bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen removal from wastewater in a pilot plant operated in the recirculation anoxic-oxic activated sludge mode
Authors: Burica Olga , Strazar Marjeta , Mahne Ivan
Published: May 2018

The recirculation activated sludge process with preanoxic treatment was applied for biological reduction of the nitrogen content in municipal wastewater at pilot plant level. The pilot plant of total volume 3 300 1 with an initial anoxic to aerobic volume ratio of 40 : 60 was fed with wastewater from the first heavily loaded aerobic stage of a local wastewater treatment plant. Experiments were run over the summer and winter periods, the influent wastewater temperature being approx 24°C and approx 10°C, respectively. Special attention was paid to the hydraulic retention time, the total as well as mineral nitrogen loading, the aerobic to anaerobic volume ratio, and to the energy demand for denitrification of oxidised mineral nitrogen forms. Under optimal operating conditions the effluent quality that could be achieved was about 10 mg/l of total nitrogen (74% removal) and less than 2 mg N/l mineral nitrogen (87% removal), while simultaneously 205 mg BOD5/l in the influent was reduced to less than 7mg O2/l in the effluent. It was found feasible from the pilot plant experiments to upgrade an existing two stage aerobic-anaerobic wastewater treatment plant to reduce nitrogen from the liquid fraction of municipal wastewater so as to meet effluent quality standards without much additional volume and without amending the energy source for bioconversion of oxidised mineral nitrogen to gaseous forms.
Modelling of the anaerobic reactor in a biological phosphate removal process
Authors: Johansson Per , Carlsson Hans , Jönsson Karin
Published: May 2018

A kinetic model called SIPHOR has been developed for the biological phosphate removal process. The model is based on IAWQ Activated Sludge Model No. 1, and is divided into three sub-models, one anaerobic, one anoxic and one aerobic model. This paper describes the anaerobic model and results from a calibration and verification of the model on batch experiments performed with sludges from a full-scale plant in Helsingborg and a pilot-scale plant in Malmö. Both plants were run as UCT-processes. Anaerobic batch simulations have been used to identify the following constants, P-release rate (kp), fermentation rate (kferm), anaerobic hydrolysis rate (khx), P-release/VFA-storage (fpp) and the half-saturation coefficients, Kva and Kpop. The stoichiometric constant fpp has been found to be directly related to influent waste water. If acetate is added as carbon source, fpp has a value of 0.43, for primary hydrolysed waste water the value is 0.35 and for normal primary waste water, 0.30 in Helsingborg and 0.35 in Malmö. The rate of anaerobic hydrolysis has been found to be near zero in the anaerobic reactor.
Nitrifying bacteria in the influent to a wastewater treatment plant - influence and importance on nitrifying capacity
Authors: Sandén B. , Björlenius B. , Grunditz C. , Dalhammar G.
Published: May 2018

Cells of Nitrobacter sp. were enumerated in the influent to Bromma wastewater treatment plant using monoclonal antibodies in a competitive ELISA. By comparing this method with the most probable number technique we conclude that the immunological method is much more relevant for determining Nitrobacter sp. The amount of Nitrobacter sp. cells in the influent was measured once every second month during one year. Examinations concerning variations during one week and one day respectively were conducted. Finally a mass balance was constructed describing the amount of nitrifiers at different sites in the plant. The analysis showed that the amount of Nitrobacter sp. cells varies during the year but no obvious pattern could be observed. At the middle of an average week higher amounts were recorded. The major part of the nitrifiers was found in the biological unit and most of them have entered the wastewater treatment plant by the influent. Only small quantities were found in water from secondary clarifiers, filters and different sludge streams. 90% of the incoming cells of Nitrobacter sp. in the influent were captured in the plant. 5% of the bacteria were lost with the effluent and another 5% with the digested dry solids.
Characteristics of nitrification and denitrification of the media-anaerobic-anoxic-oxic process
Authors: Mishima Koji , Nishimura Takahiko , Goi Masahide , Katsukura Noboru
Published: May 2018

Widespread use of the anaerobic-anoxic-oxic process (AAO) has been expected because nutrients (nitrogen and phosphorus) can be removed simultaneously without any chemicals. The authors have been studying the nutrient removal performance of the media-anaerobic-anoxic-oxic process (M-AAO) using pilot plants, the media of which were suspending in an oxic tank (Mishima et al., 1995). The purpose of the M-AAO was to remove nutrients from sewage using a bioreactor half the size of the one used in the AAO process. The average water quality of the treated effluent of the M-AAO was 8.3 mg/l of T-N and 0.6 mg/l of T-P after a retention time of 8-9 hours in the bioreactor. According to the batch experimental results, 93% of nitrification at low water temperatures (below 15°C) was performed by the biofilm on the media. The specific nitrification activity of the biofilm was high showing 5-10 mg-N/g-MLSS/hr at low water temperatures. Media nitrification largely depended on the dissolved oxygen (DO). The denitrification rate of the activated sludge increased almost in proportion to BOD-SS loading. It was suggested that the phosphorus uptake in the anoxic tank was closely linked to denitrification.
Retrofit of biological nutrient removal process assisted by numerical simulation with activated sludge model no. 2
Authors: Kurata Gakuji , Tsumura Kazushi , Nakamura Syoichiro , Kuwahara Michio , Sato Akio , Kanaya Toshinori
Published: May 2018

