bluuebunny/crossref_metadata_2025 huggingface dataset:
Aqueous microorganisms inactivation by photocatalytic reaction
Authors: Otaki M. , Hirata T. , Ohgaki S.
Published: May 2018

Photocatalysis by TiO2 is a new technology which can treat water without adding any chemicals. In this research, the disinfections of three microorganisms such as bacteriophage Qβ, E. coli and Cryptosporidium parvum were investigated. An immobilized TiO2 reactor was used and UV lamp and Black light (BL) lamp were used as light source. The intensity of each lamp was set up to equalize the photocatalysis efficiency determined by the decomposition rate of Methylene Blue. The additive effect of TiO2 to inactivation did not appear in the E. coli experiments with UV and BL irradiation or in the Qβ experiment with UV. In these three cases, light irradiation gave a high germicidal effect and the addition of inactivation by photocatalysis was relatively too small to be significant. In the Qβ experiment with BL and in the Cryptosporidium experiment with UV and BL, the additive effect by TiO2 could be seen clearly because these microorganisms were resistant to light irradiation in these cases. In spite of setting equal photocatalysis efficiency in both lamp reactors, UV photocatalytic inactivation of Cryptosporidium was much faster than BL. It is assumed that UV and photocatalysis enhanced each other.
Characterization of the microbial diversity in a biotreatment process using non-culture based methods
Authors: You S.J. , Ouyang C.F. , Lin S.F. , Liu W.T.
Published: May 2018

Molecular techniques were used to compare the microbial community of suspended activated sludge and attached biofilm in a biological nutrient removal process (TNCU-I) operated under various COD/total P (COD/TP) feed ratios. Analysis of restriction fragment length polymorphism of amplified 16S rRNA genes indicated that the microbial population structures were more closely related among those sludge samples taken from aerobic sludge than that taken from biofilm attached on the RBC. The use of different COD/TP feed ratios (300/2.5-300/25) had no significant effect on the change of microbial structures of sludge samples. The 16S rDNA clone library further indicated that at least eight and six different microbial populations were present in activated sludge and RBC biofilm, respectively. The phylogenetic analysis revealed that six of those eight major clones obtained from the suspended activated sludge were from the beta-subclass of the class Proteobacteria. In contrast, only one clone obtained from biofilm belonged to the beta-subclass of the Proteobacteria. This difference in the microbial population structure was possibly attributed to the growth state (suspended or attached) or carbon source (autographs or heterotrophs) of the sludge samples rather than the effect of the COD/TP ratio used.
Nitrate removal by an ultra-compact biofilm reactor
Authors: Ong S.L. , Ng W.J. , Lee L.Y. , Yu J. , Hu J. Y.
Published: May 2018

This study consisted of two stages. The first stage was to cultivate denitrifying biofilm with a simplified UCBR while the second stage was to investigate the performance of a standard UCBR for nitrate removal. The volumetric nitrate-N conversion rate increased steadily from less than 0.5 kg/m3.d to about 2.5 kg/m3.d towards the end of Stage 1. Reactor instability and poor biofilm morphology had led to a relatively low nitrate-N conversion rate during stage 1 of operation. In Stage 2, the conversion rate increased rapidly to 6.5 kg/m3.d within 4 days and increased steadily to 10.5 kg/m3.d, thereafter. The biofilm formation in Stage 2 was better than that attained in Stage 1. Biofilm density and biomass concentration in the reactor were in the range of 20.5 to 29.0 g/L and 1 to 3 g/L, respectively. The specific growth rate of the denitrifiers (μ) and the observed biomass growth yield coefficient (Yobs) in the reactor varied within the ranges of 1.5-4.2 d-1 and 0.20-0.65 g biomass/g nitrate-N, respectively. The specific nitrate-N conversion rate (γ) was within the range of 1.8-3.8 g nitrate-N/g biomass.d.
A pilot study on nitrogen and phosphorus removal by a modified photostrip process
Authors: Kim K.-S. , Cho K.-M. , Choi H. , Kim I.S.
Published: May 2018

A pilot plant with a capacity of 20∼30m3/day was operated for 10 months for simultaneous removal of nitrogen and phosphorus by a modified Phostrip process. In the process, a denitrification tank was installed before the aeration tank in the Phostrip process, which was developed mainly for phosphorus removal. To maintain the effluent TKN concentration in the range of 1∼3 mg/L, the allowable maximum TKN loading rate in the aeration tank was found to be 0.065 kg TKN/kg MLSS·d. The nitrification rate in the aeration tank increased as the influent COD/TKN ratio declined. The optimal internal recycle rate from the aeration tank to the denitrifier was found to be 2Q when the yearly average COD and TKN concentration of the influent was 197 mg/L and 37.1 mg/L, respectively. To keep the effluent T-P concentration below 1 mg/L, T-P loading to the aeration tank should be less than 0.008 kg T-P/kg MLSS·d at the sludge recycle rate of 0.3Q from the 2nd clarifier to P-stripper. However, the loading should be kept at less than 0.0065 kg T-P/kg MLSS·d at the sludge recycle rate of 0.15Q.
Predator grazing effect on bacterial size distribution and floc size variation in membrane-separation activated sludge
Authors: Luxmy B.S. , Nakajima F. , Yamamoto K.
Published: May 2018

