bluuebunny/crossref_metadata_2025 huggingface dataset:
Removal of phosphorus from wastewater by activated alumina adsorbent
Authors: Hano Tadashi , Takanashi Hirokazu , Hirata Makoto , Urano Kohei , Eto Shunji
Published: May 2018

The adsorption characteristics of activated alumina treated with aluminum sulfate were studied to develop a new removal process for low concentration phosphorus in the waters of rivers and lakes. The equilibrium study showed that the adsorption capacity was enhanced about 1.7-fold by treating with aluminum sulfate. The effective intraparticle diffusion coefficients, determined by the Boyd's method based on batch runs, were hardly affected by such a low phosphorus concentration as observed in the water of rivers and lakes under investigation. The temperature dependence of the intraparticle diffusion coefficients based on the concentration in solid showed the activation energy of 29.7kJ·mol−1, which was a little higher than that in usual pore diffusion. The maximum continuous operation term (regeneration cycle) of the present phosphorus adsorption system was estimated. Under the conditions of influent phosphorus concentration of 0.1 g·m−3, removal extent of 90%, particle size of 2 × 10−3m, temperature of 298K and space velocity of 1.39 × 10−3s−1 (5h−1), the present removal system remained effective for about 500 days.
Characteristics and adsorption properties of iron-coated sand
Authors: Lo Shang-Lien , Jeng Hung-Te , Lai Chin-Hsing
Published: May 2018

This study was conducted to develop a process for coating hydrated iron oxide on the surface of quartz sand to utilize the adsorbent properties of the coating and the filtration properties of the sand. Three coating parameters were investigated: pH, Fe concentration at which iron oxide was prepared, and the coating temperature. A Scanning Electron Microscope (SEM) and X-Ray Diffractometer (XRD) were used to observe the surface properties of the coated layer. Acid resistance was used to evaluate the attachment strength of the coated layer. Batch adsorption tests were performed to compare the effects of each coating parameter on the adsorption of heavy metals on the coated layer. Energy Dispersive Analysis of X-ray (EDAX) was used for characterizing metal adsorption sites on the iron-coated sand. The results indicated that the coated sand had more pores and higher specific surface area because of the attachment of iron oxide. The coated sand produced at higher pH(coating) had better adsorption efficiencies of metals but had worse acid resistance. A high-temperature coating process enhanced the stability of the oxide coatings. Comparing heavy metal removal by adsorption on iron-coated sand and chemical precipitation, adsorption was shown to be capable of removing heavy metals over a wider pH range and to much lower levels than precipitation. The results from EDAX analysis showed that copper ions were chemisorbed on the surface of iron-coated sand.
Solubility and adsorption behaviors of chlorophenols in the presence of surfactant
Authors: Liu J. C. , Chang P. S.
Published: May 2018

The solubility of chlorophenols as affected by surfactant was investigated. Three kinds of surfactant, sodium dodecyl sulfate, Triton X-100, and Brij 35, were utilized. The solubilization of chlorophenols by surfactant follows the order of 2,4,6-trichlorophenol > 2,4-dichlorophenol > 2,6-dichlorophenol > 2-chlorophenol; and the critical micelle concentration is an important index. The adsorption reactions of 2,4-dichlorophenol and 2,4,6- trichlorophenol onto hydrous montmorillonite in the presence of surfactant were examined. The presence of surfactant decreased the adsorption of chlorophenols significantly. The roles of hydrophobicity of chlorophenols in solubilization and adsorption behaviors are discussed.
Transport of organochlorine pesticides in soil columns enhanced by dissolved organic carbon
Authors: Ding Jiann-Yuan , Wu Shian-Chee
Published: May 2018

The objective of this study is to quantify the effects of humic acid solution infiltration on the transport of organochlorine pesticides (OCPs) in soil columns using a three-phase transport model. From experimental results, it is found that the dissolved organic carbon enhances the transport of OCPs in the soil columns. In the OCPs-only column, the concentration profiles of OCPs can be simulated well using a two-phase transport model with numerical method or analytical solution. In the OCPs-DOC column, the migrations of aldrin, DDT and its daughter compounds are faster than those in the OCPs-only column. The simulation with the three-phase model is more accurate than that with the two-phase model. In addition, significant decrease of the fluid pore velocities of the OCPs-DOC column was found. When DOC leachate is applied for remediation of soil or groundwater pollution, the decrease of mean pore velocities will be a crucial affecting factor.
Changes of adsorption capacity and pore distribution of biological activated carbon on advanced water treatment
Authors: Kameya Takashi , Hada Tatsuya , Urano Kohei
Published: May 2018

