bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of an RT-PCR internal control to evaluate viral removal
Authors: Le Guyader F. , Menard D. , Dubois E. , Haugarreau L. , Kopecka H. , Pommepuy M.
Published: May 2018

We constructed an internal control based on the poliovirus genome and cloned it into a transcription plasmid to obtain a competitor RNA distinguishable by its size from the wild-type PCR product. A known number of copies was introduced into sewage samples before nucleic acid extraction in order to evaluate the reliability of the extraction step and amplification. The final gel was analysed with a densitometer and the number of viral RNA copies present in the sewage was calculated. In vitro experiments were carried out with this internal control with peracetic acid and UV to estimate decontamination efficiency. A very high concentration of peracetic acid was required to eliminate viruses with a moderate UV dose to obtain a negative PCR. This study demonstrates that competitor RNA is useful both in controlling the different reaction steps (extraction and amplification) and inhibitor detection and in providing a quantitative estimation of contamination.
Application of microbiological (certified) reference materials
Authors: Mooijman K. A. , Havelaar A. H.
Published: May 2018

The development of microbiological reference materials (RMs) has succesfully led to the certification of six materials (CRMs) and to the production of a wider range of non-certified reference materials. Both materials (RM and CRM) are prepared in the same way. They consist of gelatin capsules filled with milk powder artificially contaminated with a selected test strain. The difference between an RM and a CRM is the degree of control of the materials. Because of this difference the RMs and CRMs differ largely in price and application. An RM is intended to be used in daily quality control (QC) of microbiological (routine) analysis. For this purpose the use of a control chart can be very useful. A CRM is intended to be used incidentally, e.g. for validation of a (new) method, or for a complete check of the performance of the laboratory and technicians. The certified value of a microbiological CRM is method dependent. A user of a CRM will compare their mean results with the given certified value and confidence limits. With a so-called power calculation technique the optimal number of capsules and replicates for a CRM were calculated.
The effect of anaerobic zone mixing on the performance of a three-stage Bardenpho plant
Authors: Williams S. C. , Beresford J.
Published: May 2018

Thames Water have built a three-stage Bardenpho activated sludge plant to treat 50% of the wastewater flow at Slough in the United Kingdom. Following commissioning, the plant performed well in terms of nitrification and denitrification but did not produce an effluent with a low phosphorus concentration. One possible explanation for the poor performance was the mixing of the anaerobic zone. The flow characteristic of the anaerobic zone was identified by tracer tests and alternative mixing regimes were tested. The results showed that reducing the mixing energy in the anaerobic zone had no detrimental effect on the effluent quality. The plant has operated with the reduced mixing input for nine months and the effluent phosphorus concentration has been reduced from 2.1 mgl−1 to 0.8 mgl−1.
Large-scale nitrogen removal demonstration at the blue plains wastewater treatment plant using post-denitrification with methanol
Authors: Bailey Walter , Tesfaye Akile , Dakita Jerry , McGrath Michael , Daigger Glenn , Benjamin Alex , Sadick Thomas
Published: May 2018

The Chesapeake Bay Agreement of 1987 calls for an overall reduction in nutrient loading of forty percent of 1985 levels by the year 2000. Signatories to the agreement include the states located in the Bay's watershed and the District of Columbia. The District's 16.2 m3/sec (370 mgd) Blue Plains Regional Wastewater Treatment Plant is the single, largest point source of nitrogen load to the Bay, discharging approximately 18 metric tons per day. In an effort toward meeting the nitrogen reduction goal, a post-denitrification demonstration study was recently begun to access its potential for long-term implementation.

The denitrification demonstration project involves operating half of the nitrification facilities in a nitrification-denitrification mode using methanol as a carbon source for post-denitrification. The other half continues operation in a nitrification-only mode as a control. The post-denitrification process was selected for demonstration because it utilizes existing facilities and may offer substantial long-term cost savings. Objectives of the study are to demonstrate the process without a negative impact on effluent quality, to verify performance and capacity, to determine the stability and limitations of the project, and to compare the process to other nitrogen-removal technologies.

Thus far, the process has been successful in removing nitrogen despite problems with phosphorus limitation and with the settling characteristics of the denitrification sludge. It is believed that insufficient phosphorus availability has been responsible for problems associated with settling, sludge yield, methanol use, and denitrification rates. Recently, phosphorus input to the denitrification process has been increased by reducing metal salt addition in upstream processes and preliminary results have been promising. If performance criteria are achieved without sacrificing plant capacity, the process will be continued at full scale.
Evaluation of phosphorus removal in anaerobic-anoxic-aerobic system - via polyhydroxyalkonoates measurements
Authors: Chuang S. H. , Ouyang C. F. , Yuang H. C. , You S. J.
Published: May 2018

