms of return period fifty years or more. Surface flows then have to be investigated over an urban topography which is highly irregular and initially dry, and the transition from these conditions to major storm flows is difficult to analyse. The proposed modelling solution is based on the full integral hydraulic equations incorporating possible shock fronts. Wetting and drying simulation, careful channel resolution at low flows, and implicit solution methods with flat response properties are also important. Key points are illustrated by case studies.
Degradation of chlorinated aromatic compounds in UASB reactors
Authors: Christiansen Nina , Hendriksen Hanne V. , Järvinen Kimmo T. , Ahring Birgitte K.
Published: May 2018

Data on anaerobic degradation of chloroaromatic compounds in Upflow Anaerobic Sludge Blanket Reactors (UASB-reactor) are presented and compared. Special attention is given to the metabolic pathways for degradation of chlorinated phenols by granular sludge. Results indicate that PCP can be degraded in UASB-reactors via stepwise dechlorination to phenol. Phenol will subsequently be converted to benzoate before ring cleavage. Dechlorination proceeds via different pathways dependent upon the inocula used. Results are further presented on the design of special metabolic pathways in granules which do not possess this activity using the dechlorinating organism, Desulfomonile tiedjei. Additionally, it is shown that it is possible to immobilize Dechlorosporium hafniense, a newly isolated dechlorinating anaerobe, into granular sludge, thereby introducing an ability not previously present in the granules.
The Activated Sludge Model No. 2: biological phosphorus removal
Authors: Gujer W. , Henze M. , Mino T. , Matsuo T. , Wentzel M. C. , Marais G. v. R.
Published: May 2018

The Activated Sludge Model No. 2 is introduced as a further development of Activated Sludge Model No. 1. Model No. 2 introduces phosphorus accumulating organisms (PAO) and allows us to simulate the behaviour of biological nutrient removal activated sludge systems. Typical wastewater composition and a set of stoichiometric and kinetic parameters are provided in order to make reasonable predictions. The model has not yet been calibrated or verified in any full-scale application. This report contains a simplified version of the full Model No. 2; the full model is published in the final report of the Task Group (Henze et al., 1994).
Wastewater treatment utilizing submarine outfalls: the role of science, communications and public involvement in the decision-making process
Authors: Rogers Vernon J.
Published: May 2018

In Victoria, British Columbia, Canada, sewage is discharged to the marine environment after preliminary treatment by screening. In 1992, the CRD undertook related technical investigations including studies of the ocean sediments in the area of the two main outfalls. The results of these investigations, together with information concerning other aspects of liquid waste management, were then described as part of a public involvement program which culminated in a referendum held in November 1992. The referendum invited the public to choose from three options for land-based sewage treatment. All three options included programs such as source control, that offered clear environmental benefits. The majority of voters (56%) decided in favour of the option which includes continuation of the existing level of sewage treatment. This paper describes the process followed, and shows how good science, effective communication, and public involvement can aid a rational approach to decision-making about marine environmental management and wastewater treatment utilizing submarine outfalls. It also highlights some important points concerning development of community and environmental priorities, identification of stakeholders, public involvement, and the role of independent scientific assessment.
Wastewater and biomass characterization for the Activated Sludge Model No. 2: biological phosphorus removal
Authors: Henze M. , Gujer W. , Mino T. , Matsuo T. , Wentzel M. C. , Marais G. v. R.
Published: May 2018

The characterization of wastewater and biomass in relation to the Activated Sludge Model No. 2 is described. A new fraction of organic fermentable matter is needed. Phosphate accumulating organisms and their structural compounds polyphosphate and polyhydroxyalkanoate have to be included in the biomass characterization. There is still a need for development of analytical methods for characterization of the various components.
Modelling glycogen storage and denitrification capability of microorganisms in enhanced biological phosphate removal processes
Authors: Mino Takashi , Liu Wen-Tso , Kurisu Futoshi , Matsuo Tomonori
Published: May 2018

Some important aspects in the modelling of enhanced biological phosphate removal processes which are not considered in IAWQ Activated Sludge Model No. 2 are discussed and three submodels are proposed. When denitrification by polyphosphate accumulating organisms (PAOs) is introduced to the model, anoxic uptake of soluble orthophosphate, which is sometimes observed in the real world can be expressed. Appropriate values of stoichiometric and kinetic coefficients remain to be determined. Glycogen storage capability is another essential character of PAOs. By incorporating biochemical information obtained so far, the processes relating to glycogen storage can be modelled. The model implies very delicate kinetic characteristics of PAOs. A group of organisms, which can cause deterioration of phosphate removal and has been referred to as “G bacterium”, is characterized as glycogen accumulating non-poly-P organisms (GAOs). A preliminary model for GAO metabolism is proposed.
Examination of the Activated Sludge Model No. 2 with an alternating process
Authors: Isaacs S. , Hansen J. A. , Schmidt K. , Henze M.
Published: May 2018

