bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of storage on kinetic selection to control aerobic filamentous bulking
Authors: Majone M. , Massanisso P. , Carucci A. , Lindrea K. , Tandoi V.
Published: May 2018

In various activated sludge systems, sludge grows under transient (unbalanced) conditions and storage of internal polymers becomes important. Differences in storage capacity under transients are often used to explain kinetic control of bulking, but storage is neither studied in detail nor usually included in modelling. For this reason, the transient response of different aerobic mixed cultures was studied by experimentally determining the role of storage. Two different mixed cultures (bulking and non-bulking) were selected in an acetate-limited medium, by continuous or intermittent feeding of a CSTR, respectively. Batch tests were used to investigate the transient response of the selected cultures as a function of the starvation time and of the ratio of the initial concentration of the substrate and sludge biomass (So/Xo). In most experimental conditions, both cultures showed that the storage of poly-hydroxybutyrate (PHB) is in general the prevailing mechanism of substrate removal. In particular, the culture dominated by floc-formers showed very fast response to the substrate spike with a high observed yield. Storage was practically the only metabolism occurring. The ratio So/Xo did not have a major role in determining the type and extent of the response. Starvation did not affect the response of the floc-formers to transient conditions. For the filamentous bacteria, both the growth response and, even more significantly, the storage response were negatively affected. Hence, the difference in storage capacity between filamentous and floc-forming bacteria was further increased.
Biodegradation of p-toluenesulphonic acid by comamonas testosteroni in an aerobic counter-current structured packing biofilm reactor
Authors: Khlebnikov Artem , Péringer Paul
Published: May 2018

p-Toluenesulphonic acid degradation by Comamonas testosteroni was studied in a continuously operated fixed-bed biofilm reactor. Static mixer elements (Sulzer Chemtech, Switzerland) were used as a support matrix for biofilm formation. Degradation of p-toluenesulfonate was investigated at several aeration (0.5–4 L min−1) and dilution (0.15–0.4 h−1) rates under septic conditions. The maximum observed pollutant degradation rate was 198 mg of C L−1 h−1. In spite of nonsterile conditions, a very limited range of microbial species was present in the reactor. The system was operated for over 3 months and Comamonas testosteroni used as inoculum was largely present in the biofilm (about 60% of the total microbial population) during the whole cultivation period. Two other aerobic bacterial strains detected in the biofilm were not able to degrade p-toluenesulphonic acid. High biomass attachment was observed on polypropylene static mixers. Immobilised biomass reached the level of 10.4 g of dry weight per m2 of the support and 23% of its structure was active biomass.
New strategies for estimating kinetic parameters in anaerobic wastewater treatment plants
Authors: Merkel Wolf , Schwarz Alexander , Fritz Sebastian , Reuss Matthias , Krauth Karlheinz
Published: May 2018

Approaches to mathematical modelling of anaerobic digestion and criteria for reactor design in anaerobic wastewater treatment are based on biological degradation kinetics. Whatever type of kinetics is used, the crucial problem always is reliable parameter estimation. For Monod-type kinetics a concept based on batch and fed-batch techniques is presented, which allows accurate estimation of kinetic parameters Vmax and KS in short-time experiments. Following the method of Optimal Experimental Design, sensitivity analysis is applied to design fed-batch experiments. The paper presents the methodology and results for the anaerobic degradation of acetic acid and discusses further implications of the experimental strategy.
Effect of decarbonation on alkaline reduction in two-phase UASB process
Authors: Nishimura Sosuke , Yoda Motoyuki
Published: May 2018

Methods for reducing the alkaline dosage in a two-phase UASB process were investigated. An alkaline simulation model was developed incorporating the recycle ratio of effluent, the mass transfer rate of carbon dioxide from the liquid to gas phase, and the dissociation of organic acids and carbonate. Model simulation showed that a considerable amount of alkaline was consumed needlessly in an attempt to neutralize bicarbonate generated in both the acidification phase and methanogenic phase. Decarbonation by bubbling air between the acidification section and UASB reactor was shown to be effective in reducing the amount of alkaline required for bicarbonate neutralization. Methanogenic bacteria in the system were not adversely affected by air bubbling during four months of continuous laboratory-scale operation.
Axo-dye biodegradation under anoxic conditions
Authors: Zissi U. , Lyberatos G.
Published: May 2018

Biological oxidation of azo-dyes is important for wastewater treatment. Azo-dyes are synthetic organic colorants that exhibit great structural variety. A large majority of these dyes are released into the environment. The textile industry and dyestuff manufacturing industry are two major sources of released azodyes. In the present study, we focus on the anoxic degradation of a disperse azo-dye, p-aminoazobenzene (pAAB), a simple azo-dye, by a pure culture of Bacillus subtilis, growing on a synthetic medium. Bacillus subtilis is a bacterium capable of using nitrate and/or nitrite as terminal electron acceptor under anoxic conditions. This bacterium lacks the capability for fermentation. The degradation of p-aminoazobenzene by Bacillus subtilis was examined through batch experiments in order to elucidate the mechanism of dye degradation. The results proved that Bacillus subtilis co-metabolizes p-aminoazobenzene under denitrifying conditions, in the presence of glucose as carbon source, producing aniline and p-phenylenediamine as the nitrogen-nitrogen double bond is broken.
Sediment pore water toxicity testing
Authors: Heida Henk , van der Oost Ron
Published: May 2018

The toxicity of the pore water from the sediments of nine fresh water systems in and around Amsterdam City was studied with the aid of four acute toxicity tests. Based on preliminary chemical analysis, the sediments of three of the tested systems had to be considered strongly contaminated, according to the quality standards derived from the Dutch Law on Soil Pollution Control. In addition, the acute toxicity of groundwater from a heavily contaminated industrial building site was also examined. The following toxicity tests were used.

