bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of mathematical models in teaching wastewater treatment engineering
Authors: Morgenroth E. , Arvin E. , Vanrolleghem P.
Published: May 2018

Mathematical modeling of wastewater treatment processes has become increasingly popular in recent years. To prepare students for their future careers, environmental engineering education should provide students with sufficient background and experiences to understand and apply mathematical models efficiently and responsibly. Approaches for introducing mathematical modeling into courses on wastewater treatment engineering are discussed depending on the learning objectives, level of the course and the time available.
Problems of modern urban drainage in developing countries
Authors: Silveira A.L.L.
Published: May 2018

Socio-economic factors in developing countries make it more difficult to solve problems of urban drainage than in countries that are more advanced. Factors inhibiting the adoption of modern solutions include: (1) in matters of urban drainage, 19th-century sanitary philosophy still dominates; (2) both legal and clandestine land settlement limits the space that modern solutions require; (3) contamination of storm runoff by foul sewage, sediment and garbage prevents adoption of developed-country practices; (4) climatic and socio-economic factors favour the growth of epidemics where runoff is retained for flood-avoidance and to increase infiltration; (5) lack of a technological basis for adequate drainage management and design; (6) lack of the interaction between community and city administration that is needed to obtain modern solutions to urban drainage problems. Awareness of these difficulties is fundamental to the search for modern and viable solutions appropriate for developing countries.
PID and PLC units for the real-time control of sewer systems
Authors: Campisano A. , Modica C.
Published: May 2018

Moveable gates for the real-time control (RTC) of sewer systems storage capacities are usually operated by controllers which, on the basis of local water level or flow velocity measurements, calculate the regulation errors of the monitored variables, determining the necessary regulator movements to lead the flow conditions to the desired set point.

In this paper the results of an investigation on the influence of proportional-integral-derivative (PID) controllers and programmable logic controllers (PLC) for the RTC of moveable sluice gates positioned into sewer systems are presented. The analysis of response time, damping and regulation errors provided information on the PID parameter calibration values and on the PLC control function performances.

A comparison between the two kind of controllers has also been carried out.
Nutrient fluxes from the Danube Basin to the Black Sea
Authors: Zessner M. , van Gils J.
Published: May 2018

This paper deals with the state of the art of quantification of sources, pathways and sinks of nutrients in the Danube Basin and their transport from the catchment to the Black Sea. It shows main results of emission estimates to surface waters and the Danube Water Quality Model approach to link these emissions estimates to measured water monitoring data. The current paper provides a quantitative synthesis of available knowledge regarding the fate of nutrients in the Danube Basin. Even though many knowledge gaps existed, our understanding of the system has increased. As such, the paper provides a vehicle to carry the discussion one step beyond just complaining about how much we do not know yet.
Retrofitting activated sludge systems to intermittent aeration for nitrogen removal
Authors: Hanhan O. , Artan N. , Orhon D.
Published: May 2018

The paper provides the basis and the conceptual approach of applying process kinetics and modelling to the design of alternating activated sludge systems for retrofitting existing activated sludge plants to intermittent aeration for nitrogen removal. It shows the significant role of the two specific parameters, namely, the aerated fraction and the cycle time ratio on process performance through model simulations and proposes a way to incorporate them into a design procedure using process stoichiometry and mass balance. It illustrates the effect of these parameters, together with the sludge age, in establishing the balance between the denitrification potential and the available nitrogen created in the anoxic/aerobic sequences of system operation.
Activated carbon and residual nitrification for higher quality effluents for the coastal areas
Authors: Beler-Baykal B. , Witte G. , Sekoulov I.
Published: May 2018

Efforts for the task of modification of a nitrification/denitrification unit operating in a series of two fixed bed columns are outlined. The problem was elevated dissolved oxygen concentrations at the entrance of the denitrification column, resulting in an excessive consumption of methanol. The possibility of using a column of activated carbon for adsorption alone and in which both adsorption and residual nitrification take place was investigated. The results were observed to be very satisfactory in reducing dissolved oxygen levels to practically zero at the entrance of the denitrification unit especially for the case where both adsorption and residual nitrification were employed.
Significance of wetlands in water quality management - past and present situation of Kizilirmak Delta, Turkey
Authors: Samsunlu A. , Akca L. , Kinaci C. , Findik N. , Tanik A.
Published: May 2018

Wetlands are of utmost importance in the sense of protecting the natural ecological balance of the environment. It is possible to improve the water quality of wetlands, which are located in coastal areas like river deltas and lakes without disturbing the ecological balance through rehabilitation and by controlling. However, many wetlands in the world have so far been dried and converted to agricultural areas due to insufficient knowledge of their ecological value. Such an understanding was also held as true in Turkey and most of its wetlands have been converted to agricultural land till recent years. An example of such an occurrence and modifications within years are observed in the delta of the Kizilirmak River, which is the longest river of Turkey ending in the Black Sea. The past and present situation of the Kizilirmak delta will be investigated in this paper together with the changes in water quality. An evaluation of the water quality of the river and of lakes within the delta is done based on available previous data and on the final findings of water quality measurements conducted within the framework of this study.
Life-cycle assessment as an environmental management tool in the production of potable water
Authors: Friedrich E.
Published: May 2018

