bluuebunny/crossref_metadata_2025 huggingface dataset:
Runoff of faecal microorganisms and nutrients from perennial grass ley after application of slurry and mineral fertiliser
Authors: Heinonen-Tanski H. , Uusi-Kämppä J.
Published: May 2018

Perennial grass was fertilised with cattle slurry either surface-spread or injected into the soil. Slurry was spread once (early summer) in 1996 and 1997 and twice (both summer and autumn) in 1998 and 1999. The control was mineral fertilisation in summer. Faecal microbial numbers in surface runoff water were very high in late June 1998 soon after very heavy rains even though the last slurry application had been made almost one year earlier. There was no clear difference between slurry spreading methods. Autumn spreading of slurry lead to high microbial levels in runoff waters and water hygiene was protected better by slurry injection than by surface spreading. In spring, after snow melt, some faecal microorganisms were found in surface runoff water and the numbers of faecal microorganisms were less from plots with slurry surface spreading than those with slurry-injection. Losses of total phosphorus (TP) and total nitrogen (TN) in surface runoff were 2.7 and 7.7 kg/ha respectively from grass with surface-spread slurry in winter 1998-1999. The injection of slurry decreased TP and TN runoff by an average of 81% and 73% respectively. In 1999 there was little runoff because the summer was sunny and dry.
Comparison of static and dynamic disinfection models for bacteria and viruses in water of varying quality
Authors: Springthorpe S. , Sander M. , Nolan K. , Sattar S. A.
Published: May 2018

Disinfection studies rarely use natural waters due to demands exerted on the applied disinfectants and lack of consistent disinfectant residuals. This study compared the degree of disinfection achieved in natural waters between conventional batch (static) models and a system of similar volume where disinfectant residuals were maintained at constant levels (dynamic). In the latter, disinfectant was delivered through a hollow fibre cartridge from a slipstream of a full-scale (chloramine) or pilot (chlorine) water treatment plant. The test organisms (hepatitis A virus, poliovirus, MS-2, Mycobacterium terrae and Enterococcus durans) were selected with different resistance to the disinfectants. In general, for water of ‘good’ quality, the differences between the two systems were often small or not apparent for monochloramine. However, for low chlorine residuals, or when additional demand was placed on the disinfectant, differences between the two systems became more apparent. Little difference was seen between disinfection of the test organisms singly or in mixtures, but injury of vegetative bacteria with monochloramine was very apparent. This system could be useful for understanding the fluctuations in disinfection efficacy that may occur in source water of varying quality, or in distribution systems, as disinfectant residuals decline.
Occurrence of microcystins in raw water sources and treated drinking water of Finnish waterworks
Authors: Lahti K. , Rapala J. , Kivimäki A-L. , Kukkonen J. , Niemelä M. , Sivonen K.
Published: May 2018

Problems caused by cyanobacteria are common around the world and also in raw water sources of drinking water treatment plants. Strains belonging to genera Microcystis, Anabaena and Planktothrix produce potent hepatotoxins, the microcystins. Laboratory and pilot scale studies have shown that microcystins dissolved in water may pass the conventional surface water treatment processes. In 1998 the World Health Organization proposed a guide value of 1 μg/L for microcystin-LR (MC-LR) in drinking water. The purpose of this research was to study the occurrence of microcystins in raw water sources of surface waterworks and in bank filtration plants and to evaluate the removal of microcystins in operating waterworks. Four bank filtration plants and nine surface waterworks using different processes for water treatment were monitored. Phytoplankton was identified and quantified, and microcystins analysed with sensitive immunoassay. Microcystin occurrence in selected water samples was verified with HPLC and a protein phosphatase inhibition method. Microcystins were detected sporadically in raw water sources of most of the waterworks. In two raw water supplies toxins were detected for several months. The highest microcystin concentrations in incoming raw water were approximately 10 μg/L MC-LR equivalents. In treated drinking water microcystins were detected occasionally but the concentrations were always below the guide value proposed by WHO.
New simulators for the optimum management and operation of wastewater treatment plant
Authors: Ayesa E. , Garralon G. , Rivas A. , Suescun J. , Larrea L. , Plaza F.
Published: May 2018

This paper presents the basic description and the first full-scale implementation of a new kind of simulator specially designed to facilitate and improve the management and operation of modern wastewater treatment plants (WWTP). This new kind of simulator for plant operation is specifically adapted to every WWTP and the software is developed considering the common needs of the operators in plant exploitation.

