Removing Organic Matter and Nutrients from Pig Farm Wastewater with a Constructed Wetland System.

Pollutants from pig farms in Mexico have caused problems in many surface water reservoirs. Growing concern has driven the search for low-cost wastewater treatment solutions. The objective of this research was to evaluate the potential of an in-series constructed wetland to remove nutrients from wastewater from a pig farm. The wetland system had a horizontal flow that consisted of three cells, the first a surface water wetland, the second a sedimentation cell, and the third a subsurface flow wetland. The vegetation used was Thypa sp. and Scirpus sp. A mix of soil with red volcanic rock (10⁻30 mm diameter) and yellow sand (2⁻8 mm diameter) was used as a substrate for the vegetation. The experiments were carried out in duplicate. Water samples were collected at the inflow and outflow of the cells. Two hydraulic retention times (HRT) (5 and 10 days) and three treatments were evaluated: 400, 800, and 1200 mg·L−1 of chemical oxygen demand (COD) concentration. Data was collected in situ for temperature, pH, dissolved oxygen (DO), electrical conductivity (EC), and total dissolved solids (TDS). COD, total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3⁻N), and total phosphorous (TP) were analyzed in the laboratory. The results showed that the in-series constructed wetland is a feasible system for nutrient pollutant removal, with COD removal efficiency of 76% and 80% mg·L−1 for a 5- and 10-day HRT, respectively. The removal efficiency for TKN, NH3⁻N, and TP reached about 70% with a 5-day HRT, while a removal of 85% was obtained with a 10-day HRT. The wetland reached the maximum removal efficiency with a 10-day HRT and an inflow load of 400 mg·L−1 of organic matter. The results indicate that HRT positively affects removal efficiency of COD and TDS. On the other hand, the HRT was not the determining factor for TP removal. Treatment one, with an initial COD concentration of 400 mg·L−1, had the highest removal of the assessed pollutants, allowing for the use of water for irrigation according to Mexican regulatory standards (NOM-001). The water quality resulting from treatments two and three (T2 = 800 mg·L−1 of COD and T3 = 1200 mg·L−1 of COD) did not comply with minimal requirements for irrigation water.

Grado de sustentabilidad del desarrollo rural en productores de subsistencia, transicionales y empresariales, bajo un enfoque autopoiético / Degree of sustainability of rural development in subsistence, intermediate, and comercial farmers, under an autopoietic view point

Se comparó, desde un enfoque autopoiético, el grado de sustentabilidad del desarrollo rural en el distrito de Desarrollo Rural 006, La Antigua, Veracruz, México. El estudio se realizó en agosto 2007, mediante entrevistas a 30 productores de subsistencia, 30 transicionales y 20 empresarios, definidos heurísticamente. Los criterios específicos para la selección de productores fueron: Nivel de interacción con las instituciones, diversificación de sus agroecosistemas e innovación de prácticas de manejo. El análisis de eficiencia energética por tipo de productor, mostró diferencias estadísticas (P<0,01), donde el grupo transicional, que son productores de caña de azúcar, fue el más eficiente (4,62 ± 1,4); en comparación con el de subsistencia (2,01 ± 0,7) y empresarial (2,56 ± 0,8). Los empresarios mostraron mayor grado de cognición ecológica (3,01 ± 0,1), en relación (P<0,01) con el grupo de subsistencia (2,65 ± 0,1) y transicional (2,77 ± 0,1), siendo los empresarios los productores más jóvenes y con mayor nivel educativo. El mayor índice de bienestar económico racional correspondió a los empresarios (1,61 ± 0,1) en relación con los grupos subsistencia (1,46 ± 0,09) y transicional (1,52 ± 0,1) (P<0,01). El índice de manejo agrícola sustentable, resultó igual para los empresarios (1,46 ± 0,2) y para el grupo transicional (1,42 ± 0,1). El grado de sustentabilidad del desarrollo rural, fue diferente (P<0,01) y más alto en los transicionales (2,58 ± 0,3), en comparación con los de subsistencia (1,85 ± 0,1) y empresarios (2,16 ± 0,2), lo cual muestra el gran peso del indicador de eficiencia energética en el análisis. Se demostró que hubo procesos autopoiéticos en los tres grupos, solo que la reproducción socio cultural en ninguno de los sistemas está dirigida a lograr autopoiésis para la sustentabilidad. El grupo de subsistencia reprodujo procesos para poder subsistir, el transicional reprodujo su obediencia al esquema agroindustrial y los empresarios...

The degree of sustainable rural development in Rural Development District 006, La Antigua, Veracruz, Mexico was compared under an autopoietic view point. During August 2007, 30 subsistence farmers, 20 commercial farmers, and 30 farmers managing operations having both objectives (intermediate to the two extremes) were interviewed. Farmers were selected using three predetermined criteria: level of interaction with institutions, diversity of farm production, and innovation of management practices. The energy efficiency statistical analysis showed differences (P<0.01) among groups, the intermediate group, which are sugar cane growers, was the most efficient (4.62 ± 1.4) than subsistence (2.01 ± 0.7) and commercial operations growers (2.56 ± 0.8). On the other hand, commercial operations growers showed high ecological cognition (3.01 ± 0.1) compared to subsistence (2.65 ± 0.1) and intermediate (2.77 ± 0.1); commercial operations growers were youngest and with higher educational level compared to other groups. The well-being economic index was higher (P<0.01) in the commercial operations growers (1.61 ± 0.1) than in subsistence (1.46 ± 0.09) and intermediate (1.52 ± 0.1). The sustainable agricultural management index was similar between commercial operations (1.46 ± 0.2) and intermediate growers (1.42 ± 0.1). Degree of sustainable rural development, was different (P<0.01) among the three groups, with the intermediate group achieving the most (2.58 ± 0.3), followed by those from commercial operations (2.16 ± 0.2), and subsistence farming (1.85 ± 0.1); this showed the high influence of energy efficiency index. It was found autopoietic process in the three groups; however, none of the socio-cultural reproduction is intended for achieving autopoietic process for sustainability. The subsistence farming group repeat process to survive, the intermediate group reproduced the submission to agroindustry plan, and the commercial operations farmers followed...