bluuebunny/crossref_metadata_2025 huggingface dataset:
Mesocosm observations on the ecological response of an aquatic community to sediment contamination
Authors: Foekema E. M. , Kaag N. H. B. M. , van Hussel D. M. , Jak R. G. , Scholten M. C. Th. , v.d. Guchte C.
Published: May 2018

Between 1992 and 1997 the effects of contaminated sediment on an aquatic community were studied in outdoor mesocosms (2m3), one filled with ‘naturally’ polluted sediment from the sedimentation area ‘Ketelmeer’, the other with relatively clean sediment from the shallow lake ‘Oostvaardersplassen’. Negative effects of the contaminated sediment were observed on the population development of the amoeba species Arcella megastoma and Difflugia accuminata, the mysid shrimp Neomysis integer, the microlepidopteran Cataclysta lemnata and the cladoceran community, whereas the biting midge Culex sp. showed a preference for the contaminated system. The reduction of the grazing capacity of the cladoceran community resulted in higher algal densities in the ‘Ketelmeer’ mesocosm despite the fact that nutrient concentrations in the water column of both mesocosms were comparable.
Risk assessment of heavy metal contamination in Danube sediments from Hungary
Authors: Gruiz K. , Murányi A. , Molnár M. , Horváth B.
Published: May 2018

The aim of the current research is to establish a suitable Environmental Risk Assessment (ERA) scheme for Danube sediments in Hungary by determining contaminants' concentrations by chemical analysis and by assessing their ecotoxicological effects. Seventeen sedimentation sites were identified, mainly upstream of Budapest, between river kilometres 1811 and 1586. The heavy metal contents and basic properties of sediments were determined. Excess heavy metal content was used to characterize the extent of heavy metal contamination. Direct contact biotests were developed for testing the toxic effect of contaminated sediments. Ecotoxicological effects were measured by three bacterial tests and one plant bioassay. Effect Concentrations were determined by the inhibition of the bioluminescence of Photobacterium phosphoreum. The resultant inhibition of different partial toxic effects was characterized by Cu equivalent. Chemical and ecotoxicological results were studied together, making it possible to characterize the extent of the pollution and its biological effects at the same time. It was concluded that combined chemical and ecotoxicological characterization of contaminated sediments may serve as a strong basis for assessing the site-specific risk of heavy metal pollution.
Remediation of contaminated sediments in Oslo harbour, Norway
Authors: Hauge Audun , Konieczny Roger M. , Halvorsen Per Ø. , Eikum Arild
Published: May 2018

During the past 60-70 years, contaminated sediments from local rivers have been settling in the harbour basin of Oslo. This contamination, combined with that from other harbour activities, has developed into a serious pollution problem with both organic and inorganic contaminants. Since 1992 dredging activities have been restricted until the effect of dredging was determined and a safe disposal was found for the sediments. Because of this restriction, a conflict situation arose in terms of decreasing sailing depths, and dispersal of large quantities of contaminated sediments into the water column each day from ship traffic. A complete plan of action to remediate Oslo Harbour was started in 1994 and delivered to the State Pollution Control Authority (SFT) in August 1996. An evaluation of environmental risks connected to the remediation work has been carried out along with the determination of the requirements for the monitoring programme during and after the work. Preliminary evaluation of dredging techniques indicates that mechanic/hydraulic equipment will cause the least dispersion of sediment. Several options for treatment of the sediments have been evaluated. Study results point out that conditioning prior to disposal of the sediments in a confined disposal site in the harbour area, is the most cost effective solution. Seven disposal sites with a capacity of 0.5 mill. m3 have been identified. Two of the sites are integrated with a subsea road tunnel crossing the harbour basin. The other disposal sites will serve as new dock area after closure.
Design considerations for in-situ capping of contaminated sediments
Authors: Palermo Michael R.
Published: May 2018

In-Situ Capping (ISC) is defined as the placement of a subaqueous covering or cap of clean or suitable isolating material over an in-situ deposit of contaminated sediment. ISC is a potentially economical and effective approach for remediation of contaminated sediment. A number of sites have been remediated by in-situ capping operations worldwide. The U.S. Army Corps of Engineers (USACE) has developed detailed guidelines for planning, designing, constructing, and monitoring in-situ capping projects for the United States Environmental Protection Agency (USEPA). This paper briefly describes the major aspects of in-situ capping as an option and provides a summary of recent case studies.
Operational aspects on foaming in digesters caused by microthrix parvicella
Authors: Westlund Åsa Dillner , Hagland Eva , Rothman Maria
Published: May 2018

Foaming in the digesters has been observed several times at three large waste water treatment plants in Stockholm, Sweden. The foam is caused by the filamentous organism Microthrix parvicella, a hydrophobic filament which traps the gas bubbles and creates a foam. The foam in the digesters causes economical loss and a security hazard. Different solutions to prevent problems with foaming has been tried and applied. By increasing the sludge load in the biological stage the growth of Microthrix parvicella can be reduced. Decreasing the sludge level in the digesters or installing mixers in the gas phase can prevent the foam from blocking the gas pipe. Heating (70°C, 5 min) the excess sludge has in lab scale been shown to change the foam potential of activated sludge with a high content of Microthrix parvicella and could be used as a solution to prevent foaming.
Combined influence of temperature and process loading on the effluent concentration of biological treatment
Authors: Pöpel H. J. , Fischer A.
Published: May 2018