1. Microtox bioluminescence assay, or Microtox test. This test is based on the inhibition of bioluminescence of Photobacterium phosphoreum; 2. Rotoxkit F, based on the LC50 of Brachionus calyciflorus; 3. Thamnotoxkit F, based on the LC50 of Thamnocephalus plaxyurus; 4. Toxichromotest, based on the inhibition of β-galactosidase formation in Escherichia coli. The objective of the study was to test the feasibility of the toxicity tests as a tool for the risk evaluation of contaminated sites, both in water and on land. The results indicated that the sediments of three of the eight sites studied could be classified as toxic and one site even as very toxic. The outcome of the toxicity testing confirmed the results of the chemical analysis for only one site. It appeared that the Microtox and the Thamnotoxkit F tests were the most sensitive acute toxicity tests.

It could be concluded that the resolution of the toxicity tests scrutinized was insufficient to reliably discriminate the environmental quality of the sediments at the locations studied. The bioassays, however, are useful in determining remediation priorities of contaminated sites.
Biofilms in freshwater ecosystems and their use as a pollutant monitor
Authors: Fuchs S. , Haritopoulou T. , Wilhelmi M.
Published: May 2018

A simple biofilm sampling device is used to collect representative microcoenoses from the River Alb in Germany. The samples are analyzed for their copper, cadmium and lead contents and the results are shown to be comparable to those from the techniques.
DNA damage as a biomarker of marine pollution: strand breaks in seastars (Asterias rubens) from the North Sea
Authors: Everaarts J. M. , Sarkar A.
Published: May 2018

The DNA damage in seastars (Asterias rubens) was studied by measuring the level of integrity of DNA isolated from pyloric caeca of the organisms in order to assess the state of pollution of the North Sea. The effect of various genotoxic chemicals on the integrity of DNA was determined by the level of double strandedness with respect to total DNA following time-dependent partial alkaline unwinding assay. On the basis of the level of integrity of DNA from seastars the study area was distinguished into three clusters: Cluster-I, the highly polluted area (coastal and estuarine zones) with low integrity of DNA (27-43% integrity), Cluster-II, the moderately polluted area (offshore region) with medium integrity of DNA (49-64% integrity) and Cluster-III, less polluted area (near Dogger bank region) with high integrity of DNA (70-87% integrity).
Rapid enzymatic detection of faecal pollution
Authors: Davies Cheryl M. , Apte Simon C.
Published: May 2018

Fields trials were carried out using a 1-hour fluorimetric assay of β-D-galactosidase activity alongside conventional membrane filtration to detect faecal coliforms in beachwater samples. The ultimate aim of the study was to test the reliability of the assay with a view to its use in the field to assess the compliance of coastal bathing waters with the guideline concentrations. The assay had a 99% success rate at detecting pass/fail at 300 faecal coliforms per 100 ml, using a threshold fluorescence of 60.3 nM. A good correlation (r=0.90) between faecal coliform concentration and fluorescence assay results was obtained. The assay provides a rapid, simple and inexpensive method for the detection of sewage pollution in marine waters, and with the aid of portable instrumentation, it may be performed in the field, allowing real time monitoring of water quality.
Mineralization enhancement of non-aqueous phase and soil-bound PCB using biosurfactant
Authors: Robinson Kevin G. , Ghosh Mriganka M. , Shi Zhou
Published: May 2018

Batch studies were conducted to evaluate the impact of biosurfactant (Rhamnolipid R1) on microbial utilization of radiolabeled 4,4′ chlorobiphenyl (4,4′CB). Production of 14CO2, after addition of an acclimated bacterial culture (Alcaligenes eutrophus), was monitored to determine the extent and rate of mineralization. Bioavailability of non-aqueous and soil-bound phases upon biosurfactant treatment was evaluated. Addition of Rhamnolipid R1 elevated both the rate and extent of 4,4′CB mineralization; however, enhancement was pronounced only at biosurfactant concentrations above the critical micelle concentration (CMC). For a biosurfactant concentration of 4.0 g/L, the average mineralization rate of 4,4′CB was 45 times that measured in controls (no biosurfactant). The extent of 4,4′CB mineralization in the presence of 4.0 g/L biosurfactant increased by a factor of 213 over biotic controls. Elevated mineralization was due, in part, to aqueous solubility enhancement of the test compound in the presence of biosurfactant. The total mass of 4,4′CB mineralized in biosurfactant solutions exceeded the total initial mass of 4,4′CB dissolved in biosurfactant free solutions, which confirmed that micellized 4,4′CB was biodegradable. Co-mineralization of biosurfactant was at a minimum during periods of high 4,4′CB mineralization. The results of this research provide clear evidence that biosurfactant addition followed by pure culture biological treatment is a promising approach for treatment of non-aqueous phase and soil-bound PCBs.
Technologies for wastewater treatment appropriate for reuse: potential for applications in Greece
Authors: Tchobanoglous George , Angelakis Andreas N.
Published: May 2018