Accumulating and utilizing PHAs (polyhydroxyalkanoates), i.e. a major carbon reserve of polyphosphate accumulating organisms (PAOs), is a prerequisite for phosphorus removal in an enhanced biological phosphorus removal (EBPR) system. To evaluate phosphorus removal, this study investigates the behavior of PHAs in a hybrid anaerobic-anoxic-aerobic process, operating under various sludge retention times (5, 10, 12 and 15 days) and dissolved oxygen conditions (0.5, 1.0 and 2.0 mg/l in aerobic stage). PHAs and phosphorus measurements in the pilot-scale experiments demonstrate that the PHAs content of sludge closely relates to phosphorus release and uptake behavios under anaerobic and aerobic conditions, respectively. The aerobic specific-phosphorus-uptake-rate is directly proportional to PHAs content of sludge in the anoxic stage. When the process is under a high organic loading condition, the sludge exhibits a large amount of PHAs having accumulated in the anoxic stage and a high phosphorus uptake rate in the subsequent aerobic stage. However, experimental results confirm that anoxic phosphorus release, leading to a high concentration of phosphorus flow into the aerobic stage, causes deficient phosphorus removal under a high organic loading condition. Moreover, a low PHAs content of sludge causes incomplete phosphorus removal; the phenomenon occurs when the process is under a low organic loading condition. Based on the results presented herein, we can conclude that the organic loading should be carefully controlled for phosphorus removal in the anaerobic-anoxic-aerobic process.
Avoiding the problems of septic sewage
Authors: Boon Arthur G. , Vincent Alison J. , Boon Kevin G.
Published: May 2018

Septic sewage develops in a sewerage system when aeration of sewage in gravity sewers is inadequate or when sewage is pumped up a rising-main sewer and sulphides are formed. Many variables affect the rate at which septicity develops. Equations have been produced which describe the relation between the variables and septicity. Such equations can be applied to individual sewers or rising mains. To predict, prevent and control septicity of an entire sewerage system will be complex; preventative measures taken upstream will affect the formation of septicity downstream. This paper describes the development of a computer programme, consisting of a series of linked algorithms. The programme enables the sewerage system to be mathematically modelled in order to predict the formation of sulphides in the sewage at identified locations. It also enables the effects of applying a range of preventative measures to be assessed in order to optimise a strategy for prevention and control. The results are described and discussed for application of the model to an extensive sewerage system, serving a population of 665,000. In some circumstances, prevention of septicity may not be practical or it may be expensive. To remove odours from ventilated air, which includes hydrogen sulphide, a novel, reliable, low-cost and effective catalytic filter has been developed. This filter is described, together with performance data obtained during recent full-scale operation.
Effect of draft tube diameter on nitrogen removal from domestic sewage in a draft tube type reactor
Authors: Fujiwara Taku , Somiya Iso , Tsuno Hiroshi , Okuno Yoshio
Published: May 2018

The effect of the ratio of draft tube diameter to reactor diameter (Di/Do) on the efficiency of nitrogen removal from domestic sewage is discussed based on liquid-circulating flow rate and continuous treatment data. More than 2.5 minutes of circulation time in the annulus part, which is required to create an anoxic zone, could be maintained under operating conditions in which air flow rate per reactor volume was 2 m3/(m3 · hr) and Di/Do was 0.19. When Di/Do was set at 0.19, the average total organic carbon (TOC), total nitrogen (TN) and dissolved nitrogen (DN) removal efficiencies were 83.2%, 72.1% and 71.6%, respectively, which were higher than those when Di/Do was at 0.26 or 0.36. From these results, it is concluded that 0.19 is the best Di/Do for nitrogen removal in a draft-tube type reactor with an effective depth of 4.0m under the treatment condition in which the BOD volumetric loading rate is in the range 0.22 to 0.46 kgBOD/(m3 · day). More than 80% nitrification and denitrification efficiencies can be achieved simultaneously when both conditions, the aerobic zone ratio being more than 0.2, and the anoxic zone ratio being more than 0.3, are satisfied.
Evaluation of total emissions from treatment plants and combined sewer overflows
Authors: Guderian Joachim , Durchschlag Andreas , Bever Jürgen
Published: May 2018

Based upon the connection of a simulation program for combined sewer systems with the IAWQ-Activated Sludge Model No.1 the new simulation tool GEMINI was developed, which allows the calculation of sewer and sewage treatment plant as a unit. Some obtained results are presented in an example. They suggest, that for every treatment plant a rate of inflow is determinable, which leads to a minimum of total emissions out of sewer and treatment plant. The optimal value of sewage treatment plant inflow in the example is distinctly greater than the design flow rate fixed in German design rules. So it is recognizable that a rigid flow management for sewer and treatment plant does not always fulfil the aim of minimization of total emissions.
A model for organic matter removal in free water surface constructed wetlands
Authors: Polprasert C. , Khatiwada N. R. , Bhurtel J.
Published: May 2018

This study was conducted to determine performance of free water surface (FWS) constructed wetlands located in the tropics in the removal of organic matter and to assess the importance of biofilm bacteria in the overall kinetics of organic matter (or chemical oxygen demand, COD) removal. Because constructed wetlands normally contain both biofilm and suspended bacteria, a kinetic model incorporating the activities of these two bacteria groups, dispersion number and hydraulic retention time, was employed. The model parameters essential for the calculation of COD removal in FWS constructed wetlands were determined from the experiments and some from the literature. The model was found satisfactory in predicting COD removal efficiencies in a pilot-scale FWS constructed wetland unit treating a domestic wastewater.
Distribution and removal of Giardia and Cryptosporidium in water supplies in Germany
Authors: Karanis Panagiotis , Schoenen Dirk , Seitz H. M.
Published: May 2018