In this study the role of higher organisms and the effect of their predation on bacterial size distribution as well as on floc size variation were investigated in the membrane-separation activated sludge system. The pilot plant study was conducted by setting a membrane-separation bioreactor (MBR) in a wastewater treatment plant in Tokyo, Japan. A large number of predator organisms were observed in the MBR dominated by ciliated protozoa. The dispersed bacterial size distribution was obtained by using the combination of florescent in situ hybridization (FISH) and image analysis technique. With the increase of predator species especially sessile ciliates and free-swimming ciliates, reduction of smaller bacterial population (1 μm or so) was significant. It was found that, bacteria and predators are negatively correlated i.e. with increasing number of predator organisms the number of dispersed bacteria decreased. This effect of predation was confirmed while observing the floc size distribution with an automatic particle distribution measuring instrument simultaneously. It was observed that when the higher predator organisms (protozoa and metazoa) were high in number, the percentage of floc groups less than 10 μm (optimum prey size for most of the ciliate species) were less and vice versa. From this study it can be concluded that, mainly the smaller flocs which mostly consist of small (<1 μm) dispersed bacterial species, were grazed heavily by the predator population in the membrane-separation activated sludge.
Alkalinity requirements and the possibility of simultaneous heterotrophic denitrification during sulfur-utilizing autotrophic denitrification
Authors: Kim E.-W. , Bae J.-H.
Published: May 2018

Alkalinity requirement and the possibility of simultaneous heterotrophic denitrification during sulfur-utilizing autotrophic denitrification were evaluated with sulfur packed bed reactors (SPBRs). SPBR showed >99% NO3--N removal efficiency at influent NO3--N concentration of 1,500 mg/L, although 25-40% of the added NO3--N was recovered as N2O. Complete denitrification without N2O production was achieved when the influent NO3--N concentration decreased to 750 mg/L. When nitrified landfill leachate containing 602–687 mg/L of NO3--N was fed to SPBR, denitrification efficiency was greater than 98%. During leachate treatment, alkalinity consumption was 3.25–3.76 g CaCO3/g NO3--N removed. Most of denitrification activity occurred within bottom 11.5 cm of sulfur layer, meaning that effective HRT of 2.34 hours was enough for the complete denitrification at the loading rate of 2.2 kg NO3--N/m3-day. Complete denitrification was also achieved when methanol was added to nitrified leachate without alkalinity addition. In this case, alkalinity produced by heterotrophs was used for sulfur-utilizing denitrification.
Effect of chemical structures of reactive dyes on color removal by an anaerobic-aerobic process
Authors: Luangdilok W. , Panswad T.
Published: May 2018

An Anaerobic/Aerobic SBR system was used to treat a synthetic wastewater with glucose and acetic acid (1000 mg/l COD) as carbon sources together with 20 and 100 mg/l of four different reactive dyes: disazo vinylsulphonyl, anthraquinone vinylsulphonyl, anthraquinone monochlorotriazinyle and oxazine. The decolorization efficiencies of the first three dyes at the 20 mg/l dye concentration were 63, 64 and 66%, respectively, and at the 100 mg/l dye concentration were 58, 32 and 41%, respectively. For the disazo dye, two color removal rates were evident, with the initial rate in the first two hours of the anaerobic stage higher than the latter. For the two anthraquinone dyes, only one rate of color removal was seen. For the oxazine dye, a high decolorization was observed in the reactor, but when disturbed, the color re-appeared for unexplainable reasons. The phosphorus removal efficiencies were 78, 52, 41 and 96% for the four dyes of 20 mg/l, respectively, while the corresponding numbers for the 100 mg/lcondition were 48, 48, 48 and 42%, respectively, and different types of dyes had different impacts on the phosphorus removal performance. COD and TKN removals were very high, i.e., 90–99 percent. The disazo reactive dye was decolorized by the reductive reaction, which resulted in the cleavage of the azo bond. Meanwhile, the decolorization of anthraquinone dyes is believed to be through the direct adsorption of dyes on to the floc materials.
Modeling and simulation with microsites on vertical concentration profiles in sediments of aquatic zones
Authors: Sakita S. , Kusuda T.
Published: May 2018

Modeling of reactions in sediments with microsites which have particulate organic matter (POM) in their cores as energy source for bacteria (called the M-S model) and subsequent simulation using it are executed for the explanation of vertical concentration profiles in sediment, and for the comparison with a conventional vertically one-dimensional transport-reaction model (the V-1 model). The POMs in the sediment are assumed to be sphereical with a range from 50μm to 500μm in radius and a logarithmic normal distribution.

