• by Fabíola Ortiz (porto de galinhas, brazil)
  • Inter Press Service

'It must be recognised that water quality is a serious problem, with high levels of pollution due to bad management and poor governance. Water reserves in aquifers are rapidly being depleted,' Walter Ubal of the Canadian government's International Development Research Centre (IDRC) told IPS.

Urbanisation is increasing the demand for water, and so the cost of providing and purifying it has become 'extremely high,' said this expert on natural resource and environmental management, attending the 14th World Water Congress in Porto de Galinhas, a beach resort in the northeastern Brazilian state of Pernambuco.

The conference, which opened Sunday Sept. 25, was organised by the Pernambuco state government and the International Water Resources Association (IWRA), an NGO network of experts on sustainable water use.

'The worst of it is that we are using water treatment options that may be more costly and generate greater environmental impacts than they need to,' said Ubal, who acknowledged that no method of purifying water is completely sustainable.

'We need to find the least harmful methods, which can also be tailored to social needs,' he said.

'This involves a huge effort, because a large sewage treatment plant can produce odours and drive down housing prices, involving social questions which are more complex than merely technical matters,' he said.

Since April Adalberto Noyola, head of the Engineering Institute at the National Autonomous University of Mexico (UNAM), has been coordinating a team of experts studying sewage treatment plants in the region in search of more sustainable processes and technologies to improve the situation in Latin America.

The aim of the research project, which covers Brazil, Chile, Colombia, the Dominican Republic, Guatemala and Mexico, is to assess the environmental impacts of the region's most commonly used treatment technologies and identify strategies to reduce greenhouse gas emissions, Noyola told IPS.

'Wastewater is treated in order to avoid polluting soils, rivers and seas; as society develops and water demand increases, many regions are seeking to reuse water for irrigating farmland and for industry, although not as yet for household use,' he said.

In Brazil and Mexico, which between them are home to half the total population of Latin America and the Caribbean, around 30 to 40 percent of wastewater is treated.

Chile was included in the study because its water and sanitation services are similar to 'those of industrialised countries, because of its continuous, long-term policy of water privatisation,' said Noyola. By 2012, Chile will be treating 100 percent of its wastewater, he said.

In contrast, the Dominican Republic and Colombia only treat 25 percent of sewage, while in Guatemala just 10 or 15 percent is treated.

Noyola said there are basically three technologies used to treat wastewater in the region: stabilisation lagoons or ponds; activated sludge; and anaerobic reactors.

Stabilisation lagoons - large tanks lined with cement, clay or plastic sheeting to prevent water seeping into the ground - 'have the advantage of very low operating costs, although their large size means they can only be installed on flat land,' he said.

The activated sludge process has a more compact layout, but requires equipment like pumps and motors and more technology, and electrical energy use pushes up costs. The method 'provides consistently good quality reclaimed water,' he said.

Anaerobic reactors, or digesters, are compact airtight containers. 'Their advantage is the very low operational costs,' but the process produces methane gas instead of organic matter, as the other treatments do. 'The disadvantage is that water quality is lower than for the activated sludge system, and a post-treatment stage of purification is required,' he said.

Noyola agrees with Ubal that no technology for wastewater treatment is entirely sustainable and eco-friendly.

'Some are 'greener' than others. Every process that uses energy will have environmental consequences, however small. The challenge is to minimise impacts,' he said.

In Noyola's view, no single technology is suitable for wastewater treatment throughout Latin America, because of 'the wide range of treatment plant sizes, as well as the geographical diversity of the region.'

When sewage is treated, energy is consumed, and this adds to the burden of greenhouse gas emissions, he said.

'Methane gas is dangerous and has a huge impact on climate change. If it is not captured, but allowed to escape into the atmosphere, it makes a very negative contribution. Pollution is shifted from water to the atmosphere, so one problem is merely exchanged for another,' Noyola stressed.

The pioneering study that Noyola is coordinating aims to provide an up-to-date, representative analysis of wastewater treatment in Latin American cities and produce a guide containing this information for municipal governments.

'We will write a guide with recommendations that will allow decision-makers to select the technology that is best suited to their requirements. Some countries have produced recommendations, but they are mainly technical and economic. We want to include environmental assessments,' he said.

According to Noyola, water treatment plants have their share of negative impacts that need to be minimised by selecting the most sustainable technology.

© Inter Press Service (2011) — All Rights ReservedOriginal source: Inter Press Service