This study has been conducted, to estimate the distribution of Giardia and Cryptosporidium in German water supplies and the removal efficiency of surface water treatment plants for Giardia and Cryptosporidium by conventional treatment. Water samples from six surface water treatment plants in different parts of Germany were simoultaneously examined for Giardia and Cryptosporidium. Investigations for both parasites were carried out in the period from July 1993 until December 1995. The results confirmed the occurrence of Giardia and Cryptosporidium in surface and raw water, in intermediate steps after treatment, in back wash water, in the first filtrate and in final water. Giardia or Cryptosporidium or both have been found in 76.2% of the investigated raw water sources. The average number of the detected Giardia cysts was 88.2/100 1 (max. 1314/100 1), and the average number of Cryptosporidium oocysts was 116/100 1 (max. 1081/100 1). In the intermediate steps (including flocculation and several steps of filtration), Giardia or Cryptosporidium or both have been found in 33.3% (50/150) of the samples. 14.9% of drinking water samples (7/47) were positive for Giardia (max. 16.8/100 1) and 29.8% (14/47) were positive for Cryptosporidium (max. 20.8/100 1). Overall, Giardia and Cryptosporidium, or both were detected in 38.3% of the drinking water samples. The parasites have been found in nearly all of the investigated backwash water samples. The filtrate of a rapid sand filter was analysed immediately after filter backwashing during the ripening period of the filter. Good elimination results were obtained by optimizing relevant water treatment process, but a low flocculant dose following sudden variation in the raw water quality, causes a breakthrough of Cryptosporidium into the treated water. Although water treatment technologies are effective to remove Giardia and Cryptosporidium, the results clearly show that Giardia and Cryptosporidium evade the filter barries in the absence of visible treatment deficiencies and low turbitidy level, and contaminate final water.
Characterization of raw sludge, chemically modified sludge and anaerobically digested sludge in Hong Kong
Authors: Chu C. W. , Poon C. S. , Cheung R. Y. H.
Published: May 2018

Chemically Enhanced Primary Treatment (CEPT) or Chemically Assisted Primary Sedimentation (CAPS) is being employed at the new sewage work on Stonecutters Island as part of the Strategic Sewage Disposal Scheme (SSDS) in Hong Kong. CAPS involves the use of chemical coagulants (such as lime or ferric chloride) to induce coagulation or flocculation and let these finely-divided particles form large aggregates (floc) so that they can settle out within a reasonable period of time. In this study, five sludge samples collected from different sewage treatment plants in Hong Kong were physically and chemically characterized. They were chemically modified sludge from Stonecutters Island (CAPS) raw sludge from Tai Po and Yuen Long Sewage Treatment Plant (STP) (rTP & rYL) and anaerobically digested sludge from Tai Po and Yuen Long STP (dTP & dYL). It was found that CAPS sludge was better than other 4 sludge samples in terms of settleability and dewaterability. CAPS sludge contained significant higher amounts (p<0.01) of extractable compounds than other sludges (except NO3− for dTP, NH4+ and PO43− for dYL). The concentration of total N and P in CAPS sludge were significantly higher (p<0.01) than other sludges (except dYL). The concentrations of total Cu, Pb, Ni, Cd, Cr and K in the CAPS sludge were also significantly higher (p<0.01) than other sludge samples. Most of the metals (Cr, Pb, Cr and Zn) in CAPS sludge were associated with the organically-bounded phase. It is concluded that there are significant differences in both physical and chemical properties between the chemically modified sludge and biological treated sludges.
Effect of ozone on disinfection by-product formation of algae
Authors: Plummer Jeanine D. , Edzwald James K.
Published: May 2018

The presence of algae in a drinking water source can have a significant impact on the treatment of that water. Algae and their extracellular organic matter can be precursors for disinfection by-product (DBP) formation which is of concern for treatment plants that employ pre-chlorination. This research examined the DBP formation of suspensions of Scenedesmus quadricauda, a green alga, and the effect of ozonation on that formation. Trihalomethane formation potential (THMFP) was found to increase by 10% to 30% when preozonation was applied versus non-ozonated samples. A slight increase in haloacetic acid (HAA) formation was also observed in the ozonated samples. Ozonation caused an increase in the dissolved organic carbon content of the algal suspension, thereby increasing the concentration of precursors. The alkalinity of the water did not significantly affect the formation potential of either THMs or HAAs.
The effect of surges on the performance of rapid gravity filtration
Authors: Glasgow Graeme D. E. , Wheatley Andrew D.
Published: May 2018