During the past 15 years, a wide variety of technologies have been developed that can be used for the treatment of wastewater for reuse applications. To assess the need for alternative technologies, potential reuse applications are reviewed. Changes in wastewater management, including the growing importance of decentralized wastewater management, is examined. The role of decentralized wastewater management is considered with respect to wastewater treatment, reclamation, and reuse. Technologies are presented and discussed for a wide range of reuse applications, ranging from individual homes to large centralized systems. The performance of representative technologies is assessed. A brief review of the water resources of Greece is presented to provide some perspective on the potential for wastewater reclamation and reuse in Greece.
Improvement of effluent quality for reuse in a dairy farm
Authors: Hamoda Mohamed F. , Al-Awadi Saed M.
Published: May 2018

This study examined the chemical treatment of wastewaters from a dairy farm in order to improve effluent quality and evaluated the reuse of treated effluent in irrigation. An extensive sampling and analysis program was conducted over a period of one year to determine wastewater characteristics at the plant. It has been found that the wastewater COD, BOD, solids, nitrogen and phosphorus content are relatively high but daily variations in pollution loads are not considerably high. Waste treatment in primary settling tanks was found to be insufficient since the effluent quality cannot satisfy the requirements set by the municipal. Experimental results on chemical treatment using alum as a coagulant indicated that the wastewater pollutants could be effectively reduced in order to obtain a good effluent for reuse in irrigation. A wastewater treatment system has been proposed based on the results of the industrial waste survey, evaluation of the existing treatment, and analysis of the jar tests on chemical treatment. The proposed system can be implemented to produce a good quality effluent for beneficial reuse in irrigation of farm land.
Management modeling of integrative wastewater treatment and reuse systems
Authors: Oron Gideon
Published: May 2018

An integrative approach for wastewater treatment and reuse projects is exemplified. The approach is based on management modeling for optimal wastewater treatment, disposal and reuse. Management modeling takes into account regional and national aspects. These considerations include treatment levels and control, water supply and demand, transportation and storage requirements, technical capabilities and social issues. Attention is also given to environmental pollution and health risks aspects and purpose of wastewater application. The model is based on defining an objective (cost) function to be optimized. The optimum of the objective function is evaluated subject to a series of technological, social, health and environmental constraints. The results provide information regarding the system layout and related optimal investment and operational expenses.
Selective removal and recovery of phosphate in a novel fixed-bed process
Authors: Zhao Dongye , Sengupta Arup K.
Published: May 2018

This paper reports salient features of a new fixed-bed sorption process in regard to ultimate removal and recovery of phosphate from municipal and industrial wastewater. The sorbent, referred to as polymeric ligand exchanger(PLE), is essentially a copper(II) loaded specialty chelating polymer. Laboratory experiments have demonstrated that the PLE: can remove phosphate selectively from municipal and synthetic wastewater; is amenable to efficient regeneration; and provides opportunities to recover phosphate and reuse the spent regenerant for multiple numbers of cycles.
Effect of effluent quality and temperature on the persistence of viruses in soil
Authors: Blanc Remy , Nasser Abid
Published: May 2018

Survival and adsorption of pathogenic viruses in soil material can effect the extent of groundwater pollution by the application of wastewater effluents to soil. This study was conducted to determine the effect of soil composition and wastewater quality on the adsorption of pathogenic viruses (hepatitis A virus and poliovirus 1) and model bacteriophages onto soil. Moreover, the effect of temperature, soil composition and water quality on the die-off of pathogenic viruses and model bacteriophages was also studied. The effect of water quality on virus adsorption to soil was virus type dependant. Poliovirus 1 adsorption was the highest regardless of water type, whereas the poorest adsorption was observed for MS2 bacteriophage. Intermediate adsorption rates were observed for PRD-1 bacteriophage. No die-off was observed for any one of the studied viruses (HAV, poliol, MS2 and PRD-1) after 20 days incubation in soil saturated with secondary/tertiary treated wastewater at 10°C. At 23°C, the greatest die-off was observed for MS2 bacteriophage, which was incubated in soil saturated with secondary and tertiary treated effluents. Intermediate die-off was observed for poliovirus 1, whereas negligible die-off was observed for HAV and PRD-1 bacteriophages. This indicates that pathogenic viruses can survive for long period of time in soil at ambient temperatures. Our results indicate that polio 1 and MS2 bacteriophage can not be used as models for the persistence of pathogenic viruses such as HAV in soil. PRD-1 bacteriophage has been found to be more suitable than MS2 to predict the persistence of pathogenic viruses especially at ambient temperatures.
Environmental considerations for wastewater reuse in agriculture
Authors: Al Salem Saqer S.
Published: May 2018