In existing wastewater treatment plants that employ biological nitrogen and phosphorus removal processes, a low concentration of organic substrates in the influent wastewater has a destabilizing effect on the phosphorus removal process. Many efforts have been made to combat this problem, including reconstructing the process flow and improving operation and control systems. However, because the mechanism used for biological phosphorus removal is complex, it is difficult to establish effective empirical methods. For this paper, we constructed a simulator for the wastewater treatment process and tried to improve on current procedures, focusing on the planning, execution, and evaluation of methods of retrofitting existing WWTP with equipment for biological nutrient removal. The Shinnanyo WWTP uses the anaerobic/aerobic activated sludge process to remove nitrogen and phosphorus biologically. At this plant, however, the influent wastwwater has an insufficient concentration of organic substrates, thus decreasing the efficiency of the biological phosphorus removal. An analysis of organic consumption in the reaction tank on the simulation suggested that injecting primary sludge into the reaction tank would increase the efficiency of phosphorus removal process. Full scale experiments conducted at the plant verified the efficiency of this method. In addition, by shortening the A-SRT, ensuring that nitrification is not negatively affected, the efficiency of the nitrogen and phosphorus removal was significantly improved.
In situ analysis of nitrifying bacteria in sewage treatment plants
Authors: Wagner Michael , Rath Gabriele , Koops Hans-Peter , Flood Janine , Amann Rudolf
Published: May 2018

Autotrophic microbial nitrification is the key process in the removal of ammonia from wastewater. To avoid the limitations of traditional microbiological methods an in situ identification technique for ammonia- and nitrite-oxidizing bacteria was developed. Based on comparative sequence analyses we designed a collection of 16S ribosomal RNA-targeted oligonucleotide probes for all validly described members of the genusNitrobacter . Whole cell hybridizations of target and reference cells with fluorescent probe derivatives were used to determine the optimal hybridization stringency for each of the probes. These probes were applied together with a recently developed probe for important members of the genus Nitrosomonas for simultaneous identification of ammonia- and nitrite-oxidizing bacteria in natural and engineered systems. Ammonia-oxidizing bacteria were identified in situ in river water, epiphytic biofilms from eutrophic wetlands, oligotrophic biofilms, a nitrifying trickling filter biofilm as well as in all analyzed nitrifying activated sludge samples. In none of these samples could Nitrobacter cells be detected in situ. However, all hitherto describedNitrobacter species and a strain of Nitrobacter sp. isolated from one of the analyzed nitrifying activated sludge samples showed bright hybridization signals with all Nitrobacter specific probes. Possible reasons for the absence of in situ detectable Nitrobacter cells are discussed.
Running-in of the nitrification process with and without inoculation of adapted sludge
Authors: Sinkjær O. , Thirsing C. , Harremoës P. , Jensen K. F.
Published: May 2018

Comprehensive pilot plant studies have been conducted over a period of six years in connection with the upgrading of the Lynetten Wastewater Treatment Plant to nutrient removal. The studies showed already at an early state that the nitrification process was inhibited. Short-term and long-term effects in connection with the running-in of the nitrogen removal processes, were investigated in two situations,- with and without inoculation with adapted sludge from a reference pilot plant. The floc formation, sludge accumulation and the establishment of full nitrification and denitrification developed in the same way in the two tests. The development of the nitrification capacity, however, differed to a significant extent. Compared with the nitrification capacity at the reference plant, the nitrification capacity in the test involving inoculation was reached approximately 2 month after the start-up as opposed to 7.5 months in the test without inoculation.
Denitrification of nitrite in a two-phase fluidized bed bioreactor
Authors: Hirata A. , Meutia A. A.
Published: May 2018

Denitrification of nitrite-nitrogen carried out experimentally in an anoxic two-phase fluidized bed bioreactor is described, and the characteristics of the biological treatment were also theoretically studied. Methanol was used as the carbon source, and nitrite-degrading bacteria immobilized on CB particles were employed. A method for evaluating the characteristics of the biological treatment is proposed. Within the range of the experiment, the results show that denitrification of nitrite-nitrogen could be approximated by Monod-type reaction kinetics, characteristic values for the biological treatment of Ku = 5.0 kg-N·kg−1-VS·d−1 and Ku/Km = 23.8 m3·kg−1-VS·d−1 being obtained. There was good correlation between the experimental results and the calculated curves. A maximum volumetric denitrification rate for nitrite of 18.7 kg-N·m−3·d−1 was achieved, this high value demonstrating the high efficiency of an anoxic two-phase fluidized bed bioreactor to denitrify nitrite-nitrogen.
Bulking and foaming in BNR plants in Johannesburg: problems and solutions
Authors: Pitman Anthony R.
Published: May 2018

