bluuebunny/crossref_metadata_2025 huggingface dataset:
The interaction of a manganese-oxidising bacterium as part of a biofilm growing on distribution pipe materials
Authors: Murdoch F. , Smith P.G.
Published: May 2018

The deposition of manganese within a biofilm growing on the surface of high-density polyethlene (HDPE) and polyvinychloride (PVC) was studied over a period of four months. The manganese rich water used in the study was inoculated with a manganese oxidising Pseudomonas spp. The level of Mn2+ in the water was monitored and was found to decrease as the biofilm formation increased. This was confirmed by energy dispersive X-ray spectroscopy (EDS) analysis which showed the detection of manganese was dependent on the presence of a biofilm. After two months a 100% removal of Mn2+ was observed in all the flasks inoculated by the Pseudomonas spp. and manganese micro-nodules, the formation of which were reported in Murdoch and Smith (1999), were being formed in large clusters across the surfaces of both the HDPE and PVC. The manganese peak area from the EDS spectrum analysis of the micro-nodules was significantly larger than was measured in the biofilm when these micro-nodules were absent. The scanning confocal laser microscope (SCLM) images of three-week samples showed high bacterial activity around areas where manganese micro-nodules were starting to form on the pipe surface.
Modelling biofilm growth and disinfectant decay in drinking water
Authors: Jegatheesan V. , Kastl G. , Fisher I. , Angles M. , Chandy J.
Published: May 2018

A simple biofilm model was developed to describe the growth of bacteria in drinking water biofilms and the subsequent interactions with disinfectant residuals incorporating the important processes, such as attachment of free bacteria to the biofilm on a wall surface, detachment of bacteria from the biofilm, growth of biofilm bacteria with chloramine inhibition, chloramine decay in the bulk water phase, and chloramine decay due to biofilm bacteria and wall surfaces. The model is useful in evaluating the biological stability of different waters, as it can predict concentration of organic substances in water. In addition, the model can be used to predict the bacterial growth and biofilm decay in distribution systems. A model of this kind is a useful tool in developing system management strategies to ultimately improve drinking water quality.
The circulating floating bed reactor: effect of particle size distribution of the carrier on ammonia conversion
Authors: Garrido-Fernandez J.M. , Méndez R. , Lema J.M. , Lazarova V.
Published: May 2018

Three Circulating Floating Bed Reactors (CFBR) R1, R2 and R3 with 20% v/v of a plastic carrier with different size distribution were operated to study the effect of the particles size of the carrier on biomass accumulation and nitrification performance. Operating conditions were similar in the three systems: ammonia concentrations around 50 mg-N–NH4+/ L, ammonia loading rates up to 1.2 kg N–NH4+/m3·d and temperatures between 14 and 27°C. Accumulation of nitrite was observed until day 65th. This w as result both of the inhibition of nitrite oxidation by free ammonia until day 20th and the insignificant accumulation of a biomass with low nitrite oxidising capacity between days 20 and 65th. Ammonia conversion rate and removal efficiency were higher in the reactor with lower particle size, R3 (nitrification rate of 1.1 kg N–NH4+/m3·d and ammonia removal of 97% at 16°C), than in R2 or R1 (nitrification rate of 1.0 kg N–NH4+/m3·d and ammonia removal of 90% at 16°C). The better efficiency in R3 was obtained as a result of the higher specific surface of the biofilm developed. Biomass activity was similar in the three reactors (2.2 and 1.12 g N/g protein · d at 30 and 15°C, respectively). Both the biomass evolution with time and biomass retention in the systems was practically not influenced by the size of particle. Biomass concentration of 1.2 g protein/L was retained in the carrier and up to 20% of the newly produced biomass was retained in the CFBRs.
Extensive nitrogen removal in a new type of airlift reactor
Authors: Frijters C.T.M.J. , Vellinga S. , Jorna T. , Mulder R.
Published: May 2018

A new type of CIRCOX® airlift reactor was started-up treating anaerobically pre-treated potato-processing waste water. This type of airlift reactor with biofilms on carrier is an airlift reactor extended with an anoxic compartment to obtain total nitrogen removal. This type of reactor was designed in the early nineties and was tested successfully at pilot-scale on brewery and municipal waste water. The 3 m3 pilot reactor was scaled-up to a size of 130 m3. Both the hydraulics and the biological performance were studied. High liquid velocities and equal concentrations of sludge throughout the whole reactor, indicated that the system was well mixed. Up to 5 kg COD/m3/day was removed. Ammonia was almost completely removed (up to 1.0 kg NH4–N/ m3/day in the aerated compartment). The denitrification efficiency was over 90%. The NOX–N concentration in the effluent never exceeded 6 mg/l. The biofilm layers were extremely dense: 30 g/l of VSS with a sludge volume of 220 ml/l. Therefore the particles had high settling velocities and could easily be retained in the reactor. It can be concluded that this new technology has been scaled-up successfully. With this an aerobic technology is available in which extended treatment and nitrogen removal are accomplished in a very compact system.
Combined denitrification and phosphorus removal in a biofilter
Authors: Falkentoft C.M. , Harremoës P. , Mosbæk H. , Wilderer P.
Published: May 2018

A lab-scale biofilter was run continuously for 1½ years for combined denitrification and phosphorus removal. lternation between anaerobic and anoxic (nitrate) conditions was used to obtain an enriched culture of denitrifying, phosphate accumulating organisms. Batch experiments were performed to test the importance of diffusion and zonation in the biofilm. Half- and zero-order anaerobic phosphate release and anoxic phosphate uptake rates were verified, which was taken as an indication of a zonated biofilm.