Several problems such as unpleasant odor, taste and toxic halogenated organic compounds which are produced by the reaction of organic substances with chlorine that is used for disinfection have occurred in water purification plant for drinking water. Advanced water treatment with biological activated carbon (BAC) has been focused on, but there are few papers about pore volume decrease of activated carbon in BAC. In this study, the changes in cumulative TOC removal and pore volume distribution for two types of activated carbon from a bench-scale apparatus and a mini-column apparatus, to which river water was supplied after coagulation-sedimentation for a period of over 1200 days, were investigated. Adsorption abilities decreased considerably after ca 1000 days and the activated carbons became like sand. The cumulative TOC removals by the adsorption effect were asymptotic to constant values for each empty bed contact time. Though the removal efficiencies for both the activated carbons were approximately equivalent, the pore volume decreases were not uniform. The volume of smaller pores under 2 nm in diameter mainly decreased. Accumulations of minerals such as aluminium and calcium were small, and the pore volume decreases were mainly caused by the accumulation of organic substances. Almost all of the organic substances that accumulated in the activated carbon could be extracted by sodium hydroxide solution. The mean density of the organic substances that accumulated in the activated carbon was estimated to be 0.91 g/ml. Since the pore volume decrease of the activated carbon was small compared with the removal amounts by the adsorption effect, a large amount of organic substances that had adsorbed once disappeared and the pore volume of the activated carbon was regenerated.
Supercritical CO2 regeneration of activated carbon loaded with organic adsorbates
Authors: Chihara Kazuyuki , Oomori Kanji , Oono Takao , Mochizuki Yosuke
Published: May 2018

Supercritical CO2 regeneration is one of the possibilities for spent carbon regeneration loaded with some organics. Here, adsorption equilibrium and adsorption dynamics were evaluated for some typical organic pollutants under some supercritical CO2 conditions. A supercritical CO2 chromatograph packed with activated carbon (F-400, CAL) was used to detect the pulse responses of organics, which were analyzed by moment analysis. Adsorption equilibrium constants of some organics varied with CO2 density and their boiling points. Possibility of regeneration of each substance was discussed. Cost estimation was necessary and was the key point of this technique.
Analysis of effluent charge for wastewater treatment plants in industrial districts
Authors: Lo Shang-Lien , Chen Li-Ru
Published: May 2018

Three cost functions of wastewater treatment plants in industrial districts were analyzed and discussed. From the results, the effluent charge rate can be proposed in order to internalize parts of the external cost of wastewater pollution. The charge base of the effluent charge shall be the total pollutant amounts in the effluent. The charge rate shall be set up according to the results of cost functions for various treatment efficiencies. The marginal cost of NT$790 (US$30.4) per noxiousness unit (F=1,000 m3/day, Q=5,000 noxiousness units/year, treatment efficiency = 90%) was recommended to be the initial charge rate. This cost should be updated regularly and the charge rate should be raised according annually.
Water conservation and pollution control for intensive prawn farms
Authors: Chin K. K. , Ong S. L.
Published: May 2018

Hundreds of fish and prawn farms were constructed in the past decades. Many of these farms have ceased operation mainly due to the outbreak of diseases. With population increase, rapid urbanization and industrialization, water quality at the estuary and coastal regions where most of the fish and prawn farms are located is deteriorating. Treatment and recycling of water are essential to maintain the water quality at an acceptable level. A system consisting of preliminary settling, biofiltration, secondary settling and final polishing with a biofilter was tested in an experimental farm. Water quality was maintained at relatively good level at the cultivating pond after 120-day growing period. The growing facilities continued to show good performances after 4 growing cycles with a 2-week rest period between each cycle. Similar system was installed at a 26-hectare farm site having several ponds with sizes varying from 0.7 to 2.5 hectares. No disease outbreak was encountered after the installation of the treatment and recycling facilities.
Effect of particle concentration on the entire cycle of filtration
Authors: Prasanthi H. , Vigneswaran S. , Dharmappa H. B.
Published: May 2018

Influent particle concentration is one of the physical parameters that influence the overall performance of a deep bed filter. Natural waters with varying turbidity have varying effect on filtration. Experimental and theoretical studies on the effect of concentration on clean bed filter efficiency and ripening stage efficiency have been reported in the literature. However, a comprehensive study on the effect of influent concentration on the transient stage of filtration is not documented. In addition, it is not understood in what units the concentration should be expressed in the mathematical models: the mass, number or surface area of the particles?

In this present study, submicron polystyrene latex beads of sizes 0.46 μm and 0.825 μm were used to study the effect of concentration on the entire cycle of filtration. Experiments were carried out at constant mass, number and surface area as influent concentrations in order to observe the variation in filtration of the two sizes of particle.

At constant mass concentrations, the initial removal was found to be higher for smaller particles (0.46 μm) (in the submicron range); but when the number or surface area of particles was considered, it was found to be higher for larger particles (0.825 μm). The transient stage removal was found to increase with an increase in particle size, either with constant mass, number or surface area as an influent concentration. The Vigneswaran and Chang (1986) model was used to quantify the results. The model parameters estimated using the experimental results are useful in quantifying and understanding the performance of the filter.
Application of the IAWQ activated sludge model to nutrient removal process
Authors: Mino T. , San Pedro D. C. , Yamamoto S. , Matsuo T.
Published: May 2018

