bluuebunny/crossref_metadata_2025 huggingface dataset:
Complete characterisation of thermally treated sludges
Authors: Anderson N.J. , Dixon D.R. , Harbour P.J. , Scales P.J.
Published: May 2018

As disposal options for sludges become more difficult to find and more expensive to operate, those relying on some form of thermal treatment are becoming more commercially attractive. The incentive, especially for more heavily populated countries, is the production of treated solids suitable for beneficial application to land. It is the level of treatment required to achieve this cost effectively which has been the focus of much of the research in this field. There are now several commercially available plants designed to thermally treat sludges and many have been in full scale operation for a number of years. One of the auxiliary claims often made by proponents of such treatments, is that the resultant sludges are more amenable to dewatering and therefore easier and cheaper to handle. In this work we have used a novel filtration rig to obtain complete sets of filtration data for different sludges. Historically sludge characterisation has been achieved by measurement of an empirical Capillary Suction Time (CST) parameter, however with the new filtration apparatus it is now possible to obtain fundamental sludge characteristics across a wide range of volume fractions in hours not days. We have applied this technology to characterise different sludge samples before and after thermal treatment under different sets of operating conditions (pH, temperature and pressure) to simulate some of the commercially available thermal treatment technologies. We have also examined the effects of various chemical oxidants (hydrogen peroxide and Fenton's reagent) used as pretreatments to the thermal process and attempted to compare their cost efficiencies. The results show that the physical structure of the sludge is irreversibly altered by decreasing the pH or heating to temperatures in excess of 150°C in a way which significantly enhances the dewaterability of the material. The treated sludge not only has a higher permeability but also has a higher final per cent solids (often in the autothermal region). In contrast the amounts of chemical additives used in pretreatment to achieve similar effects are cost prohibitive.
Identification of factors contributing to degradation in autothermal thermophilic sludge digestion
Authors: Csikor Zs. , Miháltz P. , Hanifa A. , Kovács R. , Dahab M.F.
Published: May 2018

A laboratory scale ATAD reactor (6 days SRT, 24 h feed cycle) was operated at quasi steady-state conditions with real waste activated sludge feed. Hydrolysis tests of waste activated sludge demonstrated that 10% of feed suspended matter is hydrolysed practically instantaneously and 20-30% of all fed suspended matter is dissolved after 60 minutes in tap water and in cell free reactor liqueur equally. Respirometric, VSS and COD concentration data served as basis for calibration of a simple VSS based kinetic model. The calibrated model provided good fit to two separate sets of measured data. This model was used to evaluate different operation strategies. Modification of cycle length does not affect overall VSS removal rate, while shorter cycle length or continuous operation helps avoid oxygen limited conditions. Further advantages of shorter feed cycles (reduced cooling effect, greater realizable load) support choosing continuous operation of the ATAD system if the main goal is VSS reduction. While reactor cascades increase efficiency, this advantage diminishes with increasing load. At high load rates increased construction costs are not justified by the expected improvement in efficiency.
Removal of fecal coliforms by thermophilic anaerobic digestion processes
Authors: De Leén C. , Jenkins D.
Published: May 2018

Recent U.S. EPA regulations (40 CFR Section 503) specify maximum concentrations of pathogens and metals for Class A wastewater treatment plant sludges. The most common sludge process is mesophilic (35¡C) digestion which stabilizes the solids, produces a combustible gas but does not create an effluent that meets the 503 Class A pathogen requirements. This investigation was conducted to determine whether anaerobic digestion processes incorporating a thermophilic stage could achieve 503 Class A pathogen levels. The research reported here was a bench-scale screening study meant to identify the most promising process alternatives for further investigation. Fecal Coliform (FC) concentrations were used to assess disinfection efficiency. Digesters were 30 L capacity fed semi-continuously in draw-fill mode. Digester startup was rapid to produce true thermophiles. Temperature staging and pH were assessed in 3 sets of experiments: Set 1 were one stage (“acid phase”), Set 2 were one stage (“acid + methane phases”) and Set 3 were two stage (“acid phase” then “methanogenic phase”). Feed was a 1:1 mixture of Thickened Waste Activated Sludge and Primary Sludge. The following anaerobic digestion configurations and operating parameters allowed the production of digested sludge with a mean FC concentration statistically less than 103 (the regulatory value for Class A sludge): thermophilic single stage acid phase at 52 and 62°C; thermophilic single stage acid + methane phase at 48°C, 52°C and 62°C; two-stage mesophilic acid phase followed by mesophilic methane phase; two stage mesophilic acid phase followed by thermophilic methane phase at 48°C, 52°C and 62°C. If the maximum digested FC concentration must be below 103 MPN/g TS then the following digester configurations and operating conditions will be compliant: two stage mesophilic acid phase followed by thermophilic methane phase at 52°C and 62°C.
Two combined techniques to enhance anaerobic digestion of sludge
Authors: Moeller-Chávez G. , González-Martínez S.
Published: May 2018

