bluuebunny/crossref_metadata_2025 huggingface dataset:
How farmers in Switzerland perceive fertilizers from recycled anthropogenic nutrients (urine)
Authors: Lienert J. , Haller M. , Berner A. , Stauffacher M. , Larsen T.A.
Published: May 2018

We studied acceptance of a urine-based fertilizer product using a mail survey of 467 Swiss farmers. We distinguished among four production types: organic or IP farming, and with or without vegetable production. Considering that the idea of urine-based fertilizers is new, acceptance among the answering farmers was surprisingly high, with 57% explicitly stating that they thought it was a good or very good idea, and 42% willing to purchase such a product. The farmers of different production types did not differ strongly in their attitude towards urine-based fertilizers. Especially IP and vegetable farmers, who purchased additional fertilizers anyway, seem willing to accept urine-based fertilizers, hereby preferring a grainy, odorless ammonium nitrate fertilizer. Absolutely essential is a hazard-free product: 30% of all farmers had concerns regarding micropollutants. Based on fertilizer data, we demonstrate an existing demand for the nutrients N, P, and K in Switzerland, which could be partially substituted by a recycled urine product. Finally, we discuss methodological requirements of social science surveys. To obtain representative data on an entire population in a mail survey, multiple contacts with respondents are necessary. We argue that information and participation of stakeholders at an early stage is essential for successful technology transfer.
Hydrogen production from wastewater by acidogenic granular sludge
Authors: Liu H. , Fang H.H.P.
Published: May 2018

Sludge was granulated in a hydrogen-producing acidogenic reactor when operated at 26°C, pH 5.5 treating a sucrose-rich wastewater. The influence of hydraulic retention time (HRT) and sucrose concentration on hydrogen production by the acidogenic granular sludge was investigated at a constant loading rate of 25 g-sucrose/(láday). Results show that the gas composition was not greatly influenced by HRT or sucrose concentration. The hydrogen accounted for 57% to 68% of the biogas at HRT ranging 4.6-28.6 h and sucrose concentration ranging 4,800-29,800 mg/l. However, the hydrogen yield was more dependent on HRT and sucrose concentration. It ranged from 0.19 to 0.27 l/g-sucrose with the maximum yield occurring at HRT 13.7 h and sucrose concentration 14,300 mg/l in the wastewater. The acidified effluent was composed of volatile fatty acids and alcohols. The predominant products were butyrate (59-68%) and acetate (10-25%), plus smaller amounts of i-butyrate, valerate, i-valerate, caproate, methanol, ethanol, propanol, and butanol. The sludge yield averaged 0.2 g-VSS/g-sucrose. The carbon balance was 98-107% throughout the study.
Development of a high-efficiency phosphorus recovery method using a fluidized-bed crystallized phosphorus removal system
Authors: Shimamura K. , Tanaka T. , Miura Y. , Ishikawa H.
Published: May 2018

The authors have been engaged in the research and development concerning the recovery of MAP (Magnesium Ammonium Phosphate) using a fluidized-bed crystallized phosphorus removal system. In the reactor of the fluidized-bed crystallized phosphorus removal system, seed crystals (of MAP) are fluidized previously and new MAP crystals are produced on the seed crystal surfaces. Conventionally, the reactor consisted of one reaction tank only, but this practice had the problem that as the crystallization progresses, the seed crystal is grown excessively and as a result, the effective reaction surface areas are decreased and the fluidization effect is degraded, causing the recovery ratio to be decreased. Recently, the authors have devised a two-tank type reactor by adding a sub reaction tank to the reactor (now the main reaction tank) so that the MAP particle size in the main reaction tank may be kept constant making the recovery ratio stable. They conducted a demonstration test with a pilot experimental system of the 2-tank type reactor. For raw water T-P 111 to 507 mg/L, the main reaction tank treated water T-P 14.0 to 79.5 mg/L and phosphorus recovery ratios 84 to 92% were obtained. Because the mean MAP particle size in the main reaction tank could be kept constant, the phosphorus recovery ratio could always be above 80%, realizing stable treatment.
Extraction of Cu and Pb from printed circuit board sludge using ammonia solutions
Authors: Liu J.C. , Kao T.-H.
Published: May 2018

Sludge from a printed circuit board factory containing high concentrations of Cu and Pb was characterized. Aqueous ammonia solutions were used to extract metals from the sludge. The extraction reactions were completed within 6 hrs. The best extraction efficiency was found at pH of 10.0. Higher solid-liquid ratio and higher ammonia concentration resulted in better extraction efficiency. Fractionation experiments showed that Cu and Pb were mainly extracted from the Fe-Mn oxide-bound and carbonate-bound fractions. Extracted sludge could meet the TCLP regulation limit and be categorized as a non-hazardous waste. Results show that ammonia extraction is of potential in resource recovery and in detoxification of hazardous waste.
Tertiary nitrification in a new dual-medium aerated filter
Authors: Ishikawa S. , Suzuki T. , Nikata T. , Kakii K. , Shirakashi T.
Published: May 2018

