bluuebunny/crossref_metadata_2025 huggingface dataset:
Treatment of landfill leachate in on-site lagoons and constructed wetlands
Authors: Mæhlum T.
Published: May 2018

On-site “high-tech” leachate treatment systems are often avoided due to large construction and operation costs. Alternative integrated methods need to be examined. This paper describes a biological treatment system, capturing leachate from a municipal sanitary waste (MSW) landfill on-site. The area has a typical cool temperate continental climate. The treatment system is built in a ravine and has been operating since July 1993. The average flow is estimated to be 120 m3 d−1. The low-strength leachate is first treated in a 400 m3 anaerobic pond. Stage 2 is a 4000 m3 aerated lagoon with 3 AIRE-O2 aspirator propeller aerators/mixers. Oxidation of organic matter, NH4-N and Fe take place in this lagoon. Stage 3 is two parallel constructed wetlands (CWs) with horizontal subsurface flow, each with an area of 400 m2. The filters consist of (i) washed gravel and (ii) Light Expanded Clay Aggregates, LECA (size range 10-20 mm). The CWs were planted with Phragmites australis and Typha latifólia. Stage 4 is a 2000 m2 free water surface CW, planted with Scirpus and Typha. The integrated system has no moving parts, except for the aerators. The overall removal of organic matter, N, P, Fe and pathogenes is promising (70-95%). The paper presents combinations with the use of conventional and natural systems in MSW landfill leachate treatment.
Accumulation of organic solids in gravel-bed constructed wetlands
Authors: Tanner Chris C. , Sukias James P.
Published: May 2018

The effects of wastewater loading rate and planting with Schoenoplectus validus (soft-stem bulrush) on the accumulation of organic matter were investigated in four pairs of gravel-bed constructed wetlands. The planted and unplanted wetland pairs, each supplied with a different hydraulic loading of dairy farm wastewaters pre-treated in an anaerobic and aerobic lagoon, had received cumulative suspended solids loadings (∼ 82% volatile) of between ∼ 1.6 and 5.4 kg m−2 over a 22 month period. Vertical and horizontal gradients of organic matter accumulation were sampled by stratified coring, and the impact of solids accumulations on wastewater residence times investigated using bromide as a conservative tracer. Mean accumulations of organic matter in the unplanted wetlands ranged between 0.4 and 2.3 kg m−2, while those in the planted wetlands reached mean levels of nearly 4 kg m−2. Highest levels were recorded in influent zones (up to 9.5 kg m−2) and in the upper 100 mm of the substratum. The effective porosity of the highest loaded wetlands was markedly reduced compared to that in the lowest loaded wetlands, with mean retention times decreasing to around half of their theoretical values (corrected for evapotranspirational water losses). The planted wetlands retained higher apparent gravel porosity, despite greater accumulations of organic matter. High evapotranspiration rates during hot summer days, markedly extended retention times and increased tracer dispersion.
Variability of treatment performance in constructed wetlands
Authors: Kuehn E. , Moore James A.
Published: May 2018

Eight constructed wetland ponds treating pulp mill effluent were monitored for removal of biochemical oxygen demand (BOD) and total suspended solids (TSS). Matched pairs of ponds differed by retention times and vegetation types. Analysis showed that variations over time between pairs of similar ponds were small. Performance of similarly designed constructed wetlands should be similar. TSS effluent concentrations varied by vegetation type, while BOD effluent concentrations varied with season.
Selective mechanisms controlling algal succession in Aydat lake
Authors: Lafforgue Michel , Szeligiewicz Wojciech , Devaux Jean , Poulin Michel
Published: May 2018

Aydat lake is a dimictic eutrophic lake where Cyanophycean blooms occur. In order to study with accuracy this lake functioning, a one-dimensional vertical model (Licorne 2 model) was developed. This model takes into account physical, chemical and biological interactions and simulates the algal succession of the five main phytoplankton algae for two different years (1984 and 1985).

It appears that the growth rate, the sedimentation rate, or the death rate do not explain by themselves the algal succession, and more specially the blue-green blooms.

However, a good correlation between field data and Licorne 2 results are obtained by introducing specific advantages of blue-green algae such as buoyancy regulation mechanisms, capacity to fix atmospheric nitrogen and to grow at high pH value and toxin production.

In the view of these results, a new understanding of the Aydat lake algal succession is then possible, where competition for light, food and limitation of the losses (sedimentation, grazing) take an important place in a thermal and chemical vertical stratified environment.
Flow cytometry: a powerful tool in analysis of biomass distributions in phytoplankton
Authors: Jonker R. R. , Meulemans J. T. , Dubelaar G. B. J. , Wilkins M. F. , Ringelberg J.
Published: May 2018

