Fenton's reagent and coagulation-flocculation as pretreatments of combined wastewater for reuse.

In Mexico City, drinking water is mainly produced from groundwater (70%). This practice has caused collateral problems such as Mexico City's soil sinking (5-30 cm/year). One of the most viable alternatives to palliate this problem is the treatment of wastewater for reuse in either irrigation or for groundwater artificial recharge. This paper presents the evaluation of two physicochemical pretreatment systems to treat the wastewater from the metropolitan area of the Mexican Valley that are conducted by two main sewage systems called Great Canal and Churubusco River. In this research two treatment processes were studied: 1) coagulation-flocculation and, 2) Fenton's reagent. For each one of these processes suggested, tests were performed with wastewater samples of the Great Canal and the Churubusco River mixed in a volume ratio of 1:1. In the case of the coagulation-flocculation process, additional experiments were performed to determine the optimal conditions by applying an experimental design technique. In this experimental design, six coagulant agents were considered (alum, ferric chloride, three coagulant reagents of polymeric kind with aluminium and a coagulant reagent of natural origin), and three flocculant agents (an anionic, a cationic, and a non ionic polymers). Concerning the application of the Fenton's reagent (Fe2+:H2O2), the experimental variables were the weight ratio of the ferrous iron and the hydrogen peroxide and the concentrations of these reagents. The pH value was controlled to be near to 4. For the best experimental conditions, the effluent of the Fenton's method showed similar physicochemical characteristics to the wastewater treated by coagulation-flocculation. Nevertheless, Fenton's reagent showed two very important advantages compared to the coagulation-flocculation process: a disinfecting effect and a lower production of residual sludges.

Ciliatological characterization of a biological reactor that eliminates nitrogen with intermitent aeration

El presente trabajo tiene por objetivo la determinación de los ciliados presentes en un reactor biológico con alternancia de aireación empleado para la eliminación de compuestos nitrogenados. El sistema de tratamiento usado fue de tipo lodos activados, con un volumen de trabajo de 30 litros, tiempo de residencia hidraúlico de 20 horas y tiempo de retención celular de 15 días. El reactor operó a 15 ºC y fue alimentado con agua residual doméstica, proporcionandole de manera alternada una hora de aireación por cada hora de no aireación, incorporándole de manera periódica acetato de sodio para favorecer la fase de desnitrificación. En términos globales el reactor logró una eliminación del 95 por ciento del material orgánico disuelto. Durante la fase de operación pseudoestable se presentaron 16 especies de ciliados (Phyllum Ciliophora), las cuales están distribuídas en 13 géneros; 12 familias; 7 órdenes; 6 subclases; 5 clases y 3 subphyla. De ellas 9 son libres nadadoras y 7 son sésiles. El subphyllum con mayor riqueza de especies fue el Cyrtophora, siendo la clase Oligohymenophorea la mejor representada y correspondiendo a la subclase Peritricha el mayor número de especies. Casi la totalidad de los ciliados encontrados has sido reportados como habitantes comunes en plantas de tratamiento de lodos activados convencionales con altas eficiencias depurativas y han sido catalogados dentro del sistema de ciliados saprobios, ubicándose principalmente en los niveles alfa y ß mesosaprobios. La presencia de esta comunidad de ciliados concuerda tanto con el nivel de eliminación de contaminantes carbonados, como nitrogenados. En consecuencia puede inferirse la factibilidad de evaluar la calidad operativa de un reactor aerobio/anóxico, a partir de la observación directa de la comunidad de ciliados prevaleciente

Ciliatological characterization of a biological reactor that eliminates nitrogen with intermitent aeration.

Ciliates present in an activated sludge biological reactor used for removal of nitrogen compounds with intermitent aeration were determined. The reactor had a working volume of 30 liters, a hydraulic residence time of 20 hours, and a cell retention time of 15 days. Operating temperature was 15 degrees C, and it was fed with domestic sewage. Aeration was given in pulses, one hour aeration and one hour without aeration, feeding sodium acetate to favour denitrification processes. Elimination efficiency was 95% of the dissolved organic matter. During the pseudostable operating phase, 16 species of ciliates (Phylum Ciliophora) were found. They were distributed as follows: 13 Genera; 12 Families; 7 Orders; 6 Subclasses; 5 Classes, and 3 Subphyla. From them, 9 are free swimmers and 7 are pedunculates. The Subphylum with higher diversity of species was the Ciliophora. The Oligohymenophorea Class was the best represented, corresponding to the Peritricha Subclass the highest number of species. Almost all the ciliates found have been reported as common inhabitants of activated sludge wastewater treatment plants with high removal efficiencies. They are catalogued as saprobe ciliates, within a and b masosaprobe levels. The presence of this ciliate community agrees with the carbon and nitrogen compounds removal efficiencies. Consequently, there exists the possibility of evaluating the operational efficiency of an aerobic/anoxic reactor using direct ciliates observations.

[Comparison of ciliate diversity in biodisc reactors which purify industrial wastewater]. / Comparación de la diversidad de ciliados en reactores de biodiscos que depuran aguas residuales industriales.

The comparative study of the ciliate populations present in rotating biological reactors (biodiscs reactors) of 20 l working volume, treating three different wastewaters is the aim of this project. Wastewaters chosen were those of a maize mill, of a sugarcane/ethyl alcohol plant, and of a recycled paper mill. Its dissolved organic contents, measured as soluble chemical oxygen demand (COD) and five-day biochemical oxygen demand (BOD5), were 2040 mg COD/l and 585 mg BOD5/l for maize mill effluents (nejayote), 2000 mg COD/l and 640 mg BOD5/l for sugarcane/ethanol effluents (vinasses), and 960 mg COD/l and 120 mg BOD5/l for whitewaters of the paper industry. Results obtained indicate that ciliate proliferate in all chambers of reactors treating these wastewaters. The ciliates were more abundant in vinasses, followed by nejayote, and then whitewaters. Among protozoa, ciliates were present as follows: 19 species in total. Three of them were common for the three systems. Free swimming ciliates were in higher proportion than pedunculated ones. Its diversity was higher for the whitewaters system, next for nejayote, and the lesser, for vinasses, corroborating the fact that less polluted waters have higher organisms' diversity.

[Isolation and selection of methylamines and dimethyl formamide degrading microorganisms]. / Aislamiento y selecci'on de microorganismos que degradan metilaminas y dimetilformamida.

From an activated sludge sample, microorganisms capable to degrade monomethylamine (MMA), dimethylamine (DMA), trimethylamine (TMA), and dimethylformamide (DMF) were isolated. These compounds are present in the wastewaters from a petrochemical plant. Microbial communities were cultivated, in aerobic conditions in a 2-liter bioreactor fed with the wastewater. Only four different kinds of microorganisms were obtained, but they could maintain their degradative capacity after several transfers. This microbial biomass was able to reduce 90% of the dissolved pollutants in a sample of industrial wastewater, mainly MMA, DMA, TMA, and DMF, measured as dissolved organic carbon, in approximately 5 days.