bluuebunny/crossref_metadata_2025 huggingface dataset:
Management of environmental uncertainty in maintenance dredging of polluted harbours in Norway
Authors: Cañellas-Boltà S. , Strand R. , Killie B.
Published: May 2018

High levels of toxic chemicals such as tributyltin (TBT) have been found in the bottom sediments of many Norwegian harbours. Norwegian environmental authorities consider maintenance dredging of such harbours to be potentially harmful to the environment due to the suspension and spread of polluted sediments during the dredging operation. Accordingly, permission to dredge may be denied, or special environmental measures may be required on a case-to-case basis. In this paper, we describe the prevailing uncertainty in the assessment of the environmental effects. Employing Jerome Ravetz' distinction between practical and technical problems in the analysis of a case study from Northern Norway, we show the disadvantages with an exclusive focus on technical solutions. Finally, we discuss informal and simple means to strengthen the presence of the practical problem in the decision process and thereby improve the management of uncertainty.
Finite element modeling to expand the UMCCA model to describe biofilm mechanical behavior
Authors: Laspidou C.S. , Rittmann B.E. , Karamanos S.A.
Published: May 2018

In order to understand the influence of biofilm's physical and microbiological structures on its mechanical behavior, a finite element model that describes the structural mechanics of a composite solid is linked to the outputs of the multi-component biofilm model UMCCA. The UMCCA model outputs densities of active biomass, inert biomass, and EPS for each compartment in a 2-D biofilm. These densities are mapped to the finite-element model to give a composite Young's modulus, which expresses the stress-strain properties of the biofilm by location. Sample results illustrate that using this methodology, one can identify the points in the biofilm that develop the highest internal stresses and that are most likely to fail first, leading to detachment.
The use of the Rotoscope as an online, real-time, non-destructive biofilm monitor
Authors: Cloete T.E. , Maluleke M.R.
Published: May 2018

Biofilms are involved in all kinds of biofouling and cause a significant economic loss of billions of dollars annually, worldwide. In order to effectively control the growth of biofilms, it is necessary to investigate the structure of biofilms grown under different conditions. Several methods are available to monitor biofilm progression, but their applications are limited by low intensity, high labour intensity, intrusive sampling, and long time lags from sampling to results. The goal of this research was to monitor biofilm growth using a biological rotating contact disc, based on the total plate count, scanning electron microscopy and the light reflection. Light reflected changed with biofilm thickness and the thicker the biofilm, the less light was reflected. Addition of NaCl anolyte caused some detachment of the microbial cells as was indicated by a slight increase in light reflection. This was supported by SEM micrographs.
Resistance of Legionella to disinfection in hot water distribution systems
Authors: Saby S. , Vidal A. , Suty H.
Published: May 2018

The efficiency of various disinfection treatments against Legionella was tested on a hot water distribution system (HWDS) pilot unit. The results demonstrated clearly that most Legionella in the networks were fixed in the biofilm at the surface of the pipe (more than 98% for each loop). Chemical treatments (continuous chlorination, hyperchlorination, hydrogen peroxide and peracetic acid mixing) commonly used for the eradication of Legionella in hot water distribution networks appeared to be inadequate for eradicating the bacteria in the biofilm. Unfortunately, the biofilm contained most of the pathogens in an HWDS whereas legislation is only restricted to the Legionella concentration in the water phase. Thermal treatment appeared to be efficient to disinfect most of the biofilm but seemed to promote the biofilm re-growth as well. It was then concluded that the best solution to prevent Legionella contamination in hot water distribution systems would be to have perfect control of the temperature in the networks (temperature > 55°C at all points). Nevertheless, in many cases it is difficult to have such control, so during the time necessary to modify networks, the best solution to control Legionella proliferation appears to be to apply a treatment shock (thermal or chlorination as a function of pipe characteristics). These treatments must be followed by a continuous chlorination that is totally controlled and equipped with alarm systems. This study demonstrates that biofilm sampling devices must be installed in hot water distribution systems to anticipate Legionella contamination and correctly determine the efficiency of the treatments.
Workshop 1 (synthesis): systems for sustainable urban water services
Authors: Speers A. , Brattberg G. , Oatridge J.
Published: May 2018

The systems approach is absolutely essential to secure sustainability in urban water services. The financing dimension is critical; fragmented institutions are a great barrier, hindering a systems approach; recycling of water and nutrients is vital for food production and livelihood improvements; effective knowledge transfer about innovative approaches to sanitation is essential to share success stories and failures.
Policy principles and implementation guidelines for private sector participation in the water sector — a step towards better results
Authors: Rothenberger D. , Frei U. , Brugger F.
Published: May 2018

To achieve the Millennium Development Goals, all partners (public, private, NGOs) must be engaged for improving and expanding the water supply and sanitation services. Yet, high transaction costs, unclear role allocation and lack of trust and commitment put Private Sector Participation (PSP) at risk. The initiative “Policy Principles and Implementation Guidelines for Private Sector Participation in Sustainable Water Supply and Sanitation” contributes to equitable, effective, ecological and efficient PSP projects. Based on a multi stakeholder process, the Policy Principles are offering an open and transparent framework for the negotiation of valid, widely accepted and action-oriented solutions, while the Implementation Guidelines focus on success factors for building partnerships on the operational level.
Workshop 5 (synthesis): cascading effective water use in catchment systems
Authors: Rijsberman F. , Harlin J.
Published: May 2018

