Stabilization ponds are a technology that has been used for over 3,000 years to treat wastewater, yet they are still one of the most commonly-used wastewater treatment technologies today. They utilize natural sunlight and indigenous communities of bacteria and algae to achieve treatment objectives, and have very low carbon footprints relative to mechanized wastewater treatment technologies.
If designed, operated, and maintained correctly, can produce an effluent that is suitable for irrigation and has nutrients in forms that are readily available for crop uptake. The operation and maintenance of stabilization ponds is very simple, but the mechanisms contributing to the removal of pathogens and other contaminants are incredibly complex, and some are still poorly understood.
Over the past several years, USF Reclaim, in collaboration with the Universidad Tecnológica Boliviana (UTB) and the Centro de Aguas y Saneamiento Ambiental (CASA) at the Universidad Mayor de San Simon, has been studying the performance and impact of stabilization pond systems in Bolivia. This work helps local decision-makers, planners, and engineers evaluate the many trade-offs associated with the safe recovery of water, energy, and nutrient resources from domestic wastewater. Here are three of USF Reclaim’s most recent publications on wastewater treatment pond technologies.
Matthew E. Verbyla, Stewart M. Oakley, Louis A. Lizima, Jie Zhang, Mercedes Iriarte, Andres E. Tejada-Martinez and James R. Mihelcic
Water Science & Technology, available online, October 2013 (in press).
Abstract: The objective of this study is to compare the removal of Taenia eggs to the removal of Ascaris eggs in a wastewater stabilization pond system consisting of three ponds in series, where the hydraulic residence time distribution has been characterized via a tracer study supported by computational fluid dynamics modeling. Despite a theoretical hydraulic retention time of 30 days, the peak dye concentration was measured in the effluent of the first pond after only 26 hours. The smaller-sized Taenia eggs were detected in higher concentrations than Ascaris eggs in the raw wastewater. Ascaris eggs were not detected in the pond system effluent, but 45 Taenia eggs per liter were detected in the system effluent. If some of these eggs were of the species Taenia solium, and if the treated wastewater were used for the irrigation of crops for human consumption, farmers and consumers could potentially be at risk for neurocysticercosis. Thus, limits for Taenia eggs in irrigation water should be established, and precautions should be taken in regions where pig taeniasis (T. solium) is endemic. The results of this study indicate that the theoretical hydraulic retention time of a pond is not always a good surrogate for helminth egg removal.
Available online at http://www.iwaponline.com/wst/up/wst2013556.htm
Pablo K. Cornejo, Qiong Zhang, and James R. Mihelcic
Journal of Environmental Management, December 2013, Volume 131, pages 7 – 15.
Abstract: Despite concerns of sanitation provision, water scarcity, climate change, and resource depletion, limited research has been conducted to assess the environmental impact of wastewater treatment and resource recovery strategies to improve access to sanitation and resource utilization in developing world settings. Accordingly, the goal of this study is to evaluate the potential benefits of mitigating the environmental impact of two small community-managed wastewater treatment systems in rural Bolivia using resource recovery (i.e., water reuse and energy recovery). Life Cycle Assessment (LCA) is used to estimate the embodied energy, carbon footprint, and eutrophication potential of these systems under existing and resource recovery conditions. Two distinct technologies are analyzed: (1) an upflow anaerobic sludge blanket reactor (UASB) followed by two maturation ponds in series (UASB-Pond system) and (2) a facultative pond followed by two maturation ponds in series (3-Pond system). For the existing systems, bathroom and collection infrastructure had a higher energy intensity than the treatment processes, whereas direct methane emissions from treatment were the primary contributors to the carbon footprint. Taking advantage of reclaimed water was found to greatly reduce the eutrophication potential for both systems, in which the reduction increases proportionally to the percentage of water that is reclaimed. Energy recovery from the UASB-Pond system provided a 19% reduction in embodied energy and a 57% reduction in carbon footprint. Combining water reuse and energy recovery for the UASB-Pond system reduced the eutrophication potential, embodied energy and carbon footprint simultaneously. This highlights the benefits of integrated resource recovery.
Available online at http://www.sciencedirect.com/science/article/pii/S0301479713006439#
Wastewater Infrastructure for Small Cities in an Urbanizing World: Integrating Protection of Human Health and the Environment with Resource Recovery and Food Security
Matthew E. Verbyla, Stewart M. Oakley and James R. Mihelcic
Environmental Science & Technology, March 2013, Volume 47(8), pages 3598 – 3605.
Abstract: The majority of population growth in developing countries will occur in small cities closely linked to agricultural zones, with poor access to water and sanitation. Wastewater management priorities in these regions will be different from those in larger cities and developed countries. Two wastewater treatment systems in Bolivia, one with an upflow anaerobic sludge blanket (UASB) reactor and polishing ponds, the other with three stabilization ponds, are assessed to determine their resource recovery potential. The UASB reactor produces biogas with 500–650 MJ per day. In six months, both systems discharge wastewater with the same mass of nutrients as fertilizers used to produce crops containing 10–75 days’ worth of the recommended food energy intake for each person using the system. Both systems also discharge detectable levels of helminth eggs, Giardiacysts, and Cryptosporidium oocysts, but the UASB reactor system discharges higher concentrations, implying limited reuse potential. From a regional management standpoint, small cities should not expend resources to treat wastewater to levels suitable for discharge into surface waters. Rather, they should focus on removing pathogens to reclaim water and nutrients. Biogas recovery may be a priority that should be subservient to water and nutrient recovery in these settings.
Available online at http://pubs.acs.org/doi/abs/10.1021/es3050955
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