The internal structure of the plant operation simulator is based on a complete connection between the real data and the mathematical model of the plant. The software is then able to perform the processing, storage and management of the plant data and to predict the evolution of the process reading the required inputs from its stored files. The results obtained with the first application recommend the implementation of this new kind of simulators for plant operation in other treatment plants. However, it is important to note that the application of this technology implies a systematic and rigorous methodology in the acquisition and processing of the most significant plant data.
Experience with an up-flow biological aerated filter (BAF) for tertiary treatment: from pilot trials to full scale implementation
Authors: Payraudeau M. , Pearce A. R. , Goldsmith R. , Bigot B. , Wicquart F.
Published: May 2018

Biofilters can be added to existing non-nitrifying activated sludge plants for tertiary ammonia removal and effluent polishing. It is a convenient, efficient, and cost effective way of meeting more stringent consents. In order to prove this technology, a biofilter pilot plant was installed in a large activated sludge plant with challenging conditions, since almost half of the load is industrial effluent and the water temperature can be as low as 7°C. Trials were conducted over a two year period, providing the following information: low water temperature does not affect the process; the optimum rise rate at nominal flow is 8.5 m/h for this wastewater; the consent can be achieved for ammonia loads up to 0.94 kgNH4N/M3 media/day; about 50% of the post-secondary TSS and BOD can be removed in the BAF; a large proportion of industrial effluent has not had any noticeable effect on the beads after two years. A full scale plant with a nominal flow of 8257 l/s was then built and commissioned in summer 1998. Seeding was completed within three weeks of starting the filters. Two months later, a 28 day takeover was started. Results obtained on full scale plant during and after this test confirm the results obtained on the pilot.
Operating space diagrams: a tool for designers of wastewater treatment plants
Authors: Hopkins L. N. , Lant P. A. , Newell R. B.
Published: May 2018

Recent years have seen the introduction of new and varied designs of activated sludge plants. With increasing needs for higher efficiencies and lower costs, the possibility of a plant that operates more effectively has created the need for tools that can be used to evaluate and compare designs at the design stage. One such tool is the operating space diagram. It is the aim of this paper to present this tool and demonstrate its application and relevance to design using a simple case study. In the case study, use of the operating space diagram suggested changes in design that would improve the flexibility of the process. It also was useful for designing suitable control strategies.
Mass balance for on-line αkLa estimation in activated sludge oxidation ditch
Authors: Chatellier P. , Audic J. M.
Published: May 2018

The capacity of an aeration system to transfer oxygen to a given activated sludge oxidation ditch is characterised by the αkLa parameter. This parameter is difficult to measure under normal plant working conditions. Usually this measurement involves off-gas techniques or static mass balance. Therefore an on-line technique has been developed and tested in order to evaluate αkLa. This technique deduces αkLa from a data analysis of low cost sensor measurement: two flow meters and one oxygen probe. It involves a dynamic mass balance applied to aeration cycles selected according to given criteria. This technique has been applied to a wastewater treatment plant during four years. Significant variations of the αkLa values have been detected while the number of blowers changes. This technique has been applied to another plant during two months.
Applying fine bubble aeration to small aeration tanks
Authors: Duchène; Ph. , Cotteux E. , Capela S.
Published: May 2018

Because the aeration system in an activated sludge plant typically represents a large part of the total energy requirements, designers and operators need accurate oxygen transfer information to make the aeration system as energy efficient as possible. This paper presents clean water tests performed at 38 wastewater treatment plants. The Specific Aeration Efficiency results (SAE, kgO2/kWh) are reported for: (1) large open channels (volume higher than 1000 m3), (2) small open channels, (3) total floor coverage cylindrical tanks, and (4) cylindrical tanks with a grid arrangement. Some practical guidelines can be drawn, some of them being: (1) high SAE can be achieved at small aeration tanks (<1000m3), applying cylindrical tanks with a total floor coverage arrangement of diffusers, volumetric blowers, and moderate air flow rates per diffuser area; (2) the high investment cost of this configuration can be justified with respect to a grid layout characterized by spiral liquid circulation which affects the oxygen transfer; (3) small open channels can meet sufficient SAE values but fail to meet in this range of tank volumes those of total floor coverage cylindrical tanks.
Critical velocity of floatables in Combined Sewer Overflow (CSO) chambers
Authors: Cigana J. , Lefebvre G. , Marche C.
Published: May 2018

Although the efficiency of underflow baffles has never been clearly proven, these underflow baffles have gained in popularity over the last few years as a viable means to intercept floatables in Combined Sewer Overflows (CSOs). These pilot scale essays, performed in a 17.0 metres basin at various flowrates, show that a critical horizontal velocity (VCR) may develop in the overflow chamber. Whenever this critical velocity is exceeded, floatables that would normally rise to the surface are kept within the flow and never intercepted, thus rendering the underflow baffle ineffective. The equation relating the critical horizontal velocity to the vertical velocity is found to be: VCR = 16 w RH1/6.
Removing filterable reactive phosphorus from highly coloured stormwater using constructed wetlands
Authors: Lund M.A. , Lavery P.S. , Froend R.F.
Published: May 2018

A constructed wetland design, consisting of 16 repeating cells was proposed for Henley Brook (Perth, Western Australia) to optimise the removal of FRP from urban stormwater. Three replicate experimental ponds (15×5 m), were constructed to represent at a 1:1 scale a single cell from this design. Three 5 m zones of each pond were sampled: shallow (0.3 m) vegetated (Schoenoplectus validus) inflow and outflow zones and a deeper (1 m), V-shaped central zone. In 1998/99, inflows and outflow waters were intensively sampled and analysed for FRP and Total P. In addition, all major pools of P (plants, sediment) within the ponds, and important P removal processes (benthic flux, uptake by biofilm and S. validus) were quantified.