Filters used in drinking water treatment are subject to small continuous flow rate fluctuations or surges. Large changes in rate are known to have a detrimental effect on filtrate quality. Less is known about the effects of surging. Past observations suggest that surging may significantly influence filter performance but the effect has yet to be confirmed under controlled conditions and the mechanisms critically examined. Two rapid filters were developed in the laboratory to investigate the influence of surging on performance. Reproducible performance was established before applying surges to one filter only. Measurements of head loss and turbidity were taken with depth and time. Surges were found to reduce filter performance. The fluctuations in flow were found to slow the rate of ripening of the filter, retard the rate of head loss development and reduce the removal efficiency. The experimental results obtained suggest that surging does have a significant effect on rapid filter performance.
Strategies for sludge handling in the Stockholm region
Authors: Mossakowska A. , Hellström B. G. , Hultman B.
Published: May 2018

The annual production of dewatered sludge from the municipal wastewater treatment plants handled by Stockholm Water Company is about 75,000 tonnes. The policy of Stockholm Water Company is to find methods to use the sludge as a resource by recovering its contents of nutrients and earth-forming substances. The most suitable sludge use is considered to be for agriculture. Intensive work has been done on reducing the sludge concentration of toxic metals and other pollutants by use of control of discharges of industrial waters into the sewer network, information campaigns to households, and improved management of storm water. The sludge quality is measured by automatic samplers for dewatered sludge and analyses of heavy metals and certain organic pollutants. Sludges with better quality than limiting values from authorities may safely be used in agriculture, while sludges not fulfilling stringent requirements must be handled by other methods. Due to resistance from the food industry and a number of interest organisations, it is important to find other handling methods also for high quality sludges. Such methods include the use of incineration together with municipal solid wastes or biomass or separation of the sludge into different products for internal or external use.
Combined effects of organic pollution and eutrophication in the South Para reservoirs, South Australia
Authors: Recknagel F. , Burch M. , Jablonskas G. , Minney J. , Schoofs S.
Published: May 2018

Preliminary results of a comparative limnological study of three Mediterranean reservoirs in South Australia from August 1995 until March 1996 are presented. The reservoirs are characterised by meso- to eutrophic and dystrophic conditions. Dynamics and interactions between DOC, SRP and phytoplankton biomass were investigated regarding differences in mixing conditions, water levels and catchment links of the reservoirs. A scenario analysis was conducted to predict effects of artificial aeration and DOC removal in the Barossa reservoir. Results indicate positive and negative feedbacks between organic pollution and eutrophication such as nutrient limitation by organic complexation of phosphorus, light limitation of phytoplankton growth by water colour and DOC release after phytoplankton breakdowns. Orientation of further research and management options are discussed.
Transport of phenolic compounds through a compacted organoclay liner
Authors: Lo Irene M. C. , Mak Raymond K. M.
Published: May 2018

The transport of phenolic compounds through a compacted liner improved with organically modified bentonite (organoclay BB-40) was studied. Organoclay BB-40 is one of the manufactured products of Biomin International, Inc. and is modified with 40 lb of dicetyldimethylammonium per 100 lb of clay. The adsorption of phenolic compounds onto organoclay BB-40 is found to be significant, which could be attributed to the formation of hydrophobic bonding. The hydraulic conductivities of organoclay BB-40 are 1.98 × 10−7, 2.28 × 10−7 and 5.49 × 10−7 cm/sec for the phenol cell, 2-chlorophenol cell and 2,4,6-trichlorophenol cell, respectively. The experimental results of adsorption tests and hydraulic conductivity tests were input into the computer program “Pollute v9” to simulate the transport of phenolic compounds through a compacted organoclay liner material. The simulation result was then compared with phenol transport through the conventional soil liner (90% silty sand and 10% natural clay mineral). It indicates that the retardation of the transport of phenolic compounds using organoclay as a liner material is more significant than using the conventional soil liner, particularly for higher hydrophobic organics.
An algal monitoring protocol: the strategic link between reservoir and treatment process
Authors: Steynberg Machiel C. , Adam K. , Pieterse A. J. H.
Published: May 2018

Eutrophication as well as the removal of algae by the drinking water industry received dedicated attention in past three decades. An interdisciplinary approach will assist catchment and water purification managers to work to the same future – algal blooms in reservoirs dominated by the “ideal algae” which can be removed by conventional unit treatment processes. This paper will provide a futuristic picture of resource and product quality management, based on a historic perspective of eutrophication and algal removal research.
Computer simulation to evaluate the economics of landfill gas recovery
Authors: Milke M. W.
Published: May 2018

A need exists for tools to improve evaluations of the economics of landfill gas recovery. A computer simulation tool is presented. It uses a spreadsheet computer program to calculate the economics for a fixed set of inputs, and a simulation program to consider variations in the inputs. The method calculates the methane generated each year, and estimates the costs and incomes associated with the recovery and sale of the gas. Base case results are presented for a city of 500,000. An uncertainty analysis for a hypothetical case is presented. The simulation results can help an analyst see the key variables affecting the economics of a project.
A concept for an integrative consideration of the drinking water and wastewater/sewage management
Authors: Bjørnsen Gerhard , Gimbel Rolf , Spangenberg Hans-Dieter
Published: May 2018

