El tratamiento de las aguas residuales municipales en las comunidades rurales de México

Recently, efforts have been made to increase municipal wastewater treatment plants in Mexico; however, efforts have focused mainly on urban communities. Municipal wastewater can be treated with different technologies ranging from expensive and highly mechanized equipment to relatively simple and low-cost ecological treatment systems. This paper's aim is to research the current status of municipal wastewater treatment in Mexican rural communities, discussing the main barriers and challenges to overcome in order to increase coverage of treatment plants in these communities. In most states, municipal wastewater treatment plants coverage in small rural communities, with less than 2 500 inhabitants have not been taken care of, especially those 47 233 villages with populations ranging from 100 to 2 499 inhabitants, where it is feasible to install treatment plants. In rural areas, the priority has been given to drinking water supply and sewage, increasing the volumes of wastewater collected. The treatment systems that are most commonly used for the small rural communities with municipal wastewater treatment plants are stabilization ponds and constructed wetlands, followed by sedimentation or septic tanks. Stabilization ponds are quite common in Mexico, whereas constructed wetlands have faced dome barriers preventing their implementationon a larger scale. Some of these obstacles are, deficient knowledge about this technology, lack of basic, easily designed manuals for potential users, etcRecientemente se han hecho esfuerzos, por incrementar la cobertura de plantas de tratamiento de aguas residuales municipales en México; sin embargo, estos esfuerzos se han enfocado principalmente en las comunidades urbanas. Para el tratamiento de aguas residuales municipales, existen diversas tecnologías que van desde las altamente mecanizadas y costosas, hasta las tecnologías relativamente simples y de bajo costo. El objetivo de este trabajo, es investigar el estado actual del tratamiento de las aguas residuales municipales en las comunidades rurales en México, así como discutir cuáles son las barreras y retos que se deben superar, para incrementar la cobertura de plantas de tratamiento. En la mayoría de los estados, se está dejando de atender las pequeñas comunidades rurales de menos de 2 500 habitantes, en especial aquellas 47 233 localidades con 100-2 499 habitantes, en donde es factible instalar plantas de tratamiento. En las zonas rurales se ha dado prioridad a la cobertura de agua potable y los servicios de alcantarillado, lo que ha incrementado el volumen de aguas residuales municipales. Los sistemas de tratamiento que más se emplean en las comunidades rurales, que cuentan con plantas de tratamiento de aguas residuales municipales, son las lagunas de estabilización y los humedales artificiales precedidos de sedimentación o fosa séptica. Mientras que las lagunas de estabilización son bastante comunes en México, los humedales artificiales enfrentan algunas barreras, que han evitado su implementación en forma masiva; por el poco conocimiento de esta tecnología y la falta de diseños accesibles a los usuarios directos

Partially Saturated Vertical Constructed Wetlands and Free-Flow Vertical Constructed Wetlands for Pilot-Scale Municipal/Swine Wastewater Treatment Using <i>Heliconia latispatha</i>

Partially saturated vertical constructed wetlands (PSV-CWs) and free-flow vertical constructed wetlands (FFV-CWS) are treatment systems for which there is limited information on their operation in tropical climates and even scarcer information on their use for municipal/swine wastewater treatment. In this work, the removal of pollutants from municipal wastewater mixed with swine effluents was evaluated using PSV-CWs and FFV-CWs, at pilot scale, with the presence and absence of vegetation in a tropical climate. Six vertical flow CWs made up of polyvinyl chloride (1 m high and 0.5 m in diameter) were used; three were operated with free-flow conditions and three with partially saturated conditions. In each type of configuration, two reactors were planted with an individual of Heliconia latispatha, and one remained without vegetation. They were fed with municipal wastewater mixed with 50% of swine wastewater. Their ability to remove COD, TSS, TP, TN, N-NH4, and N-NO3 and plant development were evaluated. Heliconia latispatha registered better results of adaptation and vegetative development in the PSV-CWs in comparison with FFV-CWs measured as total biomass (5697.1 g/m2 and 5095.7 g/m2, respectively). PSV-CWs were slightly better for TSS elimination (4.21%), while FFV-CWs presented a better performance for TN removal (3.76%), N-NH4 (3.94%) and N-NO3 (4.76%) in the systems with vegetation; no significant difference (p ˃ 0.05) was found between the two types of CWs for the removal of COD and TP. However, significant differences (p ˂ 0.05) were found between the systems with vegetation and those without vegetation in both configurations. These results demonstrate that PSV-CWs represent a better option for the treatment of municipal/swine wastewater since their efficiency was slightly higher than, or similar to that of, FFV-CWs and allowed a better development of H. latispatha

Remediation of River Water Contaminated with Whey Using Horizontal Subsurface Flow Constructed Wetlands with Ornamental Plants in a Tropical Environment

The aim of this research was to evaluate the efficiency of horizontal subsurface flow-constructed wetlands (HSSFWs) planted with Hippeastrum striatum and Heliconia lastisphata for the treatment of contaminated river waters by wastewater from the dairy industry (WDI) and domestic wastewater in tropical climates over a study period of 136 days. Cell with a real volume of 780,000 mL and a flow rate of 1.805 mL s−1. The hydraulic retention time was determined to be 5 days. 12 individuals of Hippeastrum striatum were planted at a distance of 20 cm from each other in one cell, while in another cell, 12 individuals of Heliconia spp. were planted. An adaptation period was determined for both species. Subsequently, the experiment was started, and the elimination percentages obtained were as follows: COD: 67.94 ± 1.39%, 63.17 ± 2.63%; TSS: 56.49 ± 5.73%, 48.78 ± 5.87%; N-NH4: 51.06 ± 2.16%, 50.80 ± 1.91%; TN: 44.36 ± 5.73%, 30.59 ± 5.87%; TP: 47.00 ± 5.32%, 35.57 ± 4.06%; DO: 50.23 ± 1.61%, 47.74 ± 1.34%; and pH: 6.81 ± 0.07, 6.52 ± 0.1, for Heliconia lastisphata and Hippeastrum striatum, respectively. These results demonstrate that both macrophyte species can be used for the treatment of wastewater from the dairy industry using HSSFWs; cheese factories could be involved in the development of constructed wetland systems to reduce the environmental impact of the industry

Optimization of DNA isolation and PCR protocol for analysis and evaluation of genetic diversity of the medicinal plant, Anemopsis californica using RAPD

Anemopsis californica is a perennial herbaceous plant that has been utilized as a medicinal plant for the treatment of various diseases. The present work was carried out with the objective of optimizing a method of extraction of the genomic DNA of A. californica and a PCR protocol and later to evaluate the existing genetic diversity among the genotypes deriving from different origins. For DNA extraction, we tested four procedures: with the CTA B-2 protocol, we obtained the highest yield (61.5±2.2 μg DNA/g of leaf tissues) and the best quality (A260/280 1.83±0.022). To estimate genetic variability, we utilized the randomly amplified polymorphism DNA (RAPD) technique, employing 20 oligonucleotides, of which only 18 generated reproducible banding patterns, producing 123 polymorphic bands generated, thus obtaining a polymorphism rate of 93.93% among the genotypes analyzed. The Jaccard similarity coefficient generated a variation ranging from 0.325–0.921, indicating a high level of genetic variation among the studied genotypes. An Unweighted pair-group method with arithmetic mean (UPGMA) group analysis indicated six distinct groups. The present optimized method for DNA isolation and RAPD protocol may serve as an efficient tool for further molecular studies