The primary source of the discharge of phenols into the environment is industrial activity, such as the production of pharmaceuticals, plastics, and pesticides, being the majority discharged into surface water sources, reaching concentrations around 0.001 to 0.400 mg/L. These compounds are considered a priority contaminant due to their toxicity to aquatic life and effects on human health. The presence of phenols even at low concentrations generates flavour and odour in drinking water. Due to the molecular stability and solubility of phenols in water, their removal by conventional water treatment methods is inefficient. However, adsorption with granular activated carbon (GAC), after conventional filtration with sand and anthracite, is an efficient technique for the reduction of organic compounds such as phenols. This paper studied the effect of applying double filtration to the reduction of phenols present in the filtered water of a conventional drinking water treatment plant, using two types of GAC (vegetable and mineral) and three GAC:Sand configurations (100:00; 00:100; 50:50). The configurations with GAC showed an efficient reduction of turbidity, organic matter indicator variables (UV254 absorbance and total organic carbon) and phenols, the mineral GAC being the most efficient GAC.

<p><strong>Abstract.</strong> The water supply industry is faced with three phenomena of great importance: the aggressiveness, corrosion, and incrustation of water distribution systems (WDS), which are primarily due to the low alkalinity of water sources and the addition of chemicals used in water treatment processes, which require pH adjustments during the last stage of the treatment process before going into the WDS. This article presents the results of using Ca(OH)₂ and NaOH with doses between 2 and 20 mg L⁻¹ and NaHCO₃ and Na₂CO₃ between 10 and 250 mg L⁻¹ to adjust the pH of water treated from the Cauca River, which is located in Cali, Colombia, using stabilisation indices normally used in water treatment plants for pH monitoring processes and to better predict the behaviour of water in the WDS. The results indicate that for the case of the surface water source studied, which exhibits low alkalinity levels, the evaluated alkalising agents, with the exception of NaHCO₃, can create conditions that lead to the precipitation of a~protective calcium carbonate film. Because the pH values that guarantee an adequate pH adjustment are higher (8.7–9.0) than those specified by the Colombian water code and because other international rules indicate that these values do not compromise the health of consumers, it is advisable to review and adjust the code in this respect.</p>

The type of hazards and hazardous events in watersheds, depend on land uses around them. Atrazine is an organic pollutant widely applied as a pesticide and it is a potential chemical hazard present in water sources, which cause water pollution and negative effects on aquatic life and human health, due to its high solubility and persistence in soil. However, for developing countries, monitoring and quantification of atrazine can be complex and costly; thus, to contribute to establishing strategies for risk assessment in water supply watersheds, it was evaluated the potential use of an easy, rapid and low-cost technique such as ultraviolet (UV) absorbance to identify the presence of atrazine. It was conformed distilled and surface water samples doped with Atrazine, and there were correlated with the UV typical spectrum indicator of organic material presence (wavelength λ: 200 - 300 nm). The optimal λ range was 203 - 223 nm to identify this substance at levels possible to be found in surface sources, being UV223 more adequate than UV254, which is more used to identify the presence of natural organic matter, which shows that UV223 is a complementary tool to chemical risk assessment for atrazine in drinking water supply systems.

Palabras clavesAntracita, arena, configuración de medio filtrante, filtración, turbiedad. ResumenSe evaluó a escala piloto el efecto de la configuración del medio filtrante sobre el proceso de filtración del agua clarificada de la planta de potabilización Puerto Mallarino, Cali -Colombia. Se analizaron cuatro configuraciones, una con características similares a los filtros existentes y las restantes con diferente tamaño efectivo y espesor de antracita. Se analizó turbiedad, duración de carrera, producción de agua y pérdida de carga. La filtración fue más eficaz al reducir el tamaño efectivo e incrementar el espesor. La configuración que mostró un mejor desempeño incluso operando con turbiedades de agua clarificada mayores a 10,0 UTN, fue la del filtro con un espesor de 700 mm.

This study investigated the state of a service reservoir of a drinking water distribution network. Numerical simulation was applied to establish its flow pattern, mixing conditions, and free residual chlorine decay. The influence of the change in the water inlet configuration on these characteristics was evaluated. Four scenarios were established with different water level and flow rate as the differences between the first three scenarios. The fourth scenario was evaluated to assess the influence of the inlet configuration, momentum flow and water level on hydrodynamic conditions within the service reservoir. The distribution of four nozzles of 152.4 mm diameter was identified as a viable measure to preserve the water quality in this type of hydraulic structures. Keywords:Computational fluid dynamics, CFD, free residual chlorine, mixing time, momentum flow, service reservoir, tracer. RESUMENEn este estudio se evaluó mediante simulación numérica la influencia del cambio en la configuración de entrada de agua sobre el patrón de flujo, condiciones de mezcla y decaimiento del cloro residual libre en un tanque de compensación de una red de distribución de agua potable. Se establecieron cuatro escenarios, tres presentaron diferencias en el nivel de agua y velocidad de flujo y el cuarto escenario evaluó la influencia de la configuración de entrada, el flujo de momento y nivel del agua sobre las condiciones hidrodinámicas en el tanque de compensación. La distribución de cuatro boquillas de 152,4 mm de diámetro fue identificada como una medida viable para preservar la calidad del agua en este tipo de estructuras hidráulicas.Palabras clave: Dinámica de fluidos computacional, CFD, cloro residual libre, tiempo de mezcla, flujo de momento, tanque de compensación, trazador.