bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption of micropollutants onto fibrous activated carbon: association of ultrafiltration and fibers
Authors: Brasquet C. , Roussy J. , Subrenat E. , Le Cloirec P.
Published: May 2018

The adsorption of polluted solutions is performed by different kinds of activated carbon: grains, powder and fibers (cloth or felt). The adsorption is carried out in a batch reactor. Classic models are applied and kinetic constants are calculated. Results showed that the performance of fiber activated carbon (FAC) is significantly higher than that of granular activated carbon (GAC). Moreover, FAC's adsorption capacities of phenol are greater than GAC's. Therefore the application of FAC adsorbers may lead to smaller adsorption reactors. The breakthrough curves obtained with FAC adsorbers are particularly steep, suggesting a smaller mass transfer resistance than GAC. The adsorption zone in the FAC bed is about 3.4 mm and is not dependent on the flow rate within the range 0.67 - 2.07 m.h−1. The selectivity of the FAC between different size of soluble molecules is shown. Then, an Ultrafiltration (UF) membrane is coupled with FAC to remove successively macromolecules (humic substances) and phenols present together in an aqueous solution. This new and original approach to a water treatment compact process successfully put to use. Industrial developments are put forward.
Competitive adsorption of trace organics on membranes and powdered activated carbon in powdered activated carbon-ultrafiltration system
Authors: Kim J.-S. , Lee S.-J. , Yoon S.-H. , Lee C.-H.
Published: May 2018

An activated carbon adsorption model was developed to predict final permeate concentrations of a target trace organic compound (o-dichlorobenzene, DCB) under the variable influent concentration in powdered activated carbon-ultrafiltration (PAC-UF) system for drinking water production. The results were then compared with experimental DCB concentrations both in bulk and permeate. In the adsorption period, the DCB concentrations both in bulk and permeate were always lower than the predicted ones while the permeate concentrations were lower than the bulk ones regardless of membrane materials used and PAC doses. On the other hand, during the desorption period, the experimental values were higher or lower than the predicted ones depending on PAC dose and membrane used. The competitive adsorption and/or desorption of DCB between PAC and membrane itself resulted in this discrepancy, and this trend was more pronounced in a hydrophobic membrane.
Application of new criteria to control sediment problems in combined sewers in Poland
Authors: Blaszczyk Pawel , Ashley Richard M.
Published: May 2018

The Polish criteria for design and operation to control sediments in combined sewers may now be replaced to reflect new knowledge. A series of field investigations have been carried out to examine the occurrence and nature of sediments in sewers in Warsaw. Using the results of these studies and new UK approaches to the control of sedimentation in sewers, new simplified criteria have been defined based on different modes of sediment transport and relative sewer sizes.
Biodegradation of chlorophenols by immobilized pure-culture microorganisms
Authors: Chih-Jen Lu , Chi-Mei Lee , Chiou-Zong Huang
Published: May 2018

The biodegradation of phenol and chlorophenols by immobilized pure-culture cells was conducted by a series of batch reactors. The microorganisms used in this study were Pseudomonas putida, Psuedomonas testosteroni, Pseudomonas aeruginosa, and Agrobacterium radiobacter. All four species showed the ortho-cleavage pathway to metabolize chlorophenols. Among the four species, P. testosteroni, P. putida, and P. aeruginosa could effectively remove phenol at 200 mg/l. P. testosteroni could effectively remove 2-chlorophenol at 10mg/l. However, the other three species, P. putida, P. aeruginosa, and A. radiobacter, could not effectively remove 2-chlorophenol. Although 3-chlorophenol is a recalcitrant compound, P. testosteroni also could rapidly metabolize 3-chlorophenol at 10 mg/l. The removal of 4-chlorophenol at 10 mg/l by P. testosteroni reached 98% within one day. P. aeruginosa and A. radiobacter also could metabolize 4-chlorophenol after 2 and 7 days of lag period, respectively.
Role of peroxidase and chitosan in removing chlorophenols from aqueous solution
Authors: Ganjidoust Hossein , Tatsumi Kenji , Wada Shinji , Kawase Mitsuo
Published: May 2018

Chlorophenols removal from industrial wastewater by horseradish peroxidase and coagulant was investigated. It was found that an enzymatic reaction time of less than one hour was enough for the reaction to reach 95% completion. Chitosan, which is a natural coagulant, was an effective coagulant as compared to mineral coagulants such as aluminum sulfate (ALUM), hexamethylene diamine epichlorohydrin polycondensate (HX), polyacrylamide (PAM), and polyethyleneimine (PEI). A combination of 0.4 U/mL peroxidase to 2 ppm chitosan along with 0.8 mM of hydrogen peroxide resulted in over 95% chlorophenol removal from aqueous solution.
Analysis and evaluation of heavy metal uptake and release by insoluble starch xanthate in aqueous environment
Authors: Chaudhari Sanjeev , Tare Vinod
Published: May 2018