The rate-limiting step during anaerobic digestion is the hydrolysis of the particulate organic matter and methanogenesis. Certain elements, such as iron, nickel and cobalt and some growth factors such as coenzymes are needed for the adequate growth of the organisms. The main objective of this research was to enhance anaerobic digestion of primary sludge combining thermal and alkaline pre-treatment with stimulation of the methanogenic activity by adding yeast extract. Primary sludge was exposed, separately, to alkaline and thermal pre-treatment procedures. After this pre-treatment, different amounts of yeast extract were added to the sludge. The best COD, TSS and VSS removal rates were observed without pre-treatment and with the addition of 0.1% in weight of yeast extract. The highest specific methane production was obtained with thermal pre-treatment and 0.1% yeast addition. A second experimental stage was run for a closer analysis of the preliminary results. Thermal pre-treatment and 0.1% yeast addition was tested. The best results regarding both COD, TSS and VSS removal rates and methane production were obtained without thermal pre-treatment and with addition of yeast extract. The calculated F-values for the ANOVA-test show that the main influencing factor was the addition of yeast extract where the Biochemical Methane Production was doubled compared with the blank. The highest values for the hydrolysis constants were obtained at hydraulic retention times of six days after adding 0.1% of yeast extract.
Retention of granular sludge at high hydraulic loading rates in an anaerobic membrane bioreactor with immersed filtration
Authors: Hernández A.E. , Belalcazar L.C. , Rodríguez M.S. , Giraldo E.
Published: May 2018

This study shows the results of an Anaerobic Membrane Bioreactor with immersed filtration cartridges for granular biomass retention working at high hydraulic loading rates. Biomass retention capabilities, granular biomass structure and activity, filtration cartridges flux and organic material degradation performance were evaluated. Four reactors with a volume of 0.005 m3 were tested. Two different filtration cartridges were used (10 and 100 μm) with effective surface area of 0.05 m2. The filtration cartridges were submerged in the reactors for suction type filtration. Three organic loading rates were tested in the first two reactors and seven in the other two. Selective biomass washout and an increment in the biomass methanogenic activity was observed in the reactors at hydraulic loading rates between 1.2 and 4.5 m/h. Analyses of biomass granulometry showed an increase of larger size granular biomass. The immersed membrane anaerobic bioreactor maintain most of the advantages without biomass activity loss.
Effects of aerobic and anaerobic digestion systems on pathogen and pathogen indicator reduction in municipal sludge
Authors: Dahab M.F. , Surampalli R.Y.
Published: May 2018

In this study, the effectiveness of anaerobic treatment systems in reducing pathogenic density levels was evaluated under the US EPA municipal sludge rule (40 CFR Part 503 Rule). Wastewater and sludge samples were analyzed for both pathogens and pathogenic indicator organisms from six different existing wastewater treatment systems. The results indicate that Class B sludge requirements under the US 503 Rule are reasonable and can be achievable by the existing treatment systems while Class A sludge requirements under the same rule may not be easily achieved by the existing treatment systems. The effects of volatile solids loading rates on anaerobic digester performance were investigated. Under anaerobic digestion conditions, it appears that the log reductions in fecal coliform and fecal streptococcus appeared to be dependent on VSS loading rates. On the other hand, Salmonella sp. density reductions did not appear to be dependent on VSS loading rates.
A risk assessment of emerging pathogens of concern in the land application of biosolids
Authors: Gerba C.P. , Pepper I.L. , Whitehead L.F.
Published: May 2018

Since the development of the United States Environmental Protection Agency's 503 biosolids Rule, which includes treatment requirements to reduce the threat of pathogen transmission, many new pathogens have been recognized which could be transmitted by biosolids. A risk analysis was performed to assess which emerging pathogens would be most likely to survive treatments required for Class B biosolids before land application. The literature was reviewed on the resistance of emerging pathogens to temperature and other environmental factors to assess their probability of surviving various biosolids treatment processes. In addition existing information on occurrence in biosolids and dose response models for each pathogen was reviewed. It was concluded that adenoviruses and hepatitis A virus are the most thermally resistant viruses and can survive for prolonged periods in the environment. The protozoan parasites microsporidia and Cyclospora were unlikely to survive the temperatures achieved in anaerobic digestion and do not survive well under low moisture conditions. A risk model was used to assess the risk of infection and illness from enteric viruses after application of class B biosolids.
Coliform and helminth eggs removal in a combined UASB reactor – baffled pond system in Brazil: performance evaluation and mathematical modelling
Authors: von Sperling M. , Chernicharo C.A.L. , Soares A.M.E. , Zerbini A.M.
Published: May 2018

The paper presents the monitoring results of a pilot UASB reactor followed by a baffled polishing pond treating domestic sewage in Brazil. Longitudinal profiles of E. coli and helminth eggs along the baffled pond have been undertaken. The experimental results have been compared with von Sperling's model for coliform removal and Ayres' model for helminth eggs removal, and the fitting was considered satisfactory in both cases. The distribution of the helminth species along the system is also presented.
Measuring metal and phosphorus speciation in P-rich anaerobic digesters
Authors: Carliell-Marquet C.M. , Wheatley A.D.
Published: May 2018