To guarantee drinking water of high quality not only the drinking water treatment must be of high standards but also the quality of water resources should be the best possible. Therefore, pollution control and pollution risk management in the catchment areas of water resources are important parts of an overall water management concept. This includes the assessment of physical and chemical parameters as well as bacteriological parameters, especially hygienic parameters. A concept for an integrative consideration of drinking water treatment and quality management of water resources is presented.
The challenge of managing water and material balances in relation to eutrophication
Authors: Harremoës P.
Published: May 2018

Eutrophication is the result of overfertilisation of the aquatic environment. In other words, the detrimental effects derived from increased anthropogenic release of nutrients to the environment. By modern concepts of environmental abatement this is no longer only a question of identifying and purifying discharges. It is a question of keeping track of the system of nutrient mining, utilisation, recycle, transport, conversion, containment and release in the modern society - in effect, the total balance of nutrients in society. In Denmark, the point sources of nutrient release have been reduced by an order of magnitude. That has contributed to some improvements, but the diffuse sources have turned out to be more significant than originally expected. They are harder to reduce. That is why more integrated approaches have to be analysed. Four approaches will be analysed: the DPSIR-approach, the 5-options approach, the cause-effect relationship and the material balance analysis.
Phosphorus retention in sediments1
Authors: Boers P. C. M. , Van Raaphorst W. , Van der Molen D. T.
Published: May 2018

Phosphate is usually the most important growth limiting nutrient in aquatic environments. The availability of P is the result of external load and retention in the sediments. This latter is the result of a number of transport, microbial and chemical processes. The role of P in the productivity in systems and in the eutrophication process has initiated a large number of studies to the behaviour of P in sediments. Case studies in Veluwemeer, IJsselmeer, Wadden Sea and German Bight show that sorption on and binding in ferric (oxi)hydroxides, occlusion in calcium carbonates and authigenic mineral formation are the most important retention processes.

However, all this research did not result in totally new approaches in lake restoration, nor did knowledge of internal P loading result in large scale applications of well-known sediment restoration techniques. It did result in more realistic expectations of lake restoration programmes.

At the same time, renewed interest in the overall role of phosphate in the functioning and productivity of systems is emerging. The most important new items are: the role of the productivity is examined at large scale levels; the coupling of productivity with several large scale material cycles and global environmental problems and the study of the behaviour and fate of phosphate within the context of the functioning of entire watersheds.
Contemporary issues in watershed and water quality modeling for eutrophication control
Authors: Thomann Robert V. , Linker Lewis C.
Published: May 2018

Three issues are discussed: controllability of nonpoint nutrient loadings using watershed models; the sometimes counter intuitive results from eutrophication models from nutrient controls for coastal waters; and the potential significant interaction of improvement in habitat for suspension feeding bivalves. For the Chesapeake Bay watershed model, and for Limit of Technology (LOT) controls, a 16% and 45% reduction in nitrogen and phosphorus, respectively, is calculated. For the Bay, it is concluded that removal of phosphorus only is less effective than nitrogen in improving bottom water DO because of differential transport of nitrogen downstream. For the Delaware estuary, a significant decline in phytoplankton chlorophyll has been observed in the absence of any nutrient controls but in the presence of improved DO. A simple model is offered that hypothesized an increase in benthic bivalve filtration of overlying water as a result of improvement in DO.
Modeling the phosphorus retention of the Kis-Balaton upper reservoir
Authors: Clement A. , Somlyódy L. , Koncsos L.
Published: May 2018

The Kis-Balaton reservoir system, consisting of the upper and lower reservoirs, is located near to the mouth of the Zala River. It was established for the protection of Lake Balaton against high nutrient loads. In accordance with the original plan prepared at the end of 70s the aim was that before entering the lake, nutrients - primarily phosphorus - will be removed by macrophytes. The Upper Reservoir started to operate in 1985. In contrast to the predictions, it became an open lake dominated by algae. Until 1991 about 50% of the external phosphorus load has been removed yearly. However, the retention efficiency has decreased considerably after reduction of the external load upon phosphorus removal at the wastewater treatment plant of the largest town of the Zala catchment. This observation can be explained by the increased contribution of the internal loading. To analyze the phosphorus removal mechanisms and to understand the behavior of the sediment, different water quality models were applied. The results show that the P retention is characterized by different processes acting spatially differently. Essentially, abiotic processes like settling of inorganic particulate P and the adsorption of dissolved inorganic P are responsible for the P retention in the reservoir, mostly in the neck of the Upper Reservoir. Simple models indicated that the internal loading increased after the external load reduction. In fact, it was not that the internal loading increased, but the adsorption decreased.
The advantages of a constructed reed bed based strategy for small sewage treatment works
Authors: Griffin P. , Pamplin C.
Published: May 2018

The advantages of the use by a major UK water utility serving 8 million people in central England of constructed subsurface flow reed beds for secondary, tertiary and storm water treatment at small sewage treatment works is placed in context with improved permit compliance to more stringent standards and a continuing downward pressure on operating costs. Capital and energy costs are compared with the competing tertiary treatment process of recirculating sand filtration. Further economic advantage is gained by combining tertiary treatment and stormwater treatment.