The influence of temperature on biological wastewater treatment is generally quantified by an exponential model for maximum growth (μmax) of bacteria or maximum conversion (vmax) for specific substrates. This “maximum” influence is also applied for reactor design, although recent experiences with nitrogen removal show little temperature effect on the effluent concentrations. The new parameter “process temperature influence” (dce/dT) on the effluent concentration is defined and quantified including the “kinetic temperature influence” plus process loading and reactor configuration. These interrelations are modelled and presented graphically. Also, dce/dT is expressed as “apparent temperature coefficient” θa for easy comparison with the kinetic coefficient. θa depends strongly on the degree of process loading and never reaches the magnitude of the kinetic coefficient. Especially at lower loadings this coefficient is almost equal to one proving very little temperature effect dce/dT. The derived model is verified by computer simulation. Hence, effluent concentrations of biological treatment are much less sensitive to temperature changes than quantified by the kinetic temperature coefficients θ. This significantly reduced temperature influence should be incorporated into the design of reactor volumes to ensure a realistic design (procedure) and reduce unnecessary investment cost. The presented model is a valuable tool in this respect.
Significance of biofilm structure on transport of inert particulates into biofilms
Authors: Okabe S. , Kuroda H. , Watanabe Y.
Published: May 2018

Evolutional changes in interior structures of mixed population biofilms grown on domestic wastewater were quantitatively analyzed using a cryosectioning technique and an image analysis. Meanwhile, transport of particulates into the biofilms was also experimentally investigated using fluorescent microbeads as tracers to relate the biofilm structure and particulate transport into the biofilm. Microscopic observation of the cryomicrotomy biofilm sections indicated the biofilms were very porous and consisted of interwinded filamentous biomass acting as a framework of the biofilm. A honeycomb structure was often found, which would make the biofilm more resistant to water flow. There were micropores with the diameter of about 10 μm microcolony aggregates attached to filamentous biomass and macropores with the diameter of 20–200 μm in the biomass matrix. These pores did not clog during two months of cultivation. Areal porosity was about 30% in the bottom biofilm and more than 90% in the surface. Significant difference in transport efficiency was not observed for various sizes of microbeads due to the presence of macropores. Therefore, even 10 μm tracer beads could quickly traverse throughout a biofilm 640 μm thick via water channels or macropores and then penetrated into the micropores. Convective transport from the bulk to the bottom biofilm, rather than molecular diffusion, was responsible for this rapid transport. Based on experimental results, it can be concluded that the biofilm structure seems to be well designed to maximize the transport efficiency of substrates and products and the strength of biofilm structure.
Immobilized biofilms on granular activated carbon for removal and accumulation of heavy metals from contaminated streams
Authors: Scott J. A. , Karanjkar A. M.
Published: May 2018

Biofilms consisting of a matrix of exopolysaccharide and microorganisms developed over granular activated carbon (GAC) enhance metal uptake from solution several times more than that achieved by GAC alone. By specifically employing GAC, there is also the opportunity of developing biofilm/GAC systems that can both entrap metals and also adsorb, and ultimately degrade, polluting organic residues such as pesticides. Targets for this type of process could be dump site leachates, mine tailings and other industrial wastes. The conditions under which the biofilm is developed, including pH and temperature have, therefore, been studied in terms of subsequent influence on metal bisorption.
A three-stage biofiltration process: performances of a pilot plant
Authors: Chudoba P. , Pujol R.
Published: May 2018

A three-stage biological aerated filter (BAF) pilot plant has been run, fed with a mechanically pre-treated municipal wastewater. The pilot plant consisted of a physico-chemical lamella sedimentation unit for suspended solids removal and soluble phosphorus precipitation, followed by three stages of up-flow biofilters: a BAF C for organic carbon removal, a BAF N for nitrification and a biological anoxic filter (BaF DN) for post-denitrification with methanol as an external organic carbon source. The main objective of the experiments was to study the process limits of this pilot plant under overloading conditions, and to evaluate the time necessary for recovery of normal operation after a period of strong overloading. The pilot plant was first operated at a nominal wastewater flow rate of 12 m3/h (according to previous conventional design rules for first generation of up-flow BAF), which was progressively increased up to 25 m3/h, a maximum value still enabling us to achieve the final effluent standards. Beyond this flow rate, a high organic carbon load applied to the BAF C was only partially removed by this filter, the rest had to be eliminated in the BAF N unit. Consequently, the factor directly limiting the tested pilot plant was the COD overloading of the BAF C, which indirectly influenced the nitrification in the BAF N. The maximum applied load eliminated by the pilot plant, at a wastewater flow rate of 25 m3/h, was 2 times higher than the nominal applied load at a wastewater flow rate of 12 m3/h. In the second experimental period, short-term strong overloadings were applied to the pilot plant operating in steady state conditions at a nominal flow rate, and the limiting process parameters were detected. A lower short-term overloading (32 m3/h = 2.66 times the nominal flow rate) had no effect on the quality of the final effluent, and different filters were able to remove short-term loadings as high as 25 kg COD/m3.d (BAF C), 1.6 kg NH4-N/m3.d (BAF N) and 3.2 kg NO3-N/m3.d (BaF DN). These loadings represent respectively 1.33 times the maximum applied load found in the first set of experiments and 2.66 times the nominal load at a wastewater flow rate of 12 m3/h. A higher short-term overloading (40 m3/h = 3.33 times the nominal flow rate) led to the same consequences as in the first period: a high organic load (up to 32 kg COD/m3.d for the BAF C) was partially removed in the BAF N, decreasing thus its nitrification capacity. The recovery of normal operation after the period of overloading was almost immediate. This study showed that it is very important to maintain the specific populations in separate reactors, in order to reduce the competition between different bacterial species and to enable the microorganisms to grow under optimal conditions. The tested treatment configuration is particularly suited for treating peak flow with high removal rates.
Improving stability of anaerobic biological reactors using composite ion exchangers
Authors: Mitra Indra N. , SenGupta Arup K. , Kugelman Irwin J.
Published: May 2018