IAWQ Activated Sludge Model No.2, with the parameter values recommended by the IAWQ Task Group, was capable of predicting the behavior of a nutrient removal activated sludge pilot plant in Japan rather well except for the profile of NH4-N and NOx-N. The model was calibrated for the process and procedures for the calibration of the model are proposed. By applying the proposed calibration procedures, Activated Sludge Model No.2 has been satisfactorily calibrated to simulate the steady state behavior of the process in terms of organic matter and nitrogen removal. but, sometimes, selection of the specific growth rate of nitrifiers gives very sensitive effect on nitrate concentration in the effluent. It is indicated that the rate of anaerobic processes is affected by hydrolysis of particulate organic or slowly biodegradable substrates, and the hydrolysis can be the rate limiting step of the removal of organic matters or, sometimes, nitrogen and phosphorus. At the moment, it is rather risky to estimate the anaerobic hydrolysis rate, the anaerobic substrate uptake rate by phosphate accumulating organisms and the PHA yield with respect to polyphosphate utilization simultaneously only by using static data. The present case shows how relevant calibration procedures can be developed with limited static data.
Rotating biological contactors for wastewater treatment in an equatorial climate
Authors: Wilson Francis , Lee Wei Meng
Published: May 2018

The purpose of the study was to investigate the use of the Rotating Biological Contactor (RBC) to treat high strength wastewater in an equatorial climate. Total Organic Carbon, BOD and COD were used as analytical parameters to determine the efficiency of treatment of the wastewater, using high influent concentrations and high loading rates with a laboratory scale rotating disk system operating under ambient temperatures in Singapore. The effect of recirculation of the effluent was also studied. The results indicated that the RBC system could produce high treatment efficiencies at high ambient temperatures, however there were problems with first stage due to the high reaction rate. The Stover-Kincannon relationship appeared to adequately model the process when TOC was used as the major analytical parameter for loading rates up to 20 g m−3 d−1. Higher loading rates produced first-stage problems and lower removal efficiencies. Recirculation had little effect on the treatment efficiency at low loading rates.
Exploring zero discharge potentials for the sustainability of a bottle washing plant
Authors: Visvanathan C. , Hufemia Anna Marie M.
Published: May 2018

The beverage industry which requires large amounts of good quality water in their processes is a major contributor to the problem of excessive pumping from existing aquifers in Thailand. In view of a government restriction on groundwater withdrawal, an overall water management plan was drawn for the sustainability of a softdrink plant in Bangkok which depends solely on a deepwell source for its water needs. Technologies that can recover water for reuse, minimize raw water input and consequently lead to zero discharge were identified.

The overall water balance drawn for this plant revealed that 76% of the raw water consumed daily ends up in the biological wastewater treatment plant (WWTP). A large portion (40%) of this wastewater is generated from the bottle-washing units. By employing microfiltration for polishing of the WWTP effluent, the plant can recover process water for reuse such that, groundwater input is reduced by 40% and liquid discharged to the receiving water by 56%.

There are two proposed strategies for recovering rinse water from the bottle-washing units. A microfiltration-reverse osmosis system will purify the rinse water for reuse in the bottle washing process, thereby reducing raw water consumption further to 58% and the liquid discharge by 81.5%. On the other hand, a dual filter media-ion exchange system can reduce raw water input to 57% and the liquid discharge by 80.5%.
Advanced anaerobic wastewater treatment in the near future
Authors: Lettinga G. , Field J. , van Lier J. , Zeeman G. , Hulshoff Pol L. W.
Published: May 2018

New insights into the anaerobic degradation of very different categories of compounds, and into process and reactor technology will lead to very promising new generations of anaerobic treatment system, such as ‘Expanded Granular Sludge Bed’ (EGSB) and ‘Staged Multi-Phase Anaerobic’ (MPSA) reactor systems. These concepts will provide a higher efficiency at higher loading rates, are applicable for extreme environmental conditions (e.g. low and high temperatures) and to inhibitory compounds. Moreover, by integrating the anaerobic process with other biological methods (sulphate reduction, micro-aerophilic organisms) and with physical-chemical methods, a complete treatment of the wastewater can be accomplished at very low costs, while at the same time valuable components can be recovered for reuse.
Micropollutants: a bottleneck in sustainable wastewater treatment
Authors: Janssens I. , Tanghe T. , Verstraete W.
Published: May 2018

Every year a variety of xenobiotic chemicals as pesticides, dyes,… are introduced on a very large scale. The majority of these compounds have a rather poor biodegradability. Hence, fresh water resources become more and more contaminated with micro-quantities of these man-made pollutants. Moreover, some of these obscure pollutants may have the undesirable capability of having oestrogenic activity on various high forms of life.

This paper deals with the problems of micropollutants in drinking water production and wastewater treatment. The biocatalytic properties of microorganisms can be limiting for several reasons such as lower threshold values for metabolism, insufficient free energy change or inadequate metabolic knowledge base in the microbial cell or community.