The environmental life cycle assessment (LCA) methodology was used in this study to calculate and compare the environmental burdens resulting from two different methods employed in the production of potable water in South Africa. One method employs conventional processes for the treatment of water and the other one is based on membrane filtration. All inputs (raw materials and energy) and outputs (products, by-products and emissions to air, water and soil) from the two methods were listed and quantified. These inputs and outputs cause different environmental impacts (global warming, ozone depletion, smog formation, acidification, nutrient enrichment, ecotoxicity and human toxicity) and the contribution of each method to each of these impact categories has been quantified, resulting in a score. The ISO (International Organisation for Standardisation) methodological framework for life cycle assessments guided this study. By using these methodologies and by tracing all the processes involved in the production of potable water to the interface with the environment, it was found that the main contributor to the overall environmental burden is the generation of electricity. This conclusion is valid for both methods investigated and in order to increase the environmental performance in the production of potable water the energy efficiency of waterworks should be increased.
Geochemical and isotopic tracing of water in nested southern Minnesota corn-belt watersheds
Authors: Magner J.A. , Alexander S.C.
Published: May 2018

Land-use changes over the last century in southern Minnesota have influenced riverine water chemistry. A nested watershed approach was used to examine hydrologic pathways of water movement in this now agriculturally intensive region. From field scale subsurface tile-drains of the Beauford ditch to the respective outlets of the Cobb River and Blue Earth River, more than 125 samples were collected for major dissolved ions and isotopes between March 1994 and June 1996 over a range of climatic conditions that included snowmelt and storm-flows. Results indicate that riverine water chemistry is dominated by subsurface tile-drained row crop agriculture. In the mid-1990s, regional ground water discharge into the Cobb and Blue Earth Rivers comprised less than 10% of the total flow based on ionic mixing calculations. Ammonia, present in manure or as anhydrous, is readily exchanged in the soil. This ion exchange releases increasing ratios of magnesium, sodium and strontium relative to calcium, the dominant cation. Soil thaw and snowmelt recharge influenced March–April tile-drain and ditch water isotopic values. Light δD values increased as spring infiltration-derived water was displaced from the soil zone by heavier summer precipitation. δ15N followed a similar but opposite pattern with relatively heavy March–April tile-drain and ditch values trending to lighter δ15N through the growing season. The future of southern Minnesota riverine water quality is closely linked to the management of the landscape. To improve the riverine environment, land owners and managers will need to address cropping systems, fertilization practices and drainage.
Life cycle assessment of an industrial water recycling plant
Authors: Pillay S.D. , Friedrich E. , Buckley C.A.
Published: May 2018

An industrial water recycling plant was recently commissioned in Durban, South Africa. As with any industrial activity there are environmental burdens associated with water recycling. To assess these burdens a relatively new environmental tool - the life cycle assessment (LCA) - was used. LCA is a systematic way to evaluate the environmental impact of a product or process. This study presents the environmental burdens associated with industrial water and identifies the areas for improvement for the processes involved for recycling water. It was shown that the majority of the environmental burdens for producing industrial water could be traced back to the consumption of electricity for the operation of the plant.
Design considerations for increased sedimentation in small wetlands treating agricultural runoff
Authors: Braskerud B.C.
Published: May 2018

Some suggestions to increase the sedimentation of non-point source pollution in small surface flow wetlands are presented. The recommendations are based on results from seven Norwegian constructed wetlands (CWs) after 3–7 years of investigation, and a literature review. The wetlands were located in first and second order streams. Surface areas were 265–900 m2, corresponding to 0.03–0.4% of the watershed. Each CW had a volume proportional composite sampler in the inlet and outlet, in addition to sedimentation plates. The mean annual retention of soil particles, organic particles and phosphorus was 45–75%, 43–67% and 20–44%, respectively. Results showed that erosion and transportation processes in arable watersheds influenced the retention. Sedimentation was the most important retention process, and increased with runoff, because the input of larger aggregates increased. Retention of nitrogen did not follow the same pattern, and was only 3–15%. Making CWs shallow (0–0.5 m) can optimize sedimentation. The hydraulic efficiency can be increased by aquatic vegetation, large stones in the inlet, baffles and water-permeable, low dams. Vegetation makes it possible to utilize the positive effect of a short particle settling distance, by hindering resuspension of sediments under storm runoff conditions. As a result, the phosphorus retention in shallow CWs was twice that of deeper ponds.
Wetland management to reduce Baltic Sea eutrophication
Authors: Paludan C. , Alexeyev F.E. , Drews H. , Fleischer S. , Fuglsang A. , Kindt T. , Kowalski P. , Moos M. , Radlowski A. , Stromfors G. , Westberg V. , Wolter K.
Published: May 2018

