bluuebunny/crossref_metadata_2025 huggingface dataset:
Survival of indicators of bacterial and viral contamination in wastewater subjected to low temperatures and freezing: application to cold climate waste stabilisation ponds
Authors: Torrella F. , López J.P. , Banks C.J.
Published: May 2018

The survival of bacterial and viral pollution indicators and Salmonella in urban wastewaters under freezing conditions (-14°C for up to 60 days) is reported. Presumptive, total and faecal coliforms (PC, TC, FC), salmonellae and coliphages were tested. The dynamics of somatic coliphage (E. coli C) and F-pili specific coliphage inactivation were compared at 4°C and 25°C over various run times. On freezing of the wastewater, it was found that PC, TC and FC showed a first rapid phase (days) of inactivation followed by a slower second phase (up to 4 weeks) and then stabilisation at between 1-10% of the initial population size, depending on the wastewater sample used. Salmonella spp. were detectable in 0.1 ml of raw wastewater and were still detected up to 2 days after freezing but none were detected in 100 ml samples after 4, 42 and 60 days, although microbiologically similar but antigenically different forms were found. Viral indicators of pollution showed a slow but constant decrease in viability during the first month but then stabilised at between 10-20% survivors (10% in somatic E. coli C phages, 15.8% in somatic Salmonella phages and 17.9% in F-pili specific coliphages). Using electron microscopy, no difference in susceptibility to freezing could be detected with respect to morphological phage types, which were either small icosahedral particles or complex tailed phages. The study of viral indicators at 4°C versus 25°C showed a higher survival of the various coliphages over time at 4°C. F-pili specific leviviridae were particularly susceptible to the antiviral factors at 25°C and no viable units per ml were detected after one month at that temperature, whereas somatic coliphages were detected in higher numbers after this period, especially at 4°C.
Online sensing of volatile organic compounds in groundwater using mid-infrared fibre optic evanescent wave spectroscopy: a pilot scale test
Authors: Steiner H. , Staubmann K. , Allabashi R. , Fleischmann N. , Katzir A. , Reichlin Y. , Mizaikoff B.
Published: May 2018

A prototype sensing system for in-situ monitoring of volatile organic compounds in contaminated groundwater was tested at a pilot scale plant. The sensor consists of a commercially available Fourier transform infrared spectrometer, connected to a 6 m long infrared transparent silver halide fibre optic cable. A 10 cm long core-only section at the centre of the fibre is mounted on a sensor head and coated with a hydrophobic polymer layer, while the remaining fibre is protected by Teflon tubing and thus not in contact with the surrounding media. The sensor head was immersed into the monitoring wells of the pilot plant testing the sensor system under circumstances close to field conditions and typical for in-situ measurements. The pilot plant consists of a 1 m3 cubic tank filled with gravel. A pump is used to circulate water horizontally through the tank, simulating a natural aquifer. The evolution of the concentration of analytes injected into the system is monitored with time using the developed prototype sensing system. The results are validated by corresponding sampling and analysis with headspace gas chromatography.
Development of guidelines for improved hydraulic design of waste stabilisation ponds
Authors: Shilton A. , Harrison J.
Published: May 2018

Pond hydraulic behaviour is influenced by the inlet/outlet configuration, baffles and wind, but design information relating to these factors is still very limited. This paper reviews the development of “Guidelines for the Improved Hydraulic Design of Waste Stabilisation Ponds” and summarises some of the key findings and recommendations. This work was based on review of previous research, laboratory experimentation, field studies and mathematical modelling using computational fluid dynamics. The inlet design can have a significant influence on the flow regime in a pond. Poorly considered positioning of the inlet and the outlet can create hydraulic short-circuiting problems. As an example of the nature of the work undertaken in this project, the use of a small horizontal inlet pipe was compared against a vertical inlet design. A practical method of assessing the relative significance of wind versus inlet power input was presented. The application of this analysis may allow engineers to size inlet pipes to help control the flow patterns in ponds for efficient performance. Extensive testing has been undertaken on a wide range of baffle configurations. An example of this research showed how short stub baffles could provide similar improvements to longer “traditional” baffle designs, potentially offering significant savings in construction costs. For traditional baffle designs a minimum of two baffles is recommended. For the pond modelled in this work, it was found that any more than four baffles gave only marginal improvements.
Remote water quality monitoring “on-line” using LEO satellites
Authors: Stadler H. , Skritek P.
Published: May 2018

Low Earth Orbit Satellites (LEOS) provide world-wide “nomadic” data-communication using low-cost and low-power “cellular like” equipment. LEOS allow us to also exploit those regions, which up to now were inaccessible by land-based wireless or geostationary (GEO) satellite systems. First, this paper compares satellite systems and summarizes features of the ORBCOMM LEO-system used. In the main part, a detailed report is given on a hydrogeological prototype implementation for remote water-quality monitoring: setup, obtained results, conclusions and further aspects as well as cost comparisons. As a result, LEO satellite data transmission may be a reliable low-cost alternative even to GSM-SMS for low data volume applications.
Dynamic mathematical model of high rate algal ponds (HRAP)
Authors: Jupsin H. , Praet E. , Vasel J.-L.
Published: May 2018

This article presents a mathematical model to describe High-Rate Algal Ponds (HRAPs). The hydrodynamic behavior of the reactor is described as completely mixed tanks in series with recirculation. The hydrodynamic pattern is combined with a subset of River Water Quality Model 1 (RWQM1), including the main processes in liquid phase. Our aim is to develop models for WSPs and aerated lagoons, too, but we focused on HRAPs first for several reasons:• Sediments are usually less abundant in HRAP and can be neglected• Stratification is not observed and state variables are constant in a reactor cross section• Due to the system's geometry, the reactor is quite similar to a plugflow type reactor with recirculation, with a simple advection term.

