Workshop Summary - PDF document

/ Workshop Summary December, 01 to 03, 2003 at CETESB, São Paulo, Brazil by Companhia de Tecnologia de Saneamento Ambiental – CETESB Escola Politécnica – Universidade de São Paulo - EPUSP December 2003 Prefácio Um dos aspectos mais importantes da gestão em áreas costeiras é o do tratamento e disposição final de esgotos domésticos. A situação se torna ainda mais complexa se considerarmos o contexto social e ambiental da Zona Costeira, patrimônio nacional pela Constituição Federal, com ecossistemas frágeis e densa ocupação urbana e turística, motivada por seus atributos paisagísticos naturais. Uma adequada tomada de decisão quanto a esse problema, portanto, deve se basear não somente nos estudos ambientais, mas também na capacitação tecnológica, incluindo soluções regionais estrategicamente desenvolvidas e com a participação da comunidade local. Nesse sentido, cabe aos organismos governamentais a promoção da conscientização e disponibilidade de informações para a gestão e desenvolvimento sustentável de áreas marinhas e costeiras. Muito embora o atendimento da população por rede coletora de esgotos no Estado de São Paulo seja elevado, acima de 80%, no litoral paulista esse percentual está abaixo desse valor. Se considerarmos ainda o tratamento adequado dos esgotos observamos que a situação requer medidas para minimizar os problemas ambientais. Com algumas exceções, os municípios costeiros despejam parte considerável dos seus esgotos, sem tratamento, em rios, córregos e no oceano. A solução de disposição dos efluentes domésticos a partir da utilização de emissários submarinos, com tratamento preliminar do esgoto bruto, é uma opção a ser cuidadosamente investigada para aplicação no litoral paulista e brasileiro. A sustentabilidade ambiental desta solução passa pela sistematização e aprimoramento dos projetos, pelo monitoramento ambiental na região de descarga oceânica a partir dos difusores, pelo aprimoramento das regras de operação, manutenção e controle tanto das Estações de Pré-Condicionamento –EPCs, como do emissário, além da modelagem do processo de dispersão da pluma de esgoto no mar, consubstanciados numa devida avaliação dos impactos ambientais. Visando discutir todos estes aspectos é que a CETESB – Companhia de Tecnologia de Saneamento Ambiental e a EPUSP – Escola Politécnica da Universidade de São Paulo, tomaram a iniciativa de organizar este evento, no qual especialistas brasileiros e convidados da Alemanha, Austrália, Escócia, Espanha, Estados Unidos, Portugal e Itália estarão reunidos discutindo essas e outras questões, junto com empresas públicas e privadas. Vinte e quatro apresentações técnicas, material didático distribuído aos participantes e uma mesa redonda de discussão final do evento, entendemos, irão proporcionar rica massa de informações para reflexão, além de critérios e parâmetros técnicos para subsidiar propostas de normas e instrumentos legais. Isso tudo proporcionará o aprimoramento da operação dos atuais emissários e projetos futuros, assim como a avaliação de impactos e o licenciamento ambiental, constituindo mais um passo para a conservação de nossa região costeira. CETESB – Companhia de Tecnologia de Saneamento Ambiental EPUSP – Escola Politécnica da Universidade de São Paulo Preface Waste water treatment and the disposal of its residuals is one of the most important aspects of coastal management. The situation turns out to be more complex if social and environmental contexts are considered: The federal constitution declares the coastal zone a national heritage, it has a fragil ecosystem, a dense urban and touristical population due to its natural environmental attributes. Adequate decision making for this problem has to be based not only on environmental studies but also on technical capabilities including regionally developed solutions with local public participation. Therefore governamental organs have to make aware of these problems and provide information for a sustainable development and management of maritime and coastal areas. Although more than 80% of the population of São Paulo state is connected to a sewer-system the São Paulo coastal area is below that value. If we additionally look on the subsequent treatment of the collected sewage it can be observed that the situation requires measures to minimize environmental problems. With some exceptions, the coastal municipalities dispose a considerable part of their sewage, without any treatment, in rivers, canals or the ocean. The usage of preliminar waste-water treatment plants and subsequent ocean disposal via submarine outfalls for domestic sewage is one option which has to be carefully studied for its application at the brazilian coastal areas. To be environmental sustainabel this solution demands a systematization and improvement of such projects, an environmental monitoring of the disposal area starting at the diffusers, an improvement of