High concentrations of soluble orthophosphate, magnesium and potassium are released during anaerobic digestion of biological phosphorus removal (BPR) sludge. This research was undertaken to investigate the effects of phosphorus enrichment on digester performance, metal and phosphorus speciation. High concentrations of soluble PO4-P (> 250 mg/l) were found to have a retarding effect on anaerobic digestion, reducing the rate of volatile solids digestion and methane production in comparison to control digesters. This was found to be reversible after a period of time, which was related to the amount of PO4-P added to the digesters, higher concentrations of PO4-P requiring more time for digester recovery. Addition of magnesium and potassium to the digesters, together with PO4-P, reduced the inhibitory effect of phosphorus enrichment but these digesters still showed lower rates of volatile solids digestion and methane production in comparison to the control digesters. Phosphorus enrichment resulted in extensive precipitation of calcium, magnesium and manganese, markedly reducing the soluble and easily available fractions of these metals. Other trace metals such as copper, zinc, chromium, nickel and cobalt actually showed increased levels of solubility as a result of phosphorus enrichment. This was thought to be caused by high levels of soluble organic carbon in the phosphorus-rich anaerobic digesters, which acted as organic ligands for metal complexation.
Sludge management regulations and their applicability in mountainous regions
Authors: Wett B. , Becker W. , Ingerle K.
Published: May 2018

The Commission of the European Communities (CEC) is just working out a new directive in order to regulate the agricultural reuse of sewage sludge. This new regulation will also effect a “special case” - sludge usage in a mountainous environment - which will be discussed in this paper. Three reuse sites at small wastewater treatment plants of mountain refuges at altitudes more than 2,000 m a.s.l. are investigated. Applied sludge, soil and drainage flow from lysimeters are analysed. Concerning heavy metal concentrations domestic sewage sludge from these sites differs significantly from municipal sludge. A comparison with background concentrations reveals that no relevant accumulative pollution of the soil is possible. An increase of coliform bacteria of maximum two orders of magnitude is preserved during the long winter period and indicates a limited hygienic risk.
Oxygen-limited nitrogen removal in a lab-scale rotating biological contactor treating an ammonium-rich wastewater
Authors: Pynaert K. , Wyffels S. , Sprengers R. , Boeckx P. , Van Cleemput O. , Verstraete W.
Published: May 2018

A lab-scale Rotating Biological Contactor (RBC) was operated with the purpose of oxygen-limited (autotrophic) nitrification–denitrification of an ammonium-rich synthetic wastewater without Chemical Oxygen Demand (COD). Based on the field observations that RBCs receiving anaerobic effluents come to anoxic ammonium removal, the RBC was inoculated with methanogenic sludge. Some 100 days after the addition of the anaerobic sludge to the reactor as a possible means of a rapid initiation of the nitrogen (N) removal process, a maximum ammonium removal of 1,550 mg N m−2 d−1 was achieved. Batch tests with 15N labeled ammonium and nitrite indicated that a large part of that N was removed via oxygen-limited oxidation of ammonium with nitrite as the electron acceptor. The other part was removed via conventional denitrification, presumably with COD released from lysis of cells. Species identification of the most abundant microorganisms revealed that Nitrosomonas spp. were the dominant ammonium-oxidizers in the sludge. Thus far, the molecular characterization of the sludge could not show the presence of Planctomycetes among the most dominant species. Overall this experiment confirms the property of the RBC system to remove ammonium to nitrogen gas without the use of heterotrophic carbon source.
Rivers of Life: the challenge of restoring health to freshwater ecosystems
Authors: Postel S.
Published: May 2018

The world is moving into a period of widespread water stress and competition,with enormous implications for food security, the health of the aquatic environment,and social and political stability. In the second half of the 20th Century water demand more than tripled,the major factor being irrigation for food production. Over the same period,the number of large dams worldwide climbed from 5,000 to 45,000 - bringing about a major alteration of river hydrology and ecosystem function. Rivers have been disconnected from portions of their channels, their floodplains, their deltas, and from the seas into which they empty. The resulting loss of aquatic habitat has put freshwater life in grave jeopardy. In the 21st Century it will be possible to satisfy the needs of 8-9 billion people while protecting the health of aquatic ecosystems,but only with a fundamental shift in the way society uses, manages and values freshwater. It will likely require a doubling of water productivity over the next 25 years - including more efficient irrigation practices and greater recycling of wastewater. To guide policy, nations need to systematically determine their freshwater ecosystem flow requirements in a way that perhaps only South Africa is attempting so far. Underpinning all these measures is the need for a guiding water ethic that states that enough water should be provided for all living things before some get more than enough.
Dairy farming and river condition: investigating the sustainable use of water resources in an agricultural area
Authors: Christesen L.
Published: May 2018