In an effort to develop an aerated filter with high nitrification capabilities, we formulated a new filter with 2 layers: the upper layer is filled with a plastic medium, and the lower with anthracite. We tested the filter in a pilot-scale apparatus on secondary-treated sewage, and in a small-scale apparatus on secondary-treated sewage and on artificial sewage. We evaluated the nitrification characteristics under various conditions of water velocity, air velocity, temperature, and pH. We designed a tertiary plant to treat 20,000 m3/day of secondary-treated sewage, using the new filter or a conventional filter. From these comparisons, it appeared that the dual-medium aerated filter had high nitrification capabilities and was an effective device for tertiary sewage treatment.
Nitrate removal by simultaneous sulfur utilizing autotrophic and heterotrophic denitrification under different organics and alkalinity conditions: batch experiments
Authors: Oh S.E. , Bum M.S. , Yoo Y.B. , Zubair A. , Kim I.S.
Published: May 2018

The effect of various organic compounds were tested using lab-scale batch reactors. At sufficient alkalinity, the initial nitrate nitrogen concentration of 100 mg/L was completely reduced in all batch reactors. Sulfate production decreased by the addition of organics. The concentration range of organics used in this experiment did not inhibit autotrophic denitrification except for propionate. Propionate inhibited autotrophic denitrification a little, indicated by a lower sulfate production rate. Biomass in suspension increased with higher initial organic concentrations, showing higher DOC consumption. As the concentration of organics increased, alkalinity increased accordingly. Under the conditions of low alkalinity, in the case of a control reactor without organics, only about 30% of the initial nitrate was reduced. With half the theoretically required dosage of methanol, the denitrification rates increased slightly. When ethanol, acetate, and propionate were used, denitrification went to completion. When excess organics was added, however, sulfate production was significantly decreased. Interestingly, even when small amounts of organics were added, autotrophic denitrification was promoted as indicated by the sulfate production.
A comparative study of anaerobic digestion of food waste in a single pass, a leachate recycle and coupled solid/liquid reactors
Authors: Xu H.L. , Wang J.Y. , Zhang H. , Tay J.H.
Published: May 2018

A single pass reactor (R1), a leachate recycle reactor (R2) and a coupled solid/liquid bioreactor (R3-Rm) for anaerobic digestion of food waste were comparatively investigated in terms of digestion process and treatment efficiency. The coupled solid/liquid bioreactor is an enhanced two-phase system and distinctive from a traditional two-phase process with an upflow anaerobic sludge blanket (UASB) reactor as the methanogenic phase and a circulation of treated leachate between the acidification and methanogenic phases. In comparison with R1 and R2, R3-Rm enhanced the digestion process and increased the methane content of biogas. 100% of the R3-Rm methane yield was from the methanogenic phase with average methane content of 71%. The significant enhancement was also confirmed by the removal of 79% of total organic carbon (TOC), 60% of volatile solids (VS) and 80% of total COD in 12 days running of R3-Rm. However, no active methane fermentation was detected in R1 and R2 during 60 days operation. The results in this laboratory-scale study show that the rapid accumulation of volatile fatty acids (VFAs) due to the rapid acidification of food waste inhibits the development of effective methane fermentation in single pass and leachate recycle reactors. The coupled solid/liquid bioreactor is more efficient in converting food waste into methane and carbon dioxide.
The effect of light:dark cycles of medium frequency on photosynthesis by Chlorella vulgaris and the implications for waste stabilisation pond design and performance
Authors: Ratchford I.A.J. , Fallowfield H.J.
Published: May 2018

The effect of light/dark (L:D) cycle times on the recovery from photoinhibition of green micro-alga Chlorella vulgaris (CCAP211/11c) and the cyanobacterium Synechococcus (CCAP1479/5) was investigated using an irradiated, temperature controlled oxygen electrode. The onset of photoinhibition in both organisms occurred at irradiances > 300 mmol m-2s-1 at temperatures >15°C. Light/dark cycle times were controlled independently using a relay timer and shutter placed between the quartz iodide light source and the oxygen electrode chamber. Oxygen evolution decreased rapidly when cells were continuously irradiated at 300, 500 and 750 mmol m-2s-1. However, Chlorella cells irradiated at 300, 500 and 750 mmol m-2s-1 on a L:D cycle of 60s:20s, 30s:60s and 60s:120s respectively, maintained a constant rate of oxygen evolution over a 24 h incubation period. Exposure time to a given incident irradiance rather than the total light dose received appeared to determine the effect of light/dark cycle times on photosynthesis. A relationship was established between L:D ratio required to maintain constant oxygen production and incident photon flux density. The results suggest that the adverse effects of high irradiances on algae near the surface of a stratified waste stabilisation pond might be ameliorated by controlled mixing of algal cells through the depth of the pond.
New chalcogenide glass chemical sensors for S2- and dissolved H2S monitoring
Authors: Miloshova M. , Baltes D. , Bychkov E.
Published: May 2018