The limiting biodegradative capacity of natural microbial associations necessitates the development of more integrated water treatment and management. Research is necessary on two levels i.e. the search for biotechnological processes able to remove such chemicals through engineering of pathways and microbial associations, and the need for reliable biosensors able to generate information on residual microorganics. Trends such as improved biocatalysis and accurate process control are of major significance. However, a clear-cut scientific and political endorsement of the necessity to use reclaimed wastewater is of prime importance to evolve towards sustainable water treatment and management.
Mineralisation of 1,2-dibromoethane and other brominated aliphatics under aerobic conditions
Authors: Freitas dos Santos Luisa M. , Livingston Andrew G.
Published: May 2018

1,2-dibromoethane (DBE) is a common environmental contaminant; it is potentially carcinogenic and has been detected in soil and groundwater supplies. Most of the biodegradation studies to date have been performed under anaerobic conditions or in the context of soil remediation, where the pollutant concentration was in the ppb range. The aim of this work was to find a bacterial culture (axenic or mixed) capable of complete aerobic mineralisation of concentrations of DBE up to 1 g L−1 under well controlled laboratory conditions. A mixed culture capable of degrading DBE as a sole source of carbon has been enriched. In order to verify biodegradation, formation of biodegradation products as well as the disappearance of DBE were measured. The ability of this culture to degrade other chlorinated and brominated compounds has also been tested. Successful degradation of bromoethane, bromoethanol and bromochloroethane was achieved.
Membrane bioreactors for wastewater treatment: the state of the art and new developments
Authors: van Dijk L. , Roncken G. C. G.
Published: May 2018

The combination of membrane separation technology and bioreactors has lead to a new focus on wastewater treatment. The application of membranes has led to very compact wastewater treatment systems with an excellent effluent quality. For concentrated wastewaters, like industrial streams and landfill leachate the membrane bioreactor has been applied at full scale successfully. The relatively high energy requirements have hindered the wide spread application of membrane bioreactors. Using new membrane techniques, like transfer flow modules, creates the possibilities of a more widespread application. This opens possibilities for far going reuse of wastewater, both industrial and municipal, decrease in sludge production and small-footprint bioreactors for less concentrated wastewater streams.
Biocatalytic oxidation of polycyclic aromatic hydrocarbons in media containing organic solvents
Authors: Torres Eduardo , Tinoco Raunel , Vazquez-Duhalt Rafael
Published: May 2018

Lignin peroxidase, cytochrome c and haemoglobin were tested for oxidation of polycyclic aromatic hydrocarbon (PAH) in the presence of hydrogen peroxide. The reaction mixture Contained water-miscible organic solvents in order to reduce the mass transfer limitation of hydrophobic substrates. The reaction products from all three haemoproteins were mainly quinones, suggesting the same oxidation mechanism for the three biocatalysts. The haeme prosthetic group must have located in a protein environment for it to catalyze these reactions, and only certain types of protein environment are able to induce this type of haemebased catalytic activity. The solvent hydrophobicity is a factor affecting the biocatalysis in organic media. Substrate partitioning between the active site (haeme) and the bulk solvent is the main factor of the biocatalytic behaviour in organic solvent mixtures. Site-directed mutagenesis of yeast cytochrome c significantly altered the kinetic behaviour of the protein. The Gly82;Thr 102 variant was 10 times more active and showed a catalytic efficiency 10-fold greater than the wild-type iso-1-cytochrome c. These results suggest that it is possible to design a new biocatalyst for environmental purposes.
Enhanced biological phosphate removal: modelling and design in theory and practice
Authors: Scheer Holger , Seyfried Carl F.
Published: May 2018

The need for Enhanced Biological Phosphorus Removal (EBPR) in wastewater treatment plants (WTP) is increasing so that the development of steady state design models for WTPs using nitrification, denitrification and EBPR becomes more and more important. In developing such a model, theoretical and practical aspects must be considered if the qualitative and quantitative statements regarding the influence of various wastewater conditions (e.g. substrate composition) and surrounding conditions (e.g. influence of nitrate, duration of the anaerobic contact time) affecting EBPR shall be described. The presented EBPR design model is verified using data from various WTPs (e.g. Berlin-Ruhleben) currently using EBPR practices. Sensitivity studies for the most important influencing parameters and surrounding conditions are done, using fictious plant data. Recommendations are given, based on these studies, for the optimization of the EBPR process. These recommendation illustrates the most effective means towards improving the surrounding conditions for EBPR (e.g. increase of amount of readily available organic substrate, decrease of sludge age) with regard to an increase of the biologically removed phosphorus concentration.
High nutrient removal in the three-sludge sewage treatment system: results and economic evaluation
Authors: Marsman E. H. , Roeleveld P. J. , Rensink J. H.
Published: May 2018

The Three-sludge sewage treatment system proved to be a stable process for the treatment of wastewater. This new concept consists of three separated bioreactors. Biological removal of phosphorus and COD takes place in the first high loaded activated sludge bioreactor with an intermediate settler. The second reactor is a nitrifying biofilm reactor. Nitrate is removed in the third denitrifying biofilm reactor. Pilot plant research (scale 2–3 p.e.) showed that at a constant flow rate during night and day a minimal hydraulic retention time of 10.4 hours, inclusive, the settler, could be obtained and yet still the stringent effluent standards (10 mg N/l and 1 mg P/l) were met. At a dynamic flow rate with day/night rhythm and at a storm-weather peak flow rate of 2.5 times the dry weather flow rate the standards were still met. However, at a flow rate of three times the dry-weather flow rate the concentration of Ptotal increased which indicates instability of the dephosphatating bioreactor under the set process conditions. The nitrification and the denitrification capacity remained excellent. The economical evaluation showed that the Three-sludge sewage treatment system can compete with conventional low loaded activated sludge plants in The Netherlands. Moreover, this advanced technology only occupies 40% of the space of conventional plants.
The modified renphosystem: a high biological nutrient removal system
Authors: Rensink J. H. , van der Ven J. , van Pamelen G. , Fedder F. , Majoor E.
Published: May 2018