To investigate the practical applicability of the process, the development of a computer model is necessary due to the high complexity of the process. AQUASIM is suitable for this purpose. The model can provide insight into what goes on inside the biofilm and act as a tool when predicting required tank sizes, optimal phase lengths and biofilm thickness etc. for a large-scale system. For control of the process, on-line measurements and computer control of the system are essential.
Cleaner production in the chemical industry
Authors: Alzamora Rumazo C. , Pryor A. , Ocampo Mendoza F. , Campos Villareal J. , Robledo J.M. , Rodríguez Mercado E.
Published: May 2018

A cleaner production demonstration study was developed in 1998 for the chemical industry by the Mexican Center for Cleaner Production with the support of the United States Agency for International Development (USAID). The project's objective was to develop cleaner production assessments for chemical plants by identifying and evaluating process and energy cleaner production opportunities for technical feasibility, economic benefit and environmental impact. Four plants in the chemical industry groups of inorganic and organic chemicals and plastic materials and synthetic resins were involved.

The main results are: (1) a reduction of solid toxic residues in the organic chemicals plant of 3,474 kg/year with after-tax savings of US$ 318,304/year; (2) an increase in plant capacity of 56%, and 10% reduction in VOCs emissions in the plasticizers and epoxidated soybean oil plant with after-tax savings of US$ 2,356,000/year; (3) a reduction of 31,150 kg/year of ethylene oxide emissions with after-tax savings of US$ 17,750/year in the polyethylene glycol plant and (4) a reduction of CO2 emissions of 9.21% with after-tax savings of US$ 44,281/year in the inorganic chemicals plant.

The principal areas for improvement in the chemical industry are process control and instrumentation, process design, maintenance programs and providing adequate utilities for the plants.
B.O.O. Case: water management project for the use of reclaimed wastewater and desalted seawater for the “Antonio Dovali Jaime” refinery, Salina Cruz, Oaxaca, Mexico
Authors: Baron C. , Equihua L.O. , Mestre J.P.
Published: May 2018

The water management project for the “Antonio Dovali Jaime” Refinery is definitely one of the firsts of its type that has been implemented in México. The aim of this project is to reduce the water consumption through seawater desalination for steam generation and reclamation of treated wastewater for cooling purposes. For this purpose Pemex-Refinación opened a bidding process under a Build-Own-and-Operate scheme. In 1995 the partnership formed by BICONSA, Degrémont and Marubeni was awarded this project. The processes selected include: reverse osmosis for seawater desalination as well as biological treatment with nitrification-denitrification and tertiary treatment for industrial wastewater treatment. The construction of this facility started at the end of 1997 and started its operation at the end of 1999.
Methanethiol production as an indicator of toxicity in anaerobic treatment
Authors: Zitomer D.H. , Owens D. , Speece R.E.
Published: May 2018

In the operation of a biological process, it would be helpful to have some indication of when the microcosm is under stress due to toxicity or otherwise. Various indicators have been suggested. In this research it was found that the reduced sulfur compound methanethiol was produced when various inhibitors were injected into a well operating system e.g. sodium ion, toluene, ethyl acrylate, tetrachloroethylene, octane, and chloroform. These inhibitors were added at concentrations equivalent to 50% to 200% of their IC50 concentrations. Operation of the system with two primary substrates – acetate and glucose – were evaluated. Methanethiol production was found to be correlated to inhibition.
High-rate anaerobic treatment of purified terephthalic acid wastewater
Authors: Kleerebezem R. , Lettinga G.
Published: May 2018

During production of purified terephthalic acid (PTA) a concentrated waste stream is generated, containing both readily (acetate and benzoate) and slowly (terephthalate and para-toluate) degradable organic substrates. Based on our experimental experiences with the anaerobic treatment of this waste stream, this paper presents an optimized concept for start-up and operation of a two-stage anaerobic bioreactor system. Based on considerations concerning the optimal conditions for cultivation of the specific types of biomass degrading the different substrates, and considerations concerning sodium-hydroxide requirements for pH-control, a gradual transition between initial operation in parallel to operation in series is suggested.
Upgrade of a petrochemical wastewater treatment plant by an upflow anaerobic pond
Authors: Noyola A. , Macarie H. , Varela F. , Landrieu S. , Marcelo R. , Rosas M.A.
Published: May 2018

A petrochemical plant producing terephthalic acid faced a saturation of its wastewater treatment facilities due to an increase in production. In fact, the plant has been growing in recent years, and the effluents have been treated by reproducing the original activated sludge design. However, owing to lack of space, as well as energy consumption and sludge production reaching a certain level, the plant considered other options for coping with the new effluent flow and organic load.

