bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling the transient impact of rain events on the oxygen content of a small creek
Authors: Jacobsen J. L. , Madsen H. , Harremoës P.
Published: May 2018

Oxygen has been monitored in a small urban creek for a two months period. The purpose of the data collection is to use statistical modelling to obtain a better understanding of the phenomena governing the oxygen concentration. The long term goal is to influence the process of urban runoff to achieve oxygen concentration suitable for fish. Oxygen fluctuates significantly on a diurnal basis. Furthermore the purpose is to establish a model by which we are able to use rain data to estimate extreme values for comparison with standards for minimum oxygen concentration. The experience is that the fluctuations cannot be explained adequately on a deterministic basis alone. Significant stochastic variation has to be accounted for.

Data from a small stream is used to identify a dynamic model of the oxygen level as a function of solar radiation, water depth, and rain. The model is formulated in continuous time as two coupled stochastic differential equations. The continuous time formulation makes it possible directly to interpret the parameters of the model. Hence the model is useful for monitoring the actual state of the stream.

In this paper a grey box modelling approach, which is a statistical method taking the known physical relations into account, is used. This approach is closely related to the continuous time formulation. The parameters of the model are estimated using discrete time data and a maximum likelihood method. In evaluating the likelihood function a Kalman filter is used.

The dynamic model makes it possible to assess the transient impact of the urban runoff due to rain events, as well as the effect due to solar radiation. The ultimate outcome of the analysis is to determine the required size and location of storage basins to be constructed in the sewer system, in order to decrease combined sewer outflows and extreme oxygen depletion during rain.
Knowledge based diagnosis of solids-liquid separation problems
Authors: Bergh Sven-Göran , Olsson Gustaf
Published: May 2018

Often the suspended solids concentration in activated sludge treatment plants may display both large amplitudes and unnaturally fast changes. If the sensor calibration has been found satisfactory, the abnormal appearance has to be explained by the process itself. There may be three principal reasons for such a behaviour: severe hydraulic conditions, poor floc separation properties or very high sludge blanket. During these circumstances it is very informative to qualitatively examine the relationships between the suspended solids concentration variations and important influencing variables, such as the flow rates and the sludge blanket level. This kind of knowledge based diagnosis is superior to dynamic models for such odd behaviour. A simple on-line method to perform the diagnosis is presented. The method has been tested on a massive set of data from a full scale wastewater treatment plant in Sweden and shown unexpected good ability to supply early warnings. It is also shown that small hydraulic disturbances may purposefully be injected into the settler in order to analyse the risk for process failure.
Detoxification of industrial wastewaters in an Extractive Membrane Bioreactor
Authors: Livingston A. G. , Freitas dos Santos L. M. , Pavasant P. , Pistikopoulos E. N. , Strachan L. F.
Published: May 2018

Point source treatment of aqueous wastes produced in the chemical industry and containing toxic organic compounds in an Extractive Membrane Bioreactor (EMB) is reported. The EMB is shown to be effective in removing a range of toxic organic compounds, achieving over 99% removal at wastewater-reactor contact times of less than 30 minutes. A model which predicts the removal efficiency is discussed, and a new, advanced EMB system is described which overcomes the mass transfer limitations in the original plug flow configuration. Finally, data showing the effect of the membrane attached biofilms on membrane mass transfer is used to illustrate one of the key problems that must be solved during technology transfer if the EMB process is to prove successful at industrial scale.
Biodegradability of N-substituted aromatics and alkylphenols under methanogenic conditions using granular sludge
Authors: Razo-Flores Elías , Donlon Brian , Field Jim , Lettinga Gatze
Published: May 2018

The biodegradability of seventeen N-substituted aromatic and six alkylphenol compounds were evaluated under methanogenic conditions. Biodegradation was assessed in batch assays inoculated with unacclimated and predigested anaerobic granular sludge at 30°C under agitated conditions over a 150 day period. The compounds were supplied at sub-toxic concentrations in the assays in order to prevent inhibition to the methanogens. The biodegradability test was performed by the measurement of the methane composition in the headspace of the serum flasks. The methanogenic consortia completely mineralized 2-, 3-aminobenzoate, 2-aminophenol and 4-cresol; whereas, 4-aminobenzoate was only partially degraded. The other N-substituted compounds and the alkylphenols tested were not biodegradable under the experimental conditions employed. An additional biodegradability assay was conducted with sludge from an upward-flow anaerobic sludge bed reactor adapted to the degradation of 2-nitrophenol. This sludge mineralized 2-aminophenol without any lag phase while the unadapted sludge required 110 days of acclimation. The three aminobenzoate isomers were fully mineralized by the adapted sludge after similar lag periods observed in the unadapted sludge. The 2-nitrophenol adapted sludge cross-acclimatized to the mineralization of 5-aminosalicylate and 4-aminophenol. This constitutes the first report demonstrating the anaerobic mineralization of 5-aminosalicylate, which indicates that at least some azo dye cleavage products can be degraded in methanogenic consortia.
External and internal sources which inhibit the nitrification process in wastewater treatment plants
Authors: Sinkjær O. , Bøgebjerg P. , Gruüttner H. , Harremoës P. , Jensen K. F. , Winther-Nielsen M.
Published: May 2018