Instability in anaerobic biological processes is caused primarily by the inhibition of methanogens due to (i) the buildup of volatile acids and a consequent reduction in pH under BOD overloading and (ii) heavy metal contamination of the feed. A three-year long study confirmed that the process stability can be greatly improved by retaining composite ion exchangers (CIX) within the anaerobic reactors. CIX is a polymeric ion exchanger with imino-diacetate functional group and thus can buffer the pH and arrest cationic heavy metals. Because of its cloth-like texture and thin-sheet morphology, CIX is compatible in a biological medium with a high solids content. After three years of operation, CIX did not foul and retained its original exchange capacity. Use of CIX in anaerobic bioreactors is particularly attractive for high-strength biological wastewater where unforeseen fluctuations in feed compositions are rather common.
Experimental test to evaluate performance of an anaerobic reactor provided with an external membrane unit
Authors: Elmaleh S. , Abdelmoumni L.
Published: May 2018

The coupling of a wastewater treatment anaerobic reactor with a microfiltration or ultrafiltration membrane is particularly attractive: lower sludge production than in an aerobic reactor, methane production and dissociation of the mean residence times of the different phases. However, the industrial development of such a process is hampered by membrane fouling which can be a result of many causes and require a comprehensive study especially fouling by anaerobic suspensions. In order to simplify the study, the different phases of anaerobic oxidation were separated and this work is focused on the filtration of an anaerobic suspension fed with acetic acid as the sole carbon source at 2 g/l TOC. The effluent quality was excellent without sludge production in spite of large variation of the liquid phase space time. The tested filtration elements were tubular Carbosep membranes. The M14 membrane showed the greatest flux of 120 l/m2 h at 0.5 bar and 25 Pa shear stress and the flux increased to 180 l/m2 h when a baffle was introduced. The main fouling mechanism appears to be the particle deposition on the membrane surface as no flux decline was observed at higher cross-flow velocity.
Inhibition kinetics for propionate degradation using propionate-enriched mixed cultures
Authors: Hyun S. H. , Young J. C. , Kim I. S.
Published: May 2018

To study propionate inhibition kinetics, seed cultures for the experiment were obtained from a propionate-enriched steady-state anaerobic Master Culture Reactor (MCR) operated under a semi-continuous mode for over six months. The MCR received a loading of 1.0 g propionate COD/l-day and was maintained at a temperature of 35±1°C. Tests using serum bottle reactors consisted of four phases. Phase I tests were conducted for measurement of anaerobic gas production as a screening step for a wide range of propionate concentrations. Phase II was a repeat of phase I but with more frequent sampling and detailed analysis of components in the liquid sample using gas chromatography. In phase III, different concentrations of acetate were added along with 1.0 g propionate COD/l to observe acetate inhibition of propionate degradation. Finally in phase IV, different concentrations of propionate were added along with 100 and 200 mg acetate/l to confirm the effect of mutual inhibition. Biokinetic and inhibition coefficients were obtained using models of Monod, Haldane, and Han and Levenspiel through the use of non-linear curve fitting technique. Results showed that the values of kp, maximum propionate utilization rate, and Ksp, half-velocity coefficient for propionate conversion, were 0.257 mg HPr/mg VSS-hr and 200 mg HPr/l, respectively. The values of kA, maximum acetate utilization rate, and KsA, half-velocity coefficient for acetate conversion, were 0.216 mg HAc/mg VSS-hr and 58 mg HAc/l, respectively. The results of phase III and IV tests indicated there was non-competitive inhibition when the acetate concentration in the reactor exceeded 200 mg/l.
Propionic acid accumulation in anaerobic digestion of carbohydrates: an investigation on the role of hydrogen gas
Authors: Inanc B. , Matsui S. , Ide S.
Published: May 2018