Seven regions with coastal eutrophication problems in the Baltic Sea, including the Kattegat, constitute the BERNET project (Baltic Eutrophication Regional Network). To counteract eutrophication and associated severe biological conditions the countries around this large brackish water body must all cooperate. The regions are characterized by large differences in land use, e.g. agricultural intensity, and losses of retention capacity in the catchments due to wetland reclamation. Initially it has been necessary to identify nutrient sources – especially nitrogen – and technical, economical and even administrative obstacles to initiate eutrophication management measures. Nitrogen retention in different types of wetlands in the Baltic Sea Region has been analysed. The wetlands generally have a positive effect on reduced nitrogen transport to aquatic environments and it is generally accepted that measures leading to decreased losses of nutrients to the aquatic environment must be combined with measures leading to increased retention of nutrients in catchments. Data analysed in the BERNET project show that the potential for such a measure is large. Therefore, conservation and restoration initiatives for wetlands is an essential part of the work in the BERNET project. Wetlands have been drained or totally eliminated due to intensive agriculture in some regions while large scale rehabilitation of wetlands occurs in regions with less intensive agriculture. Based on land use data from the seven regions, the working group for wetland management within the BERNET project has identified the possible use of wetlands as building blocks as a contribution to the management of the Baltic Sea eutrophication. Several recommendations are presented on the wise use of existing and constructed wetlands for water quality management in relation to non-point nutrient pollution.
A computational fluid dynamic and experimental study of an ozone contactor
Authors: Huang T. , Brouckaert C.J. , Docrat M. , Pryor M.
Published: May 2018

A computational fluid dynamic (CFD) model of an ozone contacting chamber in the Umgeni Water Wiggins Waterworks in Durban, South Africa, has been set up and verified by experimental tracer tests, as part of an investigation to optimise the control and disinfection efficiency of the contactor. The effect of gas injection was modelled by increasing the turbulent intensity at the reactor inlet. Experimental tracer responses which were used as partial verification of the model correspond very closely to model predictions.
Characterization and mass load estimates of organic compounds in agricultural irrigation runoff
Authors: Pedersen J.A. , Yeager M.A. , Suffet I.H.
Published: May 2018

Investigations of agricultural chemicals in surface runoff typically target nutrients or specific pesticides; however, numerous other organic compounds are regularly applied to agricultural fields in pesticide formulations, irrigation water, soil amendments and fertilizers. Many of these compounds have toxicological significance. We conducted a broad spectrum analysis of surface runoff from individual irrigated agricultural fields in coastal southern California to characterize organic compounds amenable to analysis by gas chromatography-mass spectrometry and to estimate the mass flux of selected chemicals. Aqueous phase extracts contained several pesticides, as well as personal care product ingredients and pharmaceutically active compounds apparently derived from treated wastewater used for irrigation. Several compounds potentially associated with pesticide adjuvants were also present in aqueous phase extracts. Dissolved NOM constituents in water phase extracts included n-fatty acids, aliphatic alcohols and plant terpenoids. Tentatively identified compounds sorbed to suspended particles included pesticides, a fecal sterol, aliphatic and alicyclic hydrocarbons, aliphatic alcohols, aldehydes, and C14 and C16n-fatty acids and fatty acid esters. Bicyclic and polycyclic aromatic hydrocarbons were identified in both aqueous and suspended particle phases. Constituent concentrations, including total suspended solids (TSS), varied over the course of the sampled events by up to an order of magnitude, and typically were not correlated with flow. Variation in sorbed organic compound concentrations often did not parallel those for TSS concentration. Mass load estimates were strongly influenced by the choice of sampling interval.
Use of simulation mass balance modeling to estimate phosphorus and bacteria dynamics in watersheds
Authors: Cassell E.A. , Meals D.W. , Aschmann S.G. , Anderson D.P. , Rosen B.H. , Kort R.L. , Dorioz J.M.
Published: May 2018

Dynamic simulation technology is integrated with mass balance concepts and compartment-flux diagramming to create computer models that estimate contaminant export from watersheds over long and short-term futures under alternative simulated policies of watershed management. The Watershed Ecosystem Nutrient Dynamics (WEND) model, applied to developed watersheds with a mix of urban, agricultural, and forest land-uses, predicted phosphorus (P) export from three watersheds; a 275,000 ha dairy/urban watershed, a 77,000 ha poultry/urban watershed, and a 23,000 ha swine dominated watershed. Urban, agricultural, and forestry activities contribute to P export in different proportions. In all cases the P imports to the watershed exceed total export and P accumulates in watershed soils. Long-term future P export patterns are compared for several watershed management strategies that range from encouragement of rapid urban growth to aggressive environmental protection. The specific response of each watershed to imposed management is unique, but management strategies designed to reduce export of P over the long-term need to consider options that promote P input/output balance. Using this same approach, the Watershed Ecosystem Bacterial Dynamics (WEBD) model assesses the dynamics of bacterial populations in a small case-study watershed over an annual cycle as influenced by dairy farm management actions. WEND and WEBD models integrate the diversity of activities and stakeholders interested in the watershed and promote development of a more holistic understanding of watershed function. Model outputs are designed to assist watershed policy-makers, managers, and planners to explore potential future impacts of management/policy decisions.
SIMPLE: Assessment of non-point phosphorus pollution from agricultural land to surface waters by means of a new methodology
Authors: Schoumans O.F. , Mol-Dijkstra J. , Akkermans L.M.W. , Roest C.W.J.
Published: May 2018