The model is based on mass balances and includes the following processes:Phytoplankton growth with NO3-, NO2- and death• Aerobic growth of heterotrophs with NO3-, NH4+ and respiration• Anoxic growth of heterotrophs with NO3-, NO2- and anoxic respiration• Growth of nitrifiers (two stages) and respiration.

The differences with regard to RWQM1 are that we included a limiting term associated with inorganic carbon on the growth rate of algae and nitrifiers, gas transfers are taken into account by the familiar Adeney equation, and a subroutine calculates light intensity at the water surface. This article presents our first simulations.
The reasons behind the performance superiority of a high rate algal pond over three facultative ponds in series
Authors: El Hamouri B. , Rami A. , Vasel J.-L.
Published: May 2018

Results from a tracer study were used to determine and to compare actual and standard (k20°C) first order reaction rate constants for COD removal in a High Rate Algal Pond (HRAP) and in 3 facultative ponds (FP) in series. An annual average k20°C of 0.123 day-1 was found for the HRAP while the values of 0.097, 0.025 and 0.003 d-1 were found for facultative ponds 1, 2 and 3 respectively. Also, comparing nominal and tracer study hydraulic retention times showed large differences for the FP but not for the HRAP indicating that the former were suffering from severe short-circuiting. Loading rate within the range of operation exhibited a positive correlation with k20°C for the HRAP but did not show such a relationship for any of the FP. Optimal chlorophyll-a concentration was found to be 3 mg/l for the HRAP and only 1.1 mg/l for the FP. Pollutant specific removal rates (SRR), that translate the hydrodynamic efficiency and the rate of COD biodegradation into pond performance per m2 and per day were calculated. They show that the adoption of the HRAP in place of a series of 3 FP reduces the net land area requirement (LAR) by at least 40%.
Selenium and nitrate removal from agricultural drainage using the AIWPS® technology
Authors: Green F.B. , Lundquist T.J. , Quinn N.W.T. , Zarate M.A. , Zubieta I.X. , Oswald W.J.
Published: May 2018

Monthly Maximum Discharge Limits (MMDL) have been established for selenium in irrigation drainage by the State of California and the U.S. Environmental Protection Agency following observations of avian teratogenesis at the Kesterson Reservoir in the San Joaquin Valley of California. As a result of these and other adverse effects, farmers and drainage districts on the western side of the San Joaquin Valley must reduce selenium concentrations in irrigation drainage discharged to the San Joaquin River. Drainage treatment will be required in the near future to meet existing MMDL and future Total Maximum Discharge Limits (TMDL) for the San Joaquin River. A 0.4-hectare Algal Bacterial Selenium Removal (ABSR) Facility was designed and constructed at the Panoche Drainage District in 1995 and 1996 using the Advanced Integrated Wastewater Pond Systems® or AIWPS® Technology. Each of two physically identical systems combined a Reduction Pond (RP) with a shallow, peripheral algal High Rate Pond (HRP). A Dissolved Air Flotation (DAF) unit and a slow sand filter were used to remove particulate selenium from the effluent of each system. The two systems were operated under different modes of operation and the bacterial substrate varied in each system. The rates of nitrate and selenium removal were compared. Microalgae were harvested using DAF and used as a carbon-rich substrate for nitrate- and selenate-reducing bacteria. Mass removals of total soluble selenium of 77% or greater were achieved over a three-year period. Nitrate and selenate were removed by assimiliatory and dissimiliatory bacterial reduction, and nitrate was also removed by algal assimilation. The final removal of particulate selenium is the focus of ongoing investigations. The removal of particulate selenium is expected to increase the overall removal of selenium to greater than 90% and would allow farmers and drainage districts to discharge irrigation drainage in compliance with regulatory discharge limits.
Removal of organics and nutrients from tannery effluent by advanced integrated wastewater pond systems technology
Authors: Tadesse I. , Isoaho S.A. , Green F.B. , Puhakka J.A.
Published: May 2018