A non-optimised treatment of wastewaters containing organic and biological substances is very often accompanied by an accidental emanation of hydrogen sulphide H2S and therefore leads (i) to an undesirable odour in the vicinity of water treatment plants, and (ii) to a potential hazard for the neighbouring population. Fast, sensitive and reliable monitoring devices are hence of significant importance. Chalcogenide and chalcohalide glasses are new promising membrane materials for detection of heavy metal ions and toxic anions and particularly well adapted for continuous in situ monitoring and industrial process control. In the present paper, we will discuss analytical characteristics of new chalcogenide glass chemical sensors for detection of S2− and dissolved H2S, which allow reliable process control to be carried out at natural pH of wastewaters.
Rapid automated detection of nitrification kinetics using respirometry
Authors: Langergraber G. , Wuchty M. , Fleischmann N. , Lechner M.
Published: May 2018

There is no doubt that respirometry is a useful measurement principle in the field of wastewater treatment. Although a large variety of methods and case studies have been published, respirometry has become neither a standard tool for control nor for assessment and optimisation of treatment plants. The drawback of the conventional method for determining nitrification kinetics is the long experimental time. This disadvantage can be avoided by “turning over” the experiment. Starting with low ammonia concentrations the steep slope of the Monod curve is measured first. The low concentration branch of the Monod curve is also the part where e.g. inhibition can be detected. Therefore the proposed procedure allows us to speed up the measurement of nitrification kinetics and to measure nitrification inhibition on-line.
Application of CFD modelling to study the hydrodynamics of various anaerobic pond configurations
Authors: Vega G.P. , Peña M.R. , Ramírez C. , Mara D.D.
Published: May 2018

The simulation of hydrodynamics and transport phenomena in waste stabilization ponds is a developing tool worth studying in order to understand their internal processes and interactions. Pond design involves several physical, hydrological, geometric and dynamic variables so as to provide high hydrodynamic efficiency and maximum substrate utilization rates. CFD modelling allows the combination of these factors to predict the behaviour of ponds having different configurations. The two-dimensional depth-integrated model MIKE 21 was used in this study to simulate hydrodynamic and advection-dispersion processes in a full-scale anaerobic pond (AP) located in southwest Colombia. A set of 12 configurations including sludge contents, inlet-outlet positioning, baffling and pond geometry were modelled. Results showed that a crosswise (diagonally opposite) inlet-outlet layout, a length-to-breadth ratio of 2:1, plus provision of two cross baffles at 1/3 L and 2/3 L were the most effective measures to improve overall AP hydrodynamics and dispersion patterns.
Influence of the dispersion number on the estimation of coliform removal in ponds
Authors: von Sperling M.
Published: May 2018

The paper uses the technique of Monte Carlo simulation in order to investigate the sensitivity to the Dispersion Number (d) of the effluent coliform concentration from facultative and maturation ponds. The Dispersion Number is one of the coefficients used in the dispersed-flow model for ponds. Initially, four empirical equations available in the literature for the estimation of d were compared, using the results from 1,000 runs of the Monte Carlo simulation. A second different set of Monte Carlo simulations (1,000 runs) was undertaken, allowing a sensitivity analysis of d, in conjunction with other coefficients and input data used in the design of facultative and maturation ponds (e.g., population, wastewater flow, coliform removal coefficient and others). The results of the simulations suggest that, when considering the high level of uncertainty in all input variables used in the design of the ponds for coliform removal, the Dispersion Number d does not present a greater influence in the model prediction, compared with the other input variables. Based on these considerations, it is likely that, for design purposes, simple models for the prediction of d can be used, without significantly affecting the estimation of the effluent coliform concentration, considering the existing uncertainty in all other input variables.
The spatial significance of water quality indicators in waste stabilization ponds - limitations of residence time distribution analysis in predicting treatment efficiency
Authors: Sweeney D.G. , Cromar N.J. , Nixon J.B. , Ta C.T. , Fallowfield H.J.
Published: May 2018

Over the past fifty years, considerable research in waste stabilization pond operation has led to the development of a number of models used to describe the hydraulic regime and predict treatment efficiency. Models range in complexity from plug or completely mixed simplifications to computational fluid dynamics (CFD) models which are able to predict flow hydraulics at a local level. Information about the exit age of pond effluent can be used to estimate pollutant decay. However, a mechanistic approach to understanding pond operation highlights the importance of knowing both the time and spatial history of pond effluent. A CFD model of a large pond system was constructed to demonstrate various hydraulic scenarios under different boundary conditions. Two scenarios were compared to visually demonstrate the effects of differing hydraulic conditions. Typical mechanistic models were applied to each condition to quantify biological differences. This simple example indicates that integrating biological and localised flow models will lead to a more holistic understanding of pond operation and treatment efficiency.
Optimization of the treatment of piggery wastes in water hyacinth ponds
Authors: Costa R.H.R. , Zanotelli C.T. , Hoffmann D.M. , Belli Filho P. , Perdomo C.C. , Rafikov M.
Published: May 2018