Three series of data obtained in a pilot-scale alternating-type activated sludge nutrient removal process are examined in light of the recently introduced Activated Sludge Model No. 2 (ASM2). The first data series was collected while adding acetate to the inlet to improve phosphate removal. ASM2 can explain why phosphate levels first rise before an improvement occurs based on a slow build-up of internally stored polyhydroxyalkanoates (PHA). The second and third data series represent batch experiments performed in the pilot plant, and show the effect of nitrate on phosphate release. ASM2 could describe the second data series well after including one additional reaction to account for denitrification by phosphate accumulating organisms. The third data series examines the effect of the rate of acetate addition, and shows that this affects the rate of anoxic phosphate release more strongly than it does the denitrification rate.
A metabolic model for the biological phosphorus removal process
Authors: Smolders G. J. F. , van Loosdrecht M. C. M. , Heijnen J. J.
Published: May 2018

A structured metabolic model of the biological phosphorus removal process has been developed. In this approach the model is based on the bioenergetics and stoichiometry of the metabolism. All relevant metabolic reactions underlying the P-metabolism, considering also ATP and NADH2, are described. The derived set of stoichiometry based linear relations is used to reduce the number of reactions and conversions rates required to describe the process. The model predictions were experimentally verified by measurement of the external acetate, phosphate and ammonium concentrations as well as the internal fractions of PHB and glycogen. The model is applied to dynamic and steady-state situations over a wide range of sludge ages. The derived structured metabolic model is very well capable of describing the complex conversions of the biological phosphorus removal process.
Methods for studying dissolved oxygen levels in coastal and estuarine waters receiving combined sewer overflows
Authors: Revilla José A. , Koev Kalin N. , Díaz Rafael , Álvarez César , Roldán Antonio
Published: May 2018

One factor in determining the transport capacity of coastal interceptors in Combined Sewer Systems (CSS) is the reduction of Dissolved Oxygen (DO) in coastal waters originating from the overflows.

The study of the evolution of DO in coastal zones is complex. The high computational cost of using mathematical models discriminates against the required probabilistic analysis being undertaken. Alternative methods, based on such mathematical modelling, employed in a limited number of cases, are therefore needed.

In this paper two alternative methods are presented for the study of oxygen deficit resulting from overflows of CSS. In the first, statistical analyses focus on the causes of the deficit (the volume discharged). The second concentrates on the effects (the concentrations of oxygen in the sea). Both methods have been applied in a study of the coastal interceptor at Pasajes Estuary (Guipúzcoa, Spain) with similar results.
Dredged material of Izmir harbor: its behavior and pollution potential
Authors: Filibeli Ayse , Yilmaz Recep , Alyanak Ibrahim
Published: May 2018

The Arap and Melez Rivers discharge to Izmir Bay bringing wastewater together with rainwater coming from their catchment areas. There is an artificial harbor built at the discharge point of the Melez River acting as a sedimentation area for the suspended matter carried by these rivers. This area has a storage capacity of 3 to 4 years. After this period, the sediments are dredged and disposed from the region. In this study, various studies were carried out in order to determine the geotechnical properties and pollution parameters of the sediments; the results of many previous studies are also given. In the analyses done on dredging samples, it was observed that sulfur, oil and grease, phosphorus, nitrogen and heavy metal concentrations were very high. The reason for these high concentrations is the direct discharge of untreated wastewater formed in the industries located along the Arap and Melez Rivers. The pollutants carried to Izmir Bay by these rivers then settle down inside the artificial harbor and reach high concentrations in bottom sediments. As a result of this study, some possible environmental effects of land disposal of this material are discussed and suggestions are given for final disposal alternatives.
Success and shortcomings of clarifier modelling
Authors: Krebs Peter
Published: May 2018