In this study, a pilot-scale experiment was carried out on a pre-settled combined tannery effluent from Modjo tannery, Ethiopia, to evaluate the feasibility of the Advanced Integrated Wastewater Pond Systems® or AIWPS® Technology, for the treatment of tannery effluent. The pilot-scale AIWPS® Facility was comprised of an Advanced Facultative Pond (AFP), Secondary Facultative Pond (SFP) and Maturation Pond (MP) all arranged in series. Three feed phases with low, moderate and overloading organic loading rates were applied to assess the organics and nutrients removal performances of the AIWPS® reactors. The overall organics removal performance of the AIWPS® Process was high, with removal efficiencies in the range of 90-98% for BOD5 and 86-92% for COD. Among the AIWPS® reactors, the AFP attained the highest organics removal efficiency with a BOD5 removal of 70-89%. BOD5 removal efficiencies of the SFP and MP were 34-65% and 30-40%, respectively. The AFP was also able to withstand a much higher volumetric organic loading rate (70% more) than the conventional open anaerobic ponds. The drop in BOD5 removal efficiency of the AFP at the overloading condition was only 7%, while the corresponding drop in the SFP was 29%. AIWPS® reactors achieved a cumulative ammonia removal efficiency of 85%. The highest ammonia removal (50-60%) occurred in the SFP, followed by the MP with removal efficiency of 20-26%. At the overloading condition the overall ammonia removal efficiency of the AIWPS® Facility decreased by 50%, while the BOD5 organics removal dropped by only 6%, signifying the higher vulnerability of ammonia removal mechanism to high loading conditions than the organics removal. The phosphorus removal in the AIWPS® Facility was erratic, with highest removal (up to 75%) occurring in the AFP. The lack of H2S odour nuisance from the AFP was mainly due to the proliferation of sulphide oxidizing anoxygenic photosynthetic pink bacteria of the genera: Thiocystis, Rhodobacter, Rhodospirillum and Rhodopseudomonas in the upper solar illuminated water layers of the AFP.
Linking pond and wetland treatment: performance of domestic and farm systems in New Zealand
Authors: Tanner C.C. , Sukias J.P.S.
Published: May 2018

Wetland systems have been used extensively to supplement and upgrade waste stabilisation pond treatment systems in New Zealand. Key attributes of wetlands, such as low operational costs, minimal reliance on machinery and external energy inputs, high wildlife habitat values, and perceived “naturalness”, complement those of pond systems. Performance data for a range of New Zealand post-pond constructed wetlands treating sewage, dairy farm and piggery wastewaters show BOD and SS concentrations can be readily reduced to low levels. Bacterial indicators are commonly reduced by at least one log unit, but levels below 500 cfu (100 mls)-1 are difficult to achieve consistently. Nutrient removal efficiency is highly dependent on loading rates and wastewater characteristics. Plant establishment and maintenance, wildlife management, hydraulic design and adequacy of preceding treatment are identified as key practical issues in the implementation and management of constructed wetland systems.
Effect of duckweed cover on greenhouse gas emissions and odour release from waste stabilisation ponds
Authors: van der Steen N.P. , Nakiboneka P. , Mangalika L. , Ferrer A.V.M. , Gijzen H.J.
Published: May 2018

Treatment of wastewater in stabilisation pond systems prevents the negative environmental impact of uncontrolled disposal of sewage. However, even a natural treatment system may generate secondary negative environmental impacts in terms of energy consumption, emission of greenhouse gases and emission of odorous compounds. Whereas natural systems have an advantage over electro-mechanical systems in that they use less hardware and less energy, it is not yet known whether secondary environmental effects in the form of greenhouse gas emissions are lower for these systems. This research intends to be a first step in the direction of answering this question by assessing gas emissions from two types of natural systems, namely algae-based and duckweed-based stabilisation ponds. The H2S volatilisation from laboratory scale pond-reactors has been determined by drawing the air above the water surface continuously through a solution of 1 M NaOH for absorption of sulphide. The amount of H2S that volatilised from the algae pond-reactor, and was trapped in the NaOH trap, was found to be 2.5-86 mg/m2/day. The H2S volatilisation from the duckweed pond-reactor was found to be negligible, even though the sulphide concentration was 9.7 mg/l S2-. The duckweed cover was a physical barrier for volatilisation, since bubbles were trapped in the cover. In addition the duckweed layer was found to be a favourable environment for both aerobic sulphide oxidisers (Beggiatoa gigantae) as well as for photosynthetic purple sulphur bacteria belonging to the genus Chromatium. These may also have contributed to the prevention of H2S volatilisation. Results on methane emissions were not conclusive so far, but the same mechanisms that prevent H2S volatilisation may also prevent methane volatilisation. Therefore it was concluded that duckweed covers on stabilisation ponds may reduce the emission of both odorous and greenhouse gases.
Seasonal influence of waste stabilisation pond effluent on DAF/F (dissolved air flotation/filtration) process operation
Authors: Buisine F. , Oemcke D.
Published: May 2018

The Bolivar wastewater treatment plant (WWTP), North of Adelaide, South Australia encompasses the largest waste stabilisation pond (WSP) system in the Southern hemisphere. The wastewater effluent will ultimately be fully reused for agriculture irrigation. A dissolved air flotation/filtration (DAF/F) plant was installed for tertiary treatment downstream of the stabilisation lagoons for supply to the irrigation scheme. Chemical treatment in the form of coagulation and flocculation is required to assist the separation process.