This work investigates the optimal management of water hyacinth ponds for the improvement of piggery waste treatment. The optimal harvesting strategy for the water hyacinth was studied using a single mathematical model. The water hyacinth optimal harvesting problem was formulated as an optimal control problem that was solved by application of Pontryagin's Maximum Principle. The optimization of the water hyacinth control in the pond indicates that the plant density should be reduced whenever it reaches half of the maximum capacity for growth. Two experimental systems were used to validate the mathematical model, one in real scale and the other in pilot scale. The results demonstrated the feasibility of the proposed harvesting strategy. For example, a comparison of the total nitrogen removal in the different pilot ponds confirmed the modeling results, in that the performance of the pond maintained with 50% water hyacinth cover was better than the others.
Renewable energy for the aeration of wastewater ponds
Authors: Hobus I. , Hegemann W.
Published: May 2018

The application of a decentralised renewable energy supply for the aeration of wastewater ponds, and the influence of an unsteady oxygen supply on the specific conversion rate and biocoenose was investigated. With the discontinuous aeration the specific conversion rate is increased as compared to facultative ponds. The estimation of the microorganisms consortia was done with in situ hybridisation techniques. A significant shift in the bacteria population with the chosen specific probes for anaerobic, sulphate reducing and nitrifying bacteria could not be detected. Wastewater ponds have sufficient buffer volume to compensate for the fluctuating energy supply. But the efficiency of the energy supply of a photo-voltaic plant decreases in shallow lakes (d < 1.5 m) corresponding to a high oxygen production of algae. For the layout of the individual components: photo-voltaic and wind power plant, energy management, aeration system and wastewater pond, a simulation model was developed and tested. The application of renewable energy for the aeration of wastewater ponds is a useful alternative for the redevelopment of overloaded ponds as well as the construction of new wastewater ponds, especially in areas with an inadequate central electricity grid and a high availability of wind and solar energy.
Concepts for river water quality processes for an integrated river basin modelling
Authors: van Griensven A. , Bauwens W.
Published: May 2018

Although there are various ways to model the bio-chemical processes in rivers, two main trends can be distinguished: the traditional QUAL2E-type models and the RWQM-type models, developed by extending and adapting the ASM equations. Both approaches have their weak and strong points. This paper focuses on the application of these concepts in an integrated modelling context. To this purpose, the models were adapted to respect the mass balances, to enable linkage to WWTP outputs and to diffuse pollution sources. Both approaches have been included in ESWAT - Extended Soil and Water Assessment Tool - which was developed by the authors to allow for an integral modelling of the water quantity and quality processes in river basins. A comparison and evaluation of both quality models is performed for the river Dender (Belgium). It is shown that both models give a reasonable fit for dissolved oxygen and ammonia. However, the dynamics of the quality processes for the RWQM model are slower, due to the time that bacteria need to adapt to changes of the loads of organic matter.
Competitive transport of cadmium and lead through a natural porous medium: influence of the solid/liquid interface processes
Authors: Bianchi A. , Petrangeli Papini M. , Corsi A. , Behra P. , Beccari M.
Published: May 2018

Contaminated groundwater typically contains different metal contaminants which may compete with each other for the same adsorption sites. Understanding the fate of these micro-pollutants is of primary importance for the assessment of the risk associated with their dispersion in the environment and for the evaluation of the most appropriate remediation technology. In this regard, column techniques can be considered as useful tools both to perform transport experiments and to obtain equilibrium adsorption data without any perturbation of the actual solid/liquid interface. Cd and Pb monocomponent step column experiments were used to obtain adsorption isotherms on a natural aquifer material. A General Composite approach was used to define the equilibrium adsorption model characterized by two types of sites (ion-exchange and surface complexation sites). Coupling the adsorption model with the Advection-Dispersion equation (by IMPACT code) allowed us to well represent the monocomponent step experiments. The model was successfully used to predict the competitive Cd and Pb transport behaviour. Cd peaks of concentration due to Pb competition were experimentally observed and simulated by the model. This behaviour can be described only by an accurate modelling of the interaction and cannot be predicted by simple isotherms (such as Langmuir or Freundlich type).
Separation characteristics in dissolved air flotation - pilot and full-scale demonstration
Authors: Ljunggren M. , Jönsson L.
Published: May 2018

This study presents practical implications for particle separation in Dissolved Air Flotation (DAF). The objectives were to localise where particles are separated from the water phase and to determine what particles, in terms of size, are removed by the DAF-process. Both pilot- and full-scale plants were investigated. Particle sizes were analysed with a light-blocking particle counter and an optical borescope was used for visualisation of particle-bubble aggregates. It was found that particles are preferably separated upstream in the process, i.e. close to the contact zone. Furthermore, separation efficiency for particles increased with increasing particle size.
Comparative survival of Cryptosporidium, coxsackievirus A9 and Escherichia coli in stream, brackish and sea waters
Authors: Nasser A.M. , Zaruk N. , Tenenbaum L. , Netzan Y.
Published: May 2018