A removal efficiency of 5% (1998) and 10% (1999) was obtained for FRP. Initial uptake was mainly in plant biomass, although the sediment became an increasingly important sink. Benthic flux experiments showed that anoxia did not cause release of P from sediments, indicating that most of the P was bound as apatite rather than associated with Fe or Mn. The highly coloured waters were believed responsible for the very low biofilm biomass recorded (<1 g.m-2). We have demonstrated that constructed wetlands can be effective for removing FRP immediately after construction, although their long-term removal capacity needs further research.
Nitrogen removal in a combined system: vertical vegetated bed over horizontal flow sand bed
Authors: Kantawanichkul S. , Neamkam P. , Shutes R.B.E.
Published: May 2018

Pig farm wastewater creates various problems in many areas throughout Thailand. Constructed wetland systems are an appropriate, low cost treatment option for tropical countries such as Thailand. In this study, a combined system (a vertical flow bed planted with Cyperus flabelliformis over a horizontal flow sand bed without plants) was used to treat settled pig farm wastewater . This system is suitable for using in farms where land is limited.

The average COD and nitrogen loading rate of the vegetated vertical flow bed were 105 g/m2.d and 11 g/m2.d respectively. The wastewater was fed intermittently at intervals of 4 hours with a hydraulic loading rate of 3.7 cm/d. The recirculation of the effluent increased total nitrogen (TN) removal efficiency from 71% to 85%. The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal efficiencies were 95% and 98%. Nitrification was significant in vertical flow Cyperus bed, and the concentration of nitrate increased by a factor of 140. The horizontal flow sand bed enhanced COD removal and nitrate reduction was 60%. Plant uptake of nitrogen was 1.1 g N/m2.d or dry biomass production was 2.8 kg/m2 over 100 days.
Occurrence and die-off of indicator organisms in the sediment in two constructed wetlands
Authors: Stentström T.A. , Carlander A.
Published: May 2018

The interest in constructed wetlands for municipal wastewater and stormwater treatment has recently increased but data for the reduction efficiency of indicator organisms are often restricted to the water phase. In a full-scale wastewater wetland in Sweden fecal coliforms and enterococci were reduced by 97-99.9% and coliphages by approximately 70%. The factors affecting the reduction are however less well understood.

In two full-scale wetlands, for stormwater and wastewater treatment, an assessment has been done of the particle associated fraction of indicator organisms. No significant differences in the particle-associated numbers were seen between the inlet and the outlet of the wetlands, but the amounts of sedimenting particles varied between the two sites. In the stormwater wetland the amount of sedimenting particles at the outlet was 3% of the amount at the inlet, while the wastewater wetland had much lower particle removal efficiency. The reduction of suspended particles seems to be the main factor for bacterial elimination from the water phase, governed by vegetation and design. In the sediment, survival of presumptive E.coli, fecal enterococci, Clostridium and coliphages were long with T90-values of 27, 27, 252 and 370 days, respectively. The organisms can however be reintroduced by resuspension. Viruses in the water phase may be of main concern for a risk assessment of receiving waters.
Performance modeling of subsurface-flow constructed wetlands systems
Authors: Dahab M.F. , Surampalli R.Y. , Liu W.
Published: May 2018

A subsurface flow constructed wetlands (CW) system, located at a neighborhood consisting of a small housing development and golf courses outside of Lincoln, NE, was studied for its effectiveness as a small community wastewater system. Extensive monitoring was conducted biweekly between June 1996 and December 2000. Prediction models for soluble CBOD5 NH3-N, and TP removal in CW were employed for comparison with the field data. It was found that the disappearance of BOD5 and NH3-N could be approximated using first-order kinetics, but the kinetics of TP removal were unclear. The reduction rate constants regressed from the field data were found to be lower than literature reported values.
Natural wastewater treatment in Hungary
Authors: Szabó A. , Osztoics A. , Szilágyi F.
Published: May 2018

Over the last few decades more and more natural wastewater treatment systems have been built in Hungary. The present study is the first step in creating a broad database on the water quality parameters and on the pollutant removal efficiency of these systems. The investigation included 78 plants out of which we analysed 16 systems in detail. Four types of natural methods are evaluated: wetlands, ponds, bio-mechanical combined oxidation (BMKO) systems, and poplar plantations. Pond systems are efficient in ammonium-nitrogen (NH4-N) removal, reducing it with 83% (41-88%). Their chemical oxygen demand (CODCr) removal capacity is only 55% (37-81%). The only BMKO system that could be evaluated performs high CODCr (77%) and total suspended solid (TSS) (89%) removal. Removal of NH4-N and total nitrogen (TN) declines during the years of operation giving an average value of 39% and 49%, respectively. The system is not efficient in phosphorus removal (13%). In wetlands the 71% CODCr (53-96%), and 57% TSS (33-91%) removal provides satisfactory effluent quality most of the time. Wetlands performed low nutrient removal, i.e., 17% (-21-46%) for TN and 26% (-20-92%) for phosphorus. Poplar plantations are very effective in pollutant removal. Even the average removal of each nutrient type is above 75%. Several problems have occurred in the operation of natural treatment systems. However, if carefully planned and constructed, and the required maintenance work is done properly, they can be possible alternatives for wastewater treatment.
Subsurface-flow constructed wetlands treatment in the plains: five years of experience
Authors: Dahab M.F. , Surampalli R.Y.
Published: May 2018