This paper describes the experimental investigation into the accumulation of propionic acid under artificially lowered or elevated hydrogen gas levels. Vacuum operation at 0.13, 0.5, and 0.75 atm on the headspace of the reactors, and a selective permeable Teflon membrane placed in the liquid phase, were used to provide low hydrogen concentrations. In the elevated hydrogen concentration experiments, first, hydrogen gas (20% H2 + 80% N2) was bubbled into a batch CSTR reactor. Second, purer H2 gas (80% H2 + 20% CO2) was overpressurized at 2 atm in vials. Suspended cultures were used in all the experiments. The results have suggested no inhibition or stimulation effect by elevated or lowered hydrogen on the accumulation of propionic acid.
Recirculation of powdered activated carbon for the adsorption of dyes in municipal wastewater treatment plants
Authors: Nicolet L. , Rott U.
Published: May 2018

The use and recirculation of powdered activated carbon (PAC) as an advanced treatment for colour removal in municipal wastewater treatment plants is presented. Studied wastewaters consist of domestic effluents with a high portion of dyehouse residual waters. The particularity of the treatment is that PAC is not disposed of before being recirculated several times. Therefore, it enables the use of a great part of the total adsorption capacity of the PAC. A positive side effect is that halogenated and refractory organic compounds, which are not degraded by micro-organisms in a conventional municipal wastewater treatment plant, are removed too. This paper describes results which were obtained in batch experiments and in a pilot plant during two years of observation, and concludes with advantages and drawbacks of this technology.
Wastewater control and management in a leather tanning district
Authors: Kabdaşlı I. , Tünay O. , Orhon D.
Published: May 2018

Initial assessment of industrial structure and wastewater characteristics is important for successful environmental management in an industrial district. This is particularly important for the cases where highly polluting industries such leather tanners are of concern. In this study, Biga Leather Tanners District was evaluated. The process characteristics, wastewater amounts, wastewater quality and their variations with time were defined. The district housed 46 tanning plants, processing mainly sheepskins with a total capacity of 66.5 tons skin per day. Process profile was prepared and checked with experimental data. Chemical treatability experiments were conducted to assess the pretreatment alternatives. Chemical precipitation preceded by catalytic air oxidation of sulfide was found to be an optimum pretreatment system providing COD and TKN removals up to 80% together with complete chromium removal, Results of the study were evaluated and discussed.
Colour removal from fermentation industry effluents
Authors: Inanc B. , Ciner F. , Ozturk I.
Published: May 2018

Large amounts of effluents from the fermentation industry are characterized by high COD and colour. Although significant reduction in COD is achieved through biological treatment processes, a substantial amount of colour remains. Coagulation and flocculation with alum and iron salts are not effective for colour removal. This is due to the nature of colour causing compounds which are almost totally dissolved and resistant to biodegradation. Hence, fermentation industries face difficulties in discharging their coloured effluents into either sewers or surface waters. In this study, colour removal from biological treatment plant effluents of a fermentation industry with lime and ozone was investigated experimentally. Optimum lime dose for reducing the colour to values around 1000 Pt-Co was found as 10.0 g/l, while 0.9 g/l ozone was necessary to obtain the same residual colour. Economic evaluation has indicated that cost of lime treatment was 1.3 to 1.4 USD/m3 while it was 2.5 USD/m3 for ozone treatment. Annual total costs for lime and ozone treatment were also estimated as 2 million USD and 3.65 million USD, respectively.
Transformation of industrial food wastes into polyhydroxyalkanoates
Authors: Yu P. H. F. , Chua H. , Huang A. L. , Lo W. H. , Ho K. P.
Published: May 2018

Due to the synthetic and biologically inert nature of petroleum-derived plastics, the disposal of these solid wastes has been a focus of concern for waste management. Thus, the demand for biodegradable plastics has become a highly visible issue. Broader usage of biodegradable plastics in packaging and disposable products as a solution to environmental problems would heavily depend on further reduction in costs and the discovery of novel biodegradable plastics with improved properties. As the first step in pursuit of eventual usage of industrial food wastewater as nutrients for microorganisms to synthesize environmental-friendly bioplastics, the usage of soya wastes and malt wastes from a beer brewery plant were investigated as the carbon sources for the production of bioplastics. Bench experiments showed that microorganisms from the municipal activated sludges used the nutrients from malt and soya wastes to biosynthesise PHAs. The results of experiments indicated that with the proper selection of the type of food wastes as the carbon source, bioplastics with specific PHAs copolymers could be produced with distinct polymer physical properties.
Assessing the impact of agricultural land use changes on water quality
Authors: Meissner R. , Seeger J. , Rupp H. , Balla H.
Published: May 2018

To study and predict environmental impacts of land use changes on water quality we conducted different types of lysimeter experiments. All of them are linked to representative experimental catchment areas in the field. This allows the verification and extrapolation of lysimeter results. The objective of this paper is to discuss a strategy for using and scaling-up of lysimeter results to a field and catchment scale. It will be shown that the N-loss determined with lysimeters falls within the variation of N-balance based model calculations, and also within ground water recharge rates calculated with models commonly used in hydrology. Extrapolation of lysimeter data to a catchment with similar soils provides a reliable basis for estimating the N-leaching caused by a change in agricultural land use. On the basis of the N-loss from the soil and the N-load of the stream, the calculations show that an increase in the proportion of one year rotation fallow from 10 to 25% results in nearly a 10% increase in the N-load of the stream. However, from the point of view of protecting drinking water quality, rotation fallow for one year is not recommended because of the resulting intensified leaching of nitrates.
The impact of agricultural pollutants in six drinking water reservoirs
Authors: Tanik A. , Beler Baykal B. , Gonenc I. E.
Published: May 2018