Precipitation is the primary water resource. Equal attention should be given to the management of evapotranspiration, surface and ground water as well as water storage.
Workshop 7b (synthesis): sustainable groundwater management in rural areas
Authors: Shah T. , Cederwall K. , Egboka B.
Published: May 2018

Sustainable groundwater management strategies should be based on adequate assessment of the specific resource characteristics and human reliance on these resources. Disturbed groundwater balance reduces safe yield and degrades groundwater quality.
River basins: the environmental engines to keep us all running
Authors: Matthews P.
Published: May 2018

The importance of clean water, good sanitation and a healthy environment demands better management of planning, control and regulation with catchments increasingly being the administrative basis of regional management. It then makes eminent sense from a theoretical and practical point of view to use the basin as the administrative unit to model and administer an integrated environmental protection regime.
Concentration and detection of SARS coronavirus in sewage from Xiao Tang Shan hospital and the 309th Hospital of the Chinese People's Liberation Army
Authors: Wang X.W. , Li J. , Guo T. , Zhen B. , Kong Q. , Yi B. , Li Z. , Song N. , Jin M. , Xiao W. , zhu X. , Gu C. , Yin J. , Wei W. , Yao W. , Liu C. , Li J. , Ou G. , Wang M. , Fang T. , Wang G. , Qiu Y. , Wu H. , Chao F. , Li J.
Published: May 2018

A worldwide outbreak of severe acute respiratory syndrome (SARS) had been reported. Over 8439 SARS cases and 812 SARS-related deaths were reported to the World Health Organization from 32 countries around the world up to 5 July 2003. The mechanism of transmission of SARS-CoV has been limited only to close contacts with patients. Attention was focused on possible transmission by the sewage system because laboratory studies showed that patients excreted coronavirus RNA in their stools in Amoy Gardens in Hong Kong. To explore whether the stool of SARS patients or the sewage containing the stool of patients would transmit SARS-CoV or not, we used a style of electropositive filter media particle to concentrate the SARS-CoV from the sewage of two hospitals receiving SARS patients in Beijing, as well as cell culture, semi-nested RT–PCR and sequencing of genes to detect and identify the viruses from sewage. There was no live SARS-CoV detected in the sewage in these assays. The nucleic acid of SARS-CoV was found in the sewage before disinfection from both hospitals by PCR. After disinfection, SARS-CoV RNA could be detected from some samples from the 309th Hospital of the Chinese People's Liberation Army, but not from Xiao Tang Shan Hospital after disinfection. In this study, we found that the virus can survive for 14 days in sewage at 4°C, 2 days at 20°C, and its RNA can be detected for 8 days though the virus had been inactivated. In conclusion, this study demonstrates that the RNA of SARS-CoV could be detected from the concentrates of sewage of both hospitals receiving SARS patients before disinfection and occasionally after disinfection though there was no live SARS-CoV; thus much attention should be paid to the treatment of stools of patients and the sewage of hospitals receiving SARS patients.
Assessment of solar photocatalysis to purify on-site rinse waters from tractor cisterns used in grapevine pest control: field experimentation
Authors: Pichat P. , Vannier S. , Dussaud J. , Rubis J.-P.
Published: May 2018

The aim of this study was to assess in a vineyard the effect of purifying by solar photocatalysis the title rinse waters (currently most often rejected) in terms of efficacy and on-site practicality for the wine grower. The on-site, self-functioning, solar purifying unit included a corrugated-steel inclined plate of area S=1m2 onto which a TiO2-coated thin material had been slightly pressed, a tank, and an aquarium-type pump powered by a photovoltaic panel (appropriate for isolated locations). For a vineyard of area A=0.15km2, the rinse water (about 90L) corresponding to each of four typical vine treatments in summer was analysed (major pesticides for each treatment, TOC, Microtox test and, in one case, BOD5) by independent laboratories, before and after purification for 8 days. The S/A ratio tested was found insufficient even if the photocatalytic treatment markedly improved the quality of the rinse waters. From the relatively low final organic content reached in one case, it is calculated that a three-time higher S/A ratio might suffice, but new trials are necessary to determine whether it is valid for other typical cases. Inferred contribution of inorganic ions to the post-photocatalytic treatment toxicity points to the need for an additional detoxification. These field experiments have also demonstrated that the purifying prototype is robust, and easy to install and use on site by the wine grower.
The performance of vertical flow constructed wetland systems with special reference to the significance of oxygen transfer and hydraulic loading rates
Authors: Cooper P.
Published: May 2018

The paper reviews the development of the vertical flow (VF) reed beds/constructed wetlands over the past 20 years. The performance of VF systems (and their use within hybrid systems) is analysed by reference to a number of brief case studies. The oxygen transfer rate (OTR) achieved is absolutely critical to the sizing of the systems. The author reviews the reported OTRs and comments on the existing design equations proposed for calculation of the area of beds. The 1st generation of VF systems used a set of parallel beds that were dosed one at a time in rotation and then rested for a period of days because there was considerable concern (based on early experience) that they would become clogged. In the past 10 years a number of new designs of 2nd generation VF beds have been built which make use of a single bed and hence operate without any resting periods. The hydraulic loading rate and the selection of the bed media, which are critical to the design and hence successful operation of these 2nd generation compact VF beds, are described. It is now possible to produce a very high quality of effluent from VF beds alone sized at 2 m2/pe when treating domestic sewage.
Sludge reed bed facilities: operation and problems
Authors: Nielsen S.
Published: May 2018

