bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developing acceptable sewage screening practices
Authors: Clay Stephen , Hodgkinson Andrew , Upton John , Green Maurice 
Published: May 2018

Severn Trent Water screens approximately 1.9 million cubic metres of sewage every day, producing 46000 m3 of screenings annually. Although the company's sludge incinerators are able to burn small quantities of screenings most of the material has to be landfilled.
Over the last few years the company has investigated the areas relating to the development of an environmentally sound disposal strategy at minimum cost. These areas have included the volume and “quality” of screenings produced, the costs of collection, treatment and disposal and the variation of screenings production rates under high flow conditions. Various items of screenings handling equipment have been assessed to identify acceptable options for permanent installations.
The required quality of screenings for economic disposal has been established and a “Quality Factor”, combining biological oxygen demand, density and dryness developed to provide a scientific basis to judge the aesthetic and commercial acceptability of a screenings product. This factor has been tested widely and found to coincide with visual assessment.
Data on the variation of screenings production with sewage flow have been collected to assist with the sizing of future installations.
The information obtained has been used to develop an application matrix for screenings handling equipment at large sewage treatment works.
Nitrogen removal upgrade of a wastewater treatment plant within existing reactor volumes: A simulation supported scenario analysis
Authors: Coen F. , Vanderhaegen B. , Boonen I. , Vanrolleghem P. A. , Van Eyck L. , Van Meenen P. 
Published: May 2018

A simulation supported scenario analysis for the upgrading of a municipal WWTP Hoogstraten (Belgium) with nitrogen removal is presented. The most cost-effective solution is to create optimal aerobic and anoxic conditions within the existing reactor volumes. The IAWQ-model No. 1 was used for the simulation of the biological reactor. A measuring campaign and some specific respirometric tests provided the necessary information for calibration and verification of the biological model.
The study consisted of two parts: 1) increase of the denitrification capacity, and 2) optimisation of operation. First, the impact of three measures, i.e. creation of anoxic zones, implementation of step feeding and introduction of internal recirculation, was evaluated by means of simulation. For this purpose a standard time variant influent was defined based on the measuring campaign. This approach made it easy to compare the different scenarios.
In the second part of the study some specific problems were handled. To avoid high nitrate concentrations during weekends three possible control actions were simulated. The simulation study also evaluated the usefulness of the primary clarifier in the upgraded design and the effect on the biological process of first flush during intensive rainfall.
The potential impact of soil carbon content on ground water nitrate contamination
Authors: Adelman D. D. , Tabidian M. A. 
Published: May 2018

A potential buildup of nitrate in the ground water resources of the eastern Sandhills of Nebraska has been projected to occur due to the intensive use of nitrogen fertilizer on irrigated cropland. A root-zone nitrate leaching study in this area revealed that soils with a high carbon concentration had minimal leaching compared to soils with lower concentrations. Soils high in carbon have an active population of denitrifying bacteria possibly causing denitrification and in turn reduction of nitrate leaching. Denitrifying bacteria are principally heterotrophic using soil organic carbon for both an energy and carbon source. The objective of this research was to interpret how root-zone denitrification affected nitrate leaching and ground water contamination by nitrate. A modified version of a solute transport model developed for the Eastern Sandhills was used to assess the risk of nitrate contamination for combinations of fertilizer and irrigation rates and for various soil carbon levels.
The first attempt was to make risk assessment with eight farm management practices for cells with increasingly greater carbon levels until only those cells with the greatest carbon level were kept in production. Results of this assessment showed that even with excessive fertilizer and irrigation rates, risk of nitrate leaching was reduced as the minimum carbon level was increased. However, since less cropland was leaching nitrate with each successive risk calculation, the impact that root-zone denitrification had in nitrate leaching reduction could not be definitively determined. This prompted a model modification of the risk calculation procedure which kept all cropland in production and computed nitrate leachate risk for increasingly higher artificial carbon levels during successive risk calculations. Changing carbon levels was still more detrimental on nitrate leaching rates than changing farm management practices.
Prediction of dissolved oxygen concentration along sanitary sewers
Authors: Matos J. Saldanha , de Sousa E. Ribeiro 
Published: May 2018