In this paper almost twenty years of experience with sludge bulking and foaming/scumming problems in extended aeration and BNR plants in Johannesburg is summarised. Various reasons for these problems are proposed and remedial measures discussed. A general hypothesis for bulking and scumming in BNR and other plants is proposed and design features to minimise these problems recommended. Practical experience with a full scale plant incorporating some of these features is described.
An expert system for selecting and sequencing wastewater treatment processes
Authors: Yang Chin-Tien , Kao Jehng-Jung
Published: May 2018

Wastewater treatment system design involves selecting and sequencing various treatment processes. The design becomes complicated when a large number of processes and various contaminants are considered. In this work, an expert system is developed to find an appropriate treatment process design for a given waste stream. The knowledge base of the system is established with a treatability database to select suitable treatment techniques for specified contaminants and concentration levels. Also, a preliminary fuzzy logic based approach is proposed to express the user's preference of treatment techniques in a linguistic form. The preference is defined on the basis of the treatment efficiency and the cost of a technique. The system is intended to serve as a decision support tool for a designer to determine optimal treatment process sequences for various contaminants at different concentration levels. Finally, the developed system is demonstrated in a case study for a chemical processing waste stream.
Sludge production characteristics of small-scale wastewater treatment facilities using anaerobic/aerobic biofilm reactors
Authors: Inamori Yuhei , Takai Tomotake , Yamamoto Yasuhiro , Katagai Nobuyoshi , Sankai Toshihiro , Hirata Akira
Published: May 2018

Sludge production characteristics were investigated in many on-site small-scale wastewater treatment facilities used to treat domestic wastewater of about 1.25m3/day. Two popular types have been used in experiments for several years; one was an anaerobic bed reactor with constant flow-rate control system followed by aerobic bio-filtration reactor CFR type facility), and the other was an aerobic bed reactor with plug-flow stream followed by aerobic biofilm reactor (PFS type facility). Circulation ratio was set at 0 and 4. From the results obtained, lower sludge production rates were observed in CFR type facilities. Furthermore, it was suggested that a promotion of sludge decrease occurred in facilities with high denitrification activity at circulation ratio of 4. The results from experiments with different SS loading rates in laboratory-scale reactors suggested that at higher loading rates, the produced sludge was greater on account of the decrease of nitrification activity even on a circulating operation.
Tracer studies of a gravel bed wetland
Authors: Shilton Andy N. , Prasad Julius N.
Published: May 2018

Current rational design methods for subsurface flow wetlands idealise these systems as plug flow reactors. This assumption ignores the existence of longitudinal dispersion, short-circuiting, stagnant zones and so on. This paper reports on a series of three tracer experiments performed on a gravel bed wetland with a design hydraulic retention time of four days in order to study its hydraulic characteristics. The results present the hydraulic retention time distributions. The first tracer run using a single point inlet source had a mean time of 2.71 days. The second and third had the influent distributed across their width using an inlet manifold and yielded mean retention times of 3.47 and 3.41 days respectively. Further interpretation of these results indicates that the current plug flow assumption used in design can result in over estimation of treatment efficiency.
Development of a biofilter using an organic medium for on-site wastewater treatment
Authors: Talbot Pierre , Bélanger Ginette , Pelletier Martin , Laliberté Gilles , Arcand Yves
Published: May 2018

In recent years, many authors identified peat-based systems as a very promising technology for on-site wastewater treatment. In that context, Premier Tech has been working, since 1988, on the development and commercialization of a peat-based biofilter suitable for on-site wastewater treatment. This research and development programme comprised three major phases: an experimental phase where one type of peat out of 21 was chosen to be used in biofilters; a second phase where two prototype biofilters were installed in the field and their performances followed for 5 years; and a third phase where 4 biofilters were installed in order to demonstrate the adaptability of the system. The results obtained in this three-phase programme allowed the introduction on the market of a compact, reliable, and easy to operate biofilter requiring little investment from the home owner. In this paper an overview of the research and development programme carried out in the last 8 years in relation to on-site wastewater treatment is given.
The influence of fibres on the structure of thermally dried sludge product
Authors: Lowe Paul , Brown Michael , Hudson Kathleen
Published: May 2018

There appears to be a limited experience world-wide in the application of thermal drying technology to processing raw undigested sludge. This limited experience has shown that the products from raw sludge processing have a much lower bulk density than those from digested sludge. The apparent reason for this phenomenon demonstrated by this work, is the high concentration of fibres in the raw undigested sludge. Different sludges show varying degrees of fibre concentration with a decrease in fibre content as the proportion of secondary sludge increases. The relationship between the bulk density of the product and the fibre content are given and this shows that as the fibre content increases the bulk density of the product will fall. It is recommended that a compaction/pelletisation stage is included in the process stream for high fibre sludges.
Development of adsorbent/catalyst from municipal wastewater sludge
Authors: Jeyaseelan S. , Lu Gao Qing
Published: May 2018