The POM size and distribution alter the concentration profiles in the sediment in the M-S model, especially NO3--N profiles, because of dependence of denitrification rate on the POM characteristics. Anoxic and anaerobic reaction rates in the sediment in the V-1 model are underestimated because of no microsite. For the practical purpose of calculating concentration profiles of substances, the M-S model has higher accuracy and controlability, and is useful for detailed explanation of reactions in the sediment.
Quantification of foaming behaviour using foam index
Authors: Ng W.J. , Ong S.L. , Sarada N. , Hu J.Y. , Fan X.J. , Ang W.S.
Published: May 2018

The factors influencing foam index were identified and their effects on foam index were investigated. It was noted that increasing the diameter of the flotation cell led to an increase in foam index. The maximum foam index was found to occur at a constant air/solids ratio when MLSS was varied with time of aeration or airflow. A good degree of correlation was also obtained between filament count and foam index. A small concentration of Surfactants was sufficient to induce foaming. However, further increase in surfactants showed relatively little influence on Foam Index.
Full scale case studies of a simplified aerated filter (BAF) for organics and nitrogen removal
Authors: Chen J.J. , McCarty D. , Slack D. , Rundle H.
Published: May 2018

The limitation of available land for wastewater treatment facilities has challenged environmental engineers in searching for efficient and effective treatment systems that will minimize space requirements for waste treatment. To meet these requirements, a fixed film biological process using a DeepBedTM filter for aerobic and anoxic treatment was developed. The innovative biotechnology uses sand as the media to which microorganisms attach and as the filter media for solids retention. The unique characteristics of the biosystem combine long sludge age and short hydraulic detention time and provide small footprints for the bioreactor. The novel technology has been successfully practiced for industrial and municipal wastewater treatment in three (3) continents. This article gives details of a US facility to treat coke plant effluent with high ammonia and phenol content, describes a plant in Taiwan for polishing plastic manufacturing wastewater by combining ozone and biofiltration, illustrates nitrogen removal from a semiconductor factory in Korea, and shows the results of a municipal treatment plant in Britain using BAF to pretreat peak loads from the dairy industry.
Nutrient balances for combined nitrification and denitrification in biofilters
Authors: Zwerger B. , Arnold E. , Wilderer P.A.
Published: May 2018

Nutrient balances were set up for a biofiltration pilot plant operated with pre-denitrification and post-nitrification in order to gain more information about its treatment efficiency. Data collected during several weeks was used for balancing the parameters phosphorus (Ptot), carbon (COD) and nitrogen (Ntot). From the results obtained (overall deviation of 20–30%) it can be stated that 30% of the phosphorus load in the inlet was incorporated into biomass or sludge. The effluent contained between 50 and 80% of the incoming phosphorus loading. The percentage of the initial carbon loading found by sludge analysis was in the range of 60 to 80% and about 20% were measured in the effluent. Thus, only 20 to 40% were oxidized and/or utilized as carbon source for denitrification. The nitrogen balance showed similar values for incorportion as determined for phosphorus (20–40%). As not more than 20% of the incoming nitrogen load could be denitrified, 40–60% left the plant with the effluent.
Numerical simulation of the flow field in a bioreactor
Authors: Ester S. , Guo X. , Delgado A.
Published: May 2018

In order to give detailed information about the local flow field in a bioreactor a numerical method has been developed. This method gives information about the velocity, pressure and temperature in each point of the reactor, avoiding the problems caused by placing measurement instruments inside. Comparisons of experiments and numerical results show good agreement. The functionality and physical fundamentals of this tool are described. This is followed by explaining a reasonable application of the numerical code in the field of biological reactors. The reactors considered are filled with polydisperse, spherical support particles. From the results of the simulation a detailed picture of a reactor's fluid mechanical behaviour is drawn. This includes the quantification of mechanical stresses on the biofilm surface as well as information about the inflow, outflow and channelling behaviour of a reactor. Furthermore the effect of polydisperse support carries in discussed.
Anaerobic treatment of low concentration waste water in an inverse fluidized bed reactor
Authors: Castilla P. , Meraz M. , Monroy O. , Noyola A.
Published: May 2018

Low concentration synthetic and municipal wastewaters were treated at HRT as short as 3 and 0.6 h respectively in an anaerobic inverse fluidized bed. Both bioreactors showed gas hold up due to the liquid downflow pattern of the prototype. The bioreactor operated at 3 h had a removal efficiency of 83%, specific activity of 4.5 kg CODremoved/kg IVS (d and the gas hold up varied from 23 to 55%. The reactor treating municipal wastewater had a removal efficiency of 44% when operating at 0.6 h, the specific activity was 4.2 kg CODremoved/kg IVS (d and no biogas was detected apparently because an important fraction was dissolved in the liquid phase. The biomass concentration was 13.8 and 1.1 kg IVS/m3 for synthetic and municipal wastewater and the SEM microphotographs showed a bacterial diversity for the first run and only cocci cells for the second run. The system does not remove suspended solids, so a polishing postreatment to improve water quality has to be implemented.
Relations between carbon removal rates, biofilm size and density of a novel anaerobic reactor: the inverse turbulent bed
Authors: Buffière P. , Moletta R.
Published: May 2018