Water is supplied in the Greater Istanbul Metropolitan Area from the surface water of six main reservoirs. The present land use in the catchment areas of the reservoirs indicates that the area devoted to agricultural activities and to forests and meadows varies between 73 and 97% and that only a minor percentage, 1-26%, is devoted to settlements and industries. In contrast to the land use profile, the current environmental evaluation of the catchment areas reveals that point sources dominate over diffuse sources. However, this trend is expected to be reversed in the near future, making diffuse sources and control of fertilizers and pesticides the most significant issue. Pollutant loads regarding pesticides and fertilizers are calculated from unit loads based on area. These pollutants are observed to have a negative impact on water quality in terms of eutrophication and toxicity. In this paper, the status of fertilizers and pesticides are addressed and some protective measures for reducing the impact of agricultural pollutants in the reservoirs are recommended.
Pollution wash-off modelling on impervious surfaces: calibration, validation, transposition
Authors: Zug M. , Phan L. , Bellefleur D. , Scrivener O.
Published: May 2018

This paper presents the modification and the application of the conceptual wash-off model initially proposed by the SWMM on five separate urban catchments with very different characteristics and during a lot of rainfall events. To allow measurements on real sites to be considered, this model was incorporated in an overall model including simulation build-up, sediment transport in collector as well as runoff and hydraulics. This modified model has been calibrated, validated, transposed and completed with sensitivity analysis of parameters and initial conditions. The proposed model gives some improvement to the results of the initial model: an adaptation to a large range of rainfalls, the correct reproduction of the peak values and satisfying reproduction of the beginning and the end of the TSS pollutograph.
Denitrification of groundwater using acetic acid as a carbon source
Authors: Mohseni-Bandpi A. , Elliott D. J. , Momeny-Mazdeh A.
Published: May 2018

A pilot scale rotating biological contactor was used to investigate the ability to remove nitrate from groundwater using acetic acid as a carbon source under various operating conditions. The reactor achieved a nitrate removal efficiency of 99 to 83 percent at loading rates of 76 and 490 mg/m2.hr respectively with a flow rate of 2.5 l/min at 20±2°C. The nitrate removal rate was found to be dependent on the influent acetic acid loading rate. The optimum acetic acid to nitrate-nitrogen (A/N) ratio was found to be 4.3:1. Under optimum conditions the effluent nitrate, nitrite-nitrogen and residual acetic acid concentrations were 0.43, 0.03 and 4.4 mg/l. The process generally produced low nitrite intermediate production for up to 100 mg/l influent nitrate-nitrogen. The results of this study show that an anoxic RBC using acetic acid as a carbon source is a convenient and reliable process for the removal of nitrate from water supply. Pseudomonas were found to be the dominant bacterial species with species being Ps. stutzeri and Ps. fluorescence.
H2S paper strip method – a bacteriological test for faecal coliforms in drinking water at various temperatures
Authors: Pillai J. , Mathew K. , Gibbs R. , Ho G. E.
Published: May 2018

Epidemics arising from waterborne diseases are a global health problem. Faecal contamination of drinking water is the main cause of these outbreaks. According to WHO (1996) for drinking water to be safe, a 100 ml sample should not contain any coliform bacteria. The standard methods currently used for routine testing have many limitations especially when applied in remote areas. The H2S method has been developed as an on-site, inexpensive and easy to use method to test drinking water for remote and rural areas. The present work analyses the reliability of the H2S method for detecting faecal contamination in drinking water. The minimum level of faecal coliforms that could be detected and the incubation period required at various levels of contamination were studied. The range of temperatures at which the method was effective and the incubation period required at various temperatures were also determined. The H2S method was found to be able to detect contamination down to a level of 1 CFU/100 ml of coliform bacteria. Although the H2S method could be used at a temperature range of 20 to 44°C, temperatures between 28 to 37°C gave faster results. An incubation period of only 24 hours was required at 37°C, which was found to be the most suitable incubation temperature. The incubation period increased with a decrease or increase in temperature.
Overview of water environment priorities in Hong Kong (China)
Authors: Chua H.
Published: May 2018

Hong Kong produces over two million tonnes of municipal wastewater each day. Until recently, 50% of the wastewater volume entered water courses, rivers and coastal waters without treatment. Untreated organics, heavy metals and refractory synthetic materials accumulate in certain areas, and have led to breakdown of aquatic and marine ecological systems, closure of beaches, red tides and bioaccumulation in seafood. In 1986, a flexible framework of environmental management master plan was designed, to be implemented over the following two decades. The master plan comprises (1) establishment of water control zones and pollution control legislation, (2) upgrading of services and facilities for management of municipal sewage and chemical wastes, (3) construction of the “Strategic Sewage Disposal Scheme”, and (4) implementation of a “polluter pays policy”. This paper critically reviews the legislation and management priorities relevant to the water environment.
Nutrient removal mechanisms in constructed wetlands and sustainable water management
Authors: Sakadevan K. , Bavor H. J.
Published: May 2018