In the past, environmental Phosphorus (P) parameters like soil P indices have been used to catogorize the potential risk of P losses from agricultural land. In order to assess the actual risk of P pollution of groundwater and surface waters, dynamic process oriented soil and water quality models have been frequently used. Recently, an approximating model for phosphorus, called SIMPLE, has been developed. This model approximates the output from a complex dynamic water quality model. The approximating model is called a metamodel. This simple P-model proves to be a powerful tool for quick assessment of the risk of P pollution from agricultural land to surface waters.
Assessment of the denitrification potential for biological nutrient removal processes using OUR/NUR measurements
Authors: Sözen S. , Artan N. , Orhon D. , Avcioglu E.
Published: May 2018

The denitrification potential, a key parameter in nutrient removal activated sludge systems, is mathematically described in terms of mass balance expressions for different carbon sources, namely, easily biodegradable substrate, slowly biodegradable substrate and biomass. Mass balance was derived both for single-anoxic (pre-denitrification) and dual anoxic (Bardenpho) systems. Correction factors for anoxic growth were experimentally determined using respirometry for domestic sewage and meat processing wastewater. The denitrification potential expressions were evaluated for different process configurations such as pre-denitrification, Bardenpho process and University of Cape Town (UCT) process.
Characterization of surface runoff in urban areas
Authors: Choe J.S. , Bang K.W. , Lee J.H.
Published: May 2018

Water quality measurements of surface runoff have been carried out in selected residential and industrial zones in urban areas, in which yearly mean precipitation is 1,225 mm. The concentrations of constituents in the surface runoff were measured at sampling sites categorized by land use type in the residential zone, and by industry type in the industrial zone. The water quality constituents of BOD5, COD, SS, NO3-N, TKN, PO4-P, TP, n-Hexane extracts, Cr, Cu, Pb and Fe were analyzed. The event mean concentrations (EMCs) of COD, SS, TKN and TP in the residential zone were 313 mg/L, 279 mg/L, 8.45 mg/L, 1.98 mg/L, and those in the industrial zone were 80 mg/L, 106 mg/L, 5.07 mg/L, and 1.93 mg/L, respectively. Cumulative load curves were created to analyze the first-flushing effect of each pollutant related to the pollutant, the rainfall event, and the land use type. No general relationship between the cumulative load and runoff has been established. The degree of first-flushing effect by constituents was in the following order; TKN>COD>SS>HEM>TP>PO4-P. The correlations between SS and other constituents were analyzed to evaluate the efficiency of the physical treatment process to control the surface runoff in urban areas. Based on the correlation of constituents with SS, high treatment efficiency of SS, heavy metals, organic matter, and TP was expected. The unit pollutant loading rates of COD, SS, TKN, TP, Cr and Pb in the residential zone were 2,392, 2,130, 64.6, 15.1, 0.31, and 1.83 kg/ha/yr, and those in the industrial zone were 612, 812, 38.7, 14.8, 0.51 and 0.82 kg/ha/yr, respectively.
Evaluation of urban non-point source runoff of hazardous metals entering Santa Monica Bay, California
Authors: Buffleben M.S. , Zayeed K. , Kimbrough D. , Stenstrom M.K. , Suffet I.H.
Published: May 2018

Significant amounts of non-point source runoff enter the Santa Monica Bay from the Ballona Creek Watershed during wet weather flow. The primary objective of this study was to determine the concentrations of hazardous metal pollutants associated with the aqueous and suspended solid phases during wet weather flow. A calculation of the mass of the pollutants for each storm was conducted. Other objectives of this study were to evaluate during a storm event the relationships between (1) soluble and sorbed metals, (2) storm flow and pollutant loading, including a determination if a first flush was present, and (3) total mass loading of pollutants and relative pollution loading from three watershed sub-basins. This study focused on the urbanized watershed of Ballona Creek, which is approximately 330 km2 (127 miles2) in size and developed primarily with residential and light commercial industries. In the 1997–98 rain season, an El Niño year, two storm events were monitored by the collection of hourly grab samples. An initial storm monitored Ballona creek, while a second storm also monitored Ballona Creek along with two smaller sub-watersheds, Centinela Channel and Sepulveda Channel. The results indicated the suspended solids phase primarily transported the mass for five of the six hazardous metals studied: cadmium, chromium, copper, lead, and nickel. Arsenic was found primarily in the aqueous phase.
Critical issues for stormwater ponds: learning from a decade of research
Authors: Anderson B.C. , Watt W.E. , Marsalek J.
Published: May 2018