An anaerobic inverse turbulent bed, in which the biogas only ensures fluidisation of floating carrier particles, was investigated for carbon removal kinetics and for biofilm growth and detachment. The range of operation of the reactor was kept within 5 and 30 kgCOD· m−3· d−1, with Hydraulic Retention Times between 0.28 and 1 day. The carbon removal efficiency remained between 70 and 85%. Biofilm size were rather low (between 5 and 30 μm) while biofilm density reached very high values (over 80 kgVS· m−3). The biofilm size and density varied with increasing carbon removal rates with opposite trends; as biofilm size increases, its density decreases. On the one hand, biomass activity within the reactor was kept at a high level, (between 0.23 and 0.75 kgTOC· kgVS· d−1, i.e. between 0.6 and 1.85 kgCOD·kgVS · d−1).This result indicates that high turbulence and shear may favour growth of thin, dense and active biofilms. It is thus an interesting tool for biomass control. On the other hand, volatile solid detachment increases quasi linearly with carbon removal rate and the total amount of solid in the reactor levels off at high OLR. This means that detachment could be a limit of the process at higher organic loading rates.
Operational results and experience with submerged fixed-film reactors in the pretreatment of industrial effluents
Authors: Schlegel S. , Teichgräber B.
Published: May 2018

Submerged fixed-film reactors are ideal for the pretreatment of industrial effluents. The advantages lie not only in the investment costs, but also in the operating costs. The pretreatment plants can be subject to higher loads than are possible with the activated sludge process. Consequently, considerably less space is required. And, last but not least, it is also possible to treat normally non-degradable industrial effluents. The prerequisites are that system-related general structural requirements are fulfilled and suitable materials are used for the fixed-film reactor.

They also offer considerable advantages in terms of operation compared to the activated sludge process, since both a higher oxygen transfer rate and yield are achieved, less sludge is produced and fewer personnel are required. All in all, the upstream submerged fixed-film reactor has proven to be an extremely reliable process, requiring little maintenance, that can cope, to a far-reaching degree, with load fluctuations of all types and reduce these. As a result, the operation of downstream treatment stages is also stabilized.
Improvement of river water quality - the results of industrial effluent minimisation
Authors: Zagorc-Končan J. , Žgajnar Gotvajn A.
Published: May 2018

The harmful effects of wastewaters on receiving streams, caused by insufficient quality of effluents, inadequate dimensioning and overloading of present treatment plants, as well as the trends of science and technology call for improvement of the treatment technologies, development of advanced treatment processes and above all for waste minimisation in industrial processes to meet the increasing water quality standards. Microbial degradation is crucial in the prediction of the duration and, thereby, the effects of organic pollution in natural waters. Evaluating the fate of biodegradable organic pollution downstream from the discharge seems an appropriate way to follow the effect of pollution and its hazard assessment that dictates needed sanitation measures. This paper is concerned with effluent discharges and with the water receiving such discharges. A practical method for the study of the fate of biodegradable industrial pollution in receiving stream is demonstrated. The impact of wastewater from the synthetic phenol-formaldehyde resin production on Borovnišica river is presented. By comparative investigations, before and after introduction of sanitation measures, the beneficial impact of industrial effluent minimisation and treatment is shown evidently.
The recovery of precious metals from acidic effluents using sodium formate
Authors: Julsing H.G. , McCrindle R.I.
Published: May 2018

At Western Platinum Refinery in South Africa, zinc was used for the reduction of the platinum group metals (PGMs) in acidic effluent (palladium filtrate). Owing to the increasing cost of zinc and the risk of zinc pollution, sodium formate was investigated as an alternative reductant. It was found that pH 1.5 was the optimum starting pH for sodium formate reduction. The optimum concentration of sodium formate was found to be 18 g/dm3 at a temperature of approximately 100°C where the process time was 5 hours. The addition of sodium formate increased the pH of the final reaction mixture to approximately pH 4.5. Palladium was the most effectively reduced PGM, exhibiting an average precipitation efficiency of 98%. Difficulty was experienced with the precipitation of platinum (average precipitation efficiency of 47%). The precipitated PGMs were readily dissolved in hydrochloric acid (6 M) and sodium chlorate (2%). A reduction in costs resulted from the discontinuation of the use of zinc for reduction purposes. An additional advantage was that zinc was no longer introduced into the PGM refinery circuits. This effectively reduced the pollution potential of the acidic effluent.
Comparative study on polyvinyl alcohol and alginate for cell immobilization in biosorption
Authors: Ting Y.P. , Sun G.
Published: May 2018

In this work, we compared the performance of a new method of cell immobilization in a novel matrix for biosorption. Yeast cells were entrapped in a polyvinyl alcohol (PVA) matrix, based on an adapted iterative freeze-thaw-freeze process. Spherical and uniform beads were produced, and SEM micrographs confirmed that the cells were uniformly dispersed within the PVA matrix. Further experiments revealed that the use of PVA as the immobilization matrix conferred better mechanical and chemical properties than the commonly used calcium alginate matrix. Experiments also showed that the PVA matrix gave rise to a lower mass transfer resistance than the alginate matrix. Finally, it was established that PVA-yeast biosorbent beads could be regenerated using dilute hydrochloric acid (10mM) and reused for at least five biosorption cycles with virtually no decrease in its bisorption capacity. Different metal/biosorbent in PVA-immobilized systems are currently being investigated.
Photocatalytic degradation of wastewater from manufactured fiber by titanium dioxide suspensions in aqueous solution: a feasibility study
Authors: Hsieh Y.H. , Wang K.H. , Ko R.C. , Chang C.Y.
Published: May 2018