The large range in concentrations and cell-sizes of algal cells and colonies and the large variety of cell types are the main reasons for developing a dedicated cytometer for the analysis of phytoplankton. A European Community funded consortium has developed the EurOPA cytometer, which is easily transported and can be operated at sea. With the EurOPA, both small single cells and large colonies of cyanobacteria can be analyzed in one run. This provides correlated information on optical characteristics, pigments contents and taxonomy. The resulting distribution of (chlorophyll) biomass over taxonomic groups can be inter-calibrated with standard spectrometric analysis techniques. The EurOPA can be used successfully for analysis of field samples and phytoplankton cultures. It is well suited for phytoplankton monitoring and grazing studies.
Mousetrap: modelling of water quality processes and the interaction of sediments and pollutants in sewers
Authors: Garsdal Henrik , Mark Ole , Dørge Jesper , Jepsen Svend-Erik
Published: May 2018

A water quality model has been developed with the objective of describing the water quality processes in sewer systems. The model has the capability of simulating both dissolved and sediment attached pollutants. This paper describes the modelling approach for the water quality processes and it demonstrates a small application of the water quality model to a gravity sewer operating under aerobic conditions. The application shows that the transport of dissolved substances in sewers can be accurately described and that the water quality processes are simulated with acceptable results.
Determination of the pollutant far-fields dilution using variable turbulent diffusion coefficients
Authors: Gardanov T. V.
Published: May 2018

The main subject of the paper is deriving appropriate relationships to calculate the horizontal turbulent diffusion coefficient, the size of the far-field polluted plume and the concentration distribution in the case of the continuous steady state wastewater discharge into receiving marine environment.

The simplified advection diffusion-diffusion equation with variable (depending on the distance from the outfalls) coefficients of turbulent diffusion has been solved for this purpose.
The effects of surcharged manholes on the travel time and dispersion of solutes in sewer systems
Authors: Guymer Ian , O'Brien Rob
Published: May 2018

Previously, the design of sewer systems has been limited to studies of their hydraulic characteristics, in particular the ability of the system to convey the maximum discharge. Greater environmental awareness has necessitated that new designs, and some existing schemes, are assessed to determine the environmental load which the scheme will deliver to any downstream component. This paper describes a laboratory programme which has been designed to elucidate the effects of manholes on the longitudinal dispersion of solutes. A laboratory system is described, which allows in situ measurements to be taken of the concentration of a fluorescent solute tracer, both up- and down-stream of a surcharged manhole junction. Results are presented from a preliminary series of studies undertaken for a single manhole geometry over a range of discharges, with varying levels of surcharge. Results are presented showing the variation of travel time, change in second moment of the distribution and of a dispersion factor with surcharge, assuming a Taylor approach and determining the dispersion factor using a ‘change in moment’ method. The effect of the stored volume within the manhole is clearly evident. The limitations and the applicability of this approach are discussed.
Capturing and releasing settleable solids – the significance of dense undercurrents in combined sewer flows
Authors: Verbanck Michel A.
Published: May 2018

Particulate organic matter concentrations determined at the outlet of a low-sloped combined sewer are observed to increase significantly in the very early stage of storm runoff events. It is found that this is not a result from scouring of actual deposited sediments in the sewer (which are granular), but from the dynamic behaviour of a distinct component of the sewage flow itself. During low flows in dry weather, a part of the coarsest material present in normal sanitary sewage (primarily organic debris such as human and food wastes, of about millimetric size and larger) settles and leaves the main body of the flow, but does not reach the sewer bottom to deposit there. The lowest part of the flowing sewage acts in this case as a temporary storage of highly polluting matter, as its longitudinal velocity is lower than the one of the remaining flow. An explanation for the building of these ‘dense undercurrents’ is formulated, based on a difference between free settling in the main body of flow and hindered settling near the bottom. Although this still merits further confirmation, it is likely that the process which maintains coarse solids in suspension in the undercurrent is a lift force induced by shear in the near-bed zone.

The collapse of the undercurrent and the subsequent release of polluting material into the whole water column has been observed in the considered sewer to occur when bed shear stress exceeds about 1.1-1.2 N/m2. This low value can explain flushing effects occurring frequently during rainy period, or even at peak dry weather flows. On the basis of properties illustrated in this study, a number of management options can be considered for revised day-to-day operation of low-sloped interceptor sewers where dense undercurrents are likely to develop.
On the kinetics of nitrification-denitrification biological excess phosphorus removal processes
Authors: Arsov R. , Ribarova I. , Topalova Y. , Mihailov G.
Published: May 2018

Eutrophication is one of the major environmental problems of the Black Sea, resulting in uncontrolled enrichment of the sea water with nutrients – nitrogen and phosphorus. This autoaccelerating process can be stopped effectively by implementation of advanced technologies for wastewater nutrients removal, some aspects of which are objectives of this paper. The University of Cape Town (UCT) technological scheme was examined in series of experiments with different technological parameters. Completely mixed continuous flow automated reactors were used. The experiments were conducted with real municipal wastewater. The mass fractions and the relevant substrates, utilized by three essential groups of microorganisms (poly-P and nonpoly-P heterotrophic and nitrifying bacteria) were determined. As a result of the derived relationships, based on the simplified procedure developed, the kinetic parameters of these groups of microorganisms were determined, as a base for nitrification-denitrification biological excess phosphorus removal system design and simulation.
Upgrading of a small wastewater treatment plant: design and operation aspects
Authors: Hatziconstantinou G. J. , Kalergis C. M. , Grivas A. P.
Published: May 2018