This paper explores some of the factors that may contribute to the sustainable use of water on irrigated dairy farms in Victoria, Australia. The paper begins with a discussion of the principles of sustainable water use as they would apply to dairy farms in the Gippsland region of Victoria. A series of indicators are used to link aspects of sustainable water use at a regional scale, and the observable trends are discussed. Of particular interest is the way that local river systems contribute to the dairy industry in this region and the aspects of dairying and other significant regional factors that may be impacting on the sustainability of river systems in this area. The indicators are structured and analysed using the Pressure-State-Response (PSR) framework developed by the OECD, most commonly used in State of the Environment reporting. The trends highlighted by the indicator set are discussed in terms of the implications that current patterns of water use may have for possible shifts towards more sustainable water use on individual dairy farms in Gippsland.
Rivers as urban landscapes: renaissance of the Waterfront
Authors: Benson E.
Published: May 2018

The Lake Ontario Waterfront Trail, currently stretching 350 kilometres along the shore of Lake Ontario, Canada, links 26 communities, 184 natural areas, 161 parks and promenades, 84 marinas and yacht clubs, hundreds of historic places, fairs, museums, art galleries and festivals. The Waterfront Trail is a catalyst for a new attitude and way of thinking towards the Lake Ontario waterfront and its watersheds - one that integrates ecological health, economic vitality and a sense of community.

Since it was launched in 1995, the Trail has accompanied the protection of the most valued elements of the waterfront, and the transformation of under-utilized and environmentally degraded lands to vibrant places with businesses and jobs, parks and recreational facilities, green spaces, natural habitats and cultural venues and attractions. It is through the Trail that people have been mobilized to improve the waterfront as they have rediscovered the shoreline and understood the interconnections, both natural and cultural, that are so vital to its health and vitality.

The Waterfront Regeneration Trust is the not-for-profit charitable organization that has been leading this large-scale greenway initiative over the past 10 years. While much has been accomplished, there remains much to do to enhance and expand the greenway. This presentation will focus on the lessons we have learned over the past decade in our involvement with more than 100 projects and what those lessons mean for the next decade of waterfront regeneration.
Community-based stream conservation initiatives in British Columbia, Canada
Authors: Wilson N.
Published: May 2018

British Columbia is a diverse province, with ecosystems ranging from semi-arid deserts to valley glaciers and vast ice fields. By world standards, BC has an abundance of fresh water in its lakes and rivers. However, rivers have been exploited for social and industrial purposes, often to the detriment of the natural values. Community groups and non-government organizations have been active in rehabilitating and restoring waterways.

The Outdoor Recreation Council of BC is a provincial non-government organization that has been instrumental in river conservation issues in BC. Three key initiatives have been established by the Council since its formation in 1975. BC Rivers Day has grown into the largest river celebration of its kind in North America, and there is a move to establish a national Rivers Day in Canada based on the model established in BC. Second is the annual Endangered Rivers List compiled by the Council and released each spring. The third initiative is the River Recovery Project in which dams and impoundment structures were evaluated against a set of criteria. A short list of candidates was generated by the project that will be further studied to determine what actions should be taken to alter the management of the structures to restore ecological values of the rivers and streams on which they are built.

The three initiatives described rely on local community support. The Outdoor Recreation Council of BC provides coordination, promotion, and publicity as well as some resource materials while local groups and communities take on stewardship roles for their local streams. This model may be useful for other jurisdictions.
Environmental action for community monitoring
Authors: Kingham N.
Published: May 2018

Community monitoring began in Australia in the 1980s primarily as an awareness-raising tool. Since that time, the community has developed increased skills and knowledge in monitoring procedures and both the data collectors and data users are placing greater demands on community data to be accurate and reliable. With over 3,500 community groups in the field collecting data at over 5,000 sites across Australia, the Waterwatch Program has developed guidelines and tools for monitoring and data collection for the community to collect reliable, accurate and useful data. This paper will discuss how Waterwatch is providing technical support through a range of data confidence guidelines and procedures to ensure that community monitoring and community data continue to play a significant role in the protection and management of our waterways. This paper will also draw on a couple of case studies from across Australia that demonstrate community data being used by a variety of stakeholders.
Impacts of water management options on flows in the Condamine River in Southern Queensland
Authors: Porter J.W.
Published: May 2018

This paper examines the implications for river flows of a number of water practices and potential management options in the alluvial plains of the Upper Condamine River. It is an intensively cultivated area where irrigation is limited by the availability of water resources. The practice of capturing overland flows was investigated by the development of a model that simulates the performance of clusters of offstream storages up to sub-catchment scale. Management options examined included improvement to on-farm water use efficiency, the suppression of evaporation from open water storages, increasing the depth of those storages, decreasing their number, and improved tailwater return from irrigated land. Impacts of management options were analysed using a catchment scale water allocation model.
Appropriate basis of effluent standards for industrial wastewaters
Authors: Tilche A. , Orhon D.
Published: May 2018

Designing industrial discharge standards should reflect the numerical compromise between what can be achieved to prevent environmental pollution and sustainable development. They should involve categorical limitations for specific sources. Micropollutants represent the major concern for industrial effluents. A micropollutant-based subcategorization is needed for an effective control of industrial effluents. Regulations imposed require a comprehensive knowledge of polluting processes and sources, and technological limits of available treatment technologies.
High-rate methane fermentation of lipid-rich food wastes by a high-solids co-digestion process
Authors: Li Y.Y. , Sasaki H. , Yamashita K. , Seki K. , Kamigochi I.
Published: May 2018

