bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial variations of phytoplankton community structure in a highly eutrophicated coast of the Western Mediterranean Sea
Authors: Torres E. Soler , del Río J. G.
Published: May 2018

Pinedo is a small beach placed at the southern side of Valencia (Eastern Spain). This coastal area has became highly eutrophicated because of the discharge of a large flow of urban wastewaters at the shore line. In order to assess the environmental impact of a new sea outfall and to study the phytoplankton and nutrients dynamics of this eutrophicated system a broad survey was conducted between May 1989 and April 1990. Physical and chemical parameters were measured through a transect laying between the wastewater discharge point and the open sea. In this paper we report preliminary results about the variations observed in the phytoplankton community along this sharp environmental gradient. Three main zones with particular phytoplankton structure appear well differentiated. The first is an inshore zone very influenced by continental loadings where brackish and polluted waters were found. Phytoplankton shows relatively low numbers being dominated by Chlorophyceae and a few other eurihaline species. An intermediate zone has salinities close to sea water but nutrient concentrations are high enough to allow maximum development of phytoplankton, which reaches its highest abundance and diversity values. Diatoms, dinoflagellates and some flagellates (Prymnesiophyceae and Cryptophyceae) dominate the eukaryotic community of this zone. Gradual impoverishment of sea water is accompanied by a rapid decrease of phytoplankton biomass, which is reduced to scarce flagellates populations at the open sea stations.
Software sensors based on the grey-box modelling approach
Authors: Carstensen Jacob , Harremoës Poul , Strube Rune
Published: May 2018

In recent years the grey-box modelling approach has been applied to wastewater transportation and treatment. Grey-box models are characterized by the combination of deterministic and stochastic terms to form a model where all the parameters are statistically identifiable from the on-line measurements. With respect to the development of software sensors, the grey-box models possess two important features. Firstly, the on-line measurements can be filtered according to the grey-box model in order to remove noise deriving from the measuring equipment and controlling devices. Secondly, the grey-box models may contain terms which can be estimated on-line by use of the models and measurements. In this paper, it is demonstrated that many storage basins in sewer systems can be used as an on-line flow measurement, provided that the basin is monitored on-line with a level transmitter and that a grey-box model for the specific dynamics is identified. Similarly, an on-line software sensor for detecting the occurrence of backwater phenomena can be developed by comparing the dynamics of a flow measurement with a nearby level measurement. For treatment plants it is found that grey-box models applied to on-line ammonia measurements from the aeration tank of an alternating plant provide information on the incoming ammonia load. It is also shown how measurements of the return sludge concentration from a secondary clarifier can be filtered to minimize the effect of the scraper. Thus, important information can be derived from on-line measurements if the appropriate grey-box model for the specific system is identified.
NH4 automatic analysers for wastewater treatment plant: evaluation test at laboratory and field level
Authors: Wacheux H. , Million J.-L. , Guillo C. , Alves E.
Published: May 2018

Nine NH4 automatic analysers or monitors were tested in June-July 1995 (among them 2 prototypes):

- 5 based on ion electrode; ABB, Applikon, Contronic, Hydro-Environnement, STIP,

- 4 based on colorimetry; Danfoss, Data Link (UV absorption), Meerestechnik, Skalar

Laboratory tests are aimed to determine response time, repeatability, response linearity, short-term stability, influence of various factors on the measurement. The field test relates to real conditions: all the sensors were installed in parallel at the discharge point of a Wastewater treatment plant (WWTP). Recorded outputs were compared with conventional laboratory analysis of average hourly samples.

Response time range from 2 to 21 minutes. Repeatability varies from 1 to 10%, stability from 1 to 17%. Linearity is always good and detection limits (about 0.2 mg/l) do not seem to be critical for use in a WWTP. Among factors of influence, power voltage has limited effect, sample temperature is affecting some monitors, chemical interferents have nearly no effect excepted for one monitor. Field tests have shown that NH4 monitors are still very sensitive and that installation is crucial. Each monitor suffered several failures, some of them required high maintenance and used costly reagents.
Dynamic modelling for operational design of a respirometer
Authors: Giroux É. Y. , Spanjers H. , Patry G. G. , Takács I.
Published: May 2018

The purpose of this paper is to demonstrate how dynamic modelling and simulation can effectively be used to assess the operation of an on-site respirometer. A dynamic model of the respirometer was developed using the General Purpose Simulator (GPS-X). The approach is appropriate for operational design of the respirometer in allowing the user to experiment with the instrument, through simulation, before it is actually operated. The model was able to replicate the operational modes of the respirometer. The dynamic model was found to be particularly useful in assessing difficulties associated with multiple respiration rate calculations, the effect of temperature on the respiration rate, and the detection of the endogenous respiration rate.
Uncertainty and transient contamination of river water by agricultural use of industrial products: release and run-off of hazardous chemicals from agricultural plastic film
Authors: Okada Mitsumasa , Cho Kyung Jin , Mukai Tetsuo , Takimoto Kazuto
Published: May 2018