The water demand in the Middle East is growing very rapidly. The portion of the quantity of the potable water is increasing on the account of the irrigation water and most of the countries will face water deficiency. A reliable way to secure the required water for irrigation is by collecting and reclaiming each drop of water used in the cities to be reused. To guarantee and safeguard hygienic standards and have no adverse effects on the environment must be given the highest priority. The paper discusses in detail the pollutants, their effect, and their way of influence. The on-site reuse and its advantages and the aspects that must be evaluated to decide the suitability of treated water were presented besides appropriate treatment for wastewater reuse and its guidelines. The Jordanian experience in the field of wastewater reuse in agriculture is discussed, and the socioeconomic benefits to community are illustrated.
Reuse of treated sewage effluent for cooling water make up: a feasibility study and a pilot plant study
Authors: Wijesinghe Bandupala , Kaye Ralph B. , Fell Cristopher Jospeh D.
Published: May 2018

This investigation was aimed at developing an acceptable technology for using secondary effluent as cooling water makeup for inland manufacturing industry in Australia. Approximate economic evaluations were made for a number of pretreatment alternatives and for internal treatment with chemical conditioning agents. Internal treatment with biocide dosing appeared to be the most promising option. A portable pilot plant scale cooling tower/heat exchanger unit was constructed. The unit incorporated an on-line, differential pressure biofilm monitor together with automated control and data acquisition systems. The pilot plant was installed on site at a sewage treatment plant near Sydney. It was demonstrated that the use of TSE for cooling water makeup is technically feasible. The rate of biofilm growth observed using chlorinated secondary effluent directly from the sewage treatment plant as makeup water was similar to the rate of biofilm growth observed when potable water was used and supplementary chemical treatment was not introduced in either case. Excellent control of biofilm growth was observed in subsequent experiments when supplementary additions of simple chlorine or bromine chloride treatment systems were carried out. The pilot plant was operated successfully at 5 cycles of concentration without any other supplementary treatment being required.
Effect of soil type on water quality improvement during soil aquifer treatment
Authors: Quanrud David M. , Arnold Robert G. , Wilson L. Gray , Conklin Martha H.
Published: May 2018

Bench-scale soil column experiments were performed at The University of Arizona to examine the effects of soil type and infiltration rate on the removal of wastewater organics during soil aquifer treatment (SAT). The suitability of such waters for potable uses following a combination of above-ground treatments and SAT polishing was under investigation. SAT was simulated in 1-meter soil columns containing repacked homogenized soils ranging from poorly graded sands to silty sands. Soils were obtained from existing and potential effluent recharge sites in Arizona. All columns received chlorinated/dechlorinated secondary effluent, ponded to a 25-cm depth above the soil surface, under alternating wet/dry conditions. Treatment efficiencies in biologically active and inhibited columns were compared to determine the mechanism(s) of water quality improvements and the sustainability of SAT. Water quality parameters included: (i) non-purgable dissolved organic carbon and (ii) UV absorbance at 254 nm (used as a measure of disinfection-by-product precursors). Differences in through-column removal of non-purgable dissolved organic carbon were significant for columns containing sandy loam (56%), sand (48%) and silty sand (44%). Removal of UV-absorbing organics was not significantly different for columns containing sand and sandy loam (22 and 20%, respectively). There was no significant correlation between infiltration rate and removal efficiency of either organic parameter for both soils.
Control of nitrification efficiency in a new biofilm reactor
Authors: Lazarova V. , Nogueira R. , Manem J. , Melo L.
Published: May 2018

The study of the nitrification capacity of a new gas-lift circulating bed reactor (CBR) carried out with laboratory and industrial scale prototypes, showed a high nitrification rate (1.2-2 kgN m−3 d−1) without any nitrite accumulation. A good nitrification performance 0.5-0.6 kgN m−3 d−1 was maintained even when the CODs/N-NH4 ratio was increased up to 1.8-3.4 (laboratory CBR) and 4-10 (industrial prototype). The comparison of the apparent and intrinsic kinetics indicates that the CBR ensures high specific nitrification rates close to the maximum value. These results indicate an effective control of the attached biomass growth and activity in this type of bioreactor.

The intrinsic kinetics and diffusion limitations were studied by respirometric tests. It was demonstrated that apparent kinetics are zero-order for bulk concentrations of ammonia above 2 mgN l−1 and half-order for lower substrate concentrations. The diffusivity values calculated using the half-order diffusion-reaction model are in the range of 1.09 × 10−9 to 1.58 × 10−9 m2 s−1 for ammonia nitrogen and of 1.1 × 10−9 to 1.37 × 10−9 m2 s−1 for nitrite within the range of temperature studied (16-28°C). The application of the diffusion-reaction model requires a very precise determination of the biofilm thickness or density. In the case of biofilms developed in heterogeneous granular surfaces, new methods have to be developed for the best estimation of the biofilm density and active cells distribution.