The oxygen balance in wastewater collection systems is important in respect to the degree of biological oxidation that occurs within the stream and in respect to the control of septicity and its effects. In this paper, a simple mathematical model is presented, in order to predict dissolved oxygen concentration profiles along sanitary sewers.
The mathematical model was developed based on an analytical solution of the simple differential equation of dissolved oxygen balance in sewers, and includes an empirical expression for prediction of dissolved oxygen transfer to the slime layer on the pipe walls.
Because the factors controlling dissolved oxygen balance in sewers are so complex, it would be unrealistic to expect, that with this rather simple model, dissolved oxygen concentrations can be accurately predicted. Nevertheless, it is reasonable to suppose that the predictions may be adequate for some design and operation purposes.
Genotoxicity of influents and effluents of the wastewater treatment plant
Authors: Filipic M. , Toman M. J. 
Published: May 2018

Wastewaters are treated through different processes of wastewater treatment procedures. Nevertheless they often contain mutagens especially when the proportion of industrial wastewater in comparison to municipal wastewater is high.
In this study we evaluated mutagenic potential of influents and effluents from a wastewater treatment plant that is processing both industrial and domestic wastewater. The mutagenicity of XAD-2 extracts of influent and effluent was evaluated by means of Ames test using S. typhimurium strains TA100 and TA98 in the presence and in the absence of metabolic activation. Extracts that were mutagenic to strain TA98 without metabolic activation were suspected to contain nitropolyaromatic hydrocarbons (nitro-PAHs). To confirm this hypothesis they were tested with nitroreductase (TA98NR) and O-acetiltransferase (TA98/1,8DNP6) deficient derivatives of strain TA98, that are resistant to nitropolyaromatic hydrocarbons. The nitroreductase deficient strain TA98NR was less sensitive to the mutagenic extracts of influent than the parent strain TA98. The O-acetiltransferase deficient strain TA98/1,8DNP6 was resistant to the mutagenic extracts of influent. The mutagenic extracts of the effluent were nearly equally mutagenic to the parent strain TA98 and both deficient strains TA98NR and TA98/1,8DNP6.
On the basis of the responses of nitroreductase deficient strains on the influent and effluent it was concluded that the influent contained nitro-PAHs. These were not removed or inactivated during the biological treatment of the wastewater, but activated to the final nucleophylic form able to induce mutations strain TA98 and in its nitroreductase deficient derivatives TA98NR and TA98/1,8DNP6.
Biological treatment of leachates from hazardous waste landfills using SBBR technology
Authors: Dollerer J. , Wilderer P. A. 
Published: May 2018

Bench-scale experiments with two different types of fixed bed reactor have been conducted in order to investigate the potential of SBBr technology (Sequencing Batch Biofilm Reactor) for treatment of leachates from different hazardous waste landfills. Reactor A was equipped with a membrane oxygenatition system for bubble free transfer of oxygen into the bulk liquid. In constract, reactor B was bubble aerated.
The process was found to be remarkably stable. An average DOC removal rate of 68% was achieved with a 12-hour cycle. The emission of biodegradable volatile organic substances was observed to be significantly reduced by using bubble free aeration system.
Study of toluene degradation kinetics in a flat plate vapor phase bioreactor using oxygen microsensors
Authors: Villaverde S. , Mirpuri R. , Lewandowski Z. , Jones W.L. 
Published: May 2018

