A machine learning approach to analyse ozone concentration in metropolitan area of Lima, Peru.

The main objective of this study is to model the concentration of ozone in the winter season on air quality through machine learning algorithms, detecting its impact on population health. The study area involves four monitoring stations: Ate, San Borja, Santa Anita and Campo de Marte, all located in Metropolitan Lima during the years 2017, 2018 and 2019. Exploratory, correlational and predictive approaches are presented. The exploratory results showed that ATE is the station with the highest prevalence of ozone pollution. Likewise, in an hourly scale analysis, the pollution peaks were reported at 00:00 and 14:00. Finally, the machine learning models that showed the best predictive capacity for adjusting the ozone concentration were the linear regression and support vector machine.

Reverse Osmosis Concentrate: Physicochemical Characteristics, Environmental Impact, and Technologies.

This study's aim is to generate a complete profile of reverse osmosis concentrate (ROC), including physicochemical characteristics, environmental impact, and technologies for ROC treatment, alongside element recovery with potential valorization. A systematic literature review was used to compile and analyze scientific information about ROC, and systematic identification and evaluation of the data/evidence in the articles were conducted using the methodological principles of grounded data theory. The literature analysis revealed that two actions are imperative: (1) countries should impose strict regulations to avoid the contamination of receiving water bodies and (2) desalination plants should apply circular economies. Currently, synergizing conventional and emerging technologies is the most efficient method to mitigate the environmental impact of desalination processes. However, constructed wetlands are an emerging technology that promise to be a viable multi-benefit solution, as they can provide simultaneous treatment of nutrients, metals, and trace organic contaminants at a relatively low cost, and are socially accepted; therefore, they are a sustainable solution.

Predicting Accumulation of Intermediate Compounds in Nitrification and Autotrophic Denitrification Processes: A Chemical Approach.

Nitrification and sulfur-based autotrophic denitrification processes can be used to remove ammonia from wastewater in an economical way. However, under certain operational conditions, these processes accumulate intermediate compounds, such as elemental sulphur, nitrite, and nitrous oxide, that are noxious for the environment. In order to predict the generation of these compounds, an analysis based on the Gibbs free energy of the possible reactions and on the oxidative capacity of the bulk liquid was done on case study systems. Results indicate that the Gibbs free energy is not a useful parameter to predict the generation of intermediate products in nitrification and autotrophic denitrification processes. Nevertheless, we show that the specific productions of nitrous oxide during nitrification, and of elemental sulphur and nitrite during autotrophic denitrification, are well related to the oxidative capacity of the bulk liquid.

Effect of Free Ammonia, Free Nitrous Acid, and Alkalinity on the Partial Nitrification of Pretreated Pig Slurry, Using an Alternating Oxic/Anoxic SBR.

The effect of free ammonia (NH3 or FA), free nitrous acid (HNO2 or FNA), and total alkalinity (TA) on the performance of a partial nitrification (PN) sequencing batch reactor (SBR) treating anaerobically pretreated pig slurry was studied. The SBR was operated under alternating oxic/anoxic (O/A) conditions and was fed during anoxic phases. This strategy allowed using organic matter to partially remove nitrite (NO2-) and nitrate (NO3-) generated during oxic phases. The desired NH4+ to NO2- ratio of 1.3 g N/g N was obtained when an Ammonium Loading Rate (ALR) of 0.09 g NH4+-N/L·d was applied. The system was operated at a solid retention time (SRT) of 15-20 d and dissolved oxygen (DO) levels higher than 3 mg O2/L during the whole operational period. PN mainly occurred caused by the inhibitory effect of FNA on nitrite oxidizing bacteria (NOB). Once HNO2 concentration was negligible, NH4+ was fully oxidized to NO3- in spite of the presence of FA. The use of biomass acclimated to ammonium as inoculum avoided a possible effect of FA on NOB activity.

Effect of free ammonia nitrogen on the methanogenic activity of swine wastewater

Swine wastewater is characterized by high organic matter content, solids, nitrogen (expressed as total ammonia and protein) and heavy metals. This work determines the methanogenic toxicity effect of free ammonia contained in swine wastewater comparing raw swine wastewater (RW) and the liquid fraction of swine wastewater (TW). The values of IC50 (50 percent of inhibition) obtained for methanogenic bacteria ranged between 56 and 84 percent for RW, meanwhile IC50 for TW was ranged between 84 and 94 percent. Such inhibitory effects can be related to the free ammonia nitrogen concentration (> 40 mg NH3-N/L) contained in swine wastewater.

Determinación de la capacidad nitrificante de un sedimento marino proveniente de un centro de cultivo de salmones / Determination of the nitrifying capacity of marine sediments from a salmon farming centre

En el proceso productivo del salmón se eliminan residuos líquidos y sólidos. Si estos residuos no son tratados o retirados de los sitios de cultivos pueden ser tóxicos a los sistemas acuáticos, debido a su descomposición y producción de amonio (NH4+) y nitrito (NO2 4 +). En los ecosistemas acuáticos las bacterias nitrificantes son responsables de la oxidación de estos compuestos. El objetivo del presente trabajo es obtener cultivos de bacterias amonio oxidantes (BAO) y nitrito oxidantes (BNO) en sistemas de tipo batch y evaluar la capacidad de eliminación de nitrógeno, determinando las respectivas cinéticas. Como inóculo inicial se utilizó sedimentos de un centro de cultivo de salmones. Los resultados muestran la baja actividad nitrificante presente en los sedimentos, obteniéndose para BAO producciones de 197-206mg·l -1 N-NO -2, velocidades de consumo de O2 (VCO) con respecto del factor estequiométrico de 0,023mg·l -1·min-1 N y consumo neto de O2 (CNO) de 0,055mg·l-1·min-1 O2, mientras que para BNO, se obtuvieron producciones de 404-631mg·l-1 N-NO3-, VCO de 0,027mg·l-1·min-1 N y CNO de 0,0122mg·l?1·min?1 O2. Los resultados corroboran la incapacidad de las bacterias nitrificantes de oxidar la gran cantidad de compuestos nitrogenados generados por esta actividad acuícola.