1. Background

In the 5th region, located in central Chile, with approximately 1.200.000 inhabitants, infrastructure projects are being implemented or in a planning phase in order to increase the capacity to treat and dispose sew-age. The proposed installations include new or significant retrofitting of sewage treatment plants as well as sea outfalls, including mechanical and chemical treatment previous to disposal to the sea. It is expected that these installations will result in a significant sludge production.
The ORWARE (ORganic WAste REsearch) model, a specific approach for municipal waste and waste-water systems analysis, is used to calculate material and energy flows (MFA: Material Flow Analysis) for various alternatives to organic waste handling and municipal wastewater treatment within a municipality. For evaluation, the results are translated to environmental effects using LCA-methodology.
In order to analyse the sludge management alternatives mentioned above in a structured way, we have proposed to apply the ORWARE model, as well as relevant parts of the ISO 14000- guidelines.

2. Approach

The research project was divided in two stages:
In the first stage the base-line has been established and the relevant data and documentation gathered. This stage also included: definition of environmental impact categories and goals, as well as the sewage and sludge management strategies to be compared

The management alternatives chosen were for sewage chemical or biological treatment while for sludge the management alternatives were based on digestion, composting or lime stabilisation. Alternatives for final destination of the treated sludge were landfill disposal or utilisation as fertiliser in agriculture. 
The environmental impact categories chosen were pathogen emissions, toxicological effects of selected heavy metals and organic compounds, energy use and generation, and emission of green house gases. Costs of management alternatives are also analysed.

3. Results

The following conclusions were derived from this study:

• If ”acceptable emissions and low cost” criteria is applied chemical precipitation is an adequate alterna-tive. If ”lowest possible emissions” is the main objective of sewage treatment biological treatment should be applied.
• Regarding pathogen reduction both chemical precipitation and biological treatment attain an adequate reduction if the treated sewage is to be discharged to the sea. On the other hand, additional disinfec-tion is needed in the case of discharge to rivers
• Where low nutrient emissions are required, biological treatment should be applied
• From the point of view of energy, digestion appears to be better than composting.
• Landfilling implies higher emissions of toxic substances and greenhouse gases and therefore should be reduced
• Control at source should be stressed to avoid heavy metals and toxic organic compounds in the sludge 

Mr. José Ignacio Ramírez was born 1962 and has the degree of Civil Engineer from the Universidad Técnica Federico Santa María, Chile, and M.Sc. Engineering from KTH, Sweden. He has over 10 years experience in the field of water and wastewater both in Sweden and internationally. He works at the engineering firm SWECO - VBB VIAK in the design and evaluation of sanitation schemes, such as water supply and sewage recollection systems as well as sewage treatment plant.  In parallel, Mr. Ramírez is carrying out doctoral studies at Industrial Ecology Department, KTH, Sweden, where he is carrying out the research project “Evaluation of Sludge Management Strategies in Valparaíso and Aconcagua Regions, Chile”.  He has also a number of publications in the subject.

Prof. Galindo is a Civil Engineering; Sanitary and Environmenthal Engineering Specialist from Universidad de Chile and has a Coastal Pollution Training Course - Technical University - Denmark, and Post Title Courses on economics, environmenth, sanitary engineering and other related topics obteined from diferents universities around the World. Member of the Inter American Society of Sanitary  Engineering and Environmental Sciences, the Chilean Society of Hydraulics Engineers and the American Geophisical Union. He is also a full Professor at Universidad Técnica Federico Santa María, Valparaíso, Chile. He has been is Dean, Academic Vice Rector and Member of is Board. Professor Galindo has been a consultant for different chilean governmental institutions and  Member of the Presidential Sustainable Developement Council,  Short Term Consultant For UNESCO, PHO/WHO, CEPAL, PNUMA, CPPS, and THE WORLD BANK. He has over  80 scientifics and proffesionals publications and over   130   engineering designs, apprassials, studies as Project Engineer, Project Manager and Consultor including : Oxidation Ponds  Waste Water Treatment Plants, Oxidation Dishes Waste Water  Treatment Plants , TheMaster Plan for the Aconcagua Valley - Water Resources Planning and Pollution Control, the Great Valparaíso Sewerage Master Plan, Water Supply Tariffs and Concession Studies. Recently he has design the big Valparaiso submarine outfall and the Viña del Mar submarine outfall.