Short operating periods and problems with dewatering efficiency, vegetation, mineralisation and odour are primarily caused by incorrect construction of the filter, poor capillary connections, an inadequate number of basins, insufficient basin area and overloading during commissioning and during subsequent operation. Dimensioning should be based on the sludge quality including the dewatering qualities and not solely on calculations of the sludge production. Loading after planting depends on the development level of the vegetation. The loading program should ensure that reed establishment is not impeded and should prevent the sludge residue from growing so quickly horizontally and vertically that the reeds cannot colonise the sludge residue. Overloading results in an anaerobic sludge residue with ensuing methane production. Typically, a sludge reed bed facility with a loading period of maximum 5 days, must be built with 10 basins to permit a rest phase of about 40 days. Facilities with 8 basins, where it is possible to load 1 basin for 7 days, will be able to have a 7-week rest phase before the first basin is loaded again. Facilities with for example 8–13 basins and loading period of between 4 and 10 days are able to achieve rest periods of up to 2 to 2½ months, which results in the optimal evapotranspiration and minerilization. The conditions and thus the possibilities vary depending upon the type of sludge.
Treatment of septage in constructed wetlands in tropical climate: lessons learnt from seven years of operation
Authors: Koottatep T. , Surinkul N. , Polprasert C. , Kamal A.S.M. , Koné D. , Montangero A. , Heinss U. , Strauss M.
Published: May 2018

In tropical regions, where most of the developing countries are located, septic tanks and other onsite sanitation systems are the predominant form of storage and pre-treatment of excreta and wastewater, generating septage and other types of sludges. The septage is disposed of untreated, mainly due to lack of affordable treatment options. This study presents lessons that have been learned from the operation of pilot-scale constructed wetlands (CWs) for septage treatment since 1997. The experiments have been conducted by using three CW units planted with narrow-leave cattails (Typha augustifolia) and operating in a vertical-flow mode. Based on the experimental results, it can be suggested that the optimum solids loading rate be 250 kg TS/m2 yr and 6-day percolate impoundment. At these operational conditions, the removal efficiencies of CW units treating septage at the range of 80–96% for COD, TS and TKN were achieved. The biosolid accumulated on the CW units to a depth of 80 cm has never been removed during 7 years of operation, but bed permeability remained unimpaired. The biosolid contains viable helminth eggs below critical limit of sludge quality standards for agricultural use. Subject to local conditions, the suggested operational criteria should be reassessed at the full-scale implementation.
The effect of a vertical flow filter bed on a hybrid constructed wetland system
Authors: Noorvee A. , Põldvere E. , Mander Ü.
Published: May 2018

Data from 18 sampling wells in Kodijärve horizontal subsurface flow (HSSF) constructed wetland (CW) (South Estonia) is presented and differences in purification efficiencies inside the HSSF CW are calculated. Temporarily anaerobic conditions in the Kodijärve HSSF system did not allow efficient removal of BOD7, NH4-N, Ntot and Ptot. In 2002 a vertical subsurface flow filter was constructed to enhance aeration. The design of the system was based simply on the oxygen demand of the wastewater and on the aeration potential of vertical flow wetlands. The vertical flow system has shown satisfactory results. The purification efficiency of BOD7 in the Kodijärve CW has improved significantly and there has been a slight increase in purification efficiencies of NH4-N and Ntot. On the ohther hand, the removal efficiency of Ptot has decreased significantly. Although, the mass loading rates have increased, mass removal rates of all four parameters have improved significantly. Nevertheless, optimization of the constructed wetland system is essential in order to meet effluent standards during wintertime.
Development of a high-efficiency H2 feeder for bioremediation
Authors: Nobata T. , Prosnansky M. , Sakakibara Y. , Fukuda S.
Published: May 2018

An electrochemical dissolved hydrogen feeder equipped with a multi-cathode system and a high-rate recirculation pump was developed in order to examine its feasibility for bioremediation. Results showed that the feeding efficiency was remarkably higher than that in former studies. The reason for the enhanced hydrogen dissolution rate was thought to be due to the large cathode area by applying multiple granular activated carbon electrodes resulting in low current density. Two mass balance equations were formulated and applied to analyze the performance of the apparatus theoretically. The hydrogen dissolution rate calculated from the equations was in fairly good agreement with observed results. It was suggested that the electrochemical H2 feeder would be a competitive alternative as a hydrogen feeding method for bioremediation.
Parameter investigation for decentralised dewatering and solar thermic drying of sludge
Authors: Wett B. , Demattio M. , Becker W.
Published: May 2018

The purpose of this paper is an experimental and model assisted investigation of the capabilities of a dewatering system for sewage sludge for decentralised sites. Laboratory and field tests are performed with different initial conditions and the influences of filter medium, initial height, initial total suspended solids, temperature and relative humidity are discussed. The experimental work shows the feasibility of geotextile media for dewatering high water content sewage sludge and that the textile structure is of secondary importance. The specific filter resistance of the sludge cake is found to be the most significant factor in dewatering applications.