An organophosphoric acid triester, tricresyl phosphate (TCP), was detected in the Kurose river, Hiroshima, Japan. The concentration was low during dry weather and increased after rainy days suggesting typical contamination originating from non-point sources. However, precipitation did not always increase the concentration of TCP in the river. Some rainevents increased TCP in river water and bottom sediments, whereas others did not. To clarify the uncertainty and mechanism of the transient contamination, we carried out an intensive survey both in the river and catchment area. Small amounts of TCP were detected both in domestic and industrial waste waters. Also, urban run-off, dry and wet precipitation and other possible non-point sources did not contain significant amounts of TCP. Occasionally, we could detect high concentration of TCP in agricultural run-off from greenhouses. Most greenhouses in the region are covered by plastic films for insulation. Although TCP used in many industrial products in the basin, it seemed most likely that the major sources of TCP were plastic films for agricultural purposes. Release of TCP from an agricultural plastic film by rainwater was confirmed. However, the release did not always reach the river or its tributaries. Most of the released TCP seemed to be transported to the soil and was decomposed in the soil. This mean that run-off of TCP from the field was not associated with rainfall. Only a part of the TCP seemed to be released from the film to be transported to soil and finally to the river with surface run-off of soils.
Full-scale on-line assessment of toxic wastewaters causing change in biodegradation model structure and parameters
Authors: Vanrolleghem Peter A. , Kong Zaide , Coen Filip
Published: May 2018

Detecting wastewater toxicity in due time is essential for protection of a sewage works and the receiving waters. A respirometric method is presented that performs short batch experiments, so-called In-Sensor-Experiments for toxicity detection. Two types of wastewater samples can be added to the reactor in the device: either the potentially toxic wastewater entering the plant, or, a defined mixture of acetate and ammonia. From the latter experiments models are identified that describe the heterotrophic and autotrophic activity of the sludge. Since these ‘calibration’ experiments are alternated with experiments in which wastewater is injected, the effect of the wastewater on the sludge can be quantified unequivocally.

Full-scale toxicity detection (and the corresponding effluent quality) results are reported for a plant treating a mixture of hospital and municipal wastewaters. The respirometer was installed at the influent line of the plant. It was evaluated during a 6-month period for its on-line toxicity detection capacity. Both deliberate and accidental intoxications were recorded and compared with off-line toxicity measurements. Inhibitory wastewaters affected the nitrification activity of the sludge. This was confirmed by the concomitant increase in NH4+ discharge of the treatment plant. To evaluate the efficiency of control actions, the deliberate addition of toxicant was interrupted at the time a toxicity alarm was triggered by the respirometer. It was observed that plant performance then remained unaffected for all monitored criteria.
An evaluation of the efficiency of the combined sewer – wastewater treatment system under transient conditions
Authors: Bauwens W. , Vanrolleghem P. , Smeets M.
Published: May 2018

The paper considers the efficiency of alternative sewer and wastewater treatment plant management schemes with respect to the effluents to the receiving waters. The input time series for the flows and concentrations at the CSO structures and at the treatment plant intake are obtained through a continuous sewer simulation model. The wastewater treatment plant model is based on a structured dynamic model describing COD removal and final settling. Special emphasis is put on the sludge inventory of the plant since this is considered to be the main problem area under storm conditions. The methodology is illustrated on the combined sewer network of Brussels. Scenarios without and with CSO control measures in the sewer are considered. At the treatment plant, the simulation study evaluates the effect of potential control strategies such as ratio control of the RAS, step feed and retention of first flush in a storm tank.
A demonstration of the benefits of integrated wastewater planning for controlling transient pollution
Authors: Crabtree B. , Earp W. , Whalley P.
Published: May 2018

The Urban Pollution Management (UPM) Research Programme has been the UK Water Industry's response to the need to limit the risk of transient pollution of receiving waters resulting from intermittent discharges, such as combined sewer overflows. Demonstrating that the UPM tools, such as MOSQITO, STOAT and MIKE 11, can be used to produce cost-effective and reliable solutions to practical problems is considered to be a major element in promoting the benefits of the UPM Procedure approach by eliminating the uncertainty of water quality impact associated with more traditional approaches. A demonstration of the full UPM Procedure for inland situations has been carried out in the city of Derby, in the UK, where high levels of investment are planned for both sewerage and sewage treatment.

Detailed simulation models were calibrated and verified and then used with the simplified pollution modelling tool, SIMPOL, to evaluate the integrated environmental impact of a possible sewerage upgrading option. The results indicated that this option would meet wet-weather water quality requirements at a reduced cost compared to alternatives derived from traditional planning procedures which had a high degree of uncertainty in meeting water quality objectives.
Reduction of operational costs by planned interruptions of aeration in activated sludge plants
Authors: Neiva Manoel Reis , Galdino Laurindo Alves , Catunda Paula Frassinetti Cavalcanti , van Haandel Adrianus
Published: May 2018