This paper documents the performance of a subsurface-flow constructed wetlands system during its initial five years of operation under variable loading and operating conditions associated with a northern midwestern US climate. The results indicate that effective and sufficient CW seasonal removals of TSS, VSS, CBOD5, COD, and fecal coliform were achieved. Wastewater temperatures seemed to affect CBOD5 and COD removal rates. Nitrogen and phosphorus reductions were not as effective and varied seasonally, as well as with wastewater temperature. The addition of a sand filter, to aid in further nitrification and disinfection following CW treatment, markedly improved the performance of the wetlands system. After a few years of operation, the remarkable performance of the CW system was dampened by apparent clogging and subsequent eruption of wastewater at the head-end of the treatment cells. While clogging was partially caused by biomass build-up in the wetlands substrate, visual observations suggest that excessive vegetation coupled with relaxed maintenance may also be responsible for clogging.
Treatment of a molasses based distillery effluent in a constructed wetland in central India
Authors: Billore S.K. , Singh N. , Ram H.K. , Sharma J.K. , Singh V.P. , Nelson R.M. , Dass P.
Published: May 2018

A field-scale 4-celled, horizontal subsurface constructed wetland (CW) was installed to evaluate removal efficiencies of wastewater constituents in an industrial distillery effluent. Total and dissolved solids, NH4-N, TKN, P and COD were measured. This CW design provides four serial cells with synthetic liners and a river gravel base. The first two unplanted cells provide preliminary treatment. Specific gravel depths and ensuing biofilm growth provides anaerobic treatment in Cell 1 and anaerobic treatment in Cell 2. Cell 3 was planted with Typha latifolia with an inserted layer of brick rubble (for phosphorus removal). Locally grown reed, Phragmites karka was planted in Cell 4. COD was reduced from 8420 mg/l 3000 from Cell 1 to the outlet of Cell 4. Likewise other parameters: total and dissolved solids, ammonium and total nitrogen, and total P, indicated declining trends at the 4-celled CW effluent. This study reveals how high strength distillery wastewater strongly impacts morphology, aeration anatomy in the chiseled plant tissues, reed growth; and composition of the biofilm in the specialized substratum. The reliability of a CW for organic and nutrients reduction, in association with a poorly performing conventional system is discussed. There is an immense potential for appropriately designed constructed wetlands to improve high strength wastewaters in India.
Use of constructed wetlands for acid mine drainage abatement and stream restoration
Authors: Brenner F.J.
Published: May 2018

Constructed wetlands have been used for over two decades for the treatment of acid mine drainage (AMD). Through a variety of physical, chemical, biological processes, these wetlands are effective in reducing acidity and removing up to 99% of iron and aluminium from AMD, but they only remove 20-30% of the manganese loading. The Slippery Rock Creek watershed in northwestern, Pennsylvania has been adversely impacted by acid mine drainage (AMD) for over 100 years with 74 mine discharges contributing a total of 1,228.8 kg, 282 kg and 69 kg/day of sulfuric acid, iron and aluminium, respectively to receiving streams. In the Slippery Rock Creek Watershed, aerobic and vertical flow wetlands, along with limestone drains and vertical flow limestone beds help to restore acid mine drainage impacted streams. Since 1995, the construction of seven passive treatment systems currently contribute 192.8 kg of alkalinity and remove 39% of the acid loading to a 4.83 km section of Slippery Rock Creek. When the eight passive treatment currently under construction are in operation, it is anticipated that there will be an additional 34.7% reduction in acidic loading to streams within the watershed. The cost of restoring all streams currently impacted by acid mine drainage within the Slippery Rock Creek watershed is currently estimated at $8,929,500.
Nutrient and heavy metal uptake and storage in constructed wetland systems in Arizona
Authors: Karpiscak M.M. , Whiteaker L.R. , Artiola J.F. , Foster K.E.
Published: May 2018

The Constructed Ecosystems Research Facility (CERF) was conceived in the early 1980s as a test facility to explore the potential for using plants to treat wastewater in the arid west of the USA. One of the major issues that has been identified in the use of constructed wetland technology is plant nutrient uptake and tissue storage of nutrients as well as heavy metals. Our approach to understanding plant uptake and storage has been to look at both controlled conditions in constructed systems and background concentrations in natural systems. Plant tissues have been collected and analyzed from natural systems and from controlled systems receiving either wastewater or municipal water. Plants studied included the herbaceous species Anemopsis californica (Yerba mansa), Scirpus spp. (bulrush) and Typha domingensis (cattail), and tree species Fraxinus velutina (ash), Populus fremontii (cottonwood) and Salix spp. (willow). Data indicate that uptake varies not only among plant species, but also among chemical species, depending upon water quality within the wetlands. Leaf tissues of Fraxinus, Salix and Populus, contained the lowest amounts of nutrients and heavy metals studied (Na, P, K, Cu, Pb and Zn), while the root tissues of the herbaceous plants generally had the highest concentrations.
A constructed surface flow wetland for treating agricultural waste waters
Authors: Borin M. , Bonaiti G. , Santamaria G. , Giardini L.
Published: May 2018

