Search

Computational fluid dynamics (CFD) can be applied to the advancement of dissolved air flotation (DAF) plant design. The use of CFD in design and predictive analysis, in particular here with reference to the upgrading of an existing DAF plant from 30 to 60 Ml/d and associated diagnostics, while still developing, helped by the emergence of ever more powerful computational systems, can be regarded as an established tool providing beneficial and useful data, although on occasions care may be required in the interpretation of results. The initial CFD studies were undertaken using the existing and upgraded works flows and structures at both 'low' and 'high' temperatures, i.e. 2 and 20°C, while the modelling results are reported using graphical representations of 'contours of flow velocity' and 'velocity vectors'. In addition the degree of short circuiting based on T 10 together with other retention parameters T 50 and T 50 /m are reported. Further modifications were also considered: how changes to the incline baffle and tank depth can impact on the predicted distribution, vorticity and in practice on the actual subnatant water quality measured in terms of turbidity. Finally applying CFD to DAF plant design is shown to be a beneficial tool for the designer.

In November 2005 one of the largest combined coagulation ultrafiltration plants worldwide and the largest in Germany went into operation. Its maximum capacity is about 7,000 m3/h of drinking water. Furthermore, a secondary UF stage with a capacity of about 630 m3/h has been used to treat the backwash water of the first stage. The innovative plant design results from an intensive preliminary pilot period, during which several advanced concepts were investigated. The paper reflects the long-term experience with operation and monitoring of the plant over a period of about two years. Up to now, expectations regarding performance in terms of permeability, retention, and reliability have been exceeded. The predicted specific treatment costs of about 10 €Ct/m3 drinking water were achieved or even reduced.

The practice of the Public Utilities Board (PUB) of Singapore is to provide the Singapore public with high quality drinking water. In 2001, in keeping with this practice and due to an increased emphasis on diversification of its water supply, the PUB undertook a major project to expand the capacity of the Chestnut Avenue Waterworks (CAWW) by 273,000 m3/d (60 Migd) using membrane technology. In 2003, Zenon Environmental, as part of a team with the owner's engineer, Black & Veatch, main contractor Thames Water Projects/SembCorp Engineers & Constructors and local Zenon licensee, Hyflux Engineering, installed and commissioned a 273,000 m3/d enhanced coagulation /ultrafiltration membrane plant — the largest of its type in the world at the time. This paper describes the innovative aspects of the CAWW membrane plant design and summarizes the results of its first year of operation. Certain aspects of the full-scale system design are particularly noteworthy. Whereas typical immersed membrane systems employ expensive process pumps to create the vacuum necessary to produce filtrate, the CAWW system relies on a simple siphon to produce filtrate. No permeate pumps are required and this dramatically reduces capital and operating cost through simplified design, reduced controls and minimized floor space. The land area needed for membrane filtration and related process equipment is equivalent to obtaining 180 m3/d of capacity per m2 of land area.

Nitrification kinetics are important for process design, optimization, and capacity rating of activated sludge wastewater treatment plants. A Water Environment Research Foundation (WERF) project on Methods for Wastewater Characterization in Activated Sludge Modeling (WERF, 2003) focused significantly on the development of procedures for measuring the nitrifier maximum specific growth rate, μAUT. In addition, the importance of (and lack of data for) the nitrifier decay rate, bAUT, was identified. This paper describes three bench-scale methods for measuring μAUT: the Low F/M SBR, Washout and High F/M methods. During the WERF project, the importance of pH and temperature control was investigated briefly; this paper summarizes further experimental work performed to address these issues. A summary of μAUT measurements in a number of locations and using the different measurement techniques is provided.

Obtaining reliably high compaction characteristics and low SVI values has enormous economic consequences on activated sludge plant design and operation. Now that use of selectors has become more common for achieving low SVI values, the assessment of the full-scale performance characteristics of activated sludge plants incorporating selectors has high value for the design and operation of future plants. Treatment plant effluent quality is seldom analyzed solely on an average basis and the impact peak events have on effluent quality must be considered in design and operation. Descriptive statistics should also be used to assess selector performance, so that the influence of infrequently occurring values on plant design and operation can be assessed. The performance of 21 activated sludge plants incorporating selectors was evaluated. All the selector plants for which post installation data were available showed that the operating SVI values were significantly improved. One plant studied in detail showed that final effluent quality was significantly better after the selector installation. As a group, activated sludge plants with anaerobic selectors outperform those with anoxic selectors. Dissolved oxygen control is just as important in activated sludge plants with selectors as in conventional activated sludge plants.