The objective of this research work is to investigate the possibility of using sewage sludge as a source to produce adsorbent for odorous gas removal. The basic method of adsorbent preparation is pyrolysis in nitrogen gas. The effects of heating temperature and resident time are investigated. Treatments such as drying in air at low temperature and soaking in chemicals prior to pyrolysis are attempted. The prepared adsorbents are characterized by an automatic surface area porosimeter in terms of BET surface area, pore size distribution. The highest BET surface area achieved is 309 m2/g, where the sludge is soaked in 5M zinc chloride solution and dried at low temperature before heating to 650°C for two hours. Laboratory tests at 17.5 ppm H2S concentration show that the sludge-derived adsorbent has an H2S adsorption capacity 25% that of a commercial activated carbon (Calgon IVP 4×6) over 15 hours of duration.
The watershed protection approach: a framework for ecosystem protection
Authors: Davenport Thomas E. , Phillips Nancy J. , Kirschner Bruce A. , Kirschner Lyn T.
Published: May 2018

From the ecosystem protection cocept the watershed protection approach is derived and its implementation by EPA outlined.
Implementing the world bank's water resources management policy: a priority on toxic substances from nonpoint sources
Authors: Duda A. , Nawar M.
Published: May 2018

Compared to point source discharges, nonpoint or diffuse source contaminants cause more widespread degradation of surface and groundwater quality worldwide. While it is in the economic interest of all nations to establish programs for abatement of nonpoint source pollution, priorities must be established, and particularly dangerous contaminants that are hazardous, toxic or radioactive by nature deserve the highest priority. This paper makes the case for why these dangerous contaminants from nonpoint sources must urgently be addressed. The nature and significance of these contaminants are reviewed and the complex, multimedia sources of the releases are identified, including “donations” and export of hazardous materials to developing countries. Examples are cited from North America, Europe, the former Soviet Union and Asia of the enormous extent of contamination of soil, groundwater, surface water, fish, and wildlife from these persistent toxic chemicals. They are persistent in the environment, build up in fish through food chains, and contaminate human food. These chemicals mimic hormones and disrupt the development of offspring as they cause complex reproductive, metabolic, neurological, and behavioral changes as well as cancer risks. A new Water Resources Management Policy recently adopted by the World Bank places a priority on pollution prevention measures for industry, abatement of nonpoint source discharges, development of effective government regulatory institutions, and remediation/restoration of contaminated sites and ecosystems. Relevant elements of the policy are presented. In addition, the importance of economic instruments (polluters pays funds) for waste site cleanup and remedial action requirements being included during privatization of industrial sites are stressed.
Source apportionment of riverine nitrogen transport based on catchment modelling
Authors: Wittgren Hans B. , Arheimer Berit
Published: May 2018

Source apportionment of river substance transport, i.e. estimation of how much each source in each subbasin contributes to the river-mouth transport, is a vital step in achieving the most efficient management practices to reduce pollutant loads to the sea. In this study, the spatially lumped (at sub-catchment level), semi-empirical PULSE hydrological model, with a nitrogen routine coupled to it, was used to perform source apportionment of nitrogen transport in the Söderköpingsån river basin (882 km2) in south-eastern Sweden, for the period 1991–93. The river basin was divided into 28 subbasins and the following sources were considered: land leakage from the categories forest, arable and ley/pasture; point sources, and; atmospheric deposition on lake surfaces. The calibrated model yielded an explained variance of 60%, based on comparison of measured and modelled river nitrogen (Total N) concentrations. Eight subbasins, with net contributions to the river-mouth transport exceeding 3 kg ha−1 yr−1, were identified as the most promising candidates for cost efficient nitrogen management. The other 20 subbasins all had net contributions below 3 kg ha−1 yr−1. Arable land contributed 63% of the nitrogen transport at the river mouth and would thus be in focus for management measures. However, point sources (18% contribution to net transport) should also be considered due to their relatively high accessibility for removal measures (high concentrations). E.g., the most downstream subbasin, with the largest wastewater treatment plant in the whole river basin, had a net contribution of 16 kg ha−1 yr−1. This method for source apportionment may provide authorities with quantitative information about where in a river basin, and at which sources, they should focus their attention. However, once this is done, an analysis with higher resolution has to be performed in each of the interesting subbasins, before decisions on actual management measures can be taken.
Prediction of runoff pollutant load considering characteristics of river basin
Authors: Ichiki Atsushi , Yamada Kiyoshi , Ohnishi Toshiyuki
Published: May 2018

The objectives of this study are to establish a runoff model and show profiles of pollutant runoff by simulating the change in runoff load with variance in the characteristics of river basins (i.e. population, urban area, rate of sewerage, etc.). The model, hereinafter referred to as “MACRO MODEL”, consists of three main sections. The first one shows pollutant runoff from point sources taking into consideration the sedimentation of pollutants in sewers. The second and third ones show pollutant runoff from nonpoint sources in an urban and rural area taking land use into consideration. Since it was proved that MACRO MODEL could simulate runoff load accurately enough to predict profiles of pollutant runoff, it has become possible to estimate the effect of characteristics of a river basin on pollutant runoff. As a result, some available knowledge concerned with the environmental management of water was obtained by using MACRO MODEL.
Impact of diffuse pollution on water quality of the Vltava River (Slapy Reservoir), Czech Republic
Authors: Procházková Ludmila , Blažka Pavel , Kopácek Jirí
Published: May 2018