The DAF/F plant operation is highly dependent on the raw water algal population. Seasonal variations seem to be the main abiotic factors affecting the algal population growth. Significant doses of chemical can be required to respond to rapid changes of water quality. United Water International is currently assessing the appropriate chemical treatment for short term response, and is also working with Flinders University of South Australia on determining ways to manage the lagoons and to control the water quality feeding the DAF/F plant in the long term. This paper outlines the effect of seasonal variations of WSP effluent quality on the DAF/F process operation, the findings for an adapted chemical treatment, and the eventual possibilities for lagoon management.
Improving the effluent of small wastewater treatment plants by bacteria reduction and nutrient removal with an algal biofilm
Authors: Schumacher G. , Sekoulov I.
Published: May 2018

In wastewater ponds, bacteria numbers decrease considerably in the case of raised algae concentrations in the effluent. This shows that algae have a high potential for bacteria reduction in wastewater. Simultaneously, algae remove nutrients from the water for the formation of biomass. However, suspended algae also cause a high secondary pollution in the effluent of wastewater treatment plants. By using attached algae, as they are frequently observed as an algal biofilm in the effluent of wastewater treatment plants, the problem of separation of algae and water can be avoided. Furthermore, the algae can be removed simply from the water. In this study the possibilities for bacteria reduction and nutrient removal were examined with the aid of an algal biofilm. The results show that an algal biofilm process can be used for cases where small amounts of wastewater should be treated and a high quality of the effluent should be attained.
Phenotypic population characteristics of the enterococci in wastewater and animal faeces: implications for the new European directive on the quality of bathing waters
Authors: Wallis J.L. , Taylor H.D.
Published: May 2018

Faecal pollution of recreational bathing waters may derive from point sources of various wastewaters or from more diffuse sources such as run-off of agricultural wastes. The paper describes the application of population similarity studies to the enterococcal flora of various animal faeces and municipal wastewaters as a means of distinguishing human from animal faecal material. A simplified phenotypic testing technique (PhenePlate, PhP) was used to study the fermentation kinetics of eleven carbohydrates by all bacterial isolates. Enterococcal isolates (1,766) from six sources were investigated. Enterococcal population diversity (measured as Simpson's Diversity Index) in wastewater samples was high (mean Di = 0.95) compared with those of non-human faeces. The mean diversity of isolates in seabird faeces was 0.72, in sheep and donkey faeces 0.44, in dog faeces 0.42 and in cattle faeces 0.32. Analysis of population similarity coefficients demonstrated that faeces from sheep and cattle showed the greatest similarity (Sp = 0.72). Sheep and cattle faeces demonstrated a low similarity to municipal wastewater samples. This would suggest that population similarity studies might be a useful tool for distinguishing the relative contributions of municipal wastewater and agricultural run-off to bathing water pollution. The PhP procedure identified a specific PhP type that appears to have high specificity to non-human faeces. It may, therefore, represent an important tool in source tracking. Additional phenotypic and genotypic analysis of PhP types that demonstrate a high degree of source specificity is required. The benefits and limitations of the use of population similarity studies to distinguish pollution sources are discussed in comparison with other source tracking approaches and the implications of these developments for future European Union legislation on the quality of bathing waters are discussed.
Predation of Cryptosporidium oocysts by protozoa and rotifers: implications for water quality and public health
Authors: Stott R. , May E. , Ramirez E. , Warren A.
Published: May 2018

Predation by free-living protozoa and rotifers was investigated as a possible mechanism for the removal of Cryptosporidium parvum oocysts in aquatic ecosystems including wastewater treatment plants. Free-living ciliated protozoa (Stylonychia mytilus, Paramecium caudatum and an unidentified wastewater wetland ciliate), an amoeba (Acanthamoeba culbertsoni) and rotifers, all commonly found in aquatic ecosystems, were exposed to varying doses of C. parvum oocysts. All organisms investigated ingested oocysts. Predation activity and rates of ingestion varied with predator species and prey density. Ciliated protozoa demonstrated greater predation activity than A. culbertsoni or rotifers when exposed to 2 × 105 oocyst/mL for up to 3 h. Greatest predation after 1 h exposure was observed in P. caudatum, the largest ciliate, with on average 1.9 oocysts/cell (range 0-9 oocysts/cell). Stylonychia mytilus and the wetland ciliate had a similar mean ingestion of around 0.3 oocysts/cell, with numbers internalised ranging from 0-3 oocysts/cell. Rotifers ingested on average 1.6 oocysts/individual (range 0-7 oocysts/individual) whilst amoebae ingested on average 1.8 oocysts/cell after 2 h exposure (up to 3 oocysts/cell). Grazing activity by P. caudatum was demonstrated at a variety of prey levels ranging from 9 to 9,000 oocysts. Numbers of oocysts internalised by Paramecium frequently exceeded the reported human infective dose of 30 oocysts. In general, numbers of internalised oocysts increased with incubation time of up to 20-30 min although the rate of accumulation was slower at lower dose levels. The significance of predation on the fate of Cryptosporidium oocysts in the environment is discussed.
Comparative reduction of Norwalk virus, poliovirus type 1, F+ RNA coliphage MS2 and Escherichia coli in miniature soil columns
Authors: Meschke J.S. , Sobsey M.D.
Published: May 2018