A study was conducted between December 1997 and December 1998 in NE Italy on a 3,200 m2 surface flow vegetated wetland receiving agricultural drainage water from a cultivated field of about 6 ha and occasional applications of organic wastes. The study aimed at evaluating: 1) biomass and seasonal nitrogen dynamics in above- and below-ground biomass of Phragmites australis Cav. (Trin.) and Typha latifolia (L.) grown in separate zones; 2) the effectiveness of the wetland in removing nutrients and sediments coming from the fields; 3) the possibility that wetland could treat occasional applications of organic wastes and 4) to collect some general information on whether the wetland can receive heavy loads coming from storm water runoff.

Monthly observations showed that, in both species, aboveground biomass, nitrogen concentration and nitrogen content reached maximum values in summer and minimum values in winter. The contrary occurred in below-ground biomass. The total input of water in the wetland was 66,000 m3 ha-1, of which 7,700 were drained. Total nitrogen input was 526 kg ha-1, of which 58 were discharged out of the wetland.
Treatment of stormwater runoff from row crop farming in Ruskin, Florida
Authors: Rushton B.T. , Bahk B.M.
Published: May 2018

A wet-detention pond, constructed to treat agricultural runoff from winter vegetables, was studied to document constituent concentrations, measure hydrology and analyze conditions in the treatment system. The efficiency of the pond to remove pollutants was affected by the unseasonable amount of rainfall induced by the El Niño phenomenon and the succeeding dra La Niña year. During the two years of study (50 rain events), about 90 per cent of all the pollutant loads for potentially toxic metals entered the pond during five El Niño storms; and since higher pollutant loads are often more easily reduced these conditions contributed to the greater per cent reduction of metals during 1998. Another condition which may have enhanced constituent reduction was made possible by the newly evacuated sediments, since clean soils provide more attachment sites for constituent removal. Annual data show pollutant load reductions for 1998 were greater than 90 per cent for most metals, but for 1999 reduction was about 60 per cent. In contrast, inorganic nutrient removal was better in 1999 (> 80 per cent) than during 1998 (to 70 per cent). Organic nitrogen had the poorest removal for both years (20 to 40 per cent). Total phosphorus levels were measured at high median concentrations (1 mg/L at the inflow) compared to other studies for stormwater runoff.
River water quality improvement by natural and constructed wetland systems in the tropical semi-arid region of Northeastern Brazil
Authors: de Ceballos B.S.O. , Oliveira H. , Meira C.M.B.S. , Konig A. , Guimarães A.O. , de Souza J.T.
Published: May 2018

The efficiencies of a natural Typha spp wetland (Wn) formed on a river bed and its effluent treatment in a constructed wetland (Wc, subsurface horizontal flow) were investigated in northeastern Brazil (Paraiba State). The Wc system (12 tanks with stone gravel, 4.13 m2, 0.22 m3, 20 Typha spp rhizomes. m-2 each, with 38, 29, and 19 mm.d-1 hydraulic loadings, and 5, 7, and 10 days HRT) was fed daily with effluent from a Wn. Wn removal presented the highest values after Typha spp were cut during the 5th week. Removal values were (1st and 2nd periods or before and after cutting): 75% and 81% BOD5; 10-53% total phosphorus; 13%-55% ammonia; 89%-91% FC; 90-96% coliphages and bacteriophages. Wc removals increased with time with best results on 10d HRT. Removals were also higher in the 2nd period: 74%-78% BOD5; 58%-82% ammonia; 90% FC; 94-98% FS; and 92%-96% coliphages and bacteriophages. Despite the high remaining values of FC (1.4×104 CFU/100 ml) and FX (4×103 CFU/100 ml), the removals were satisfactory and HRT dependent, suggesting a gradual optimization of the system with time. The Wc exhibited good efficiency for improving water quality from polluted river.
Compartmental model for organic matter digestion in facultative ponds
Authors: Giraldo E. , Garzón A.
Published: May 2018

A model has been developed for the digestion of organic matter in facultative ponds in tropical regions. Complete mixing has been assumed for the aerobic and anaerobic compartments. Settling, aerobic layer oxidation, and anaerobic layer methanogenesis are the main processes for organic matter removal in the water column. Exchange processes between layers are dispersive or soluble exchange, solubilization and transport of organic matter from sediments to water column are also taken into account. Degradation of organic matter in the sediments produces gaseous emissions to the water column. The exchange between bubbles ascending and the water column was measured. The model was calibrated with data obtained from a pilot facultative pond built in Muña Reservoir in Bogotá. The pond was sampled during 4 months to compare data between its water hyacinth covered section and uncovered section. The results clearly show the relative importance of different BOD removal processes in facultative ponds and suggest modifications to further improve performance. The results from the model suggest that internal loadings to facultative ponds due to solubilization and return of organic matter from the sediments to the aerobic layer greatly influence the soluble BOD effluent concentration. Aerobic degradation activity in the facultative pond does not affect significantly the effluent concentration. Anaerobic degradation activity in the facultative pond can more easily achieve increases in the removal efficiencies of BOD.
Sludge accumulation in polishing ponds treating anaerobically digested wastewater
Authors: Cavalcanti P. , van Haandel A. , Lettinga G.
Published: May 2018

When ponds are used for wastewater treatment, settleable solids will form a steadily growing bottom sludge layer, which reduces their effective volume. Eventually this sludge must be removed to ensure that the pond maintains the required retention time to keep performing properly. The settleable solids may either be present in the influent or they are formed during the treatment as a result of algal flocculation.