In conclusion it can be stated that this new three-phase bioreactor ensures a high nitrification rate and enhanced process stability through an effective biofilm control. The CBR is a good tool for more fundamental studies of biofilm kinetics and activity thanks to the homogeneous distribution of the fixed biomass in the reactor.
Hydrolysis and degradation of filtrated organic particulates in a biofilm reactor under anoxic and aerobic conditions
Authors: Janning K. F. , Mesterton K. , Harremoës P.
Published: May 2018

Two experiments were performed in order to investigate the anoxic and the aerobic degradation of filtrated organic matter in a biofilter. In submerged lab. scale reactors with Biocarbone media as filter material, accumulated particulate organic matter from pre-settled wastewater served as the only carbon source for anoxic and aerobic degradation respectively. In order to utilise the accumulated organic matter, the bacteria in the biofilm had to produce extracellular hydrolytic enzymes for the hydrolysis process. In the first experiment with anoxic degradation, a significant denitrification occurred. The maximum nitrate removal rate, with particulate organic matter as carbon source, was found to 1 g NO3-N/ (m2d), declining exponentially as rA.NO3-N = 1.04 e −4t g NO3-N/(m2d) (t = days). A significant release of soluble organic matter (< 0.45 μm) and production of inorganic carbon to the bulk liquid was observed as an indication of hydrolysis taking place. The second experiment was designed as a series of on-line OUR batch experiments in a biofilm reactor with recirculation, in order to investigate further the degradation of particulate organic matter. After the biofilm had been starved in order to remove the original organic matter, particulate organic matter was added and the degradation kinetics recorded. The initial removal rate was high, rA.02 = 2.1 g O2/(m2d) though fast declining towards endogenous respiration. The respiration ratio between removed oxygen and produced carbon dioxide was declining from 1.3 to 1.0 g O2/g CO2 during the degradation of organic particulates. The respiration ratio during endogenous respiration was determined to be 0.7 g O2/g CO2 indicating a thorough mineralisation of biomass.
How to evaluate photochemical methods for water treatment
Authors: Braun André M. , Oliveros E.
Published: May 2018

Photochemical advanced oxidation processes (AOPs) generally imply generation of hydroxyl radicals which are initiating the oxidative degradation by well defined reactions (hydrogen abstraction, addition and electron transfer) with available organic substrates. This limitation of the scope of applications may be avoided in implementing combinations of different photochemical and/or thermal processes. A simple evaluation of photochemical AOPs is based on the absorption spectrum of the oxidant to be added and on the spectral distribution of the emission of commercially available light sources. Dominating light absorption, in particular in the UV-C spectral domain, by the solutes of the aqueous system to be treated may lead to exclude some of the degradation processes, as excitation of the oxidant and, consequently, production of the initiator become inefficient with increasing inner filter effects.

The evaluation of photochemical AOPs in terms of volume independent rates is convenient and highly advocated, but such comparisons should only be made for processes applied to a restricted number of model substrates which are to be degraded in optimized equipment. Taking into account the volume independent rates determined in the range of realistic pollutant concentrations, the number of m3 of contaminated water of known pollutant nature and concentration to be treated per unit of time, the list of a commercially available light sources and their geometry, a final selection of the degradation process or of a combination of processes may be made, and the total electrical energy required and the number of photochemical reactors to be built may be calculated.
A conceptual view of floc structure in the sweep floc domain
Authors: Bache D. H. , Johnson C. , McGilligan J. F. , Rasool E.
Published: May 2018

Using a model suspension of rice starch granules coagulated with alum, the paper describes an experimental investigation into the factors which control strength by the sweep floc mechanism. Electron micrographs, backed by electrophoresis measurements, indicated that the precipitate exists both as a positively charged adhesive coating and also in a mobile state, possibly similar to ‘free’ precipitate without significant charge. A comparison of strength measurements on flocs derived from rice starch with those based on low charged latex particles, led to the conclusion that coulombic attraction between the primary charges and shared coating in the form of an electrostatic bridge was the dominant bonding mechanism when the primary charge was significant. Rheological measurement on a suspension of the ‘free’ precipitate at a concentration likely to be encountered within the floc showed that it behaved as a Bingham plastic i.e with an identifiable yield stress at zero shear and contributes to cohesion. It is suggested that floc strength depends on an interplay between these two binding mechanisms, overdosing reducing electrostatic bridging and tending towards the weaker cohesion of the internal gel.
Collision efficiency factor in brownian coagulation (αBr) including hydrodynamics and interparticle forces
Authors: Mooyoung Han , Hyungki Lee , Lawler Desmond F. , Sangil Choi
Published: May 2018