Various types of final clarifier model are introduced. The approaches and simplifications used for one-dimensional modelling are outlined, whilst new results of hydrodynamic modelling demonstrate how complex the flow field and the interactions with the settling behaviour of the sludge are. Based on the examination of which processes and boundary conditions affect the clarifier performance, what basic knowledge is lacking for modelling is analysed. One- and two-dimensional models are assessed with respect to their capacities and their shortcomings. Finally, the promising applications of the various models are pointed out, and future research potential for significant improvement of modelling is indicated.
Computer-aided design of submarine pipelines
Authors: Gökkus ümit
Published: May 2018

The computerization of pipeline design is relatively important for the engineering feasibility of submarine pipelines. The changing environmental conditions make difficulties for the stability calculation of each pipe segment on line. For this reason, the computer study will provide many advantages during the design of pipeline. The different environmental and functional parameters can be easily tried on line and the most suitable size of structure against the extreme environmental conditions can be determined.

This study deals with the general design principles especially including the engineering studies, i.e. wave statistical analysis, transformation of waves, stability analysis, and developed computer program to achieve both the stabilization of pipeline and aid for drawing the route together with user in some stages of the design.

Finally, the outline of the program is briefly described and a flow chart is presented.
Mineralisation and pathogen removal in gravel bed hydroponic constructed wetlands for wastewater treatment
Authors: Williams J. , Bahgat M. , May E. , Ford M. , Butler J.
Published: May 2018

Gravel Bed Hydroponics (GBH) is a constructed wetland system for sewage treatment which has proved effective for tertiary treatment in the UK and secondary treatment in Egypt. Significant improvements in effluent quality have been observed in 100 m long field scale beds planted with Phragmites australis, resulting in large reductions in BOD, suspended solids and ammoniacal N. For such GBH beds, operating optimally with a residence time of about 6 hours, 2 to 3 log cycle reductions in the counts of indicator bacteria, certain bacterial pathogens and viruses are typically obtained. However, the efficiency of mineralisation was strongly influenced by flow-rate and the prevailing temperature. In addition, in the UK, overloading of the treatment system reduced the efficiency of removal of faecal coliforms, probably due to decreased adsorption to biofilms. Faecal coliform counts were also more strongly correlated to BOD than suspended solids. As a secondary treatment process, pathogen removal was consistently better in Egypt than the UK. Although GBH constructed wetlands do not fully satisfy the WHO guidelines for unrestricted irrigation, they can make a significant contribution to the control of pathogens in developing countries.
An assessment of metal removal from highway runoff by a natural wetland
Authors: Mungur A. S. , Shutes R. B. E. , Revitt D. M. , House M. A.
Published: May 2018

Constructed wetlands are increasingly being seen as a viable solution to the treatment of highway runoff. This paper presents a preliminary assessment of the heavy metal removal performance of a natural wetland. The results are compared with the levels found in an adjacent stream which also receives runoff from the same major road. Both subsequently discharge effluent at proximal locations into the Brent Reservoir, a site of special scientific interest in NW London. The concentrations and temporal trends of Cd, Cu, Pb and Zn in the water, sediment and emergent macrophytes of the wetland and stream are discussed with respect to the treatment efficiency of the wetland. Although there is evidence of active metal uptake by the sediment and macrophytes, aqueous metal concentrations generally remain unchanged. The results support the proposal to construct a wetland planted with selected species of macrophyte to treat highway runoff on approximately half the area of the current site.
Iron and manganese release in coal mine drainage wetland microcosms
Authors: Tarutis W. J. , Unz R. F.
Published: May 2018

The primary mechanisms responsible for the removal and retention of iron, manganese, and sulfate in constructed wetlands receiving acidic mine drainage (AMD) include the formation of metal oxides and sulfides within the sediments. This study was initiated to determine the kinetics of metal ion liberation, under reducing conditions, from synthetic and naturally occurring iron and manganese oxides typically found in AMD precipitates. Rates of metal ion liberation were determined during time series incubations of an organic substrate (spent mushroom compost) to which five metal oxides of varying crystallinity (amorphous and crystalline oxides of iron and manganese; natural AMD oxide) were added. All experiments were carried out in silicone-sealed polycarbonate centrifuge tubes incubated at 22°C for a period of 3, 7, 10, 14, 21 or 28 days. Tubes were sacrificed after each incubation period and were analyzed for redox potential, pH, sulfide, and metals. All tubes exhibited reducing potentials within 3 days coupled with rapidly increasing concentrations of iron and manganese. Liberation of iron and manganese decreased with increasing mineral crystallinity (amorphous > natural AMD ≫ crystalline). The results suggest that metal ion liberation from oxide minerals may be an important source of iron and manganese within constructed wetlands receiving AMD.
Structural, dynamic and energetic differences among biotic communities dominated by macrophytes, planktonic algae and cyanobacteria
Authors: Reynolds C. S.
Published: May 2018