A full scale investigation was carried out at the CETREL activated sludge plant to evaluate the technical feasibility of operational cost reduction by planned interruptions of aeration during the daily periods of three hours of high tariff, imposed by the power supply company. It was experimentally established that the daily interruptions did not affect adversely the effluent quality and that sludge activity as well as the settleability remained unaltered. On the other hand the reduction of energy consumption during the high tariff period generated a decrease of operational costs of more than US$ 400.000 per year. Because of the fact that interruptions of aeration in the activated sludge process was shown to be economically feasible, CETREL was in a position of negotiating a more favourable contract with the power supply company, whereby a lower price for power during off peak hours was obtained in exchange for low consumption during the high tariff hours of peak demand.
Institutional developments, standards and river quality: a UK history and some lessons for industrialising countries
Authors: Johnstone D. W. M. , Horan N. J.
Published: May 2018

From the middle ages until the early part of the nineteenth century the streets of European cities were foul with excrement and filth to the extent that aristocrats often held a clove-studded orange to their nostrils in order to tolerate the atmosphere. The introduction in about 1800 of water-carriage systems of sewage disposal merely transferred the filth from the streets to the rivers. The problem was intensified in Britain by the coming of the Industrial Revolution and establishment of factories on the banks of the rivers where water was freely available for power, process manufacturing and the disposal of effluents. As a consequence the quality of most rivers deteriorated to the extent that they were unable to support fish life and in many cases were little more than open sewers. This was followed by a period of slow recovery, such that today most of these rivers have been cleaned with many having good fish stocks and some even supporting salmon.

This recovery has not been easy nor has it been cheap. It has been based on the application of good engineering supported by the passing and enforcement of necessary legislation and the development of suitable institutional capacity to finance, design, construct, maintain and operate the required sewerage and sewage treatment systems. Such institutional and technical systems not only include the disposal of domestic sewage but also provisions for the treatment and disposal of industrial wastewaters and for the integrated management of river systems. Over the years a number of institutional arrangements and models have been tried, some successful other less so. Although there is no universally applicable approach to improving the aquatic environment, many of the experiences encountered by the so-called developed world can be learned by developing nations currently attempting to rectify their own aquatic pollution problems. Some of these lessons have already been discussed by the authors including some dangers of copying standards from the developed world.

The objective of this paper is to trace the steps taken over many years in the UK to develop methods and systems to protect and preserve the aquatic environment and from the lessons learned to highlight what is considered to be an appropriate and sustainable approach for industrialising nations. Such an approach involves setting of realistic and attainable standards, providing appropriate and affordable treatment to meet these standards, establishment of the necessary regulatory framework to ensure enforcement of the standards and provision of the necessary financial capabilities to guarantee successful and continued operation of treatment facilities.
Screening for non-regulated organic compounds in municipal wastewater in Göteborg, Sweden
Authors: Paxéus Nicklas , Schröder Horst Friedrich
Published: May 2018

Organic compounds from influent and effluent wastewater were concentrated on C18 bonded phase cartridges and sequentially eluted with organic solvents of different polarity. About 80% of the toxicity (Microtox) arised from organic matter eluted with ether. Approximately 50% decrease in the overall toxicity of the influent was observed during the treatment process. More than 50 individual compounds were identified in the eluates for both influent and effluent by GC-MS and FIA-MS analysis. Perfume additives to washing powders and cleaning agents and a number of industrial volatile hydrophilic solvents were quantitatively removed by volatilization in the treatment process. Only a partial removal was observed for less volatile compounds (benzophenone, dibutyl formamide, dimethyl quinoline, benzothiazole, phosphate esters) of industrial origin. Substituted phenols, used as antioxidants in both industrial and domestic products were transformed to corresponding -ene-ones in the biological stage of the water treatment process. Polyglycols and polyglycol ether type surfactants are not removed in the activated sludge prosess, only partly transformed to highly persistant acids by oxidation of the terminal hydroxyl function. The treatability in municipal wastewater plants should be paid much more attention when introducing polar non-volatile constituents in new “environmentally friendly” water based products or processes.
Decomposition of 2-chlorophenol in aqueous solution by ultrasound/H2O2 process
Authors: Jih-Gaw Lin , Cheng-Nan Chang , Jer-Ren Wu
Published: May 2018

Several authors have indicated that ultrasound is effective in oxidizing organic contaminants in water and in wastewater either as the sole means of treatment or in combination with ozonation and UV irradiation. In this work we decomposed 2-chlorophenol (2-cp) in aqueous solution with ultrasound and H2O2. The experiment was conducted with a sonicator (Microson XL-2020) operated at 20 kHz. The double amplitude at the tip of the standard horn (12.7 mm) was adjusted to 0, 72 and 120 μm, corresponding to power input 0, 125 and 160 W. The initial concentration of aqueous 2-cp solution was 100 mg/l, treated in the system with 0, 100, 200 and 500 mg/l H2O2 individually. The volume of solution was 1 l in a mixing flask, and was circulated to the sonication cell at the rate 500 mL/min. Oxygen was continuously purged into the flask. The temperature of solution was kept constant at 25°C and pH was controlled at 3, 5, 7, 9 and 11. The results showed the decomposition of 2-cp was effective at increased amplitude of ultrasound and concentration of H2O2, and smaller pH. At reaction duration 360 min, 2-cp decomposition with 500 mg/l H2O2 was found with 57% improvement over the control, i.e. without H2O2 addition. The pH, controlled below the pKa of 2-cp (8.49 at 25°C), had significantly better decomposition of 2-cp than at greater values. The decomposition rate of 100 mg/l 2-cp was 99% at 120 μm double amplitude with H2O2 (200 mg/L) and pH 3, after 360 min of reaction. The removal of total organic carbon was found to be only 63%. From analysis of the experimental results, the data on 2-cp decomposition appeared to follow pseudo-first-order reaction kinetics. The squared correlation coefficient, R2, of the model was greater than 0.9 for various pH values.
The role of the sludge in nitrification inhibition tests
Authors: Winther-Nielsen Margrethe , Jansen Jes la Cour
Published: May 2018