This paper presents the finding of the investigation on the behaviour of metal removal and recovery using insoluble starch xanthate. It is hypothesized that metal-xanthate interaction is a net result of the two simultaneous reactions - (i) reversible complexation of metal with xanthate groups, and (ii) decomposition of the xanthates. The affinity, and also the selectivity sequence of metals for xanthate groups is postulated to follow the reverse order of metal-ethyl xanthate solubilities. Further decomposition of xanthates is viewed advantageous for metal recovery. Metal recovery is predicted to follow reverse order of metal-selectivity for xanthates. Results of the laboratory experiments carried out on insoluble starch (corn) xanthate are used to test the hypothesis. The selectivity of metals for ISX follows the sequence Hg(II)>Cu(II)>Cd(II)>Ni(II) which correlates with metal-ethyl xanthate Ksp values. The recovery of metals from metal-ISX sludge is attempted by using mineral acids (hydrochloric, sulfuric and nitric), oxidizing agents (chlorine solution and hydrogen peroxide) and eluting agent (EDTA). The results of metal removal and recovery are in accordance with the proposed hypothesis.
Municipal effluent standards in the Czech Republic
Authors: Wanner Jirí , Cech Jakub S. , Kos Miroslav , Barchánek Michael
Published: May 2018

The paper explains the need for proper wastewater treatment in the Czech Republic and the development of legislation for effluent standards. A step-wise development from environmental quality standards to emission effluent standards is described. The necessity of retaining the environmental quality standards in the new legislation under specific conditions of the Czech Republic is explained. The paper describes the proposal by the Czech Association of Wastewater Treatment Experts to change the absolute effluent standards to standards with a stochastic character. The numerical values of effluent standards in the Czech Republic depend on the wastewater treatment plant size. Thus the wastewater treatment processes characteristic of individual size categories are described.
Systematic approaches in water management: Aquatic outlook and decision support systems combining monitoring, research, policy analysis and information technology
Authors: de Jong J. , van Buuren J. T. , Luiten J. P. A.
Published: May 2018

Sustained developments is the target of almost every modern water management policy. Sustainability is focused on human life and on the ecological quality of our environment. Both aspects are essential for life on earth. Within a river catchment area this means that well balanced relations have to be laid between human activities and ecological aspects in the involved areas. Policy analysis is especially looking for the most efficient way to analyse and to overcome bottlenecks.

In The Netherlands project “The Aquatic Outlook” all these elements are worked out in a nationwide scale, providing the scientific base and policy analysis from which future water management plans can be derived.
Status of construction and operation of large wastewater treatment plants in South Korea
Authors: Kim I.S. , Ryu J.Y. , Lee J.J.
Published: May 2018

The history of wastewater treatment in Korea began in 1976 with construction of Chongke sewage treatment plant in the city of Seoul. At present, there are 48 large municipal sewage treatment plants for 42 cities with a total treatment capacity of 7,841,000 m3/d. This indicates that the population receiving sewage treatment is 42% of the total national population. The government is planning to extend the population receiving wastewater treatment to 73% by the year 1997. It turned out that activated sludge processes are the most popular type (39 out of 48 plants) for the treatment of municipal wastewater.

The present lawful effluent criteria for BOD, COD, and SS from large municipal wastewater treatment plant are changing from 30 mg/l, 50 mg/l, and 70 mg/l, to 20 mg/l, 40 mg/l, and 20 mg/l, respectively, by the year 1996. Regulation of the total concentrations of nitrogen and phosphorus are also added as 60 mg/l and 8 mg/l, respectively. The enactment to control the nutrient concentrations in the lake and pond is inevitable for the protection of drinking water in South Korea.
A computational framework for modelling the fate of selected toxic substances in the meuse basin
Authors: Ploco S. Š.
Published: May 2018

Within the scope of the research program of Integrated Water Management Working Group, new research, focused on developing a computer aided system for policy analysis of water management for international river basins, has been launched at Delft University of Technology. This paper refers to conceptual strategies included in creating a part of the computational framework that will be used to support policy analysis of water quality management. Moreover, it outlines major process formulations and process constants referring to modelling the fate of trace metals (Cd, Cu, Zn), PCBs, PAHs, triazines (atrazine, simazine) and pesticides (dichlorovos, mevinphos, lindane). The choice of these substances is tailored to the prevailing water quality concerns that exist in the Meuse basin.
Oxygen supplementation by U-tube to the Tombigbee River
Authors: Speece R. E.
Published: May 2018