Norwalk-like viruses (NLVs) are important agents of waterborne illness and have been linked to several groundwater-related outbreaks. The presence of human enteric viruses, in particular the presence of NLVs, is difficult to detect in the environment. Consequently, surrogate organisms are typically used as indicators of viruses from faecal contamination. Whether traditional bacterial indicators are reliable indicators for viral pathogens remains uncertain. Few studies have directly compared mobility and reduction of bacterial indicators (e.g. coliforms, Escherichia coli) and other surrogate indicators (coliphages) with pathogenic human viruses in soil systems. In this study the mobility and comparative reduction of the prototype NLV, Norwalk Virus (NV), was compared to poliovirus 1 (PV1), a bacterial indicator (E. coli, EC) and a viral indicator (coliphage MS2) through miniature soil columns. Replicate, 10cm deep, miniature columns were prepared using three soils representing a range of soil textures (sand, organic muck, and clay). Columns were initially conditioned, then incubated at 10-14°C, dosed twice weekly for 8 weeks with one column pore volume of virus-seeded groundwater per dose, followed by 8 weeks of dosing with one column pore volume per dose of unseeded, simulated rainwater. Columns were allowed to drain after each dosing until an effluent volume equivalent to an applied dose was collected. Column effluents and doses were assayed for all viruses and EC. Rapid mobility with minimal reduction was observed for all organisms in the sand. Similar reductions were observed in organic muck for most organisms but NV showed a greater reduction. No organisms were shown to pass through the clay columns. Elution of viruses, in particular PV1, from the columns was gradual. After cessation of microbe dosing, E. coli was less detectable than viruses in column effluents and, therefore, unreliable as a virus indicator.
Detection, enumeration and isolation of strains carrying the stx2 gene from urban sewage
Authors: Blanch A.R. , García-Aljaro C. , Muniesa M. , Jofre J.
Published: May 2018

Verotoxigenic Escherichia coli strains have been related with waterborne outbreaks. Besides 0157:H7, several serotypes of E. coli and other enterobacteria have been implicated in outbreaks and reported to carry the shiga toxin genes. Shiga toxins, stx1 and stx2, are important virulence factors of these strains. These genes have been linked to bacteriophages and consequently are susceptible to lateral transmission. To better understand the ecology of these genes a study of the presence of the shiga toxin 2 gene (stx2) among coliform bacteria present in sewage samples was carried out. A procedure based on colony hybridisation was developed for the isolation of enterobacteria carrying this gene. Colony growth on Chromocult® agar was transferred to a membrane and hybridised with a gene specific probe. The procedure allowed detection of about one colony carrying the gene among around 1,000 faecal coliform colonies. The numbers of bacteria carrying the gene in sewage were also estimated by PCR indicating that the numbers of bacteria carrying the stx2 gene were about 1/1,000 faecal coliforms. The detected numbers by both methods were similar. Positive colony hybridisation was detected in four sewage origins. Fifty-two colonies showing positive signal were isolated from the Chromocult® agar plates, confirmed to be stx2 positive by PCR and phenotypically characterised. Results of the characterisation showed certain diversity among the isolates even in isolates from the same sample. Most of these isolates would not have been isolated with the methods regularly used for the isolation of E. coli 0157:H7 strains. The method will allow study of the numbers and characteristics of bacteria carrying the stx2 gene in different water environments and isolate them in order to determine their role in the spread of the gene.
A detection method for Legionella spp in (cooling) water: fluorescent in situ hybridisation (FISH) on whole bacteria
Authors: Declerck P. , Verelst L. , Duvivier L. , Van Damme A. , Ollevier F.
Published: May 2018

Although traditional culture methods are appropriate for detection of Legionella species, such culture takes several days. Rapid detection (<24 h) of individual Legionella is possible using fluorescent in situ hybridisation (FISH) on whole bacteria. Water samples were filtered and the concentrated bacteria were immediately detected (without culture) with a fluorescence microscope following appropriate labelling. The detection level was very high and quantification was possible. For the detection of all Legionella spp. the probe LEG705 was used, complementary to a 16S rRNA sequence conserved in all Legionella spp. For specific detection of L. pneumophila the probe LEGPNE1 was used. This probe is designed against a variable domain of the 16S rRNA sequence from L. pneumophila. CY3 and FLUOS labels were tested and CY3 showed clearly detectable bacteria with minimum background staining. This FISH technique is very sensitive, fast, reliable and individual bacteria are easily detected.
The role of pH in the organic material solubilization of domestic sludge in anaerobic digestion
Authors: Yangin Gomec C. , Speece R.E.
Published: May 2018

