Browsing by Autor "Alvaro Mercado"

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Ammonia Inactivation of Ascaris Ova in Ecological Compost by Using Urine and Ash
(American Society for Microbiology, 2012) James W. McKinley; Rebecca E. Parzen; Alvaro Mercado
Viable ova of Ascaris lumbricoides, an indicator organism for pathogens, are frequently found in feces-derived compost produced from ecological toilets, demonstrating that threshold levels of time, temperature, pH, and moisture content for pathogen inactivation are not routinely met. Previous studies have determined that NH(3) has ovicidal properties for pathogens, including Ascaris ova. This research attempted to achieve Ascaris inactivation via NH(3) under environmental conditions commonly found in ecological toilets and using materials universally available in an ecological sanitation setting, including compost (feces and sawdust), urine, and ash. Compost mixed with stored urine and ash produced the most rapid inactivation, with significant inactivation observed after 2 weeks and with a time to 99% ovum inactivation (T(99)) of 8 weeks. Compost mixed with fresh urine and ash achieved a T(99) of 15 weeks, after a 4-week lag phase. Both matrices had relatively high total-ammonia concentrations and pH values of >9.24 (pK(a) of ammonia). In compost mixed with ash only, and in compost mixed with fresh urine only, inactivation was observed after an 11-week lag phase. These matrices contained NH(3) concentrations of 164 to 173 and 102 to 277 mg/liter, respectively, when inactivation occurred, which was below the previously hypothesized threshold for inactivation (280 mg/liter), suggesting that a lower threshold NH(3) concentration may be possible with a longer contact time. Other significant results include the hydrolysis of urea to ammonia between pH values of 10.4 and 11.6, above the literature threshold pH of 10.
Bactericidal Effect of Solar Water Disinfection under Real Sunlight Conditions
(American Society for Microbiology, 2008) M. Boyle; C. Sichel; Pilar Fernández‐Ibañez; G. B. Arias-Quiroz; M. Iriarte-Puña; Alvaro Mercado; Eunice Ubomba‐Jaswa; Kevin G. McGuigan
Batch solar disinfection (SODIS) inactivation kinetics are reported for suspensions in water of Campylobacter jejuni, Yersinia enterocolitica, enteropathogenic Escherichia coli, Staphylococcus epidermidis, and endospores of Bacillus subtilis, exposed to strong natural sunlight in Spain and Bolivia. The exposure time required for complete inactivation (at least 4-log-unit reduction and below the limit of detection, 17 CFU/ml) under conditions of strong natural sunlight (maximum global irradiance, approximately 1,050 W m(-2) +/- 10 W m(-2)) was as follows: C. jejuni, 20 min; S. epidermidis, 45 min; enteropathogenic E. coli, 90 min; Y. enterocolitica, 150 min. Following incomplete inactivation of B. subtilis endospores after the first day, reexposure of these samples on the following day found that 4% (standard error, 3%) of the endospores remained viable after a cumulative exposure time of 16 h of strong natural sunlight. SODIS is shown to be effective against the vegetative cells of a number of emerging waterborne pathogens; however, bacterial species which are spore forming may survive this intervention process.
EVAS - a practical tool to assess the sustainability of small wastewater treatment systems in low and lower-middle-income countries
(Elsevier BV, 2020) Claudia Cossio; Jennifer McConville; Ann E. Mattsson; Alvaro Mercado; Jenny Norrman
Small wastewater treatment systems (WWTSs) in low and lower-middle income countries still face challenges to achieve optimal performance and acceptable levels of sustainability. Thus, a practical tool, easy to apply by locals, to diagnose the actual status of WWTSs is required in order to identify weak areas for further improvement. This study presents a sustainability assessment tool, EVAS (EVAluación de Sostenibilidad: EVAluation of Sustainability), for small WWTSs in low and lower-middle income countries. The EVAS tool is developed based on a set of contextualized sustainability indicators and sub-indicators in five dimensions (technical, environmental, social, economic, institutional). Each indicator or sub-indicator is broken down into factors, each associated with specific targets to fulfil, and scored using a traffic light scale (0 to 4) indicating unsustainable-low-medium to high levels of sustainability. The tool was developed taking into consideration that local data may sometimes be incomplete and encourages the collection and monitoring of relevant data. The assessment results support local managers or other stakeholders responsible for wastewater management with the identification of weaknesses that need to be addressed. The tool was tested using two case studies involving WWTSs in Bolivia. One WWTS received a medium sustainability rating, whereas the other system received a low sustainability rating, which indicates that several improvements are required in all sustainability dimensions. Stakeholders in the case studies found the tool useful, and suggested ways in which it could be further improved. It is expected that the application of this tool can contribute to raising the sustainability level of small WWTSs in low and lower-middle-income countries.