Disolved oxygen (D.O.) in the Tombigbee River in Alabama, USA occasionally decreases below 4 mg/L and forces two paper mills to reduce their effluent discharge loads to the river. These mills have limited capacity to store their treated effluents on-site. Therefore if the duration of critical D.O. conditions in the river exceeds the length of time that storage capacity is exhausted, paper production capacity must be curtailed. Since the combined capital costs of these two paper mills exceeds $2,000,000,000, the amortization exceeds $1,000,000 per day and it is prohibitively expensive to shut down paper production. Permission was granted to these mills by the river regulatory agency to supplement the D.O. resource of the river during critical periods to offset the effluent BOD loading to the river (4.7 kg O2/kg BOD5). This, in turn, negates the need to cut back on paper production. Two oxygen supplementation installations were made. Both use commercial oxygen, – instead of air – that is dissolved into the water by a U-Tube process. Each U-Tube forces the water down 175 feet (53.4 m) under a baffle and back to a river diffuser located 35 feet (10.7 m) below the river surface. Oxygen gas is injected at the U-Tube entrance and the bubbles are swept by the water down and back up through the U-Tube. This greatly increased hydrostatic pressure provides high oxygen absorption efficiency of the commercial oxygen while producing a D.O. concentration of 50 mg/l in the 28 oC discharge. The diffuser in the river facilitates very rapid mixing/dilution of the high D.O. discharge with the low D.O. river water. The D.O. several hundred feet downstream of the diffuser never exceeds 8.0 mg/l. One U-Tube installation adds 12,000 lb/day (5450 kg/day) of D.O. directly to the 35 MGD (1.53 m/sec) treated effluent from one mill. The second U-Tube installation 35 miles (58 km) downstream pumps 120 MGD (5.25 m3/sec) directly from the river though the U-Tube and adds 40,000 lb/day (18,180 kg/day) of D.O. before discharging through another diffuser located on the bottom of the river.
Practical aspects of the oxygen supply/sludge activity relationship
Authors: Tench H. B.
Published: May 2018

The basis of the sludge activity concept is described together with experimental applications. As a result of these it has been concluded that activated sludge plants normally operate under oxygen limiting conditions and that increases in the rate of aeration which enable the plants to deal with greater loadings require equal increases in the sludge and dissolved oxygen concentration. The increases necessary are not proportional to the increased loadings but to the square roots of them. Increase in turbulence of the mixed liquor does not appear to be a factor of importance down to retention periods of the order of two hours when treating an average strength sewage, but may have had an effect at lower aeration periods. Calculations using data obtained from a hybrid mechanical aeration plant at Manchester indicate that the percentage oxygenation of the sludge in a low intensity carbonaceous oxidation plant may be as low as 15%. Even in a high intensity plant treating sewage in two hours the calculations gave an estimate of 33% aerobicity. It appears that the sludge activity approach can be applied to nitrifying organisms and that they also tend to a maximum as the sludge concentration is increased. In full scale practice there will be an optimum dissolved oxygen level which gives the highest oxygen deficiency, and thus power economy, consistent with attaining the required nitrification.
Anaerobic substrate uptake by the enhanced biological phosphorus removal activated sludge treating real sewage
Authors: Satoh Hiroyasu , Ramey Williams D. , Koch Frederic A. , Oldham Williams K. , Mino Takashi , Matsuo Tomonori
Published: May 2018

The enhanced biological phosphorus removal (EBPR) activated sludge process is a wastewater treatment process by which not only organic pollutants but also phosphorus are removed. In the EBPR process, it is known that organic matter in the influent is removed in the anaerobic phase of the sequencing anaerobic and aerobic conditions. Although the mechanism of the anaerobic substrate uptake is being revealed, the existing observations are based on the experiments with activated sludge acclimatized with synthetic sewage, or synthetic media. In this study, the anaerobic substrate uptake by EBPR activated sludge treating real sewage was examined. The sludge was obtained from a pilot plant of the University of British Columbia, Canada. And as the substrate, acetate, propionate, lactate, pyruvate, malate, succinate, and fermented sewage were examined. The results clearly showed that most part of the sink of carbon anaerobically taken up is explained by PHA (poly 3-hydroxyalkanoates), and that glycolysis is playing a significant role in the anaerobic uptake of acetate and propionate.
Microbial adaptation, process performance and a suggested control strategy in a pre-denitrifying system with ethanol dosage
Authors: Hallin S. , Lindberg C.-F. , Pell M. , Plaza E. , Carlsson B.
Published: May 2018

Biological nitrogen removal in activated sludge processes is dependent on sufficient supplies of easily metabolized carbon compounds for the denitrifying bacterial population. An external carbon source can increase denitrification rates and compensate for deficiencies in the influent C/N ratio. Plant performance and microbial adaptation were studied in a pre-denitrifying pilot-scale activated sludge plant with and without ethanol. Total nitrogen removal efficiency was 67 and 35% for the ethanol and reference line, respectively. The process responded rapidly to ethanol but one sludge age was necessary for full bacterial adaptation. An initial rapid increase suggests enzyme induction rather than alterations in bacterial species composition. Increased enzyme activity was explained by an increase in turn-over rate of biomass. Low effluent nitrate concentration was a result of the simultaneous use of influent COD and ethanol. Fluctuations in influent COD did not affect denitrification capacity with ethanol. Sludge settling properties were moderately better in the process without ethanol addition. An automatic control strategy for carbon dosage using feedforward from influent carbon and nitrate in the recirculated flow was simulated. Simulations with an adaptive linear quadratic controller demonstrated that the desired nitrate concentration at the end of the anoxic zone could be maintained despite relatively large disturbances.
Nitrification and mass balance with a membrane bioreactor for municipal wastewater treatment
Authors: Xiao-Jun Fan , Urbain Vincent , Qian Yi , Manem Jacques
Published: May 2018

