Access to clean water a big problem in Latinoamerica(2)

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

Stabilization 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 minimize 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 minimized by selecting the most sustainable technology.