In connection with the upgrading of the two largest wastewater treatment plants in the Copenhagen area to nutrient removal special attention has been paid to the nitrification process regarding inhibition effects. Inhibitory substances in the wastewater could be identified by simple batch tests, and the long-term effects on the nitrification process were tested in pilot plants or at full-scale. A distinction could be made between effects produced by wastewater from external sources in the catchment area and internally circulated flows in the wastewater treatment plant. Results from programmes monitoring the influent to the Lynetten WWTP and the Damhusåen WWTP and the catchment areas have revealed that discharges from industries are to be considered the most important external sources of inhibition. The load from the external sources has decreased during the investigation period, and since 1993 the nitrification capacity monitored at the pilot plants has been in agreement with the design basis. The recycling of the scrubber water from the cleaning of sludge incineration flue gas was found to be an important internal source of inhibition at the Lynetten WWTP. Investigations show that it is possible to reduce the effect by modifying the existing incineration process and, if necessary, combining it with separate treatment.
Leachate chemistry and precipitates mineralogy of rudolfsgruvan mine waste rock dump in central Sweden
Authors: Zhixun Lin
Published: May 2018

The chemical and mineralogical properties of leachates and precipitates formed in a sulfide ore mine waste rock dump were studied by atomic adsorption spectrometry, optical petrography, X-ray diffractometry, scanning electron microscopy with energy dispersive spectroscopy. The dump is divided into a leached horizon and an accumulation horizon. The intensity of sulfide oxidation decreases with depth. Leachates are characterized by acid and enriching Fe, SO4 and other metals. Secondary minerals consist mainly of goethite, with some jarosite, schwertmannite ferrihydrite elemental sulphur and Cu and Zn compounds including copper iron oxides, Cu and Zn oxides (hydroxides) and Zn-sulfates. Dissolved Al, Cu, Zn, Si and S are partialy retained by goethite, precipitating in a microbanded texture. The banded formation indicates temporal variability in pore water chemistry influenced by episodic/seasonal hydraulic flushing. The dump is rather old and could provide an important information, or “natural analogue” to the future evolution of the rock dumps that are being generated at currently operating mines.
Dechlorination of chlorobenzenes in anaerobic estuarine sediment
Authors: Masunaga Shigeki , Susarla Sridhar , Yonezawa Yoshitaka
Published: May 2018

The reductive dechlorination of chlorobenzenes (CBs) in an anaerobic estuarine sediment was examined. The sediment was preexposed to various anthropogenic chemicals from the surrounding industries. The sulfate content (20 mmoles/l) in the interstitial waters indicated that the sediment was sulfidogenic. All the CBs were transformed following a first-order reaction kinetics with rate constants ranging from 0.0016 to 0.0389 day−1 or half-lives between 17 and 433 days. Disappearance of CBs in autoclaved sediment were observed but to a much less extent than in the test sediment. Detected intermediates indicated that the removal of chlorine atom occurred at all possible positions on the aromatic ring. The contribution of different dechlorination pathways were estimated using branched chain first-order irreversible reaction kinetics. The results showed that the preferential dechlorination was in the following order: two chlorine atoms on both sides > one of the adjacent chlorine atoms > chlorine with no adjacent chlorine atoms. The major pathway observed for CBs followed a thermodynamically most favorable step that gave the highest energy for dechlorination.
A preliminary investigation on the photocatalytic degradation of a model humic acid
Authors: Bekbölet Miray , Özkösemen Gölhan
Published: May 2018

The research reported addresses the destructive removal of humic acid in aqueous medium by a photocatalytic oxidation process. Bench scale experiments were carried out using titanium dioxide as the photocatalyst and Black Light Fluorescent Lamp as the irradiation source. Following 1 h irradiation 40 % TOC and 75% Color400 removals were attained for 50 mg/L humic acid solution in the presence of 1.0 mg/mL TiO2. The optimum TiO2 loading was found to be 1.0 mg/mL. Acidic medium accelerated the photocatalytic degradation rate whereas a retardation factor of 0.4 was recorded in alkaline medium. The evaluation of the THMFPs of the photocatalytically treated humic acid solutions revealed that the destructive removal of humic acid was effective enough to keep the THM levels below the maximum contaminant level of 0.10 mg/L (USEPA).
The influence of some parameters upon the aluminium leaching out by limousin soils through batch reactor
Authors: Guibaud G. , Ayele J. , Mazet M.
Published: May 2018

In order to evaluate the influence of an intensive forestry on the monomeric aluminium and organic matter release by the Limousin forest (France), an acidic brown earth soil planted with 3 different forests (centenary Douglas, young Douglas and Chesnuts) was selected. According to batch reactor experiments, the results show that all A horizons the most contaminated distilled water with monomeric aluminium and organic matter. The higher released concentrations of monomeric aluminium were obtained with the old Douglas upper soil horizon. When the soil was in contact with acidic solution, the more the pH was acidic, the more monomeric aluminium released concentration was important.
Expanding the horizons of pond technology and application in an environmentally conscious world
Authors: Pearson H. W.
Published: May 2018