Occurrence of toxic compounds in the influent to a wastewater treatment plant with nitrogen removal may disturb the process tremendously. Nitrification inhibition tests act as an important tool in the efforts of isolating sources of toxic compounds. However, it is necessary to evaluate the test methods and to know the importance of variable parameters. We set up a complete factorial experiment for 6 different types of waste water, 3 concentration levels of waste water and three different sludges. Statistical treatment of the results showed that the percentage inhibition of nitrification was significantly depending on the type of waste water, on the concentration of waste water and on the combination of waste water and sludge. It was apparent that the effect of the waste water is related to the type of compound or waste water that usually occurs in the sludge.

An interlaboratory study was performed with the primary object of establishing repeatability and reproducibility for nitrification tests (modified MINNTOX). From the test of 7 types of waste water, we found repeatability between 1.1 and 6.4% inhibition and reproducibility between 7.9 and 91% inhibition. In general, the reproducibility was better when laboratories used the same type of sludge than when different sludges were used.
Effects of atrazine and alachlor on self-purification processes in receiving streams
Authors: Zagorc-Koncan Jana
Published: May 2018

In recent years many waterways in Slovenia have been subjected to an increased loading with pesticides due to intensification of agriculture. The most widely used herbicides are atrazine and alachlor and they were detected in some rivers and even in ground water. Therefore the effects of atrazine and alachlor on selfpurification processes were investigated. The basic selfpurification processes studied were biodegradation of organic substances and photosynthesis and growth of algae. The inhibiting effect of pesticides on the process of biodegradation of organic pollutants was evaluated by the use of laboratory river model and mathematical modelling. The harmful impacts of pesticides on aquatic autotrophic organisms were assessed by measurement of net assimilation inhibition (24-h acute toxicity test) as well as growth inhibition - chlorophyll- a content (72-h chronic toxicity test) of algae Scenedesmus subspicatus. The results obtained demonstrate that atrazine and alachlor in concentrations found in our rivers have practically no effect on biodegrading heterotrophic organisms, while their adverse effect on algae is quite considerable.
Desorptive behavior of chlorophenols in contaminated soils
Authors: You C. N. , Liu J. C.
Published: May 2018

A study was conducted to assess the desorptive behavior of chlorophenols in contaminated soils. Two soils spiked with three types of chlorophenols, i.e., 2,6-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP), respectively, were examined. The effects of pH, methanol, surfactants, and soil properties were investigated. Amount of three chlorophenols desorbed from soils increased with increasing pH. Deprotonated chlorophenols were more mobile than their conjugate acids. When methanol was added to the soil-water system, the amount of chlorophenols desorbed increased. The desorption of PCP was enhanced in the presence of anionic surfactant, SDS. However, when non-ionic surfactant, TX-100, was present, the desorption of PCP decreased. The effects of pH and surfactants on desorptive behavior of chlorophenols were most significant on PCP. Generally, the amount of chlorophenol adsorption deceased in the order PCP > TCP > DCP. Hydrophobic interaction was found to be the major driving force of adsorption reactions. It was therefore proposed that hydrophobicity of chlorophenols is an important factor controlling their desorptive behavior.
Evaluation of SOS-inducing activity with an O-acetyltransferase-overexpressing strain Salmonella typhimurium NM2009 for municipal river water and the identification of 1-nitropyrene
Authors: Ohe Takeshi
Published: May 2018

Evaluation of SOS-inducing activity of organic extracts from tributaries of the Yodo River in Kyoto was examined with a highly sensitive umu test system using an O -acetyltransferase(O -ATase)-overexpressing strain Salmonella typhimurium NM2009 and an O-ATase-defective strain NM2000. Organic extracts in river water were collected by the XAD-2 resin column method and the blue rayon hanging method at 4 locations throughout the year. Both XAD-2 resin and blue rayon extracts collected at downstream locations from wastewater treatment plants showed higher SOS-inducing activity than those at the upsream location in the absence and the presence of S9 mix with NM2009. It was also shown that the constituents contributing SOS-inducing activity were different between XAD-2 extract and blue rayon extract. No or weak responses of SOS-inducing activity were observed with an O -ATase-defective strain NM2000 among all extracts performed. These results indicate that a highly sensitive umu test using an O-ATase-overexpressing strain and an O-ATase-defective strain proved to be an excellent tool for the monitoring of genotoxicity attributable to trace amounts of genotoxicants such as direct-acting nitroarenes and/or indirect-acting aromatic amines in river water. Further study was made to identify 1-nitropyrene in XAD-2 resin extract from municipal river water.
Monitoring pesticides in surface water using bioassays on XAD-2 preconcentrated samples
Authors: Baun Anders , Nyholm Niels
Published: May 2018