With over 160 sites in operation by mid 1997 the success of the strategy has given confidence to allow for the early or emergency installation of reed beds to improve or maintain effluent quality before replacement, or in one case the provision, of secondary treatment. Use of constructed reed beds is now being extended to larger facilities where only a proportion of the flow needs to be treated to achieve standards. For tertiary treatment reed beds there is an additional environmental benefit with the typical removal of 10.7 mg/l of total nitrogen.
Effects of the membrane technology of the dimensioning of municipal wastewater treatment plants
Authors: Seyfried A. , Dorgeloh E. , Brands E. , Ohle P.
Published: May 2018

The successful application of membrane filtration on the activated sludge process is a recent development. Two processes are most common: separate modules and submerged modules, with the former being the more promising due to the lower energy consumption. While they allow high sludge ages, conventional sludge ages are equally viable, thus allowing the use of tested and reliable dimensioning techniques. The near perfect solids retention of the membrane filtration, however, can lead to problems with the accumulation of inert solids and heavy metals in the activated sludge. In that area, further research is necessary to develop safe dimensioning methods.
Trends in water quality and algal growth in shallow Frisian lakes, The Netherlands
Authors: Maasdam R. , Claassen T. H. L.
Published: May 2018

About 20 shallow lakes form, together with interconnected canals, one hydrological water system in the province of Friesland. Total water surface area meets 14,000 ha, of which the lakes cover 10,000 ha. The regional catchment area is about 305,000 ha. In summer periods inflow of water from Lake IJsselmeer keeps the system on a constant water table of 0.52 m below sea level.

At the end of the sixties the lakes became hypertrophic. Algae were dominating the biocenoses and submerged water plants disappeared. Systematic investigations started in 1970, and biological data were included from 1976 on. During twenty years a stable, but highly eutrophic situation, passed. Blue-green algae, especially Oscillatoria agardhii, were dominating the phytoplankton. Submerged vegetation was absent and bream dominated the fish-stock.

From 1991 onwards there is a slight improvement in water quality. Transparency increased, phosphorus concentration and algal biomass decreased. Also a shift in phytoplankton species occurred. Dominance of O. agardhii decreased and species diversity increased. First submerged water plants recovered in 1994. Improvements are induced by a combination of measures and a culmination of small effects. Results of 14 years of water quality research are presented. Results are given as trends in time. Attention is paid to the spatial gradient in the province as well. From south to north the chain-arranged lakes represent a remarkable pattern of increasing trophic state, caused by regional loading of nutrients.
Feedforward control of nitrification by manipulating the aerobic volume in activated sludge plants
Authors: Brouwer Harry , Bloemen Michiel , Klapwijk Bram , Spanjers Henri
Published: May 2018

A procedure was developed to manipulate the aerobic nitrification volume by means of model based respirometry. The objective was to oxidise all ammonia nitrogen. The required aerobic volume was calculated from the influent flow rate, the influent concentration nitrifiable nitrogen and maximum ammonia oxidation rate which were obtained from respirometric batch-experiments using model calibration and state estimation techniques. Automation of the procedure resulted in the development of the RESCUE (REspirometric activated Sludge and wastewater Characterisation Unit). The procedure was tested for a pilot scale plug-flow activated sludge plant with satisfactory results.
Optimal control of N-removal in ASPs
Authors: Lukasse L. J. S. , Keesman K. J. , Klapwijk A. , van Straten G.
Published: May 2018

Optimisation of the operation strategy of N-removing activated sludge processes (ASPs) contributes to improved effluent quality and/or costs savings. This paper deals with the development of an aeration strategy yielding optimal N-removal in continuously mixed, continuously fed ASPs. First, optimal control theory is applied to the generally accepted ASM no. 1 model. This study reveals that, from an N-removal point of view, both alternating nitrification/denitrification and simultaneous nitrification/denitrification at limiting DO-levels might be optimal, depending on the uncertain oxygen half-saturation constants of autotrophic and heterotrophic biomass. Hence, taking into consideration the risk of sludge bulking at limiting DO-levels, an alternating anoxic/aerobic strategy is favoured. A Receding Horizon Optimal Control (RHOC) strategy using NH4 and NO3 measurements is developed, enabling feedback control of the alternation between anoxic and aerobic phases with the explicit objective of optimal N-removal. Simple rules are given for straightforward tuning of this controller. The controller successfully passed several tests both in simulation and in application to a pilot plant continuously fed with presettled domestic wastewater.
Hydrogen sulphide and volatile fatty acid removal from foul air in a fibrous bed bioreactor
Authors: Li X. Z. , Wu J. S. , Sun D. L.
Published: May 2018