The Queen’s University/National Water Research Institute Stormwater Quality Enhancement Group has been actively researching stormwater ponds for the past decade, using a fully instrumented on-line system in Kingston, Ontario, Canada as a representative field installation of this group of stormwater best management practices, along with comprehensive surveys of other facilities as well. From this body of research, the Group has concluded that there are a number of identifiable factors, termed critical issues, which will significantly influence the success, failure and sustainability of these BMPs. Such factors will be important to a very diverse group of stakeholders in stormwater management, including designers, owners/operators, regulatory authorities and the general public. These factors can be grouped within the categories of initial design, operation and maintenance, performance and adaptive design. From this work, it is concluded that the so-called first generation quantity-control ponds may be outdated today, compared with the modern focus on quantity and quality issues in the second generation systems; nonetheless, without consideration of these critical issues and flexible design practices which can account for emerging or future issues, the current systems also run the risk of becoming outdated before the end of their design lives.
Development of a new mathematical model for subsurface water quality management
Authors: Das D.B. , Nassehl V.
Published: May 2018

The interfaces between free (e.g., groundwater) and porous (e.g., soil) flow zones in the subsurface represent important transition zones across which many important transfer/exchange processes occur. The understanding of these interactive phenomena and the way these regions behave in combination is, therefore, critical for management of subsurface water quality. Indispensable to this is numerical modelling and simulation as they can handle complex flow domains and minimise the analysis cost and time. In the present work, the hydrodynamic conditions for a combined free and porous flow domain in the subsurface are analysed. An investigation into the fluid dynamical behaviour for different aspect ratios of the domains is of most interest.
Nutrient management for coastal zones: a case study of the nitrogen load to the Stockholm Archipelago
Authors: Scharin H.
Published: May 2018

This study investigates cost-effective solutions of decreasing the nutrient load to a coastal area, using a drainage basin approach. The study is applied to the Stockholm Archipelago, a coastal area of the Baltic Sea suffering from eutrophication caused by the load of nutrients entering the area. Nitrogen is the nutrient of concern in this study since it is the limiting nutrient of the Archipelago. The main sources of nitrogen are wastewater plants, agriculture, and atmospheric depositions. The final impact of a deposition depends on the buffering capabilities it is subject to on its trajectory from the source to the recipient. This is the reason for using a recipient oriented approach, in which the focus is to reduce the final impact of a deposition. The model integrates data over hydrology, land cover, land use, and economy in order to find the optimal allocation of measures. Results indicate that in order to achieve cost effectiveness, the major part of nitrogen load reduction to the Archipelago should be done at the wastewater plants and by constructing wetlands. The minimum annual cost of reaching a 50% reduction of the load to the Archipelago was estimated to around 191 million Swedish crowns (around $ 19 million).
Sensitivity analysis and auto-calibration of an integral dynamic model for river water quality
Authors: van Griensven A. , Francos A. , Bauwens W.
Published: May 2018

ESWAT – Extended Soil and Water Assessment Tool – was developed to allow for an integral modelling of the water quantity and quality processes in river basins. ESWAT is a physically based, semi-distributed model, with a moderate-to-large number of parameters and input and output variables (depending on the desegregation scheme). An auto-calibration procedure was implemented for the optimisation of the process parameters. The procedure is based on a new approach for multi-objective calibration and incorporates the algorithms of the Shuffled Complex Evolution Method. The optimisation uses a global optimisation criterion, whereby several output variables can be taken into account simultaneously. A statistical method enables the aggregation of the objective functions for individual variables, hereby avoiding the weighting problem. To select the important parameters for the optimisation, a sensitivity analysis precedes the calibration. The latter analysis is based on the One-factor-At-a-Time (OAT) design approach.

The sensitivity analysis and the calibration procedure are applied to the river Dender in Belgium. The river is characterised by high pollution loads and long residence times in summer periods.
Anaerobic digestion: concepts, limits and perspectives
Authors: Schink B.
Published: May 2018

Anaerobic degradation processes are faced with limitations with respect to reaction energetics and reaction kinetics. The small amount of energy available in methanogenic degradation of complex organic compounds allows in most cases only the conservation of minimum amounts of energy in the lowest range of energy exploitable by biochemical reactions for ATP-synthesis. This limit has to be defined in the range of 1/3–1/4 of an ATP unit, or 15–20 kJ per mol reaction. Such small amounts of energy are exploited efficiently by syntrophic microbial communities co-operating e.g. in fatty acid conversion to methane and CO2. Methanogens also set the stage for efficient conversion of sugars or amino acids, and channel electron fluxes to the utmost efficiency. Kinetic limitations are set by the inertness of certain compounds, e.g. hydrocarbons, to react in the absence of a strong oxidant. New reactions have been found recently which activate such compounds, e.g. aromatic hydrocarbons such as toluene, xylenes, naphthalene, methane, or ammonia. Refined techniques for analysis of microbial activities in ill defined natural environments such as digestive tracts of small invertebrates or polluted aquifers have shown an amazing capacity for anaerobic or oxygen-limited degradation processes that are still to be exploited. Thus, anaerobic digestion is still a matter of fast increasing knowledge, both on the side of basic research as well as on the side of application in treatment of soil, waste materials, or in understanding complex living communities.
Ozonation of wastewater sludge for reduction and recycling
Authors: Ahn K.-H. , Park K.Y. , Maeng S.K. , Hwang J.H. , Lee J.W. , Song K.-G. , Choi S.
Published: May 2018