Waste stabilisation pond technology has advanced greatly in terms of application and reliability and this has come from the wealth of modern research. Pond technology can be designed to meet exacting effluent standards and can treat both domestic sewage and a wide range of industrial wastewaters. They are now very much on a par with other wastewater treatment technologies. A wide range of pond types now exist allowing for flexibility in design and optimisation of the process to meet a particular applications or set of conditions. Ponds can be made to combine treatment and effluent storage and are the best and cheapest option for treating wastewaters for subsequent reuse in aquaculture and agriculture. Ponds can be designed to produce large quantities of algal biomass for animal and potential human consumption and for energy production via methane. Ponds are thus a modern wastewater reclamation and resource recovery technology in tune with current environmental thinking.
Design of facultative ponds based on uncertainty analysis
Authors: von Sperling Marcos
Published: May 2018

The paper presents a methodology for the utilisation of the Uncertainty analysis based on Monte Carlo simulations for the design of wastewater treatment systems. The special and important case of facultative-ponds design is exemplified. The design is carried out a large number of times, each run with different values of the inputs, randomly selected from uniform distributions within ranges which define the designer's uncertainty with the data. The results are interpreted statistically, giving elements for the selection of more or less conservative designs, according to the resulting effluent quality. The procedure for undertaking a Sensitivity Analysis is also described and exemplified, allowing the designer to concentrate more efforts on a more accurate determination of those inputs found to be significantly important.
Ammonia volatilization from a piggery pond
Authors: Shilton Andy
Published: May 2018

There is a need to improve the performance of agricultural wastewater stabilization ponds. In particular, a better understanding of the relative importance of the nitrogen removal mechanisms is required. The objective of this study was to quantify the magnitude of ammonia volatilization from a piggery pond in order to determine its significance as a nitrogen removal mechanism. A model of a typical piggery pond was established and sampled for ammonia, TKN, COD and pH. A method was developed to allow the rate of ammonia volatilization to be quantified. The rates of ammonia and total nitrogen removal were established, as were the corresponding COD and pH levels over a series of pond ammonia concentrations. The rate of ammonia volatilization ranged from 355 to 1534 mg/m2.d, increasing with higher concentrations of ammonia and TKN. These rates compared well with volatilization rates from other types of piggery waste disposal. It was concluded that although it is impractical to use ammonia volatilization in its own right to achieve high levels of nitrogen removal, it does make a significant contribution to the overall nitrogen removal potential of a piggery pond system.
Immobilization in fixed film reactors: an ultrastructural approach
Authors: Harendranath C. S. , Anuja K. , Singh Anju , Gunaseelan A. , Satish K. , Lala Krishna
Published: May 2018

An ultrastructural approach has been attempted to study the surface features of 29 packing media reported in literature and a few more potential candidates for immobilizing micro-organisms. The electron micrographs reveal important features like degree of smoothness/roughness, microcrystals and fibres, ridges, macro and micro pores <196> their dimensions, depth and distribution and thereby the biomass accumulation capacity of the media. Based on microscopic observations the packing media have been classified as (i) smooth - polypropylene bead, glass bead, peristaltic tube, porcelain, powdered activated carbon, perspex, polyvinyl chloride and glass (ii) uneven - straw, paddy stem, nylon, sand, gravel and stone (iii) porous - jute, gravel, soil, granulated clay, limestone, ceramic, shell, refractory brick, diatomaceous earth, casuarina seed, granular activated carbon thermocol, sponge, pumice stone and polyurethane foam. The results clearly show that ultrastructural examination and image analysis can be a quick, effective and direct visual technique for selecting support media for bioreactors. An example of application of quantitative image analysis for providing quantitative geometric description of surface features is also presented.
The first flush in sewer systems
Authors: Saget Agnès , Chebbo Ghassan , Bertrand-Krajewski Jean-Luc
Published: May 2018

The first flush phenomenon of urban wet weather discharges is presently a controversial subject. Scientists do not agree with its reality, nor with its influences on the size of treatment works. Those disagreements mainly result from the unclear definition of the phenomenon. The objective of this article is first to provide a simple and clear definition of the first flush and then to apply it to real data and to obtain results about its appearance frequency. The data originate from the French database based on the quality of urban wet weather discharges. We use 80 events from 7 separately sewered basins, and 117 events from 7 combined sewered basins. The main result is that the first flush phenomenon is very scarce, anyway too scarce to be used to elaborate a treatment strategy against pollution generated by urban wet weather discharges.
The use of soluble organic polymers in waste treatment
Authors: Bolto Brian A. , Dixon David R. , Gray Stephen R. , Ha Chee , Harbour Peter J. , Le Ngoc , Ware Antony J.
Published: May 2018