operational rules, the maintenance and control of the treatment plants and the outfalls itself and beyond that: previous modeling of waste plume dispersion processes for environmental impact assessments. In view of discussing all mentioned aspects CETESB - Environmental Sanitation Technology Agency and EPUSP - Polytechnical School of the University of São Paulo took the first initiative and organized this event, where brazilian specialists and foreign specialists from Germany, Australia, Scotland, Spain, United States, Portugal and Italy will discuss together with public and private companies. Twenty-four technical presentations, documents and a round table at the end of the event will create a huge base of informations to be studied and discussed. Besides, technical parameters and criterias support proposals for regulatory issues. All this will provide and improve the operation of existing and planned outfalls, as well as environmental impact assessments, giving the opportunity of making one more step for the conservation of our coastal region. CETESB - Environmental Sanitation Technology Agency EPUSP - Polytechnical School of the University of São Paulo Workshop Summary Submarine Outfalls: Design, compliance and environmental monitoring Helicopter view of Santos bay with a slight view of the sewage plume from Santos outfall. Front: City Praia Grande. Back: The island of São Vicente (approx. 700.000 inhabitants and 1.4mio during high season). São Paulo coastal water quality problems The workshop was opened by the Director of the Environmental Protection agency of the state São Paulo, Lineu José Bassoi, who described the legislation and environmental management of sewage disposal in São Paulo coastal waters. The importance for the São Paulo coast was clearly shown by the number of inhabitants (1.7mio.), which grows continuously (about 6% yearly) and almost doubles during high season times along the approximately 900 km long coastline with its 430 km beaches. On the average only 40% of the households are connected to sewer-systems. Only 40% of the sewage is treated in simple Pre-treatment plants with long sea outfalls (8) or conventional treatment plants with river outfalls. Legislation depends mainly on national laws (CONAMA), federal laws and their management, monitoring and licensing from federal agencies (like CETESB). A major problem is the lack of an environmentally sound sanitary masterplan, where different wastewater treatment options and their related disposal options (high treatment levels lead to low concentrated coastal effluent disposals (short outfalls) and highly concentrated land sludge disposals (huge landfills, incineration) or low treatment levels lead to high concentrated coastal effluent disposals (long outfalls) and fewer low concentrated land sludge disposals) are required. The week before the workshop 78 out of the 128 weekly monitored beaches have been declared improper for bathing. Sao Paulo coast Submarine outfalls present a viable solution Prof. Jayme Pinto Ortiz from the University of São Paulo showed the necessity of the systematization of sea outfall projects including the decision criterias for their related treatment options and outfall lengths respectively. Advantages of outfalls are their environmental and operational efficiency due to minor maintenance and energy needs. Disadvanteges are the huge planning needs and long planning periods and difficult monitoring as well as the prevalent public concern in “dumping sewage in the sea”. It was pointed out that the university has to support the planning and monitoring issues to avoid either misunderstanding of these complex processes and minimize environmental impacts. Cost-benefit analysis and modling techniques are the major contributions on that field. Location criterias and minimization of environmental impacts Leonardo Silva Macedo from the São Paulo Sanitation company SABESP presented principal criterias on how to decide which location and geometry of an outfall and which related treatment level is best for minimizing environmental impacts. Favourable (e.g. open coastline like Praia Grande) and non-favourable sites (e.g. closed bays like Santos Bay) for outfalls can be defined by studying nautic maps, oceanographic informations, municipality and public informations about sensitive areas (beaches, fishing or aquaculture). The minimization of environmental impacts than can only be done be modelling the hydrodynamic mixing and dispersion processes, as well as bacterial decay processes for planned discharges and their interaction with existing discharges. Outfalls (red lines) along the Baixada Santista: in the middle Santos Bay outfalls, right: Guarujá, left: Praia Grande I and II Land treatment options before discharge through outfalls Pedro Além Sobrinho from the University of São Paulo listed several treatment schemes and their treatment efficiency. He separates between the liquid