Differences in the composition and organisation of three mutually alternative aquatic vegetation types are examined, paying particular attention to the influence exerted through the food webs in regulating the transfer of primary products to the higher trophic levels. Whereas limnoplanktonic communities of open water, whether transferring primary products directly to animals or largely through micro-organisms, are founded upon near-climactic vegetation, shallow margins supporting macrophytes provide a pioneer-stage to terrestrial ecosystems. Small or shallow lakes are entirely ‘marginal’ and are susceptible to dominance by one hydroseral stage or another but with an outcome which depends upon the operating alternative state. These factors change in time or may be altered artificially, to drive the system towards another natural or regulated alternative steady state.
Impact of fishstock manipulation on the composition of net phytoplankton in the rímov reservoir (Czech Republic)
Authors: Komárková J. , Vyhnálek V. , Kubecka J.
Published: May 2018

A ten-year period of monitoring of the Rímov reservoir was chosen to demonstrate the impact of fishstock manipulation on phytoplankton biomass and on species composition of the phytoplankton assemblage. Biomass of planktivorous fish decreased substantially under various forms of biomanipulative pressure. The proportion of large individuals of Daphnia galeata (retained on the 0.71 mm mesh sieve) increased from nearly 0 to 9% of the total zooplankton biomass during the period of 1985-1988 and remained nearly constant during subsequent years. Change in zooplankton structure had no significant response in the abundance of phytoplankton. Species composition of phytoplankton assemblage, however, changed considerably after the large daphnids had reached a biomass of more than 10 mg.m−2 of protein-N. Aphanizomenon flos-aquae var. flos-aquae formed about 8% of phytoplankton biomass before 1985, while its share increased to 40-65% during 1988-1990. Later, Aphanizomenon was replaced by other large forms of algae. The factors possibly influencing Aphanizomenon blooms are discussed with respect to the situation in other water bodies.
Flow and pollutant measurements in a combined sewer system to operate a wastewater treatment plant and its storage tank during storm events
Authors: Bertrand-Krajewski J.-L. , Lefebvre M. , Lefai B. , Audic J.-M.
Published: May 2018

Urban storm drainage is considered using an integrated approach taking into account all parts of the sewer system: pipes, storage tanks, overflows, treatment plant and receiving waters. This paper presents an experimental research in Boran-sur-Oise (France) where continuous measurements are carried out in the combined sewer system (catchment area 61 ha), in the storage tank (245 m3) and in the treatment plant (3000 p.e.). One of the objectives is a comprehensive knowledge of effects of storm events on treatment plant process and efficiency. Catchment, sewer system, storage tank, treatment plant and measurements are described. Results for an autumn rainfall are given as an example. Many impacts on the treatment plant are observed. Despite the load increase compared with dry weather periods, especially for TSS and ammonia, the plant efficiency remains satisfactory. Short-term and long-term impacts are distinguished. New rules for storage tank operation are proposed to avoid hydraulic plant overloading and to use the stormwater solids-settling properties. These rules will be tested in the future to verify their compatibility with receiving water quality requirements. Measurements in upstream sewer system could also be used in the future to operate stormwater treatment systems during storm events.
Origin, resuspension and settling characteristics of solids transported in combined sewage
Authors: Michelbach S.
Published: May 2018

Solids in combined sewage come from different sources. During dry weather flow, organic material will settle in sewer sections having low flow velocities. Microorganisms living from solubles out of dry weather flow are growing at the sewer wall. During low rains, mineral and organic solids from the surface will be washed into the sewer systems and part will settle at the sewer bottom. During storms, all these types of solids will be resuspended and mixed into the complex suspension called “combined sewage”. After five years' research it is apparent that settling velocity is a good instrument for describing sedimentation, transportation and erosion of settleable solids. The knowledge about the transportation of solids in dry weather flow will lead to better design of sewers. During wet weather, another major process for keeping solids back from receiving waters is the settling process. Up to 70% of settleable solids will be settled in a stormwater tank designed after the German guideline A 128. With knowledge of the settling behaviour of combined sewage the design of stormwater tanks could be improved and the receiving waters better protected from sewer pollution.
Analysis of Northern adriatic sea surges
Authors: Manzi D. , Mazzucchelli L.
Published: May 2018