Wastewater Treatment plants can cause odour emissions that may lead to significant odour annoyance in their vicinity. Thus, over the past 20 years, several measurements were taken of the odour emissions that occur at WWTPs of different sizes, treatment technology, plant design and under different operating conditions. The specific aspects of odour sampling and measurement have to be considered. I presented some of the results of my odour emission measurements 11 years ago. However, it is now necessary to update the figures by evaluating newer measurement results obtained from measurements taken from 1994 to 2003. These are presented in this paper. Also, the paper highlights the odour emission capacity (OEC) measurement technique which characterises liquids and can be used to assess the results achieved by different types of treatment in the liquid phase, e.g. in a sewerage system. In addition, the OEC is a suitable parameter to set standards for the odorant content of industrial wastewaters that are discharged into the publicly owned sewerage system.

The paper describes the method that led to the design of the 1,500 Ml/day dissolved air flotation (DAF) water treatment plant for Boston's water supply. In particular, the topics of flocculation techniques, floated solids removal and DAF recycle as they relate to very large capacity plant design are covered in detail. The use of mathematical models, including computational fluid dynamics (CFD) software, to refine the design is described.

The development and tasks of IAWQ specialist group on Activated Sludge Population Dynamics have been briefly described. The paper is aimed at three main topics of population dynamics, i.e., competition of nitrifying and organotrophic bacteria, population dynamics of enhanced biological phosphate removal, and activated sludge bulking and foaming. The population dynamics problems are illustrated on examples of Czech activated sludge plants. The examples were selected from a large national survey of activated sludge plants accomplished in 1995–1999. Nitrification proved to be the most difficult process to design and control in nutrient removal activated sludge systems. The survey of enhanced biological phosphate removal processes has shown that the arrangements used in the Czech Republic support well this process. The competition of PAOs with “G” bacteria in full-scale plants is less common than could be expected from previous laboratory studies. The phenomenon of anoxic phosphate uptake was also observed in full-scale plants. Traditional activated sludge separation problem of bulking was observed with much less frequency than expected. On the other hand, foaming caused by M. parvicella, N. limicola and by GALOs has become the most serious operation problem. The survey has also shown that physical rather than biological methods of foaming control are successfully applied in Czech activated sludge plants. The extent of foaming problems underlines the importance of a proper design and construction of final clarifiers.

This paper aims to review the development of wastewater treatment operation and control over the last two decades. Due to the authors' background and experiences there is a special emphasis on the Scandinavian perspective. Since the developments in these countries have been in the forefront in the wastewater treatment area we believe that it may give a reasonable view of the progress also in other countries. The results of regulatory, technical and economical driving forces are discussed. A brief historical review of the progress of nutrient removal is made, and current methodologies for the operation and control of nutrient removal systems is reviewed.

A large scale pilot plant was designed and built and was run over several months in order to collect data and experiences for the final design of a 400.000 P.E. waste water treatment plant. The design and building of this pilot plant is explained with respect to the two objectives examination of plant performance and comparison of different treatment types. In two examples, concerning the influence of temperature and hydraulic balance on EBPR (Enhanced Biological Phosphorus Removal) process the results and their influence on the final design are described. Compared with a design according to the standard design rules in Germany (ATV-A131, 1991), the future large WWTP can meet the effluent requirements with 30% less volume. The costs for the pilot plant were less than 35% of the costs saved by the now possible reduction of tank volume.

A new concept developed for the successful implementation of integrated resource management in urban and protected areas is the production of ‘designer’ or custom-made recycled water for various reuse purposes. The Edward C. Little Water Recycling Facility in El Segundo, California is an excellent example and the only facility in the world and the United States producing five distinct types of recycled water. This paper presents the plant design, critical milestones, water quality challenges faced and problems solved towards consistently meeting the needs of a diverse client base through delivery of a leading-edge range of custom-made recycled waters.