This investigation used wastewater from manufactured fiber plant for studying the effect of controlling variables on the COD removal efficiency by photocatalyzed degradation of organic pollutants in the presence of titanium dioxide catalyst. By using BOD/COD ratio as index, the treatment of raw wastewater was evaluated for its change of biodegradability as a feasibility in the pre-treatment of biological treatment. The experimental results indicated that with the Janssen Chemica TiO2 as catalyst, the optimal addition was 0.25 g/L with increasing COD removal for decreasing pH value. Both increased light intensity and continuous aeration increased COD removal efficiency, particularly under continuous aeration for significantly raising the ratio of BOD/COD to improve efficiency of subsequent biological treatment.
Catalytic photodegradation of alkyl surfactants
Authors: Gelover S. , Leal T. , Bandala E.R. , Román A. , Jimenez A. , Estrada C.
Published: May 2018

An attempt to identify intermediate and final products of photocatalytic degradation of sodium dodecylbenzensulfonate (DBSNa) in aqueous solution was carried out. Synthetic samples of DBSNa containing TiO2 as catalyst were treated in a solar concentrator device. Samples were taken at regular intervals and analyzed by GC/MS. Two main types of signal were observed in the total ion chromatograms. The first group includes signals absent in the untreated sample that appeared during the first phases of the experiment and decreased toward the end. The second group comprised species already present in the untreated sample. There were signals in both groups probably because of stable oxygenated molecules that were accumulated to the end of treatment, indicating partial mineralization. Results clearly showed that degradation dynamic is complex. The detergent is fragmented into other products that undergo further reactions. The species distribution towards the end of the process is difficult to predict since it depends on a large number of variables including adsorption, reaction rates and the nature of the intermediate products. It is necessary to continue the study to determinate if these molecules are destroyed within the system for longer illumination times.
Production of activated carbon from petroleum coke and its application in water treatment for the removal of metals and phenol
Authors: Ramírez Zamora R.M. , Schouwenaars R. , Durán Moreno A. , Buitrón G.
Published: May 2018

The feasibility of the reuse of petroleum coke, withof high sulphur content, produced as waste in a Mexican petroleum refinery, its properties for use in water treatment was were assessed. Several classical activation methods were used and the physicochemical characteristics of the treated material were measured using normal ASTM standards. Use of scanning electron microscopy and microprobe analysis permitted most of the effects of the activation processes on the structure and properties of the coke. Adsorption capacities of mercury and silver and physicochemical characteristics determined for these activated carbons as well as scanning electron microscopy show that the H3PO4 is the best activating agent. It is shown that the process is highly promising for the production of an activated carbon aimed at the removal of heavy metals from wastewater.
Improvement of industrial wastewater treatment by aerated lagoon: case studies
Authors: Fonade C. , Rols J.L. , Goma G. , Doubrovine N. , Bermejo M. , Grasa J.P.
Published: May 2018

This paper deals with the aerobic biological treatment of industrial wastewaters by aerated lagoons, when high flowrates are involved. A methodology is developed which gives the best fit between the biological reactions and the ideal hydrodynamic behaviour of the lagoon. This analysis, based on the real kinetics of the degradation process, leads to the minimum volume and the ideal behaviour of the lagoon needed to reach the degree of conversion required to respect the discharge regulations. Because the flow field of a lagoon is of “shallow waters” type, appropriate technologies have been designed in order to achieve the mixing (by fluidic deviator) and the aeration (by hydroejector) in such a lagoon. Some applications of these methodologies and technologies to industrial problems in the chemical industry (pulp and paper) and food industry (sugar) are presented. This original approach is suitable for modifying existing aerated lagoons, or for upgrading natural lagoons to aerated lagoons, to successfully meet the new legislation on effluent quality.
Detection and origin of 3-chloro-4-dichloromethyl-5-hydroxy-2(5H)furanone (MX) in river water
Authors: Kinae N. , Tanaka J. , Kamio N. , Sugiyama C. , Furugori M. , Shimoi K. , Tanji K.
Published: May 2018

An isolation experiment of MX, a potent mutagen and promoter in drinking water, from river water contaminated with industrial and domestic sewage was carried out. The presence of MX was demonstrated by GC-MS-SIM method. The contribution ratio of MX to the total mutagenic activity of river water was 5–30%. To elucidate the origin of MX, several chemicals contained in domestic sewage were treated with sodium hypochlorite. From each reaction solution of catechin mixture, catechin and diosmin, MX was isolated and identified. These contribution ratios to the total mutagenicity of each reaction mixture were 36.3%, 95.5% and 4.3%, respectively. The results suggest that domestic sewage is a new origin of MX.
Recent epidemiological studies on itai-itai disease as a chronic cadmium poisoning in Japan
Authors: Kasuya M.
Published: May 2018