Pilot plant studies on high biological nutrient removal and using settled domestic wastewaters have been carried out with the so-called Modified Renphosystem. The system consists of a bioreactor which has been divided into four zones: anaerobic, aerobic, anoxic and aerobic, respectively. In the by-pass of the bioreactor a part of the return sludge was stripped in a stripper tank. The process of P-release was accelerated by dosage of acetate. The Modified Renphosystem is characterized by distribution of the stripped sludge to the first aerobic zone and the anoxic zone. In the aerobic nitrification and P-accumulation take place. In the anoxic zone denitrification and P-accumulation run simultaneously. The experiments carried out at low F/M-ratios resulted in very low concentrations of P and N in the effluent. For achieving a high degree of nitrate removal the first part of the mainstream of the Modified Renphosystem was retrofitted to a AAO-system followed by an anoxic and aerobic zone respectively. This process configuration resulted in Pt and Nt of the unfiltered effluent of 0.4 and 2 mg/l respectively.
Limits of sludge dewaterability
Authors: Vesilind P. Aarne , Hsu Cheng-Chao
Published: May 2018

Water in sludge appears to be of four kinds; free water which freezes at normal freezing temperatures; interstitial water, which freezes at lower temperature due to high dissolved solids concentrations; vicinal water which is associated with solid surfaces and freezes only at very low temperatures; and water of hydration, which does not enter the ice crystal and which can be removed from the sludge only by thermal means. Using the classical technique of freezing in dilatometers, unfrozen water is measured in sludge at different temperatures and at different solids concentrations. Not all water appears to be frozen even down to −30°C. At low solids concentrations, where the sludge does not form large flocs, the only unfrozen water is most likely vicinal water and the water of hydration. At intermediate solids concentrations, the flocs capture the interstitial water which does not freeze, apparently due to its high dissolved solids concentration. At high solids concentrations, the interstitial water is squeezed out of the flocs and only the vicinal water and the water of hydration remain unfrozen. It is not possible to remove vicinal water or the water of hydration by mechanical means, but it is theoretically possible to remove the interstitial and free water. A knowledge of these fractions of water can provide practical limits of mechanical dewatering.
Investigation into alternative sludge conditioning prior to dewatering
Authors: Smollen Maryla , Kafaar Achmad
Published: May 2018

The principal objective of this work is to provide a more effective alternative for sludge conditioning prior to mechanical dewatering. The common use of polyelectrolytes often results in the final cake solids concentration not sufficiently high for the sludge to be beneficially reused or safely disposed. The pyrolysed domestic refuse (char) was used to increase the structural strength and permeability of biological sludges in order to increase final cake solids concentration. The laboratory experiments have proven that the mixture of char and a small quantity of polyelectrolyte (0.5 to 1kg per ton of dry solids), used as a conditioner prior to centrifugation and filtration tests, produced cake solids concentration superior to that obtained by using polyelectrolyte on its own. Laboratory dewatering by filtration with admixture of char and polymer, resulted in cake solids concentration of 30 and above 40 per cent.
Thermal inactivation of plant seeds in sewage sludge
Authors: Baier Urs
Published: May 2018

Seeds of Tomato (Lycopersicon lycopersicum) and Millet (Digitaria sanguinalis) were exposed to temperatures from 60°C to 70°C for 20 to 75 minutes. The influence of aeration as well as heat protection by sludge solids was investigated in laboratory scale and in full scale sludge hygienisation.

Thermal inactivation of Millet was achieved at temperatures of 65°C where 1 - 5% of the seeds survived an exposure of 60 minutes. Lower temperatures showed little effect on Millet. At 60°C only 1 - 10% inactivation was found after 70 minutes. Complete inactivation could be achieved at 70°C and above with exposition periods of 20 minutes.

Tomato seeds showed a higher resistance to heat inactivation at low temperatures. Temperatures of 60 - 65°C were not sufficient to inactivate the seeds. An exposition of tomato seeds to 65°C for 60 minutes still resulted in a survival of > 20% of the initial seed concentration. Complete inactivation was found at 70°C and higher with exposition periods of 20 minutes.

No difference of heat inactivation was found between static and aerated sludge. The protective action of sludge solids was found to be present but negligible for both species.