This paper presents an experimental study on anaerobic degradation of lipids-rich food wastes by using the high solids co-digestion process. The experiments were conducted under mesophilic (35°C) and thermophilic (55°C) condition, respectively, by using a semi-continuous flow completely mixed reactor. The influent TS level was controlled at around 10%, while the hydraulic retention time (HRT) was changed from 15 days to 7.5 days. The lipids (fats or oil and grease) content in the influent TS was changed from 8% to 40% by adding salad oil (vegetable) and lard (animal) to the food wastes. The result of this study showed that the food wastes containing high lipids content was effectively degraded by the high solids co-digestion process and over 85% of lipid was degraded to biogas with 60-65% of methane. In addition, thermophilic methane fermentation was more effective for reducing lipids and had more higher loading capacity compared with mesophilic condition.
Effect of dissolved oxygen conditions on nitrogen removal in continuously fed intermittent-aeration process with two tanks
Authors: Hidaka T. , Yamada H. , Kawamura M. , Tsuno H.
Published: May 2018

In this study, an intermittent aeration type activated sludge process that is fed continuously is evaluated for nitrogen and organic carbon for facilities in rural areas, which are characterized by small scale, low loading rate and automatic operation. Anoxic and aerobic conditions can be regulated alternatively by intermittent aeration for biological nitrogen removal. It is proved that an intermittent aeration cycle of 90 min, with aeration/anoxic mixing periods of 25~30 min/65~60 min in Tank 1, and 30~45 min/60~45 min in Tank 2, and a DO control set at 0.6~1 mg/L during the aeration period are required for satisfactory treatment performance. Under these conditions, a stable effluent water quality with BOD ≤ 5 mg/L, CODMn ≤ 8 mg/L, Nitrogen ≤ 3 mgN/L, SS ≤ 5 mg/L and transparency ≥ 80 cm can be achieved. The solids retention time in aerobic condition was 10~25 d, which is sufficient for nitrification.
Assessment of source-based nitrogen removal alternatives in leather tanning industry wastewater
Authors: Zengin, G. , Ölmez T. , Doğruel S. , Kabdaşlı I. , Tünay O.
Published: May 2018

Nitrogen is an important parameter of leather tanning wastewaters. Magnesium ammonium phosphate (MAP) precipitation is a chemical treatment alternative for ammonia removal. In this study, a detailed source-based wastewater characterisation of a bovine leather tannery was made and nitrogen speciation as well as other basic pollutant parameter values was evaluated. This evaluation has led to definition of alternatives for source-based MAP treatment. MAP precipitation experiments conducted on these alternatives have yielded over 90% ammonia removal at pH 9.5 and using stoichiometric doses. Among the alternatives tested liming-deliming and bating-washing was found to be the most advantageous providing 71% ammonia removal.
Modelling of a recirculating granular medium filter's processes
Authors: Boutin C. , Parouty R. , Ménoret C. , Liénard A. , Brissaud F.
Published: May 2018

The effluents of French small farm factories will soon be submitted to regulation. Only a few treatment techniques are available to deal with these kind of effluent (high concentration and small daily volumes). To allow the treatment, in the particular economic context of small food processing industries, Cemagref is trying to adapt a treatment based on attached growth cultures on fine media, a system known to be easy to operate and relatively inexpensive. A model, based on four sub-models (hydrodynamic characteristics, oxygen transport, solute transport in the mobile and immobile phases and bacterial evolution) describes this process. Based on wastewater concentration, hydraulic load, applied organic loads, feeding / rest cycles and recycling phases number, this model predicts:•eliminated organic loads and the discharge concentration as a function of time,•oxygen and biomass contents as a function of time and depth. The determination of the model's parameters is based on a comparison between simulations and performances achieved on experimental columns. This model would be helpful in sizing full-scale filters treating different types of agro-food wastewater. The aim of this article is to present the model's structure, to give all parameter values and to compare the simulations with the results obtained on pilot and full scale plants.
In-plant control applications and their effect on treatability of a textile mill wastewater
Authors: Dulkadiroglu H. , Eremektar G. , Dogruel S. , Uner H. , Germirli-Babuna F. , Orhon D.
Published: May 2018

Water minimization and exploration of the potential for wastewater recovery and reuse are priority issues of industrial wastewater management. They are extremely significant for the textile industry commonly characterized with a high water demand. The study presents a detailed in-plant control survey for a wool finishing plant. A comprehensive process profile and wastewater characterization indicate that process water consumption can be reduced by 34%, and 23% of the wastewater volume can be recovered for reuse. Treatability of reusable wastewater fraction and the effect of in-plant control applications on effluent treatability were also investigated.
Treatment of dairy waste by using water hyacinth
Authors: Trivedy R.K. , Pattanshetty S.M.
Published: May 2018