Itai-itai disease is a chronic cadmium poisoning with renal tubular dysfunction followed by osteomalacia. Renal tubular dysfunction among inhabitants of the cadmium-polluted Jinzu River basin was irreversible and progressive, despite the fact that cadmium exposure had decreased. The bone mass was decreased in the inhabitants living in cadmium-polluted areas with renal tubular dysfunction, correlating with the urinary β2-microglobulin level. The decreased bone mass was diagnosed as latent renal tubular osteomalacia. Low serum erythropoietin levels were detected among the patients with itai-itai-disease, despite the presence of severe anemia. The anemia found in the end-stage of the disease was closely associated with an impaired renal function. Health surveys in cadmium-polluted areas of 8 prefectures were carried out, and many cases of renal tubular dysfunction were found in 4 prefectures, although the most severe cases were found in Toyama Prefecture. Many cases whose clinical features are completely in accord with those of itai-itai disease with severe renal tubular dysfunction and osteomalacia were reported in 3 prefectures as well as Toyama Prefecture. Mortality risks were increased in the patients with itai-itai disease, in the group suspected of having the disease, and in the groups of mild renal tubular dysfunction with 300–<1,000 μg/g creatinine. The development stage of the disease was divided into three stages. Those are the mild stage (stage of cadmium nephropathy) with the renal tubular dysfunction and decreased bone mass, the typical stage with the severe renal tubular dysfunction and pseudofracture detectable by X-ray examination, and the serious stage with severe renal dysfunction and pseudofracture and/or fracture.
History of mercury migration from Minamata Bay to the Yatsushiro Sea
Authors: Kudo A. , Fujikawa Y. , Mitui M. , Sugahara M. , Tao G. , Zheng J. , Sasaki T. , Miyahara S. , Muramatsu T.
Published: May 2018

Mercury concentrations were measured in sediment cores collected from the Yatsushiro Sea to clarify physical transport of mercury from Minamata, the site of major methylmercury pollution in Japan, to the surrounding sea. The results suggested that the mercury pollution in the Yatsushiro Sea sediment was caused by a slow migration of mercury-bearing sediment particles from Minamata Bay. The deposition rate of mercury observed at the Yatsushiro Sea was correlated with cumulative loss of mercury from an acetaldehyde facility in Chisso Minamata, with a certain time-lag.
Fate of pesticides in a shallow reservoir
Authors: Itagaki N. , Nagafuchi O. , Takimoto K. , Okada M.
Published: May 2018

Based on the horizontal and vertical distributions of pesticides in the river and the reservoir, the fates of pesticides in these systems were investigated in this study. Four pesticides, i.e., MEP, thiobencarb, BPMC and isoprothiolane had the highest concentrations among the eighteen pesticides. These pesticides in suspended components except isoprothiolane were detected not only during stormy weather days but also during dry weather days. The percent detection of pesticides in suspended component was 59.8-61.9% in MEP, 34.6-38.9% in thiobencarb and 17.0–19.0% in BPMC. However, isoprothiolane in the suspended component was undetectable.

These pesticides in the suspended component have existed as a part of the suspended solids in the river, then disappeared by sedimentation during the flow of the river from the upper stream to the backwater in the reservoir. On the other hand, the pesticides in the dissolved components that flowed into the reservoir were uptaken or adsorbed by phytoplankton. Moreover, the concentrations of the less absorptive pesticides like isoprothiolane have decreased by dilution and diffusion in the reservoir.
Novel aspects for management of xenobiotic compounds in wastewater treatment plants – linking theory, field studies, regulation, engineering, and experience
Authors: Jacobsen B. N. , Guildal T.
Published: May 2018

Management aspects for control of environmental contaminants has widened from being focussed on heavy metals to a broader approach including specific organic compounds, inhibition of sensitive bacteria or algae, and newly identified environmental issues, e.g., endocrine disruption and antibiotic resistance.

Studies conducted at the Avedøre WWTP confirm the relevance of such newly discovered environmental problems, however, the order of magnitude of the effects do not seem alarming.

It is recommended in future research to establish links between occurrence of specific organic compounds and heavy metals to various measures of toxicity and bioaccumulation. Also data for specific biodegradation rates in WWTPs represent a bottleneck for simulating fate of specific organic compounds in the plants.
Removal of heavy metal from soil and groundwater by in-situ electrokinetic remediation
Authors: Shiba S. , Hino S. , Hirata Y. , Seno T.
Published: May 2018

The operational variables of electrokinetic remediation have not been cleared yet, because this method is relatively new and is an innovative technique in the aquifer remediation. In order to investigate the operational variables of the electrokinetic remediation, a mathematical model has been constructed based on the physico chemical mass transport process of heavy metals in pore water of contaminated aquifer. The transport of the heavy metals is driven not only by the hydraulic flow due to the injection of the purge water but also by the electromigration due to the application of the electric potential gradient. The electric potential between anode and cathode is the important operational variable for the electrokinetic remediation. From the numerical simulations with use of this model it is confirmed that the remediation starts from the up stream anode and gradually the heavy metal is transported to the down stream cathode and drawn out through the purge water.
An integrated approach to waste stabilization pond design in Marrakech
Authors: Boussaid A. , Ouazzani N. , Bouarab L. , Bouhoum K. , Lyakhloufi S.
Published: May 2018