Today's sludge hygienisation technology will significantly reduce Millet and Tomato seeds in sludge and eliminate or reduce the risk of contamination of agricultural areas. Thermal pasteurisation processes show a higher seed destruction potential for Tomato and Millet than aerobic - thermophilic pretreatment.
A design model of sewage sludge incineration plants with energy recovery
Authors: Mininni G. , Zuccarello R. Di Bartolo , Lotito V. , Spinosa L. , Di Pinto A. C.
Published: May 2018

A design model of sewage sludge incineration plants has been developed to examine the possibilities for energy recovery. It was evident that, without sludge drying, there was a high fuel (methane) consumptions (149-192 Nm3/t sludge cake at 25% concentrations), but considerable amount of electric energy is obtainable (391-515 kWh/t sludge cake). Sizes of boiler and whole exhaust gases treatment line are in this case quite large. On the contrary, fuel consumption can be lowered down to 20 Nm3/t sludge cake at 44% concentration by introducing sludge drying. In this case fuel is needed only in the afterburning chamber, as the combustion in the fluidized bed furnace is autothermal. Boiler and exhaust gas treatment line are considerably reduced in size when power production is not performed, thus allowing a simpler and smaller plant to be designed.
Lab-scale evaluations on formation of products of incomplete combustion in hazardous waste incineration: influence of process variables
Authors: Mascolo G. , Spinosa L. , Lotito V. , Mininni G. , Bagnuolo G.
Published: May 2018

Laboratory investigations have been carried out to study the influence of process failure modes on organics emission during the incineration of hazardous sludge. The thermal, temporal and fuel-oxidant mixing failure modes were tested. They were simulated by holding the first combustion temperature at 400°C and varying the after-burning one between 600 and 1100°C, the after-burning residence time between 1 and 3 s and the excess air between 30 and 160%. Results showed that the thermal failure mode is the most important factor controlling the number and concentration of emitted organics leading to the formation of over 70 compounds at after-burning temperature of 600°C. At higher after-burning temperatures emissions are controlled by the fuel-oxidant mixing failure mode and, only when the after-burning is 800°C and the oxygen is 160% over the stoichiometric value, by the temporal failure mode. Based on results obtained some suggestions for reducing emissions of toxic organics in full-scale incinerators are given.
Role of plant uptake on nitrogen removal in constructed wetlands located in the tropics
Authors: Koottatep Thammarat , Polprasert Chongrak
Published: May 2018

Major interactive components of the constructed wetlands such as aquatic vegetation, substratum, water, microorganisms and animals play significant roles in the treatment of wastewaters. For nitrogen (N) removal, a sequential nitrification/denitrification reaction and plant uptake are two major treatment mechanisms, while NH3 volatilization is considered to be insignificant under the liquid pH lower than 8. In this research, both laboratory- and pilot-scale constructed wetlands were operated in the free water surface (FWS) mode. In order to investigate the role of plant uptake of N, narrow-leave cattails (Typha augustifolia) were planted at the initial density of 35 rhizomes/m2. Based on N mass balance, approximately 50% of the total nitrogen (TN) loaded into the constructed wetlands, operating at the hydraulic retention time (HRT) of 2–10 days, was accounted for by the amount of N assimilation into the plant tissues, resulting in the total kjeldahl nitrogen (TKN) and chemical oxygen demand (COD) removal efficiencies of 40–70% and 71–83%, respectively. To further investigate the role of plant uptake, the cattail plants harvested at the intervals of 2, 4, 8, and 12 weeks of operation resulted in the TN removal efficiencies of 73, 78, 86 and 80%, respectively. The constructed wetland unit having the plant harvesting interval of 8 weeks yielded the N plant uptake of 7.1–7.5 kg/(ha.day) amounting to 66–71% of the TN input. Some biogeochemical parameters such as oxidation-reduction potential (Eh) and dissolved oxygen (DO) in the constructed wetland beds suggested the occurrence of anoxic and reduced conditions which were favorable for the N removal processes such as plant uptake, ammonification, and nitrification/denitrification.
Polishing of BNR process effluent by tertiary denitrifying filter
Authors: Zuwhan Yun , Euiso Choi , Han Young T.
Published: May 2018

The objective of this research is focused to evaluate the effectiveness of a denitrifying filter system for the tertiary effluent polishing process. Operational results from the laboratory-scale denitrifying filter using sand media of 90 cm depth showed that a successful application largely depended on the design of filtration rate, amount of external carbon source supplied, and bumping operation. A deterioration of SS quality in the final effluent was caused by the reduced empty bed detention time (EBDT) due to the increase of filtration rate. Up to 96% of NO3-N removal efficiency was consistently achieved by the addition of methanol as a carbon source and with EBDT of less than 18 minutes. It is noticed that the production of low SS effluent from the denitrifying filter largely depended on the bumping operation. The frequent bumping operation was a major source of SS washout from the filter. The negative effect of the bumping operation in the single-stage filter was minimized by the design of the shallow bed 2-stage filter system. Although the denitrification rate at 10°C was reduced to 4.8 mg NO3-Nremoved/grVSS/hr, a practical level of nitrate removal would be achieved by appropriate design.
Biological denitrification of high explosives processing wastewaters
Authors: Zoh Kyung-Duk , Stenstrom Michael K.
Published: May 2018