This paper presents the case of a small wastewater treatment plant taken out of service due to insufficient design and equipment installed. Design assumptions and decisions made for plant restoration based on treatment requirements are outlined and plant operation aspects regarding revealed wastewater characteristics, process efficiency, sludge settling behaviour and equipment control, are discussed. The importance of wastewater characterization as a necessary procedure prior to plant design and construction, is stressed and the feasibility of nutrient removal in small wastewater treatment plants under minimum supervision, is assessed. A simplified mathematical model, as a useful tool to operators, for plant performance evaluation and prediction, is presented.
Organic compounds at different stages of a refinery wastewater treatment plant
Authors: Gulyas Holger , Reich Margrit
Published: May 2018

In this study organic compounds in dichloromethane extracts of wastewater samples taken at different stages of a mineral oil refinery wastewater treatment plant were analysed by gas chromatography using a mass selective detector. Main constituents of the raw wastewater were n-alkanes, iso-alkanes, cyclic alkanes, aromatic hydrocarbons, and phenols. Also small concentrations of some heterocycles were detected. The data suggest that flotation is a suitable pre-treatment step for removing the major part of alkanes, aromatics and phenols. The flotation protects biological stages against inhibitory effects of e.g. phenols. The activated sludge process removes most of the remaining gas chromatographically detectable organics and only three iso-alkanes, traces of carboxylic acids and – exhibiting the highest concentration – acetic acid 2-(2-butoxyethoxy)-ethyl ester were found in the clarified effluent of the activated sludge process. These detected substances cannot explain the relatively high COD of the sedimentation effluent and it is assumed that the main part of the COD of the biologically treated mineral oil refinery wastewater is represented by humic material formed in the activated sludge process. As in the raw wastewater also volatile aromatics (e.g. toluene, xylenes, ethylbenzene) were detected it is recommended to collect and treat the off-gas of flotation units applied for petrochemical wastewater purification.
Septicity in sewers: causes, consequences and containment
Authors: Boon Arthur G.
Published: May 2018

This paper reviews research and development on the causes, consequences and methods of controlling septicity in sewers. It draws on information given in 57 published papers on the subject. Explanations are given on the deviation of equations used to predict critical conditions in sewers and rising mains. The consequences of septicity, including toxicity, corrosion and odour nuisance, are described and discussed. Prevention is always recommended over cure, but where this cannot be achieved the methods of controlling septicity generally rely on maintaining an adequate supply of oxygen (dissolved or chemically available) to oxidize previously formed sulphide. Other options to cure the effects of septicity include minimizing the emission of hydrogen sulphide into the atmosphere, deodorizing vented air, and the use of protective coatings or corrosion-resistant pipes.
Mathematical modelling of sulphides and hydrogen sulphide gas build-up in the Costa do Estoril sewerage system
Authors: Matos J. S. , Aires C. M.
Published: May 2018

The Costa do Estoril sewerage system is one of the largest separate systems ever built in Portugal. Because of the quality of the environment in the region and the high level of touristic use, special care was given, in its design, to sulphide calculations.

This paper describes the application to the Costa do Estoril sewerage system of an integrated computer model for forecasting sulphides and hydrogen sulphide gas build-up along sewer atmospheres. The empirical sulphide prediction equations have been calibrated with experimental results obtained under a research project carried out in a gravity tributary and in a rising main located near the Costa do Estoril zone. The hydrogen sulphide gas concentrations along the main trunk line have been predicted according to an mathematical model described by Matos and Sousa.

The results of the model have been considered to be adequate for identifying critical reaches and for predicting the effects of corrective and preventive measures on the overall behaviour of the system.
Relation between the structure of an aerobic biofilm and transport phenomena
Authors: de Beer Dirk , Stoodley Paul
Published: May 2018

An aerobic biofilm was characterized using confocal scanning laser microscopy (CSLM), O2 micro-electrodes, particle tracking and microinjection of fluorescent dyes. The biofilms were found to consist of microbial clusters of cells and Extra-cellular Polymeric Substance (EPS) separated by interstitial voids. The cell clusters were ca 300 μm and the voids were ca 100 μm wide. The voids were open channels connected with the bulk fluid. Fluorescein micro-injection showed that liquid could flow through the voids, but was always stagnant in the cell clusters. Consequently, in voids both diffusion and convection may contribute to mass transfer, while in cell clusters transport is determined by diffusion only. Particle tracking with CSLM showed that flow velocity inside the biofilm was proportional to the bulk flow velocity. The importance of convective mass transport in biofilms was demonstrated by oxygen distribution measurements. At high flow velocities of the bulk liquid, the mass boundary layer followed the irregular biofilm surface. At lower velocities the mass boundary layer was parallel to the substratum. Mass transfer from voids to cell clusters increased with flow velocity, as result from vonvective mass transport from the bulk to the voids. Convective transport was insignificant at low flow velocities, but at high flow velocities it increased the total mass transport by 200-250%. The local diffusion coefficients in biofilms were measured using microinjection of fluorescent dyes and quantitative analysis of the subsequent plume formation using CSLM. The diffusion coefficient of small, non-binding molecules in cell clusters is close to that in water. Very large molecules were impeded in their diffusion through the biofilm matrix. It was calculated that the cell cluster matrix had the characteristics of a gel network with pore diameters of 80 nm.
Effects of area and time horizons in comprehensive and integrated water resources management
Authors: Yevjevich Vujica
Published: May 2018