The design of wastewater treatment plants with redundancy to assure a quality end product may be in conflict with efforts to assure effectiveness. Redundancy of major system components is to assure compliance with regulations and protection of the environment and the health and safety of the public and treatment plant staff. However, the capital costs and maintenance associated with redundant equipment does not necessarily enhance facility performance. There are a number of forces driving the level of redundancy in plant designs. Federal and state compliance regulations and the design engineer's past experiences will influence the plant design. To some extent the plant staff may also provide input into the plant design and, therefore, contributes to the redundancy. This report determines alternative methods to address treatment plant redundancy, including examples of methods currently in place and, ideally, insight on the premises leading to these applications. A secondary objective is to identify the similarities and differences in redundancy requirements associated with federal and state regulatory agencies. This title belongs to WERF Research Report Series ISBN: 9781843396413 (Print) ISBN: 9781780404011 (eBook)

A survey was carried out during the late '80s over 7 infiltration percolation plants, serving populations ranging between 400 and 1700. With sand depths, hydraulic loads, influent COD and NTK concentrations respectively ranging from 0.6 to 0.2 m, 0.07 to 0.77m/day, 820 to 75 and 70 to 10 mg/l, and with different operating schedules, this set of plants displays a wide spectrum of infiltration percolation in use. When plants are suitably designed, sized and operated, primary effluents oxidation is very effective and current EEC quality standards for wastewater treatment plant effluents are matched. Disinfection is poor, below the level expected from laboratory and pilot plant data. This is due to non-uniform spreading of the influents on the infiltration areas and exceedingly short circuits and short water detention times in the sand beds. Based on a theoretical approach and on data obtained from these and many other plants, a sizing methodology is provided. Recommended improvements in the spreading technology, as well as in the plant design and management, should lead to more reliable oxidation and disinfection performance

The operating and design experience gained during the past seven years of the Electrodialysis Reversal Plant at Tutuka Power Station was evaluated. Factors like plant design and performance measures such as water recovery, salt rejection, current efficiency and CaSO4 saturation were investigated. The valuable operating experience has led to several design improvements to the EDR units, the clean in place system and the feed water pretreatment. Water recovery of 75%, salt rejection of 65% and current efficiency of 86% were achieved. Water recovery and salt rejection can be improved upon as very low CaSO4 saturation analyses were recorded. Plant availability varied between 90% and 57% but is expected to return to 90% as throughput increases. Membrane life has proven to be in excess of guarantee figures. Total production cost of R361,82/M1 was achieved. In conclusion the plant has successfully achieved its aims during the past seven years.

Environmental Technologies to Treat Nitrogen Pollution will provide a thorough understanding of the principles and applications of environmental technologies to treat nitrogen contamination. The main focus will be on water and wastewater treatment, with additional coverage of leachates and off-gasses. The book will bring together an up-to-date compilation of the main physical, chemical and biological processes demanded for the removal of nitrogenous contaminants from water, wastewater, leachates and off-gasses. It will include a series of chapters providing a deep and broad knowledge of the principles and applications required for the treatment of nitrogen pollution. Each chapter will be prepared by recognized specialists across the range of different aspects involved in the removal of nitrogenous contaminants from industrial discharges. Environmental Technologies to Treat Nitrogen Pollution will be the first book to provide a complete review of all the different processes used for the global management of nitrogen pollution. It will also contain updated information about strategies to achieve nitrogen recovery and reuse in different industrial sectors. Several case studies will document the application of different environmental technologies to manage nitrogen pollution. This book will be of interest to lecturers and graduate students in the following subject areas: Environmental Engineering, Environmental Biotechnology, wastewater treatment plant design, water pollution control, contaminants recovery and reuse. The book will also be an attractive reference for environmental engineering consultants. This title belongs to Integrated Environmental Technology Series . ISBN: 9781843392224 (Print) ISBN: 9781780401799 (eBook)

For information on the online course in Biological Wastewater Treatment from UNESCO-IHE, visit: http://www.iwapublishing.co.uk/books/biological-wastewater-treatment-online-course-principles-modeling-and-design Over the past twenty years, the knowledge and understanding of wastewater treatment have advanced extensively and moved away from empirically-based approaches to a first principles approach embracing chemistry, microbiology, physical and bioprocess engineering, and mathematics. Many of these advances have matured to the degree that they have been codified into mathematical models for simulation with computers. For a new generation of young scientists and engineers entering the wastewater treatment profession, the quantity, complexity and diversity of these new developments can be overwhelming, particularly in developing countries where access is not readily available to advanced level tertiary education courses in wastewater treatment. Biological Wastewater Treatment addresses this deficiency. It assembles and integrates the postgraduate course material of a dozen or so professors from research groups around the world that have made significant contributions to the advances in wastewater treatment. The book forms part of an internet-based curriculum in biological wastewater treatment which also includes: * Summarized lecture handouts of the topics covered in book * Filmed lectures by the author professors * Tutorial exercises for students self-learning Upon completion of this curriculum the modern approach of modelling and simulation to wastewater treatment plant design and operation, be it activated sludge, biological nitrogen and phosphorus removal, secondary settling tanks or biofilm systems, can be embraced with deeper insight, advanced knowledge and greater confidence.