Previous work in our laboratory over the past four years has shown that the high explosives hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) can be readily destroyed by alkaline hydrolysis. The hydrolysis process produces large quantities of concentrated but conventional wastewaters, containing acetate, formaldehyde, formate, ammonia and nitrite. To treat these wastewaters, a denitrifying (anoxic) biological process was developed that converts the hydrolysates to harmless endproducts, such as N2 and CO2. The nitrite is produced during the hydrolysis process as the electron acceptor, but additional nitrite is required to completely oxidize the carbon compounds. Over 90 percent of each organic carbon source can be removed in a packed-bed, upflow reactor in 3 hours hydraulic retention time. Formaldehyde and acetate are first degraded at approximately the same rate, and formate is degraded more slowly. Results closely match the stoichiometry predicted by the empirical redox equations describing the process.
Phosphorus removal from nightsoil with sequencing batch reactor (SBR)
Authors: Oa S. W. , Choi E.
Published: May 2018

Phosphorus removal characteristics are rather complicated in a highly nitrogenous waste like nightsoil under treatment with SBR (sequencing batch reactor). It was found that the increased pH due to denitrification in anaerobic period stimulated chemical precipitation of phosphorus as struvite and hydroxyapatite, and the depressed pH due to nitrification in the aerobic period dissolved the previously formed precipitates. Phosphate accumulating organisms (PAO) worked as in the ordinary BNR (biological nutrient removal) systems regardless of the chemical reactions, but the chemical reactions masked the biological phosphorus release and uptake reactions. About 36% of phosphorus applied was removed biologically in polyphosphate granules. P-fractionation of sludges confirmed this phenomenon. Biological phosphorus removal could be increased with the increased anaerobic period. The morphological types of phosphorus precipitates were examined by SEM in combination with x-ray diffraction.
Operating characteristics of aerated submerged biofilm reactors for drinking water treatment
Authors: Lim Kyeong-Ho , Shin Hang-Sik
Published: May 2018

As the quality of raw water deteriorates, a number of additional treatment techniques have been developed and adapted to water treatment for producing a safe and aesthetically satisfactory drinking water. One of the various alternatives is to use a biological process, such as a submerged bed filter, as the first process in the treatment train followed by conventional treatment processes. Biofilm process for the pretreatment of water is suitable for advanced treatment as the biofilm can keep microorganism, at low organic concentrations. This article examines the application of biological treatment strategies to tackle the current problems of the water industry. Pilot-scale biofilm reactors were evaluated with various contaminants frequently encountered in water supplies. The studies focused on the production of biologically stable water, increased disinfectant stability, and reduced formation of disinfection by-products. Results showed that the finished water became more biologically stable even though the reduction of organics was relatively low. Biofilm grown on natural water supplies was effective in removing THMP (trihalomethane precursor) as well as taste and odour compounds, such as geosmin.
Control of sulfate reduction by molybdate in anaerobic digestion
Authors: Tanaka Shuzo , Lee Young-Ho
Published: May 2018

Control of sulfate reduction by adding molybdate was investigated to enhance the methane production under batch and continuous operation in the anaerobic digestion of a sulfate-rich lysine wastewater. In phase 1 of the continuous operation, four anaerobic filters were fed with the lysine wastewater and then added with molybdate at 1,3,5 and 10 mM just after methane producing bacteria (MPB) were completely inhited by H2S produced by sulfate reducing bacteria (SRB). In phase 2, three anaerobic filters were operated with continuous or intermittent addition of 3 mM molybdate from the beginning of operation, including one with no molybdate as a control. Batch experiments revealed that the sulfate reduction was strongly inhibited and finally ceased by adding 3 mM or more of molybdate, resulting in great enhancement of the methane production. In phase 1 of the continuous experiments, all reactors showed the cessation of the methane production when the content of H2S reached 9–10 % in biogas, but the MPB activity was gradually recovered after initiating the molybdate addition at 3 or 5 mM. The 10 mM dosage of molybdate, however, had an inhibiting effect to MPB as well as SRB, resulting in the accumulation of acetate within the reactor. In phase 2, the control reactor continued to decrease the methane production, and a methane conversion rate was only 3 % in the control, while 35 and 10 % in continuously-added and intermittently-added reactors, respectively. Thus, it was confirmed that the MPB activity was greatly enhanced under control of the SRB activity by the continuous addition of molybdate. Comparing phase 2 with phase 1, addition from the start-up of the process is considered more effective than addition after the methane production dropped in the control of the sulfate reduction by molybdate.
Water quality and occurrences of protozoa and metazoa in two constructed wetlands treating different wastewaters in Thailand
Authors: Panswad Thongchai , Chavalparit Orathai
Published: May 2018

Two constructed wetlands were evaluated regarding their performance in treating different wastewaters under the tropical conditions of Thailand. The first one was for treating the domestic sewage from a governmental institute, whereas the latter was used to improve the quality of the effluent from a central aerated lagoon, for which the influent had been already pretreated by about 100 factories in an industrial estate. The hydraulic loading rate and the hydraulic retention time were 0.015 m3/m2.d and 28 days and 0.3 m3/m2.d and 3 days for the two wetland systems, respectively. The physical and chemical water quality and the occurrences of protozoa and metazoa were monitored for three seasons, each of which had samples taken twice a week for two months. The temperature was quite constant throughout the whole year, ie., 26 to 31°C and 25 to 34°C for the two wetlands, respectively. The water quality of the wetland effluents was rather good; the BOD and TKN were only 4.5 and 3.3 mg/l and 2.7 and 6.8 mg/l for the two cases. A relationship between the filtered BOD and the zoological characteristics was established. As a result, a simple glance at the occurrence of certain metazoa and protozoa can rapidly but approximately predict the water quality of the system.
A novel and cost-effective sewage treatment system consisting of UASB pre-treatment and aerobic post-treatment units for developing countries
Authors: Machdar Izarul , Harada Hideki , Ohashi Akiyoshi , Sekiguchi Yuji , Okui Hiroyuki , Ueki Kyoko
Published: May 2018

