Building a pilot plant to biologically remove manganese from groundwater in Costa Rica

Manganese present in groundwater can cause health problems and sanitary issues, therefore the World Health Organization (WHO) has set the limit of manganese concentration to < 0.1 mg/L. Currently manganese is frequently removed using a strong oxidant, such as chlorine. Chlorine however has the disadvantage of the by-product thriholamethanes and it is expensive. A biological method seems to be a good alternative.

The aim of my study was to design and build a pilot plant that biologically removes manganese from groundwater. The pilot plant was built in La Hacienda, Costa Rica. The biological method uses oxygen and a manganese oxidation bacteria as a catalysing agent. This bacteria is already present in the groundwater. The bacteria can grow in the filter media, but it has a long start-up period. Therefore a recirculation start-up seemed like a good alternative to reduce the start-up time and the reduction of water consumption during start- up.

In collaboration with Technologico de Costa Rica in Cartago a pilot plant was designed and built. The design of the pilot plant consists of two duplicated filter columns of pumice and a recirculation tank. During the design of the pilot system it was a consideration between availability, necessity and budget. The pilot system needed to be connected to the water well and monitored. While the pilot system was monitored the optimal conditions for the bacteria had to be kept in mind.

Cartago was a great experience. I lived in a family’s home for two months and learned a lot about their culture, traditions and some Spanish. Doing research at a university in a different county was challenging. I learned a lot about the process of building a pilot system and about water treatment for potable water. I would like to thank Dr. Luis Guillermo Romero Esquivel and Jose Andres Araya Obando from Technologico de Costa Rica and Prof.Dr. Luuk Rietveld from Delft University of Technology for the unforgettable experience and opportunity of doing my thesis abroad.

Malou van Schaijk 

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