In the present study treatment of wastewater from a large dairy by using water hyacinth was studied in laboratory experiments. Effects of depth of the system, variations in area coverage, prior settling and of daily renewal of the plants was also studied on the efficacy of hyacinth in treating the dairy waste. Water hyacinth (Eichhornia crassipes) was found to grow exceptionally well in the waste (BOD 840.0 mg/L) and brought down the level of BOD from 840.0 to 121.0 mg/L; COD from 1,160.0 to 164.0 mg/L, total suspended solids from 359.0 mg/L to 245.0 mg/L, TDS from 848.0 mg/L to 352.0 mg/L, total nitrogen from 26.6 mg/L to 8.9 mg/L in 4 days. There was very little reduction, however in calcium, sodium and potassium concentration. Results of different experiments showed that systems with shallow depth were more efficient in removing dissolved solids, suspended solids, BOD, COD, nitrogen and phosphorus. Daily renewal of the plants led to slightly better reduction in suspended and dissolved solids, BOD, COD and nitrogen. Water hyacinth coverage was found to have a direct bearing on the treatment efficiency. Pretreatment (settling) of the waste was also found to be favourable as dissolved oxygen content increased rapidly in the experimental sets with pretreatment. Efficiency of removal of various parameters was also good in these sets. From the study it can be concluded that dairy waste can be effectivily treated by water hyacinth. Consideration of above parameters and incorporating them in design factors can greatly increase the efficiency of the system.
Microbial population dynamics in laboratory-scale activated sludge reactors
Authors: Kaewpipat K. , Grady C.P.L.
Published: May 2018

As a first step in understanding nonlinear dynamics in activated sludge systems, two laboratory-scale sequencing batch reactors were operated under identical conditions and changes in their microbial communities were followed through microscopic examination, macroscopic observation, and denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene segments from the prokaryotic community. Two experiments were performed. The first used activated sludge from a local wastewater treatment plant to start the replicate reactors. The second used the biomass from the first experiment as a source by intermixing the two and equally redistributing the biomass into the two replicate reactors. For both experiments, the two reactors behaved fairly similarly and had similar microbial communities for a period of 60 days following start-up. Beyond that, the microbial communities in the two reactors in the first experiment diverged in composition, while those in the second experiment remained fairly similar. This suggests that the degree of change occurring in replicate reactors depends upon the severity of perturbation to which they are exposed. The DGGE data showed that the bacterial communities in both experiments were highly dynamic, even though the system performance of the replicate reactors were very similar, suggesting that dynamics within the prokaryotic community is not necessarily reflected in system performance. Moreover, a significant finding from this study is that replicate activated sludge systems are not identical, although they can be very similar if started appropriately.
Phylogenetic analysis and in situ identification of “Nostocoida limicola”-like filamentous bacteria in activated sludge from industrial wastewater treatment plants
Authors: Snaidr J. , Beimfohr C. , Levantesi C. , Rossetti S. , van der Waarde J. , Geurkink B. , Eikelboom D. , Lemaitre M. , Tandoi V.
Published: May 2018

The diversity of filamentous bacteria present in industrial wastewater treatment plants was analysed by a combination of classical and molecular-biological approaches. Many unknown filamentous bacteria were observed in about 80 screened activated sludge samples from different industries with sometimes severe bulking sludge problems. A special focus was paid to filaments which resembled “Nostocoida limicola”, a filamentous bacterium which was found to be present in many WWTPs. These filamentous bacteria are hardly cultivable and only one strain was obtained and maintained in co-culture with a yeast. The 16S rRNA sequences of several other “Nostocoida limicola”-like filamentous bacteria from different sludge samples were obtained by micromanipulation and different molecular-biological methods. The sequences were phylogenetically analyzed and specific molecular probes were developed and applied. The results clearly demonstrate that “Nostocoida limicola”-like filaments from industrial WWTPs are different from all other “Nostocoida limicola” types investigated so far. Our strains are affiliated to the alpha-subclass of Proteobacteria.
Characterization of type 1851 organism isolated from activated sludge samples
Authors: Kohno T. , Sei K. , Mori K.
Published: May 2018

Five orange pigmented filamentous strains of Eikelboom's type 1851 were isolated from bulking activated sludge, and were examined for their phylogenetic lineage, morphology, and physiology. The analysis of 16S rDNA sequence revealed that the isolates belong to Chloroflexus subdivision in green non sulfur bacteria. They shared most common features with type 1851, but the result of Gram stain was negative. Furthermore, they showed polymorphic nature and gliding motility, which could not be seen in activated sludge samples. General physiological tests were conducted under aerobic conditions although they could also grow by fermentation. Good growth was generally seen on sugars. The extremely slow growth rate (0.48–0.93 day−1) suggests the stimulation of this type exclusively in long SRT systems fed with sugars.
Phylogenetic and physiological diversity of tetrad-forming organisms in deteriorated biological phosphorus removal systems
Authors: Tsai C.-S. , Liu W.-T.
Published: May 2018