Organic polymeric flocculants have been used in water purification for several decades as coagulant aids or floc builders, after the addition of inorganic coagulants like alum, iron salts or lime. The increased use of cationic polyelectrolytes as primary coagulants instead of inorganic salts, which has occurred in recent times, arises from their significant inherent advantages. The main ones are faster processing, a lower content of insoluble solids to handle, whether by sedimentation, filtration, flotation or in biological conversion, and a much smaller sludge volume. Polymers have often been used in chemically assisted sedimentation of sewage solids to enhance the removal of suspended matter. The concept is applicable as well to the primary coagulation of industrial wastewaters where the separation may be based on flotation, as in examples from the leather, steel, wool scouring, cosmetic, detergent, plastics, dyehouse, paper, food processing and brewing industries. A cationic polymer of particular charge density is optimal, and hydrophobically modified polymers have relevance in the case of oil and grease removal. The burden of solids which must be floated is much reduced relative to systems utilising inorganic coagulants, and the dosage of chemicals overall is lower. In some cases the addition of some inorganic coagulant is unavoidable, as in the case of highly coloured effluents; in others, an anionic surfactant is needed to facilitate flotation.
Experimental investigation of the effect of particle size distribution of suspended particles on microfiltration
Authors: Chang J. S. , Tsai L. J. , Vigneswaran S.
Published: May 2018

Suspended particle size is one of the main factors which affect the performance of the microfiltration. Experimental results with bi and trimodal suspensions of latex particles clearly showed that the permeate flux and the quality were significantly affected by the particle size and its distribution, especially when the particle size was smaller than the pore size of the membrane.
Characteristics of fouling due to clay-organic substances in potable water treatment by ultrafiltration
Authors: C.-H. Kim , Hosomi M. , Murakami A. , Okada M.
Published: May 2018

Effects of clay on fouling due to organic substances and clay were evaluated by model fouling materials and kaolin. Model fouling materials selected were protein, polysaccharide, fulvic acid, humic acid and algogenic matter (EOM:ectracellular organic matter, microbial decomposition products) and kaolin was selected as the clay material. Polysulfone membrane (MWCO(Molecular Weight Cut-Off) 10,000, 50,000 and 200,000) was used as an ultrafiltration membrane. In particular, the flux measurement of solutions containing algogenic matter used an ultrafiltration membrane of MWCO 50,000. The flux of protein and polysaccharide with coexistence of kaolin increased in the case of the ratio of MW/MWCO being greater than one, but did not increase in the case of the MW/MWCO ratio being below one. In contrast, the flux of fulvic acid and humic acid with coextence of kaolin decreased regardless of the ratio of MW/MWCO. The addition of dispersion agent and coagulant in the organic substances and kaolin mixture solution changed the size distribution of kaolin, and resulted in a change of the flux. EOM and microbial decomposition products decreased with the increase of the fraction of organic matter having molecular weight more than MWCO of membrane. The flux of the algogenic organic matter with coexistence of kaolin decreased with the increase of the amount of kaolin. It was suggested that the decline of the flux with coexistence of kaolin was due to the change of the resistance of the kaolin cake layer corresponding to the change in kaolin size distribution with charge.
Sewer sediments: preparation methods for enumerating bacteria
Authors: McGregor Iain , Souter Nicola H. , Ashley Richard M.
Published: May 2018

In the UK, the Urban Pollution Management programme has contributed to extensive international research concerning solids associated with urban drainage systems.

Since 1986, as part of the UPM programme, research undertaken at the Wastewater Technology Centre, University of Abertay Dundee, has focused primarily upon the characteristics and movement of solids and associated pollutants in combined sewer systems.

These investigations have considered the behaviour of sediments and their attached pollutants during dry weather and storm flow conditions, and also the degree of pollutants associated with, and released from sewer sediments during periods of increasing sediment bed shear stresses. Data collection and sample analysis were driven by requirements specified for the development of a United Kingdom sewer flow model termed “MOSQITO”, with the basic chemical parameters ie; COD, BOD and ammonia, of sewage and sewer sediments. A data collection programme is described which assesses the feasibility of using combined sewer sediment preparation protocols, normally used for these chemical analyses, to enumerate bacterial indicator organisms present in deposited sediments. The data were analysed to investigate whether the methods used were precise in terms of repeatability, prior to more extensive studies being undertaken to provide sewer sediment data for bacterial numbers.
Technical solutions envisaged in managing solids in combined sewer networks
Authors: Chebbo Ghassan , Laplace Dominique , Bachoc André , Sanchez Yves , Le Guennec Benoit
Published: May 2018

Solids in combined sewer networks represent two important technical questions:

- the clogging of man-entry sewers, and

- pollution in urban wet weather discharges, whose main vectors are generally suspended solids.

In this paper, we shall present first, curative technical solutions which avoid or remove deposits in man-entry sewers. We shall discuss the partial extraction of the largest solids; selective trapping of bed load solids, which form deposits; and the displacement of deposits using dry weather flow flushing waves.