Based on the authors' previous experience with this wastewater, the consultant designed a process consisting of modifying an existing pond, in order to add an anaerobic step before the aerobic tanks already in operation. The anaerobic pond is a three-stage process, all included in the same adapted basin, with a distribution system in the bottom of each stage that creates an upflow pattern. Terephthalic acid wastewater is a mixture of several organic acids, with different anaerobic degradation kinetics, acetic and benzoic acids being more rapidly removed; the staged design takes this into account. The first two stages have a plastic floating cover (5,813 m3 and 8,719 m3 volume, respectively), while the third one is a conventional UASB type reactor (6,276 m3 volume) with a gas-liquid-solid separation device on top.

The design wastewater flow is 230 m3/h, with 10,300 mg/l COD, a pH of 4.5 and a temperature of 40 °C. There is an effluent recycling pump (510 m3/h) to control upflow velocities and eventual acidification problems in the first two stages. The reactor, seeded with anaerobically adapted waste sludge from the aerobic plant, is now under start up, with the expected performance.
Anaerobic effluent treatment by a pilot and full-scale plant at a chemical industrial complex
Authors: Boulenger P. , Driessen W. , van de Werfhorst E. , Tielbaard M.
Published: May 2018

To test the feasibility of anaerobic treatment of an effluent from a chemical factory producing intermediates for synthetic fibres, test work with a 45 l UASB pilot plant was conducted. Following its successful operation, a full-scale anaerobic effluent treatment plant including a 400 m3 combined pre-acidification tank and a 990 m3 Biopaq®-UASB reactor was constructed. The results of the pilot plant and the full-scale anaerobic treatment plant have been compared, similarities and differences in performance are presented and evaluated. COD removal efficiencies above 80% and BOD efficiencies in excess of 85% achieved in the pilot trial were confirmed by the full-scale installation. Overall process design as well as operational data from the pilot trial and the full-scale plant is presented. Despite the differences in configuration, operational results of the full-scale plant are comparable to the results obtained from the pilot plant study making such a pilot plant a useful tool for the process design of an full-scale anaerobic effluent treatment plant.
Nitrogen-fixing bacteria capable of utilising kerosene hydrocarbons as a sole carbon source
Authors: Pérez-Vargas J. , Poggi-Varaldo H.M. , Calva-Calva G. , Ríos-Leal E. , Rodríguez-Vázquez R. , Ferrera-Cerrato R. , Esparza-García F.
Published: May 2018

Several nitrogen fixing consortia (NFC) were isolated from kerosene contaminated soil, where Phaseolus vulgaris plants were being cultivated. The capability of these consortia for kerosene hydrocarbons removal was investigated and demonstrated. The NFC cultivated under aerobic conditions, and kerosene as sole carbon source, effected a maximum of 75% of reduction of the total kerosene hydrocarbons. Also, from experiments conducted to evaluate their atmospheric nitrogen fixing capability, all consortia showed nitrogenase activity: from 4 to 183 nmol N2/3E09 bacteria.day. To our knowledge, this is the first report that shows a group of bacteria with the dual characteristic of fixing atmospheric nitrogen and capability to use kerosene hydrocarbons as a sole carbon source. Application of these microorganisms to soil bioremediation processes is discussed.
Two-stage biofiltration of sulfides and VOCs from wastewater treatment plants
Authors: Devinny J.S. , Chitwood D.E.
Published: May 2018

Hydrogen sulfide and volatile organic compounds are often found together in waste air streams. This combination is difficult to treat by biofiltration because oxidation of the sulfide produces acid, reducing the pH in the biofilter. Rapid declines in pH can inhibit treatment of organic compounds. A two-stage biofilter, with the first stage operated at low pH and an inorganic support medium, and the second operated at neutral pH with an organic support can eliminate the problem. A pilot-scale facility was operated on this principle. Comparisons were made among two-stage treatment, single-stage low pH treatment, and single-stage uncontrolled treatment to determine which of the strategies was most effective. In two-stage treatment the first stage did provide protection for the second, allowing it to operate at neutral pH. Single-stage low pH treatment was effective at removing sulfide and many organic compounds, and may be sufficient for many applications.
Estrogenic metabolites of alkylphenol polyethoxylates in secondary sewage effluents and rivers
Authors: Ahel M. , Molnar E. , Ibric S. , Giger W.
Published: May 2018

Degradation products of nonionic surfactants of the nonylphenol polyethoxylate type (NPnEO) were reported recently to be estrogenic to fish at low microgram per litre concentrations. These estrogenic metabolites, including nonylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) as well as their corresponding carboxylic acids (NP1EC and NP2EC), were measured during 1997 and 1998 in sewage effluents and ambient waters in Switzerland in order to assess the effects of risk reduction measures introduced in 1986. Lipophilic metabolites (NP+NP1EO+NP2EO) were found in the examined secondary sewage effluents mostly at concentrations from 1 to 5 μg/L, while elevated levels were found in those sewage treatment plants which receive industrial effluents from textile finishing plants. The concentrations of the lipophilic nonylphenolic compounds in rivers ranged mainly from 0.05 to 0.3 μg/L with NP being most abundant. The total concentration of the nonylphenoxy carboxylic acids was significantly higher than that of the lipophilic metabolites. Despite a significant decrease of the environmental exposure levels of all nonylphenolic compounds subsequent to the introduction of risk reduction measures, the total concentration of estrogenic metabolites often exceeded the predicted no effect concentration (PNEC) of 0.33 μg/L proposed in a risk assessment report to the European Union.
Distribution of endocrine disrupting semivolatile organic compounds in several compartments of a terrestrial ecosystem
Authors: Streck G. , Herrmann R.
Published: May 2018