phase (effluent) and the solid phase (sludge) of the sewage, which, depending on the treatment level cause environmental impacts on or off shore, if not considered in detail. If high treatment levels are demanded he treatment for the solid phase will be more expensive than for the liquid phase. For long submarine outflalls he recommended at least the usage of fine screens (1.5mm) including intensive maintenance and sand and oil removel. The common usage of effluent disinfection using chlorine is often not necessary and should only be done during high season. Floating materials from Santos outfall due to bad working or not operating screens Permitting and Monitoring of submarine outfalls Claudia Lamparelli from CETESB is responsible for the licensing and monitoring of submarine outfalls and has to determine whether they are conforming with the allowed licence values to minimise the coastal pollution. Pollutant discharges can result in a range of environmental impacts including: Poor recreational water quality (swimming, wading and boating) due mainly to pathogen (& indicator bacteria) loadings; Eutrophication (excessive plant growth including algal blooms) due to nutrient loadings; Toxicity to humans and ecosystems due to a range of chemicals in sewage and accumulation of contaminants in organisms and sediments due to chemicals in sewage. These have to be monitored, licencsed and controlled to preserve environmental values of the region. Water quality of beaches, rivers and discharges are monitored by CETESB. Major problems are related to the definition of either modelling plans for planned discharges or monitoring plans for existing discharges where length scales (area of influence) and time scales (probability of influence) for limit values as well as the parameter choice itself is still not standardized. Monitoring results still show a huge need for better WWTP monitoring (large floating materials pass the WWTP and are discharge directly to the ocean), outfall monitoring (no flowrates or concentrations of the discharged effluent are known) and environmental monitoring (contamination of the sediment due to accumulation of settlable material around Santos outfall) as well as for modelling support to consider multiple sources and future installations. Visible outfall plume at the channel of São Sebastião Dilution and dispersion processes for submarine outfalls Prof. Gerhard Jirka from the University of Karlsruhe, Germany, provided an overview over the physical processes which can be divided into the near-field region in the vicinity of the discharge location and the far-field region at large distances. The dominant near-field process is buoyant jet entrainment that leads to an effective reduction of pollutant concentrations that can be controlled by the discharge design. Other processes include various boundary interaction processes, such as surface or bottom contact and terminal layer formation, as a transition to internal density currents. The lecture was illustrated with various laboratory and field observations and cites different design examples. Laboratory studies of discharge processes for a single submerged outfall discharging in a stratified ambient, where the plume gets trapped before reaching the water surface Wastewater plume Modeling Gerhard Jirka succeeded the description of the physical processes presenting modelling methodologies for the waste plume dispersion processes in the coastal environment surrounding the discharge location. Dominant processes that lead to a large-scale reduction of pollutant concentrations are buoyant spreading, ambient advection and dispersion by the action of coastal currents and turbulence, and finally pollutant transformation and decay, such as bacterial die-off. The time scales of these processes range from hours to several days. Special aspects in linking near- and far-field simulation models to predict these distributions have been discussed and examples from monitoring studies have been shown. He recommended furthermore not only to consider concentration values but also pollution loads. Example result of a Lagrangian particle tracking model (Delft3D-PART, Delft Hydraulics), for a sewage discharge Near Field Model CORMIX Robert Doneker from the Portland State University and developer of CORMIX (together with Gerhard Jirka) explained the CORMIX methodology. CORMIX is a USEPA-approved simulation and decision support system for environmental impact assessment of mixing zones resulting from continuous point source discharges. The system emphasizes the role of boundary interaction to predict steady-state mixing behavior and plume geometry. Effluents considered may be conservative, non-conservative, heated, or contain suspended sediments. Advanced information systems provide documented water quality modeling, regulatory decision support, visualization of regulatory mixing zones, and tools for outfall specification and