No abstract

Industrial development has made new products available to people to make their lives easier. Items such as food, cleaning, personal care and health products, among others, are processed, sold and consumed daily by all age groups. These products include in their formulation inorganic and organic chemicals with the purpose of improving or increasing some of their properties, making them more attractive to the consumer. These substances are strictly controlled during production so that the final product may be safely consumed. In most cases, the constituents of commercial products end up in wastewater, where they are not controlled. These uncontrolled pollutants of differing chemical natures are known as “Emerging Contaminants” (ECs). Research worldwide has found ECs in various environmental matrices, especially water. To understand this problem, four fundamental aspects must be addressed: 1) the analytical methods for its determination; 2) the occurrence in environmental matrices; 3) the treatments for the removal of ECs in wastewater and drinking water plants; and 4) the risks to health and the environment. This document reviews these four aspects with regard to 14 ECs commonly found in the studies around the world and addresses the state of these ECs in trans-American waters.

Residence time distribution (RTD) curves play an essential role in the hydraulic characterization of reactors. Current approaches for obtaining RTD curves in laboratory-scale reactors are time-consuming and subject to large errors. Thus, automated systems to obtain RTD curves in laboratory-scale reactors are of great interest for reducing experimental errors due to human interaction, minimizing experimentation costs, and continuously obtaining experimental data. An automated system for obtaining RTD curves in laboratory-scale reactors was designed, built, and tested in this work. During the tests conducted in a cylindrical upflow anaerobic sludge blanket (UASB) reactor, the system worked properly using the stimulus–response pulse technique with sodium chloride as a tracer. Four main factors were found to affect the representativeness of the RTD curves: flow stabilization time, test water conductivity, temperature, and surface tension. A discussion on these factors and the corresponding solutions is presented. The RTD curves of the UASB reactor are left-skewed with a typical tank reactor’s flow shape with channeling and dead zones. A transitory flow behavior was evidenced in the reactor, which indicates the influence of internal turbulent flow structures. The system proposed herein is expected to help study the hydraulics of reactors using laboratory-scale models more efficiently.

The rapid urbanization of Cuenca, Ecuador, since about 1990 has led to efforts to build and operate decentralized domestic wastewater treatment systems in periurban and rural areas. The treatment efficiency of some of these is falling, however, and others are no longer working. ETAPA, the municipal institution in charge of water supply and sanitation, is evaluating them fully to identify common operating and maintenance difficulties, as well as deficiencies in design and/or construction. This paper presents an evaluation of the physical infrastructure and characterization of the treatment processes performed historically. The objective is to overcome the technical deficiencies and adopt a long-term, sustainable O&M plan.

Among emerging pollutants, endocrine disruptors such as estradiol are of most concern. Conventional water treatment technologies are not capable of removing this compound from water. This study aims to assess a method that combines physicochemical and biological strategies to eliminate estradiol even when there are other compounds present in the water matrix. Na-montmorillonite, Ca-montmorillonite and zeolite were used to remove estradiol in a medium with sulfamethoxazole, triclosan, and nicotine using a Plackett–Burman experimental design; each treatment was followed by biological filtration with Daphnia magna. Results showed between 40 to 92% estradiol adsorption in clays; no other compounds present in the mixture were adsorbed. The most significant factors for estradiol adsorption were the presence of nicotine and triclosan which favored the adsorption, the use of Ca-montmorillonite, Zeolite, and time did not favor the adsorption of estradiol. After the physicochemical treatment, Daphnia magna was able to remove between 0–93% of the remaining estradiol. The combination of adsorption and biological filtration in optimal conditions allowed the removal of 98% of the initial estradiol concentration.