Helena Alegre

A performance indicators system for urban wastewater treatment plants

A performance assessment system (PAS) is an important instrument to provide a cost-effective and sustainable management of wastewater treatment plants (WWTPs). Despite the fact that many PASs have been developed in recent years, important aspects of WWTP evaluation have not yet been considered. This paper presents the framework and the overall performance indicators of a PAS developed for urban WWTPs.

Performance Indicators for Water Supply Services - Second Edition

The IWA Performance Indicator System for water services is now recognized as a worldwide reference. Since it first appearance in 2000, the system has been widely quoted, adapted and used in a large number of projects both for internal performance assessment and metric benchmarking. Water professionals have benefited from a coherent and flexible system, with precise and detailed definitions that in many cases have become a standard. The system has proven to be adaptable and it has been used in very different contexts for diverse purposes. The Performance Indicators System can be used in any organization regardless of its size, nature (public, private, etc.) or degree of complexity and development. The second edition of Performance Indicators for Water Supply Services represents a further improvement of the original manual. It contains a reviewed and consolidated version of the indicators, resulting from the real needs of water companies worldwide that were expressed during the extensive field testing of the original system. The indicators now properly cover bulk distribution and the needs of developing countries, and all definitions have been thoroughly revised. The confidence grading scheme has been simplified and the procedure to assess the results- uncertainty has been significantly enhanced. In addition to the updated contents of the original edition, a large part of the manual is now devoted to the practical application of the system. Complete with simplified step-by-step implementation procedures and case studies, the manual provides guidelines on how to adapt the IWA concepts and indicators to specific contexts and objectives. The manual includes a new version of the software Sigma Lite incorporating all the new developments and an improved graphical user interface. This new edition of Performance Indicators for Water Supply Services will be an invaluable reference source for all those concerned with managing the performance of the water supply industry, including those in the water utilities as well as regulators, policy-makers and financial agencies. This title belongs to Manual of Best Practice Series . ISBN: 9781780405292 (eBook) ISBN: 9781843390510 (Print)

Translating removal efficiencies into operational performance indices of wastewater treatment plants.

Removal efficiencies are often used to assess the performance of a single or a group of unit operations/processes (UOPs) of a wastewater treatment plant (WWTP). However, depending on the influent concentration (Cin), the same efficiency of removal (Er) may be insufficient or excessive to achieve the UOP or WWTP effluent quality requirements, expressed by concentration limit values (LVs). This paper proposes performance indices (PXs), Er-based, as new metrics for benchmarking, i.e. for assessing and improving the performance of each UOP or treatment step and ultimately of the WWTP as a multi-barrier system, and comprehensively describes the stepwise method of translating Ers into PXs. PXs are dimensionless and vary between 0 and 300 to define three performance levels: unsatisfactory (0-100), acceptable (100-200) and good (200-300) performance. The method developed takes into consideration Cin and LV, and the reference values for judging the performance are given from Er-Cin typical ranges and Er vs. Cin model curves, LV based and field data based. The general equations of the Er model curves are derived. A set of six curves is calibrated for TSS (Total Suspended Solids) and COD (Chemical Oxygen Demand) removal by primary sedimentation and activated sludge systems (carbon or combined carbon and nutrients removal), using 5-year (2006-2010) field data from five Portuguese WWTPs. A statistical analysis of the PX results is additionally proposed to assess treatment reliability. The new method is applied in two WWTPs and the PX results are compared with those of conventional measures - Er and performance indicators (PIs). The results demonstrate that, whereas a simplistic Er-driven or PI-driven management of the WWTPs shows limitations, the developed PXs are adequate measures for benchmarking removal efficiencies towards WWTP reliability and sustainability.

Infrastructure Asset Management of Urban Water Systems

IAM methods partially differ from those applicable to managing other types of assets. One of the reasons is the fact that such infrastructures have indefinite lives, in order to satisfy the permanent needs of a specific public service. Infrastructures are not replaceable as a whole, only piecemeal. Consequently, in a mature infrastructure, all phases of assets lifetime coex‐ ist. Additionally, in network-based infrastructures, it is frequently not feasible to allocate levels of service to individual components because there is a dominant system behavior (e.g. symptoms and their causes often occur at different locations).

Prioritization of rehabilitation interventions for urban water assets using multiple criteria decision-aid methods.

The aim of this paper is to compare sorting and ranking methods for prioritization of rehabilitation interventions of sewers, taking into account risk, performance and cost. For that purpose multiple criteria decision-aid (MCDA) methods such as ELECTRE TRI for sorting and ELECTRE III for ranking are applied in a real case-study and the results obtained are compared. The case study is a small sanitary sewer system from a Portuguese utility located in the metropolitan area of Lisbon. The problem to investigate is the prioritization of the sewer candidates for rehabilitation. The decision maker (a panel group of specialists) has chosen five assessment measures: water level and maximum flow velocity (hydraulic performance indices), sewer importance and failure repair cost (collapse-related consequences of failure) and the risk of collapse. The results show that the outcomes from ELECTRE III are easier to understand than those from ELECTRE TRI method. Two different sets of weights were used, and the sorting and ranking results from both methods were found to be sensitive to them. ELECTRE TRI method is not straightforward as it involves technical parameters that are difficult to define, such as reference profiles and cut levels.