design. CORMIX software is licensed and distributed by MixZon Inc. Left: CORMIX Modeling result of a sewage discharge; right: visualisation of a multiport diffuser Combining physical and numerical models with remote sensing data. Jayme Ortiz presented simple physical modeling results of single port hot water discharge in cold water reservoir and its comparison with CORMIX with good correlation. On the other hand, the identification and mapping of wastewater plumes of Santos outfall through satellite images analysis showed good agreement with CORMIX results. Additionally some simulations were shown using FLUENT to model Phosphorus and Nitrogen for the Araçá (São Sebastião) submarine outfall. Preliminary results shows that FLUENT can be used to reproduce the plume dispersion process in the transition and far field. The usage of several techniques supporting and complementing each other helps to understand the mixing and dispersion processes as well as to monitor possible effects. Left: Remote sensing of Santos outfall plume via satellite images; right: plume modelling using FLUENT Far Field Model MOHID Ramiro Neves from the Instituto Superior Tecnico de Lisboa, Portugal, described the situation at the Portuguese coast, where the more intense usage of fertilizers, the polluted river discharges and the movement of people to coastal areas and their near-shore sewage discharges caused an increase of nutrients in coastal waters causing polluted water bodies. The perception of the population instead was only related to sewage discharges and not to other pollutant sources although the sewage disposal in coastal waters might be the only environmentally sound solution for these areas, if an adequate treatment level is guaranteed. MOHID is an integrated model for the hydrodynamics of near field dispersion and far field water quality. Applications at the submarine outfalls of Guia and S. Jacinto in Portugal Lisbon and Aveiro showed the environmental impacts related to eutrophication of the Tejo estuary and impacts on beaches near the outfalls. All results showed minor influences of the discharges through submarine outfalls on water quality compared to near-shore discharges or river discharges. MOHID modelling result showing the environmental impact zone of a primary treated sewage discharge at the Portuguese coast near the Tejo Estuary Physical and numerical modelling experience Paolo Alfredini from the Hydraulic Laboratory of the Univeristy of São Paulo showed results of studies of coastal and estuarine processes along the 8000 km brazilian coastline. There is bathymetrical data of the São Paulo coast, wave data and coastal and estuarian circulation data available for further studies related to pollutant dispersion processes, as well as further physical modelling of outfalls is planned. Physical modelling at the hydraulic laboratory Analysis and control of environmental impacts of outfalls Peter Scanes from the Environment Protection Authority New South Wales, Australia provided a complete monitoring programme and its related results. Monitoring of a large development like a sewage outfall should move through a series of stages: 1.) Design assessment (before outfall is built): Expected performance of the WWTP and outfall should be expressed as environmental outcomes (e.g. no change in ecological communities more than 50 m from outfall, or no visible plume, or beaches passing health �criteria 90% of time), 2.) Verification Assessment (after outfall is built): Intensive monitoring of the outfalls’ performance against the performance criteria needs to determine whether, under a wide range of environmental conditions, the outfalls are performing to expectation and 3.) Performance Assessment (control/impact): long-term, usually less intensive stage which provides confidence to operators, regulators and the public that the plant and outfall continues to meet environmental expectations (involving intensive investigation of plant inputs and internal performance criteria = license condition; ambient monitoring of a small number of key environmental criteria which provide triggers to more detailed monitoring if expectations are not maintained). In NSW Australia, a five year, multi-disciplinary Environmental Monitoring Program (EMP) measured the environmental performance of Sydney’s deepwater outfalls against a wide range of criteria related to impacts on marine ecosystems and on human utilization of marine resources: Beach and bathing water quality dramatically improved; concentrations of organochlorines in fish and deployed oysters declined to background in the vicinity of the old shoreline discharges and did not increase measurably at the new deepwater outfalls, contamination of sediments in the vicinity of the new outfalls did not change to an extent that can be readily measured by the technology and methods utilised in these studies, computer modelling of plume behaviour and the studies