Today's practice in leachate treatment and disposal in the FRG comprises two possibilities:a) the combined leachate domestic wastewater treatment (transportation to the treatment plant either using the sewer system or tank trucks)b) complete, decentralized treatment at the source of the leachate production. As a result of the updating of the general water management law (WHG § 7a) the discharge of waste waters containing dangerous substances (e.g. AOX) into sewer systems is no longer permitted. As there is no possibility of a selective removal of the hazardous substances, the future consequence will be that the whole amount of leachate has to be treated at the landfill site. Existing leachate treatment plants are often designed for average loading rates. Because of the high fluctuations of the leachate quantity such plants are often overloaded. In the past there were two solutions:a) temporary transportation to a municipal treatment plant using trucks,b) recycling of the excessive leachate volume. As transportation is no longer accepted there is only the possibility of recycling left. The feasibility of buffering the runoff peaks has not yet been studied in detail (reservoir management). This cost-favourable option (earth basin with sealing) offers two advantages. First, the plant design can be based on mean conditions while secondly the loading of the plant will be almost constant (no variation concerning the hydraulic loading; concentration equalization effect of the storage tank). Herewith an attractive way of adapting existing plants to the time dependent changing requirements is available.

A general framework for the formulation and analysis of an overall decision support index is discussed. It is indicated that such an index allow evaluation of the combined effects of both design and operation (i) during the planning phase of new WWTPs, as well as (ii) for the evaluation of new operational strategies versus traditional expansions of plants already in operation. Attention is drawn to the problems of incorporating such factors as plant flexibility and robustness against failures in the index. These factors become especially relevant when decisions are to be made that affect the life span of a WWTP. Spatial and temporal separation of the optimisation problem are proposed to make the approach operational. It is not the intention of the authors to provide an exhaustive list of objective criterion functions, but rather to give the reader some examples illustrating the approach.

This paper presents the case of a small wastewater treatment plant taken out of service due to insufficient design and equipment installed. Design assumptions and decisions made for plant restoration based on treatment requirements are outlined and plant operation aspects regarding revealed wastewater characteristics, process efficiency, sludge settling behaviour and equipment control, are discussed. The importance of wastewater characterization as a necessary procedure prior to plant design and construction, is stressed and the feasibility of nutrient removal in small wastewater treatment plants under minimum supervision, is assessed. A simplified mathematical model, as a useful tool to operators, for plant performance evaluation and prediction, is presented.

Swedish effluent discharge regulations and treatment plant design practice are briefly reviewed. The performance with respect to BOD7 and total phophorus removals of different chemical and biological-chemical treatment plants is discussed with emphasize on cold climate conditions. Operating experiences and tests with process modifications are summarized.

A computer based design methodology was developed to facilitate and improve the preliminary design of wastewater treatment plants. It aids design by choosing the least cost treatment system (including sludge treatment and disposal) which meets all the constraints of the particular application. This methodology not only chooses the best alternative treatment system among numerous alternatives but also finds the optimal values of the independent design variables of the processes forming the optimal treatment system. In addition, it has two advantages over currently available design methodologies in that it optimizes wastewater treatment design with respect to the removal of more than one water quality parameter and it considers that sludges produced by different processes have different qualities. This methodology is based on a nonlinear programming method termed optimization by random search and systematic reduction of the size of search region. The design procedure was used to analyze a particular example problem.

This paper provides primarily a discussion of the instrumentation, control and automation aspects of improving the efficiency of certain wastewater treatment facilities including control and operation of sewerage systems, primary and secondary sewage treatment and sludge handling and disposal. Relevant aspects of the activities of the recently constituted IAWPRC's Instrumentation Group receive brief mention including its activities in the areas of evaluation of existing sensors and systems, their relevance to particular needs, attributes and deficiencies, and also in the area of promotion of relevant research and development. A brief appraisal and description of existing sensors and systems, an indication of their usefulness to date and details of alternative instrumentation configurations for use in the enhancement of their general utility is provided. Relevant research and development is reviewed, including relevant remote sensing aspects, and developments in micro electronics and computing: finally some new horizons are explored.