Concentrations of semivolatile organic compounds – most of them known or suspected endocrine disrupters – were monitored in different compartments of a forested region in Northeast Bavaria. Considered compartments included precipitation (rain, snow), aerosol particles and vapour phase, soil and spruce needles (Picea abies). Investigated compounds comprised 4 phthalate acid esters, 14 polycyclic aromatic hydrocarbons (PAH) and 8 pesticides. While nearly all PAHs and phthalate acid esters were found in significant concentrations in the different compartments, pesticide concentrations were low, perhaps due to sampling in winter conditions. Regarding literature data about receptor affinity, the estrogen potential of the investigated compounds were evaluated.
Development of quantitative comparative cytotoxicity and genotoxicity assays for environmental hazardous chemicals
Authors: Plewa M. J. , Kargalioglu Y. , Vankerk D. , Minear R. A. , Wagner E. D.
Published: May 2018

Mammalian cell asays can provide toxicological information that may be more relevant to human risk asessment than commonly used microbial tests. Rapid, semi-automated, quantitative mammalian cell cytotoxicity and genotoxicity assays were developed to analyze drinking water disinfection by-products (DBPs). These assays employ 96-well microplates; selected DBPs were analyzed with cultured Chinese hamster ovary (CHO) cells. The concentration of the DBPs that repressed 50% of CHO cell growth with a 72 h exposure was calculated as the %C1/2 value. Using these values the rank order (from highest to lowest cytotoxicity) was bromonitromethane, dibromonitromethane, tribromonitromethane, bromoacetic acid, dibromoacetic acid, and tribromoacetic acid. Genotoxicity analyses of the DBPs were conducted using the single cell gel electrophoresis (SCGE) assay. This assay detects genomic DNA damage at the level of the individual nucleus. Using SCGE genotoxic potency the rank order was bromoacetic acid> dibromonitromethane>>bromonitromethane>dibromoacetic acid>tribromoacetic acid. The relative cytotoxicity and genotoxicity of these agents were compared with Salmonella typhimurium. Studies of specific DBPs in mammalian cell systems are important to compare the toxicity of these hazardous water contaminants. Such knowledge is necessary for risk assessment and to assist in the formulation of public regulatory policies that protect the environment and the public health.
Global transport rates and future prediction of hazardous materials: Pu and Cs – from Nagasaki to Canadian Arctic
Authors: Kudo A. , Zheng J. , Yamada R. , Tao G. , Sasaki T. , Sugahara M.
Published: May 2018

A historical man-made global pollution of hazardous materials occurred at Nagasaki, Japan on August 9, 1945 detonation of a plutonium (10–15 kg) atomic bomb. Recent advancements in analytical technology made it possible for artificial radionuclides released from the nuclear explosion to be detected in the Arctic ice core layer of 1945. The fission product, 137Cs (23.4 g or 7.44×1013 Bq), and unexpended fission material, 239+240Pu (8.8–13.8 kg or 2.22–3.49×1013 Bq), originating from the Nagasaki A-bomb were measured by collecting 10 ice cores on the Agassiz ice cap, Ellesmere Island, Canada.

The deposition rates were 20 mBq/cm2 for 137Cs and 0.16 mBq/cm2 for 239+240Pu, originating from Nagasaki. Assuming the radionuclides, excluding the amount deposited as local fallout, are deposited evenly throughout the northern hemisphere, a rate of 67% of the expected amount of 137Cs arrived at the Arctic while 1.1% of 239+240Pu reached the Arctic. The results suggest that different transport mechanisms exist for these two hazardous contaminants in the global transport system.

A non-reactive rare gas, such as neon and argon, can spread evenly throughout northern hemisphere, including Ellesmere island at the Canadian Arctic, while a reactive gas, sulfur dioxide (SO2) will not reach the ice cap. The measured global transport rates of 137Cs and 239+240Pu were 67% and 1.1%, respectively. These measured rates were for the historical man-made hazardous materials and probably obtained for the longest distance of global transport over 10,000 km. Assuming there was a consistency in climate for the next 10,000 years, the chronological anthropogenic deposits, mainly of 239+240Pu, could be detected in the ice layer between 97–98 m from the snow surface at 11,999 AD on the Agassiz ice cap. Even if there were no improvements in the radioactive analytical method used, the ice layers for the 1945–1980 period could still be easily identified with the present analytical technology. Hopefully this study will find a way to use our generation's artefacts for the benefit of our future descendants.
Biological treatment of mineral oil in a salty environment
Authors: Yang L. , Lai C.-T.
Published: May 2018