of biota and sediments showed that the enhanced rate of dilution and dispersion has resulted in a decreased likelihood of any given organism or area of sediment encountering (and therefore accumulating) high loads of a contaminant, but concomitantly there has been an increased likelihood of more organisms accumulating small amounts of contaminants. He concluded that effective operation of ocean outfalls can be facilitated by well designed assessment programmes incorporating a variety of strategies for monitoring. This monitoring can identify impacts and human health risk and provide information back to operators that can inform better plant and outfall management. Careful use of licences by regulators will ensure that operation of plants and outfalls remains within appropriate criteria and minimise environmental and environmental harm. BACI: Before/After, Control/Impact Monitoring Predictive modelling with probabilistic resutls leads to decision making José Juanes from the University of Cantabria, Spain, addressed Impact assessments carried out during the pre-commissioning stage, at both the planning and the project levels, both based on the evaluation of risks (probability x consequences) estimated for different “sanitation schemes”, taking advantage of the predictive power of mathematical models. This process consists of four consecutive stages: 1) Design and selection of alternatives (strategic assessment), 2) Risk evaluation for different scenarios (impact assessment), 3) Verification of adverse effects (objective-oriented monitoring) and 4) Action plan for mitigation of registered impacts (management of pollution events). Monitoring programs were based on modeling predictions and assumptions about likely responses of a great variety of environmental compartments to disturbances, through the implementation of a program of continuous measurements, that support both the definition of the specific objectives to be addressed and the more appropriate technical designs, in order to produce predefined management information useful for decision making. But: “risk-free decision-making is an impossible goal. Environmental-oriented planning strategies for the design of sanitation systems in the coastal zone are the only way to protect the aquatic environment, its resources and human health. CantabriaBasque CountryCantabriaBasque Country 3 km 01002000UFC/100ml Alternative West Alternative East Simulations of sewage discharges from the two outfalls proposed for the sanitation system of Bilbao. Dashed lines indicate the administrative limits for the coastal waters of Cantabria and the Basque Country Left: regulatory monitoring points almost without any data; right: better monitoring scheme supported with model prediction Design and construction of sea outfalls Carlo Avanzini from MECC Consuting, Italy explained that design cases for spatially and temporally changing currents, winds and density profiles have to be defined and cases of well-mixed and stratified waters are to be studied. Wave actions on submarine structures are major tasks for the pipe stability itself and its fixation on the ground. Pipes can laid on the seabed, in a trench or tunnelled to the discharge location. Headwork and storage buildings have to be designed for temporally changing discharge and ambient conditions. High Density Poly Ethylene Pipe is laid on the seabed. Optimization and Operation of the outfall Tobias Bleninger from the University of Karlsruhe, Germany, stated that inadequate attention on the internal diffuser hydraulics often result in hydraulic problems (partial blockage, high head losses, uneven flow distribution, salt water intrusion and poor dilution) causing higher energy demands and stronger environmental impacts. A computer program (CorHyd) was presented to analyze and optimize diffuser design alternatives as well as existing diffuser configurations for different discharge and ambient conditions. CorHyd recommendations help reducing construction, operation and monitoring costs by optimizing geometries and if necessary recommending cheaper inflow conditions. Left: Complete tunnelled outfall construction from the Boston outfall, with risers; right: diffuser pipe laid on the seabed with attached variable area orifices to prenvent salt-water intrusion. Outfall operation manual Carlo Avanzini said that after the pipe installation, still much shall be done. Apart the stabilization and protection, an operation testing should be considered essential for knowing the operating characteristics in view of the monitoring. Moreover, when the outfall’s “hardware” is completed, it is still imperative to proceed with the necessary “software”: the preparation of the complete final reports and manuals, which shall supply to the Owner all the information on what he has received and on what shall be done to keep the outfall alive and efficient. There is a must for an “Inspection and Maintenance