Four concepts are defined for water resources systems: comprehensive management, integrated management, area horizons and time horizons. Five phases in development of water resources are: initial phase of modest demand (water transferred only in space), intense developmental phase (water transferred in both space and time), water transfer among the adjacent areas, water re-allocation phase, and the phase of developmental maturity. The comprehensive management incorporates the external social, economic, environmental, financial and political influences by specifying the goals to be attained. The concept of water resources supersystem, as a set of dependent systems, is introduced. The integrating management means incorporating a set of purposes as the internal aspects of resource management. They are realized by economic, social, environmental and other optimizations of the well defined objective functions. Objectives are fulfilled by matching supply and demand. Thus a triad of goals-purposes-objectives is defined. Three basic area horizons for a system are: the main system area, the adjacent physically-interacting area, and the surrounding areas interacting through water or power demand. Five time horizons of effects on systems are: period of economic life, period of physical life, horizon of obsolescence, period of full allocation of available water, and period during which significant climatic changes have occurred.
Sorption sites in biofilms
Authors: Flemming Hans-Curt
Published: May 2018

The distribution of pollutants in water is strongly dependent on the processes at the solid-liquid interface, such as soprtion. The solid phase is represented by many different materials, mostly minerals but also metals and organics. In technical and natural water systems, biofilms occur to a greater or lesser extent. They will cover the underlying material (substratum) at least partially and represent a gel-type layer, mainly consisting of extracellular polymeric substances (EPS), formed by biofilm organisms, in which the latter are embedded. Thus, the sorption properties of biofilms will significantly determine the overall process. This effect may have been almost completely overseen, e.g., in the assessment of the fate of pollutants in waters, in the process of sediment diagenesis, and in chemical sorption studies. Sorption data can differ considerably between sterile and non-sterile assays; this aspect puts in question many results gained in biologically uncharacterized systems. Sorption in biofilms can be undesired, if pollutants accumulate in biomass such as activated sludge. The same effect, however, can be biotechnologically exploited, e.g. in biosorption reactors.

Biofilms can sorb water, inorganic and organic solutes and particles. As sorption sites can serve: EPS, cell walls, cell membranes and cell cytoplasm. These sites display different sorption preferences, capacities and properties. The situation becomes even more complex as biofilms may respond physiologically to sorbed substances. For example: the uptake of toluene can lead to the formation of uronic acids in the EPS and, thus, to an increased sorption capacity for cations.

When decomposing, biofilms will release sorbed substances. This can be of significance if trickling deposition of sewage water on soil is finished. The biomass will decompose, sorbed pollutants are remobilized and can contaminate the ground water if not retained abiotically by other soil components.

A substantial research demand is identified regarding the following questions: (i) what do biofilms sorb; (ii) what are the binding sites; (iii) what are the sorption mechanisms and capacity, and (iv) what is the remobilization potential?
Biofilm structures
Authors: van Loosdrecht M. C. M. , Eikelboom D. , Gjaltema A. , Mulder A. , Tijhuis L. , Heijnen J. J.
Published: May 2018

The influences of reactor conditions (substrate loading rate and shear) and microbial characteristics (yield and growth rate) on the structure of biofilms is discussed. Based on research on the formation of biofilms in Biofilm Airlift Suspension (BAS) reactors a hypothesis is postulated that the ratio between biofilm surface loading and shear rate determines the biofilm structure. When shear forces are relatively high only a patchy biofilm will develop, whereas at low shear rates the biofilm becomes highly heterogeneous with many pores and protuberances. In case of a right balance smooth and stable biofilms can be obtained. A hypothesis for the evolution of biofilm structures as a function of process conditions is formulated.
New experimental findings and biofilm modelling concepts
Authors: Wanner Oskar
Published: May 2018

About ten years ago a mathematical model was presented which describes the spatial distribution and development in time of microbial species in mixed-culture biofilms. The model was based on the continuum approach and was one-dimensional in space. These two concepts still are the basis of practically all biofilm models used today. On the experimental side some remarkable new findings have been made in the past years: transport of dissolved components in the biofilm is not always due to molecular diffusion only, transport of particulate components can not be exclusively related to the net growth rates of the microbial species in the biofilm, the liquid phase volume fraction (porosity) in the biofilm is not a constant, and simultaneous attachment and detachment of cells and particles at the biofilm surface is an essential process. These experimental findings had a significant impact on our notion of biofilm systems and called for the integration of new processes in the original mixed-culture biofilm model. The new processes can reproduce most of the experimental observations, however, they are described by empirical mathematical functions. Their mechanisms and significance for biofilm behavior have not been completely elucidated yet. Thus, the extended mixed-culture biofilm model represents primarily a tool for research on biofilm processes.
Extraction of extracellular polymeric substances (EPS) from biofilms using a cation exchange resin
Authors: Jahn A. , Nielsen P. H.
Published: May 2018