Mineral oil may be spilled into the marine or coastal environment through the discharges of ballast and bilge water, dry docking activities and tanker and non-tanker accidents to contaminate both of the seawater and coastline, especially in harbors. The unsuitable storage and disposal of wasted mineral oil may also contaminate saltified soil or brackish groundwater that have been polluted by salty wastes or intruded by seawater in coastal areas. In order to clean those contaminated sites, the mineral oil must be removed from the salty environment. In this study, a lab-scale aerobic biofilter-biotrickling tower system packed with particulate plastic media (1.5 cm, hexagon in shape) was used to treat the salty artificial wastewater polluted by mineral oil (diesel fuel) mixed with chemical dispersant (CPC OD-10) and inorganic nutrients. The volatile organic compounds (VOCs) escaped from the biofilter due to aeration was then treated by the biotrickling tower of the treatment system. According to the experimental results, the optimal removal efficiencies of the emulsified diesel in this salty water was found to be 95% controlled under concentrations as high as 1000 mg TOC/L of diesel in the influent and volumetric loading rate of 1.5 kg TOC/m3-day. The biodegradation rate constant (k) was measured to be 0.169 hr–1 for a first-order reaction assumed. As to the removal efficiency for VOCs, a low percentage of 68.2% was measured due to short hydraulic retention time (10 seconds) applied to the tower. However, only a small fraction (7.9%) of total amounts of diesel was measured as VOCs. The chemical dispersant used in this study was biodegradable, which could be used as a surfactant to emulsify the mineral oil into seawater for biological treatment. Due to short HRT applied to this aerobic biofilter-biotrickling tower treatment system, both the surface area and reactor volume required to build this treatment equipment are thus decreased to make it more easily set up in a mobile ship or truck. Thus, we may treat the mineral oil in marine or any other salty environment more conveniently.
Membrane filtration for preferential removal of emulsified oil from water
Authors: Leiknes T. , Semmens M.J.
Published: May 2018

The feasibility of using selective oil filtration (SOF) with microporous hollow fiber membranes for the separation and recovery of oil from spent cutting fluids was investigated. Two samples of water-based soluble cutting fluids made from petroleum products were tested. Characterization of the fluids was complicated due to proprietary information on the product and different use patterns. In general the fluids were found to be alkaline and comparable to mineral rich water. Emulsion stability was relatively high over the pH range tested. Preliminary tests showed the unit functioned primarily as an ultrafiltration (UF) unit due to wetting of the membranes by the high concentrations of emulsifying agents. To encourage SOF the cutting fluids were concentrated by UF by removing 80% of the water. Permeate collected during SOF of the concentrate contained an unstable “creamy” oil phase in the permeate which phase separated within 12 hours. The volume of the oil phase increased with decreasing pH. Results obtained suggest that separation is feasible if the conditions of operation are optimized. However, additional studies are needed to understand several of the factors that affect the performance of the process such as emulsion stability, concentration, membrane characteristics, module design and operation etc.
Effect of the operating parameters on the separation of metal chelates using low pressure reverse osmosis membrane (LPROM)
Authors: Ujang Z. , Anderson G.K.
Published: May 2018

This paper describes an investigation on the effect of operating parameters on the separation of metal chelates using LPROM. The objective of this study was to optimise the process of metal chelates removal by a LPROM using statistical factorial design. Factorial experiment by statistical design was applied, in which a central composite factorial design (half replicate) was used, then followed up by a star design to give a central composite factorial design. A bench-scale spiral wound configuration of sulphonated polysulphone LPROM was used at various operating conditions, i.e. operating conditions, solute concentrations, EDTA, pH and temperature. It has been shown experimentally that the effect of pressure is non-linear with respect to percentage of metal removal at different concentrations of metal ions in the feed solution. Observation of the response surface implies that the operating pressure was not the significant parameter in determining the percentage of zinc removal in the LPROM. The operating pressure, temperature and concentration of EDTA in the feed solution were the most significant parameters for permeate flux variation. It can also be concluded that for a given set of feed and experimental conditions, permeate flux increased linearly with operating pressure and temperature. The other parameters, i.e. the concentration of zinc in the feed solution and pH, were not statistically significant.
The removal of acrylonitrile from aqueous solution by Fenton's reagent and membrane filtration
Authors: Chang C.Y. , Chen S.H. , Chang J.S. , Wang C.C.
Published: May 2018

The removal of acrylonitrile by Fenton-precipitation and Fenton-microfiltration was investigated in this study. As for Fenton-precipitation, in the range of pH 2 to pH 4, TOC removal efficiency decreased with the increase in pH during the Fenton-precipitation of acrylonitrile. Fenton-microfiltration had a significant improvement on TOC removal at pH 3 and 4 as compared with Fenton-precipitation. The highest removal efficiency of 95% was obtained at pH 3 and the solution pH value had a significant effect on the total permeate quantity and the rate of accumulation. Experimental results led to the conclusion that the oxidation caused by Fenton's reagent was predominant at pH 2. On the contrary, coagulation was most significant at pH 3 and 4. The results indicated the superiority of the Fenton-microfiltration process as compared with Fenton-precipitation process for the removal of acrylonitrile from water.
A new design of microfiltration system and application to wastewater treatment
Authors: Chang D.J. , Chen S.H. , Chang C.Y. , Lin S.S. , Chang J.S.
Published: May 2018

A new microfiltration system with two sets of dead-end membrane cells and driven by a piston force system was designed in this study. In this system, suction of the filtrate was through the membrane in the reverse direction with a piston to backwash and reduce membrane fouling. In addition, after a few forward-reverse filtration cycles, the concentrated suspension of particles or solute on the retentate side was discharged into the stock tank under the cross flow condition. For maximizing the filtrate volume, it was found that the optimum times for forward and reverse filtration were 90 s and 3 s respectively, and the discharge frequency of retentate was 1 time per cycle. Moreover, it was also found that the filtrate volume increased with an increase in particle size and membrane pore size but decreased with an increase in feed concentration. Furthermore, an optimal filtrate volume existed on effecting the pressure drop. Finally, it could be used efficiently to treat and recycle the backwash wastewater from a rapid sand filter by a membrane with pore size of 0.1 and 0.22 μm.
The use of algal-bacterial biofilms to enhance nitrification rates in lagoons: experience under laboratory and pilot-scale conditions
Authors: McLean B. M. , Baskaran K. , Connor M. A.
Published: May 2018