Polyhydroxyalkanoate (PHA)- and polyphosphate-accumulating traits of different taxonomic tetrad-forming organisms (TFOs) in two anaerobic-aerobic sequential batch reactors (SBRs) were characterized by the simultaneous use of fluorescence in-situ hybridization, PHB stain and DAPI stain. The two SBRs with glucose as the main carbon source were operated under different P:total organic carbon feeding ratios for more than 300 days, but both exhibited no enhanced biological phosphorus removal (EBPR) activity. Microscopic observations on sludge samples taken at various times from those two SBRs revealed that TFOs consistently accounted for more than 50% of total cells, and were mostly affiliated with the β- and γ-subclasses of Proteobacteria and the high G+C phylum of Gram-positive bacteria (HGC). Those TFOs from the β-Proteobcateria exhibited PHB stain positive and DAPI stain negative, indicating that they could utilize compounds other than polyphosphate (i.e. glycogen) as reducing power for PHA synthesis from glucose. In contrast, two types of TFOs within the HGC group showed negative PHB stain and positive DAPI stain, indicating their capacity to accumulate polyphosphate without the synthesis and degradation of PHA. This metabolic trait was different from the widely accepted biochemical model of EBPR and non-EBPR metabolisms. Other TFOs within the HGC group and γ-Proteobacteria showed negative responses to both PHA and DAPI stains, and their function in the deteriorated EBPR system need to be further clarified. Overall findings suggested that the phylogenic and physiological heterogeneity of TFOs in anaerobic-aerobic activated sludge systems were diverse and greatly exceeded the current understanding.
Density separation and molecular methods to characterize enhanced biological phosphorus removal system populations
Authors: Schuler A.J. , Onuki M. , Satoh H. , Mino T.
Published: May 2018

A novel approach to the identification of microorganisms that accumulate high density microbial storage products based on density separation, denaturing gradient gel electrophoresis (DGGE), and DNA sequencing was developed and applied to bench and pilot scale enhanced biological phosphorus removal (EBPR) systems. Polyphosphate (PP), glycogen, and polyhydroxyalkanoates (PHAs), are all of higher density than a typical bacterial cell. PP-accumulating organisms (PAOs), the organisms responsible for EBPR, accumulate all three of these storage products. Density separation in a homogenous solution of Percoll produced a high-density biomass fraction with a relatively high concentration of PAOs, as determined by Neisser staining. DNA was extracted from these fractions, amplified, and separated by DGGE. DGGE profiles demonstrated some bacterial strains were present at a greater concentration in the high density fractions than in low density fractions. These strains were considered PAO candidates. 5 of 12 PAO candidates from high density fractions were γ Proteobacteria and only 1 was a β Proteobacterium. 2 PAO candidates were most similar to recently identified γ Proteobacteria sequences obtained by DGGE analysis of a deteriorated benchtop EBPR system.
In situ identification of azo dye inhibition effects on nitrifying biofilms using microelectrodes
Authors: Li J. , Bishop P.L.
Published: May 2018

In this study, the inhibitory effects of acid orange 7 (AO7), a common azo dye, on nitrification in biofilms were investigated in situ using microelectrodes. Biofilms were obtained from laboratory rotating drum biofilm reactor after the nitrification process reached a pseudo-steady state. Dissolved oxygen, pH, NH4+, NO3−, and redox potential microelectrodes, with tip diameters ranging from 3–15 μm, were used to monitor the spatial distribution and change of microbial activities within nitrifying biofilms. It was found that at lower concentration (1 mg/L), AO7 had only a slight impact on the NH4+-N concentration profiles. The ammonium consumption rate decreased as higher AO7 concentrations (15 mg/L and 25 mg/L) were exposed to the biofilms. A similar trend was observed for the NO3−-N microprofiles. The nitrate production rate decreased as the AO7 concentration in the bulk solution increased. The dissolved oxygen and pH microprofiles also showed oxygen and alkalinity utilization, but at lower rates throughout the biofilms when the nitrification process was inhibited. No significant redox potential differences were observed in the biofilms after AO7 was applied.
Production of gaseous nitrogen compounds in a novel process for ammonium removal
Authors: Green M. , Denekamp N. , Lahav O. , Tarre S.
Published: May 2018

The production of gaseous nitrogen compounds, particularly the greenhouse gas nitrous oxide, was investigated in a novel process for ammonium removal from wastewater. The process is based on the adsorption of ammonium on zeolite followed by bioregeneration. The zeolite serves the dual purpose of an ion exchanger and a physical carrier for nitrifying bacteria which bio-regenerate the ammonium saturated mineral. An analysis of the nitrifying population composition in the reactor fed with simulated secondary effluent (NH4+ = 50 mg/l) revealed that about half of the bacteria in the biofilm were common ammonium oxidizers Nitrosococcus mobilis and Nitrosomonas, while the other half were nitrite oxidizers.