In order to realistically model the behavior of Brownian particles in water, collision efficiency factor in Brownian coagulation (αBr) should be included. αBr is calculated by solving the diffusion equation including the detailed mathematical description of hydrodynamics and interparticle forces. αBr is found to be a function of several parameters: particle size and ratio, Hamaker constant, ionic strength of liquid, surface potential of particle. Ionic strength and surface potential significantly affect αBr. The graphical plane of ionic strength and surface potential is divided into two regions by a curve: above this curve, no coagulation is expected, however, below this curve, coagulation is expected. αBr values in this region are the same as those predicted for no electric repulsion. The model qualitatively explains the change of coagulation efficiency at estuary or water treatment plant. Better prediction of suspensions at both stabilized and destabilized system can be made possible incorporating the collision efficiency factors of the other coagulant mechanisms such as differential sedimentation and fluid shear.
The role of particle size and density in dissolved air flotation and sedimentation
Authors: Vlaški A. , van Breemen A. N. , Alaerts G. J.
Published: May 2018

Conventional (sedimentation) and advanced (dissolved air flotation) treatment were studied in the context of removal of the single cells form of the cyanobacteria Microcystis aeruginosa. This cyanobacterium species is recognised as an ideal surrogate for process removal efficiency assessment of particles of the problematic size range (3-10 m). The agglomeration (coagulation/flocculation) phase has been indicated as essential and determining the down-stream process efficiency, hence it is a prerequisite for process improvement. Relevant process parameters have been addressed on a laboratory (model water) and pilot plant (reservoir water) scale, including the influence of coagulant (FeCl3) dose, coagulation pH, flocculation time, energy input (G value), single stage versus tapered flocculation and application of cationic polymer as coagulant aid. The process efficiency was assessed as a function of the preceeding agglomeration (coagulation/flocculation) phase and the obtained particle (floc) size distributions. The particle (floc) size - density relationship was addressed in the context of more accurate process kinetic modelling.
Particle separation, solids budgets and headloss development in different biofilters
Authors: Boller Markus , Kobler Daniel , Koch Gerhard
Published: May 2018

Biofilters for secondary treatment, tertiary nitrification and tertiary denitrification were investigated with regard to solids and gas accumulation. Biomass growth, solids capture by filtration and gas entrapment were quantified for the three different applications. In biofilters for COD-removal or denitrification heterotrophic growth dominates solids accumulation. In tertiary nitrifying biofilters the biomass remaining attached to the media after backwash and suspended solids deposits are the main fractions responsible for filter clogging. Depth profiles of solids accumulation indicate that top layers cause the main headloss in biofilters. As a consequence of solids accumulation increasing gas entrapment in countercurrent and denitrifying biofilters lead to a sudden headloss increase and terminate the filter runs.
Phosphate and ammonium removal by constructed wetlands with horizontal subsurface flow, using shale as a substrate
Authors: Drizo A. , Frost C. A. , Smith K. A. , Grace J.
Published: May 2018

The objective was to investigate the performance of constructed wetlands with horizontal subsurface flow, using shale as a substrate, in removal of phosphate (P) and ammonium (N) from sewage. Shale was selected on the basis of its physico-chemical properties and its potential for P removal, investigated in an earlier study. A laboratory-scale constructed wetland system (CWS) employing horizontal subsurface flow was set up in a greenhouse, with and without Phragmites australis (reeds), and its capacity for simultaneous phosphate and ammonium removal from a synthetic sewage was monitored over a period of ten months. Both the planted and unplanted systems showed an extremely high P removal of 98–100% over the whole period of investigation. Ammonium N was also completely removed in the planted tanks, whereas in the unplanted ones the rates of removal varied between 40 and 75%; removal of nitrate N varied between 85 and 95% in planted and between 45 and 75% in unplanted tanks. pH, Eh and temperature did not differ significantly among planted and unplanted tanks, but the inlet Eh was correlated with P removal (r2 = 0.73; p < 0.05). The presence of Phragmites australis contributed significantly (p < 0.05) to P and N removal. In addition the plants showed excellent growth (up to 2 m in the first year), with good root and rhizome development, and showed potential for heavy metal removal. It was concluded that the shale-based system (which uses a readily available material) shows promise as a substrate for constructed wetland systems.
Soil clogging phenomena in constructed wetlands with subsurface flow
Authors: Blazejewski Ryszard , Murat-Blazejewska Sadzide
Published: May 2018

The paper presents a short description of soil clogging processes during sewage infiltration as well as a simple theoretical model of sand clogging by suspended solids. The Kozeny-Carman equation was used to investigate the influence of the decreasing porosity due to clogging on the sand permeability. A comparison of the results obtained using the derived theoretical relationships with empirical data showed an acceptable agreement.
Numerical models in water quality management: a case study for the Yamuna river (India)
Authors: Kazmi Absar Ahmad , Hansen Ian Sehested
Published: May 2018