The mathematical description of the dewatering process is based on the superposition of two models, the Conventional Filtration Theory for the filtration phase and the BT-model for the drying phase. Feasibility and limits of the theoretical approach are evaluated by means of a comparison between measurements and simulated data of cyclic reloading tests. It is found that a better filtration efficiency is achieved at higher TSS and at lower initial height of the slurry layer. Due to the viscosity decrease, a higher temperature enhances not only evaporation, but also filtration rate.
Enhancement of oxygen transfer and nitrogen removal in a membrane separation bioreactor for domestic wastewater treatment
Authors: Chiemchaisri C. , Yamamoto K.
Published: May 2018

Biological nitrogen removal in a membrane separation bioreactor developed for on-site domestic wastewater treatment was investigated. The bioreactor employed hollow fiber membrane modules for solid–liquid separation so that the biomass could be completely retained within the system. Intermittent aeration was supplied with 90 minutes on and off cycle to achieve nitrification and denitrification reaction for nitrogen removal. High COD and nitrogen removal of more than 90% were achieved under a moderate temperature of 25 °C. As the temperature was stepwise decreased from 25 to 5 °C, COD removal in the system could be constantly maintained while nitrogen removal was deteriorated. Nevertheless, increasing aeration supply could enhance nitrification at low temperature with benefit from complete retention of nitrifying bacteria within the system by membrane separation. At low operating temperature range of 5 °C, nitrogen removal could be recovered to more than 85%. A mathematical model considering diffusion resistance of limiting substrate into the bio-particle is applied to describe nitrogen removal in a membrane separation bioreactor. The simulation suggested that limitation of the oxygen supply was the major cause of inhibition of nitrification during temperature decrease. Nevertheless, increasing aeration could promote oxygen diffusion into the bio-particle. Sufficient oxygen was supplied to the nitrifying bacteria and the nitrification could proceed. In the membrane separation bioreactor, biomass concentration under low temperature operation was allowed to increase by 2–3 times of that of moderate temperature to compensate for the loss of bacterial activities so that the temperature effect was masked.
Application of remote monitoring and automatic control system using neural network for small wastewater treatment plants in Korea
Authors: Lee H. , Lee K.M. , Park C.H. , Park Y.H.
Published: May 2018

For this study, an automatic control system has been developed by using a neural network and internet-based remote monitoring system for efficient operation of plants that have a serious variance of influent loading and have difficulties in appropriate maintenance, just like small wastewater treatment plants in Korea. In the control algorithm, ORP was used as the main sensor for control. At the point where the ORP value was judged to reach the “nitrate knee” of denitrification and phosphorus release, ORP indicated the state of lower saturation read by the neural network and then changed the operating condition from the reduction state to the oxidation state. For example, if ORP indicates the state of higher saturation at the point of “nitrogen breakpoint” or “ammonia valley” of nitrification, the neural network reads it and cuts off the oxygen supply and mixing. The dORP data have been used as one of the main input for the neural network. After the operation of lab-scale cyclic aeration process using an automatic control system, it has been found that regardless of loading variance, more than 95% of organic matters and more than 60% of nitrogen and phosphorus have been removed. Assuming that an internet-connected computer and a basic web browser are available, this study has developed a remote monitoring system that can monitor the operating status of small plants or any troubles with them.
Characteristic of the sludge from the wastewater treatment plants near Varna city and possibilities for use in agriculture
Authors: Marinova-Garvanska S.
Published: May 2018

During the last few years numerous stations were built for purification of wastewaters in the country. Such a station was opened in Varna town on the Black sea cost. At purification of wastewaters a huge amount of sludge is received. The sludge is accumulated in the WWTP premises, thus hampering its functioning and polluting the environment. The aim of this investigation was to determine the chemical characteristics of the sludge from this station, considering the different modes of treatment: the sludge compactor and the drying beds after some stay. With the sludge from Varna Purification station a pot experiment was set to determine at what levels of loading with sludge the soils differ from each other by the biomass yield and heavy metals content. During the experiment two crops were grown: rape-fodder and rye-grass harvested in two cuts to follow the effects of the sludge use and the post effect in controlled conditions. The experiment was carried out on four soil units: Calcareous Chernozem, Leached Smolnitsa, Leached Cinnamonic Forest soil and Grey Forest soil (Calcic Chernozem, Haplic Vertisol, and two Chromic Luvisols from South and North Bulgaria, respectively).
An integrated electro-chemical and natural treatment system for industrial water pollution control
Authors: Polprasert C. , Sharma K. , Koottatep T.
Published: May 2018

Experiments were conducted to test the feasibility of applying an integrated electro-chemical (EC) and natural treatment system for treatment of some industrial wastewaters. The EC process was found to be very effective in removing lead, a model heavy metal from some wastewaters. Within 20 minutes of operation time, 5 to 10 A of electric current and specific surface area of electrode of 46.51m2/m3, the lead concentrations in the wastewaters were reduced from 35–100mg/l to less than 1mg/l. Based on a kinetic model developed from the experimental data, the important parameters for the EC process were found to be electric current, specific surface area of electrode, and operation time. From scanning electron microscopic and X-ray diffractometric (XRD) analysis, the EC sludge samples were found to compose mainly of maghemite (Fe2O3), magnetite (Fe3O4), and laurionite (PbClOH), suitable for disposal to secure landfills.

