Porto is the second largest city in Portugal in terms of area and population. The city is witnessing rapid growth of population as well as severe water scarcity and demand imbalances like most of the Mediterranean European Union (EU). This situation creates big environmental implications and hazards. To reduce the damaging effect of water scarcity on the city, construction of Wastewater Treatment Plants (WWTPs) is the way ahead, as this will allow the treated water to be re-used thus easing the burden of water shortage on the city. The purpose of this study is the identify suitable sites for the construction of Wastewater Treatment Plants (WWTPs).
Four criteria are chosen for the study, namely, roads, rivers and waterbodies, points of interest such as educational institutions, monuments etc. and the slope of region (using DEM). These criteria are marked as unsuitable, suitable and highly suitable. The obtained results show that majority of the potential sites for the Wastewater Treatment Plants (WWTPs) are found to the West of Porto compared to the East. This is because majority of the criteria are satisfied in this region. Although all aims are achieved in this study, there are some limitations in different perspectives of the study such as details of data and determining other possible criteria that can be used as well as the weights assigned to each, which can be improved by using GIS.
Population growth, urbanization and industrial development are the main factors, which continuously increase water demand (DO MONTE, 2008). Increased globalization processes have caused water shortage, which is a common problem, especially in regions of low precipitation and high evaporation. This also results in competition for scarce water resources between agriculture, tourist activities and other uses. Water scarcity can have negative impacts on the environment, including lakes, rivers and wetlands. Hence, water conservation is the hydrological answer to the water deficit problem, and water reuse is an extremely important component of water conservation strategies. Water can be reused for one or more beneficial purposes: irrigation for agriculture or landscape purposes, industrial supply, non-potable urban applications (such as street washing, fire protection), groundwater recharge, recreational purposes and direct or undirected water supply (DO MONTE, 2008). Thus, wastewater treatment plants (WWTPs) are very important as they meet the restrictive environmental and public health standards which are crucial in today’s rapidly advancing world
A rapid growth in population and tourism has also seen an increase in the generation of sewage and other general wastes. Sewage is wastewater from residential areas that generally consists of wastewater from kitchens, toilets and bathrooms. It is necessary to collect, treat and most importantly, safely dispose the sewage because if this is let into the environment without treatment, it will be drained by the existing ground slope and will reach nearby lakes and rivers. In addition to preventing environmental pollution, wastewater treatment plants aim to reuse the treated water for further consumption, such as agricultural purposes, washing of equipment and even gardening, to name a few. (Rose, 1999) states that the development of wastewater management helps to attain high environmental quality, high yields in food and fiber, low consumption, good quality, high efficiency production and full utilization of wastes. The increase in growth of urban population, health levels and most importantly public awareness have resulted in building many Wastewater Treatment Plants in the last few years
Portugal, like most Mediterranean European Union (EU), experience severe water supply and demand imbalances (DO MONTE, 2008). Half of Portugal suffers from a water deficit. This is mostly due to the rate of evapotranspiration exceeding the surface runoff and infiltration and this is especially aggravated in the summer months. This situation is further aggravated in years of drought, such as the one that occurred in 2005. In the future this is likely to become a frequent event, due to the constant and increasing changes in climate. Tourism, being an important economic activity in Portugal, is pushing water demand, particularly in regions of suffering water deficit. Wastewater treatment and sanitation services in Portugal have seen tremendous advances in services, technologies used and access to services. Nonetheless, problems still occur even where a wastewater treatment plant exists, as they generally do not function well. The increasing demand for water during the driest period induced by increasing needs of water for tourism and agriculture in that period, combined with water quality degradation has led to search for new alternative water sources (DO MONTE, 2008).
The outflow from wastewater treatment plants can pollute the environment and water with its high volume and heavy pollution load. Thus, the locations of wastewater treatment plants are considered to be of utmostimportance that affects the surrounding environment. Suitable site selection is the most important stage of wastewater treatment plants process, causing the least environmental effects. Thus, site selection studies usually utilize many parameters and a systematic methodology is highly needed to integrate the various information, which have been obtained from multi- disciplines (Zhao et al, 2009).The aim of this study is to identify suitable sites for the construction of Wastewater Treatment Plants (WWTP) in Porto, Portugal to help ease the burden of scarcity of water supply in the city. The potential sites will be selected using GIS based methods and tools as this will help limit the chances of errors while also helping coordinate the spatial and non-spatial data.