An ozone treatment system was introduced as an alternative method for municipal sludge treatment and disposal. A pilot-scale facility was built to investigate the feasibility of the ozonation for sludge reduction and recycle. The system consists of three main parts; advanced wastewater treatment, sludge ozone treatment and belt press dewatering. Ozonation of wastewater sludge resulted in mass reduction by mineralization as well as volume reduction by improvement of dewatering characteristics. The supernatant of the ozonated sludge, consisting of solubilized organics and micro-particles, proved to be an effective carbon source for denitrification. A simple economic assessment reveals that the ozonation process can be more economical than incineration for sludge treatment and disposal at small- and medium-sized wastewater treatment plants.
Competition for H2 between sulfate reducers, methanogens and homoacetogens in a gas-lift reactor
Authors: Weijma J. , Gubbels F. , Hulshoff Pol L.W. , Stams A.J.M. , Lens P. , Lettinga G.
Published: May 2018

Reported values for growth kinetic parameters show an order in competitivity of heterotrophic sulfate reducing bacteria>methanogens>homoacetogens for the substrate hydrogen. This order suggests that methanogens can succesfully compete with consortia of heterotrophic SRB and homoacetogens when H2/CO2 is present as sole substrate. However, we found in experiments using gas-lift reactors inoculated with anaerobic sludge and fed with H2/CO2 and sulfate, that heterotrophic sulfate reduction rapidly and completely outcompeted methanogenesis, whereas a low amount of acetate was formed. Thus, in disagreement with the above competitivity order, hydrogen is more readily consumed by homoacetogenesis than by methanogenesis, indicating that the competition is not kinetically determined. The superior settling velocity of sulfidogenic-acetogenic sludge compared to that of methanogenic sludge suggests that the former sludge is better retained, which can explain the predominance of sulfate reduction/homoacetogenesis over methanogenesis.
A comparative study between mechanical, thermal and oxidative disintegration techniques of waste activated sludge
Authors: Camacho P. , Deleris S. , Geaugey V. , Ginestet P. , Paul E.
Published: May 2018

The release performances of an organic and mineral activated sludge matrix were studied for a wide range of disintegration treatments like mechanical, thermal, thermal-chemical and oxidative disintegration techniques. The maximal COD release was 35% of total COD after 24 hours contact time at 95°C. A limiting value of 60% COD release was obtained for 500 and 700 bars after 10 passes. Concerning the oxidative disintegration techniques (O3 and H2O2), a limiting value of around 60-65% of TOC release was observed. Therefore, it was hypothesised that thermal and mechanical treatments allow mainly for breaking apart the micro-organisms while the oxidative treatment destroys the sludge flocs and disrupts the micro-organisms. A release effect of the mineral fraction is observed only oxidative disintegration techniques.
Kinetics and inhibition during the decolorization of reactive anthraquinone dyes under methanogenic conditions
Authors: Fontenot E.J. , Beydilli M.I. , Lee Y.H. , Pavlostathis S.G.
Published: May 2018

The objective of this study was to assess the biological decolorization of two reactive anthraquinone dyes (Reactive Blue 4, RB 4; Reactive Blue 19, RB 19) under methanogenic conditions. Using a mixed, methanogenic culture, batch assays were performed to evaluate both the rate and extent of color removal as well as any potential inhibition. The effect of initial dye, biomass, and organic feed concentration, as well as the effect of repetitive dye addition on color removal kinetics and culture inhibition were assessed. Overall, a lower rate and extent of color removal was observed in RB 4-amended cultures as opposed to the RB 19-amended cultures. For an incubation time of ca. 15 days and an initial dye concentration of 2000 mg/L, the extent of color removal was 50 and 95% for RB 4 and RB 19, respectively. Inhibition of acidogenesis and to a larger degree of methanogenesis, resulting in accumulation of volatile fatty acids, was observed in both RB 4- and RB 19-amended cultures. Although the degree of inhibition varied among the two dyes tested (RB 19 was more inhibitory than RB 4), an increase of inhibition was observed with increasing initial dye concentration. At an initial dye concentration of 500 mg/L or higher, methane production was lower than 6% of that of the control culture for both RB 4 and RB 19. However, color removal occurred despite culture inhibition.
Ammonia inhibition on thermophilic aceticlastic methanogens
Authors: Liu T. , Sung S.
Published: May 2018

The inhibition effects of total ammonia nitrogen (TAN) on aceticlastic methanogenic activity using biomass from thermophilic anaerobic reactors were investigated in this study. Anaerobic Toxicity Assays (ATA) were conducted after the biomass was acclimated to different levels of TAN. The TAN background concentrations in the reactors were 400, 1,200, and 3,050 mg/L. The results from ATA showed: 1) high TAN concentrations could cause inhibition of aceticlastic methanogens; 2) biomass acclimated to higher TAN concentrations could alleviate the inhibition effect due to the increase of TAN concentration; 3) the lethal TAN concentration for methanogens was approximately 10,000 mg/L regardless of the background TAN concentration; 4) ATA results also revealed the role played by pH. At a given TAN concentration, methanogenic activity varied with the pH values. The highest methanogenic activity was always observed at a pH of 7.0∼7.5. 5) It was also observed that acclimation could increase the pH tolerance range, which made methanogens less sensitive to pH changes.
Effect of high salinity on the fate of methanol during the start-up of thermophilic (55°C) sulfate reducing reactors
Authors: Vallero M.V.G. , Hulshoff Pol L.W. , Lens P.N.L. , Lettinga G.
Published: May 2018