Two pilot-scale constructed wetlands (CW) in series, a model natural treatment system, were employed to treat wastewaters of an industrial estate in Thailand. At organic loading rates of 57–140kg BOD/hectare-year, these constructed wetlands were able to reduce BOD from 90 to 4mg/l, while suspended solids, total nitrogen and total phosphorus were reduced from 100 to 10mg/l, 24 to 4.6mg/l and 7 to 1.5mg/l, respectively, during the summer season. These results demonstrated technical feasibility of CW in removing organic and other pollutants contained in this industrial wastewater.
CFD (computational fluid dynamics) modelling of baffles for optimizing tropical waste stabilization pond systems
Authors: Shilton A.N. , Mara D.D.
Published: May 2018

CFD modelling of the incorporation of two baffles equally spaced along the longitudinal axis of the pond and with a length equal to 70% of the pond breadth, indicated a potential improvement in the removal of E. coli in a 4-day secondary facultative pond at 25°C from 5 × 106 per 100 ml in the effluent from a 1-day anaerobic pond to 4 × 104 per 100 ml; the reduction in an un-baffled pond was an order of magnitude less effective. The addition of a similarly baffled 4-day primary maturation pond reduced the effluent E. coli count to 340 per 100 ml; the reduction in an un-baffled series was two orders of magnitude less effective. Well designed baffles thus have considerable potential for reducing pond area requirements and hence costs in the hot tropics. These very promising results highlight the need for field studies on baffled pond systems to validate (or allow calibration) of the CFD model used in this study.
Granulation in an upflow anaerobic sequencing batch reactor treating disintegrated waste activated sludge
Authors: Park K.Y. , Kim D.Y. , Chung T.H.
Published: May 2018

An upflow anaerobic reactor operated with a sequencing batch mode to enhance high rate digestion of raw and thermally disintegrated waste activated sludge with formation of granules. The gas production rate doubled when disintegrated waste activated sludge was introduced. Gradual granulation took place and the dispersed particles become coarse granulation as the operation continued. The granular sludge showed relatively higher specific methanogenic activity than the dispersed sludge. Bacterial morphology by a scanning electron microscope showed diversity of bacteria such as filamentous, rod and spherical shape in the section of granules. Filamentous bacteria, which might support the frame of a granule, were observed as long chains at the outer surface. Meanwhile, rod and spherical bacteria, which might play a role in the initial stage of granule formation, were observed from the inner surface of the granule. High rate digestion of sludge along with efficient liquid–solids separation was achieved due mainly to development of sludge granules within the upflow reactor.
Modeling ammonia removal in aerated facultative lagoons
Authors: Houweling C.D. , Kharoune L. , Escalas A. , Comeau Y.
Published: May 2018

A mechanistic model has been developed to model ammonia removal in aerated facultative lagoons. Flow is modeled through the water column by a continuously stirred tank reactor and exchanges between the sludge layer and the water column are simulated by a solids separator. The biological model is based on an activated sludge model with reactions added for anaerobic bacterial growth and degradation of inert organic material. Results show that the model is able to predict seasonal variation in ammonia removal as well as sludge accumulation in the lagoons.
Investigating helminth eggs and Salmonella sp. in stabilization ponds treating septage
Authors: Sanguinetti G.S. , Tortul C. , García M.C. , Ferrer V. , Montangero A. , Strauss M.
Published: May 2018

Sludge management arises as a relevant problem after being accumulated in primary ponds of septage treatment plants. One of the most attractive options for sludge disposal is its use in agriculture and then specific guidelines regarding hygienic quality must be fulfilled. This study aimed at evaluating the storage time needed to inactivate Ascaris eggs and Salmonella in sludge accumulated in a primary pond treating septage. Raw septage exhibited very low concentrations of viable Ascaris eggs, thus experiments with Ascaris suum eggs spiking were conducted. The concentration of Ascaris eggs in the solids accumulated at the bottom of the pond was 20 eggs/g of total solids (g TS) at the time of pond closure. Although it decreased, some eggs remained viable (0.59 mean viable eggs/g TS) up to 20 months of in-pond storage of the biosolids. Salmonella survival was studied after developing an analytical method that inhibited the native flora. Sludge was seeded with Salmonella enteritidis. An equation adequately describing Salmonella die-off in biosolids subjected to 115 days of in-pond storage/dewatering, was found to be represented by the regression: y = log MPN Salmonella/g TS = 6.67·t−0.086, with t= storage time elapsed in days. The initial concentration was 7.0 × 106 MPN/g TS and the removal efficiency was 99 %.
Potential biogas scrubbing using a high rate pond
Authors: Mandeno G. , Craggs R. , Tanner C. , Sukias J. , Webster-Brown J.
Published: May 2018