Discharge of inadequately treated wastewater into streams may result in the dissemination of pathogens and the contamination of surface water sources. Determining the die-off rate of pathogenic microorganisms in stream and sea waters may serve as the basis for evaluating the health risks posed by the presence of pathogens in seawater. This study was conducted to determine the effect of microbial load, temperature, salinity and turbidity on the die-off of oocysts of Cryptosporidium as compared to that of coxsackie A9 virus (Cox A9) and E. coli. The test microorganisms were seeded into stream, outfall or sea waters and incubated at either 30°C (summer) or 15°C (winter). At 30°C, the fastest die-off was observed for Cox A9 where <5-log was reduced regardless of the water quality. At 15°C Cox A9 persistence was similar to that of Cryptosporidium where no change was detected in the concentration of either throughout the study period. E coli die-off reached 5 orders of magnitude within 10d then its concentration remained unchanged. The die-off of E coli was faster than observed for Cox A9 at 15°C regardless of the water quality. No decrease was observed in the viability of Cryptosporidium under all tested conditions throughout the study period indicating the unsuitability of E coli to serve as an indicator for the presence of parasites and viruses in stream and marine waters. The prolonged persistence of pathogenic microorganisms in marine waters suggested that discharge of contamination into streams may present a serious environmental health risk.
Ultrasonic treatment of Cryptosporidium oocysts
Authors: Ashokkumar M. , Vu T. , Grieser F. , Weerawardena A. , Anderson N. , Pilkington N. , Dixon D.R.
Published: May 2018

The effect of 20 kHz ultrasound on the viability of Cryptosporidium oocysts was investigated. More than 90% of the dispersed Cryptosporidium oocysts could be deactivated in about 1.5 min of continuous sonication. In order to apply this technique to large quantities of contaminated water, quantitative filtration and redispersion of Cryptosporidium oocysts were investigated and found to be easily achievable. The estimated cost of sonication showed that the ultrasound treatment of Cryptosporidium oocysts contaminated water could be a very effective means of “deactivating” Cryptosporidium oocysts.
Effectiveness of guideline faecal indicator organism values in estimation of exposure risk at recreational coastal sites
Authors: Craig D.L. , Fallowfield H.J. , Cromar N.J.
Published: May 2018

Decay rates in coastal water and sediment for the bacterial pathogens Salmonella typhimurium and S. derby were compared in laboratory-based microcosms with results previously obtained for a number of faecal indicators. In general, the decay rates of Salmonella spp. were greater than either enterococci or coliphage in overlying water and sediment. Decay rates of E. coli were similar to Salmonella spp. in overlying water, although greater in sediment. Raised temperature resulted in an increased decay rate for all organisms in the overlying water (and to a lesser extent in the surface sediment layer). It was demonstrated that decay rates for both S. typhimurium and S. derby were greater in overlying water compared with sediment. This suggested that sediments may be acting as a reservoir for pathogenic microorganisms released into the coastal environment during recreational activity and should be considered when estimating environmental exposure. Using measured decay rates and available dose-response data, a quantitative microbial risk assessment (QMRA) utilising Monte Carlo simulation was undertaken to estimate the risk of infection to Salmonella spp. following exposure to recreational coastal water subject to a range of faecal contamination levels. In waters of extremely poor quality, subject to contamination by faecal coliforms (106 CFU/100 mL), the maximum probability of infection on the day of an accidental release was above 2.0 × 10−1 and remained above 1 × 10−3 for three days following the initial high concentration.
The significance of sunlight for the elimination of indicator bacteria in small-scale bathing ponds in central Europe
Authors: Mascher F. , Deller S. , Pichler-Semmelrock F.P. , Roehm S. , Marth E.
Published: May 2018

In order to determine the impact of sunlight on the reduction rate of indicator bacteria, bathing waters of different turbidity were artificially contaminated with indicator bacteria and exposed to sunlight. The reduction rates determined for the indicator bacteria showed a significant correlation with radiation intensity and, thus, also the time of day as well as the turbidity of the water. Under conditions of strong radiation intensity and low water turbidity (<5 FTU), indicator bacteria were eliminated within 1-2 h of contamination with an initial concentration of 105 CFU/mL. Moreover, differences between different indicator bacteria were found. Enterococcus faecalis proved to be significantly more resistant to sunlight than the other indicator bacteria tested (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus). The results of the present study, namely the complete elimination of indicator bacteria within a few hours, showed that sunlight, given an appropriate intensity and good water transparency, was the most important factor in the reduction of hygienically-relevant microorganisms in surface waters and, thus, also in small-scale bathing ponds.
Water quality problems associated with intermittent water supply
Authors: Tokajian S. , Hashwa F.
Published: May 2018

A controlled study was conducted in Lebanon over a period of 12 months to determine bacterial regrowth in a small network supplying the Beirut suburb of Naccache that had a population of about 3,000. The residential area, which is fed by gravity, is supplied twice a week with chlorinated water from two artesian wells of a confined aquifer. A significant correlation was detected between the turbidity and the levels of heterotrophic plate count bacteria (HPC) in the samples from the distribution network as well as from the artesian wells. However, a negative significant correlation was found between the temperature and the HPC count in the samples collected from the source. A statistically significant increase in counts, possibly due to regrowth, was repeatedly established between two sampling points lying on a straight distribution line but 1 km apart. Faecal coliforms were detected in the source water but none in the network except during a pipe breakage incident with confirmed Escherichia coli reaching 40 CFU/100 mL. However, coliforms such as Citrobacter freundii, Enterobacter agglomerans, E. cloacae and E. skazakii were repeatedly isolated from the network, mainly due to inadequate chlorination. A second controlled study was conducted to determine the effect of storage on the microbial quality of household storage tanks (500 L), which were of two main types - galvanized cast iron and black polyethylene. The mean bacterial count increased significantly after 7 d storage in both tank types. A significant difference was found in the mean HPC/mL between the winter and the summer. Highest counts were found April-June although the maximum temperature was reported later in the summer. A positive correlation was established between the HPC/mL and pH, temperature and storage time.
Anaerobic digestion of organic solid wastes: process behaviour in transient conditions
Authors: Bolzonella D. , Battistoni P. , Mata-Alvarez J. , Cecchi F.
Published: May 2018