The overall performance of the Membrane Bioreactor (MBR) process for municipal wastewater treatment was studied to determine the characteristics of activated sludge under different Sludge Retention Times (SRT) and Hydraulic Retention Times (HRT). The experiment lasted over a period of 300 days, which included 4 runs. The effluent quality of the MBR process in terms of COD and suspended solids, was excellent under all conditions tested. Specific nitrification rates of the activated sludge were measured at steady state in each run. Similar maximum nitrification rate values were obtained through batch experiments with either only NH4Cl or raw wastewater as substrate. Mass balances of the process in terms of COD, nitrogen and inorganic suspended solids were made, and it was found that 28%, 42%, and 48% of influent COD were converted into activated sludge at SRTs of 20, 10, and 5 days, respectively. The COD/VSS ratio of the activated sludge seems to be dependent on mass loading rate. The estimated true yield and decay rate coefficients of the activated sludge were 0.61 kgCOD/kgCOD and 0.050 d−1, respectively. In the completely aerobic system, nitrogen balances were always close to 100%.
Use of contact tank to enhance denitrification in oxidation ditches
Authors: Hao X , Doddema H. J. , van Groenestijn J. W.
Published: May 2018

Poor denitrification in a Pasveeer oxidation ditch is attributed to a lack of carbon sources available in the anoxic zone as it is essential to maintain a high C/N ratio for denitrification. Influent of sewage directly into the anoxic zone is not useful to maintain a high C/N ratio. The adsorptive capacity of activated sludge can rapidly increase the C/N ratio. Similar to a contact-stabilization process, a contact tank can be combined with the Pasveer ditch; it provides contact time (zone) between raw sewage and return sludge before entering the ditch. In principle, insoluble organic substrate can be easily adsorbed onto the floc surfaces and enmeshed in the floc structure at a short retention time. After the contact, mixed influent is introduced into the anoxic zone. As a result, a high C/N ratio is obtained which enhances denitrification. Using this set up, the Pasveer ditch was operated. The experimental results show that the efficiency of denitrification has been enhanced from 45 to 83% for NO−3-N removal. The corresponding denitrification capacity of the sludge is increased by 240%. The contact tank has also the same principle as a ‘selector’ to control bulking sludge caused by filamentous bacteria. The SVI data and microscopic examination indicated improved settleability of the sludge. Further enhancement of denitrification needs an exact control of the dissolved oxygen level in the ditch and/or a concentration increase of denitrifying microorganisms.
Effects of population displacements on biological phosphorus removal in a biofilm SBR
Authors: Muñoz-Colunga Ana , González-Martínez Simón
Published: May 2018

A biofilm sequencing batch pilot reactor was operated 400 days in order to determine the effects of different operation strategies on the capacity of the biofilm to remove nutrients (C, N, and P). The reactor was fed with wastewater from the main campus of the National University of Mexico. The wastewater was enriched with a molasses and phosphate solution when needed to vary the nutrients concentration. The operation was controlled with an industrial programmable timer. The treatment cycles were adjusted with four stages: filling, anaerobic phase, aerobic phase and draw of treated wastewater. Cycles of 8 and 12 were tested with different anaerobic/aerobic time ratios. The highest removal COD and PO4-P rates were obtained with 12-hour cycles and phases duration of 37/63 percent anaerobic/aerobic. Analyzing COD, TOC, PO4-P, NH4-N, and NO3-N, shifting of the different bacterial groups could be followed. When the organic loading rate was higher than 5 gCOD/m2·d the activity of the phosphate accumulating bacteria and nitrification could not be observed. The best results regarding phosphate removal and nitrification were obtained when the mean organic load was 3 gCOD/m2·d.
Effects of pH and alkalinity on sulfur-denitrification in a biological granular filter
Authors: Furumai Hiroaki , Tagui Hideki , Fujita Kenji
Published: May 2018

Two laboratory-scale biological filters were operated to investigate the effects of alkalinity and pH on removal of nitrate and nitrite in sulfur denitrification filter processes. The concentration of sodium bicarbonate in the feed media was changed from 120 to 240 mg/l during about 3 months in a filter (Run A). The other filter was initially fed with 300 mg/l and then with 240 mg/l (Run B). The performance of the filter was monitored by measuring pH, nitrate, nitrite, sulfate, alkalinity, and thiosulfate.

Nitrate concentration in effluent rapidly decreased to lower levels within several days for both filters after inoculation of enrichment culture of sulfur denitrifiers. However there was a large difference in removal of nitrite. When rapid removal of nitrate took place, nitrite accumulation was observed and remained while the bicarbonate concentration was 120 and 150 mg/l. On the other hand the nitrite accumulation disappeared when more bicarbonate (240 and 300 mg/l) was supplied. The experimental results indicated that the nitrite accumulation was closely related to pH condition and alkalinity level in the filter. The stable data of effluent water quality for 5 cases were collected and the relationship discussed between nitrite concentration and pH in effluents. The relationship indicated a strong pH dependency on nitrite accumulation below pH of 7.4. The pH condition around 7 is not so inhibitory to biological activity. Therefore, the pH within the biofilm would be low enough to suppress the nitrite reduction by sulfur denitrifiers, while the pH in effluent was not in the inhibitory range. It was recommended to keep the pH higher than 7.4 to prevent nitrite accumulation in the sulfur denitrification filter.
Another carbon source for BNR system
Authors: Choi E. , Lee H. S. , Lee J. W. , Oa S. W.
Published: May 2018