A decision support system for Coastal Resource Management (from now on called CRM) has been developed in the PC-Windows graphic environment. CRM includes the following modules: a 2-D and a 3-D time dependent barotropic numerical model, a two-layer baroclinic model, a diffusion equation solver. Analytic tests have been done both for the 2-D and the 3-D model; in the paper a validation and calibration of the 2-D model is presented using data collected in Northern Adriatic sea (Trieste and Venice).
Influence of sewer sediments on flow friction and shear stress distribution
Authors: Perrusquía Gustavo , Petersen Ole , Larsen Torben
Published: May 2018

Most sewers contain more or less deposited sediments. The paper discusses the distribution of the boundary shear stresses and the hydraulic resistance in part-full sewer pipes with such deposited sediments. The discussion is based on a series of numerical experiments using a validated numerical turbulence model. The results from the numerical model are compared with the sidewall elimination method. The validity of the sidewall elimination method is evaluated.
The nitrogen removal potential of predenitrification systems in sensitive coastal areas
Authors: Görgün E. , Artan N. , Orhon D. , Tasli R.
Published: May 2018

Effective nitrogen removal is now required to protect water quality in sensitive coastal areas. This involves a much more difficult treatment process than for conventional domestic sewage as wastewater quantity and quality exhibits severe fluctuations in touristic zones. Activated sludge is currently the most widely used wastewater treatment and may be upgraded as a predenitrification system for nitrogen removal. Interpretation of nitrification and denitrification kinetics reveal a number of useful correlations between significant parameters such as sludge age, C/N ratio, hydraulic retention time, total influent COD. Nitrogen removal potential of predenitrification may be optimized by careful evaluation of wastewater character and the kinetic correlations.
Influence of oxygen on biofilm growth and potential sulfate reduction in gravity sewer biofilm
Authors: Norsker Niels H. , Nielsen Per H. , Hvitved-Jacobsen Thorkild
Published: May 2018

Under conditions of high organic surface load and high hydraulic shear the influence of bulk water dissolved oxygen (DO) concentration on biofilm oxygen consumption, biofilm growth and sulfate reduction in biofilms was investigated using both domestic wastewater and synthetic glucose - yeast extract medium. The biofilm thickness apparently did not approach a steady-state value; instead biofilm thickness increased linearly until the entire biofilm eventually sloughed.

Potential activity of sulfate-reducing bacteria was highest when the biofilms were grown at low DO levels in bulk water. Potential sulfide production measured per biofilm volume remained fairly constant during the growth of the biofilms. Only at oxygen levels close to 0 ppm was sulfide production into bulk water under aerobic conditions evident; at higher oxygen levels, complete reoxidation of sulfide occurred within the biofilm. For biofilms growing at bulk oxygen conditions below 1 ppm, the sulfate reduction (and thus sulfide production) was of significance for the processes in the biofilm system in terms of oxygen consumption and COD removal.
An evaluation of the efficiency and impact of raw wastewater disinfection with peracetic acid prior to ocean discharge
Authors: Sánchez-Ruiz Concepción , Martínez-Royano Silvia , Tejero-Monzón Iñaki
Published: May 2018

Peracetic acid (PAA) is the active component of a series of disinfectant products developed for the treatment of wastewater. These products have only recently been introduced onto the market so little published information exists about their efficiency. In this work the disinfection efficiency of PAA has been experimentally studied on raw wastewater, along with eventual regrowth after the ocean discharge of the treated water. Great variability has been observed in the inactivation of total coliforms by PAA, the influence of the pH of the wastewater was noteworthy. The disinfection action takes place in short times (around 5 to 10 minutes). After disinfection and mixing with real sea water the total coliforms present greater T90 values and disappearance times, having increased their concentration under laboratory conditions and in darkness.
Aerobic biodegradation and microbial population of a synthetic wastewater in a channel with suspended and attached biomass
Authors: Cao Y. S. , Alaerts G. J.
Published: May 2018