A cation exchange resin was used to extract water soluble EPS material from different sewer biofilms and a biofilm monoculture of P.putida. The extraction method seemed to be especially suitable for extracting humic substances and proteins from biofilms but also carbohydrate could be extracted, depending on the nature of the sample. Extraction conditions must be well defined because the extraction efficiency was dependent on stirring intensity, amount of cation exchange resin and extraction time. Up to 20% of the total biofilm protein was found in the DOWEX-extractable fraction. No significant cell-lysis up to 2 hours of extraction time could be detected by acridine orange (AO) direct counts. The same was true when applying the extraction method to a batch culture of P.putida. However, the number of viable cells in the batch culture as recorded by plate count technique was reduced to 28 % after 30 min of extraction. In conclusion, proteins and humic substances can be extracted from biofilm EPS in considerable amounts and should be investigated more in detail when analysing the properties of the EPS matrix of a biofilm.
Degradation of chlorophenols by biofilms on semi-permeable membranes in two types of fixed bed reactors
Authors: Wobus A. , Ulrich S. , Röske I.
Published: May 2018

Two identical fixed bed reactors containing gas-permeable tubings as carrier material were compared for the elimination of chlorophenols. Under plug flow conditions, the continuous flow operation resulted in a stratification of biomass due to concentration gradients. To achieve a homogeneous colonization, the sequencing batch mode has been applicated to one biofilm reactor (Sequencing Batch Biofilm Reactor - SBBR). Concentration gradients after filling, probably due to sorption phenomena, caused an uneven distribution of biomass in the SBBR. However, the colonization of the SBBR was more homogeneous as compared to the continuously operated reactor (CFBR). As to the elimination of a trichlorophenol (2,4,5-trichlorophenol - TCP), no significant differences between the SBBR and the CFBR were observed with regard to its sensitivity against load surges. It is to be supposed that sorption to the biofilm was included in the elimination of chlorophenols. A higher diversity of protozoan community and meiofauna is obviously to be attributed to continuous flow.
Restoration of the broads-area Alde Feanen, The Netherlands: measures and results
Authors: Claassen T. H. L. , Maasdam R.
Published: May 2018

The Alde Feanen (2500 ha) is a relatively large nature reserve in the lower middle part of the province of Friesland, The Netherlands. The area consists of grass- and woodland, peat-diggings, and broads and open basin water. The nature-function -with specific ecological goals- is the main target for the water management. However, the water quality in the various waters did not agree with the formulated standards for this area. In the period 1990–1993 many restoration measures have been realised, namely isolation from the basin water, dredging, biomanipulation, and hydrological re-arrangement. A monitoring program, started at the end of 1987, follows the effects of the various measures. First results are an improvement of the water quality of hydrological isolation, and of dredging. Biomanipulation gives varying results, depending on the effectivity of the removal of bream. Local factors, such as a colony of cormorants, can nullify restoration measures. In general, water quality is improving, which gives a perspective on the re-introduction of the otter.
Ecological rehabilitation and morphological impact of gravel extraction in the river meuse
Authors: Duizendstra H. D. , Nieuwenhuijzen M. E.
Published: May 2018

For the gravel bed river, the Grensmaas, plans have been made by which extraction of gravel and ecological rehabilitation of the river will be combined. One way to study the morphological changes, the time scale of these changes and the expected ecological rehabilitation is to study gravel bed rivers with approximately the same morphological characteristics as the future Grensmaas. Since scale models in nature of the future Grensmaas do not exist, selection criteria of reference rivers have to be modified. The results of the reference investigation will be different and the interpretation will be much more complicated. An important morphological parameter is the (yearly) sediment transport. A method to measure sediment transport during high discharges is described and tested.
Development and eutrophication: experiences and perspectives
Authors: Lijklema Lambertus
Published: May 2018

Fluxes of nutrients are dominated by agriculture and the flow of agricultural products. Presently nutrients accumulate in the developed world whereas developing countries suffer from nutrient depletion and erosion of their soils. The fast growing population with its expected increase per capita intake of food, to be cultivated on a generally limited area of arable land, will stimulate the application of nutrients in large parts of the developing world. Considering the time-scales of nutrient storage this will eventually lead to similar problems to those experienced in the developed world. Timely intervention can mitigate future environmental degradation, but it requires foresight without complete fixation with today's problems.
River water quality study in the vicinity of Jakarta
Authors: Palupi K. , Sumengen S. , Inswiasri S. , Agustina L. , Nunik S. A. , Sunarya W. , Quraisyn A.
Published: May 2018