This study on long-term (36 years) changes of water chemistry in the Vltava River is based on regular monitoring of the Slapy Reservoir, which has a large heterogenous catchment. Ionic concentrations doubled at constant ratio of cations, while the equivalent ratio of anions of strong acids (SO42−, NO3−, Cl−) to hydrogen carbonate increased more than twice between 1959 and 1990. Nitrate levels increased seven times, reflecting mainly rate of fertilization and atmospheric N deposition. Diffuse sources were dominant in N discharge from the basin (at least 60-80%) throughout the period, in extremely dry years the importance of point sources increased. A sharp decline in the fertilizer application since 1990 due to economic changes in the Czech Republic and also decreased emissions of sulphur in Europe has resulted in the slow recovery of water quality.
Monitoring approach to evaluate water quality of intermittent lake Cerknica
Authors: Gaberšcik Alenka , Urbanc-Bercic Olga
Published: May 2018

The article presents the monitoring approach that is used to evaluate water quality of the intermittent Lake Cerknica and its tributaries. The results show that specific nature of Lake Cerknica influences the extent of the pollution. When regular gradual changes in water level occur the pollution effects can be buffered. The consequence of immediate decrease of water level is severe pollution of the main flow. The springs of the carstic tributaries are already loaded with pollutants which are transferred through underground pathways from neighbouring regions.
An evaluation of a dynamic model of the secondary clarifier
Authors: Jeppsson Ulf , Diehl Stefan
Published: May 2018

The main objective of the paper is to support and illustrate recent theoretical results on the mathematical modelling of the secondary clarifier. A new settler model is compared with a traditional layer model by means of numerical simulations. Emphasis is put on the numerical solution's ability to approximate the analytical solution of the conservation law written as a non-linear partial differential equation. The new settler model is consistent in this respect. Another important conclusion is that a layer model dividing the settler into only ten layers (normally used in settler models) is too crude an approximation to capture the detailed dynamic behaviour of the settler. All simulations presented are performed with the settler models coupled to the IAWQ Activated Sludge Model No. 1.
A model for predicting nitrous oxide production during denitrification in activated sludge
Authors: Wicht H.
Published: May 2018

To examine the importance of certain conditions on the production of nitrous oxide during denitrifications batch experiments with activated sludge were conducted. With the obtained parameters and a Monod kinetics based model the nitrous oxide concentrations in a CSRT were calculated. The influence of temperature, pH, nitrate influent concentration, readily biodegradable COD influent concentration, H2S and oxygen inhibitor concentrations are discussed. The presented model helps in understanding some previously described phenomena of nitrous oxide production in wastewater treatment plants.
Microbial floc stabilization and preparation for structural analysis by correlative microscopy
Authors: Droppo Ian G. , Flannigan Derrick T. , Leppard Gary G. , Liss Steven N.
Published: May 2018

In the analysis of microbial flocs from activated sludge it is important to stabilize these structures and their components for structural studies sufficiently to assess, minimize and conceptually balance artifacts, particularly during manipulation. By employing multi-technique stabilization and immediate preservation it is possible to analyze a single sample by correlative microscopy (conventional optical microscopy (COM), scanning confocal laser microscopy (SCLM), and transmission electron microscopy (TEM)). This approach minimizes variability associated with multiple sampling. Floc samples were collected using plankton chambers consisting of reservoirs with a removable circular microscope slide. Flocs which come to rest on the slide are stabilized within low melting point agarose. The solidified gel is a clear, highly porous and resilient medium amenable to further staining, washing, sub-sampling or direct microscopic analysis. Stabilization in agarose was found not to significantly influence floc size distribution. The use of agarose was found to be compatible with SCLM and TEM techniques and minimized perturbations. Agar-embedded samples were easily infused with Nanoplast, a hydrophilic melamine resin, which stabilizes material in its natural state. This facilitates the ultrastructural analysis of the three-dimensional fibrillar architecture of the floc matrix. The matrix is found to consist of complex pores bounded by fibrils of 4-6 nm diameter.
Effect of nickel(II) on the biomass yield of the activated sludge
Authors: Gökçay Celal F. , Yetis Ulku
Published: May 2018

Biomass yield of microorganisms is important in applied microbiology since it is the ultimate factor determining the amount of product produced regardless of whether product is growth-linked or not. In the case of environmental microbiology the opposite is true and minimizing the biomass produced, or the sludge in the relevant jargon, often is the prime goal. In this paper, a unique means of manipulating the microbial biomass yield of a heterogeneous culture to fulfil either of the two goals is presented. 5.0 mgl−1 Ni(II) in the feed composition to a completely mixed, once- through, activated sludge was found to induce the observed biomass yield of the microbial culture developed from sewage. As compared with the base-line study without Ni(II), where the reactor received synthetic wastewater only, true biomass yield was found to have increased along with the increased decay constant with the net effect of lowering observed biomass yield drastically at lower dilution rates and increasing it over that observed in the base-line study at higher dilution rates. At 10.0 mgl−1 influent Ni(II) concentration the culture conditions almost reverted back to the base- line study and at 25 mgl−1 Ni(II) concentration a truly steady-state condition could not be attained.
A novel concept for evaluation of biofilm adhesion strength by applying tensile force and shear force
Authors: Ohashi Akiyoshi , Harada Hideki
Published: May 2018