A well mixed indoor recirculating channel was adopted to investigate aerobic heterotrophic biodegradation kinetics and microbial communities in drainage systems with suspended and attached biomass. Experiments were run with synthetic substrate. The biofilm function was distinguished from the suspended biomass by using the Biological Oxygen Monitor (BOM) to measure suspended biomass activity. The microbial community was overall dominated by filaments (mainly Sphaerotilus natans) due to the selection pressure of the soluble organic substrate; the biofilm was surface film-dominated because of the low flow velocity and shear stress. The channel processes were dominated by the biofilm function. However, it was found that the intrinsic Monod kinetic constants were μmax=2.8 d−1, Ks=1.8 mg/l for the suspended biomass, 1.4 d−1, 2.7 mg/l for the biofilm biomass, both at 28°C; and 0.76 d−1, 2.5 mg/l, 0.52 d−1 and 2.9 mg/l respectively for the two types of biomass, both at 200°C. The specific activity of suspended biomass was 50-100% higher than the biofilm biomass, but no significant difference was found between surface and base film biomass. Biofilm oxygen uptake rates (BUR) were around 25 gO2/m2.d at 28°C, 18 gO2/m2.d at 20°C, and velocity dependent. The observed oxygen consumption coefficient of biofilm Yo/s (gO2/ggluc) decreased from 50 to 10% when biofilm surface loading increased from 50 to 300 ggluc/m2.d. The relationship between the biomass population, intrinsic kinetics and biofilm performance is discussed.
Alteration in sewage characteristics upon aging
Authors: Kaijun Wang , Zeeman G. , Lettinga G.
Published: May 2018

To improve the understanding of the nature of sewage changes upon aging during transport or storage, simulation experiments were conducted using batch reactors under a number of well defined conditions, i.e. anaerobic, aerobic and micro-aerophilic at 10°C, 20°C and 30°C. Important characteristics of the studied sewage were the visual appearance, various chemical properties and odour. The effect of temperature on the degradation processes and reaction kinetics of different polluting fractions of the sewage is studied under mainly micro-aerophilic and anaerobic conditions.

The results of non-inoculated batch simulating experiments reveal that micro-aerophilic conditions are suitable for both pre- and post-treatment of sewage, while anaerobic conditions will suffice for pre-treatment. At low temperatures, anaerobic conditions mainly serve for pre-acidification. On the basis of the results obtained, we recommend putting emphasis on further research dealing with on-site and on-line treatment systems, combined with a central wastewater treatment plant. Such processes look attractive in improving the organic removal efficiency and in reduction of operating cost and capital outlay of wastewater treatment systems.
The gully pot as a physical, chemical and biological reactor
Authors: Butler D. , Xiao Y. , Karunaratne S. H. P. G. , Thedchanamoorthy S.
Published: May 2018

The gully pot operates under two distinct regimes: dry weather and wet weather. During dry weather, rapid drops in dissolved oxygen concentration result in the establishment of anaerobic conditions. This leads to the release of oxygen demanding soluble organics, ammonium and possibly sulphides. Complex changes also occur to the phase and bio-availability of a range of heavy metals. Concurrently, some material previously held in suspension in the inflow settles to the base of the pot to form a bed whilst significant amounts of smaller material remain in suspension. The bed formed under the liquor seems to undergo an aging process. In wet weather, incoming runoff rapidly displaces the standing liquor, which can represent a significant fraction of the total flow volume and pollutant load contributing to a first foul flush. The solids trapping efficiency of the pot is high for larger particles, but poor for smaller particles which carry proportionately more of the pollutant load. Organics and smaller solids can be re-entrained, but there is little evidence of large-scale overturning of the bed.
Control of hydrogen sulfide and degradation of organic matter by air injection into a wastewater force main
Authors: Tanaka N. , Takenaka K.
Published: May 2018

In an attempt to establish a method for controlling the generation of hydrogen sulfide in wastewater force mains, we injected air into a force main, measured its effect on the level of hydrogen sulfide and organic matter, and studied pressure loss and the appropriate volume of air to inject. When air was injected, the concentration of dissolved oxygen was 1 mg/l or more at the terminal point of the force main and there was no increase of hydrogen sulfide. An experimental equation for finding the volume of air injection required to inhibit the generation of hydrogen sulfide was established. This method both inhibits the generation of hydrogen sulfide and helps to purify the wastewater. Our study on pressure loss in the two-phase flow of air and liquid confirmed that it is possible to calculate it using previously proposed models.
Effect of clay particles on the behaviour of biofilms formed by Pseudomonas fluorescens
Authors: Vieira M. J. , Melo L. F.
Published: May 2018