It has been known wastewater with low COD/TKN ratio produces higher effluent NO3-N and adversely affects poly P microbes returning it to an anaerobic stage in BNR systems. Nightsoil applicability to return activated sludge line to minimize NO3-N effect to poly P microbes in anaerobic stage was examined with laboratory BNR systems operated at 20°C. The study results indicated nightsoil application could improve nitrogen and phosphorus removal efficiencies both with low strength settled municipal and piggery wastes presenting low COD/TKN ratios of 6 and 2.2, respectively. Even organic loading rates increased to 20 to 60% due to nightsoil application, the effluent COD increased only 10 to 20%. This would suggest nightsoil can be used as another carbon source and nightsoil application to return activated sludge line can be another alternative modification to improve BNR systems.
P-fixation by Mg, Ca and zeolite a during stabilization of excess sludge from enhanced biological P-removal
Authors: Wild D. , Kisliakova A. , Siegrist H.
Published: May 2018

In anaerobic digestion of excess sludge originating from enhanced biological phosphorus removal (EBPR) a complete hydrolysis of polyphosphate occurs. Varying information exists about the resulting return flow of phosphorus to the activated sludge plant. Magnesium, calcium and zeolites from detergents are the main species involved in the refixation of dissolved phosphate in the digester supernatant. Their interactions and mechanisms of phosphate removal have been characterized and quantified in experiments. The precipitation of struvite (MgNH4PO4·6H2O) evolves according to the equilibrium, whereas the fixation by calcium occurs kinetically controlled in the form of brushite (CaHPO4·2H2O) or hydroxyapatite (Ca5(PO4)3OH). Zeolites in digester sludge originate mainly from detergents. They represent around 7% of total solids entering the digester and their impact on digestion is given by 4 modes: The control of free cation concentrations as an exchanger, as a source for calcium ions, as generator of aluminum phosphate precipitation after being partly hydrolyzed and as a nucleus for crystallization processes. With the current sludge composition phosphate fixation processes in anaerobic digesters avert serious recycle load problems.
Release of phosphorus from ash produced by incinerating waste activated sludge from enhanced biological phosphorus removal
Authors: Matsuo Yoshitaka
Published: May 2018

A technical problem involved in the phosphorus removal using the enhanced biological phosphorus removal (EBPR) process is disposal of the phosphorus rich waste sludge. There are possibilities that any phosphorus in the disposed sludge would release to water environment. If the release occurs, it will nullify the efforts made in wastewater treatment. This paper reports results of a preliminary study made to examine the fate of phosphorus in the ash is produced by incinerating waste sludge from a laboratory unit of the EBPR process. A large part of phosphorus in the ash released in a relatively short time. Most of the phosphorus released at a normal temperature was apparently polyphosphate. The release was very fast at a high temperature. The finding suggests that hot water elutriation could be used as a means of recovering phosphorus from the ash. It was also suggested that the release could be prevented by adding an appropriate amount of iron to the sludge to be incinerated. The released phosphorus was susceptible to precipitation by metals, especially iron.
Primary sludge hydrolysis for biological nutrient removal
Authors: Hatziconstantinou G. J. , Yannakopoulos P. , Andreadakis A.
Published: May 2018

Primary sludge hydrolysis can enrich primary effluent with the soluble organics which in turn can be a valuable carbon source to subsequent nutrient removal processes. By controlling hydraulic retention time and temperature it is possible to confine the anaerobic digestion of the primary sludge to the acidogenic and acetogenic phase (hydrolysis/fermentation process), and take advantage of the soluble organics produced.

This paper presents the results of a research involving bench and pilot scale experiments related to primary sludge hydrolysis. The pilot scale sedimentation tank (4.10 m in diameter, 3.20 m in depth) operated over an expended period of 21 months as a conventional clarifier and following this as a fermentor unit employing sludge recirculation. Parallel to the pilot scale experiments, several batch and continuous flow bench scale experiments were conducted in order to determine the factors controlling the production of soluble organics and the effect of the latter on the denitrification process.