This paper presents the study of the variations of the process parameters during transient conditions when substrates with different biodegradability were fed to a pilot-scale anaerobic digester. The two substrates used in the experiments were the mechanically selected organic fraction of municipal solid wastes and a blend of mechanically selected and separately collected organic fraction of municipal solid wastes. Two transient conditions were studied: the mesophilic-thermophilic passage and the increase of the organic loading rate in thermophilic conditions. It was shown that enhanced fractions of biodegradable substrates determined a greater perturbation of the system and needed longer time to reach a new stable condition. The volatile fatty acids concentration and their indirect measure, alkalinity determined upon pH 4, was the more useful parameter to understand the process behaviour because of its sensitivity to the process variations.
Comparison of dry and wet digestion for solid waste
Authors: Luning L. , van Zundert E.H.M. , Brinkmann A.J.F.
Published: May 2018

To reduce the amount of MSW going to landfills a number of technologies have been developed. Two main types of anaerobic digestion processes are distinguished for MSW organic waste, which are generally referred to as “wet” (10-15% DM) and “dry” (24-40% DM) anaerobic digestion processes. The input is conditioned to the appropriate DM content by adding process water as required. This article compares a full-scale dry process, Valorga in La Coruña, Spain and a wet process, Vagron in Groningen, The Netherlands. A crucial difference is that the Vagron facility applies a washing step prior to the AD process to remove inert materials for re-use and to prevent damage of the installation. In the Valorga facility the organic fraction of the mechanical separation process is fed directly to the AD process. Both processes can be considered proven technology. Specific gas production is practically identical. Waste water production is higher in the wet process, as is to be expected, but this is compensated by a smaller amount of digestate to be disposed of and the separation of inert materials suitable for recycling. The organic loading rate for the Vagron process appears to be higher and the required reactor volume smaller in comparison to the dry Valorga process. The applicability of AD processes is strongly determined by the environmental standards set for the products from digestion. The German standards for digestate result in a lower potential for recycling of inert material separated from organic MSW.
Sewer sediment transport studies using an environmentally controlled annular flume
Authors: Tait S.J. , Ashley R.M. , Verhoeven R. , Clemens F. , Aanen L.
Published: May 2018

This paper provides an overview and some preliminary results of a collaborative project recently completed at WL Delft Hydraulics. It describes tests in an annular flume, in which sediment deposits were formed under carefully controlled and monitored environmental conditions. The deposits were then subjected to a series of time steps in which the rotational speed of the flume’s top and bottom plates was increased, progressively increasing the bed shear stress. The sediment deposits were formed using three different types of sediment. An artificial organic sediment, together with a uniformly sized sand were selected as surrogate sewer sediments. The deposits in the remaining experiments were real in-sewer sediments, from catchments in the UK (Dundee) and The Netherlands (Loenen). During the erosion tests, total and volatile suspended solids concentration, particle size distribution of the eroded sediment, and COD and DO levels were recorded. The bed surface topography was also measured so that the influence of the deposit formation condition on bedforms could also be examined. Where bed consolidation times were least 24 hours a biologically active surficial layer was observed to develop at the sediment/water interface. The initial deposit conditions (temperature and deposit duration) were both found to have a significant impact on the subsequent erosion of the deposit.
Alkaline subcritical-water treatment and alkaline heat treatment for the increase in biodegradability of newsprint waste
Authors: Fox M.H. , Noike T. , Ohki T.
Published: May 2018

This work describes two alkaline semicontinuous processes for the conversion of refractory organic materials into biodegradable substances. Newsprint was used as a lignocellulosic waste. Methane conversion efficiencies and cellulose removals were investigated for the two following processes: alkaline subcritical-water treatment (ASWT) coupled with methane fermentation and alkaline heat treatment (newsprint heated with steam in an autoclave; AHT) coupled with methane fermentation with a neutral subcritical-water treatment (NSWT) recycle. Results showed that for ASWT coupled with methane fermentation higher methane conversion efficiencies and higher cellulose removals were achieved as HRT increased. At HRT = 20 days, average CH4 conversion efficiency and average cellulose removal reached 26% and 44%, respectively. After a final HRT of 40 days, average CH4 conversion efficiency and average cellulose removal reached 50% and 60%, respectively. On the other hand, for AHT coupled with methane fermentation, methane conversion efficiencies did not show a greater improvement using this pretreatment process. Average conversion reached 9% with an average cellulose removal of 20%. In order to improve the yield of the reactor, approximately one-third of the effluent was recycled using NSWT (150°C; neutral pH). Methane conversion efficiency of this process increased as more recycles were performed. For the fifth operation, the total average methane conversion efficiency was 44% with a total average cellulose removal of 55%.
Optimal process configuration for anaerobic digestion with ozonation
Authors: Goel R. , Tokutomi T. , Yasui H. , Noike T.
Published: May 2018