The effect of pH on anaerobic solubilization of domestic primary sludge and activated sludge was investigated and compared. Anaerobic solubilization was carried out in continuously stirred anaerobic reactors at mesophilic temperature (35°C) and pH was fixed at 6.5 (pH-controlled). Many researches reported the serious effects of pH on the solubilization of organic materials. Thus, the aim of pH control in the reactors consisting of domestic primary and activated sludges, was the evaluation of retardation in hydrolysis/acidogenesis at low pH values. Since primary and activated sludges have different biodegradation characteristics, results were compared. Results indicated that the destruction of Total Suspended Solids (TSS) and Volatile Suspended Solids (VSS) were better in the pH-controlled reactors. In both sludges, acetic acid was the main Volatile Fatty Acid (VFA) produced. In the pH-controlled reactors, VSS reduction was found to be 72% in about 20 days in the anaerobic digestion of activated sludge, whereas for the same interval VSS reduction could only be achieved by 32% in primary sludge at 35°C. When primary sludge was used as substrate, the pH-uncontrolled and the pH-controlled reactors removed VSS with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). However, production of VFAs and SCOD was ceased after 5 days in the pH-controlled reactor whereas VFAs and SCOD production continued after 5 days in the pH-uncontrolled reactor, which indicated that hydrolysis and fermentation did not complete and continued longer. On the other hand; in either the pH-uncontrolled or the pH-controlled reactor of activated sludge, VSS was not removed with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). It was apparent that solubilization was occurring, however this solubilization was not observed as VFA production. When total methane production and total COD (CODtot) removal were estimated using VSS removal in both types of sludges, results indicated that pH control enhanced biogas productions as well as CODtot removals.
Inactivation of Salmonella spp. from secondary and tertiary effluents by UV irradiation
Authors: Keller R. , Passamani F. , Vaz L. , Cassini S.T. , Gonçalves R.F.
Published: May 2018

The aim of this study was to verify the efficiency of UV irradiation in the inactivation of Salmonella spp. in treated wastewater with different levels of turbidity and exposed to increasing doses of UV irradiation. Experiments were carried out in a batch reactor and in a real scale reactor. Salmonellae obtained from clinical samples were seeded into autoclaved wastewater collected from a wastewater treatment plant (WWTP) comprising an association of a UASB reactor followed by three submerged aerated biofilters (BAF) and one tertiary filter. The results showed that salmonellae were not inactivated in effluents from the UASB reactor indicating that the presence of suspended solids was an important obstacle to UV penetration in bacteria. However, UV irradiation was efficient in inactivating Salmonella of effluents from aerated secondary and tertiary biofilm reactors.
Quantitative risk assessment of Cryptosporidium in surface water treatment
Authors: Medema G.J. , Hoogenboezem W. , van der Veer A.J. , Ketelaars H.A.M. , Hijnen W.A.M. , Nobel P.J.
Published: May 2018

Quantitative microbiological risk assessment requires quantitative data to assess consumer exposure to pathogens and the resulting health risk. The aim of this study was to evaluate data sets on the occurrence of Cryptosporidium oocysts in raw water and on the removal of model organisms (anaerobic spores, bacteriophages) to perform such a risk assessment. A tiered approach was used by first calculating approximate point estimates and when the point estimate was close to the required safety level (10-4 annual risk of infection), fitting the data to probability distributions and Monte Carlo analysis to calculate the distribution of the risk of infection. Sensitivity analysis showed that the variability in the Cryptosporidium data in raw water (largely introduced by the variability of the recovery efficiency of the detection method) determined most of the variance in the risk estimate.
Removal of the organic surface layer in combined sewer sediment using a flushing gate
Authors: Laplace D. , Oms C. , Ahyerre M. , Chebbo G. , Lemasson J. , Felouzis L.
Published: May 2018

Recent research identified the different sources of pollution of wet weather Combined Sewers Overflows (CSOs): it appeared that the deposits in sewers, and especially an organic layer situated at the water-sediment interface, may contribute 40-70% to the total pollution load of CSOs. Using the cyclic flush Hydrass gate, we generated increased water flows during dry weather. The effects of flushing the deposits have been analysed: the eroded particles sampled during the first flush wave show pollutant characteristics similar to characteristics measured in the organic layer. The organic layer that has formed on the surface of deposits can thus be washed off before rainstorms occur using the cyclic flushing technique.
Biofilm in combined sewers: wet weather pollution source and/or dry weather pollution indicator?
Authors: Rocher V. , Azimi S. , Moilleron R. , Chebbo G.
Published: May 2018

In a sewer trunk, three kinds of deposit, acting as potential wet weather sources, can be found: the biofilm, the organic layer and the gross bed sediment. This research program, on the “Le Marais” catchment (Paris, France), focused on the biofilm. The objectives were to describe, using a Transmission Electronic Microscope, the architecture of the sewer biofilm and to investigate the contents and the distributions of aliphatic and aromatic hydrocarbons in biofilm. The electron micrographs illustrated a uniform film of bacteria totally covering the surface of a thick organic matrix. A large cohesion of the cell layer and organic matrix complex, due to exopolysaccharides, was noticed. Hence, the hydrocarbon contents were measured not only in the biofilm itself, but in this complex. Our results showed that almost all hydrocarbons were stored in the gross bed sediment and the organic layer and, consequently, the biofilm was not an important potential source of wet weather pollution. Comparison between the hydrocarbon distributions in the biofilm and in the other deposits indicated that the biofilm could be used as an indicator of the aliphatic hydrocarbon pollution in the organic layer.
Evaluation of the current status of operating and closed landfills in Russia, Finland and Ireland with regard to water pollution and methane emission
Authors: Kalyuzhnyi S. , Epov A. , Sormunen K. , Kettunen R. , Rintala J. , Privalenko V. , Nozhevnikova A. , Pender S. , Colleran E.
Published: May 2018