Investigations were undertaken at the Western Treatment Plant (WTP), near Melbourne, Australia, to find ways of increasing overall ammonia and nitrogen removal rates in the WTP lagoon systems. Immobilisation of nitrifying bacteria in biofilms was one approach explored. Preliminary tests showed that algal/bacterial biofilms capable of achieving ammonia removal rates of 3 to 4 μg N/cm2·h would form on support surfaces immersed in the WTP lagoons. A laboratory-scale investigation was carried out to characterise the influence of parameters such as pH, temperature, COD level, dissolved oxygen concentration and incubation depth on biofilm performance. This study was followed by a pilot-scale investigation in a series of experimental ponds at the WTP. This compared the performance of three ponds, two containing 9360 m2 and 18240 m2 respectively of a geotextile biofilm support material and one containing no biofilm support material (the control pond). Ammonia removal rates comparable to those obtained in the preliminary tests were obtained when the biofilm support material was within the top 500 mm of the lagoon, i.e. in the photic zone. COD and suspended solids levels in the effluents from the biofilm containing ponds were substantially lower than those in the control pond effluent.
Treatment performance of newly developed johkasous with membrane separation
Authors: Ohmori H. , Yahashi T. , Furukawa Y. , Kawamura K. , Yamamoto Y.
Published: May 2018

In order to verify the treatment performance of newly developed johkasous with membrane separation, for household use, three johkasous of different types were used for experimental study. It was found that each of these johkasous has a high treatment performance for removing BOD, nitrogen, and can be operated steadily by monitoring the function and maintaining the devices at every three months and by withdrawing accumulated sludge at every six months. It was also found that periodical cleaning of the membrane by sodium hypochlorite solution and neutralizing cleaning wastewater by sodium thiosulfate solution at every six months is important to maintain a steady permeability of the membranes. No adverse effects on treatment performance was observed by leached sodium hypochlorite solution from the membrane at membrane cleaning.
Comparison between algae-based and duckweed-based wastewater treatment: differences in environmental conditions and nitrogen transformations
Authors: Zimmo O. R. , Al Sa'ed R. , Gijzen H.
Published: May 2018

In laboratory-scale batch experiments, duckweed (Limna gibba)-based and algae-based wastewater containers have been monitored over 15 days in two experiments with different initial total nitrogen concentrations of 50 (experiment 1) and 100 mg-N/L (experiment 2). Clear differences in environmental conditions were observed. High dissolved oxygen (DO) concentrations were observed in the algae-based ,compared to duckweed-based, containers. In the algae-based containers the DO range was between 2.1 to 6.6 mg/L and 1.2 to 4.3 mg/L in experiment 1 and 2, respectively, whereas in the duckweed-based containers DO ranged between 1.1 to 3 mg/l and 0.5 to 2.1 mg/L. Higher pH values were measured in algae-based due to algal photosynthetic activity compared to duckweed-based containers where the duckweed mat prevented sunlight penetration and hence algal development. In algae-based containers, the pH range was 7.9 to 8.6 and 8.1 to 8.4 in experiments 1 and 2, respectively, and 7.3 to 7.5 and 7 to 7.6 in the duckweed-based containers. Depending on initial nitrogen concentrations, duckweed-based containers removed between 42%–62% of total nitrogen and between 56%–95% of Kjeldahl nitrogen from the wastewater, while algae-based containers removed between 45%–48% and 48%–58% of total nitrogen and Kjeldahl nitrogen, respectively. Nitrogen loss, probably due to denitrification and ammonia volatilisation, represents 40% of the total nitrogen content of algae-based and duckweed-based containers. However, in duckweed-based containers only 28% of N-loss was observed in containers with higher initial N-content. This study demonstrates that there were differences in environmental conditions in algae-based and duckweed-based containers, which have caused differences in nitrogen transformation mechanisms.
Petro® concept: a tentative approach to biological phosphorus removal incorporating waste stabilisation ponds
Authors: Shipin O. V. , Meiring P. G. , Hoffmann J. R.
Published: May 2018

Ponding which is usually considered a low tech process can be successfully integrated with downstream Biological Nutrient Removal (BNR) facility. The PETRO system incorporating ponds and downstream trickling filter (TF) or activated sludge process (ASP) is a technology which offers simplicity of O and M combined with biological removal of P and N. It is feasible to produce in a primary facultative pond with a deep fermentation pit quantities of readily biodegradable substrates sufficient to meet the requirements of phosphate accumulating organisms (PAO) in a downstream BNR facility. Malodorous conditions are dealt with by high rate recirculation. This novel low tech approach is a step towards a more straightforward BNR process. PETRO concept features phenomenon of algae-assisted chemical P-removal in activated sludge reactor. The process results in precipitation of inorganic phosphates apparently in a form of calcium/magnesium salts. Possible mechanism of this additional process which removes up to several milligrams per litre of inorganic P is discussed.
Study on a sequencing batch membrane bioreactor for wastewater treatment
Authors: Ng W.J. , Ong S.L. , Gomez M.J. , Hu J.Y. , Fan X.J.
Published: May 2018