Frecuencia de Anaplasma marginale (Theiler 1910) y Babesia sp en bovino mestizo Cebú, en el Municipio de Ixiamas provincia Abel Iturralde Departamento de La Paz, Bolivia
(Selva Andina Research Society, 2011) Alvaro Mercado; Manuel Gregorio Loza-Murguia; Rodrigo Aliaga; Jaime Cahuana
The present work one carries out in the Municipality of Ixiamas County Abel Iturralde of the department of Peace-Bolivia, between May and August of 2010.The objective was to determine the presence of Anaplama sp and Babesia sp, through sanguine smear, they took 160 samples of blood, 40 bovine of the four areas they have been evaluated.The results indicate the presence of Anaplasma sp 6,90%, 6,20% in females and 9,70% in males, this represents 2,50% for the area TO, 5,00% area B, 17,50% area C and 2,50% area D. According to the category 12,50% in calves, 0,00% in torillos, 4,80% in bulls, 6,20% in cows and 14,30% in heifers.The presence of Babesia sp 3,13%, with relationship to the sex 3,10% in females and 3,22% in males, being observed 2,50% in the area TO, 5,00% in the area B, 5,00% in the area C and 0,00% in the area D, according to the category 0,00% in calves, torillos 4,80% bulls, 2,73% vacates and 7,14% in heifers.
Impact of climate and bulking materials on characteristics of compost from ecological toilets
(IWA Publishing, 2012) James W. McKinley; Rebecca E. Parzen; Alvaro Mercado
Urine-diversion dehydration toilets (UDDT) are common throughout the developing world, and the toilet product is widely used as compost. There is no comprehensive research to date that characterizes the compost to determine its quality, extent of pathogen inactivation, and the effects of climate and bulking materials on the compost. Compost was collected from 45 UDDT in Bolivia and analyzed for physical, chemical, and biological parameters. Eighty percent and 56% of samples did not meet acceptable compost guidelines for moisture content and pH, respectively, indicating desiccation was the dominant process in UDDT. Bulking materials significantly impacted compost characteristics in terms of pH, carbon, carbon-to-nitrogen ratio, and carbon stability (P &lt; 0.05). Composts with ash exhibited, on average, low carbon concentrations (4.9%) and high pH values (9.7), which can be harmful to plants and composting microorganisms. Composts with sawdust exhibited, on average, high carbon concentrations (40.0%) and carbon-to-nitrogen ratios (31.0). Climate had no significant impact on chemical characteristics, however composts from humid regions had significantly higher moisture contents (34.4%) than those from arid climates (24.8%) (P &lt; 0.05). Viable Ascaris lumbricoides ova were identified in 31% of samples, including samples with high pH, low moisture contents, and long storage times.
Impact of treatment plant management on human health and ecological risks from wastewater irrigation in developing countries – case studies from Cochabamba, Bolivia
(Taylor & Francis, 2019) Claudia Cossio; Luis Fernando Perez-Mercado; Jenny Norrman; Sahar Dalahmeh; Björn Vinnerås; Alvaro Mercado; Jennifer McConville
Wastewater irrigation is a common practice in developing countries due to water scarcity and increasing demand for food production. However, there are health risks and ecological risks associated with this practice. Small-scale wastewater treatment plants (WWTPs) intend to decrease these risks but still face management challenges. This study assessed how the management status of five small-scale WWTPs in Cochabamba, Bolivia affects health risks associated with consumption of lettuce and ecological risks due to the accumulation of nutrients in the soil for lettuce and maize crops. Risk simulations for three wastewater irrigation scenarios were: raw wastewater, actual effluent and expected effluent. Results showed that weak O&M practices can increase risk outcomes to higher levels than irrigating with raw wastewater. Improving O&M to achieve optimal functioning of small-scale WWTPs can reduce human health risks and ecological risks up to 2 log10 DALY person-1 year-1 and to 2 log10 kg nitrogen ha-1 accumulated in soil, respectively.