A solid phase extraction (XAD-2) preconcentration procedure has been developed specifically for bioassays of pesticide contaminated water. Adsorption and elution efficiencies of XAD-2 columns were examined using solutions of the 14C-labelled pesticides 2,4 dichlorophenoxy acetic acid (2,4 D), pirimicarb, atrazine and phenmedipham in concentrations 0.4-5.4 μg/l. The adsorption was strongly dependent on pH. Serial preconcentration at two different pH's (pH 2.0 and pH 7.0) implied approximately 85% pesticide recovery in the final extracts. Using spiked surface water, the efficiencies decreased significantly, but efficiencies of about 70% could be accomplished with two consecutive extractions at pH 7.0 and pH 2.0. The toxicity of an atrazine extract (1000 times concentrated from originally 15 μg/l) was similar to that of the pure compound as assessed using a test battery with 3 different species - Selenastrum capricornutum, Daphnia magna, andLemna minor . This result indicates that no modification of toxicity occurs during the preconcentration step. Two water samples with a different degree of pesticide contamination were collected from a small rural, lowland stream, the Højvads Rende (Lolland, Denmark) and subjected to preconcentration and toxicity testing. The technique proved sensitive enough to detect the presence of toxicity. It is concluded that bioassays on water concentrates obtained by means of XAD solid phase extraction have a considerable potential as a new monitoring tool for pesticides and their metabolites in water.
The performance of a pilot-scale series of ten ponds treating municipal sewage in northeast Brazil
Authors: de Oliveira R. , Silva S. A. , Araujo A. L. C. , Soares J. , Mara D. D. , Pearson H. W.
Published: May 2018

The performance of a pilot-scale long series of ten ponds was evaluated in terms of the removal of BOD5, COD, suspended solids and faecal coliforms with data from two experiments with total mean hydraulic retention times of 19 and 28.5d. Overall removals were very good and in both experiments the final effluent of the series complied with the recommended FC count of less than 1000 per 100ml for unrestricted irrigation, and unfiltered BOD5 concentrations were less than 20 mg/l. The long series of ponds was concluded to be a land-saving alternative compared to other pond configurations previously studied at EXTRABES.
Occurrence and removal of Giardia sp. cysts by Kenyan and French waste stabilisation pond systems
Authors: Grimason A. M. , Wiandt S. , Baleux B. , Thitai W. N. , Bontoux J. , Smith H. V.
Published: May 2018

A study was conducted to determine the occurrence and removal of Giardia sp. cysts in municipal wastewater by two waste stabilisation pond systems; one at Eldoret, Kenya and one at Meze, France. A total of 71 and 26 grab raw wastewater samples from Eldoret and Meze, respectively, were examined for the presence of cysts. Cysts were detected in 37% (26) and 100% (26) raw wastewater samples, respectively. Cyst concentrations detected in raw wastewater samples ranged from 1×103 to 2.5×104 cysts/l at Eldoret and 230 to 2.5×104 cysts/l at Meze. At Eldoret, all anaerobic (8/8), secondary facultative (5/5) and primary maturation (5/5) pond effluent samples examined were positive for Giardia. Cyst concentrations ranged from 1.25 to 483 cysts/l (anaerobic), 23.5 to 192.5 cysts/l (secondary facultative) and 17.2 to 118.5 cysts/l (primary maturation), respectively. At Meze, cysts were detected in 12 of 12 primary facultative (range 4.4 to 48 cysts/l) and 9 of 11 (82 %) primary maturation pond effluents (range 0.2 to 16 cysts/l). In final maturation pond effluent, Giardia cysts were detected in 100% of final pond effluents discharged from Eldoret (n=10; range 21 to 90 cysts/l) and 7 of 16 (44%; range 0.1 to 2.5 cysts/l) from Meze. The occurrence of cysts in final pond effluents examined would indicate that cumulative retention periods of up to 25.3 days at Eldoret and 40 days at Meze would be sufficient to remove between 99.1% and 99.7% of cysts, respectively, but that such retention periods are insufficient to ensure the complete removal of Giardia sp. cysts.
Wastewater treatment mechanisms in anoxic stabilization ponds
Authors: Almasi A. , Pescod M. B.
Published: May 2018

Studies on the performance of wastewater stabilization ponds operating in the “grey” area of organic loading between fully anaerobic and facultative conditions show that organic matter removal is still satisfactory. The results obtained revealed that wastewater treatment mechanisms are mainly based on biochemical reactions in the anoxic system. Although physico-chemical mechanisms were not negligible, algal activities in the presence of light proved to be important in the surface layer of the pond and facultative bacteria were working mutually with the algae. Motile flagellate algae (Euglena and Chlamydomonas) were the only species found to exist under anoxic conditions.