The potential to scrub biogas in a high rate pond (HRP) was evaluated using apparatus designed to maximize gas–liquid contact. Experiments compared the removal of carbon dioxide from synthetic biogas by an “in-pond angled gutter” to that by a simulated “counter-current pit.” Results showed that the counter current pit has potential for use in biogas scrubbing, with synthetic biogas carbon dioxide composition consistently reduced from 40% to <5%. The in-pond angled gutter was less effective due to bubble coalescence which reduced the total bubble surface area available for gas transfer. Measurement of oxygen levels in the scrubbed biogas showed that despite supersaturation of oxygen in the HRP water, there was little transfer to the biogas, so that explosive methane/oxygen mixtures would not be formed. Theoretical calculations indicated that the amount of biogas likely to be formed during anaerobic treatment of municipal wastewater could be scrubbed in the HRP of the same advanced pond system with little influence on HRP pH, algal growth and treatment performance. These encouraging results justify further research on this method of biogas purification.
The effect of water hyacinths for wastewater treatment under Cuban climatic conditions
Authors: Rodriguez C. , Jenssen P.D.
Published: May 2018

The purification capacity of systems using floating aquatic plants depend on the climatic conditions under which they are used. This study from Cuban conditions evaluate the effects of the organic loading rate, hydraulic loading rate and water depth on the purification capacity of water hyacinths, as well as the effect of some climatic variables on the kinetics of the treatment processes. The experimental system consisted of two consecutive tanks simulating a system of ponds in series. The water depths used were 0.5 m and 1.12 m. In the shallower system with shorter retention times and greater superficial organic loading higher removal efficiencies are obtained. With the data obtained, empirical relations were sought. From these correlations it is possible to determine the values for some parameters used in the design of aquatic treatment systems with water hyacinths. The results revealed a relationship between the purification capacity of the water hyacinth and its velocity of growth. The specific velocity of growth varied with the months of the year and was associated with the temperature and the solar radiation. A multiple correlation equation describing these relations was obtained.
Contribution of floating macrophytes (Lemna sp.) to pond modelization
Authors: Jupsin H. , Richard H. , Vasel J.L.
Published: May 2018

The objective of the present study was to develop a methodology for the quantification of the growth rate of Lemnaceae biomass by digital image analysis. The effect of biomass surface coverage on the oxygen transfer coefficient (Kla) was also quantified. Contribution of Lemnaceae to oxygen balance was evaluated by closed respirometry. Monod-like equations could be derived from growth rate coefficients in various experimental conditions. This opens the way to a deterministic model of Lemnaceae ponds where uptake of nitrogen and phosphorus (even heavy metals) can be calculated.
Performance of a combined eco-system of ponds and constructed wetlands for wastewater reclamation and reuse
Authors: Wang L. , Peng J. , Wang B. , Cao R.
Published: May 2018

An on-site study on the operational performance of a combined eco-system of ponds and SF constructed wetland for municipal wastewater treatment and reclamation/reuse in Donging City, Shandong, China was carried out from January 2001 through October 2003. The removal efficiencies for various main parameters were: TSS 84.8±7.3%, BOD5 87.2±5.3%, CODCr 70.2±18.6%, TP 52.3±23.1%, and NH3-N 54.8±23.9% with effluent concentration of TSS 9.12±5.12 mg/l, BOD5 6.44±4.58 mg/l, CODCr 42.8±6.7 mg/l, TP 0.94±0.27 mg/l and NH3-N 7.95±2.36 mg/l. In addition, the removal efficiencies for faecal coliforms and total bacteria were >99.97% and >99.998% respectively, which well meet Chinese National standards for effluent quality of municipal wastewater treatment plants. The composition of TSS was closely related to CODCr and BOD5 variations, and nitrification-denitrification is the major mechanism of nitrogen removal both in ponds and in wetlands. In addition, sedimentation also played an important role in the removal of TSS, nitrogen, phosphorus and BOD5. The removal efficiencies of various parameters, the number of species and biomass of biological community in the system increased gradually with the ecological maturation.
Roles of methanogens on volatile organic sulfur compound production in anaerobically digested wastewater biosolids
Authors: Chen Y. , Higgins M.J. , Maas N.A. , Murthy S.N. , Toffey W.E. , Foster D.J.
Published: May 2018

Land application of wastewater biosolids is both economical and beneficial to resource recycling. However, this environmentally friendly practice can be at risk due to odor complaints. Volatile organic sulfur compounds (VOSCs) including methanethiol, dimethyl sulfide, and dimethyl disulfide, have been identified as major contributors to biosolids odor. In this study, methanogens were shown to play a key role in removing VOSCs and reducing odors, and methane production was related to reduced VOSC production. Factors influencing the growth of methanogens such as the shear during dewatering and storage temperature showed a strong impact on net odor production. Examination of the microbial communities of both bacteria and archaea indicated a simplified archaeal community in biosolids, which is susceptible to environmental perturbations. Therefore, one possible odor control strategy is the preservation and enhancement of the methanogenic population during biosolids storage.
Environmental aspects of the anaerobic digestion of the organic fraction of municipal solid wastes and of solid agricultural wastes
Authors: Edelmann W. , Baier U. , Engeli H.
Published: May 2018