Odour control in Hong Kong has been addressed as an important issue by the authorities, since odour pollution is generated from many sources including wastewater treatment plants. Although a number of existing technologies are available for odour abatement and control, biological technique is still more attractive due to its low operating cost and ease of maintenance. A newly innovated fibrous bed bioreactor with twin columns was specially designed and constructed in our laboratory, in which an inner column was centred in an outer column. The bioreactor was fully filled with water in order to absorb the odorous components from foul gas and also contained both suspended and attached biomass to degrade the absorbed odorous pollutants. In this study, hydrogen sulphide (H2S) and butyric acid (C4H8O2) were used as odorous components and successfully removed from synthetic foul gases. Many factors affecting the H2S and butyric acid removal efficiency and maximum elimination capacity, such as pH of water solution, gas flow rate and its fluctuation, and sulphate content in solution have been studied. The experimental results demonstrated that the reduction rates of 97.8% for H2S and 99.9% for butyric acid were achieved in this experimental condition. It is proved that this bioreactor was a compact odorous gas treatment system with an application potential for treating foul air with high odour strength and low airflow rate such as the offensive gases from sludge treatment processes in a wastewater treatment plant.
Chlorination for control of biological activity during direct recharge of tertiary effluent
Authors: Fox P. , Wang L. , Johnson P. C. , Houston S. , Houston W. N. , Brown P.
Published: May 2018

Chlorination for the control of biological activity during direct recharge of tertiary effluent was studied in bench-scale simulated aquifers. Both free chlorine and chloramine were studied at Darcy velocities of 360 cm/d to 720 cm/d. A free chlorine residual of 5 mg/l or above inhibited biological activity in the 1.2 m of soil that was studied. A free chlorine residual concentration of 2 mg/l prevented biological activity in the first 0.9 m of exposed soil and significant biological clogging was observed in soil greater than 0.9 m from the injection point. A 2 mg/L residual concentration of free chlorine prevented biological clogging over the 0.9 m of soil adjacent to the injection point. No chlorine addition resulted in clogging adjacent to the injection point indicating that the chloramine inhibited biological activity and allowed biological activity to occur over a greater distance from the injection point. Dissolved oxygen levels decreased to zero in aquifers where significant biological activity was observed and trihalomethane concentrations decreased in these aquifers. Free chlorine appears to effectively control biological clogging adjacent to the injection point while permitting biological activity to develop after the chlorine has decayed to a level of 0.6 mg/l or less.
Characteristics of contaminant transport in bank filtration through dunes
Authors: Choi H. C. , Kim K. S. , Kim I. S.
Published: May 2018

A column experiment simulating bank filtration was conducted to evaluate characteristics of contaminant sorption and migration through saturated porous media. Also a mathematical model describing contaminant transport was developed to delineate results of column tests. Temporal and spatial distributions of ammonia, lead, phenol and trichloroethylene (TCE) were plotted as breakthrough curves (BTCs). BTCs of TCE and lead revealed more retardation in the transport up to 3 pore volumes compared to the other contaminants tested. It was attributed to the higher affinity of the TCE and lead to the solid surface. The mathematical model developed in the reported research, coupled with a linear sorption isotherm model, was based on the mass balance principle in two phases, i.e., solid phase and aqueous phase. The governing equation was generalized in the form of nondimensionalization and was solved by numerical analysis. The proposed model showed an excellent match with experimental results except in the case of TCE BTC. The proposed model was employed to simulate the behavior of ammonia under the environment of ongoing nitrification. Almost 60 times more biomass than ammonia mass was required to produce the reported water quality in the reported literature (KOWACO, 1994). The analysis of numerical experiments showed that the ammonia concentration in the bank filtrate will vary significantly as the bioactivity changes due to environmental factors such as temperature and pH in the system domain.
Predicting disinfection performance in continuous flow systems from batch disinfection kinetics
Authors: Haas Charles N. , Joffe Josh , Heath Mark , Jacangelo Joseph , Anmangandla Uma
Published: May 2018

Disinfection processes have often been characterized by the “CT” concept i.e., the product of disinfectant residual and contact time (perhaps as a function of pH, temperature, and other water quality variations) produces a given level of disinfection. The objective of this work was to develop and validate the use of reaction kinetic models for disinfection process design. Using bench scale (batch) kinetic information, and hydraulic characterization of pilot scale continuous disinfection processes, predictions of continuous process performance were made using a segregated flow model. These predictions were compared to independent experimental measurements of actual inactivation in pilot scale processes. Preammoniation, free residual chlorination, and ozonation were used on two waters from Portland, Oregon (US). Organisms used were Giardia muris, bacteriophage MS2, and Escherichia coli.
Hydrodynamic characterization in dissolved air flotation (DAF) contact zone
Authors: Shawwa Ayman R. , Smith Daniel W.
Published: May 2018

The mechanism of bubble-floc interaction in a DAF contact zone is poorly understood and is usually described by conceptual models. This mechanism is highly dependent on the hydrodynamic conditions within the contact zone, i.e. contact time and degree of mixing. A pulse stimulus-response test was used to characterize the contact zone degree of mixing, in terms of dimensionless Peclet Number, and the contact time, in terms of residence time distribution. The tracer tests were performed at different hydraulic loading rates and recycle ratios. The experimental results confirmed that the axial dispersion model can be used to estimate the degree of mixing inside the contact zone. The results showed that the Peclet Number increased as the hydraulic loading rate increased, for all experiments performed under the same recycle ratio. In addition, the degree of mixing slightly increased as the recycle ratio increased, for all experiments performed under the same hydraulic loading rate.
Wastewater treatment by bio-magnetic separation: a comparison of iron oxide and iron sulphide biomass recovery
Authors: Bahaj A. S. , James P. A. B. , Moeschler F. D.
Published: May 2018