It was also determined that sulphate-reducing bacteria predominated in the lower volume of the anoxic ponds, rather than acidogenic bacteria, and this caused sulphide and hydrogen sulphide build-up in the pond's contents. The bottom volume of the ponds and the benthic sludge in laboratory-scale anoxic ponds contained acid producers and methanogenic bacteria causing the release of biogas. It is hypothesized that phototrophic bacteria (purple sulphur-, green sulphur- and purple non-sulphur bacteria) act as a biological filter to oxidize sulphide and hydrogen sulphide in the euphotic zone of the anoxic ponds. As a consequence of the latter biological activities, anoxic ponds are likely to prove viable alternatives to anaerobic and facultative ponds, where odour nuisance and high land requirements, respectively, are to be avoided.
Improved performance and increased applicability of waste stabilisation ponds by pretreatment in a UASB reactor
Authors: Frassinetti Paula , Catunda Cavalcanti , van Haandel Adrianus C.
Published: May 2018

Traditionally waste stabilisation ponds (WSPs) are built as flow-through systems with an anaerobic, a facultative and one or more maturation ponds in series. The anaerobic pond can be substituted with great advantage by an upflow anaerobic sludge blanket (UASB) reactor. The practical advantages are that the required volume for the UASB reactor is much smaller than the anaerobic pond (20 to 30 times) and that the biogas in the UASB reactor is captured, so that odour problems can be eliminated. The UASB reactor is neighbour friendly and can be used in densely populated areas.

The UASB reactor is more efficient than the anaerobic pond, so that the residual organic load is small and the subsequent pond configuration can be designed with the specific purpose of eliminating pathogens. By adopting a plug flow regime, the required area for a particular hygienic effluent quality can be greatly reduced. Also, since the UASB effluent has good transparency, photosynthesis in the ponds is intense and pH increases due to biological carbon dioxide consumption, accelerating the death rate of pathogens and opening the possibility of reducing nutrients: Nitrogen by desorption of gaseous NH3 and phosphorus by phosphate precipitation.

The fact that an odour free system with a high quality effluent can be produced in relatively small system composed by a UASB reactor + maturation ponds, increases the applicability of this system for sewage treatment in urban areas. As operation of both UASB and ponds is very simple, several small treatment plants instead of one large central unit may be constructed. Thus a very significant of the sewerage network may be achieved.
Melbourne water's wastewater treatment lagoons: design modifications to reduce odours and enhance nutrient removal
Authors: Hodgson Brian , Paspaliaris Peter
Published: May 2018

Some properties of 3 “new style” wastewater treatment lagoons, 115E, 55E and 25W at the Melbourne Water, Western Treatment Plant (WTP) treating some 250 megalitres (ML) of untreated wastewater each day are described. There is a potential residence time for each of 120 days and each consists of a sequence of up to 11 ponds. Pond 1 has an anaerobic reactor of 90, 150, and 150 ML respectively and Warmens floating aerators are installed on ponds 1 and 2 of 115E and 25W and pond 1 of 55E. BOD5 values of less than 50 are achieved by the end of pond 2 and these together with the installation of the HDPE cover on 115E have effectively reduced odour emissions. Nitrogen is removed by ammonification followed by either nitrification/denitrification, or algal growth which is grazed by zooplankton. Since the introduction of the aerators, chemolithotrophic ammonia oxidising bacteria (CAOB) are more frequently exposed to the inhibitory action of UV light, and therefore nitrification is more sporadic. Turbidity of the water may play a significant role in protecting the CAOB from UV light. The lagoons have the potential to produce an effluent with inorganic-N levels of less than 2 mg/L, a BOD5 of less than 50 mg/L and low levels of algae. The covered anaerobic reactor can in each case produce up to 20,000 cubic metres of gas each day comprising of 80% methane. Methane will be used to generate electricity, and the zooplankton generated by feeding on algae will be harvested to provide food for fish fry.
Nitrogen removal in baffled waste stabilization ponds
Authors: Muttamara S. , Puetpaiboon U.
Published: May 2018

This study evaluated nitrogen removal in Baffled Waste Stabilization Ponds (BWSPs) comprising laboratory and pilot-scale ponds with different number of baffles. The aim was to promote the waste stabilization pond practice for wastewater treatment in tropical countries by increasing nitrogen and organic carbon removal efficiency or reducing the land area requirement through the use of baffles which increased the biofilm biomass concentrations. The experiments started with a tracer study to find out the hydraulic characteristics of each pond. It was shown that the dispersion number decreased with increasing flow length and number of baffles which indicated more plug flow conditions. The deviation of actual HRT from theoretical HRT was computed and the flow pattern suggested the existence of an optimum spacing of baffles in BWSP units. The investigations further revealed that more than 65% TN and 90% NH3-N removal efficiencies were achieved at HRT of 5 days in a 6 baffled pond, which corresponds to the specific area of 34.88 m2m3. TN and NH3-N removal increased with increasing number of baffles in the BWSP units. Combined algal/bacterial biofilm grown on the baffles immersed in the ponds showed potential for increasing the extent of nitrification. COD removal increased with higher number of baffles with its maximum removal efficiency at 6 baffles. Compared with normal WSP, BWSP gave higher TN, NH3-N, COD and BOD5 removal efficiency. The effluent SS concentrations from the laboratory-scale 6 baffled pond were less than 20 mg/L at HRT of 3 days or more.
Hydrodynamics in the packed bed of the anaerobic fixed film reactor
Authors: Chua H. , Fung J. P. C.
Published: May 2018