A novel sewage treatment system was proposed, which consists of a UASB anaerobic pre-treatment unit and the following DHS (downflow hanging sponge-cubes) aerobic post-treatment unit, as a low-cost and easy-maintenance process for developing countries. Over six months experiment by feeding sewage our proposed system achieved 94% of total-COD removal, 81% of soluble-COD removal, and nearly perfect SS removal and total-BOD removal at the overall HRT of 8.3 hr (7 hr in UASB and 1.3 hr in DHS unit). Moreover, the DHS reactor was capable of performing high (73–78%) nitrification. Our whole system requires neither external aeration input nor withdrawal of excess sludge.
Micropollutant removal with saturated biological activated carbon (BAC) in ozonation–BAC process
Authors: Woo Hang Kim , Nishijima Wataru , Baes Aloysius U. , Okada Mitsumasa
Published: May 2018

The objective of this study is to evaluate the adsorption capacity of BAC saturated with natural organic matter (NOM) for micropollutant removal which intermittently enter into water sources and to compare this to sand filtration that has no adsorbability but has biodegradability.

The removal of intermittently applied micropollutants was examined with two BAC and sand filters. Two BAC filters which have been operated for 6 and 20 months and a sand filter being used for 6 months for the treatment of reservoir water were used in this experiment. EBCT of these BAC and sand filter were 15 minutes. Bromophenol (highly adsorbable but refractory) and phenol (adsorbable and biodegradable) were used instead of targeted micropollutants. Bromophenol and phenol of about 200 μg·l−1 were applied for 24 hours.

The BAC 1, which was used for 20 months had already lost its adsorbability because it was saturated with NOM. BAC 2 filter which was used for 6 months had small adsorption capacity for NOM. As a result, either BAC 2 or BAC 1 removed bromophenol (160 μg·l−1) completely for 24 hours spike, but sand filter did not removed at all. Bromophenol can be removed only by adsorption, therefore bromophenol might be removed through adsorption by BAC. On the other hand, phenol (220 μg·l−1) whose adsorbability is lower than bromophenol, was removed completely by both BAC 1 and BAC 2.

These results indicate that micropollutants with similar adsorbability as that of phenol and bromophenol can be removed by BAC even after a long period of operation and saturation with NOM.
Risk assessment and management of drinking water pollutants in Korea
Authors: Yong Chung , Dongchun Shin , Seongeun Park , Yeongwook Lim , Yoonho Choi , Seongjoon Cho , Jeeyeon Yang , Mansik Hwang , Yeosin Park , Hyun Lee
Published: May 2018

The contamination of drinking water supply is becoming an increasingly serious problem in Korea. In order to protect public health, there is a need to regulate drinking water pollutants. The purpose of this project, a national project for three years starting from 1992 to 1995, is to assess the health risk of pollutants in drinking water and recommend guidelines and management plans for maintaining good quality of drinking water. This study was conducted to monitor 80 species of chemicals including volatile organic compounds(VOCs), polycyclic aromatic hydrocarbons(PAHs), pesticides and metals in six major rivers and their distribution system for drinking water in Korea, and evaluate health risk due to exposure to these chemicals through four main steps of risk assessment in drinking water. In hazard identification, 80 species of chemicals were identified by the US EPA classification system. In their steps of exposure assessment, sampling of raw, treated and drinking water from the public water supply system have been conducted from 1993 to 1995, and 80 chemicals were analyzed. In dose-response assessment, cancer potencies, unit risk estimates and virtual safety doses of carcinogens were obtained by TOX-RISK, and reference doses and lifetime health advisories of noncarcinogens were calculated. Finally, in the risk characterization of detected chemicals, health risk due to exposure to carcinogens (weight of evidence, A or B) such as vinyl chloride, carbon tetrachloride, 1,2-dichloroethane, benzen, 1,1,1,2-tetrachloroethane, trihalomethanes(THMs), lead and arsenic of tap water in several cities exceeded 10−5 level. We suggest that non-regulated chemicals such as vinyl chloride, carbon tetrachloride and 1,2-dichloroethane should be monitored periodically and be regulated by the Drinking Water Management Act.
Management of toxicity effects in a large wastewater treatment plant
Authors: Grau P. , Da-Rin B. P.
Published: May 2018

An unusually severe case of toxicity accompanied by activated sludge filamentous bulking was observed at the wastewater treatment plant Sao Paulo-Barueri. Treatment efficiency of the plant, operated without major problems for more than five years before, was significantly hindered for almost six months. Occurrence of toxic shocks was confirmed partly directly but mostly indirectly by inhibition of nitrification and biological phenomena related to toxicity. Several measures adopted, including the recycled activated sludge chlorination, are described in the paper.