Constructed wetland systems are used to treat domestic and industrial wastewater and agricultural runoff. In this field study the influence of hydraulic loading, retention time, water column depth and phosphorus (P) concentrations of influent wastewater on P and nitrogen (N) removal was examined in experimental constructed wetland systems. Five constructed wetlands with a surface area of 150 m2, were developed in the field. Results showed that P concentrations of water from outlets of all five systems decreased (from as low as 11% decrease for the system which received wastewater with average P concentration of 8.2 mg P L−1 to as high as 48.9% decrease for the system which received wastewater with average P concentration of 3.58 mg P L−1) compared to the influent water. The N concentrations in the outlet water were also decreased in all five systems (from as low as 26.3% decrease to as high as 77.5% decrease) compared to the influent water. The total P and N in the wetland sediment increased in the first year in all five systems but were unchanged at the end of the second year. The study showed that low hydraulic loading and greater retention times positively enhanced removal of P and N from wastewater in constructed wetland systems.
Polyelectrolyte treatment – an approach for water quality improvement
Authors: Rout D. , Verma R. , Agarwal S. K.
Published: May 2018

Contamination of industrial water by suspended materials such as mud, dirt, turbidity, organic matter and decaying vegetation can be a serious operational problem besides reducing its aesthetic quality. The clarity of water is affected due to overloading of the clarifier and during the rainy season when turbidity is high. The operational problems encountered during alum and lime treatment programme and the improvement of clarification of raw water by using diallyl dimethyl ammonium chloride (DADMAC), a hetero-ally-cyclic organic polymer are discussed. This paper discusses the chemistry of coagulation and benefits of polyelectrolytes. Treatment recommendations and dosage of polyelectrolyte are discussed in terms of an overall system approach. The use of this organic polymer could improve the overall efficiency of raw water treatment plant with increased throughput, reduced plant maintenance and better water quality. The replacement of alum treatment is cost effective with a substantial cost savings of 25 to 30%.
Ammonium ion (NH4+) removal from secondary effluent through ion-exchange: the effect of biological activity and the presence of other cations
Authors: McVeigh Ryan , Weatherley Laurence
Published: May 2018

This paper is concerned with ion-exchange removal packed bed studies carried out with secondary effluent on a sewage treatment works. The work was carried out over a five month secondment period with Severn Trent Water, situated in the midlands of England. The objective of the work was to compare previous studies with clinoptilolite using synthetic wastewaters, de-ionised water and appropriate salts, with typical process water found on a sewage treatment plant. Experimental results have shown ammonium removal of 90% and greater of the influent NH4+ concentrations. In this report it has been shown that the biological activity of nitrification takes place during the upflow processing of wastewater through the packed beds. It is also shown how other cations cause an inhibitory effect on the ion-exchange process whereas biological activity leads to improved efficiency.
Chemical, Physical and Biological Cycles in Treatment Wetlands
Authors: Kadlec Robert H.
Published: May 2018

Treatment wetlands are solar powered ecosystems. Solar radiation varies diurnally, as well as on an annual basis. Wetland processes are therefore driven to respond on these same two cyclic periods. The first and most obvious effect is on the temperature of the water and soils in the wetland. Intense summer radiation results in warmer conditions and higher evapotranspiration. Winter radiation is smaller, and results in cooler temperatures and less evapotranspiration. Other meteorological variables, such as air temperature, humidity and precipitation, also have annual cycles, but with considerable stochastic variability. The water and soil temperature variations cause changes in microbial activity, which in turn creates changes in microbially-mediated water quality improvement. The cyclic changes in rain and evapotranspiration may create significant effects on the water budget for the wetland, and thus influence treatment efficiency. In addition, there are seasonal cycles in the vegetation and litter in the system, which occur in response to solar inputs and meteorological factors. This causes seasonal changes in nutrient and chemical uptake and release. This combination of cyclic influences is reflected in the treatment performance of the constructed wetland. It is shown that wetland water temperature alone is not a sufficient descriptor of wetland biogeochemical cycles. Mass balances demonstrate cyclic interactions in treatment wetlands. The effects of vegetative cycles are quantified for an example system.
Management of Dairy Waste in the Sonoran Desert Using Constructed Wetland Technology
Authors: Karpiscak Martin M. , Freitas Robert J. , Gerba Charles P. , Sanchez Luis R. , Shamir Eylon
Published: May 2018