The paper describes the toluene degradation process in a flat plate vapor phase bioreactor (VPBR) by a Pseudomonas putida 54G biofilm. Oxygen microelectrodes were used to measure oxygen concentration profiles through the gas, liquid, and biofilm phases. The linear shape of the dissolved oxygen concentration profile in the outer 87% of the biofilm thickness suggested an absence of reaction in this layer. Oxygen consumption in the remaining basal 13 % (0.3 mm) followed zero order kinetics with a rate constant of 102.2 g m−3 h−1, for toluene gas concentration of 1.5 g m−3.
The increase in respiratory activity near the substratum was confirmed by microscopic study of cryogenic biofilm sections, and the lack of activity in the surface film was interpreted as a consequence of injury exerted by the toxic substrate. The accumulation of dead cells on the top of the biofilm contributed a resistance to the transport of substrates to deeper layers of the biofilm suggesting a protective role of the outer layer against the harmful effect of the toxic. These results highlight a new conceptual biofilm model in which both microbial growth and inactivation are controlled by substrate transport, leading to a structure that itself controls substrate availability.
Do macrophytes play a role in constructed treatment wetlands?
Authors: Brix Hans 
Published: May 2018

The larger aquatic plants growing in wetlands are usually called macrophytes. These include aquatic vascular plants, aquatic mosses and some larger algae. The presence or absence of aquatic macrophytes is one of the characteristics used to define wetlands, and as such macrophytes are an indispensable component of these ecosystems. As the most important removal processes in constructed treatment wetlands are based on physical and microbial processes, the role of the macrophytes in these has been questioned. This paper summarizes how macrophytes influence the treatment processes in wetlands.
The most important functions of the macrophytes in relation to the treatment of wastewater are the physical effects the presence of the plants gives rise to. The macrophytes stabilise the surface of the beds, provide good conditions for physical filtration, prevent vertical flow systems from clogging, insulate the surface against frost during winter, and provide a huge surface area for attached microbial growth. Contrary to earlier belief, the growth of macrophytes does not increase the hydraulic conductivity of the substrate in soil-based subsurface flow constructed wetlands. The metabolism of the macrophytes affects the treatment processes to different extents depending on the type of the constructed wetland. Plant uptake of nutrients is only of quantitative importance in low-loaded systems (surface flow systems). Macrophyte mediated transfer of oxygen to the rhizosphere by leakage from roots increases aerobic degradation of organic matter and nitrification. The macrophytes have additional site-specific values by providing habitat for wildlife and making wastewater treatment systems aesthetically pleasing.
N- and COD-removal in vertical-flow systems
Authors: von Felde Katrin , Kunst Sabine 
Published: May 2018

Examination of COD-degradation and N-conversion within vertical flow systems and determination of influencing factors was done on constructed wetlands as well as on unplanted soil columns at laboratory scale. Topics of investigation were influent and effluent concentrations and removal efficiency of vertical flow beds, soil water composition at different depths and N-conversion activity with different operating methods, different hydraulic loadings (50, 100, 150 mm/d) and different soil materials.
The extent of degradation and conversion are especially determined by O2-supply which can be influenced by operating method, hydraulic loading and soil material.
COD-degradation and N-conversion take mainly place in soil depths down to 20 cm depending on the O2-supply and soil material. In general a sufficient O2-supply in an intermittently loaded vertical flow bed leads to a COD- and NH4-reduction ≥ 90% and prevents a Ntot-degradation of more than 50%. The determination of N-conversion activities of different soil samples has shown that nitrification activity as well as nitrate reductase activity have their maximum in soil depths down to 10 cm.
Removal of bacteria in subsurface flow wetlands
Authors: Green M. B. , Griffin P. , Seabridge J. K. , Dhobie D. 
Published: May 2018

Removal of E. coli and total coliforms in subsurface flow constructed wetlands is investigated in field surveys and pilot experiments. Both systems use reed beds with 5-10 mm gravel medium receiving secondary effluents. A diurnal pattern of numbers was indicated in the survey of an operational tertiary reed bed at Leek Wootton. Removals of E. coli and total coliforms were compared in dry and wet periods in surveys on two successive years. Removals of about 1.5 to 2.1 log were found in dry weather. Removals fell in wet weather although no change was detected in removal of BOD5, TSS and amm N.
The effect of different flow rates was compared using a pilot reed bed. A trend of increasing removal was seen between retention times of 12, 24, 48 and 120 hrs but variation between samples implied caution. All effluent samples from the pilot had less than 1000 cfu E. coli/100 ml at retention times of 24 hrs or more.
Hydraulic tracer studies in a pilot scale subsurface flow constructed wetland
Authors: King Andrew C. , Mitchell Cynthia A. , Howes Tony 
Published: May 2018