The annual production of municipal solid wastes (MSW) in Russia, Finland and Ireland in the late 1990s accounts for 37.5, 2.5 and 2.05 mln. tonnes or 252, 488 and 566 kg per capita, respectively. 96.5, 64 and 91% of these wastes (for Russia, Finland and Ireland, correspondingly) are currently disposed of via landfilling. However, nowadays, MSW management in these countries is undergoing drastic changes (source separation, closure of old landfills, reduction of the number of landfills etc.) forced by recent legislation set by the European Union and Russian authorities. This paper evaluates the current status of MSW landfills, as well as information on current leachate and methane emissions in the three above mentioned countries. Landfill leachates are highly variable in each country and between different countries due to different rainfall and climatic conditions and also due to poor landfill top insulation/cover. Leachates in poorly structured landfills are very dilute, whereas leachates with total COD and nitrogen contents as high as 33,700 mg COD/l and 4,030 mg N/l, respectively, have been detected from state-of-the-art sites. Currently, on-site treatment of leachates exists at only a few landfills in Russia, Finland and Ireland but this situation will be considerably improved during the next years. The annual methane emissions from landfills are estimated as 500-900 and 77 ktonnes for Russia and Finland, respectively. Recent estimates from Ireland suggest an annual landfill methane emission of c. 2.1 Mt CO2 equivalent. Several systems of methane recovery have been developed in all three countries and these are currently in different stages of implementation.
The analysis of methods for measurement of methane oxidation in landfills
Authors: Nozhevnikova A. , Glagolev M. , Nekrasova V. , Einola J. , Sormunen K. , Rintala J.
Published: May 2018

Landfills and dumps are important sources of atmospheric methane. There is no generally accepted estimate of the influence of methane oxidation on landfill methane emissions. The present work aimed to analyse different methods for the investigation of methane emission and oxidation in methane-producing environments (wetlands, landfills, sludge checks), and to develop the precise procedure for the landfills. The combination of geochemical and microbiological methods to estimate and monitor the oxidation and emission of methane in landfills during different seasons is proposed. It includes the measurements, both on the surface and at different depths (up to 1 m) of landfill ground of the following parameters: (1) concentrations of methane, carbon dioxide and oxygen; (2) quantity of 13C isotope in gas samples; (3) methane-oxidation activity of landfill grounds assayed with two different methods: (a) in conditions of no moisture or substrate limitations, and (b) in conditions with a minimal deviation to in situ conditions; (4) the density of methanotrophic microbial population.
Bayesian approach for the calibration of models: application to an urban stormwater pollution model
Authors: Kanso A. , Gromaire M.-C. , Gaume E. , Tassin B. , Chebbo G.
Published: May 2018

In environmental modelling, estimating the confidence level in conceptual model parameters is necessary but difficult. Having a realistic estimation of the uncertainties related to the parameters is necessary i) to assess the possible origin of the calibration difficulties (correlation between model parameters for instance), and ii) to evaluate the prediction confidence limits of the calibrated model. In this paper, an application of the Metropolis algorithm, a general Monte Carlo Markov chain sampling method, for the calibration of a four-parameter lumped urban stormwater quality model is presented. Unlike traditional optimisation approaches, the Metropolis algorithm identifies not only a “best parameter set”, but a probability distribution of parameters according to measured data. The studied model includes classical formulations for the pollutant accumulation during dry weather period and their washoff during a rainfall event. Results indicate mathematical shortcomings in the pollutant accumulation formulation used.
Flow velocities and shear stresses during flushing operations in sewer collectors
Authors: Campisano A. , Modica C.
Published: May 2018

Many relevant problems of drainage systems such as first flush pollution, flow capacity reduction and consequent risks of surcharges are worsened by sediment accumulation in sewer collectors. For the solution of these problems several sediment cleansing methods and techniques, e.g. mechanical methods, traps and flushing devices, have been developed and applied in the last decades. In particular, simulation studies and experimental campaigns have shown the effectiveness of flushing methods as preventive cleansing strategy in sewer collectors.

In this paper the results of a numerical investigation for determining flushing waves characteristics both in terms of duration and flow rate are presented. The collector section lengths where flow velocities and average shear stresses determined by flushing waves exceed minimum threshold values are evaluated using a dimensionless approach. The results, related to the operative ranges of the practical applications, are exposed by means of graphs and regressive equations.
Co-digestion of primary sewage sludge and industrial wastewater under anaerobic sulphate reducing conditions: enzymatic profiles in a recycling sludge bed reactor
Authors: Whiteley C.G. , Enongene G. , Pletschke B.I. , Rose P. , Whittington-Jones K.
Published: May 2018

