Graduation Year

2012

Document Type

Thesis

Degree

M.S.E.V.

Degree Granting Department

Civil and Environmental Engineering

Major Professor

James R. Mihelcic

Keywords

developing countries, lagoons, sanitation, water reuse, WHO guidelines

Abstract

Extreme hunger, malnutrition, and the lack of access to sanitation are among the most pressing development challenges, but the world is not on track to meet the targets that have been established by the Millennium Development Goals. The integration of wastewater treatment and food production systems allows for the recovery of resources from wastewater, and can provide an important solution to meet the sanitation needs of growing urban populations and provide periurban farmers with a consistent supply of water and nutrients. Stabilization ponds have been long considered to be an appropriate technology for wastewater reuse systems in developing countries, but advanced anaerobic treatment technologies, such as upflow anaerobic sludge blanket (UASB) reactors, are also becoming common. The objective of this study is to evaluate the reuse potential of wastewater for irrigation from two community-managed treatment systems in Bolivia: one consisting of three stabilization ponds in series (three-pond system) and the other consisting of a UASB reactor and two stabilization ponds in series (UASB-pond system).

Specifically, the removal of helminth eggs and thermotolerant coliform bacteria is measured in both systems and evaluated with respect to the World Health Organization (WHO) guidelines for the safe use of wastewater in agriculture, which are based on health targets. Results indicate that both systems provide good removal of conventional water quality parameters but poor removal of nutrients, discharging effluents with 37 to 54 mg/L of total nitrogen and 5.7 to 9.4 mg/L of total phosphorus. The three-pond system provided >92% removal of helminth eggs and 3.4-log removal of thermotolerant coliforms, and no geohelminth eggs were detected in the system effluents. However, Ascaris eggs were detected in the effluents of the UASB-pond system and the overall removal of thermotolerant coliforms was only 2.3 log units. Viability estimates based on the use of a vital stain indicate that eggs detected in pond effluents are less likely to be viable than eggs detected in the raw wastewater, in the sludge, or in the effluent of the UASB reactor. Sludge samples from the facultative pond in the three-pond system had higher concentrations of helminth eggs than sludge samples from the UASB reactor.

Based on these results, the effluents from the three-pond system can be reused for irrigating any crop with the exception of root crops and low-growing crops that can be consumed raw (i.e. onions and strawberries). Effluents from the three-pond system may be used to irrigate salad crops or high-growing crops that are consumed raw, but additional public health interventions must be implemented throughout the food production process to meet WHO recommendations for protecting the health of farmers and consumers. The effluents from the UASB-pond system should not be reused unless improvements to the system increase its pathogen removal efficiency. The results from this study indicate that a system consisting of stabilization ponds in series may produce a higher quality effluent that is more suitable for wastewater irrigation than a system with a UASB reactor.

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