An integrated wastewater treatment facility, consisting of upper (solids separators, anaerobic lagoons, and aerobic ponds) and lower (wetland cells) subsystems, has been built to replace the lagoon at a dairy in Arizona, USA. The collection sump of the new waste treatment facility collects all dairy wastewater outflow. Wastewater is then pumped to solids separators, and flows by gravity to anaerobic ponds and aerobic ponds. The upper subsystem is expected to treat the water sufficiently so that the wetland cells may achieve further pollutant reductions. The lower subsystem, comprised of 8 surface wetland cells with an approximate surface area of 5,000 m2, receives outflow from the ponds. The cells are planted with cattail (Typha domingensis), soft-stem bulrush (Scirpus validus), and reed (Phragmites australis). After treatment is completed via the lagoons and ponds followed by the wetland cells, the wastewater can be reused to flush barns or to irrigate crops. Performance of the overall system is evaluated by measuring physical, chemical and biological parameters in water samples taken from selected locations along the treatment system. Chemical parameters studied include biochemical oxygen demand, pH, total suspended solids, nitrogen species. Biological monitoring included coliforms (total and fecal) and Listeria monocytogenes.
Overland transport of nitrate: algorithms validation
Authors: Preti F.
Published: May 2018

An efficient and integrated approach for the study of overland transport of nitrate during runoff can be achieved by coupling water quality automatic monitoring and distributed parameter modeling. A semi-distributed model, essentially based upon a spatial discretization of the territory into square cells and upon a schematization of the main hydrological processes of erosion, transformation and transport of the chemical substances, was set up. It performs the lumped analysis of overland transport of nitrate (for the elementary cell of spatial discretization or experimental plot scale) and the distributed analysis with routing to the outlet of the watershed. In the present work the mathematical algorithms and the validation of the model are presented.
Assessment of Effective Specific Surface Area for Free Water Surface Constructed Wetlands
Authors: Khatiwada N. R. , Polprasert C.
Published: May 2018

Biofilm bacteria attached to submerged surfaces play a major role in organic matter degradation in free-water-surface(FWS) constructed wetlands used for wastewater treatment. Effective specific surface area (as) available for the biofilm bacteria is an important parameter in organic matter degradation and in describing the biofilm kinetic models used in the design and operation of constructed wetlands. In this study, kinetic models based on two possible biofilm geometries were developed for the determination of as and its non-dimensionalised value or area factor (δ). The as and δ values were estimated for a laboratory FWS constructed wetland treating domestic wastewater based on the chemical oxygen demand (COD) removal performance and other kinetic parameters. With the assumption of slab geometry for the biofilm, the values of as and δ were found as 3.15 m2/m3 and 2.2 for the lab unit having 80% mass COD removal, whereas by considering the cylindrical geometry for the biofilm attached on the lateral roots higher values of as and δ were obtained.
Water, soil and chemical losses: field experiments and model analysis
Authors: Pisa P. Rossi , Preti F. , Rossi M. , Ventura F. , Mazzanti B.
Published: May 2018

The study of the environmental impact of water erosion, chemicals and nutrient transport by runoff water is very important to protect soil and water quality. It is possible to find much literature on this topic, but the survey data lack uniformity and represent many different agronomic or natural environments. This is due to the wide range of parameters involved in these phenomena, such as soil and geomorphologic characteristics, tillage and crop management, nutrients and pesticides used.

Results of some experiments are presented in this paper. A comparison of water, soil and chemical losses has been made between experimental data and modeling outputs, both at plot and at watershed scale. The findings indicate that monitoring and modeling are two complementary instruments, both necessary for the analysis of agrochemical transport phenomena, and that the proposed methodology is useful to evaluate the related environmental impact under different scenarios.
Domestic Effluent Treatment through Integrated System of Septic Tank and Root Zone
Authors: Philippi Luiz S. , da Costa Rejane H. R. , Sezerino Pablo H.
Published: May 2018

According to national statistical data, only 10% of the Brazilian urban population have their sewage treated. In the rural areas, where people usually treat sewage trough septic tank systems, this value is not greater than 5%. This situation, therefore, depicts a lack of basic sanitation in Brazil, which, in turn, is responsible for the utilisation of individual systems for the treatment of sewage by more than 100 million people. Generally, soils and water rivers are, no longer, the last fate for the discharged effluents. Wetland system for the treatment of domestic sewage have been employed in different situations and arrangements (combined system) always showing outstanding performances.

The reasons which qualify this system for the treatment of effluents have been attributed to its low cost, easy maintenance and operation.

The experiment was carried out in the Agriculture Secretary's Training Center, Santa Catarina State, responsible for servicing approximately 66 people daily, and was fed with local effluent.

This work assesses the efficacy of such a kind of system, which is composed of a septic tank followed by the root zone, in the treatment of liquid effluents.
The federal clean lakes program works
Authors: Davenport Thomas E.
Published: May 2018

In the United States, the Clean Lakes Program was created to assist locals in managing and restoring their lakes. Utilizing a holistic framework for water quality management, this multiphase program has supported the successful restoration of lakes all over the country. Locals have found the Clean Lakes approach to be a cost effective way to restore their lakes. Two case studies are presented to demonstrate the value and effectiveness of the Clean Lakes approach.
Two-Stage Constructed Wetland for Treating Hospital Wastewater in Nepal
Authors: Laber Johannes , Haberl Raimund , Shrestha Roshan
Published: May 2018