This paper presents results obtained with biofilms formed under turbulent flow by a mixed suspension of Pseudomonas fluorescens and kaolin particles and compares them with biofilms formed in the absence of clay particles. The results show that the presence of kaolin particles leads to: higher accumulation of biomass in biofilm systems; higher stability of the biofilms when substrate is suppressed; higher values of the respiratory coefficient of the suspended cell cultures; increase in the mass transfer rates throughout the biofilm thickness. The results suggest that the kaolin particles enhance microbial activity in the biofilm and may cause changes in the physical structure of the biofilm, making it a more strong and open matrix.
The impact of land reclamation on groundwater quality and future drinking water supply in the Netherlands
Authors: Stuyfzand Pieter J.
Published: May 2018

Reclaimed lakes (surface ≥3 m below sea level) in a coastal plain with formerly more or less stagnant flow conditions, act as huge groundwater discharge areas and convert the bordering land into groundwater recharge zones. The main consequences are: (1) the infiltration of fresh polder and river-Rhine water, both of poor quality; (2) the moving in of fresh groundwater of excellent quality, from relatively remote sandy recharge areas like the coastal dunes and Pleistocene uplands; (3) the encroachment of salt North Sea water along the west coast; and (4) the bleeding-out of relict brackish to salt water.

The sluggish change in the spatial distribution of water types, leads to new possibilities of groundwater pumping for public water supply in and around the deep polders, in future. The chemical consequences are discussed. Salinization hazards for well fields in the coastal dunes and Pleistocene uplands may increase.
Kinetic aspects of biofilm formation on surfaces exposed to drinking water
Authors: van der Kooij D. , Vrouwenvelder H. S. , Veenendaal H. R.
Published: May 2018

Biofilm formation in drinking water distribution systems should be limited to prevent the multiplication of undesirable bacteria and other organisms. Certain types of drinking water with an AOC concentration below 10 μg of acetate-C eq/l can support the growth of Aeromonas. Therefore, the effect of acetate at a concentration of 10 μg of C/l on the biofilm formation rate (BFR) of drinking water with a low AOC concentration (3.2 μg C/l) was determined. Drinking water without acetate had a BFR of 3.9 pg ATP/cm2.day, whereas a BFR value of 362 pg ATP/cm2.day was found with acetate added. These data indicate that a low acetate concentration strongly affects biofilm formation, and that only a small fraction of AOC is available for biofilm formation. Aeromonads did not multiply in the biofilm despite their ability to grow at a concentration of 10 μg of acetate-C/l. Further investigations are needed to elucidate the relationship between substrate concentration and biofilm formation in drinking water distribution systems and the growth of undesirable bacteria in these biofilms.
Influence of substrate C/N ratio on the structure of multi-species biofilms consisting of nitrifiers and heterotrophs
Authors: Ohashi Akiyoshi , Viraj de Silva D. G. , Mobarry Bruce , Manem Jacques A. , Stahl David A. , Rittmann Bruce E.
Published: May 2018

A bench-scale biological aerated filter (BAF) was operated under a range of substrate loadings and C/N influent ratios. Start-up with a substrate loading of 4.8 COD kg m−3 d−1 and an influent C/N ratio of 1.5 gave no nitrification, due to the high biofilm detachment rate caused by the daily backwashing. Subsequent runs with lower substrate loadings and backwashing rates allowed stable nitrification. A final run with the initial substrate loading and backwash rate gave stable nitrification. Oligonucleotide probes targeted to the 16S rRNA of the nitrifiers, as well as to other types of microorganisms, were used to characterize how the changes in loading and detachment affected the microbial structure in the biofilms. The proportion of nitrifiers decreased with increasing C/N ratio. The biofilm remaining after backwashing also contained a higher fraction of nitrifiers than did the backwash solids stripped from the outer layers of biofilm, which consisted mainly of active heterotrophs. Thus, stable nitrification was possible only when the nitrifiers became established deeper inside the biofilm.
Fractal structure of biofilms: new tools for investigation of morphology
Authors: Hermanowicz S. W. , Schindler U. , Wilderer P.
Published: May 2018

Fractal dimension was used to describe morphology of a biofilm. Images of biofilm sections were obtained with a confocal laser scanning microscope and were further enhanced using image analysis software. Fractal dimensions were estimated from the slopes of cross-correlation functions. Two geometric scales with different fractal dimensions were identified in the biofilm. Small scale biomass clusters (< 5 μm) had fractal dimensions close to the topological dimension while the fractal dimensions of larger aggregates were considerably smaller. Anisotropic morphology was also detected by the difference of fractal dimensions and was possibly related to the direction of water flow.
Rotterdam for a clean river Meuse
Authors: Klink F. J.
Published: May 2018