The conclusions drawn were that a) a soluble COD production of the order of 5-6% in terms of sludge TCOD can be expected in a batch fermentor operating with HRT≅2days at T≤ 20°C, b) in a continuous flow fermentor, combinations of T>20°C and SRT>2 should be applied in order to achieve a production of the order of 10%, c) significant soluble carbon production can be achieved in primary sedimentation tanks (over 30% in terms of influent SCOD) when relatively increased SRTs (4 to 5 days) in combination with sludge recirculation are employed, under T>22°C, and d) increased denitrification performance of the order of 9 mgNOx/g MLSS.hr, can be achieved with hydrolysate as a carbon source.
Theoretical analysis on nitrogen removal of the step-feed anoxic-oxic activated sludge process and its application for the optimal operation
Authors: Fujii Shigeo
Published: May 2018

The nitrogen removal efficiency of the step-feed anoxic-oxic activated sludge process, which has two anoxic tanks and two oxic tanks, was theoretically discussed on the basis of the stoichiometry of denitrification and nitrification reactions. As the first step, effluent NH4-N and NO3-N concentrations were formulated with four parameters; 1) a, equivalent ratio of alkalinity to ammonia in influent, 2) b, that of substrate to ammonia, 3) r, step ratio of influent to the second anoxic tank and 4) R, return (+ recycle) sludge ratio. This calculus was done for the possible sixteen (=24) cases which show different reaction patterns in four tanks, and 12 cases out of 16 were found to be available. The effects of step ratio, r were examined in its range of 0 - 1 at a fixed R value, and it was found that the increase of r alters the outcome in a different way depending on the ranges of a and b. Consequently, zoning of a-b coordinates was successfully made, and the optimal r value for maximum total nitrogen removal was obtained in each zone. In addition, the optimal volume allocation of the four tanks was discussed and the ratios were formulated for each zone.
Synthesising dry weather flow input hydrographs: a Maltese case study
Authors: Butler David , Gatt Kevin
Published: May 2018

Dry weather flow (DWF) input hydrographs are an essential aspect of combined sewerage modelling. Collecting or deriving such hydrographs is not easy given problems of accurate data collection, location in the network and disaggregation of other flows. A method of synthesising DWF hydrographs is presented based on results from a diary survey of individual domestic appliance usage. Such a study has been carried out on 51 households in Malta and it is shown that the sample is a reasonable representation of the local population. Appliance volumes were found to be consistent with those in the literature with the possible exception of the bath. Daily per capita usage was also found to be comparable in magnitude. Detailed plots consisting of volumetric discharge for each appliance were produced illustrating the significant diurnal variations in usage. A template plot for the Maltese Isles was produced indicating a mean and peak usage of 1.1 and 2.7 l/s/1000 head respectively.
Representation of solute transport and mixing within a surcharged benched manhole using an aggregated dead zone (ADZ) technique
Authors: Guymer Ian , O'Brien Rob , Harrison Chris
Published: May 2018

Previous studies of the effects of manhole structures on the longitudinal dispersion of a soluble pollutant have been provided for unbenched manholes, concentrating on determining the dispersion effect by employing a rate of change of second moment of area of the temporal concentration distribution. This paper provides new results from over 350 individual experiments for a manhole structure containing benching with flow rates between 2 and 7.6 l/s. The effects of discharge and surcharge on both the solute travel time and the spreading of the solute slug are quantified. The results are used to estimate the parameters required to simulate the effects of the manhole on solute mixing using an Aggregated Dead Zone (ADZ) technique. Values of the mean parameters are presented together with an initial assessment of the predictive capability of the technique.
Nonlinear and set-point control of the dissolved oxygen concentration in an activated sludge process
Authors: Lindberg Carl-Fredrik , Carlsson Bengt
Published: May 2018

Control of the dissolved oxygen concentration (DO) in an activated sludge process is of considerable importance because of economy and process efficiency. A strategy for designing a nonlinear DO controller was developed. The basic idea was to take the nonlinear oxygen transfer function into account in the controller design. Simulations illustrated that a nonlinear DO controller outperforms a standard PI controller. This was also confirmed in a pilot-scale plant experiment. A supervision (set-point) controller for the DO is also outlined. Initial simulations showed promising results where the aeration system is used more efficiently and the effluent ammonia concentration could be maintained low.
The effect of nitrate on VOC removal in trickle bed biofilters
Authors: Xueqing Zhu , Rihn Molly J. , Suidan Makram T. , Kim Byung J. , Kim Byung R.
Published: May 2018

Biofiltration is becoming an established economical air pollution control technology for removing volatile organic compounds (VOCs) from waste air streams. This study utilizes diethyl ether as a VOC substrate and nitrate as a nitrogen nutrient source to investigate the effect of nitrate on VOC removal. Two trickle bed biofilters with pelletized media were operated co-currently at ether loading rates of 1.78 and 3.56 kg COD/m3·day respectively, with a low empty bed retention time of 25 seconds, inlet gas flow rate of 8.64 m3/day and nutrient liquid flow rate of 1 1/day. The ether removal efficiencies improved from 72% to over 99% with increasing influent nitrate concentration from 66.7 to 266 mg NO3-N/l in the higher loaded column. Throughout the experiment, nitrate persisted in the liquid effluent. The lower ether removal at low influent nitrate concentrations was not due to nitrogen shortage, which suggests that the nitrate diffusion in the biofilms is rate determining. The higher COD:N consumption ratio in the biofilter with higher ether loading also indicates that ether removal may benefit from the utilization of nitrate as an alternative electron accepter in the deeper layers of the biofilm where the oxygen may be limited.
Basic comparison of structure and functioning of legislative, governmental and non-governmental bodies for water quality management in the USA and the CR: an american view
Authors: Brady Donald J.
Published: May 2018