Results are presented from a field study performed on the Ciliwung, Sunter and Krukut Rivers in Jakarta. The rivers are used as raw water sources for Jakarta municipal water supply systems, yet the rivers are used as receiving bodies by some inhabitants and industries. In this study, the quality of the rivers' water was determined using a Water Quality Index (WQI) which is scaled from zero to a hundred. The higher number of the WQI indicates, the better quality of the river water. Among the results presented are the WQI and heavy metals concentration. River water sampled from upstream of Jakarta, intake areas, and estuary areas were tested during the dry and rainy seasons. In the dry season the WQIs of Ciliwung, Sunter and Krukut Rivers ranged between 21-42, 20-29 and 21-38, respectively. In the rainy season the WQIs of Ciliwung, Sunter and Krukut Rivers ranged between 34-47, 32-50, and 34-47, respectively. The level of heavy metals did not exceed current Indonesian Standards. It was concluded that the overall water quality of the Ciliwung, Sunter, and Krukut Rivers was between very poor and poor, and the rivers were polluted by Cu, Pb, Cd, Zn and Hg.
Influence of changing microbial sludge characteristics on the degradation of an inhibitory compound
Authors: Mungkarndee P. , Bhamidimarri S. M. Rao , Mawson A. J. , Chong R.
Published: May 2018

The biodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by a mixed microbial consortium enriched from soil was investigated. The specific oxygen uptake rate (SOUR) as a measure of biomass was found to be inappropriate as the characteristics and composition of the mixed culture were found to change significantly as the operating conditions changed. Both SOUR and biomass measurements revealed an expected substrate inhibition pattern up to around 1000 mg/L 2,4-D in batch incubation trials. The maximum growth rate was recorded at a substrate concentration of around 300 mg/L when the biomass was measured by gravimetrically, although maximum oxygen uptake activity was at a substrate concentration of 500 mg/L. The continuous experiments showed that 2,4-D can be degraded at inlet concentrations of up to 6362 mg/L resulting in >99.5% degradation. The flocculation characteristics of the biomass were found to change as the substrate concentration changed and a microscopic examination confirmed that the changes in SOUR and specific substrate utilisation rate (SSUR) in the continuous system were due to changes in microbial culture characteristics.
A bench-scale study on chromium recovery from tanning wastewater
Authors: Panswad Thongchai , Chavalparit Orathai , Sucharittham Yaowanud , Charoenwisedsin Sasithorn
Published: May 2018

In order to recover chromium, wastewaters from the chrome-tanning process in two Thai tanneries were coagulated with magnesium oxide or sodium carbonate at various dosages. Different types of polymer were also tried to improve the settleability of the chromium sludge which, in turn, was redissolved by sulfuric acid. The produced chromium III sulfate (Cr2(SO4)3) solution was sufficiently concentrated for direct reuse in the tanning step. The settling pattern of the chromium sludge was also observed and optimum sedimentation periods ranging from 1 to 17 hours were suggested. Under no tanning-additive (a chemical to improve chromium sorption onto hides) circumstances, the discharged wastewater contained 5-11 g Cr2O3/l and the most promising coagulant was MgO at a dose of twice the stoichiometric value and an optimum pH of 7-8. The resulting chromium precipitate or sludge was quite dense (21% solids) and possessed a good settling velocity (234 mm/h), making the decantation process very easy, whereas the corresponding acid requirement for the dissolution process was 1.5 times the stoichiometric value. On the other hand, in the tanning-additive situation, the chromium concentration in the drain was reduced to 3-6 g Cr2O3/l. Magnesium oxide was shown to be also the best coagulant but the dose was two times higher than that of the first circumstance, ie., four times that of stoichiometric requirement.
Survey on filamentous micro-organisms in activated sludge processes in Bangkok, Thailand
Authors: Mino Takashi
Published: May 2018

A survey to investigate the proliferation of filamentous micro-organisms, which cause filamentous bulking in activated sludge wastewater treatment processes, was conducted for the first time in the tropical zone. Activated sludge samples were collected from six wastewater treatment processes in Bangkok City, Thailand. The activated sludge plants investigated include those for 1) an industrial wastewater from an industrial estate, 2) a domestic wastewater from apartment houses, 3) a brewery wastewater, 4) a hotel wastewater, 5) a textile industry wastewater and 6) a milk processing wastewater. The identification of proliferating filamentous micro-organisms in the samples was attempted. Type 021N was exclusively dominant in the milk processing wastewater treatment plant. The characteristics of the 021N present were different from “typical” 021N. The most proliferating filament in the textile wastewater treatment plant was suspected to be Nostocoida limicola. There was a predominant filament in the brewery wastewater treatment plant, which is suspected to be a new type. Other major filaments proliferating include Eikelboom Type 021N, 1701, 0041 and 0092. Nocardia was also found in a few plants.
Fish farming in Denmark: environmental impact of regulative legislation
Authors: Iversen T. M.
Published: May 2018

The main environmental problems associated with fish farming in Denmark are attributable to the dam, the “dead reach” and nutrient and organic matter discharge. The environmental regulation of fish farming in Denmark started with the Environmental Protection Act of 1974, the Statutory Order of 1985 forbidding wet feed, and the Action Plan on the Aquatic Environment of 1987. In the case of freshwater fish farms, the latter was implemented through the measures stipulated in the 1989 Statutory Order on Fish Farms.