Most wastewater treatment programs in Morocco are directed towards reuse of the effluent in irrigation. A ten-year running of an experimental two-stabilization-pond system in Marrakech showed that despite retention times around 50 days, the quality of the effluent corresponded to a restrictive irrigation reuse (B category according to the WHO guidelines). This quality can be achieved even with BOD loading reaching 780-1000 kg BOD / ha.d in one anoxic stabilization pond with a depth of 2.3 m and a retention time of 9.5 days. This primary anoxic pond did not show signs of organic matter over-loading with an active algae population, a pH all the time higher than 7 and a nematode egg concentration lower than 1 egg/L. The performance of such a system in terms of organic matter removal can be evaluated using a linear relation of the same type as the one proposed by Mac Gary and Pescod but with lower removal efficiency. However, nitrogen levels were still high with a concentration above FAO irrigation standards and can lead to groundwater quality degradation. We proposed an integrated approach to stabilization pond design that can be based on the required effluent quality to protect both public health (WHO guidelines) and the receiving environment. Groundwater vulnerability maps should be drawn and evaluated for nitrogen and other pollutant tolerance before any wastewater treatment system design. Models for nitrogen removal in stabilization ponds should be combined with those already in use for organic matter and pathogenic organisms removal to allow design of systems that are aesthetically attractive, sanitarily safe and harmless to the receiving environment.
The performance of the waste stabilisation pond system at Boujaad, Morocco
Authors: Yagoubi M. , Echihabi L. , Foutlane A. , Bourchich L. , Jellal J. , Wittland C. , El Yachioui M.
Published: May 2018

The wastewater stabilisation ponds system of the city of Boujaâd was constructed and put into operation in 1992. The two main objectives of this plant are the prevention of pollution of water resources and the environment by means of wastewater discharges as well as the saving of fresh water by means of reuse of treated wastewater for irrigation purposes. Within the period of March 1997 to March 1998 a comprehensive analysis campaign of both the raw and the treated wastewater at a number of different sampling points has been carried out in order to evaluate the treatment efficiency of this wastewater treatment plant.The results of these investigations showed an average raw wastewater flow of 1600 m3/d, which is well below the design flow of 2500 m3/d.

With respect to the physico-chemical treated wastewater quality and in comparison with the French treated wastewater standards (1980) these results indicated that 90 % of the wastewater samples showed BOD5-figures below the quoted French standard, whereas 83 % of the samples showed COD-figures above the corresponding French treated wastewater standard.

With average treated wastewater suspended solids contents of 56 mg/l the suspended solids removal rate has been determined as being in the range of 65 %.

If compared to the anticipated Moroccan wastewater standards for direct wastewater discharge into receiving water bodies as stipulated in the Moroccan Standards Project the obtained wastewater analysis results showed COD- and BOD5 values below these foreseen Moroccan wastewater discharge standards. The analysis results of SS, TKN and total phosphorus (Ptot) showed figures slightly above these Moroccan standards. In view of the microbiological wastewater characteristics the treated effluents of the Boujaâd WSP respond to the WHO directive with respect to wastewater to be used for restricted irrigation (category B).

Taking into consideration the CEC directive for wastewater generated by wastewater treatment plants and discharged to the environment, the efficiency of the Boujaâd WSP is relatively low with respect to the SS-removal, the removal of organic matter (expressed by BOD5 and COD) as well as the removal of nutrients (expressed by TKN and Ptot). This relatively low efficiency might basically be caused by the already highly diluted incoming raw wastewater, which again is caused by the effect of significant infiltration of groundwater into the sewerage network. Besides the evaluation of the overall treatment efficiency, detailed investigations of the performance of individual ponds have been carried out as well.
Microfiltration-adsorption hybrid system in organics removal from water
Authors: Ngo H.H. , Vigneswaran S. , Kim S.H. , Bidkar A. , Moon H.
Published: May 2018

A series of experiments was conducted with a Millipore flat plate microfiltration module modified to incorporate in-line powdered activated carbon (PAC) addition. In-line PAC was mixed continuously through a spiral mixing device for a predetermined time prior entering a membrane unit. The results showed that this system is excellent in removing fulvic acid (FA). This system provides to sufficient contact time for PAC to adsorb organics compared to the system with in-line adsorbent addition. More than 85% of FA was removed from water containing 8 mg/l of FA. To achieve this following conditions were used:.(i) a velocity gradient G (mixing intensity) of 160.4 s–1; (ii) a hydraulic residence time (mixing time) of 4 minutes; (iii) a PAC dose of 260 mg/l; and (iv) membrane pore size of 0.22 μm. In case of low FA concentration (e.g. 1.2 mg/l) in water, the removal efficiency was almost 100%. The removal efficiency also increased with the increase of mixing intensity and mixing time. The permeate flux slightly improved when a membrane of pore size 0.22 μm was used with shorter hydraulic residence time and lower PAC concentration. This paper presents a mathematical model developed based on surface diffusion. The model successfully predicted the performance of this hybrid system.
Dynamics of a waste stabilization pond in Chile
Authors: Herrera L. , Castillo G.
Published: May 2018