We shall then examine technical solutions to control pollution in urban wet weather discharges. This will show that decantation is an efficient means of fighting pollution. However, it is not always feasible because it involves large scale investments. Complementary methods should, therefore, be developed and used at different points in the water's passage through an urban drainage area.
Petrochemical wastewater treatment with aerated submerged fixed-film reactor (ASFFR) under high organic loading rate
Authors: Park T. J. , Lee K. H. , Kim D. S. , Kim C. W.
Published: May 2018

An aerated submerged fixed-film reactor (ASFFR) was developed to treat a petrochemical wastewater with high organic loading rate, where stationary submerged biofilms were attached to net-type media (SARAN 1000D) under diffused aeration. The specific surface area of SARAN 1000D was 400 m2/m3 approximately. The organic removal ability of the reactor was tested in three lab-scale ASFFRs. The reactor demonstrated 91.8-96.6% removal efficiencies of soluble chemical oxygen demand (SCOD) and exhibited efficient and stable performance at organic loadings of 1.02-6.21 kg COD/m3 day. When the media packing ratio increased the COD removal efficiency increased, while the effluent COD and SS concentrations were stable. The organic removal rates were dependent on the effluent SCOD concentration and the reaction orders were the same as or lower than 0.5.

Based on the experimental results, the ASFFR should be very suitable for treating petrochemical wastewater with relatively high organic loading rate.
Reducing chlorinated organics, AOX, in the bleachery effluents of a Turkish pulp and paper plant
Authors: Yetis Ulku , Selcuk Aylin , Gokcay Celal F.
Published: May 2018

The possibility for reducing the chlorinated organic compounds in the bleacheary effluents of the Turkish pulp and paper industry has been studied. Within the experimental work of this study, three different chlorine dioxide substitutions and three different total chlorine application rates were examined and nine experiments were performed. The AOX formation has been shown to be proportional to the amount of molecular chlorine consumed during delignification, regardless of whether it is from chlorine or chlorine dioxide. However, molecular chlorine contributes to AOX formation to a much greater extent. The lowest AOX concentrations were achieved when the total available chlorine dosage was lowest (10 kg/ton) and ClO2 substitution level was highest. An increase in the percentage of chlorine dioxide leads to a substantial reduction in the AOX concentration in the bleachery effluents. A chlorine dioxide substitution of 90%, when the chlorine charge was 40 kg/ton, causes a 77% decrease in the DC-AOX, and a 82% decrease in the EO-AOX. However, as the chlorine dioxide substitution reduced to 10%, the decrease in the the AOX concentration became less and only 51% and 41% reductions in DC-AOX and EO-AOX could have been achieved respectively.
Identifying and fighting inhibition of nitrification at Öresundsverket
Authors: Jönsson Karin , Magnusson Peter , Jönsson Lars-Erik , Hellström Bengt Göran , Jansen Jes la Cour
Published: May 2018

After extension of Öresundsverket in Helsingborg severe nitrification problems have occurred. Complete inhibition of nitrification has been recognized once and a general reduction of nitrification capacity has been found compared to design, to other Swedish treatment plants and to internationally accepted design criteria.

A comprehensive examination of inhibition of nitrification has identified industrial sources as the dominating contributors. Some industries have been identified as important sources but fighting inhibition of nitrification requires more than tracking down a few dominating industries, since examination shows that discharges of inhibitory substances are widespread among the industries in the catchment area.

Naturally, fighting inhibition of nitrification requires the elimination of contributions from industries with identified discharge. Furthermore information campaigns directed towards the industries in general are required and finally it is necessary to include requirements for inhibitory substances in the industrial discharge permits.
Severe bulking and foaming at the Himmerfjärden WWTP
Authors: Holmström Hans , Bosander Jan , Dahlberg Alf-Göran , Dillner-Westlund Åsa , Flyborg Lena , Jokinen Karri
Published: May 2018

Several years of trouble-free operation with pre-denitrification at the Himmerfjärden WWTP concerning bulking and foaming have been followed by an unstable period. Two bulking incidents with no foaming by Microthrix parvicella were found to be caused by ethanol addition. Other bulking and foaming occurrences by Microthrix could be correlated to the production of volatile fatty acids in some of the sludge treatment steps. It is possible that a more widespread use in society of washing and cleaning products based on vegetable oils has promoted the ability of Microthrix to compete with floc-forming organisms, especially when ethanol or volatile fatty acids are present.
Water business changes – A driver for green clean compact technologies
Authors: Matthews Peter
Published: May 2018

The paper describes the development of the water industry in England and Wales from 1974 to 1995 through the perspective of Anglian Water which serves Eastern England. The experiences of that development provide ample evidence of the synergistic relationship between organisational structure and technologies used. The water industry has and is learning the same lessons as other global industries. If water management is to have its rightful place in protecting and utilising planetary resources properly, it must use the experience and lessons of other global industries. The paper indicates the first steps in this journey.
Thickening in an activated sludge process clarifier
Authors: Halttunen Sakari
Published: May 2018