Economical source minimization of excess sludge production is an attractive option to deal with the problem of sludge disposal under strict disposal standards. In this paper long-term operational results for two different process configurations that combine oxidative ozone treatment with anaerobic sludge digestion are described. In the first configuration ozone pretreatment was combined with chemostat anaerobic digestion while in the second configuration ozone pre/post-treatments were combined with an anaerobic digester operated without solid removal. From the results of chemostat experiments, the ozone pretreatment solubilized around 19% and 37% of the solids at 0.015 and 0.05 gO3/gTS ozone dose respectively. The ozone pretreatment resulted in improved TVS reduction efficiencies and the degradation efficiencies were observed to depend on the applied ozone dose and system SRT. The TVS degradation efficiency for pre-ozonated sludge at an ozone dose of 0.05 gO3/gTS was 59% as compared to 31% for the control reactor fed with un-ozonated sludge. Test results with the second configuration indicated that overall TVS removal efficiencies for a process scheme with post-ozonation could be improved up to 85% with a minimum ozone dose of 0.045 gO3/gTVS-fed. However, since no solids (except that for sampling) were withdrawn in this configuration, the accumulated total solids in the reactors increased to 28 g/l to 30 g/l at pseudosteady state. The average specific methane recoveries were observed to be 0.36 l CH4/gTVS fed which were slightly lower than theoretically expected. Based on the experimental results, important points in the choice of process configuration are discussed.
Semi-continuous anaerobic digestion of food waste using a hybrid anaerobic solid-liquid bioreactor
Authors: Wang J.-Y. , Xu H.-L. , Zhang H. , Tay J.-H.
Published: May 2018

A hybrid anaerobic solid-liquid (HASL) bioreactor was developed to enhance food waste conversion. The HASL bioreactor is a modified two-phase anaerobic digestion system with a solid waste reactor and a high-rate anaerobic wastewater reactor, which was a UASB reactor. In this study, the methanogenesis in the UASB reactor was investigated under a semi-continuous operation of the food waste digestion system. The HASL process, including 7 days of start-up and 23 days of semi-continuous operation followed by 6 days of batch operation, was commenced by loading 2.8 kg of shredded food waste. During the semi-continuous operation, 0.2 kg of the same waste was loaded daily. The leachate from acidification phase, i.e., solid waste reactor, remained acidic (pH 4.9-5.5) and high in total VFA (TVFA), 9,500-11,500 mg/L, and COD (8,000-11,800 mg/L) levels. In the methanogenesis phase, i.e., UASB reactor, effective TVFA and COD removals (88 ± 5% and 85 ± 7%, respectively) were obtained, while the methane content was 71%. At the end of operation, about 78% of VS added in the HASL bioreactor was removed, while TOC and total COD reductions were 78% and 79%, respectively. The results showed that the use of UASB reactor in the semi-continuous HASL system can enhance the methanogenesis process and increase the methane content in biogas production.
Pond and wetland treatment
Authors: Kadlec R.H.
Published: May 2018

Wetlands are in use as adjuncts to wastewater treatment lagoons at many north temperate locations. Performance data for 21 systems show median removals of 67, 61, 61, 48 and 99.8% for TSS, BOD, NH4-N, TP and fecal coliforms, respectively. Hydraulic loading rates range from 0.14 to 55 cm/d, areas from 0.02 to 200 ha, and latitudes from 30 to 54°N. Calibrations of first order models with temperature dependence show that rate constants vary from seasonal dependence at low loadings to temperature dependence at high loadings for ammonia. Phosphorus rate constants display seasonal, not temperature effects. BOD and TSS are not affected by season. Wetland rate constants are larger than those for lagoons for all constituents. The optimal winter operating strategy, if hydraulics allow, is partial storage during frozen months, coupled with winter use of the wetlands. The use of FWS wetlands for polishing lagoon effluents is cost effective when land availability is not drastically constrained. Many systems have been in operation long enough to demonstrate sustainable long-term performance. Infiltration beds are potentially a valuable addition to ponds and wetlands.
A technique using a membrane flow cell to determine average mass transfer coefficients and tortuosity factors in biofilms
Authors: López L.A. García , Veiga M.C. , Nogueira R. , Aparicio A. , Melo L.F.
Published: May 2018

Average mass transfer coefficients of an inert compound (LiCl) within denitrifying biofilms were monitored during biofilm growth in a membrane flow cell under different flow conditions, until the biofilm reached (pseudo-) steady state. Average effective diffusivities were found to increase with the decrease in tortuosity factors of the biofilm matrix. The lowest tortuosity factor corresponded to the biofilm formed under the highest liquid velocity.
Phosphorus retention in subsurface constructed wetlands: investigations focused on calcareous materials and their chemical reactions
Authors: Molle P. , Liénard A. , Grasmick A. , Iwema A.
Published: May 2018