The first stage in the degradation and recycling of primary sewage sludge and particulate organic matter is the solubilisation and enhanced hydrolysis of complex polymeric organic carbon structures associated with the anaerobic sulphidogenic environment. Solubilization of complex carbon substrates provides the primary reaction in the BioSURE Process, and is effected in the recycling sludge bed reactor (RSBR). During the process of anaerobic digestion, macromolecules are broken down into simpler low molecular weight compounds in the presence of extracellular enzymes. Though hydrolysis of the complex carbon sources was enhanced under biosulphidogenic conditions, no studies have examined the role of enzymes and the enzymatic profiles in the RSBR. To investigate the overall enzymology in the RSBR variations in COD, pH, sulphate, sulphite and sulphide concentrations, carbohydrates, protein and activities of glucosidases, proteases and lipases were studied over 50 days in the reactor at three different depths: 0-16 cm; 16-32 cm; 32-50 cm. While the pH profile remained fairly constant between 6.9 and 7.3 the sulphate and sulphide levels, as expected, changed dramatically as sulphate reduction took place. Proteases, lipases and glucosidases all showed enhanced activity with depth in the bioreactor. It is suggested that the increased sulphide concentration generated during the sulphate reduction process stimulates the enzymes, leading to enhanced solubilisation of primary sewage sludge.
The utilisation of engineered invert traps in the management of near bed solids in sewer networks
Authors: Ashley R.M. , Tait S.J. , Stovin V.R. , Burrows R. , Fraser A. , Buxton A.P. , Blackwood D.J. , Saul A.J. , Blanksby J.R.
Published: May 2018

Large existing sewers are considerable assets which wastewater utilities will require to operate for the foreseeable future to maintain health and the quality of life in cities. Despite their existence for more than a century there is surprisingly little guidance available to manage these systems to minimise problems associated with in-sewer solids. A joint study has been undertaken in the UK, to refine and utilise new knowledge gained from field data, laboratory results and Computational Fluid Dynamics (CFD) simulations to devise cost beneficial engineering tools for the application of small invert traps to localise the deposition of sediments in sewers at accessible points for collection. New guidance has been produced for trap siting and this has been linked to a risk-cost-effectiveness assessment procedure to enable system operators to approach in-sewer sediment management pro-actively rather than reactively as currently happens.
Impacts of separate rejection water treatment on the overall plant performance
Authors: Wett B. , Alex J.
Published: May 2018

A separate rejection water treatment appears as a high-tech unit process which might be recommendable only for specific cases of an upgrading of an existing wastewater treatment plant. It is not the issue of this paper to consider a specific separate treatment process itself but to investigate the influence of such a process on the overall plant performance. A plant-wide model has been applied as an innovative tool to evaluate effects of the implemented sidestream strategy on the mainstream treatment. The model has been developed in the SIMBA environment and combines acknowledged mathematical descriptions of the activated sludge process (ASM1) and the anaerobic mesophilic digestion (Siegrist model). The model's calibration and validation was based on data from 5 years of operating experience of a full-scale rejection water treatment. The impact on the total N-elimination efficiency is demonstrated by detailed nitrogen mass flow schemes including the interactions between the wastewater and the sludge lane. Additionally limiting conditions due to dynamic N-return loads are displayed by the model's state variables.
A distributed model of solid waste anaerobic digestion: sensitivity analysis
Authors: Vavilin V.A. , Rytov S.V. , Pavlostathis S.G. , Jokela J. , Rintala J.
Published: May 2018

A distributed model of anaerobic digestion of solid waste was developed to describe the balance between the rates of polymer hydrolysis and methanogenesis during the anaerobic conversion of rich and lean wastes in batch and continuous-flow reactors. Waste, volatile fatty acids (VFAs), methanogenic biomass and sodium concentrations are the model variables. Diffusion and advection of VFAs inhibiting both polymer hydrolysis and methanogenesis were considered. A sensitivity analysis by changing the key model parameter values was carried out. The model simulations showed that the effective distance between the areas of hydrolysis/acidogenesis and methanogenesis is very important. An initial spatial separation of rich waste and inoculum enhances the methane production and waste degradation at high waste loading if relatively low VFA diffusion into the methanogenic area is taking place. When both hydrolysis and methanogenesis are strongly inhibited by high levels of VFA, fluctuations in biomass concentration are thought to be responsible for initiating the expansion of methanogenic area over the reactor space.
Concentration of pig slurry by evaporation: anaerobic digestion as the key process
Authors: Bonmatí A. , Campos E. , Flotats X.
Published: May 2018

Nutrient redistribution between areas with a structural pig slurry surplus and those with a shortage, is limited by the high cost of transportation and spreading, due to the high water content in slurry (more than 90%) and its relative low nutrient concentration. Water can be removed from slurry by evaporation, through the application of waste heat from a power plant or from other processes. Apart from obtaining a concentrate with an obviously higher nutrient concentration than the original slurry, another objective is to obtain clean water as condensate. The objective of this work was to study the batch vacuum evaporation of pig slurry liquid fraction, to evaluate the economic feasibility and to evaluate condensate quality as a function of both pH (4, 5 and 6) and pig slurry type (fresh slurry and anaerobically digested slurry). Results showed that condensate characteristics (ammonia nitrogen, VFA, COD) were strongly dependent on these variables. Previous anaerobic digestion presented clear advantages: it provided a fraction of the required energy and it removed organic matter, preventing its volatilisation in the evaporation process and providing higher quality condensates. These advantages make the combined treatment strategy economically more feasible than the evaporation process alone.