In order to obtain more detailed information for better decision making in future biogenic waste treatment, different processes to treat biogenic wastes in plants with a treatment capacity of 10,000 tons of organic household wastes per year as well as agricultural codigestion plants were compared by life cycle assessments (LCA). With the tool EcoIndicator, anaerobic digestion is shown to be advantageous as compared to composting, incineration or a combination of digestion and composting, mainly because of a better energy balance. The management of the liquid manure in agricultural codigestion of organic solid wastes causes increased gaseous emissions, which have negative effects on the LCA, however. It is recommended to cover the slurry pit and to use an improved manure management in order to compensate for the additional gaseous emissions. In the LCAs, the quality of the digester output could only be taken into account to a small extent; the reasons are discussed.
Co-digestion of energy crops and the source-sorted organic fraction of municipal solid waste
Authors: Nordberg Å. , Edström M.
Published: May 2018

The biological and technical performance during co-digestion of energy crops and the source-sorted organic fraction of municipal solid waste has been investigated at laboratory and pilot scale. A 50:50 (TS-based) mixture of energy crops and organic waste reached a loading rate of 6.0 gVS L−1d−1 with a methane yield of 0.33–0.38 L gVS−1, while a 80:20 mixture showed elevated levels of volatile fatty acids at 5.5 gVS L−1d−1 The better performance of the 50:50 mixture can partly be explained by a better nutritional composition. Mincing the ley crop reduced viscosity and reduced problems with fibre floating and scum-blanket formation. The electricity consumed for mincing and stirring at a full-scale plant corresponds to ca 3% of the energy produced. Calculations of the costs for full-scale plants indicate that the price of the up-graded biogas has to be at least 0.078 Euro/kWh in order to balance the costs.
A hybrid anaerobic solid–liquid system for food waste digestion
Authors: Wang J.Y. , Zhang H. , Stabnikova O. , Ang S.S. , Tay J.H.
Published: May 2018

A hybrid anaerobic solid – liquid (HASL) system was developed to enhance food waste bioconversion in comparison with the conventional two-phase anaerobic digester. The advantages of the HASL system were the higher efficiency of methane production and smaller volume of effluent from the system. The biogas, which was generated from the methanogenic phase, had an average methane content of 71–72%. Total removal of volatile solids consisted of 78–80%. The HASL system can be operated in both batch and semi-continuous modes with satisfactory performance. The addition of a submerged biofilter for ammonia removal to the HASL system further enhanced the performance of anaerobic digestion. Methane production in the enhanced HASL system was increased by 26% in comparison with the HASL system without submerged filter. This paper describes the development of the enhanced HASL system for anaerobic treatment of food waste.
Hydrolytic activity of alpha-amylase in anaerobic digested sludge
Authors: Higuchi Y. , Ohashi A. , Imachi H. , Harada H.
Published: May 2018

Hydrolysis is usually considered to be a rate-limiting step in anaerobic digestion. For improving anaerobic solid waste treatments, it is essential to elucidate the mechanism of hydrolysis. In this study, alpha-amylase, one of the hydrolytic enzymes, was investigated for the elucidation of more precise mechanism of hydrolysis. Alpha-amylase activity of solid starch-degrading bacteria (SDB) was estimated through batch experiments with several different substrates and with distinction between cell-bound and cell-free alpha-amylase. Monitoring of newly isolated strains of SDB was done by fluorescence in situ hybridization. Results indicated that cell-bound alpha-amylase is chiefly responsible for the hydrolysis in the digested sludge, providing very useful information that the contact between microbial cells and solids is significantly important. The activity of alpha-amylase of the digested sludge remained quite low when not required, but increased as they recognized appropriate substrates. Several-fold higher activity was obtained for starch or maltose as compared to glucose only.
Thermophilic treatment by anaerobic granular sludge as an effective approach to accelerate the electron transfer and improve the reductive decolorization of azo dyes in bioreactors
Authors: dos Santos A.B. , Traverse J. , Cervantes F.J. , van Lier J.B.
Published: May 2018

The effects of temperature, hydraulic retention time (HRT), and the redox mediator, anthraquinone-2,6-disulfonate (AQDS), on electron transfer and subsequent reductive decolorization of dyes from textile wastewater was assessed in mesophilic and thermophilic anaerobic bioreactors. The results clearly show that compared to mesophilic anaerobic treatment, thermophilic treatment at 55 °C is an effective approach for increasing the electron transfer capacity in bioreactors, and thus improving the decolorization rates. At an HRT of 2.5 h and in the absence of AQDS, the color removal was 5.3-fold higher at 55 °C compared to 30 °C. Furthermore, similar decolorizations were found at 55 °C between the AQDS-free and AQDS-supplemented reactors, whereas a significant difference (up to 3.6-fold) on dye reduction occurred at 30 °C.
Editorial: trends in diffuse pollution (DIPCON 2003)
Authors: Bruen Michael , Earle Ray
Published: May 2018

This introduction gives a brief summary of the 7th International IWA Conference on Diffuse Pollution. The scope of the Conference topics is addressed and the main trends identified during its course are described.
Mass balance analysis and water quality model development for loading estimates from paddy fields
Authors: Jeon J.-H. , Yoon C.G. , Ham J.-H. , Hwang H.-S.
Published: May 2018