Indicators for sustainability assessment of small-scale wastewater treatment plants in low and lower-middle income countries
(Elsevier BV, 2020) Claudia Cossio; Jenny Norrman; Jennifer McConville; Alvaro Mercado; Sébastien Rauch
Wastewater treatment in low and lower-middle income countries is often limited by lack of local technical expertise, institutional capacity, and financial resources, making it challenging to reach SDG6-target 6.3, i.e. halving the proportion of untreated wastewater. Several studies suggest sets of sustainability indicators for assessing the planning and/or operation of WWTPs. However, existing standard indicators are typically focused on the context of high and upper-middle income countries, whereas low and lower-middle income countries face other types of issues. The development of a contextualized set of relevant and effective sustainability indicators to support the planning and/or operation of small-scale WWTPs in low and lower-middle income countries is crucial. This study develops a contextualized set of sustainability indicators for small-scale wastewater treatment plants in Bolivia, which is classified as a lower-middle income country. Indicators were identified using a literature review combined with empirical studies using focus groups with managers and operators, as well as, workshops with experts. The aim of the focus groups and workshops was to acquire an understanding of the local context and identify relevant sustainability indicators. The practical investigation took place at five sites in Cochabamba, Bolivia. The results suggest that sustainability assessment of WWTPs in low and lower-middle income countries should emphasize the institutional dimension (e.g. Institutional capacity, Interactions, and Information) and the technical dimension (e.g. Sewage network functionality and Expertise) alongside indicators in the social, economic and environmental dimensions.
Managing Microbial Risks from Indirect Wastewater Reuse for Irrigation in Urbanizing Watersheds
(American Chemical Society, 2016) Matthew E. Verbyla; Erin M. Symonds; Ram C. Kafle; Maryann R. Cairns; Mercedes Iriarte; Alvaro Mercado; Olver Coronado; Mya Breitbart; Carmen Ledo; James R. Mihelcic
Limited supply of clean water in urbanizing watersheds creates challenges for safely sustaining irrigated agriculture and global food security. On-farm interventions, such as riverbank filtration (RBF), are used in developing countries to treat irrigation water from rivers with extensive fecal contamination. Using a Bayesian approach incorporating ethnographic data and pathogen measurements, quantitative microbial risk assessment (QMRA) methods were employed to assess the impact of RBF on consumer health burdens for Giardia, Cryptosporidium, rotavirus, norovirus, and adenovirus infections resulting from indirect wastewater reuse, with lettuce irrigation in Bolivia as a model system. Concentrations of the microbial source tracking markers pepper mild mottle virus and HF183 Bacteroides were respectively 2.9 and 5.5 log10 units lower in RBF-treated water than in the river water. Consumption of lettuce irrigated with river water caused an estimated median health burden that represents 37% of Bolivia's overall diarrheal disease burden, but RBF resulted in an estimated health burden that is only 1.1% of this overall diarrheal disease burden. Variability and uncertainty associated with environmental and cultural factors affecting exposure correlated more with QMRA-predicted health outcomes than factors related to disease vulnerability. Policies governing simple on-farm interventions like RBF can be intermediary solutions for communities in urbanizing watersheds that currently lack wastewater treatment.
Pathogens and fecal indicators in waste stabilization pond systems with direct reuse for irrigation: Fate and transport in water, soil and crops
(Elsevier BV, 2016) Matthew E. Verbyla; Mercedes Iriarte; Alvaro Mercado; Olver Coronado; Mariela De La Cruz Almanza; James R. Mihelcic
Wastewater management in small towns – understanding the failure of small treatment plants in Bolivia
(Taylor & Francis, 2017) Claudia Cossio; Jennifer McConville; Sébastien Rauch; Britt‐Marie Wilén; Sahar Dalahmeh; Alvaro Mercado; Ana Malvis Romero
Wastewater management in developing countries is a challenge, especially in small towns with rapid population growth. This study aims at assessing the performance and management of five treatment plants (TPs) in rural areas of Cochabamba, Bolivia. Pollutants' concentrations, wastewater flows, hydraulic and organic loads and hydraulic retention times were determined in three small treatment plants (2000-10,000 population equivalent [p.e.]; flow > 432 m3/d) and two very small treatment plants (<2000 p.e.; flow < 432 m3/d). The performance assessment was based on operational parameters, treatment efficiency and effluent quality. Management data were collected through semi-structured interviews with managers of local water associations. The results support that the poor performance of the TPs is due to lack of operational expertise and financial resources for adequate operation and maintenance (O&M). Additionally, effective treatment was affected by the type of technology used and whether the plant design included plans for O&M with available resources. This study contributes to a better understanding of actual operating conditions of wastewater TPs in small towns, thus providing needed information regarding technology selection, design, implementation and operation.