A novel methodology is proposed in this study to evaluate biofilm adhesion strength in two different ways: by measuring detached biomass caused by tensile force and by shear force. Tensile force was provided by centrifuging biofilm-attached plates installed on rotary tables. Shear force was provided by colliding biofilm-attached plates by gravity. Test biofilms consisting of denitrifiers were formed on the flat surfaces of square (25 cm2) plates that had been submerged in a rectangular open-channel reactor. The detachment tests revealed that, although biofilm adhesion strength was relatively high at the earlier growth stage, it drastically decreased at the later stage. The most weakened location toward biofilm depth was observed at the substratum surface, at which the adhesion strength by tensile force dropped from a several Pa to below 1 Pa as biofilms became aged. The adhesion strength by shear force was all the time more than 100 times as large as that by tensile force, even though having a similar behavior. The proportion of cavity, i.e., biofilm-absent area at the biofilm/substratum interface, increased as biofilms became mature. Cavity formation was strongly responsible for lessening the adhesion strength. It is suggested that biofilm slough-off is caused by the decline of adhesion strength by tensile force rather than by shear force.
Comparative toxicity of long-chain fatty acid to anaerobic sludges from various origins
Authors: Hwu Ching-Shyung , Donlon Brian , Lettinga Gatze
Published: May 2018

Seven anaerobic sludges were screened in order to obtain the most suitable methanogenic inoculum for the anaerobic treatment of wastewaters containing long-chain fatty acids (LCFA). The selection was made on the basis of the toxicity of a model compound, oleate, to acetoclastic methanogens in different sludges. The effects of three biological factors, sludge origin, specific acetoclastic methanogenic activity and sludge adaptation to lipids, and a physical factor, specific surface area of sludge, on the degree of toxicity were investigated and compared. Values of the fifty percent inhibition concentration (IC50) of oleate obtained from 40°C batch toxicity tests ranged from 0.26 to 3.34 mM for the various sludges examined. It was found that the toxicity of oleate to anaerobic sludges was not dependent upon the three biological factors. Instead, it was closely correlated to the specific surface area of sludge. Suspended and flocculent sludges, which have higher specific surface area, suffered much greater inhibition than did granular sludges. This paper suggests the use of granular sludges as appropriate inocula for reactors treating lipids (fats, oils and greases) wastewaters, to decrease the toxic impact from their hydrolysis products-LCFA.
Mathematical modelling for supporting scale-up of an anaerobic wastewater treatment in a fluidized bed reactor
Authors: Schwarz Alexander , Yahyavi Bahram , Mösche Marek , Burkhardt Claus , Jördening Hans-Joachim , Buchholz Klaus , Reuss Matthias
Published: May 2018

The paper deals with a mathematical model for anaerobic treatment of waste water from sugar industry which has been developed for supporting the scale-up of a fluidized bed reactor. The dynamic model is based on material balance equations for substrates and products in gas and liquid phase. The effects taken into account are the biological degradation steps including chemical equilibria and mass transport between gas and liquid phase as well as convection and dispersion. Axial gradients of pH-values are calculated from a charge balance. Simulation results show reasonable agreement with measured gradients of substrates and pH in a 10 m3 fluidized bed reactor. For a new 500 m3 fluidized bed reactor simulations are performed to study the effects of increased hydrostatic pressure and increased ratio of feed to recirculation rate on the pH-values at the bottom of the reactor. The results indicate that for high COD-loading rates stationary pH-gradients may have significant influence upon the outcome of the process.
Spectrophotometric monitoring of biofouling
Authors: Jacobs Liesel , De Bruyn Elize E. , Cloete Thomas E.
Published: May 2018

The monitoring of biofouling is continuously evolving with new and better techniques being developed all the time. The major drawback of the currently used techniques is that these methods are complicated and time-consuming, involving culturing and counting of attached organisms. A continuously circulating batch culture system was therefore designed to study biofouling spectrophotometrically. Absorbance of bacteria attached to a glass tube was compared with direct counts done on DAPI-stained bacteria attached to 3CR12 coupons. Direct measurements of absorbance correlated well with the total counts obtained using the DAPI technique (r2=0.925). Spectrophotometry proved to be an easy, inexpensive and reliable alternative to techniques requiring laborious counting of microorganisms, for example the DAPI technique, for quantification of biofouling.
Modeling and risk analysis of bromate formation from ozonation of bromide-containing waters
Authors: Song Rengao , Minear Roger , Westerhoff Paul , Amy Gary
Published: May 2018

Empirical bromate formation models were developed from batch ozonation data to simulate the effects of important water quality characteristics and treatment processes on bromate formation. Bromate formation was favored at high pH, bromide concentration, alkalinity, and ozone dose. On the other hand, increasing DOC and ammonia concentration decreased bromate formation. Validation of the bromate models demonstrated that the models accurately simulated bromate formation. Risk analysis of bromate formation was performed on 5 utilities in which ozone was used, and it was concluded that under typical ozonation conditions, the associated risk related to bromate formation could be as high as 10−3.
Modeling of heavy metals in a reservoir with diffusive bottom layer
Authors: Tkalitch P. V. , Chen W. , Tay J. H.
Published: May 2018

