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A low-priced water reuse process that also delivers renewable energy in rural areas

Christian Borja-Vega's picture

What do Yucatan (Mexico), Michoacan (Mexico), Karur (India), and Jan Kempdorp (South Africa) have in common? These are all places with successful stories of implementing Anaerobic Digestion (AD) for wastewater treatment. But what is AD? What are the benefits?  

AD systems are installed for many different purposes, such as a waste treatment step, a means to reduce odours, a source of additional revenues, or a way to improve public image. The AD treats water and waste, reducing adverse environmental impacts. Through AD, two main by-products can be obtained: biogas—that can be used as a fuel, and sludge—that can be used as a soil amender for improve crops. These AD “by-products” are important in the context of mitigating the impacts of climate change, where environmental co-benefits come from efficient use of “by-products”. For instance, livestock enteric fermentation, livestock waste management, rice cultivation, and agricultural waste burning are all sources of methane emissions, representing between 7 and 10 percent of global methane emissions. AD not only treats water through an environmentally sustainable approach, but also contributes to produce high rates of methane for recovery and further utilization.

Source: The Global Partnership on Output-based Aid, 2015. Note Number 8. Biogas Support Program in Nepal.

Investing in wastewater in Latin America can pay off

Diego Juan Rodriguez's picture
We are all too familiar with these figures: on average, only 50% of the population in Latin America is connected to sewerage and 30% of those households receive any treatment. These figures are not new. The region has been lagging in the levels of wastewater treatment for decades, which is unacceptable considering its high levels of urbanization and income levels.

The region is also not homogenous. There is a large disparity in the levels of treatment per country: we see countries like Chile, which treats 90% of its wastewater, and countries like Costa Rica, which treats approximately 4% of its wastewater.
The Deodoro wastewater treatment plant in Rio the Janeiro, Brazil.

Ahead of World Water Day: Let’s Talk about … Energy?

William Rex's picture

For the last six years, a power plant in San Luis Potosi, Mexico has bought water from a nearby wastewater treatment plant to use in its cooling towers (instead of using freshwater). This operation, Project Tenorio, a public-private partnership, continues today and has already resulted in the reduction of groundwater extraction of at least 48 million cubic meters (equivalent to 19,000 Olympic size pools) and increased aquifer sustainability.
This is a good example of the water and energy nexus in practice: the wastewater treatment plant covers almost all of its operating costs from this additional revenue stream and the power plant gets a more reliable water source that is also 33% cheaper than groundwater in that area.  

Treated wastewater has been used to reduce the water requirements of power plants in several other countries as well, as water supply becomes more variable or disappears. In the US, for example, around 50 power plants are using treated wastewater for cooling in order to adapt to water shortages. However, innovative integrated approaches like these are still more of an exception than the norm.