Mass balance analysis and water quality model development for paddy field were performed using field experimental data during 2001–2002. About half (47∼62%) of the total outflow was lost by surface drainage, with the remainder (490∼530 mm) occurring by evapotranspiration. Most of nutrient inflow and outflow were mediated by fertilization and plant uptake, respectively. Nutrient outflow by surface drainage runoff was substantial about 15%∼29% for T-N and 6%∼13% for T-P. However, the responses of yield and drainage outflow to fertilization were not significant in this study. A water quality model applicable to paddy fields was developed and it demonstrates good agreement with observed data. The nutrient concentration of ponded water was high by fertilization at early culture periods, so reducing surface drainage during fertilization period can reduce nutrient loading from paddy fields. Shallow irrigation, raising the weir height in diked rice fields, and minimizing forced surface drainage are suggested to reduce surface drainage outflow.
Synthetic- and bio-polymer use for runoff water quality management in irrigated agriculture
Authors: Sojka R.E. , Entry J.A. , Orts W.J. , Morishita D.W. , Ross C.W. , Horne D.J.
Published: May 2018

Low concentrations of synthetic- or bio-polymers in irrigation water can nearly eliminate sediment, N, ortho- and total-P, DOM, pesticides, micro-organisms, and weed seed from runoff. These environmentally safe polymers are employed in various sensitive uses including food processing, animal feeds, and potable water purification. The most common synthetic polymer is anionic, high purity polyacrylamide (PAM), which typically provides 70–90% contaminant elimination. Excellent results are achieved adding only 10 ppm PAM to irrigation water, applying 1–2 kg ha−1 per irrigation, costing $4–$12 kg−1. Biopolymers are less effective. Using twice or higher concentrations, existing biopolymers are ≈60% effective as PAM, at 2–3 times the cost. A half million ha of US irrigated land use PAM for erosion control and runoff protection. The practice is spreading rapidly in the US and worldwide. Interest in development of biopolymer surrogates for PAM is high. If the supply of cheap natural gas (raw material for PAM synthesis) diminishes, industries may seek alternative polymers. Also “green” perceptions and preferences favor biopolymers for certain applications.
Nutrient balance in a paddy field with a recycling irrigation system
Authors: Feng Y.W. , Yoshinaga I. , Shiratani E. , Hitomi T. , Hasebe H.
Published: May 2018

We studied nutrient balance in a paddy field that had a recycling irrigation system and evaluated the effect of the irrigation system on nutrient balance during the irrigation period, from April to August 2002. Chemical fertilizer was the main input of phosphorus; the soil absorbed about 56% of it. The amount of nitrogen supplied by the irrigation system was higher than in a representative paddy field, and the amount of nitrogen fertilizer used was decreased because the irrigation water was partly reused. About 20% of applied nitrogen was lost by denitrification. The net outflows of phosphorus and nitrogen were −0.37 and −3.98 kg ha−1, respectively. These results indicate that our study paddy field performed well in removing phosphorus and nitrogen compounds from runoff water. A recycling irrigation system can be considered an effective way of reducing the amounts of water and fertilizer used and reducing the outflow nutrients.
A new modeling approach for estimating first flush metal mass loading
Authors: Kim L.-H. , Kayhanian M. , Lau S.-L. , Stenstrom M.K.
Published: May 2018

The purpose of this study was to investigate pollutant mass loading from major highways in Southern California, with emphasis on interpretation of event mean concentrations and first flush effects. The results of monitoring eight sites during the 1999–2002 storm seasons found that metal contaminants had higher concentrations at the early stages of storm events compared with other stages of rain storms. A new washoff model was developed to predict the event mean concentrations of metal contaminants taking first flush effect into account. Model variable parameters included average daily traffic, antecedent dry period, rain intensity, total runoff volume, and runoff coefficient. The results obtained using the washoff model were compared with measured values and found to fit well for heavy metals with R2 ranging from 0.8 to 0.95.
A novel method for evaluating bioavailability of polycyclic aromatic hydrocarbons in sediments of an urban stream
Authors: Nakajima F. , Baun A. , Ledin A. , Mikkelsen P.S.
Published: May 2018

Hydrophobic organic pollutants in urban wet weather discharges can accumulate in the sediments of receiving waters and may have adverse effects on the ecological system, especially on benthic organisms. Here, a novel method is developed for evaluating the bioavailability of such hydrophobic organic pollutants by considering the digestive guts in deposit-feeding polychaetes. We compared the amount of polycyclic aromatic hydrocarbons (PAHs) extracted by an organic solvent and by sodium dodecyl sulfate (SDS) solution (as a hypothetical digestive gut fluid of polychaetes) and interpreted the ratio of the two values as bioavailability. The sediment extracts were applied to bacterial acute toxicity tests and algal growth inhibition tests. Sediment samples were collected from an urban stream system receiving wet weather discharges. The bioavailability of the total amount of 12 PAHs in the sediments was in the range 14–38% based on the results from the GC/MS determination of the two different extracts. Lower molecular PAHs showed higher bioavailability compared to the higher molecular ones. The sediment extracts were shown to be toxic towards both algae and bacteria. The SDS extracts showed similar or higher toxicity in the two biotests compared to the organic solvent extracts in spite of their lower PAHs content.