Paulina Vilela

Partial nitritation (PN) coupled with the anaerobic ammonium oxidation (Anammox) process has improved ammonium removal in wastewater treatment plants (WWTPs). The operation conditions of this process, i.e., the dissolved oxygen (DO) and the influent ammonium and nitrite concentrations, drive the process to an equilibrium to suppress nitrite-oxidizing bacteria and achieve a proper nitrite over ammonium (NO₂/NH₄) ratio. This study aimed to implement a set of control strategies in a WWTP model BSM2-SHAMX, combining PN in a single reactor system for high-activity ammonia removal over nitrite (SHARON) to an Anammox reactor, using proportional–integrative–derivative (PID) control and model predictive control (MPC) in a cascade. For correct coupling, the PN should maintain an output NO₂/NH₄ ratio between 1 and 1.3, suitable for the Anammox process. In the cascade controller feedback loop, the primary control loop controls the NO₂/NH₄ ratio through the DO concentration from the secondary control loop, which guarantees better effluent nitrogen removal. The performance of the plant was assessed by evaluating the control strategies with different influent carbon/nitrogen (C/N) loadings. The study results showed that the MPC controllers provided better results, with an improvement of 36% in the operational cost compared to the base case with a cost around 26,000 EUR/d, and better nitrogen removal surpassing 90% removal, 10% more than the base case.

In view of the continuous increment of industrial residues, the risk associated with chemical toxicity in the environment has piqued the interest of researchers in pursuit of an alternative methodology for mitigating the apparent toxicity of chemicals. Over the past decade, the applicability of toxicity models and the evaluation of the apparent toxicity of chemicals have been examined for achieving sustainability of the environment and improving water quality. The prediction of toxicant effects with reasonable accuracy in organisms of water bodies and other environmental compartments lies in the application of a chemical toxicity model with further risk assessment analysis. This review summarizes well-known and recent advances of modeling techniques to evaluate and monitor toxicity in the environment. Chemical toxicity models such as the individual-based concentration addition (CA), independent action (IA) and whole-mixture-based concentration addition-independent action (CAIA) are considered, as well as their environmental applications, specific case studies, and further research needs towards sustainability. The gap that needs to be overcome in toxicity studies for the environmental sustainability is noted based on the aspects of environmental chemistry and ecotoxicology, sufficient laboratory equipment, data availability and resources for relevant social parameters needed for investigation.

The income tax is one of the several sources of funding of all the countries, which includes the income of resources exploitation activities, production and/or services that people carry out. In Ecuador, the income tax collection is a choice made by the President by the Tributary Code, who proposes laws to the National Assembly to optimize its collection, being administered by the National Internal Income Services Office. In 2021, the President approved a new normative for the 2022 where the base for income tax was incremented. Hence, the income tax increased to the salary related to the employees’ job dependency. In this study, the authors seek to determine the increment needed to be paid as an income tax. The methodology followed in this study consisted of first organizing the data by objective to classify them by the required income sources considering relevance, completeness and timeliness. The metrics calculated for the increment in the income tax are a fundamental and innovative methodology that outlines the impact of the increment, significantly reducing the acquisitive power of the income compared to the previous year.