The structure and function of water quality management systems in USA and CR are compared and the basic principles of the Water Protection Approach used by US EPA outlined.
Modelling impact of urban and upstream nonpoint sources on eutrophication of the Milwaukee River
Authors: Hajda Pavel , Novotny Vladimir
Published: May 2018

This paper describes a study conducted to evaluate the impact of the absence vs. the presence of the North Avenue Damin Milwaukee, Wisconsin, on water quality in the Milwaukee River in terms of conventional constituents, such as DO, chlorophyll a, BOD, and nutrients (N and P). Phytoplanktonic primary production had been recognized earlier as a link between mostly nonpoint nutrient loads to the Milwaukee River and degradation of water quality in the River. A mathematical model of a relevant section of the River was used in the study to estimate the effect of the removal of the Dam on this primary production link. The authors established the model using WASP, which is USEPA's widely used modelling package. The modelled extent of the River included both shallow, productive upstream reaches as well as impounded downstream sections. In the impounded reach of the River where the Dam is located, the simulated removal of the Dam (1) replaced net phytoplankton decay with net phytoplankton growth because of improved light conditions and limited settling; (2) substantially increased the concentration of DO because of the increased photosynthetic production and reduced benthic consumption; and (3) somewhat increased bottle BOD5 because of the elevated phytoplankton levels. The simulated removal of the Dam eliminated the negative effects of eutrophication at the site while possibly shifting the potential for these effects further downstream towards Lake Michigan.
Diffuse nutrient impact on surface water bodies and its abatement by restoration measures in a small catchment area in North-East Germany
Authors: Gelbrecht J. , Driescher E. , Lademann H. , Schönfelder J. , Exner H.-J.
Published: May 2018

Water resources management in NE Germany is still confronted with the consequences of eutrophication. Since the majority of nutrient loading is of diffuse origin, an exact understanding of the various sources is a prerequisite to reducing their impact on surface waters. Control of diffuse pollution demands a “strategy of little steps”, i.e. a variety of numerous measures at different locations in the whole catchment area. The paper describes different nutrient sources, especially those of phosphorus, in a small catchment, provides data on the sources and amounts of pollution and demonstrates proposals and strategies for abatement (e.g. reduction of fertilizers, restoration of wetland and brook stretches, development of ponds). Among the different sources, subsurface water enriched with phosphorus, plays an essential role, because arable soils are oversupplied with phosphorus and the sorption capacity of several soils is nearly exhausted.
Regional estimation of ground water vulnerability to nonpoint sources of agricultural chemicals
Authors: Burkart Michael R. , Feher Janos
Published: May 2018

The potential for ground water contamination by agricultural chemicals exists in many regions of the world. A collaborative effort between Hungarian and United States scientists has developed a general strategy to estimate the regional vulnerability of ground water to agricultural chemicals. The midwest U.S. and most of Hungary are major agricultural regions with similar hydrogeologic settings. Many areas where ground water provides public drinking water supplies in these regions are vulnerable to ground-water contamination. The vulnerability of shallow, unconsolidated aquifers and thinly-covered bedrock aquifers to agricultural chemicals is being investigated in an initial application of the strategy. This strategy integrates elements of overlay methods of vulnerability estimation, process-based modeling methods, and statistical methods. Strategy steps include: identifying characteristics of ground water needed to classify regional ground water resources; mapping the spatial distribution of aquifer classes (unconsolidated and bedrock) using a regional geographic information system; and estimating the occurrence of agricultural contaminants by applying leaching models to representative conditions in each aquifer class. In the U.S. project, pedologic data bases are being used for both mapping aquifer classes and model input. Estimated vulnerability will be evaluated against data from a regional survey of shallow aquifers recently completed in the Midwest. The Hungarian project is developing new maps of basic hydrogeologic characteristics with data that can be used to model vulnerability of the 1-meter root zone, the unsaturated zone, and the saturated zone.
Management of diffuse pollution in groundwater under imprecise conditions using fuzzy models
Authors: Woldt W. , Dahab M. , Bogardi I. , Dou C.
Published: May 2018

This paper presents a framework for evaluation of nitrate control strategies that use spatially variable nitrogen input in the presence of imprecise information. The research stems from the fact that diffuse pollution has caused water consumers to be concerned with reducing the risk posed by contaminated water supplies. An important element in quantifying risk reduction is the use of simulation modeling to predict the transport and fate of contaminants under variable rate application as employed in a wellhead protection area strategy. Specifically, a groundwater model is linked with an unsaturated zone transport (and crop production) model which provides the nutrient and recharge loading rates to the saturated zone. To consider uncertainty stemming from the unsaturated zone model output, in addition to aquifer parameters, a new groundwater modeling technique is developed in which fuzzy set theory is combined with finite-difference modeling methods. The groundwater model incorporates imprecise parameters (i.e., transmissivity) into the modelling process through the use of fuzzy set theory. Imprecision has been encoded directly into the finite-difference equations using fuzzy numbers as input, and level-set operations combined with non-linear optimization are used to solve the system of equations. The resulting fuzzy output can be interpreted as the level of imprecision associated with the model. A case study is presented to illustrate the methodology.
Influence of inlet and outlet configuration on the flow in secondary clarifiers
Authors: Krebs Peter , Stamou Anastasios I. , García-Heras Jaime L. , Rodi Wolfgang
Published: May 2018