An experimental investigation was carried out to evaluate bottom sludge accumulation in a polishing pond used for treatment of UASB effluent. The mass and composition of the bottom sludge formed in a polishing pond was evaluated after the pilot scale pond had been in operation for 1 year and about 60 m3 of digested wastewater had been treated per m3 of pond. The bottom sludge mass represented a solids accumulation of 70 g per m3 of digested wastewater. About half of these solids were the result of settling of influent solids in the first part of the pond, while the other half was attributable to settling of algae, formed in the pond. It is concluded that the bottom sludge growth in a polishing pond is so low, that desludging during the useful life span of the pond will most likely not be necessary. This leads to the important conclusion that excess sludge discharge from UASB reactors (a major factor in operational costs) may be omitted, if a polishing pond is used for post-treatment. The bottom sludge had a high volatile solids concentration (58%) and the macronutrient fractions were also high (3.9% N and 1.1% P of the TSS mass). The bottom sludge was stable and could be dried directly without problems. The hygienic quality of the bottom sludge was very poor: about half the influent helminth eggs during one year of operation were found in the bottom sludge and the faecal coliform concentration was very high.
Development of an internet-based rainfall atlas for Alabama
Authors: Durrans S.R. , Brown P.A.
Published: May 2018

In the United States, rainfall information needed for intensity-duration-frequency (IDF) curves or design storm hyetographs can be found in TP 40, HYDRO-35, and the NOAA Atlas 2. Additional rainfall data collected since the dates of those publications, and improved methods for statistical treatment of data, have motivated update studies in several regions of the United States. One of the new studies has been performed for the State of Alabama. Results of the Alabama study are embodied in an internet-based graphical user interface, which permits users to interactively point and click on a geographical location of interest, and have IDF curves and/or storm hyetographs returned on demand. Reactions to the internet-based rainfall atlas have been promising, and have led to additional work for the National Weather Service, Office of Hydrologic Development.
Comparison of rain gauge and radar data as input to an urban rainfall-runoff model
Authors: Quirmbach M. , Schultz G.A.
Published: May 2018

This paper presents an application of radar data (DX-product of the German Weather Service) with a high resolution in space (1° × 1 km) and time (Δt = 5 minutes) in urban hydrology. The radar data and data of rain gauges with different locations in the test catchment were compared concerning their suitability as input into an urban rainfall-runoff model. In order to evaluate the accuracy of model simulation results, five evaluation criteria have been specified which are relevant for an efficient management of sewer systems and wastewater treatment plants. The results demonstrate that radar data should be used in urban hydrology if distances > 4 km between rain gauge and catchment exist and for catchments with a density of rain gauges smaller than 1 rain gauge per 16 km2.
On the properties of stochastic intermittency in rainfall processes
Authors: Molini A. , La Barbera P. , Lanza L.G.
Published: May 2018

In this work we propose a mixed approach to deal with the modelling of rainfall events, based on the analysis of geometrical and statistical properties of rain intermittency in time, combined with the predictability power derived from the analysis of no-rain periods distribution and from the binary decomposition of the rain signal. Some recent hypotheses on the nature of rain intermittency are reviewed too. In particular, the internal intermittent structure of a high resolution pluviometric time series covering one decade and recorded at the tipping bucket station of the University of Genova is analysed, by separating the internal intermittency of rainfall events from the inter-arrival process through a simple geometrical filtering procedure. In this way it is possible to associate no-rain intervals with a probability distribution both in virtue of their position within the event and their percentage. From this analysis, an invariant probability distribution for the no-rain periods within the events is obtained at different aggregation levels and its satisfactory agreement with a typical extreme value distribution is shown.
X-Band local area weather radar – preliminary calibration results
Authors: Jensen N.E.
Published: May 2018

DHI has developed a cost-effective X-Band Local Area Weather Radar (LAWR) with a typical range (radius) of 60 km, 500 × 500 m areal resolution and 253 reflection levels. The development is performed in a co-operation with a number of European partners, including Danish Meteorological Institute. The specifications of the weather radar and preliminary results from the calibration are presented. Good calibration results have been obtained using high-resolution rain gauges.
Anoxic transformations of wastewater organic matter in sewers – process kinetics, model concept and wastewater treatment potential
Authors: Abdul-Talib S. , Hvitved-Jacobsen T. , Vollertsen J. , Ujang Z.
Published: May 2018