The anaerobic fixed film reactors (AFFR), containing a mixed population of bacteria immobilized on the surfaces of expanded-clay support medium, have been successfully applied in the simulation of high-strength trade effluent treatment. This paper presents residence time distribution (RTD) studies to investigate the hydrodynamic characteristics in the packed bed of this novel type of reactor under the mixing effects of an effluent recycle stream. The results show that the flow pattern is characterized by various extents of back-mixing as predicted by the dispersion model. An effluent recycle at a rate equivalent to replacing the liquid content of the AFFR three times per hour achieved a large amount of dispersion in the packed bed. The AFFR without recycle had an intermediate amount of dispersion. This study shows that treatment performance of AFFRs and the cause of reactor failure are related to the effects of the effluent recycle in diluting and distributing the organic constituents of the trade effluent.
Treatment of landfill leachate by preozonation and adsorption in activated carbon columns
Authors: Fettig J. , Stapel H. , Steinert C. , Geiger M.
Published: May 2018

Landfill leachate pretreated in an aerobic biological stage was studied with respect to the adsorption behaviour of its organic components with and without preoxidation by different amounts of ozone. Isotherm data evaluated by adsorption analysis showed that the fractions of non-adsorbable and weakly adsorbable species had been increased after preoxidation. As a result, the carbon capacity in a fixed-bed adsorption process was expected to be significantly lower for preoxidized leachate. This conclusion was confirmed by data from column experiments. The breakthrough curves under operating conditions typical for leachate treatment could be predicted quite well by the homogeneous surface diffusion model when no preoxidation was applied. After preozonation about 40% of the remaining organic substances were biodegradable. Data evaluation revealed that biodegradation took place inside the activated carbon beds. Therefore the total removal of ozonated leachate in activated carbon columns will be higher than the removal due to adsorption processes. An economic analysis must show in any practical case whether a combination of preoxidation and adsorption will be more cost-efficient than either of the single processes. The modelling technique applied in this study can be a useful tool for that purpose.
Enhancement of decomposition of 2-chlorophenol with ultrasound/H2O2 process
Authors: Lin Jih-Gaw , Chang Cheng-Nan , Wu Jer-Ren , Ma Ying-Shih
Published: May 2018

We investigated the effects of pH, ionic strength, catalyst, and initial concentration on both decomposition of 2-chlorophenol (2-cp) and removal of total organic carbon (TOC) in aqueous solution with ultrasonic amplitude 120 μm and H2O2 (200 mg/l). When the initial concentrations of 2-cp was 100 mg/l and the pH was controlled at 3, the rate of 2-cp decomposition was enhanced up to 6.6-fold and TOC removal up to 9.8-fold over pH controlled at 11. At pH 3, the efficiency of decomposition of 2-cp was 99% but the removal of TOC was only 63%; a similar situation applied at pH 7 and 11. Hence intermediate compounds were produced and 2-cp was not completely mineralized. When the concentration of ionic strength was increased from 0.001 to 0.1 M, the rate of 2-cp decomposition was enhanced only 0.3-fold, whereas the TOC removal was not enhanced. In comparison of the effects of pH and ionic strength, pH had greater influence on both 2-cp decomposition and TOC removal than ionic strength. The effect of a catalyst (FeSO4) on decomposition of 2-cp was insignificant comparing with direct addition of H2O2. The reaction rate at a smaller initial concentration of 2-cp (10 mg/l) was more rapid than at a greater one (100 mg/l). The rate of 2-cp decomposition and TOC removal appeared to follow pseudo-first-order reaction kinetics.
Assessment of sediment behaviour in a cunette-shaped sewer section
Authors: Verbanck Michel A.
Published: May 2018

The accumulation of deposits in sewers causes widespread concerns of either operational or environmental nature. It is believed that a number of sediment-related nuisances can substantially be controlled in adapting the characteristics of sewer pipes as a function of local constraints and circumstances. In particular, key design parameters such as cross-section shape or hydraulic roughness of inner walls are currently selected basing more on empiricism and intuition than on full knowledge of the sediment transport driving processes. A valid track for optimization of these parameters is to run mathematical simulations of the sediment transport behaviour under varying design scenarios. This option, however, supposes that a robust mathematical procedure to compute sediment transport capacity in sewers is available, embracing all primary physical factors of influence. Starting from a theoretical description of shear turbulence suggested by Bagnold (1966), a suspension formula is developed dedicated to the specific sewer flow properties. Applying this formula to the case of a main sewer presenting a composite cross-section allows to illustrate how geometrical discontinuities influence sediment transport characteristics in real conduits.
Simultaneous oxidation and reduction treatments of polluted water by a bio-electro reactor
Authors: Kuroda M. , Watanabe T. , Umedu Y.
Published: May 2018