Two 6.5 L lab-scale upflow anaerobic sludge bed (UASB) reactors were operated at 55°C fed with methanol as the sole electron and carbon source and in excess of sulfate (COD/SO42− of 0.5) in order to investigate the effect of high wastewater salinity on the start-up period. The first reactor (UASB I) was operated without NaCl addition, while the second reactor (UASB II) was fed with 25 g.L−1 of NaCl in the first 13 days of operation. Successful start-up of UASB I was achieved, with full methanol conversion (100% elimination) to methane gas (methane production rate up to 3.66 gCOD.L−1.day−1). Despite the detection of sulfide from day 15 onwards in UASB I, methane was the main mineralization product when operating at an organic loading rate (OLR) of 5 gCOD.L−1.day−1 and a hydraulic retention time (HRT) of 10 hours. Sulfide and acetate started to be produced after salt omission from the influent in UASB II at day 13, with no detection of methane. Acetate was the main product when operating at an OLR of 10 gCOD.L−1.day−1 and HRT of 6.5 hours in both reactors. Apparently, the methane producing bacteria (MPB) are the trophic group most sensible to the NaCl shock.
Characterization and dewaterability of raw and stabilized sludge using different treatment methods
Authors: Mijaylova Nacheva P. , Moeller-Chávez G. , Ramírez Camperos E. , Cardaso Vigueros L.
Published: May 2018

A comparison of the characteristics and stabilization potential of the four most used sludge treatment systems in Mexico was made. A pilot plant constituted by separate systems for anaerobic and aerobic digestion, lime stabilization, conditioning and dewatering, was built and operated during four months in one of the biological wastewater treatment plants in Acapulco, Mexico. Composting of sludge was also made. An aerobic static pile was built using bulking materials available in the region. A turbine centrifuge was used for dewatering the stabilized sludge and results showed good performance of the device. The main problem for the beneficial use of treated sludge was its pathogenicity. The composting process allowed us to obtain a product with approximately 20 fecal coliform density (MPN/g); with lime stabilization, the sludge produced had a fecal coliform density of 2 MPN/g. From these results, it is concluded that both the composting process and the alkaline stabilization with lime produce a well stabilized sludge, bacteriologically safe that accomplishes the requirements for its use on soil without restrictions. Related to parasitological removal, the best helminth egg removals were obtained also using these two processes. Ascaris sp. densities in raw sludge (309-430 eggs/g) were reduced to a final density of 3-14 eggs/g in the aerobic composting process and to 4-18 eggs/g in the lime stabilized sludge. Removal is not high enough to reach the recommended level for unrestricted use of stabilized sludge.
Characterization of soluble microbial products (SMP) in effluents from anaerobic reactors
Authors: Aquino S.F. , Stuckey D.C.
Published: May 2018

The residual COD from anaerobic treatment processes is usually too high to comply with legislative discharge levels. It has been shown that in well operated systems the majority of the effluent COD originates from soluble microbial products (SMP) produced by the system itself, hence the characteristics of these compounds become important when assessing post-treatment systems to remove the residual COD. The molecular weight (MW) distribution and the identification of SMP in the effluents from three different anaerobic reactors will be presented. It has been found that the bulk of SMP lies in the low MW range, though compounds with MW as high as 300 kDa were also present in all anaerobic effluents. Preliminary results on the identification of such compounds using GC/MS surprisingly revealed the presence of long chain alkenes (C12–C24) and alkanes (C12–C16), as well as some aromatic compounds. These compounds that likely come from cell lysis and endogenous decay may not be easily biodegradable, hence their presence in the effluent is likely to cause the residual COD.
Anaerobic degradation of oleic acid by suspended and granular sludge: identification of palmitic acid as a key intermediate
Authors: Pereira M.A. , Pires O.C. , Mota M. , Alves M.M.
Published: May 2018

The aim of the present work was to study the maximum potential methane production in batch assays of sludge samples taken along the operation of two EGSB reactors (RI inoculated with granular sludge and RII inoculated with suspended sludge) fed with increasing oleic acid concentrations between 2 and 8 gCOD/l (HRT = 1 day). After removing the residual substrate, the sludge was incubated in batch vials without any added carbon source. A maximum methane production rate of 152 ± 21 mlCH4(STP)/gVS.day was obtained for the suspended sludge taken on day 70, when oleate at a concentration of 2 g COD/l was fed with a co-substrate (50% COD). The maximum plateau achieved in the methane production curve was 1145 ± 307 mlCH4(STP)/gVS, obtained for the suspended sludge taken on day 162, when oleate was fed as the sole carbon source at 6 g COD/l. The methanization rate of the adsorbed substrate was enhanced under stirring conditions and was inhibited by adding oleic acid. Extraction and GC analysis confirmed that the main adsorbed substrate was palmitate, and not oleate. Accumulated palmitate adsorbed onto the sludge and further β-oxidation was inhibited when in the presence of oleic acid. If oleic acid was removed from the medium β-oxidation proceeded with methane production. Suspended sludge was more efficient than granular sludge.
Anaerobic treatment of sludge: focusing on reduction of las concentration in sludge
Authors: Haggensen F. , Mogensen A.S. , Angelidaki I. , Ahring B.K.
Published: May 2018