Sludge thickening is modeled dynamically and results of simulations are compared to observations of sludge blanket in different clarifier types. Thickening is described to depend on the inverse of thickening factor and solids concentration. Thickening factor can be measured in test cylinder or estimated on DSVI. Short circuiting inside the sludge blanket is modeled by combination of PFR- and CSTR-blocks of thickening. The results indicate that sludge blanket behavior can be explained by thickening.
Design and construction of aeration systems for optimum operation of large wastewater treatment plants
Authors: Bischof Franz , Höfken Marcus , Durst Franz
Published: May 2018

The construction and operation of large wastewater treatment plants are very important tasks today. Choosing the optimum process design can help to keep initial costs low. Careful operation and modern equipment reduces the operational costs. Taking into account the huge demand (Anonymous EEC-Report 1990) for new wastewater treatment plants or plants which need to be upgraded after the new EEC legislation concerning sewage treatment came into force in May, 1991 (Anonymous EEC-Guideline 1991) it is quite clear that only cost-effective processes supported by energy-efficient equipment are the answer to economical wastewater treatment. Regarding the operational costs for biological treatment, approximately 70% of the total energy consumption is used for the activated sludge part of the treatment plant, i.e. for the stirring and aeration systems (Höfken et al. 1992). That shows how important the proper design of such systems is and implies that only innovative and energy-efficient equipment should be used.

This paper presents theoretical considerations for the design of aeration systems for aerobic processes. These considerations lead to recommendations for the construction and the operation of aeration systems.
Influence of the enhanced biological phosphorus removal on the waste activated sludge production
Authors: Jardin Norbert , Pöpel H. Johannes
Published: May 2018

The effect of the enhanced phosphorus removal process (EBPR) on the waste activated sludge production and the type of phosphorus storage were investigated in two continuous flow activated sludge systems on semi-technical scale. One of the plants (plant II) was operated with the A/O process, whereas the other plant (plant I) was operated in a conventional, fully aerobic mode and served as a control. By monitoring the elementary composition of the activated sludge solids in plant II it was proved that a major part of the enhanced phosphorus removal was due to a storage as polyphosphate (poly-P). The additional uptake of phosphorus resulted in an increase of the inorganic sludge mass which was determined as 3.05 g SS/g P using the results of the measurements of the non volatile solid fraction. This value was also experimentally confirmed by the measurement of the difference between the WAS production of plant I and plant II. Based on the specific WAS production, an additional dry solids production of 3.14 g SS/g P was calculated. No indications for a significant difference of the organic sludge production between both plants were found, although the organic WAS production was slightly higher in experimental periods with a relatively high phosphorus content of the activated sludge solids of plant II.
Effect of cyclic oxygen exposure on the activity of denitrifying phosphorus removing bacteria
Authors: Kuba T. , van Loosdrecht M. C. M. , Heijnen J. J.
Published: May 2018

The effect of oxygen on the activity of denitrifying phosphorus removing bacteria has been studied. Denitrifying phosphorus removing bacteria were enriched without oxygen in an anaerobic-anoxic SBR (sequencing batch reactor) over a long time, after which an aerobic phase was introduced into the SBR. The performance on phosphorus and nitrogen removal was examined for an anaerobic-aerobic-anoxic SBR. It could be concluded that oxygen has no detrimental effect on the denitrifying dephosphatation activity. The maximum phosphorus uptake rate by the enriched denitrifying sludge was almost equal for anoxic and aerobic conditions, and the anoxic phosphorus removal activity was kept within at least 5 months after the introduction of the aerobic phase. From the experiments it followed that the advantage of applying denitrifying phosphorus removing bacteria can only be obtained in a pre-denitrification process like the UCT-type of process.
Influence of sludge age on enhanced phosphorus removal in biological systems
Authors: Rodrigo M. A. , Seco A. , Penya-roja J. M. , Ferrer J.
Published: May 2018

The phosphorus removal process was studied in a bench-scale plant for a period of 300 days. The process was observed to depend greatly on two parameters: the amount of volatile fatty acid (VFA) taken up in the anaerobic stage and sludge age. For a given sludge age, phosphorus release versus VFA uptake in the anaerobic stage could be fitted to a straight line, while phosphorus uptake in the non-anaerobic stages fitted a logarithmic curve. Thus, phosphorus removal occurred within a limited VFA uptake range. The range width and the phosphorus removal capacity varied with sludge age.
Stability and variation in sludge properties in two parallel systems for enhanced biological phosphorus removal operated with and without nitrogen removal
Authors: Lee Natuscka M. , Carlsson Hans , Aspegren Henrik , Welander Thomas , Andersson Bengt
Published: May 2018

In order to introduce nitrogen removal, many conventional activated sludge systems in Sweden have been transformed into low-loaded systems during the 1990's. Occasionally these systems have been combined with enhanced biological phosphorus removal (EBPR). Increased problems of sludge loss from secondary clarifiers have aroused new interest in the properties of activated sludge. The aim of this study was to investigate the long-term variation and stability of sludge properties in two parallel EBPR systems, operating on the same wastewater. One of the systems was designed as a conventional system, and the other as a low-loaded system with nitrogen removal. The study was performed at the Sjölunda plant in Malmö during a two-year period, in a pilot plant which has been in operation since 1986.