A model of heavy metal kinetics in the well mixed reservoir with respect to vertical diffusion in the active bottom layer is presented. The model incorporates the mechanisms of a heavy metal reaction process between “overlying water-suspended sediments - interstitial water - bottom sediment”. Application of long-term modeling is provided to simulate the self-cleaning abilities of the Kranji Reservoir. The adsorption rate of Zn on bottom sediments was determined by a modified batch test. The analytical results demonstrate the high retention and concentration of Zn in the interstitial water, which indicates the importance of including the interstitial water quality in the assessment of potential ecological effects. The numerical simulations show the influence of the bottom diffusive layer on Zn long-term dynamics in the aquatic system.
A basic study on comprehensive water indices using glass fiber filters and a spectrophotometer
Authors: Nakamura Keigo , Shimatani Yukihiro
Published: May 2018

Chemical and biotic indices of water quality have some problems. They need a lot of time to measure and technology, therefore we considered evaluating water color objectively and quantitatively. This method is as follows; after filtering sampling water on the glass fiber filter, absorbance spectrum of this filter is measured by the spectrophotometer. This method does not need, technology and cost. We surveyed the relation between absorbance spectrum and conventional water indices. As a result, this method is very effective to evaluate water quality change from the water color point of view abd it can also evaluate turbidity and Chlorophyll-a very easily. We expect this method to lead to a new water quality index.
A theoretical study on operational condition of hypolimnetic aerators
Authors: Nakamura Y. , Inoue T.
Published: May 2018

A theoretical basis for the operational condition of hypolimnetic aerators is described. The widely observed increase in hypolimnetic oxygen demand during aeration is ascribed to enhanced sediment oxygen demand due to induced circulation currents. The present model enables quantitative prediction of dissolved oxygen and phosphate concentrations during hypolimnetic aeration. Simple mass balance in the hypolimnoin shows a necessary condition to halt phosphate release. A time scale of changes in oxygen concentration is also discussed. These results will assist in designing an aerator and selecting an optimum operational condition.
Analyses of planktonic ecosystem structure in coastal seas using a large-scale stratified mesocosm: a new approach to understanding the effects of physicsl, biochemical and ecological factors on phytoplankton species succession
Authors: Harada Shigeki , Watanabe Masataka , Kohata Kunio , Ioriya Teru , Kunugi Masayuki , Kimura Toshihiko , Fujimori Shiro , Koshikawa Hiroshi , Sato Kazumi
Published: May 2018

Mesocosms (marine enclosures) have advantages in ecosystem analysis because they are mass-conserved systems, but with biochemical and ecological conditions similar to those of the surrounding water column. Furthermore, our mesocosm (5m in diameter and 18m in depth) developed in the Seto-Inland Sea, Japan (Watanabe et al., 1995) has vertical mixing system to control its physical conditions. Two independent experiments in 1989 and 1991 both in summer showed a high ability to reproduce the physical and biochemical conditions of the water column, underpinning the ability to design desired experimental yet near-natural conditions using the mesocosm. The dominance and population shifts of centric diatoms, pennate diatoms and flagellates in the experiments were explained by the effects of changing nutrient (N, P and Si) availability, the features of the phytoplankton species present and grazing by zooplankton. Two implications for nutrient management to control phytoplankton composition at the site were obtained: 1) Si depletion leads to shifts of dominant species from larger to smaller diatoms or flagellates; and 2) stocks of N and P below the nutricline remaining after depletion of those in the surface layer lead to the dominance of flaggellates, the latter being difficult to observe within small scale experimental systems.
Testing an artificial beach system for removal of pollution in a coastal zone
Authors: Xu K. Q. , Sakaguchi Y. , Nishimura O. , Tanaka Y. , Sudo R.
Published: May 2018

The developmental activities and utilizations of Japanese coastal seas have been increased recently. Consequently, the production of coastal fisheries, especially of those in enclosed seas, are considerably affected by artificial impacts such as reclamation from the sea and increased pollution load. The objective of this paper is to propose a new ecotechnological method to recover the polluted coastal environment by using an artificial beach system. An artificial beach (5 m × 10 m) was constructed in the Matsushima Bay facing the Pacific Sea, about 300 km northeast from Tokyo. The area was polluted by fishery production and untreated wastewaters from rural district. The major merits of this system are simplicity of the structure, energy-free operation, capability to use tidal current cycle effectively, and ease of maintenance. The results of field investigation indicated that rapid removals of turbidity, suspended solids, phosphorus and ammonium nitrogen by the artificial beach system were achieved. The removal rate of total organic carbon was high because of the retention of the particulate matters. These performances were related to physical and biological filtration through the artificial beach system. It suggests that restoration of polluted coastal area may be expected using this artificial beach system.
Nitrogen removal in seawater using nitrifying and denitrifying bacteria immobilized in porous cellulose carrier
Authors: Sakairi Maria Antonina Catalan , Yasuda Kimiaki , Matsumura Masatoshi
Published: May 2018