To treat the wastewater of a hospital at Dhulikhel/Nepal, a two-stage constructed wetland was built with a settlement tank, a horizontal flow bed as first stage and a vertical flow bed as second stage. The plant is operated without electric power. The aim was the elimination of organic compounds, nitrification and a significant reduction of indicator bacteria. Different phases of operation (high and low water level within the soil profile, serial operation, one stage operation) were investigated, of which the serial operation with high water level in the horizontal flow bed and low water level in the vertical flow bed showed the best elimination performance. The areal removal rate constants (k-values) turned out to be very high (especially of the vertical flow bed) compared with literature values of other subsurface flow constructed wetlands. For the vertical flow bed kCOD was 0.22 m/d and kNH4-N was 0.85 m/d during serial operation. For kNH4-N a strong correlation with the hydraulic loading rate and the COD inlet concentration was found.
Restoration of Lake Borrevannet – Self-Purification of Nutrients and Suspended Matter through Natural Reed-Belts
Authors: Bratli J. L. , Skiple A. , Mjelde M.
Published: May 2018

A three-year large-scale study for estimating the retention of nutrients and suspended matter has been carried out in a wetland (littoral reed-belt) in the southern part of Lake Borrevannet, in the south-east of Norway. The reed-belt adjacent to the lake was isolated with a 250 m long reinforced PVC-membrane equipped with a tunnel for transportation of water out of the wetland. Inputs, mainly from agricultural runoff, were measured at seven inlet stations. Calculations of retention show a substantial retention of suspended matter and residue on ignition, respectively 94 and 97% for the whole period 1994-96. Total phosphorus shows a mean value of 65%. The retention of orthophosphate was 85%. Nitrogen shows a lower retention rate, 44% for total nitrogen, somewhat lower for ammonia and somewhat higher for nitrate. For suspended matter/residue on ignition and for the phosphorus fractions, there was a high retention rate also during the winter period. For nitrogen, however, there was a significant reduction in the retention rate in the winter period. While in the summer period, 50-85% of the total nitrogen was held back this was down to 30% in the winter period.
Treatment of Combined Sewer Overflows at Small Wastewater Treatment Works by Constructed Reed Beds
Authors: Green M. B. , Martin J. R. , Griffin P.
Published: May 2018

The performance of constructed reed beds is illustrated by examination of results of surveys from a sewage treatment works with storm treatment reed beds and another site with a combined storm and tertiary treatment reed bed. During surveys of the first system the average hydraulic loads were between 25 and 40 cm d−1 and removals of between 6.7 to 15.4 g m−2 d BOD5, 17.7 to 38.6 g m−2 d TSS, 0.43 to 0.99 g m−2 d NH4N and 0.63 to 0.76 g m−2 d TON were observed. A survey during a storm at the combined storm and tertiary treatment reed bed showed a hydraulic loading of 98 cm d−1 in the first 24 hr and removals of 12.6 g m−2 d BOD5, 29.9 g m−2 d TSS, 0.49 g m−2 d NH4N and a small increase in TON. The sustainability of the high rate of removal during storm events is ascribed to the longer intervals in which loadings are much lower. Samples taken by the regulator from the time of commissioning of 20 sites with combined storm and tertiary treatment reed beds, up to the end of May 1998 are examined. Three of these had operational problems not associated with storm treatment. The aggregate data for the remaining 17 sites (n=906 to 911) illustrate a level of performance matching that of sites with tertiary treatment systems, with averages of 2.2 mg l−1 BOD5, 3.0 mg l−1 TSS, 1.25 mg l−1 NH4N and 12.2 mg l−1 TON.
Modeling activated sludge mass transfer in a treatment plant
Authors: Joannis C. , Aumond M. , Dauphin S. , Ruban G. , Deguin A. , Bridoux G.
Published: May 2018

To keep overflows of raw effluent to a minimum during wet weather conditions, we investigated the ability of a secondary clarifier of an activated sludge treatment plant to accept hydraulic overloads without being washed out. The experiments, which were conducted on a full scale 8000 p.e. treatment plant, showed the feasibility of the project, and suggested some features, which were included in a one-dimensional model designed to study the behavior of the sludge blanket in the clarifier. This model takes into account the effect of convection currents, suspected to play an important part in the rising of sludge blankets. The sensitivity of the model to sludge settleability prevented its use with long times-series, unless a continuous recalibration was performed. Nevertheless, this model appears very interesting for a better understanding of the dynamics of the clarifier, as described by measured data. It could be used in relation with sensors to improve the operation of the treatment plant.
Operating diagnostics on a flocculator-settling tank using fluent CFD software
Authors: Lainé S. , Phan L. , Pellarin P. , Robert P.
Published: May 2018

FLUENT CFD software was used to form an understanding of a periodic dysfunction at a drinking water production plant at a site in North Africa. The structure involved is a circular, 27-metre diameter, flocculator-settling tank, supplied with surface water taken from the nearby river. The following dysfunction was observed on the structure in question. In summer, during the hottest time of the day, a cloud of flocs would sometimes rise to the surface, appearing in the centre of the settling zone. The cloud then progressed slowly to the outer zone of the tank, where a proportion of the total suspended solids (TSS) would overflow, impairing the quality of the treated water. The CFD simulations enabled us to understand the precise mechanisms in operation when the phenomenon is observed.