The diluted sludge volume index (DSVI) was found to be about 150 ml/g in both systems. The highest values were recorded during the winter season. The variation in the DSVI was much greater in the conventional system than in the low-loaded system. The dominating filamentous bacteria in the conventional system were Type 021N and Thiothrix, and in the low loaded system Type 0041/0675 and Type 0092. The EBPR operation induced large amounts of poly-P-containing flocs in both systems. Although it was not possible to determine to what extent the poly-P-containing flocs affected the sludge properties in this study, it was clearly demonstrated that EBPR operation may not always provide conditions which lead to superior sludge properties.
Development of 2-reactor intermittent-aeration activated sludge process for simultaneous removal of nitrogen and phosphorus
Authors: Sasaki Kousei , Yamamoto Yasuji , Tsumura Kazushi , Ouchi Sachiko , Mori Yutaka
Published: May 2018

We have developed a new intermittently aerated anaerobic-aerobic activated sludge process. This process employs 2 reactors connected in series, and is capable of controlling the duration of aerobic, anoxic and anaerobic conditions in both reactors by utilizing the ORP bending point, which corresponds to the termination of denitrification. One cycle of aeration and agitation takes approximately 120 minutes. In the 1st reactor, nitrification and phosphorus uptake occur in the aeration period, followed by denitrification and phosphorus release in the agitation period. In the 2nd reactor, nitrification and phosphorus uptake are conducted during aeration, and denitrification and weak phosphorus uptake during agitation. A one-year pilot plant experiment using sewage (22 m3/day) showed stable and high removal ratios of 98% for BOD, 92% for T-N, and 85% for T-P under conditions of HRT 20 hours and water temperature 9∼33°C.
Phosphorus transport in saturated slag columns: experiments and mathematical models
Authors: Lee S. H. , Vigneswaran S. , Bajracharya K.
Published: May 2018

Excessive phosphorus (P as orthophosphate) is one of the major pollutants in natural water that are responsible for algal blooms and eutrophication. P removal by slag is an attractive solution if the P sorption capacity of slag is significant. To design an efficient land treatment facility, basic information on the behaviour of P in the media-water environment is required. In this study, detailed column experiments were conducted to study the P transport under dynamic condition, and mathematical models were developed to describe this process. The column experiments conducted with dust and cake waste products (slag) from a steel industry as adsorbing indicated that they had higher sorption capacity of P than that of a sandy loam soil from North Sydney, Australia. P transport in the dust and cake columns exhibited characteristic S-shaped or curvilinear breakthrough curves. The simulated results from a dynamic physical nonequilibrium sorption model (DPNSM) and Freundlich isotherm constants satisfactorily matched the corresponding experimental breakthrough data. The mobility of P is restricted by the adsorbents and it is proportional to the sorption capacity of them.
Biological phosphate and nitrogen removal in a biofilm sequencing batch reactor
Authors: Garzón-Zúñiga Marco A. , González-Martínez Simón
Published: May 2018

The possibility of joining biological phosphorus and nitrogen removal in a biofilm sequencing batch reactor was studied using an operation strategy with four reaction phases: Anaerobic/Aerobic/Anoxic/Aerobic. A 1,000 liter pilot scale reactor, filled with Pall-Rings as biofilm support was fed with municipal wastewater. After operating the system for 615 days, optimal operation conditions were establish to obtain highest removal rates with a well established microbial community. Adequate cycle and phase duration were established and organic loading values were obtained for different treatment purposes. The system worked successfully obtaining removals of COD, phosphates and ammonia nitrogen of 89 ± 1%, 75 ± 15%, and 87 ± 10%, respectively. The high removal efficiencies of P and N were obtained thanks to the establishing relationship between nitrifying bacteria and phosphate accumulating bacteria.
Intermittent dosage of ethanol in a pre-denitrifying activated sludge process
Authors: Hasselblad Serena , Hallin Sara
Published: May 2018

A pilot-scale activated sludge reactor is used to examine the effect of intermittent ethanol dosing to provide supplemental carbon to improve process performance. The early results noted here indicate the value of this strategy to improve denitrification.
Biological-ion exchange process for ammonium removal from secondary effluent
Authors: Green Michal , Mels Adriaan , Lahav Ori , Tarre Sheldon
Published: May 2018

A new concept for ammonium removal from secondary effluent by zeolite followed by bio-regeneration has been studied. In contrast to other studies of hybrid biological-ion exchange multireactor systems, the proposed process uses the ion exchange material, zeolite, as the carrier for the nitrifying biomass. This enables the two mode process to be carried out in a single reactor.

In the first mode (ion exchange), secondary effluent is passed through an ion exchange column where ammonium is concentrated in the zeolite. During the second mode (bioregeneration), the absorbed ammonium is released gradually and converted to nitrate by the active biomass residing on the zeolite. Nitrification is carried out batchwise and in a small volume reactor where optimal conditions can easily be maintained. Moreover, the addition of chemicals for the desorption of ammonium is minimal due to regenerant reuse during several cycles of nitrification. As a result, operational costs and production of large volumes of brine are minimized.