A numerical model for predicting the flow in clarifiers is presented which accounts for density-affected and turbulent flow as well as for the settling of activated sludge. The reliability of the two-dimensional model is demonstrated through verification by means of a laboratory experiment which was specially designed for this purpose. The numerical model is then applied for an evaluation of inlet and outlet arrangements. The inlet is positioned at the bottom and the inlet aperture is varied. An outlet at the top of the end wall is compared with outlets longitudinally extended at the surface. The alternatives are assessed by analysis of streamline patterns, layer charactersitics and the entrainment into the bottom current, i.e. the increase of its flow rate. The study demonstrates how numerical modelling can be used for systematic evaluation of the effect of geometrical configurations on the flow in secondary clarifiers.
The effect of heterotrophic yield on the assessment of the correction factor for anoxic growth
Authors: Orhon D. , Sözen S. , Artan N.
Published: May 2018

For single-sludge denitrification systems, modelling of anoxic reactors currently uses the kinetics of aerobic heterotrophic growth together with a correction factor for anoxic conditions. This coefficient is computed on the basis of respirometric measurements with the assumption that the heterotrophic yield remains the same under aerobic and anoxic coditions. The paper provides the conceptual proof that the yield coefficient is significantly lower for the anoxic growth on the basis of the energetics of the related metabolic processes. This is used for the interpretation of the very high values for the correction factor experimentally determined for a number of industrial wastewaters. A default value for the anoxic heterotrophic yield coefficient is calculated for domestic sewage and compatible wastewaters and proposed for similar evaluations.
Investigation into the microbiology of a high rate jet loop activated sludge reactor treating brewery wastewater
Authors: Dilek F. B. , Anderson G. K. , Bloor J.
Published: May 2018

The microbiology of a jet loop activated sludge reactor treating brewery wastewater has been investigated, with a venturi system combining liquid pumping with air diffusion being the basic feature of the system. The high F/M ratio, the high growth rate of the bacteria and the high levels of turbulence registered in the jet loop reactor caused the disappearance of filamentous bacteria and the production of a cloudy effluent. The population in the reactor was mainly formed by aerobic bacteria all belonging to the Pseudomonas species. Facultative anaerobes were present in small numbers, namely Klebsiella oxytoca, Klebsiella pneumonia ssp. pneumo., Vibrio fluvialis and Aeromonas hydrophila. Very high levels of respirometric activities were recorded for the mixed liquor of the reactor. The respirometric activities of individual isolates were also found to be remarkably high, especially when treating brewery wastewater. The magnitudes of their activities were a function of their relative abundance within the reactor.
Growth of an activated sludge foam-forming bacterium, Nocardia Pinensis, on hydrophobic substrates
Authors: Soddell Jacques , Seviour Robert
Published: May 2018

Nocardia pinensis is a very slow-growing organism in pure culture, yet grows well enough to cause serious foaming problems in activated sludge plants. On hydrophobic substrates like olive oil and Tween 80, it produced more biomass, and grew much faster, than on a simple hydrophilic substrate like glucose. On olive oil it also grew as compact clumps of branching filaments which attached to the oil droplets, suggesting a possible mechanism for competing with other less hydrophobic, but faster growing, organisms. These results are discussed in relation to ecological strategies of the organism in activated sludge plants.
Optimal operation of bioreactor system developed for the treatment of chromate wastewater using enterobacter cloacae HO-1
Authors: Fujie Koichi , Hu Hong-Ying , Huang Xia , Tanaka Yukio , Urano Kohei , Ohtake Hisao
Published: May 2018

The characteristics of a novel bioreactor system developed for the simultaneous treatment of toxic hexavalent chromium (chromate) and high-strength organic pollution by introducing a chromate-resistant and chromate-reducing bacterium Enterobacter cloacae strain HO-1 (HO-1, hereafter) were studied to optimize its operating condition. Based upon the growth and chromate-reducing kinetics of HO-1, a mathematical model to simulate the change of chromate removal rate per unit volume of bioreactor and that per unit cell mass under the fed-batch operation was proposed. The effects of repeated cultivation of HO-1 with ORP-controlled aeration and the cumulative chromate reduction per unit cell mass on the microbial activity were investigated to represent the kinetic expression of chromate reduction. By using the mathematical model developed through the present research, the relationship between the operating conditions and the chromate reduction rate in the bioreactor was simulated and the model was verified by comparing it with the observed data. Thus the optimal operating conditions to give the higher reduction rate and the longer operating interval with and without aerated cultivation of HO-1 are extensively discussed. This bioreactor can be used for the treatment of chromate wastewater provided that some high concentration organic wastes are available. The rate of chromate reduction in the bioreactor is as high as 10 - 15 g-Cr6+/m3h. Chromium hydroxide, products of biological chromate reduction, can be recycled as a green pigment.