Current design procedures for Subsurface Flow (SSF) Wetlands are based on the simplifying assumptions of plug flow and first order decay of pollutants. These design procedures do yield functional wetlands but result in over-design and inadequate descriptions of the pollutant removal mechanisms which occur within them. Even though these deficiencies are often noted, few authors have attempted to improve modelling of either flow or pollutant removal in such systems.
Consequently the Oxley Creek Wetland, a pilot scale SSF wetland designed to enable rigorous monitoring, has recently been constructed in Brisbane, Australia. Tracer studies have been carried out in order to determine the hydraulics of this wetland prior to commissioning it with settled sewage. The tracer studies will continue during the wetland's commissioning and operational phases. These studies will improve our understanding of the hydraulics of newly built SSF wetlands and the changes brought on by operational factors such as biological films and wetland plant root structures.
Results to date indicate that the flow through the gravel beds is not uniform and cannot be adequately modelled by a single parameter, plug flow with dispersion, model. We have developed a multiparameter model, incorporating four plug flow reactors, which provides a better approximation of our experimental data. With further development this model will allow improvements to current SSF wetland design procedures and operational strategies, and will underpin investigations into the pollutant removal mechanisms at the Oxley Creek Wetland.
Water treatment plant residuals management
Authors: Dharmappa H. B. , Hasia A. , Hagare P. 
Published: May 2018

Water treatment plants produce enormous amounts of sludge. Due to increased environmental concern, recently, there is considerable amount of pressure on the water authorities for the safe disposal of the sludge. Currently, the most acceptable form of disposal is sanitary landfilling, which requires sludge to be dewatered to 20-40% of solids. One of the most commonly used dewatering techniques is sand drying beds. This process is popular because of its reliability, ease of use and low cost. However, one of the basic concerns with this process is the requirement of a large area of land. This could be overcome by chemical conditioning of the sludge, which can accelerate the dewatering rate substantially. At this stage, however, there are no guidelines for the design of the sand drying beds for treating chemically conditioned sludges.
This study is conducted to investigate the design and performance of sand drying beds for treating chemically conditioned water treatment plant (WTP) sludge. Experiments are conducted using laboratory scale sand drainage columns. The results indicate that the drainage rates, after adding polymer, increased by 9 times for clarifier sludge and 20-25 times for filter backwash sludge. Thus, the land area requirement for sand drainage bed can be drastically reduced through polymer addition. Optimal dose of polymer is found to be between 3 and 6 kg/t of dry solids, with dilute sludges requiring high dosages. The cake solids concentration increased from 3 to 12% as the polymer dose increased from 0 to 16 kg/t of dry solids. The variation of drainage rates and cake solids with solids/hydraulic loading rates are found to vary depending on the type of sludges and polymers. The filtrate quality is found to be independent of polymer dose and solids loading rates.
Source separated urine-nutrient and heavy metal content, water saving and faecal contamination
Authors: Jönsson Håkan , Stenström Thor-Axel , Svensson Jan , Sundin Annika 
Published: May 2018

Human urine is by far the largest contributor of nutrients to household wastewater. Source separation of urine can significantly decrease the nutrient load on the recipients. By recycling the urine to agriculture as a fertiliser, with very low levels of heavy metals, the nutrients are made into resources instead of becoming pollutants.
The amounts and concentrations of nutrients and heavy metals in urine solution from a source separating sewage system were measured. The concentrations of nutrients were high. The ratio of nitrogen to phosphorus was close to the expected value, indicating that the system did not have any large nitrogen loss. The heavy metal concentrations in the urine were low, much lower than that in most chemical fertilisers. Per inhabitant and day, 1.34 litres of urine solution were collected. Of this, 0.34 litres was flush water. The low flush water volume was due to the double flush mechanism of the toilets, which saved 48% of the flush water compared with conventional water closets. Per inhabitant and day, 4.9 g of nitrogen and 0.42 g of phosphorus were collected, which was 86 and 81% respectively of the expected amount. The contamination level of faecal material in the source separated urine was low.
Don't reject the idea of treating reject water
Authors: Janus Hans M. , van der Roest Helle F. 
Published: May 2018