Manual”, “Monitoring Manual”, and an “Operation Manual”. Outfall pipe protection and fixation by mattresses or stones Montoring of the outfall operation and construction Carlo Avanzini stated that after an outfall is installed, tested and commissioned, the “control” of the outfall operation has to be monitored. The process of “control” includes such steps as inspection, maintenance, operational control and monitoring, not only of the outfall itself, but of the whole system inclusive of the WWTP discharge facilities. It is emphasized herewith that “monitoring” does not include only the evaluation of the environmental conditions of the receiving water body, but also the assessment of the operating conditions. A significant approach to the “operational monitoring” has been obtained through the E.U. Life Aquarius project, where flowrates at the outfalls entrance and the orifices have been measured, current and density profiles online sent to the coastal monitoring server. Scheme of complete outfall and ambient online monitoring programme with multiparametric probe with current meter (left) and diffuser port velocity sensors (right) Oceanographic surveys and monitoring data Luiz Roberto Tommasi from the Foundation of aquatic Studies and Research, São Paulo, Brazil presented physical chemical, biological and toxilogical data from the waters around the outfall locations. He concluded that it cannot shown, that the existing outfalls harm the environment and that in some case, where higher pollution values have been found these are related to illegal coastal discharges or diffuse discharges. Measured data around outfall Decision Criterias The present study shows a decision making process between two predominant systems in the São Paulo coast: waste water treatment plant operated with sequencing batch reactor (WWTP – SBR) and pre-conditioning plant with submarine outfall. A cost benefit survey of the two systems and analysis of emission criteria of mixing zone implemented by environmental agencies and guidelines had been carried out to inquire the possibility of adoption of such criteria for the São Paulo coast. Furthermore oceanographic monitoring campaigns are summarized and compared with modelling data. Helicopter view of sewage plume discharged by the outfall of Praia Grande European and mediteranean experience – case studies The „combined approach“ in the new EC-Water Framework Directive (WFD) consisting of environmental quality standards in addition to emission limit values promises improvements in the quality characteristics of surface waters. However, the specification of where in the water body the environmental quality standards apply is missing in the WFD. This omission will limit its administrative implementation. A clear mixing zone regulation is needed so that the quality objectives of the WFD are not jeopardized. This need is demonstrated using the examples of point source discharges into rivers and coastal waters, respectively. Furthermore, water authorities will have to make increased use of predictive modeling techniques for the implementation of the “combined approach”. The European regulation demands for secondary treatment for all marine discharges. If the discharger demonstrates that secondary treatment has no environmental benefit over primary treatment an exception is made. Modeling and monitoring studies have to be made herefore. And in most of the cases primary treatment is sufficient. In Portugal the mixing zone extents are one sea-mile around the outfall. In Spain an initial dilution of 100 and a minimum outfall length of 500m is demanded. It was concluded, that domestic discharges do not harm or change the environment, but industrial discharges (in Europe often connected to domestic sewers) instead could be problematic. Additional regulations are from the World Health Organisation and other UN institutions. Example of regulatory mixing zone specification for offshore submerged coastal discharges: The horizontal extent of the mixing zone is defined by some multiple N of the average water depth Have at the sea outfall. USA experience Water quality legislation in the United States was initiated by the Federal Water Pollution Control Act of 1972. This act required that all waters be “fishable and swimable” and gave the Federal government responsibility for improving water quality. Technology based standards were developed for wastewater treatment before disposal and ambient water quality standards were developed to manage receiving water quality. Water quality standards can be narrative or numeric and must support the designated use of the water body. Ambient water quality standards can be waived within a “mixing zone” to allow for initial dilution of waste discharges, as long as the water body as a whole is not degraded. In some cases, USEPA is phasing out mixing zones for persistent and bioaccumulative toxic materials. Sewage plume of Santos outfall