The impact of Danish legislative measures to reduce and regulate the environmental effects of freshwater fish farms can be summarized as follows:

- the number of fish farms has been reduced from about 800 in 1974 to about 500 at present;

- production has tripled since 1974 and has been stable since 1989;

- a change from wet to dry feed has reduced the environmental impact of the farms;

- the national goals of the Action Plan on the Aquatic Environment of 1987 for reducing fish farm discharges of organic matter, nitrogen and phosphorus have been fulfilled.

The main remaining problems are that:

- the local impact of fish farms on downstream stream quality is still much too high in about 15% of cases;

- the problem of the passage of migrating invertebrates and fish is still unsolved at some farms;

- the problems posed by “dead reaches” are still unsolved.

It is concluded that sustainable fish farming is possible in Denmark, but with the present technology production will have to be significantly reduced.
A hydroacoustic waste feed controller for tank systems
Authors: Summerfelt Steven T. , Holland Kyle H. , Hankins Joseph A. , Durant Martin D.
Published: May 2018

The objective of this work was to develop a commercially viable method to reduce waste feed and thus improve production efficiency and reduce discharge of solids and nutrients within tank based aquaculture systems. We developed and custom fabricated a feeding controller which uses ultrasound to detect uneaten feed and controls feeding events based upon appetite satiation as measured by the quantity of waste feed detected. During feeding, the developed device functions as a combination ultrasonic detector, feedback controller, and interval timer. The device functions as a feedback controller by ultrasonically sampling the stock tank effluent and turning off the feeder when an excessive amount of feed enters the effluent flow. After feeding has been inactivated, the ultrasonic waste feed controller operates as an interval timer and provides a user selected delay between feedings. A custom hydroacoustic probe assembly was developed to detect uneaten feed.

The controller can be calibrated by adjusting the transducer signal gain to detect signals resulting from feed pellets, while reducing signals resulting from faeces. The controller has an adjustable set-point for deactivating the feeder circuit based upon the number of feed pellets detected by the transducer and a programmable delay time interval (from 5 to 160 min) to set the time between feedings. The controller also has an adjustable sampling rate for detection at different pipe velocities and an adjustable observation volume for use in standard 2, 3, 4 and 6 inch diameter effluent pipes.

The cost in materials and labour to produce this waste feed controller was estimated at around $100 (U.S.).
Wastewater management in a dairy farm
Authors: Hamoda Mohamed F. , Al-Awadi Saed M.
Published: May 2018

Field sampling and laboratory experimentation were conducted on wastewater effluent generated at a dairy farm in order to characterise the wastewater, evaluate existing primary treatment facilities, and examine an appropriate wastewater treatment system to produce good quality effluents. It has been found that the farm contributes effluents containing considerable loads of organics, solids and nutrient pollutants. Existing treatment facilities which are limited to batch-operated primary settling tanks, are not capable of producing good quality effluent. Experimentation on an aerobic, suspended growth, biological system using sequencing batch reactors (SBR) indicated that the pollutant loads in the primary-treated effluent could be substantially reduced. The study showed that a wastewater treatment system involving primary settling tanks combined with additional aerobic biological treatment is capable of removing about 94% COD and 96% SS from the farm effluents. This system could be easily integrated and coordinated with existing facilities. A wastewater management scheme has been proposed to include waste minimisation, waste treatment and effluent reuse in irrigation.
2-methylisoborneol degradation by the cam operon from pseudomonas putida PpG1
Authors: Oikawa E. , Shimizu A. , Ishibashi Y.
Published: May 2018

The purpose of this study was to determine whether 2-methylisoborneol (MIB) degradation is coded on the chromosomal DNA or on the plasmid DNA. Result of these studies indicated the genes in Pseudomonas spp. responsible for this degradation may be located in the chromosomal DNA. Moreover, since the structure of MIB is similar to camphor, the cam operon which can decompose camphor was tested for decomposition of MIB. The cam operon consists of five parts; camD,C,A,B and camR. Each gene plays a different note; camR as it is a repressor of expression. The whole cam operon could decompose MIB by much the same pathway as camphor. Overexpressed recombinant plasmids were also constructed to reduce MIB, which was effectively degraded by deleted camR strains.
The contribution of sedimentation of algal cell to the downstream levels of musty odor
Authors: Hoson T. , Hayashi S. , Hattori K.
Published: May 2018