Separate treatment of sludge liquor (reject water) is a promising alternative for conventional biological extension of sewage plants with sludge digestion. Treatment of this nitrogen-rich water may significantly save in cost as well as in area demand.
This article evaluates pilot plant investigations of five treatment options: the biofilm airlift suspension reactor, the membrane bioreactor, the bioreactor without sludge retention, stripping of ammonia (both airstripping and streamstripping) and the MAP/CAFR-process. The choice of the optimal treatment method is dependent on site-specific factors. This is demonstrated by two case studies.
The biobed® EGSB (expanded granular sludge bed) system covers shortcomings of the upflow anaerobic sludge blanket reactor in the chemical industry
Authors: Zoutberg George R. , de Been Peter 
Published: May 2018

In this paper a new type of anaerobic reactor is presented. The system has been developed by Biothane Systems and is marketed under the name Biobed® EGSB reactor (Expanded Granular Sludge Bed). In this reactor it is possible to grow and maintain a granular sludge under high liquid (10 m/h) and gas velocities (7 m/h). The most striking feature is the growth of biomass in a granular form, similar to the UASB granules: no carrier material is used. The process is specially suitable to treat waste water that contains compounds that are toxic in high concentrations and that only can be degraded in low concentrations (chemical industry). An example is given for a waste water originating from a chemical factory (Caldic Europoort) in the Netherlands. In this factory formaldehyde is produced from methanol. The waste water is characterised by high concentrations of these compounds (formaldehyde to 10 g/l and methanol to 20 g/l). Due to the special configuration of the anaerobic reactor it is possible to realise a removal efficiency for both compounds of more than 98%.
It is also possible to operate the reactor as an ultra high loaded anaerobic reactor (to 30 kg COD/m3.day) for applications in other sectors of industry (e.g. brewery, yeast, sugar, corn ethanol production etc).
Effect of mixing on the rheological characteristics of conditioned sludge: full-scale studies
Authors: Abu-Orf Mohammad M. , Dentel Steven K. 
Published: May 2018

Conditioning of wastewater sludges with polyelectrolytes prior to dewatering is necessary to increase the sludges' dewaterability. During this conditioning process adequate mixing of the conditioner and the sludge must be attained. This research reports on results from full-scale experiments conducted to examine the effect of mixing parameters upon the conditioned sludge and liquid stream rheological characteristics.
Full-scale experiments were conducted at the 90 MGD Wilmington Pollution Control Facility. Varied mixing conditions were the rotational speed of the flocculation tank prior to dewatering and the filtrate recycling to the flocculation tank. The rheological changes in the conditioned sludge were detected using an on-line ZenoFloc™ system.
Although previous investigations have shown effects of such variations with regard to CST, use of a rheometer as indication of the rheological changes also showed that G variations led to different rheological levels. This allows some insight into conditioning mechanisms as well as optimization. Results also showed that mixing must be optimized and controlled for better dewatering performance.
Changes of some sewage sludge parameters prepared with an ultrasonic field
Authors: Bien January , Wolny Lidia 
Published: May 2018

Studies of sewage sludge conditioning by ultrasonic field concentrate on determination of the increase of water removal effect, which depends on kind of sludge and chemical compounds used in the dewatering process.
An attempt was made to find new methods of sludge preparation before dewatering. Tests presented here focused on digested and difficult dewatered sludge. The sludge was dewatered on a vacuum filter after conditioning with polyelectrolytes and the ultrasonic field. The microscopic analysis was an additional criterion to evaluate changes in the sludge structure after preparation. The polyelectrolyte dose of 3 mg/g d.m. sonicated within 15 sec. resulted in the 50% decrease of sludge volume. Results presented confirmed our previous experiences, concerning the relation between conglomerates of sludge and the effect of dewatering.