Anaerobic Treatment of Coffee Wastewater: A study on monitoring and implementation of biogas at Finca el Socorro, Matagalpa, Nicaragua

Anaerobic Treatment of Coffee Wastewater: A study on monitoring and implementation of biogas at Finca el Socorro, Matagalpa, Nicaragua

Schutgens, G.

Van Lier, J.B. (mentor)

Civil Engineering and Geosciences

Watermanagement

Sanitary Engineering

2011-10-31

In order to achieve the Millennium development goals of the UN, different initiatives have been established worldwide. One of these initiatives has been developed in Matagalpa, Nicaragua. Through the program Agua para Todos – Agua para Siempre different institutions work together, the common goal being to provide safe drinking water and sanitation to a large number of the people of Matagalpa and the surrounding areas. One of the ways in which this goal is pursued is by installing wastewater treatment systems for demonstration purposes in order to reduce the contamination produced by the coffee processing industry. This industry is, at present, the major cause of pollution of open water sources in the Matagalpa province. Therefore, a new hybrid anaerobic wastewater treatment system has been developed: an improved anaerobic lagoon (LAM, because of the Spanish acronym). One of the main objectives of this report is to throw light on the way in which such a system works and to also recommend to coffee farmers the set up size that is recommendable when installing a LAM system. In addition, the possibilities for locally integrating the use of biogas produced in the LAM system is a question that is discussed in this thesis. For this purpose, a LAM system has been installed in a medium?sized coffee farm called El Socorro. In the period between November 2009 and January 2010, measurements were made of key parameters in El Socorro which indicate the efficiency and working of the LAM system, together with pre?treatment and post?treatment. In previous harvest seasons other students have conducted work on the characterization of coffee wastewater and this data, together with the data obtained during the last harvest season will help in providing answers to the objectives stated in the previous paragraph. During the fieldwork unforeseen restrictions were encountered which were ultimately responsible for reducing the quantity of data below that which was anticipated. However, with the information gathered, it was obvious that in the last harvest season the lack of lime for neutralizing the coffee wastewater was a serious problem that inhibited the proper working of the biomass in the LAM system. Therefore, no biogas production took place at all. The biogas production, which should have been measured during the fieldwork, could not be measured due to prolonged delays. This is why many theoretical calculations and assumptions need to be made in order to come up answers to the questions posed by this thesis. Measurements of wastewater revealed an average pH value of 4.9. In order to elevate this value, a base is needed which elevates the alkalinity of the wastewater. In this report two bases are studied: calcium hydroxide and calcium carbonate. From these two bases the conclusion is drawn that calcium carbonate, even when it has to be applied in larger quantities, has the preference due to the substantial difference in costs (US$ 0,49 cheaper per produced quintal oro). The estimated biogas production, which to a large extent had been based on assumptions concerning coffee wastewater, is much lower when measured values are used to calculate methane production. Therefore, instead of the anticipated 17.5 m3/d of CH4, only 2.4 m3/d could have been produced in the last harvest season. This production is not enough to run engines and can only at best be used to cook. If this application is not possible then the only option left is to flare the biogas. At the end of the report a graph is presented in which it is shown how different coffee farmers can get an impression of how likely the successful implementation a LAM system in their coffee farms is, which not only prevents fines (by treating the wastewater), but also renders profit from biogas production in larger quantities.

anaerobic digestion
coffee wastewater
Nicaragua

http://resolver.tudelft.nl/uuid:b476b125-d4ce-4e48-b665-40bdd247c11b

Student theses

master thesis

(c) 2011 Schutgens, G.