The amount of nitrogen losses, under different conditions, and the identification of the emitted gases (N2 or N2O) were investigated in two sets of experiments: (I) batch experiments using biomass originating from the ion exchange reactor with and without the addition of nitrite, and (II) continuous experiments using the ion exchange reactor with zeolite as the biomass carrier. In the batch experiments, nitrite and oxygen concentrations were determined as the major parameters responsible for the formation of gaseous nitrogen gas during ammonia oxidation by autotrophic bacteria. Continuous experiments showed that the major parameter significantly affecting nitrogen losses was the amount of ammonium adsorbed by the zeolite during the ion exchange phase. The amount of ammonium adsorbed determines the ammonium concentration during the initial period of bioregeneration, which in turn directly influences oxygen demand and the resulting concentrations of oxygen and nitrite. It was concluded that the formation of nitrogen gas compounds in the ion exchange/bioregeneration process can be eliminated by adjusting the operational regime to have a shorter adsorption phase resulting in smaller amounts of ammonium adsorbed per cycle.
Detection and quantification of expression of amoA by competitive reverse transcription-PCR
Authors: Ebie Y. , Miura H. , Noda N. , Matsumura M. , Tsuneda S. , Hirata A. , Inamori Y.
Published: May 2018

Ammonia oxidation by chemolithoautotrophic ammonia-oxidizing bacteria is an important step in the biological nitrogen removal process. The first conversion step, the oxidation of ammonia to hydroxylamine is catalyzed by ammonia monooxygenase (AMO). To investigate the activity of ammonia oxidation, mRNA (designated as amoA) encoding a subunit of AMO was quantified by competitive reverse transcription (RT)-PCR. As a result, it was possible to detect and quantify amoA expression in cultured Nitrosomonas europaea and even complex microbial communities such as nitrifying bacterial aggregates by competitive RT-PCR. It was estimated that amoA concentration in cultured N. europaea was 2.3 × 108 copies·ml−1. Additionally, it was calculated that the copy number of amoA in nitrifying bacterial aggregates was 1.0 × 1012 copies·ml−1 (5.1 × 1010 copies·mg−1-dry weight). On the other hand, amoA expression in the natural activated sludge in a household Gappei-Johkaso was undetectable, whereas 16S rRNA of ammonia-oxidizing bacteria was detected by RT-PCR. Then, four days cultivation of this sludge in inorganic artificial wastewater resulted in increasing amoA expression to a quantifiable amount by competitive RT-PCR. In conclusion, the competitive RT-PCR was effective to investigate the expression of amoA as an indicator of ammonia oxidation activity by autotrophic ammonia-oxidizing bacteria.
Comparison of bench scale testing methods for nitrifier growth rate measurement
Authors: Katehis D. , Fillos J. , Carrio L.A.
Published: May 2018

The maximum specific nitrifier growth rate was determined for two wastewater treatment plants (WWTPs) using sequencing batch reactors (SBRs) and high F/M exponential growth batch tests. Higher nitrifier growth rates were obtained from the exponential growth batch tests. Operating SRT and aeration mode (fully aerobic versus anoxic/aerobic) significantly impacted the nitrifier's growth rate in the SBRs with lower SRT and anoxic/aerobic operation resulting in higher specific nitrifier growth rates.
Evaluation of autotrophic denitrification, heterotrophic nitrification, and PAOs in full scale simultaneous biological nutrient removal sysyems
Authors: Littleton H.X. , Daigger G.T. , Strom P.F. , Cowan R.M.
Published: May 2018

Anoxic and aerobic batch reactor assays using a two-by-two factorial design were developed to determine the potential activity of autotrophic denitrification and heterotrophic nitrification in biological nutrient removal (BNR) activated sludge systems, especially those accomplishing simultaneous BNR (SBNR). Results from the application of these assays to three full scale closed loop bioreactors previously documented to be accomplishing SBNR demonstrated that these activities were minimal in comparison with the conventionally recognized activities of heterotrophic denitrification and autotrophic nitrification. Activity within the mixed liquor consistent with current theories for phosphorus accumulating organisms (PAOs) was also observed. Along with other observations, this suggests the presence of PAOs in the facilities studied.
PCR-DGGE analysis of denitrifying bacteria in a metallurgic wastewater treatment process
Authors: Noda N. , Yoshie S. , Miyano T. , Tsuneda S. , Hirata A. , Inamori Y.
Published: May 2018

The wastewater generated from the processes of recovering precious metals from industrial wastes contains high concentrations of acids such as nitric acid and of salts. Biological nitrogen removal from this wastewater was attempted by using a circulating bioreactor system equipped with an anoxic packed bed or an anoxic fluidized bed and an aerobic three-phase fluidized bed. The system was found to effectively remove nitrogen from the diluted wastewater (T-N; 1,000–4,000 mg litre−1). The microbial population structure of activated sludge in an anoxic reactor was analyzed by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA (rDNA) fragments. DGGE analysis under different operating conditions demonstrated the presence of some distinguishable bands in the separation pattern, which were most likely derived from many different species constituting the microbial communities. Furthermore, the population diversity varied in accordance with the nitrate-loading rate, water temperature and reactor condition. Some major DGGE bands were excised, reamplified and directly sequenced. It was revealed that the dominant population in the anoxic reactor were affiliated with the β subclass of the class Proteobacteria.