Víctor Manuel Luna-Pabello

Green microalga Scenedesmus acutus grown on municipal wastewater to couple nutrient removal with lipid accumulation for biodiesel production

The green microalga Scenedesmus acutus was cultivated in two different municipal wastewater discharges (pre- and post-treated), and was compared to a culture medium with basic nutrients (20% of N, P, K), in order to study the simultaneous potential of nutrient removal and lipid accumulation ability. The highest level of nutrient removal was found in the pretreated wastewater discharge (achieving a high removal of phosphorus [66%] and organic nitrogen [94%]). Likewise, better results on biomass productivity and lipid accumulation were found in cultures using pretreated wastewater compared to enriched medium, obtaining 79.9 mg/L, and 280 mg/L, respectively. Since the best results were found in pretreated wastewater, the biodiesel preparation was performed using said medium at small-scale. After cultivation, 249.4 mg/L of biodiesel were obtained. According to this analysis, S. acutus could be used for wastewater treatment producing biomass with a suitable content of lipids, convenient for biodiesel production.

Biomonitoring of wastewaters in treatment plants using ciliates

The aim of this project has been to study and compare the ciliate populations present in roptating biological reactors treating three different wastewaters. Wastewaters chosen were a maize mill (nejayote), a sugarcane/ethyl alcohol plant (vinasses) and a recycled paper mill (whitewaters). The initial dissolved organic contents, measured as soluble chemical oxygen demand (COD) and biochemical oxygen demand in five days (BOD5), were 2040±150 mg COD L−1 and 585±5 mg BOD5L−1 for nejayote; 2000±20 mg COD L−1 and 640±5 mg BOD5 L−1 for vinasses and 960±200 mg COD L−1 and 120±10 mg BOD5 L−1 for whitewaters. Results obtained indicate that ciliated protozoa proliferated in the different chambers of each rotating biological reactor (RBR). Saprobity indices, as a quantitative evaluation parameter, indicate that there are no universal species of ciliates associated with specific BOD5 concentrations. Therefore, the number of species of ciliates present in the effluent indicate qualitatively the efficiency of removal of pollution from the wastewaters during treatment in the rotating biological reactors.

Temperature effects on ciliates diversity and abundance in a rotating biological reactor

Experiments in a 20-litre, laboratory, rotating biological reactor were performed at 10, 20, and 30°C to depurate carbonaceous wastewaters coming from the food industry with an organic load of 2 g of Chemical Oxygen Demand (COD) per litre (0·6 g of Biochemical Oxygen Demand (BOD5) per litre). Twenty acrylic discs, 0·3 m diameter were arranged in 10 compartments, and rotated at 30 rpm. At a one-day residence time, when pseudo-steady-state conditions were reached, removal of organics was, at 10°C, 45 and 63% for COD and BOD5, respectively; at 20°C, 49 and 84%; and for 30°C, 87 and 96%. Microbial communities proliferating at these temperatures corroborated previous studies on the relationship between the degree of pollution and the type of microorganisms present in the different stages of the reactor.

ESTUDIO DE LOS PROTOZOARIOS CILIADOS PARA DETERMINAR LA CALIDAD DEPURATIVA DE SISTEMAS ROTATORIOS BIOLÓGICOS PARA TRATAMIENTO DE AGUAS RESIDUALES

Los metodos tradicionales de tratamiento biologico de aguas residuales involucran comunidades aerobias para la etapa secundaria de tratamiento. Para obtener el articulo completo pueden contactar al Editor de la Revista Ecosistemas y Recursos Agropecuarios en el siguiente correo electronico era@ujat.mx y se les enviara sin algun costo.

Constructed Wetlands for Reducing Pesticide Inputs into Surface Water and Groundwater

In this review, the current knowledge on the use of constructed wetlands (CWs) to reduce pesticide inputs into surface water and groundwater and their effectiveness when applied in practice are discussed. Field data show that plants accelerate pesticide dissipation from aquatic systems by increasing sedimentation, biofilm contact, and photolysis. One of the main mechanisms of pesticide removal in CWs is sorption onto plants, support media, and sediments; yet, CWs effectiveness still has to be demonstrated for weakly and moderately sorbing compounds. The hydraulic design (hydraulic retention time, HRT) and the use of adsorbing materials can be useful to increase the pesticides residence time and the contact between pesticides and biocatalysts. Pesticide fluxes can be reduced by 50–80% when increasing ten times the retention time. This, in turn, leads to CW lengths that are much longer than those for municipal wastewater treatment. CWs are a viable and economic alternative technology for the treatment of effluents contaminated with pesticides, compared to conventional treatment systems. Yet, there are some limitations of CWs, inter alia, they are not suitable for high concentrations of xenobiotics, and they should be carefully managed in order to avoid an over contamination by pesticides of the wetland site and associated negative effects (i.e., wetlands that require remediation).