In this study attempts are done to apply the Mike 11 numerical water quality model for the evaluation of existing water quality conditions and a prediction of effects of different wastewater and other pollution control schemes under the Yamuna Action Plan. The Mawi-Delhi (Okhla Barrage) stretch has been taken for this study. From the application of model it was found out that water quality between Mawi-Wazirabad reach is significantly affected by the large growth of phytoplanktons causes 80 % to 135 % DO saturation, while in Delhi the quality is so bad that photosynthesis processes are absent. BOD removal mainly takes place by settling of organic matter. The calibrated model is subsequently applied for predicting the water quality for the waste load reduction schemes of the Yamuna Action Plan. It was found out that the water quality of the river in upstream of Delhi would be increased form class B (BOD<3mg/L) to class A (BOD<2mg/L), while for Delhi segment water quality improved considerably but still would be poor, not even to the class D. By the application of certain suggested DO control technologies along with the Action Plan, the water quality will improve to class D (BOD<6 mg/L), so that it can be use for wildlife and fisheries. Additional flow of 40 m3/s (total flow 60 m3/s) can also increase the water quality to the class D.
Use of optimization models in river basin water quality planning
Authors: Somlyódy Làszló
Published: May 2018

A literature review on water quality management optimization models is presented. They include linear and non-linear approaches, deterministic and stochastic methods, as well as multi-criteria decision techniques. Two river basin decision support systems, DESERT and STREAMPLAN developed recently at the International Institute of Applied Systems Analysis, (IIASA) are outlined. The usage of these tools is illustrated by results obtained for three river basins located in Central and Eastern European countries. Examples incorporate least-cost DO policies, regional strategies to reduce nutrient emissions with special regard to the control of inland sea eutrophication, multi-criteria decision making and the sequential usage of optimization and simulation models to assess the sensitivity of a particular policy in terms of water quality and economic impacts. Major features of available optimization models are classified. Reasons of their rare real life applications and associated barriers are evaluated, primarily the nature of legislation and related institutional structures. Finally, a future outlook is presented.
A feasibility study of Melaleuca trees for use in constructed wetlands in subtropical Australia
Authors: Bolton Keith G. E. , Greenway Margaret
Published: May 2018

Three tree species from the genus Melaleuca are being examined for use in constructed wetlands in subtropical SE Queensland, Australia. Growth responses of Melaleuca to secondary treated effluent (100% - approximately 5mgPL−1 and 8mgNL−1), half strength (50%), P enriched (+P) and N enriched (+N) secondary treated effluents were monitored in a 2 year pot trial. A growth index was derived from measurements of height, girth diameter, branch number and new leaf number. Highest rates of growth were achieved in the +N and 100% treatments, and lowest rates in the +P and 50% treatments. Seasonal growth trends were evident. Continuously waterlogged trees had slightly higher growth rates than those subjected to aeration cycles, demonstrating their suitability to wetland environments. An aerated network through the bark extending to the roots may provide a mechanism of root aeration. Biomass and nutrient partitioning were measured in an experimental constructed Melaleuca wetlands receiving pure effluent. Biomass nutrient accumulation rates were comparable to studies of other macrophytes. M. alternifolia stored approximately three times more N and P than M. quinquenervia. However, M. quinquenervia had higher rates of litter fall induced by severe insect damage, increasing the rate of transfer of nutrients to the long term sediment sink. P concentrations in the senescent leaves were highly responsive to external concentrations, and may be used as an indicator of P loading rates in constructed wetlands. Since senescent leaves provide a major pathway of biomass nutrients into the sediment sink, this provides a self regulating P storage mechanism.
Dynamical modelling of an anaerobic digestion fluidized bed reactor
Authors: Bonnet Benjamin , Dochain Denis , Steyer Jean-Philippe
Published: May 2018

One of the main difficulties in modelling a Fluidized Bed Biofilm Reactor (FBBR) is to take into account hydraulic phenomena (such as bed expansion) and its interactions with the biological variables. In this paper, we shall present a dynamical model of the process, analyse the stability of the hydrodynamics and illustrate its performances in simulation. A key feature of the model is that it combines mass balance of the process components with momentum balance equations in order to emphasise the different hydrodynamics of the liquid phase and of the solid phase, and the interactions between both phases. The model derivation finally leads to a set of partial differential equations (PDE). This model is intended to be used as a basis for the derivation of controllers and for dynamical simulation.
Respirometric control of the anaerobic period duration of an SBR bio-P process
Authors: Larose Alain , Perrier Michel , Comeau Yves
Published: May 2018

A new strategy based on respirometry for the control of the anaerobic period duration of an SBR bio-P process with a rapid-fill mode of operation was developed. Samples were withdrawn every 15 minutes from a lab-scale SBR during the anaerobic period and aerated intermittently in order to determine the respiration rate. The time of disappearance of the rapidly biodegradable substrate (acetate) was determined by the fall observed in the respiration rate. It was shown that, respirometry can be used not only for the characterization and control of aerobic processes, but also for the control of the anaerobic period duration of an SBR bio-P process.
Ranking strategies for stormwater management under uncertainty: sensitivity analysis
Authors: Reda A.L.L. , Beck M.B.
Published: May 2018