This study investigated the effect of MLSS concentration in a sequencing batch membrane bioreactor on COD and nitrogen removal as well as flux. Two values of MLSS (5 g/l and 10 g/l) were investigated in this study. The strength of the feed was varied to achieve a target F/M ratio of 0.5 based on COD. Accordingly, the concentration of COD was determined as 3.5 and 7.0 g/l for the 5 and 10 g/l MLSS targets, respectively. The test results showed that an average COD removal of 98.5% was achievable. However, it was noted that nitrification inhibition occurred. Nitrification inhibition occurred because of two factors, namely high NH4+–N concentration and high DO demand. High NH4+–N in the feed led to the inhibition of nitratation and thus high nitrites are found in the effluent. High DO demand due to high feed COD concentration led to an extended period with low DO levels inside the reactor thus retarding the conversion of NH4+–N. The increase in the MLSS concentration from 5 to 10 g/l led to a decrease in the average flux from11.1 l/m2 · h to 9.6 l/m2 · h. An increase in aeration, from 2.0 to 8.0 l/min, did not lead to any significant improvement in terms of fouling.
Influence of important operational parameters on performance of a membrane biological reactor
Authors: Yoon S-H. , Kim H-S. , Park J-K. , Kim H. , Sung J-Y.
Published: May 2018

In order to elucidate optimum operational parameters, five series of experiments with bench scale “A/O and MBR (membrane biological reactor)” devices were carried out. The HRTs of each anoxic and oxic bioreactor were maintained for 2˜6 h and for 3˜6 h, respectively. The internal recycle ratios were also changed from 100% to 300% of the influent feeding rate by peristaltic pump. There were no recognizable differences in the values of BOD removal efficiency, being around 99%, in the series of experiments. The same was true for T–N removal efficiency, which ranged about 60%. The similarity of the serial experiments for each parameter indicates that the extraordinarily high concentration of microorganisms in the bioreactor, i.e. 10,000–15,000 mg/l, strongly controls the entire process regardless of any moderate changes of the operational parameters.
Ultrafiltration of activated sludge with ceramic membranes in a cross-flow membrane bioreactor process
Authors: Fan X-j. , Urbain V. , Qian Y. , Manem J.
Published: May 2018

A cross-flow membrane bioreactor (MBR) for raw municipal wastewater treatment, consisting of a suspended growth bioreactor and a ceramic membrane ultrafiltration unit, was run over a period of more than 300 days in a wastewater treatment plant (WWTP). Sludge Retention Times (SRT) of 20, 10 and 5 days, respectively, and Hydraulic Retention Times (HRT) of 15 and 7.5 hours were tested. Membrane fouling was found to be a function of SRT and permeate flux. Under an SRT of 20 days and flux of 71 l/m2\ · h at 30°C, the MBR was successfully run over 70 days without the need for chemical cleaning. However chemical cleaning had to be undertaken every 3–5 days at shorter sludge retention times (typically an SRT of five days and a flux of 143 l/m2\ · h at 30°C). In this study, fouling materials were removed efficiently through chemical cleaning, with an average permeablity recovery of 87±11%.
Sludge accumulation and methanogenic activity in an anaerobic lagoon
Authors: Paing J. , Picot B. , Sambuco J. P. , Rambaud A.
Published: May 2018

Sludge accumulation and the characteristics of anaerobic digestion in sludge had been investigated in a primary anaerobic lagoon. Methanogenic potential of sludge was evaluated by an anaerobic digestion test which measured the methane production rate. Sludge was sampled at several points in the lagoon to determine spatial variations and with a monthly frequency from the start-up of the lagoon to observe the development of anaerobic degradation. Maximum amounts of sludge accumulated near the inlet. The mean methane production of sludge was 2.9 ml gVS–1 d–1. Sludge near the outlet presented a greater methanogenic activity and a lesser concentration of volatile fatty acids than near the inlet. The different stages of anaerobic degradation were spatially separated, acidogenesis near the inlet and methanogenesis near the outlet. This staged distribution seemed to increase efficiency of anaerobic fermentation compared with septic tanks. Methane release at the surface of the lagoon was estimated to be very heterogeneous with a mean of 25 l m–2 d–1. The development of performance and sludge characteristics showed the rapid beginning of methanogenesis, three months after the start-up of the anaerobic lagoon. Considering the volume of accumulated sludge, it could however be expected that methanogenic activity would further increase.
Application of MBR to an easily installed municipal wastewater treatment plant
Authors: Ogoshi M. , Suzuki Y.
Published: May 2018