The sewer is an integral part of the urban wastewater system: the sewer, the wastewater treatment plant and the local receiving waters. The sewer is a reactor for microbial changes of the wastewater during transport, affecting the quality of the wastewater and thereby the successive treatment processes or receiving water impacts during combined sewer overflows. This paper presents the results of studies on anoxic processes, namely denitrification, in the bulk water phase of wastewater as it occurs in sewers. Experiments conducted on 12 different wastewater samples have shown that the denitrification process in the bulk wastewater can be simplified by the reduction of nitrate to nitrogen with significant accumulation of nitrite in the water phase. Utilization of nitrate was observed not to be limited by nitrate for concentrations above 5 gNO3-N/m3. The denitrification rates, under conditions of excess substrate and electron acceptor, were found to be in the range of 0.8-2.0 g NO3-N/(m3h). A discussion on the interaction of the sewer processes and the effects on a downstream located wastewater treatment plant (WWTP) is provided.
The influence of stormwater treatment on the hydraulic and pollution load – balance for an entire river basin
Authors: Bode H. , Weyand M.
Published: May 2018

The installation of about 500 stormwater detention facilities (SDFs) led to a significant drop of the pollution originating from stormwater runoff in the river basin of the Ruhr which covers 4,488 km2. The German technical directives on the design of SDFs are briefly outlined and the specific costs for such plants are given. The average costs for one kilogram COD held back by SDFs in combined systems amount to € 3.73 (calculated without consideration of the subsequent removal in the municipal wastewater treatment plant (WWTP)). The tank volume for stormwater storage can be minimised by application of real-time management systems which allow a dynamic operation of all SDFs in a catchment area.
The impact of the controlled emptying of in-sewer storage on wastewater treatment plant performance
Authors: Jack A.G. , Ashley R.M.
Published: May 2018

The use of in-sewer storage is generally considered to be an effective means of minimising the effects of intermittent discharges into receiving watercourses during combined flows. Despite this, very little information is available about the consequential effects these flows may have on recipient wastewater treatment plant performance. Typical problems may include biomass washout (hydraulic), and reduced biological reactor performance due to dilute loading (biological). A study is described where detailed analysis was carried out to ascertain the consequential effects of prolonged dilute loading on an activated sludge wastewater treatment plant in Perth, Scotland. Consideration was given to likely storage volumes which may have been utilised in the catchment to resolve local problems. A comprehensive analysis of resulting treatment plant performance was carried out for variations in flow and various wet weather loadings. It is concluded that storage may cause little or no benefit with respect to ammonia total emissions due to reduced treatment of dry weather flows subsequent to the prolonged combined loading period. This was exacerbated by the long regeneration times of nitrifying bacteria. However, an overall benefit with respect to BOD total emissions would always be expected, as appropriately sized storage would retain the first foul flush at the CSOs, thereby compensating the increased emissions from the downstream wastewater treatment plant.
Assessment of stormwater impacts on an urban stream with a detention pond
Authors: Marsalek J. , Rochfort Q. , Grapentine L. , Brownlee B.
Published: May 2018

Impacts of urban development on a small creek with an on-stream stormwater pond, which was built to mitigate the effects of a 13-ha commercial plaza on creek flows, were assessed by investigations of the creek-pond system hydrology, water and sediment chemistry and toxicity, and benthic communities. The hydrology and conventional pollutant loadings of this system were dominated by the creek catchment (4.5 km2), which contributed more than 95% of the total flow; the rest was contributed by the plaza runoff which was less polluted than typical residential runoff. Conventional bioassays (Daphnia magna, Microtox™) did not indicate any confirmed acute toxicity in the creek flow, plaza drainage, or pond outflow. However, sediments accumulated in the pond were rather polluted and several sediment bioassays (including Sediment Microtox™) indicated their severe toxicity. In benthic community assessments, taxa richness and total counts of benthic organisms did not change much when moving from upstream to downstream of the pond. Thus, the pond accumulates sediments and toxicants and thereby prevents further degradation of the creek condition downstream of the plaza drainage outfall.
Use of phosphorus release batch tests for modelling an EBPR pilot plant
Authors: Tykesson E. , Aspegren H. , Henze M. , Nielsen P.H. , Jansen J. Ia C.
Published: May 2018

The aim of this study was to evaluate how routinely performed phosphorus release tests could be used when modelling enhanced biological phosphorus removal (EBPR) using activated sludge models such as ASM2d. A pilot plant with an extensive analysis programme was used as basis for the simulations. Without any calibration the prediction of phosphorus removal was poor and the initial release rates from the simulations were not similar to those found from the laboratory tests. A period with low organic loading was chosen as a calibration period. In this period averages of daily influent measurements were used as influent parameters. First, calibration was performed in order to fit effluent COD and MLVSS in the sludge. Next, the phosphorus content in the sludge was decreased to the measured level by decreasing the fermentation rate. Finally, the initial phosphorus release rate was calculated from a simulated batch test and the PHA uptake rate was increased to fit this release rate with the average initial rates from laboratory batch tests performed during the period. The calibrated model was verified with data from the subsequent period where acetate was dosed.
Model-based evaluation of a new upgrading concept for N-removal
Authors: Salem S. , Berends D. , Heijnen J.J. , van Loosdrecht M.C.M.
Published: May 2018