The disadvantageous consequences of stormwater perturbations of receiving water quality in urban environments can be attenuated by exercising control at various locations across the sewer network, wastewater treatment plant, and the stream itself. As part of a long-standing programme of research on developing an integrated approach to the management and real-time control of water quality in river basins, the paper examines the sensitivity of the associated strategies to model uncertainty. Specifically, results are presented for a case study based on a 10km stretch of the River Cam as it passes through the city of Cambridge in eastern England. The options for control are restricted to design and operational features of the wastewater treatment facility. Assessment is according to maximum and cumulative values of mass flows of ammonium-N and biochemical oxygen demand, together with the duration of dissolved oxygen concentration below 4.0 gm−3, at the downstream boundary of the system. A straightforward analysis of the sensitivity of these criteria to changes in the parameterisation of a model for receiving water quality shows that the ranking of strategies is robust in the face of model uncertainty. Minor differences in ranking occur as a function of whether judgement is based on ammonium-N or the other two attributes of water quality and whether attention is focused on the treatment plant in isolation or performance across the system as a whole. However, such conclusions must be qualified by noting that our analysis has been limited in its scope and elementary in its treatment of uncertainty.
Floc size distribution and bacterial activities in membrane separation activated sludge processes for small-scale wastewater treatment/reclamation
Authors: Zhang Boran , Yamamoto Kazuo , Ohgaki Shinichiro , Kamiko Naoyuki
Published: May 2018

Activated sludges taken from full-scale membrane separation processes, building wastewater reuse system (400m3/d), and two nightsoil treatment plants (50m3/d) as well as laboratory scale membrane separation bioreactor (0.062m3/d) were analyzed to characterize membrane separation activated sludge processes (MSAS). They were also compared with conventional activated sludges(CAS) taken from municipal wastewater treatment plants. Specific nitrification activity in MSAS processes averaged at 2.28gNH4-N/kgMLSS.h were higher than that in CAS processes averaged at 0.96gNH4-N/kgMLSS.h. The denitrification activity in both processes were in the range of 0.62-3.2gNO3-N/kgMLSS.h without organic addition and in the range of 4.25-6.4gNO3-N/kgMLSS.h with organic addition. The organic removal activity in nightsoil treatment process averaged at 123gCOD/kgMLSS.h which was significantly higher than others. Floc size distributions were measured by particle sedimentation technique and image analysis technique. Flocs in MSAS processes changed their sizes with MLSS concentration changes and were concentrated at small sizes at low MLSS concentration, mostly less than 60 μm. On the contrary, floc sizes in CAS processes have not much changed with MLSS concentration changes and they were distributed in large range. In addition, the effects of floc size on specific nitrification rate, denitrification rate with and without organic carbon addition were investigated. Specific nitrification rate was decreased as floc size increased. However, little effect of floc size on denitrification activity was observed.
Organic carbon and nitrogen removal in moving-bed biofilm reactors
Authors: Pastorelli G. , Andreottola G. , Canziani R. , Darriulat C. , de Fraja Frangipane E. , Rozzi A.
Published: May 2018

Pilot moving-bed biofilm reactors (MBBRs), fed on primary settled wastewater, were used in order to study organic carbon removal and nitrification. Nitrate uptake rate (NUR) tests were performed by feeding sodium acetate and potassium nitrate to a bench-scale moving-bed batch biofilm reactor. In both experiments the same polyethylene biofilm carriers were used. Both particulate and filtered COD removal rates appear to be proportional to the corresponding loading rates. Particulate COD removal is the net effect of adsorption onto and release from the biofilm surface. Filtered COD removal is the sum of the influent filtered COD removal and the removal of hydrolysed colloidal COD. Filtered COD removal rates could not be evaluated with a kinetic expression because back-diffusion from biofilm is not always negligible. Nitrification tests, performed at oxygen limiting conditions, show that the reaction rate was nearly first order with respect to dissolved oxygen due to liquid film diffusion. Denitrification batch tests showed denitrification rates very close to other reported data. Since the process proved reliable and easy-to-operate, it is suitable for application to small WWTPs, either in designing new plants or in upgrading existing overloaded activated sludge systems.
Treatment of sludges from on-site sanitation - low-cost options
Authors: Strauss M. , Larmie S. A. , Heinss U.
Published: May 2018

An overview of the current literature-based knowledge regarding faecal sludge (FS) treatment along with the results and conclusions from own field research are presented. Issues for further faecal sludge treatment studies are also addressed. The article focuses firstly on the characteristics of the various types of faecal sludge. A set of variables is proposed for minimum faecal sludge determination and faecal sludge treatment plant (FSTP) design and control. Priority treatment options particularly relevant to developing and newly industrialising countries are listed. They include solids-liquid separation by settling/thickening processes, sludge dewatering and drying in drying lagoons or drying beds, stabilisation ponds, and co-composting with refuse or other bulking/organic material of high carbon content. The results of in-depth monitoring of a faecal sludge treatment plant in Accra, Ghana, are reported. The plant receives septage and public toilet sludge and comprises solids-liquid separation by settling/thickening followed by a series of four ponds for the treatment of the liquid fraction. The four ponds in series all function as anaerobic ponds. Facultative pond conditions do not develop. This appears to be due to the suppression of algal growth through high levels of ammonia (NH3). Final effluent BOD is 300 mg/l as against 2,000 mg/l in the raw sludge mixture and 1,600 mg/l in the sedimentation tank effluent.