Anaerobic degradation of linear alkylbenzene sulfonates (LAS) was tested in continuous stirred tank reactors (CSTR). LAS12 was used as a model compound and was spiked on sewage sludge. The experiments clearly showed that transformation of LAS12 occurred under anaerobic conditions. The degree of transformation varied between 14% and 25%. HPLC analysis showed that disappearance of LAS12 was followed by the formation of a metabolite. The experiments indicated that there is a clear correlation between degradation of organic matter contained in sludge and transformation of LAS12. When the reduction degree of the organic matter increased from 22% to 28%, the transformation degree of LAS12 also increased, from 14% to 20%. Decreasing the total solids concentration of the influent sludge or increasing the spiked concentration of LAS12 did not alter the degree of LAS12 transformation significantly. A clear correlation between transformed and bioavailable LAS12 was found, indicating that it is merely the bioavailable fraction of LAS12 that is transformed by anaerobic digestion. The results from the present study are promising and indicate that a great potential for biological degradation of LAS is possible even at anaerobic conditions.
Anaerobic treatment of domestic sewage: established technologies and perspectives
Authors: Foresti E.
Published: May 2018

The use of anaerobic reactors for domestic sewage treatment has increased significantly since the UASB configuration started to be efficiently applied for this purpose in the beginning of the 1980s. Nowadays, hundreds of UASB reactors, or similar anaerobic units, are used in domestic sewage treatment systems, particularly in developing countries. These units have been operated at ambient temperature, normally higher than 20°C, at hydraulic detention time in the range of 6 to 10 hours, and organic loading rates lower than 3.0 kg COD.m−3.d−1. They have presented COD removal efficiencies in the range of 65% to 80%. Besides, new configurations have been developed and assayed in research centres, aiming to amplify the range of application and to improve process performance. At the same time, research is being conducted on the post-treatment of anaerobic effluents attempting to offer alternatives to the existing conventional systems. It takes into consideration not only sanitation and environmental protection, but also considers resources conservation at lower construction and running costs as the main supporting concepts for further development. This text presents some aspects of the consolidated technologies and suggests on further developments in the conception of domestic sewage treatment systems having the anaerobic process as their core.
Evaluation of bacteriophages during the treatment of sludge
Authors: Mignotte-Cadiergues B. , Gantzer C. , Schwartzbrod L.
Published: May 2018

The aim of this work was to determine the effect of liming and composting on the fate of three bacteriophages (somatic coliphages, F-RNA phages, Bacteroides fragilis phages) considered as potential indicators of viral contamination. It was shown that the three bacteriophages studied exhibited variable densities in sludge. Somatic coliphages were most abundant (104 to 105 .10 g−1 DM) then F-RNA bacteriophages (102 to 104.10 g−1 DM) and Bacteroides fragilis phages (101 to 102.10 g−1 DM). The efficacy of liming was found to be pH dependent but also sludge dependent. The pH allowing 99% elimination of somatic coliphage is close to 9 for solid sludges and close to 13.5 for liquid sludges. For composting, our findings clearly demonstrated that phage inactivation is very clearly temperature-dependent. For temperatures reaching 70°, there is a 5 log reduction in somatic coliphages while for temperature in the 50-55°C range, the drop off is only 2 log. Considering the efficacy of the treatment methods, it is clear that the well-established industrial procedures that reach temperatures in the 60-70°C range totally inactivate all 3 phages tested and present in sludge before composting.
Expert system for the on-line diagnosis of anaerobic wastewater treatment plants
Authors: Puñal A. , Rodríguez J. , Carrasco E.F. , Roca E. , Lema J.M.
Published: May 2018

A diagnosis system for anaerobic wastewater treatment processes is presented. The system is able to recognise the state and trend of the operation and suggest the appropriate control action. The on-line variables measured were gas flow rate and composition (methane and carbon monoxide), feed and recycling flow rates, temperature and pH, while the manipulable inputs are feed, recycling and buffer-addition flow rates. The diagnosis system comprises a structured rule base, incorporating expert knowledge using fuzzy logic features. The structure of the system is based on the classification of information related to the process in three categories: i) the state of the process, ii) its trend and iii) the recommended set-point values for the inputs manipulated: feeding, buffer and recycling pumps. The system was applied to diagnose the operation of a 1.1 m3 hybrid UASB-UAF treating wastewater from a fibreboard production factory under different conditions (overload and underload), corresponding to some of the typical causes of destabilisation in anaerobic wastewater treatment plants. These situations require control action in order to maintain the stability and the treatment capacity of the reactor. The application of the system developed for the purpose of managing the situation proved to be reliable for supplying the actual state and trend of the process, as well as the adequate set point values to recover stable operation and/or to avoid further destabilisation.