Performance assessment of water supply and wastewater systems

This paper addresses the issue of performance assessment in water and wastewater systems by reviewing two of the tools that are available to the companies operating in this field: systems of performance indicators and technical performance assessment through simulation. The paper focuses on a technical performance evaluation framework and its application to wastewater systems. The assessment is carried out through the application of utility functions to the networks elements, and the production of performance-oriented graphs that yield concise and informative views about the systems behaviour. Two case studies involving a combined sewer system and a separate domestic system are presented in order to illustrate the method.

WATER INFRASTRUCTURE ASSET MANAGEMENT: A METHODOLOGY TO DEFINE INVESTMENT PRIORITIZATION

A key component of water supply infrastructure asset management is the establishment of investment priorities: how to decide among investments of different types, values, functions, and physical conditions? The decision may be straightforward in some cases, but in most situations managers find themselves in the situation of having to adopt subjective criteria. Nowadays, decision making needs a comprehensive approach that takes into consideration cost of building, operating, maintaining and disposing of capital assets over their life cycles. Conversely, factors such as improvement of customer level of service, improvement of system reliability, or minimization of negative impacts of the infrastructures on the society and on the environment should be incorporated into the investment prioritization process. This was the motivation for a project promoted by the water utility EPAL, S.A. and jointly developed with a research team. The objective was to define a conceptual model and develop an operational tool able to assist decision-makers in the prioritization of water distribution system investments. In this context, an integrated decision support tool was developed taking into account direct, indirect and external costs during the life cycle of the assets. The model includes different points of view and service goals important for water infrastructure asset management (e.g., quantity and pressure, water quality, reliability, water losses, energy, operation and maintenance, and environment) and was developed for different infrastructure components (water mains and service connections, treatment facilities, pumping stations and service reservoirs). The model was implemented into an MS Excel-based application that allows for input data and report production. Detailed tests were made for the three most common types of investments identified by the involved water utility. Sensitive analyses were carried out and conclusions drawn about the most important and critical points of view for each case. Based on the results of the model applied to this set of investments, three different alternative approaches for investment prioritization are analyzed and discussed. The paper describes the principles of the conceptual model, summarizes the main features of the computer application, discusses its applicability, strengths and weaknesses and presents some recommendations for further development.

Moving urban water infrastructure asset management from science into practice

iGPI, the National Initiative for Infrastructure Asset Management is a Portuguese collaborative project led by LNEC (National Civil Engineering Laboratory, Portugal) through which 19 water utilities develop their own infrastructure asset management (IAM) systems and plans in a joint training and capacitation programme. Technical assistance to the participating utilities is ensured by LNEC, IST (Technical University of Lisbon) and Addition, a software development company. The water utilities get collective as well as one-on-one support and specific training. They benefit from networking with the other utilities in a common and simultaneous process, with similar difficulties and challenges, leading to an effective sharing of solutions. The developed products, including training materials, templates and guidelines for developing strategic and tactical IAM plans, are available to the general public. This project has greatly contributed to the establishment of reference methodologies and standards for IAM planning, in a range of utilities of widely diverse size and context, effectively defining an accepted best practice. This paper discusses the projects format and its advantages, and goes on to describe the main outcomes, including selected cases and final products.

Methodological Approach for the Rehabilitation of Water Distribution Systems: Case Study Application Based on the CARE-W System

Rehabilitation is nowadays a hot topic of the agenda of most European water supply stakeholders. Many existing water mains have reached their expected lifetime, and high capital investments are required to renovate them. Well-devised methodologies for rehabilitation planning are needed, in order to define what, when and how to rehabilitate water transmission and distribution networks. However, rehabilitation can be motivated not only by asset ageing, but also by a combination of other concurrent factors, such as unsatisfactory hydraulic performance, water quality problems (e.g. color, taste, smell, lead), need for expansion, insufficient reliability, high level of water losses, etc. Comprehensive and well-devised methodologies for rehabilitation planning are therefore needed. This paper proposes a general approach to network rehabilitation and uses the case study of Brandoa (Amadora, Portugal) to illustrate it. This network was selected because the identification of a good rehabilitation solution in this case is far from obvious. The network presents a combination of problems, such as excessive pressure problems in some areas, insufficient pressure in other areas, material ageing symptoms in some pipes and very high service connection failure rate. Conversely, Brandoa is a problematic area in social and urban organization terms, having started as an illegal settlement in the 50s. The implementation of the recommended rehab methodology is supported on the use of CARE-W tools, complemented with network simulation and with a Technical Performance Assessment tool. The CARE-W system (Computer-Aided Rehabilitation of Water Networks) was developed under a project of the 5th Framework Program of the European Union and aims for assisting water utilities in setting up strategic and tactical rehabilitation plans. The project ended in 2004, and since then a number of applications took place in various countries. Challenges, constraints and objectives depend on country to country and case to case, and the experience achieved is vital to allow for transforming the current prototype system into a fully developed and professional tool. In Portugal, we aim for enhancing CARE-W prototype, transforming it into a professional software application that is easier to use, is better adapted to the Portuguese context, and is complemented with some new features. This paper was presented at the 8th Annual Water Distribution Systems Analysis Symposium which was held with the generous support of Awwa Research Foundation (AwwaRF).

Diagnosis of Hydraulic Performance of Water Supply Systems

Hydraulic simulation and demand analysis have been, for some years now, key research areas for the water supply team at the National Laboratory of Civil Engineering of Portugal. It is felt that the planning, design, operation and control of water supply and distribution system are greatly improved by the use of adequate analysis and processing tools.