Many microorganisms have an affinity to accumulate metal ions onto their surfaces, which results in metal loading of the biomass. Microbial biomineralisation of iron produces a biomass, which is often highly magnetic and can be separated from water systems by the application of a magnetic field. This paper reports on the magnetic separation of biomass containing microbial iron oxide (Fe3O4, present within magnetotactic bacteria) and iron sulphide (Fe1-XS, precipitated extracellularly by sulphate reducing bacteria) in a single wire cell. Since such bacteria can be separated magnetically, their affinity to heavy metal or organic material accumulation renders them useful for the removal of pollutants from wastewater. The relative merits of each bacterium to magnetic separation techniques in terms of applied magnetic field and processing conditions are discussed.
Is sweep-flocculation relevant to saponite aggregation?
Authors: Lartiges Bruno S. , Chaignon Valerie , Michot Laurent J. , Robert Jean-Louis
Published: May 2018

Synthetic saponites with various Cationic Exchange Capacities were aggregated at pH 8.0 in a stirred vessel by hydrolysed aluminum species. Floc growth was followed by Fraunhoffer laser diffraction and the efficiency of clarification was assessed from conventional residual turbidity and sediment volume measurements. We show that the aggregation mechanisms are layer-charge dependent and can not be described by the widely accepted sweep-flocculation model.
Physical and bacterial processes affecting suspended particulate matter in a tidal river
Authors: Kozuki Yasunori , Hosoi Yoshihiko , Murakami Hitoshi , Kawamoto Katuhiro
Published: May 2018

In order to clarify the origin and behavior of suspended particulate matter (SPM) in a tidal river, variation of SPM in a tidal river was investigated with regard to its size and constituents. SPM was separated into three groups according to size. Change of contents of titanium and organic substances of each group of SPM was examined. SPM which was discharged by run-off was transported with decomposition and sedimentation in a tidal river. Concentration of SPM with a particle size greater than 0.45 μm increased due to resuspension in a tidal river. Origin of SPM with a size of less than 0.45 μm at upstream areas was from natural soil and most of such SPM which had been transported settled near a river mouth. It was determined from examination of the CN ratio and the ratio of the number of attached bacteria to free bacteria that SPM with a size greater than 1.0 μm at upstream areas was decomposing intensively. At the downstream areas, SPM with a size of less than 0.45 μm came from the sea. SPM with particle size greater than 1.0 μm consisted of plankton and substances which were decomposed sufficiently while flowing.
Feasibility of anaerobic biodegradation of PAHs in dredged river sediments
Authors: Johnson Kraig , Ghosh Sambhunath
Published: May 2018

This report examines the anaerobic biodegradation potentials of PAHs in dredged river sediments under several redox environments. Batch biodegradation tests were conducted in bioslurry reactors containing sediment samples from Jones Island, WI. Tests with unamended sediments relied on PAH biodegradation by native bacteria utilizing background nutrients and electron donors and acceptors in the sediment. The amount of degradation of 15 PAH compounds found in the sediment, ranging from naphthalene to benzo(ghi)perylene, was measured. It was observed that all 15 PAH congeners biodegraded to some extent in unamended sediments. Acenaphthene showed the highest degradation at 79% disappearance. Indeno(123cd)pyrene showed the lowest at 8%. A general trend was observed with more disappearance in the lower molecular weight PAHs than the higher molecular weight PAHs. Addition of sulfate as an electron acceptor somewhat enhanced PAH biodegradation, whereas addition of nitrate did not. Induction of methanogenic conditions by adding dextrene (a simple sugar) did not appreciably enhance biodegradation of any of the 15 measured PAH congeners. It was speculated that the relatively high background sulfate levels, accompanied by sulfate-reducing bacteria native to the sediment may have played a significant role in effecting PAH biodegradation.
Effects of biodegradable substrates and microbial concentration on the acclimation of microbes to acrylonitrile in aerobic submerged biofilter
Authors: Hu Hong-Ying , Fujie Koichi , Nozawa Mamie , Makabe Tsuyoshi , Urano Kohei
Published: May 2018

The effects of coexistence-of biodegradable substrates and microbial concentration on the acclimation of microbes to acrylonitrile (AN) in an aerobic submerged biofilter were investigated on the basis of kinetic and ecological studies. The experimental results show that the acclimation of microbial film to AN was promoted by a higher microbial concentration in the biofilter and by the coexistence of glucose and peptone in the influent. It was clarified that the upper limit of AN loading to the biofilter for the ultimate degradation, i.e., complete mineralization, of the influent AN was about 2.0-2.2 kg/m3. d. In addition, a new microbial quinone profile method was applied for the analysis of the microbial community change in the biofilter. The change in quinone profiles of the microbial film during the acclimation to AN suggested that Brevibacterium sp., Pseudomonas aeruginosa and Corynebacterium sp. could contribute to the degradation of AN in the aerobic biofilter.