Nitrogen compounds in seawater are now contributing to serious water pollution problems. In this study, continuous removal of nitrogen in seawater using nitrifiers and denitrifiers immobilized in macro-porous cellulose carrier “AQUACEL” was examined. In nitrification, the nitrite oxidation step becomes the rate limiting step unless an influent inorganic carbon (g) / influent NH4-N (g) ratio (IC/NH4-N) of 7.23 is maintained. This is equivalent to an influent alkalinity (g) / influent NH4-N (g) ratio (ALK/NH4-N) of 8.25. Nitrite oxidizers were also sensitive to change in NH4-N loading. Unlike other biological removal systems used for seawater, trace element solution (containing Mo, Cu, Mn, Co, Fe, etc.) was added only at a high NH4-N loading rate of 0.65 kg-N/m3/carrier/d (at NH4-N concentration of 40 g/m3) and acclimatizing period was short, i.e., about a week. The maximum NH4-N loading rate obtained which removed 99 to 100% of the nitrogen compounds, was 1.30 kg-N/m3/carrier/d. For completion of denitrification, an influent phosphorus (g) per influent NO3-N(g) ratio (P/NO3-N) of 0.03 was required. Trace element solution (containing Fe, Mn, Mo, etc.) was doubled to 0.02% at NO3-N concentration of 560 g/m3. In addition, methanol concentration must be maintained at 30% more of the theoretical value of carbon concentration requirements. Copper enhanced nitrite reduction at an influent Cu(g) per influent NO3-N(g) ratio (Cu/NO3-N) of 0.002. The maximum allowable NO3-N loading rate necessary to remove about 99 to 100% of the nitrogen compounds was 20.79 kg-N/m3/carrier/d. This study reveakls that the AQUACEL system has high nitrifying and denitrifying capacities. The nitrogen loading capacity of denitrification is about ten times that of nitrification and is comparable to that of freshwater which also employed the AQUACEL system. In contrast, nitrogen loading capacity of nitrification is about six times less than that of freshwater, which indicates a higher sensitivity of nitrifiers to salinity. This indficates high sensitivity of the immobilized nitrifying bacteria to salinity. Morphological observations show that the ammonia oxidizers are a mixed culture ofNitrosomonas spp . and Nitrosovibrio spp., while the nitrite oxidizer is a Nitrobacter spp. The immobilized denitrifying bacteria showed similar morphological characteristics to the Hyphomicrobium spp.
Tricaprylmethylammonium bentonite compexes as adsorbents for benzene, toluene, ethylbenzene and xylene
Authors: Man-Chi Lo Irene , Lee Cheng-Hao , Liljestrand Howard M.
Published: May 2018

An organoclay complex was synthesized by placing quaternary ammonium compound on low-charge bentonite (CEC = 90 meq/100 g) through cation exchange reaction. This kind of compex was examined for its ability to adsorb non-polar hydrocarbons such as benzene, toluene, ethylbenzene and o-xylene (BETX). The organic cation used in this study was the tricaprylmethylammonium (TCMA) ion which contains long-chain alkyl (tricapryl) groups of high hydrophobicity. The characteristics of TCMA-bentonite are presented from the results of Infrared red spectrum.

The high adsorption of benzene, toluene, ethylbenzene and o-xylene from aqueous solutions by TCMA-bentonite is found to be related to their hydrophobicity and water solubility. Free swell tests are also presented to contrast the swelling properties of bentonite with and without quaternary ammonium cations. The laboratory scale tests indicate that TCMA-bentonite could be used as an adsorbent to enhance the purification of aromatic hydrocarbon-contaminated water or act as a liner material for removing non-polar contaminants.
Water reuse for sludge management and wetland habitat
Authors: Reed Sherwood , Parten Susan , Matzen Gary , Pohren Randy
Published: May 2018

The Hornsby Bend Sludge Management Facility provides centralized stabilization and dewatering for the sludges from several wastewater treatment plants serving the City of Austin, TX. This facility has been utilizing water reuse for a number of years via land application of the treated leachate and run off from the site, on crop land. The treatment sequence included aerated and facultative lagoons and a large greenhouse structure containing water hyacinths. Plans are under development to modify and upgrade the sludge treatment facilities, these will include mechanical dewatering. The reuse of this treated filtrate as wash water in the facility is intended for future operations. This paper describes a conceptual plan for treatment of this filtrate by conversion of one of the existing lagoons to a wetland. A significant portion of this wetland will be developed for optimum habitat value. Public access to this wetland can be provided for observation of birds and other wildlife.
UV design: comparison of probabilistic and deterministic design approaches
Authors: Tchobanoglous George , Loge Frank , Darby Jeannie , Devries Marvin
Published: May 2018

Deterministic and probabilistic approaches to the design of ultraviolet (UV) disinfection systems are reviewed and discussed. Field data that must be collected to apply each method are identified. An empirical model to predict UV disinfection performance is presented and discussed. The advantage of the probabilistic approach is that the variability in the wastewater characteristics, the variability in the field test data, and the statistical nature of the discharge requirements are reflected in the in design of the UV system.