Application of a bio-electro reactor for treatment of various kinds of polluted water was investigated experimentally. Aqueous solution of nitrate, ammonium and/or organic matter were used as synthetic polluted water. Denitrification of the nitrate polluted water without organic matter proceeded effectively by utilizing hydrogen gas produced by electrolysis of water in the reactor. The bio-electro reactor was also available for the treatment of nitrate polluted water containing organic matter when the C/N concentration ratio was up to 1.0 under the condition of 100 mA of applied electric current. The nitrate removal efficiency from nitrate polluted water containing acetate at C/N=1.0 was more than 90% at 5 hours of HRT and 80% even at 2.8 h HRT. For the treatment of ammonium polluted water, nitrification and denitrification proceeded simultaneously in a bio-electro reactor where nitrifying and denitrifying microorganisms were immobilized on the electrodes. The results obtained in this study suggested that the bio-electro reactor system was capable to application for oxidation and reduction treatments of the nitrate and ammonium polluted water.
Summary: United States “sewer solids” settling characterization methods, results, uses and perspective
Authors: Pisano William C.
Published: May 2018

This paper summarizes recent U.S. experience involving “sewer solids” settling experiments. Over the last 15 years many such characterizations have been conducted during the design of combined sewer overflow (CSO) and stormwater high rate treatment facilities. Since the early 1980s there has been little organized U.S. research to summarize results and settling column methods used. This information is organized and solids settling curves for different waste types are presented noting settling column method used. Median settling velocities for each waste type are given.
Methods for determining the settling velocity profiles of solids in storm sewage
Authors: Aiguier Emmanuelle , Chebbo Ghassan , Bertrand-Krajewski Jean-Luc , Hedges Peter , Tyack Naomi
Published: May 2018

Recently, research has shown that a settling process is an efficient treatment for the removal of suspended solids from storm sewage. In order to design settling tanks, there is a need to determine the settling velocity characteristics of these solids. Devices and test methods for measuring settling velocities of solids in storm sewage have been developed by researchers. A literature review has revealed that the settling velocity profiles obtained with some methods (Chebbo, 1992), (Michelbach and Wohrle, 1993) and (Tyack et al., 1993) are very different. In order to explain why the results are different and to quantify the influence of the experimental procedure on the settling velocity grading curves, we have compared the selected methods when tested with the same sample and we have studied the effects of the conservation of the sample before the test, of the concentration of solids in the device and of the nature of the water on the settling velocity profiles. The results of the comparative tests indicate that the settling velocities are significantly lower with both the Cergrene and Aston methods than with the UFT test procedure. Moreover, the study has shown that the settling characteristics of solids change with time, that the use of sewage liquor rather than demineralised water or drinking water can change the results of the measurement and that the higher the concentration of solids, the greater the velocity of settled particles.
Laboratory investigations into cohesive sediment transport in pipes
Authors: Skipworth Peter J. , Tait Simon J. , Saul Adrian J.
Published: May 2018

In the UK many sewers are laid to shallow gradients and as a consequence, suffer from recurrent sediment deposition. The loss in conveyance due to these deposits may contribute to hydraulic overloading problems and the wash-out of in-sewer sediment deposits may result in a rain induced “foul flush” of pollution which may subsequently be discharged via a CSO to the receiving water course.

This paper reports the results of a series of controlled experiments in the laboratory in an attempt to better understand the factors which influence the erosion of cohesive sediment beds. Apparatus, formerly used for fixed bed work, was modified to assess the erosion characteristics of movable beds. Samples were taken from the flow during computer generated hydrographs and these were later assessed for the concentration of suspended sediment using a spectrophotometer.

Whilst other studies have been concerned with the erodability of different sediments, this study has been limited to one cohesive sediment type and has concentrated on two aspects of the relationship between the properties of the flow hydrograph and the erosion and transport of cohesive sediment beds. Specifically, the effect of the rate of increase of the rising limb of the hydrograph and of the ultimate flowrate on the pollutograph have been examined.

This series of experiments has produced evidence that the measured suspended sediment transport rate of cohesive-like materials exposed to a variable flowrate, is dependent both on the values of the final flowrate and on the rate of the initial temporal change of the flowrate, and is not solely dependent on the “steady state” flow variables.
Treatment of domestic sewage from rural settlements by a membrane bioreactor
Authors: Ueda T. , Hata K. , Kikuoka Y.
Published: May 2018

This study examined the feasibility of applying a membrane bioreactor to small wastewater treatment using a pilot-scale plant. The operation was continued for 336 days. From the start to 251st day, the operation was continued without membrane washing. During the latter term of the operation, however, suction pressure increased rapidly corresponding to the increase of sludge viscosity. Because sludge viscosity increase occurred right after the suspension of sludge wasting, excess sludge must be wasted at regular intervals in order to keep low sludge viscosity. More than 90 % of organic matter, suspended solids, and coliform bacteria were successfully removed. As far as nitrogen removal was concerned, denitrification was the rate determining step in this system. To enhance denitrification, the following three points should be considered: i) to concentrate inflow of raw sewage at the beginning of anoxic period, ii) to shorten aeration time, and iii) to maintain high MLSS concentration.