Batch and breakthrough experiments showed that the amount of ammonium adsorbed on the chabazite is strongly affected by the presence of competing cations present in secondary effluent. A reduction of about 75% was observed when using a typical Israeli sewage ion composition. The attached biomass did not significantly effect the efficiency of the ion exchange column.

Ammonium desorption experiments showed that regeneration with 10,000 mg/L Na+ is much faster than with 2440 mg/L (more than 90% ammonium recovery after 40 and 70 bed volumes, respectively).

A nitrification rate of 6 g NH4-N/(L reactor *day) was obtained in a fluidized bed reactor with chabazite as the carrier. Although this rate is in the high range of reported values for biofilm reactors, desorption experiments proved that nitrification will be the process's rate limiting step, rather than the desorption rate when regenerant solutions as low as 2440 mg/L Na+ are used.
Aerated denitrification in full-scale activated sludge facilities
Authors: Goronszy Mervyn C. , Demoulin Gunnar , Newland Mark
Published: May 2018

The practice of manipulating activated sludge reaction environments to obtain maximum nitrogen removal has been optimized using cyclic activated sludge technology. In its simplest form, the sequences of fill aeration, settle and decant are consecutively and continuously operated in a compartmented reactor in which an initial reaction volume performs the function of a biological selector with biomass from a final reaction volume. The technology incorporates the principles of biological accumulation - regeneration processing in which a variable volume plug-flow reaction environment precedes a variable volume complete-mix reaction environment. Both reactor volumes are typically in continuous fluid communication. This configuration and mode of operation allows removal performance in domestic wastewater treatment applications to meet less than 5 mg/L total nitrogen discharge limits. Low nitrogen concentrations are obtained using modified aeration sequences only in which the bulk phase dissolved oxygen concentration is typically less than 2 mg/L in a ramped profile beginning at zero. By that means a simultaneous or co-current nitrification-denitrification mechanism is obtained. Track run data illustrate the performance obtained in domestic applications.
New criteria for stormwater discharges into urban streams
Authors: Wagner Andreas , Geiger Wolfgang F.
Published: May 2018

The Germany state of the art for designing stormwater discharges and combined sewer retention tanks is emission oriented. This approach does not adequately reflect the needs of urban brooks. Literature on the topic shows the need for further research investigations. Firstly, a detailed study is used to define the hydraulic impact of discharges and overflows on an urban stream. This paper attempts to relate the hydraulic impact in the form of shear stress with substrate movement. The correlation between the extent of stormwater impacts and ecomorphological properties is considered to be the significant parameter for evaluation of runoff. Finally a new approach for assessing stormwater discharges into urban brooks is presented. This approach is divided into hydraulic and pollutant components and takes the ecomorphological properties into consideration.
Estimation of domestic wastewater characteristics in a developing country based on socio-economic variables
Authors: Campos H. M. , von Sperling M.
Published: May 2018

The paper presents the analysis of data related to the domestic wastewater characteristics from several areas situated in a large Brazilian city. Simple regression models are presented for the prediction of basic wastewater characteristics, such as water consumption (l/inhab.day), wastewater production (l/inhab.day),BOD load (g/inhab.day) and BOD concentration (mg/l). The models are based on simple socio-economic variables, with special attention to the easily obtainable variable of total family income (number of minimum salaries earned per month). Most of the models are able to give an excellent prediction of the desired wastewater variables. Additionally, the behaviour of the main wastewater characteristics according to the hour of the day and the day of the week are analysed. Based on the results obtained, it is suggested that the classical figures of BOD concentration of 300 mg/l and per capita BOD load of 54g/inhab.d do not apply to the typical population predominant in most areas of Brazil. The actual BOD concentrations are frequently higher than 300 mg/l, while the BOD load is frequently lower than 54 g/inhab.d. The results obtained can be used for design purposes in the areas studied, and possibly in areas of similar characteristics, substituting the classical figures obtained from foreign textbooks.
Novel high-rate processes for sewer overflow treatment
Authors: Booker N. A. , Öcal G. , Priestley A. J.
Published: May 2018

There is a demonstrated need for high-rate processes, for the treatment of storm induced sewer overflows, that are capable of removing particulate solids down to at least 10 microns in size. Chemical coagulation processes are capable of producing a high quality treated sewage effluent that would be suitable for discharge to a receiving water such as a separate stormwater system. Compact, high-rate methods of solids separation within these processes will make them more attractive for use in areas where land is expensive or unavailable for large storage basins or settling tanks. Two approaches that are being developed at the CSIRO, Division of Chemicals and Polymers, appear to fulfil this requirement; these are magnetic assisted sedimentation and a high-rate filtration process. Both approaches combine the advantages of chemical coagulation with a high-rate separation of the flocculated solids and are discussed in this paper.