Mathematical modelling is considered a time and cost-saving tool for evaluation of new wastewater treatment concepts. Modelling can help to bridge the gap between lab and full-scale application. Bio-augmentation can be used to obtain nitrification in activated sludge systems with a limited aerobic sludge retention time. In the present study the potential for augmenting the endogenous nitrifying population is evaluated. Implementing a nitrification reactor in the sludge return line fed with sludge liquor with a high ammonia concentration leads to augmentation of the native nitrifying population. Since the behaviour of nitrifiers is relatively well known, a choice was made to evaluate this new concept mainly based on mathematical modelling. As an example an existing treatment plant (wwtp Walcheren, The Netherlands) that needed to be upgraded was used. A mathematical model, based on the TUDP model and implemented in AQUASIM was developed and used to evaluate the potential of this bioaugmentation in the return sludge line. A comparison was made between bio-augmentation and extending the existing aeration basins and anoxic tanks. The results of both modified systems were compared to give a quantitative basis for evaluation of benefits gained from such a system. If the plant is upgraded by conventional extension it needs an increase in volume of about 225%; using a bioaugmentation in the return sludge line the total volume of the tanks needs to be expanded by only 75% (including the side stream tanks). Based on the modelling results a decision was made to implement the bioaugmentation concept at full scale without further pilot scale testing, thereby strongly decreasing the scale-up period for this process.
Improving the predictions of ASM2d through modelling in practice
Authors: Larrea L. , Irizar I. , Hildago M.E.
Published: May 2018

The paper presents the adjustments carried out on the structure and in some default values of the kinetic coefficients of the ASM2d model in order to get an improved prediction for the experimental results obtained in pilot scale plants studies with different activated sludge treatment processes for carbon, nitrogen and phosphorous removal. In order to predict the high effluent filtered COD experimentally observed in high rate processes for carbon removal, a new model structure has been proposed, incorporating into the carbon model a soluble fraction of the slowly biodegradable substrate. Studies with the step feed and the alternating processes showed simultaneous nitrification-denitrification in aerated reactors which was predicted with increased values in the oxygen saturation coefficients for heterotrophic and autotrophic biomass. Both processes also showed loss of the denitrification capacity under unfavourable conditions, such us rains and low anoxic fraction, which required a very large decrease in the value of the reduction factor for denitrification so as to improve the predictions for effluent nitrate experimental results. Regarding phosphorus removal, the ASM2d model showed a satisfactory predictive capacity. For improved predictions of phosphorus release in anaerobic conditions, high values of the rate constant for storage of XPHA and low values of the anaerobic hydrolysis reduction factor were used. For phosphorus uptake in aerobic and anoxic conditions satisfactory predictions were obtained using the default values.
Experimental study and modelling of zinc and lead migration in sandy soils due to stormwater infiltration
Authors: Marcos L. , Legret M. , Raimbault G. , Le Cloirec P.
Published: May 2018

Heavy metals emitted by road traffic are contaminants of roadside soils and can potentially migrate through the soils down to groundwater during runoff water infiltration. Stormwater management requires a better understanding of the mechanisms involved in the transport and particularly chemical interactions between heavy metals and the solid matrix. Experiments with open dynamic systems and modelling with a mixing-cells-in-series model have been performed to identify the main reactions which govern the migration of zinc and lead in sandy soils. Binary and ternary exchange experiments have been performed and a numerical modelling was proposed to describe zinc and lead mobility in column experiments.
Impact of zinc roofing on urban runoff pollutant loads: the case of Paris
Authors: Gromaire M.C. , Chebbo G. , Constant A.
Published: May 2018

Previous research on the Marais catchment in Paris demonstrated the very high zinc and cadmium contamination of runoff from zinc roofing. Thus further investigations were aimed at evaluating the relative importance of this type of roofing in Paris and its potential contribution to zinc and cadmium loads in wet weather flows. According to these results, about 40% of the surface of roofs in Paris is covered with rolled zinc (1016 ha), and this proportion is not likely to vary significantly in the next years, due to architectural rules. The Zn and Cd concentrations measured in runoff from these roofs are in accordance with literature data on zinc corrosion rates, in the presence of SO2. On an annual scale, runoff from Parisian zinc roofs produces around 34 to 64 metric tonnes of zinc and 15 to 25 kg of cadmium, which is approximately half the load generated by runoff from total Paris.
The wave breaking phenomena as a tool for environmental friendly shore protection
Authors: Kabdaşli M.S. , Türker U.
Published: May 2018

An experimental study was carried out to evaluate the rate of energy dissipation during wave breaking and the dependence of dissipation on the breaker type. The splash mechanism that occurs just after the breaking is also examined based on knowledge of external and macroscopic properties of breakers only. During the experiments, it is observed that most of the energy is dissipated while the water jet formed during wave breaking hits the water surface. It has been found that the percentage of wave energy dissipated in plunging type waves is larger than in spilling type waves.