Rotterdam is in contact with approximately 20 major dischargers responsible for polluting the Meuse, which is a source of drinking water for Rotterdam. These negotiations must lead to a reduction in the level of pollution in the Meuse. The measured discharges and the calculated percentage reductions are presented. In 1994, the emphasis will be on pollution by pesticides.
Effect of degradation kinetics on the microstructure of anaerobic biogranules
Authors: Fang Herbert H. P. , Ho-Kwong Chui , Yu-You Li
Published: May 2018

The microstructure of anaerobic biogranules treating a wide variety of wastewaters was investigated using light and scanning electron microscopies. Biogranules were sampled from upflow anaerobic sludge blanket (UASB) reactors treating wastewater individually containing formate, acetate, propionate, butyrate, peptone, sucrose, starch, benzoate, brewery and monosodium glutamate. Results indicated that the microstructure of the biogranules was strongly dependent on the degradation kinetics of substrates. Anaerobic degradation is a multi-step process, involving fermentation/acidogenesis, acetogenesis and methanogenesis. For substrates, such as carbohydrates, of which the initial step of degradation was considerably faster than the subsequent degradation of intermediates, biogranules developed a layered microstructure. On the other hand, for substrates, such as proteins, of which the initial step of degradation was rate-limiting, a uniform microstructure would be developed. These findings are of significance for the development of kinetic models for biogranule and biofilm.
Restoration of our lakes and rivers with wetlands – an important application of ecological engineering
Authors: Mitsch William J.
Published: May 2018

The role of wetlands, both natural and man-made, in improving water quality of streams, rivers, and lakes is illustrated with examples of fringe, instream, and riparian wetlands. Fringe wetlands have been shown to reduce inputs to freshwater lakes, instream wetlands can improve habitat and provide some water quality function to small streams, and riparian wetlands along larger rivers provide important roles in both capturing sediments and nutrients from the river itself and serving as buffer between uplands and the river. Two major experimental riparian wetland sites in Midwestern USA are introduced: The Des Plaines River Wetland Demonstration Project and the Olentangy River Wetland Research Park.
Nature on the move – towards large-scale water system and nature development in the Netherlands
Authors: de Vriend M. C. , Iedema C. W.
Published: May 2018

The potential for developing and restoring natural assets in large-scale water systems in The Netherlands is investigated. Maximizing the natural qualities of The Netherlands means giving full play to the dynamics of wind, water and sediments. Within the limits set by safety, shipping and drinking water supplies, there appear to be numerous opportunities to restore dynamics and create sustainable nature. Ecological engineering, which concentrates on restoring natural physical processes, is linked to nature policy goals in terms of processes, habitats and species. Essential abiotic mechanisms can be identified. Three examples of projects in characteristic Dutch ecosystems (rivers, down stream freshwater lakes and estuaries) illustrate both the prospects for nature and the feasibility of combining uses with nature development. The Grensmaas-case combines gravel extraction, flood protection and natural development of a rain-fed river. The case on Lake IJssel shows the importance of “natural” water level fluctuations in an “artificially” created freshwater lake. The Western Scheldt provides an interesting case for combining the economic interests of shipping with the ecological interests of the estuary by returning arable land to the sea.
Optimal operation of a reservoir for quality control using inflows and outflows
Authors: Nandalal K. D. W. , Bogardi Janos J.
Published: May 2018

This paper presents two optimization models developed for the derivation of operation policies for a reservoir when the quality considerations are important besides satisfying the quantity requirement. In one model only the releases are controlled. In the other model both inflows and releases are controlled. Reservoir operational policy is based on the Incremental Dynamic Programming technique. Complete mixing is assumed to be occurring in the reservoir throughout the year. The models are applied to a reservoir on the Shapur river in Southern Iran. The results obtained from the models show their potential in improving the quality of water supplied from a reservoir. The improvements obtained by manipulating both inflows and releases are observed to be higher than the ones achieved by simple release control.
PCLAKE: a modelling tool for the evaluation of lake restoration scenarios
Authors: Janse Jan H. , van Liere Louis
Published: May 2018

The response of various water quality parameters on nutrient load reduction in shallow lakes is often non-linear, because of the many different ecological interactions involved. In order to get insight into this, a mathematical model is presented combining a description of the internal nutrient cycles with a food-web approach. Different applications of the model are discussed: combined calibration on a multi-lake data set, and a study on the effects of increasing vs. decreasing loading on the water quality in an “average shallow lake”. The model has also been used to evaluate different restoration scenarios in several lakes in The Netherlands.