Phosphorus removal from wastewater has been of growing interest for some decades to avoid eutrophication in surface water. In subsurface constructed wetlands precipitation and adsorption are the main mechanisms responsible for P uptake. Two media (calcite and recycled crushed concrete (RCC)) were examined in batch and continuous systems. Batch experiments show attractive sorption capacities, however experiments carried out in open reactors pointed out some limitation in retention capacities and effluent quality. RCC is sensitive to a strong dissolution leading to a quick phosphorus precipitation but induces high conductivity and pH values in the treated water. Calcite efficiency depends on the carbonate equilibrium of the solution. Microscopic observations of the calcite surface show crystal growth of phosphorus precipitate. Crystallisation seems to be the main P uptake once a material's surface is covered.
Monitoring cell detachment by surfactants in a parallel plate flow chamber
Authors: Azeredo J. , Pacheco A.P. , Lopes I. , Oliveira R. , Vieira M.J.
Published: May 2018

The efficacy of the surfactants SDS and CTAB in detaching P. fluorescens from glass surface was evaluated in a parallel plate flow chamber. This device enables “in situ” determinations of cells detachment following the application of surfactants under well controlled hydrodynamic conditions. The results showed that SDS was able to remove almost all adhering bacteria in a short period of time, whereas CTAB did not promote much cell desorption. On the contrary, this surfactant increased the adhesion strength between cells and glass. Both surfactants promoted different alterations of cell surface properties, which explain their dissimilar effectiveness as cleansing agents.
Polish experience with sewage sludge dewatering in reed systems
Authors: Obarska-Pempkowiak H. , Tuszyńska A. , Sobociński Z.
Published: May 2018

Macrophyte plants e.g. reed, cattails, bulrush, can be applied to sewage sludge utilisation. One of the first facilities of this type in the Gdansk region (Northern Poland) was established in Darzlubie in 1995 and primary sludge has been utilised in reed beds there. The objective of the undertaken research was evaluating the influence of sewage sludge storage on its chemical and biological properties. A total of 5.5 m thick layer of primary, anaerobically stabilised sludge (moisture 90-96%) was loaded to the reed bed during 6 years of operation. As a consequence of dewatering and biochemical transformation, the sludge layer decreased to 30 cm. Moisture, organic matter, total nitrogen and total phosphorus contents, as well as coli index, Clostridium perfringens index and the number of Ascaris lumbricoides ova were measured. Also the contents of heavy metals (Cu, Pb, Zn, Ni, Cr and Cd) were determined in sludge samples. The study showed that sludge storage in reed beds results in dewatering and partial stabilisation. In the reed lagoons in Swarzewo and Zambrow, dewatering of secondary sludges was investigated. The results of measurements of the quality of sludge and effluent from the reed lagoon in Zambrow are also presented.
Microbial mechanisms of carbon removal in subsurface flow wetlands
Authors: Baptista J.D.C. , Donnelly T. , Rayne D. , Davenport R.J.
Published: May 2018

The microbial mechanisms of carbon removal in subsurface flow wetlands were studied, in one wetland with plants and one without plants. Particular emphasis was given to the influence of plants in the treatment process. Wetlands without plants showed higher carbon removal than those with plants, 63% and 51%, respectively (p<0.05). Molecular analysis of the bacterial diversity, growth rates and specific microbial activities showed that the two wetlands were different, especially towards the outlet of the two systems. Sulphate reducers and methanogens were found in both wetlands, and they are thought to be the main removers of soluble organic carbon in these two systems.
Nitrous oxide, dinitrogen and methane emission in a subsurface flow constructed wetland
Authors: Mander Ü , Kuusemets V. , Lõhmus K. , Mauring T. , Teiter S. , Augustin J.
Published: May 2018

N2O, N2 and CH4 fluxes were measured from a horizontal subsurface flow (HSSF) constructed wetland (CW) for wastewater treatment in Estonia. The closed chamber method was used in the field and the He-O method (intact soil core analyses) in the lab throughout the period from October 2001 to June 2002. The average flux of N2O-N, N2-N and CH4-C from various microsites ranged from 0.1 to 59, 4.1 to 1,458 and -0.04 to 2,094 mg m-2 d-1, respectively. A significantly higher flux of N2O was found in chambers installed above the inlet pipes, while the methane flux was higher in the inlet part of the bed with wetter conditions. The groundwater table significantly correlates with gas emission rates of all the gases studied; N2 emission was enhanced by higher temperature of wastewater. PO43- and NH4+ content significantly enhanced, and NO2- and NO3- content inhibited, both N2O and CH4 fluxes. NH4+ showed a negative correlation with N2 flux. Nitrification and denitrification are the main processes of the N removal in the CW covering 42.9%. The specific global warming potential was highest in the wet bed and lowest in the dry bed with lowered water table (32 and 9 g CO2 pe-1 d-1, respectively).