A 3-modular units facultative waste stabilisation pond was experimentally studied for performance and efficiency, in relation to its original design. The system was located at La Esmeralda, Melipilla a small town of the central region in Chile. It was found that treated water did not comply with treatment requirements due to overloading, flow dynamics, wrong assumptions regarding hydraulic mixing behaviour, and an overestimation of systems kinetics. The overloading in terms of flow led to a retention time which was 62% of original design. Furthermore, bad mixing further decreased the designed residence time to only 18%. The effluent did not meet the WHO faecal coliforms guidelines for unrestricted irrigation. The modelling work on the batch faecal coliforms and coliphage removal concluded that the effective decay rates were 1.359×1.087(T-20°C) day-1 for coliforms, and 0.439×1.044(T-20°C) day-1 for coliphages. The data was also well fitted by a model that incorporated solar radiation. However, model discrimination indicated that the dependence on temperature gave a better and more sensitive fit with the observed data. As the original design considered a lower faecal coliforms decay ratio, namely 0.7 day-1, the failure of the system had to relate more to mixing than overloading. Operational seasonal data (flow and retention time) and physical, chemical and microbiological parameters, and tracer studies are included. Some solutions for improving the La Esmeralda SWP performance are also discussed.
Macroscopic fluid flow conditions in spiral wound membrane elements: packed bed approach
Authors: Van Gauwbergen D. , Baeyens J.
Published: May 2018

The modelling of the reverse osmosis process is needed to fully evaluate its potential and facilitate scale up. The definition of the flow regime in the concentrate channel is of paramount importance. The present paper describes our experimental investigations on RTD and relates the RTD response curves to the regime of flow in the concentrate channel. Results demonstrate (i) that dead zones are present; (ii) that both a Plug Flow with Dispersion (PFD) and Probabilistic Time Delay (PTD) model can be used to characterise the flow; and (iii) that PFD- and PTD-model parameters assume nearly constant values for a given geometry which simplifies the prediction of the RTD for any desired flow rate.
Volume reduction of produced water generated from natural gas production process using membrane technology
Authors: Visvanathan C. , Svenstrup P. , Ariyamethee P.
Published: May 2018

This paper presents a case study of a natural gas production site covering various technical issues related to selection of an appropriate Reverse Osmosis (RO) system. The long-term field experience indicates the necessity of the selection of appropriate pretreatment systems for fouling-free RO operational conditions. The produced water has a variety of impurities such as oil and grease, process chemicals used for corrosion and scaling control, and dehydration of natural gas, etc. This situation leads to a complicated and extremely difficult task for a membrane specialist to design RO systems, especially the pre-treatment section.

Here as part of the pretreatment selection, two types of UF membrane modules viz. spiral wound and hollow fibre, with MWCO of 8000 and 50,000 Dalton respectively, were tested in parallel with NF membranes of the spiral wound type with MWCO 200 Dalton. The UF permeate is used as feed for RO compatibility testing. Both configurations of UF failed to be compatible, due to irreversible fouling of the RO membrane. The NF membrane, however, showed interesting results, due to membrane stability in terms of cleaning and fouling. The NF plant with 50% capacity gave a recovery of 75% and the RO plant gave a recovery of 60% versus the expected 92–95%. The long-term tests have indicated that the reminder of the membranes could be installed to achieve full capacity of the plant. This study also demonstrates the importance of selection of proper pre-treatment set-up for the RO system design.
Occurrence and removal of protozoan cysts and helminth eggs in waste stabilisation ponds in Marrakech
Authors: Bouhoum K. , Amahmid O. , Asmama S.
Published: May 2018

The present study aimed to determine the occurrence and removal of protozoan cysts and helminth eggs from municipal wastewater by pilot waste stabilisation ponds in the arid climate of Marrakech (Morocco). Protozoan cysts detected in raw wastewater at the entrance of the system were identified as Entamoeba histolytica, Giardia sp. and Entamoeba coli at a mean concentration of 1.5×104 cysts/l. Helminth eggs identified were Ascaris, Trichuris, Hymenolepis, Enterobius and Taenia with an average of 7.6 eggs/l. The effluent at the system outlet did not contain detectable cysts or eggs. Sludge samples collected in the pond basins resulted in detection of protozoan cysts and helminth eggs. Sedimentation therefore seems to be the main factor for cyst and egg elimination during wastewater treatment by waste stabilisation ponds. This phenomenon leads however to parasite accumulation in the sediment.
Optimal membrane selection for Brackish water desalination
Authors: Oron G. , Bick A.
Published: May 2018

An integrative approach for optimal membrane selection concerning desalting of brackish water is proposed. This approach is based on management modeling for the following subsystems: Intake, pretreatment, Reverse-Osmosis (RO) unit, post-treatment and brine disposal. The management modeling takes into account membrane performance considerations that include treatment levels and technical capabilities. Attention is also given to membrane replacement and permeates salinity.

The model is based on defining an objective (cost) function to be optimized. The optimum of the objective function is evaluated, subject to a series of technological and economical constraints. The results provide guidelines for optimal membrane selection, pretreatment technology and information regarding the system layout, optimal investment and water cost. According to the results, a design based on gravity filters and high flux membranes is preferred with respect to minimum permeate cost. Analyzing the results, indicates the sensitivity of the solution to interest rate and electric power cost.