An easily installed wastewater treatment plant was developed using an MBR process. The plant consists of inlet pumps, automatic fine screen, a main reactor in which aerator-mixer and MF membrane separators are installed and a control board. The main reactor is a sheeted pond which is easily constructed on-site by an excavation. As a result, the installation of this plant is easy and inexpensive, operation is easy, yet the effluent quality is high. The 50 m3/d pilot plant was constructed in our experimental facility in Ibaraki Pref., and operated from January 1997 to April 1998 to evaluate performance, stability and the ease of separation and installation of each unit. The results were satisfactory in all areas, except the durability of membrane permeability in the latter half of the experiment. For both hollow fibre type and plate type, membrane permeability immediately decreased due to the deposit of concentrated sludge cake on the surface, even though continuous bubble washing had been made. Hence,drastic improvement is needed in the way of sludge deposit control on the membrane surface. This is the key for the developed system to become a practical one.
Floating geomembrane covers for odour control and biogas collection and utilization in municipal lagoons
Authors: DeGarie C. J. , Crapper T. , Howe B. M. , Burke B. F. , McCarthy P. J.
Published: May 2018

The use of anaerobic lagoons as the first pond in waste stabilization pond systems in tropical and warm-temperature climates is considered a highly cost-effective and practical way to treat municipal wastewater. These anaerobic ponds, designed with hydraulic residence times of up to six days, can effect BOD5 removals of 60 to 80%. The subsequent aerobic stabilization pond surface area is greatly reduced over systems designed without anaerobic treatment up front due to the organic load reduction occurring anaerobically. In lagoon systems with mechanical aeration, operation costs can be greatly reduced.

While odour is a concern with anaerobic treatment, anaerobic ponds treating municipal wastewater can be designed to be relatively odour-free given sufficiently low wastewater sulfate concentrations. However, when sulfate concentrations are high, or when odour control or greenhouse gas emissions are significant issues, or when the wastewater is relatively high in organic strength resulting in commercial production of methane gas, anaerobic lagoons can be covered, and the biogas collected and burned both to produce energy and reduce emissions and odour.

The City of Melbourne treats approximately 50% of its municipal wastewater at the Western Treatment Plant in waste stabilization ponds designed with anaerobic ponds as the first pond in the system. Each of three pond systems at the Western Treatment Plant receives an average dry weather flow of 120,000 m3/d with an average strength of 400 mg/L BOD5. This paper describes the design, installation and commissioning of two 3.9 hectare floating, self draining, geomembrane covers on the anaerobic section of two of these lagoon systems. Biogas collection and utilization were an important part of the installation. A description of how the biogas is collected, the quantities generated and an overview of the control system used to operate the biogas handling facility is also included. Particular emphasis was placed on maximizing biogas utilization in design of the biogas control system.
Application of immersed-type membrane separation activated sludge process to municipal wastewater treatment
Authors: Murakami T. , Usui J. , Takamura K. , Yoshikawa T.
Published: May 2018

Pilot plant studies were carried out using actual wastewater to investigate the applicability of a membrane separation activated sludge (MSAS) process to municipal wastewater treatment. A small-scale pilot plant (6.7 m3/day) with immersed flat sheet membrane was operated at the flux of 0.4 m3/m2/day. Continuous operation for 140 days without chemical cleaning was possible. Average Sludge production ratio was about 0.6. No significant difference was observed in the dewaterability between membrane separation activated sludge and conventional activated sludge at the CST test. Large-scale pilot plants (30–70 m3/day) with five types of membrane were also operated. In these plants nitrogen removal by nitrification and denitrification, and phosphorus removal by coagulant addition were carried out. Stable operation with HRT of six hours, flux of 0.4–0.8 m3/m2/day was possible, the average nitrogen and phosphorus removal efficiency being more than 80 and 95%, respectively.
Hybrid modelling of anaerobic wastewater treatment processes
Authors: Kamara A. , Bernard O. , Genovesi A. , Dochain D. , Benhammou A. , Steyer J.-P.
Published: May 2018

This paper presents a hybrid approach for the modelling of an anaerobic digestion process. The hybrid model combines a feedforward network, describing the bacterial kinetics, and the a priori knowledge based on the mass balances of the process components. We have considered an architecture which incorporates the neural network as a static model of unmeasured process parameters (kinetic growth rate) and an integrator for the dynamic representation of the process using a set of dynamic differential equations. The paper contains a description of the neural network component training procedure. The performance of this approach is illustrated with experimental data.
Influence of primary sedimentation on pre-denitrification system performances
Authors: Esposito G. , Bastianutti C. , Bortone G. , Pirozzi F. , Sgroi S.
Published: May 2018

The effects of suppressing primary sedimentation on nitrogen removal efficiency of a pre-denitrification system have been evaluated for a large municipal wastewater treatment plant. Simulations have been carried out using the STOAT model. For both the process schemes with and without primary sedimentation, nitrification efficiencies are calculated for increasing influent loads of COD, total N and suspended solids. The sensitivity analysis shows that for the usual carbon to nitrogen ratios in the raw influent both the process schemes allow the requested removal efficiencies, whereas for significantly high C/N ratios the scheme with primary sedimentation is preferable.
Retrofitting SBR systems to nutrient removal in sensitive tourist areas
Authors: Tasil R. , Artan N. , Orhon D.
Published: May 2018

Retrofitting of existing SBR systems for nutrient removal is evaluated and defined for small communities in sensitive coastal areas, with seasonal fluctuations in wastewater quantity and quality. The proposed approach is developed by means of basic process stoichiometry and verified using ASM2d. The efficiency of retrofitting is found to rely on the delicate balance between the overall sludge age, the initial settled sludge volume in the reactor, and the ratio of the initial volume to the feed volume in each cycle, a parameter corresponding to the recycle ratio in continuous systems.