In Lake Biwa, there are two peaks of 2-methylisoborneol (MIB) production, each of which is due to the different MIB producing algae, Phormidium and Oscillatoria. The former grows in early summer, whereas the latter grows in late summer. Levels of MIB were determined for water samples collected from Lake Biwa and the lower sampling site of Murano Water Treatment Plant's intake on Yodo River. MIB concentrations detected at the lower site differed between the two odor seasons. In the first episode due to growth of Phormidium, MIB level at the lower site was almost the same as that in the lake, whereas it was clearly lower than that of the lake in the second episode caused by Oscillatoria. No differences in flow ratio of the lake effluent to that of Yodo River were detected between the two odor seasons. Thus, the difference in MIB concentration between the lake and the lower site in the second episode may be caused by a decrease in cell-associated MIB due to the high sinking rate of Oscillatoria. The sinking rate ofOscillatoria trichome was twenty times higher than that of Phormidium.
Organochlorine pesticides and heavy metals in fish reared in treated sewage effluents and fish grown in farms using polluted surface waters in Egypt
Authors: Shereif M. M. , Mancy K. H.
Published: May 2018

In a full scale experimental study, raw sewage from the City of Suez, Egypt was treated using a stabilization pond system. Fish grown in the treated sewage was compared with fish from one of the farms which receives contaminated surface water in Lake Manzala. Organochlorine pesticides were detected at higher levels in fish from Lake Manzala farms, than in fish reared in the treated sewage of the City of Suez. The highest levels were due to p,p'DDT and its metabolites, followed by Lindane and HCB. Furthermore, the concentrations of Pb and Cd were significantly higher in the fish from the Lake Manzala farm, than in the fish from Suez. In addition, the concentration levels of Pb and Cd in the fish from Lake Manzala exceeded the international contaminant limits for human consumption. In general, fish grown in this region have high levels of pesticides and metal contaminants. It is interesting to note that in spite of possible cultural bias against fish grown in treated sewage effluents, have lower levels of toxic chemicals than some of the marketed fish, harvested from polluted surface waters.
Studies on a biological filter for musty odor removal in drinking water treatment processes
Authors: Terauchi N. , Ohtani T. , Yamanaka K. , Tsuji T. , Sudou T. , Ito K.
Published: May 2018

Pilot plant studies on biological filter treatment for musty odor in drinking water were conducted. The plant was operated for 2 years at a filtration rate of 170 m/d and the surface water of Lake Biwa was employed as an influent. 2-Methylisoborneol (MIB) produced by Oscillatoria tenuis was the main cause of the musty odor. In the season of natural musty odor generation, total MIB concentration and the insoluble to total MIB concentration ratio in the influent varied to a large extent, but removal efficiencies of MIB by the filter were about 60 to 80%. Out of the season of natural musty odor, reagent MIB was added to the influent and the removal efficiencies obtained were about 70 to 80%. In addition to MIB, color, turbidity, Fe, Mn, NH4-N and KMnO4 consumption value were also effectively removed by the biological filter. Using the effluent from the filter, jar tests for powdered activated carbon treatment and coagulation-sedimentation treatment were conducted. From the results, the biological filter treatment seemed to effectively decrease the powdered activated carbon consumption even in cases where powdered activated carbon additions might be needed. No ill effect on coagulation-sedimentation treatment was seen and the required coagulant dosage was less in water after biological filter treatment.
Energetics of advanced integrated wastewater pond systems
Authors: Green F. B. , Lundquist T. J. , Oswald W. J.
Published: May 2018

An energy balance is presented for a second generation Advanced Integrated Wastewater Pond System (AIWPS) prototype at the University of California, Berkeley, Environmental Engineering and Health Sciences Laboratory in Richmond, California. Modifications were made to the existing 1.8 ML facultative pond in order to further optimize methane fermentation and to demonstrate the recovery of methane using a submerged gas collector. Methane production rates were determined over a range of in-pond digester loadings and temperatures. The feasibility of submerged gas collection was proven, and the advantages of in-pond digestion in terms of BOD5 and VSS removal as well as biogas scrubbing were quantified. Biogas methane concentrations increased by more than 50% as the biogas emerged through the overlying water column and most of the carbon dioxide fraction was utilized by microalgae. Electrical power requirements for mixing two 0.1 hectare algal High Rate Ponds (HRPs) were measured over a range of channel depths and velocities, and electrical power requirements for daily recirculation pumping were also measured. Oxygenation and total treatment energy requirements for the second generation AIWPS prototype at Richmond were compared with oxygenation and total treatment energy requirements for the first generation AIWPS at St. Helena, California and for two mechanical wastewater treatment plants of comparable capacity and effluent quality at Pinole and Brentwood, California. Using preliminary methane production and recovery rates achieved at Richmond, the cogeneration potential was estimated and projected for larger second generation AIWPSs of 2 MLD and 200 MLD capacities. By incorporating methane recovery and electrical power generation together with efficient HRP mixing using paddle wheels, full-scale second generation AIWPSs will be able to produce as much energy as they require for primary and secondary treatment. Additional energy would be required to produce a tertiary disinfected effluent suitable for unrestricted reuse in California, including recreational and indirect potable reuse. The additional power requirements for complete algal harvest using dissolved air flotation (DAF) and filtration were estimated for second generation AIWPSs based on data collected at Richmond and Stockton, California, and the additional power requirements for final UV disinfection were estimated.